Method for producing mounting structure for an electronic component

Abstract
In a mounting structure including a first electrode and a second electrode electrically connected to each other via a conductive adhesive, the periphery of an adhesion portion between at least one of the electrodes and the conductive adhesive is covered with an electrical insulating layer, whereby the adhesion portion is reinforced from the periphery. The electrical insulating layer may be formed by dissolving a binder resin component of the conductive adhesive in a solvent. This increases the concentration of a conductive filler in the conductive adhesive, so that the conductivity of the adhesion portion is also enhanced.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to a solder-free mounting structure for an electronic component, in particular, a mounting structure for an electronic component using a conductive adhesive, and a method for producing the same.




2. Description of the Related Art




In recent years, due to increasing environmental awareness, there have been movements toward elimination of lead-containing solder used for mounting electronic components in the electronic industry.




Under such circumstances, a mounting technique using lead-free solder has been extensively developed, and partially put into practical use. However, the lead-free mounting technique has a number of problems, such as a large effect of an increase in mounting temperature on components with low heat-resistance and difficulty in realizing lead-free electrodes.




On the other hand, mounting using a conductive adhesive has been carried out in circumstances, particularly when restricted to small components such as chip components. More specifically, in addition to the advantage of using no lead, mounting using a conductive adhesive has the following advantages, so that it is expected as a potential technique in the future. First, the treatment temperature of a conductive adhesive is low (about 150° C.), compared with that of solder. Second, the specific gravity of a conductive adhesive is almost half that of solder, so that it is easier to render electronic equipment lightweight. Third, unlike solder, a conductive adhesive is not a metal material, so that metal fatigue does not occur, and resistance to repeated stress is outstanding.




Accordingly, by applying a mounting technique using a conductive adhesive to all the components, novel mounting can be expected, which satisfies environmental friendliness and high reliability.




However, a conductive adhesive has adhesion strength smaller than that of solder. Therefore, it is likely to be difficult to replace mounting using solder by mounting using a conductive adhesive. The reason why a conductive adhesive has smaller adhesion strength compared with solder is as follows. Mounting using solder utilizes a metallic bond with electrodes, whereas mounting using a conductive adhesive utilizes physical contact, a hydrogen bond, etc. with electrodes (which are relatively weak).




Conventionally, mounting using a conductive adhesive has been utilized for small components such as chip components. In this case, the mounted components are not likely to receive stress, so that the problem of small adhesion strength has not been raised. However, in particular, when packaged components, etc. (which are rapidly coming into widespread use in recent years) are mounted on printed-wiring substrates, small adhesion strength becomes a serious problem. For example, packaged components such as a Chip Size Package (CSP) and a Ball Grid Array (BGA) are more likely to receive stress compared with chip components. Therefore, there is a high possibility that poor connection occurs in mounting using a conductive adhesive. Stress applied to a mounting structure in which these packaged components are mounted on a printed-wiring substrate is roughly classified into two kinds: shearing stress and bending stress. The shearing stress is likely to be applied to an adhesion portion due to the difference in thermal expansion coefficient between a component and a printed-wiring substrate in the presence of thermal hysteresis. The bending stress is applied to a substrate due to an external force and the like.




Thus, in the case where mounting using a conductive adhesive is applied to all the electronic components, improvement of the adhesion strength becomes important.




In order to improve the adhesion strength of a conductive adhesive, a number of examples of improved adhesive materials have been reported as in JP 59-172571 A. However, it has been difficult to achieve the adhesion strength comparable to that of solder by simply improving adhesive materials.




Hereinafter, an example of a conventional mounting structure obtained by a mounting technique using a conductive adhesive will be described with reference to

FIGS. 20 and 21

.




Referring to

FIG. 20

, in the conventional mounting structure, an electrode


93


formed on a substrate


91


is electrically connected to an electrode


94


formed on a substrate


92


via a conductive adhesive


95


. Such a mounting structure is obtained by coating the electrode


94


with the conductive adhesive


95


, placing the substrate


91


in such a manner that the electrode


93


faces the surface of the conductive adhesive


95


, and curing the conductive adhesive


95


by heating.




In the above-mentioned mounting structure, the conductive adhesive


95


is cured while substantially keeping its shape in coating. As a result, as shown in

FIG. 21

, binder resin


95




a


is present at the adhesion interface between the conductive adhesive


95


and the electrode


94


in a ratio substantially reflecting its mixture ratio in the conductive adhesive


95


. This also applies to the adhesion interface between the conductive adhesive


95


and the electrode


93


. Reference numeral


95




b


in

FIG. 21

denotes a metal filler contained in the conductive adhesive


95


.




However, the above-mentioned mounting using a conductive adhesive has been hindered from being put into practical use due to the following problems.




First, the adhesion strength in mounting using an adhesive conductive is smaller, compared with that in mounting using solder. One of the reasons for this is that, unlike mounting using solder, a fillet cannot be formed around adhesion interfaces by mounting using an adhesive conductive.




For example, in the conventional mounting structure shown in

FIGS. 20 and 21

, no binder resin


95




a


adheres to the side surfaces of the electrodes


93


and


94


and the peripheral portions thereof on the substrates


91


and


92


. Accordingly, compared with molding using solder that enables a fillet to be formed around adhesion interfaces, adhesion strength is smaller in mounting using a conductive adhesive. Therefore, the adhesion portion obtained by mounting using a conductive adhesive is likely to be broken by an external force or heat stress, resulting in low adhesion reliability.




Second, in mounting using a conductive adhesive, electrodes are electrically connected to each other by way of contact with a filler in a conductive adhesive. Therefore, the connection resistance is greatly influenced by the state of contact.




For example, in the conventional mounting structure shown in

FIG. 21

, the binder resin


95




a


in the conductive adhesive


95


also is present at the adhesion interfaces between the conductive adhesive


95


and the electrodes


93


and


94


in a ratio substantially reflecting its mixture ratio in the conductive adhesive


95


. Therefore, a large amount of the binder resin


95




a


at the adhesion interfaces may adversely affect the electrical connection, which renders the connection resistance high or unstable.




Thus, the conventional mounting using a conductive adhesive has been difficult to be put into practical use as an alternative to mounting using solder, due to insufficient reliability at the adhesion interfaces.




SUMMARY OF THE INVENTION




Therefore, with the foregoing in mind, it is an object of the present invention to provide a mounting structure in which adhesion strength and adhesion reliability are improved without using solder.




It is another object of the present invention to provide a mounting structure with high adhesion strength and low and stable connection resistance by improving adhesion reliability between a conductive adhesive and a metal electrode in solder-free molding using a conductive adhesive.




In order to achieve the above-mentioned objects, the first mounting structure of the present invention includes a first electrode and a second electrode electrically connected to each other via a conductive adhesive, wherein a periphery of an adhesion portion between at least one of the electrodes and the conductive adhesive is covered with an electrical insulating layer.




The second mounting structure of the present invention includes a conductive adhesive and a metal electrode electrically connected to each other, wherein the conductive adhesive contains a conductive filler and binder resin, a content of the conductive filler in the conductive adhesive is high in an adhesion portion between the conductive adhesive and the metal electrode, and a part of the binder resin flows and adheres to a periphery of the metal electrode.




According to the present invention, a method is provided for producing a mounting structure for an electronic component including a conductive adhesive and metal electrodes electrically connected to each other. The method includes: coating the metal electrodes with a solvent that dissolves binder resin in the conductive adhesive; coating the solvent with the conductive adhesive; and curing the conductive adhesive by heating so as to connect the metal electrodes to the conductive adhesive.




The first mounting structure of the present invention allows adhesion strength (which used to be small in conventional mounting using a conductive adhesive) to be remarkably improved by covering an adhesion portion with an electrical insulating layer, and hence, contributes to achievement of a solder-free mounting technique using a conductive adhesive.




The second mounting structure of the present invention allows adhesion strength between a conductive material contained in a conductive adhesive and a metal electrode to be enhanced, and low and stable connection resistance to be obtained. Furthermore, since binder resin adheres to the side surface of the metal electrode to form a fillet, a mounting structure with high adhesion strength can be obtained.




Furthermore, according to the production method of the present invention, in the step of curing a conductive adhesive by heating, binder resin contained in a portion of the conductive adhesive that is in contact with a solvent layer dissolves in the solvent layer and flows along an adhesion interface due to an interface effect. Consequently, the content of the binder resin contained in the conductive adhesive becomes low at the adhesion interface between the metal electrode and the conductive adhesive. Therefore, the adhesion strength between the conductive material contained in the conductive adhesive and the metal electrode is enhanced, whereby a mounting structure with lower and more stable connection resistance can be obtained, compared with a mounting structure obtained by a conventional method in which a metal electrode is directly connected to a conductive adhesive without using a solvent. Furthermore, the binder resin that is extruded along the adhesion interface adheres to the side surface of the metal electrode to form a fillet, so that adhesion strength can be remarkably enhanced, compared with the mounting structure obtained by the conventional method.




These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a sectional side view of a mounting structure of a first embodiment according to the present invention.





FIG. 2

is an enlarged view of an adhesion portion of the mounting structure of the first embodiment according to the present invention.





FIG. 3

is a sectional side view of a mounting structure of a second embodiment according to the present invention.





FIG. 4

is an enlarged view showing an adhesion portion of the mounting structure of the second embodiment according to the present invention.





FIG. 5

is a sectional side view of a mounting structure used in Examples 1 to 8 according to the present invention.





FIG. 6

is an enlarged view showing an adhesion portion of the mounting structure used in Examples 1 to 8 according to the present invention.





FIG. 7

is a sectional side view of a conventional mounting structure used in Comparative Example 1.





FIG. 8

is a sectional side view of a mounting structure used in Example 9 according to the present invention.





FIG. 9

is a sectional side view showing an example of a mounting structure of a third embodiment according to the present invention.





FIG. 10

is an enlarged view showing the vicinity of an adhesion interface between a metal electrode and a conductive adhesive in the mounting structure shown in FIG.


9


.





FIGS. 11A through 11E

are cross-sectional views, each showing a main production step of the mounting structure shown in FIG.


9


.





FIG. 12

is a sectional side view showing an example of a mounting structure of Example 10 according to the present invention.





FIG. 13

is an enlarged view showing the vicinity of an adhesion interface between a metal electrode and a conductive adhesive in the mounting structure shown in FIG.


12


.





FIG. 14

is a sectional side view showing a conventional mounting structure as a comparative example of the mounting structure shown in FIG.


12


.





FIG. 15

is an enlarged view showing the vicinity of an adhesion interface between a metal electrode and a conductive adhesive in the conventional mounting structure shown in FIG.


14


.





FIG. 16

is a sectional side view showing an example of a mounting structure of Example


13


according to the present invention.





FIG. 17

is an enlarged view showing the vicinity of an adhesion interface between a metal electrode and a conductive adhesive in the mounting structure shown in FIG.


16


.





FIG. 18

is a sectional side view showing a conventional mounting structure as a comparative example of the mounting structure shown in FIG.


16


.





FIG. 19

is an enlarged view showing the vicinity of an adhesion interface between a metal electrode and a conductive adhesive in the conventional mounting structure shown in FIG.


18


.





FIG. 20

is a sectional side view showing an example of a conventional mounting structure.





FIG. 21

is an enlarged view showing the vicinity of an adhesion interface between a metal electrode and a conductive adhesive in the conventional mounting structure shown in FIG.


20


.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




In the first mounting structure according to the present invention, it is preferable that an electrical insulating layer is formed of at least one material selected from the group consisting of ceramic and resin.




In the above-mentioned mounting structure, it is preferable that the electrical insulating layer is formed by binder resin from the conductive adhesive.




In the above-mentioned mounting structure, it is preferable that the first electrode is integrated with an electronic component and the electrical insulating layer also adheres to the electronic component.




In the above-mentioned mounting structure, it is preferable that the second electrode is integrated with a substrate, and the electrical insulating layer also adheres to the substrate.




In the above-mentioned mounting structure, it is preferable that there is a space between the electrical insulating layer covering the periphery of the adhesion portion between the first electrode and the conductive adhesive and the electrical insulating layer covering the periphery of an adhesion portion between the second electrode and the conductive adhesive, the conductive adhesive extends to the space, and the conductive adhesive in its extending portion adheres to the electrical insulating layer. It is preferable that the extending portion has a length of 50 μm to 300 μm.




In the above-mentioned mounting structure, it is preferable that a maximum height H of the conductive adhesive in a layered direction and a height H1 of the conductive adhesive in a layered direction in an adhesion portion between the conductive adhesive and the electrical insulating layer satisfy the relationship 0.01 H<H1<H/2 so as to obtain excellent adhesion reliability.




In the above-mentioned mounting structure, it is preferable that a maximum diameter D of the conductive adhesive in a plane direction and a diameter D1 of the conductive adhesive in a plane direction in the adhesion portion between the conductive adhesive and the electrode satisfy the relationship 1.01 D1<D<P/2 (where P denotes a connection pitch) so as to obtain excellent adhesion reliability.




In the above-mentioned mounting structure, it is preferable that the height of the electrical insulating layer seen in the cross-sectional direction thereof is in a range of 1 μm to 100 μm.




In the above-mentioned mounting structure, it is preferable that the thickness of the electrical insulating layer seen in the cross-sectional direction thereof is in a range of 1 μm to 100 μm.




In the above-mentioned mounting structure, it is preferable that the electrical insulating layer is formed continuously between adjacent electrodes.




In the second mounting structure according to the present invention, the content of a conductive filler in binder resin that has flowed and adhered to the periphery of the metal electrode is preferably lower than that in the adhesion portion between the conductive adhesive and the metal electrode. If the amount of the binder resin component is large at the periphery of the metal electrode, adhesion strength is enhanced, which results in an increased reinforcing effect.




In the above-mentioned mounting structure, the binder resin adhering to the periphery of the metal electrode is the one that dissolves in a solvent from the conductive adhesive. Accordingly, an electrically connected portion of the conductive adhesive is integrally formed with reinforcing resin that flows to the periphery of the connected portion, so that a reinforcing effect becomes high.




In the above-mentioned mounting structure, the binder resin is preferably thermosetting resin. This is because thermosetting resin realizes outstanding integration by adhesion and satisfactory heat resistance.




In the above-mentioned mounting structure, the cross-section of the binder resin that has flowed and adhered to the periphery of the metal electrode preferably has a shape spreading from the conductive adhesive to the metal electrode. This is because the reinforcing effect on the electrically connected portion of the conductive adhesive becomes high.




The above-mentioned solvent is preferably at least one selected from the group consisting of monovalent alcohols, ketones, esters, glycols, and glycol ethers.




Furthermore, the above-mentioned solvent preferably contains a component having a metal-adsorbing functional group or a functional group that chemically reacts with metal.




Because of this, when a solvent is formed in a layer shape on an electrode, the thickness of a solvent layer adhering to the electrode can be rendered large. Therefore, in the step of curing a conductive adhesive by heating, the amount of binder resin that dissolves in a solvent and is extruded from the adhesion interface is increased. As a result, the content of the binder resin at the adhesion interface is further decreased; and contact between the conductive adhesive and the electrode is improved, and more stable and lower connection resistance can be obtained. Furthermore, the amount of binder resin that is extruded to the periphery of the conductive adhesive along the adhesion interface and adheres to the electrode cross-section is increased, so that adhesion strength is further increased. The above-mentioned component having a metal-adsorbing functional group or a functional group that chemically reacts with metal preferably has at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a vinyl group, an epoxy group, an amino group, a methacryl group, a mercapto group, an iminodiacetic acid group, an iminodipropionic acid group, an ethylenediamine acetic acid group, and an aminocarboxyl group.




In the above-mentioned production method, the solvent preferably contains a component having a reducing property.




Because of this, an oxide film on an electrode is reduced at the adhesion interface between the metal electrode and the conductive adhesive. Therefore, lower connection resistance is obtained while adhesion strength is further increased.




The component having a reducing property is preferably at least one selected from the group consisting of reducing sugars, reducing vitamins, hydroxybenzenes, amines, formic acid, polyhydric alcohols, glycol ethers, hydrazines, Rochelle salt, acetoaldehyde, glyoxal, and hypophosphorous acid.




In the above-mentioned production method, it is preferable that coating of the solvent is conducted by spray coating.




In the above-mentioned production method, a coating amount of the solvent is set in a range of 0.01 mg to 1000 mg/cm


2


, preferably 0.1 to 100/cm


2


, and more preferably 1 to 20 mg/cm


2


so as to form a solvent layer.




In the above-mentioned production method, the mounting structure further includes a second electrode, and prior to curing the conductive adhesive, the second electrode is coated with a solvent that dissolves binder resin in a conductive adhesive, and a surface of the solvent on the second electrode is placed onto the conductive adhesive.




Embodiment 1




The present invention will be described by way of illustrative embodiments with reference to the drawings.





FIG. 1

shows the first mounting structure of the present invention. An electrode


2


on an electronic component


1


such as a CSP and a BGA is electrically connected to an electrode


6


on a substrate


5


via a conductive adhesive


4


. Each periphery of adhesion portions between the electrode


2


and the conductive adhesive


4


and the electrode


6


and the conductive adhesive


4


is covered with an electrical insulating layer


3


(made of ceramic or resin).




Because of the above, the first mounting structure has resistance to shearing stress and improved adhesion reliability, compared with a conventional mounting structure. The reason for this will be described with reference to

FIG. 2

showing an enlarged adhesion portion between the electronic component and the conductive adhesive. When shearing stress is applied to the adhesion portion in the mounting structure, the shearing stress is almost absorbed by a contact portion


7


between the electrical insulating layer


3


and the conductive adhesive


4


, whereby stress applied to an adhesion interface


8


between the conductive adhesive and the electrode becomes smaller than that in the conventional mounting structure.




Embodiment 2





FIG. 3

shows a second mounting structure of the present invention. The second mounting structure is identical with the first mounting structure except that a conductive adhesive


12


adheres to the surface of an electrical insulating layer


11


as well as the surfaces of an electrode


10


on an electronic component


9


and an electrode


14


on a substrate


13


. Accordingly, the second mounting structure is more resistant to bending stress and has further improved adhesion reliability, compared with the first mounting structure. The reason for this will be described with reference to

FIG. 4

showing an enlarged adhesion portion between the electronic component and the conductive adhesive. When bending stress is applied to the adhesion portion of the second mounting structure, the bending stress is almost absorbed by a contact portion


15


between the conductive adhesive


12


and the surface of the electrical insulating layer


11


, whereby stress applied to an adhesion interface


16


between the conductive adhesive


12


and the electrode


10


becomes smaller than that of the first mounting structure.




In the first or second mounting structure of the present invention, it is preferable that a maximum height H of the conductive adhesive in a layered direction and a height H1 of the conductive adhesive in a layered direction in an adhesion portion between the conductive adhesive and the electrical insulating layer satisfy the relationship 0.01 H<H1<H/2, because adhesion reliability becomes most excellent in this case.




When H1 is equal to or smaller than 0.01 H, the contact area between the layered surface of the electrical insulating layer and the conductive adhesive is too small to absorb shearing stress satisfactorily, so that adhesion reliability is slightly decreased.




Furthermore, in the first or second mounting structure of the present invention, it is preferable that a maximum diameter D of the conductive adhesive in a plane direction and a diameter D1 of the conductive adhesive in a plane direction in the adhesion portion between the conductive adhesive and the electrode satisfy the relationship 1.01 D1<D<P/2 (where P denotes a connection pitch), because adhesion reliability becomes most excellent in this case.




When D is equal to or smaller than 1.01 D1, the contact area between the flat surface of the electrical insulating layer and the conductive adhesive is too small to absorb bending stress satisfactorily, so that adhesion reliability is slightly decreased.




Embodiment 3




Referring to

FIG. 9

, in the mounting structure of Embodiment 3, metal electrodes


43


and


44


respectively formed on substrates


41


and


42


are electrically connected to each other via a conductive adhesive


45


.





FIG. 10

shows an enlarged vicinity of an adhesion interface between the metal electrode


44


and the conductive adhesive


45


in the mounting structure. As shown in

FIG. 10

, in the conductive adhesive


45


, a metal filler


45




b


(conductive material) is kneaded into binder resin


45




a


. The binder resin


45




a


flowing from the conductive adhesive


45


adheres to a portion formed of a side part


44




a


of the metal electrode


44


and a peripheral part


42




a


of the metal electrode


44


on the substrate


42


. Accordingly, a fillet


46


is formed. The fillet


46


is also provided at a portion formed of a side part of the metal electrode


43


and a peripheral part of the metal electrode


43


on the substrate


41


. The content of the binder resin


45




a


in the fillet


46


is high.




A production process of the mounting structure is as follows. First, as shown in

FIG. 11A

, metal electrodes


43


and


44


are formed on substrates


41


and


42


, respectively. Then, solvent layers


47


and


48


are formed on the metal electrodes


43


and


44


, respectively, as shown in FIG.


11


B. Then, as shown in

FIG. 11C

, the surface of the solvent layer


48


formed on the metal electrode


44


is coated with a conductive adhesive


45


. Thereafter, as shown in

FIG. 11D

, the substrate


41


is placed on the substrate


42


in such a manner that the metal electrode


47


faces the conductive adhesive


45


. Then, the conductive adhesive


45


is cured by heating.




In heating, the binder resin


45




a


contained in portions of the conductive adhesive


45


that are in contact with the solvent layers


47


and


48


dissolves in the solvent layers


47


and


48


. The dissolved binder resin


45




a


flows along the adhesion interfaces together with the solvent of the solvent layers


47


and


48


due to an interface effect and is extruded to the peripheries of the adhesion portions between the conductive adhesive


45


and the metal electrodes


43


and


44


, thereby forming a fillet


46


as shown in FIG.


10


.




The solvent of the solvent layers


47


and


48


is extruded together with the binder resin


45




a


and evaporates during curing by heating. Therefore, as shown in

FIG. 11E

, the solvent layers


47


and


48


do not remain in the completed mounting structure.




In the mounting structure, due to the fillet


46


, adhesion strength is remarkably improved, compared with the conventional mounting structure without a fillet as shown in FIG.


20


. Furthermore, as shown in

FIG. 10

, the content of the binder resin


45




a


in the conductive adhesive


45


is lowest on the interfaces between the conductive adhesive


45


and the metal electrode


43


and the conductive adhesive


45


and the metal electrode


44


.




Accordingly, compared with the mounting structure obtained by a conventional method in which a metal electrode is directly connected to a conductive adhesive without forming a solvent layer, contact between the metal filler in the conductive adhesive and the metal electrode is improved, and connection resistance becomes low and stable. The solvent extruded together with the binder resin


45




a


evaporates by heat during curing, so that it will not adversely affect adhesion reliability.




Examples of the metal filler


45




b


in the conductive adhesive


45


include silver powder, nickel powder, and copper powder. As the binder resin


45




a


, those which mainly contain epoxy resin or the like can be used.




The solvent as used herein refers to a general organic solvent mainly used for removing oils and fats. Examples of the solvent include monovalent alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, etc.), ketones (acetone, methyl ethyl ketone, etc.), esters (acetic acid n-butyl, etc.), glycols (ethylene glycol, diethylene glycol, propylene glycol, etc.), and glycol ethers (ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, etc.).




Embodiment 4




The mounting structure of Embodiment 4 is identical with that of Embodiment 3 illustrated with reference to

FIGS. 9

,


10


, and


11


A to


11


E, except that a solvent to be provided at the interface between a metal electrode and a conductive adhesive in the course of production contains a component having a metal-adsorbing functional group or a functional group that chemically reacts with metal. Accordingly, the present embodiment also will be described with reference to

FIGS. 9

,


10


, and


11


A to


11


E used in Embodiment 3.




In the mounting structure of Embodiment 4, the solvent layers


47


and


48


shown in FIG.


11


B and the like are formed by using a solvent containing a component having a metal-adsorbing functional group or a functional group that chemically reacts with metal. Because of this, the amount of the solvent that adheres to the metal electrodes


43


and


44


is increased, whereby the thickness of the solvent layers


47


and


48


can be rendered larger than that in Embodiment 3.




Accordingly, the amount of the binder resin


45




a


that is extruded to the periphery of the adhesion portion together with the solvent during heating becomes larger, compared with the mounting structure of Embodiment 3. Consequently, the content of the binder resin


45




a


at the adhesion interfaces between the metal electrode


43


and the conductive adhesive


45


and the metal electrode


44


and the conductive adhesive


45


is further decreased, whereby contact between the metal filler


45




b


and the metal electrodes


43


and


44


is further improved. As a result, more stable and lower connection resistance can be obtained, compared with the mounting structure in Embodiment 3.




Furthermore, the amount of the binder resin


45




a


that is extruded to the periphery of the adhesion interface to form the fillet


46


is increased. Therefore, compared with the mounting structure of Embodiment 2, adhesion strength between the conductive adhesive


45


and the metal electrodes


43


and


44


is improved.




As the metal-adsorbing functional group or functional group that chemically reacts with metal, at least one selected from the group consisting of a hydroxyl group, a carboxyl group, a vinyl group, an epoxy group, an amino group, a methacryl group, a mercapto group, an iminodiacetic acid group, an iminodipropionic acid group, an ethylenediamine acetic group, and an aminocarboxyl group can be used.




Embodiment 5




The mounting structure of Embodiment 5 is identical with that illustrated in Embodiments 3 and 4 with reference to

FIGS. 9

,


10


, and


11


A to


11


E, except that a solvent to be provided at the adhesion interface between a metal electrode and a conductive adhesive in the course of production contains a component having a reducing property. Accordingly, the present embodiment also will be described with reference to

FIGS. 9

,


10


, and


11


A to


11


E.




In the mounting structure of Embodiment 5, the solvent layers


47


and


48


as shown in FIG.


11


B and the like are formed by using a solvent containing a reducing property. Because of this, an oxide film present on the electrodes


43


and


44


is reduced, so that connection resistance lower than that in Embodiment 3 or 4 is obtained, and adhesion strength is increased. The oxide film as used herein refers to, for example, a natural oxide film to be formed on the electrodes


43


and


44


when they are made of copper, etc., a natural oxide film that is further grown by heat during curing, and the like.




Examples of the component having a reducing property include at least one selected from the group consisting of reducing sugars, reducing vitamins, hydroxybenzenes, amines, formic acid, polyhydric alcohols, glycol ethers, hydrazines, Rochelle salt, acetoaldehyde, glyoxal, and hypophosphorous acid.




EXAMPLES




Hereinafter, the present invention will be described more specifically by way of illustrative examples.




(Sample)




(1) Conductive adhesive: “NH-010A” (Trade name) produced by Nippon Handa Co., Ltd. “NH-010A” is made of a mixed composition containing a silver filler and epoxy resin.




(2) Mounting structure





FIG. 5

shows a basic structure of a mounting structure used in the tests described later.

FIG. 6

is an enlarged view for illustrating the dimensions of an adhesion portion thereof. Land electrodes


18


on a ceramic SCP


17


(10×10 mm) are electrically connected to land electrodes


22


on a mother substrate


21


(FR-4 (standard of glass epoxy substrate)) with a thickness of 0.8 mm via a conductive adhesive


20


. Each periphery of adhesion portions between the land electrodes


18


and the conductive adhesive


20


is covered with a ceramic layer


19


, and each periphery of adhesion portions between the land electrodes


22


and the conductive adhesive


20


is covered with a solder resist layer


23


(produced by Taiyo Yuden Co., Ltd.).




The details of the land electrode will be described below.




Land number: 10×10 (area array arrangement)




Land diameter: 0.5 mm




Land pitch: 1.0 mm




Land metal: Ni/Au-plated




In each example, a mounting structure with the above-mentioned basic constitution was evaluated under the condition that a maximum diameter D of the conductive adhesive in a plane direction and a maximum height H thereof in a layered direction are prescribed to be constant while varying either of the following:




Diameter of the conductive adhesive in the adhesion portion between the electrode and the conductive adhesive (D1: CSP side, D2: mother substrate side)




Height of the conductive adhesive in the adhesion portion between the electrical insulating layer and the conductive adhesive in a layered direction (H1: CSP side, H2: mother substrate side)




(Evaluation Method)




Test 1: Evaluation of Resistance to Shearing Stress




Shearing stress was applied to the adhesion portion by pressing the side face of the ceramic CSP in a direction orthogonal to the layered direction, and the force was measured when connection resistance increased by twice or more the initial value.




Test 2: Evaluation of Resistance to Bending Stress




Bending stress was applied to the adhesion portion by pressing the reverse face of the ceramic CSP from the reverse face of the mother substrate in the layered direction, and the force was measured when connection resistance increased by twice or more the initial value.




The connection resistance was obtained by measuring series resistance of the adhesion portions connected to each other by using a daisy-chain.




Table 1 shows the results.















TABLE 1













Dimension (μm)




Evaluation
















Common





Mother sub-




results (kgf)

















portion




CSP side




strate side




Test




Test




















D




H




D1




H1




D2




H2




1




2























Example 1




500




100




500




10




500




0




15.5




2.5







500




100




500




1.2




500




0




15.4




2.4






Example 2




500




100




500




0




500




10




15.3




2.7







500




100




500




0




500




1.2




15.4




2.7






Example 3




500




100




500




10




500




10




33.4




2.6







500




100




500




1.2




500




1.2




33.3




2.5






Example 4




500




100




300




10




500




10




15.5




8.6







500




100




495




10




500




10




15.4




8.6






Example 5




500




100




500




10




300




10




15.4




8.7







500




100




500




10




495




10




15.5




8.6






Example 6




500




100




300




10




300




10




33.6




17.6







500




100




495




10




495




10




33.3




17.7






Example 7




500




100




500




0.8




500




0.8




10.9




2.5






Example 8




500




100




498




10




498




10




33.5




7.5






Example 9




500




100




300




10




300




10




33.5




17.5






Comparative




500




100




500




0




500




0




4.9




2.5






Example 1














Hereinafter, the above results will be described in detail.




Example 1




Using a conventional mounting structure (Comparative Example 1), the periphery of the adhesion portion between the conductive adhesive and the electrode on the CSP side was covered with an electrical insulating layer and H1 was set so as to satisfy H1>0.01 H (where H=100, H1=10 or 1.2). As a result, resistance to shearing force was improved (Test 1) compared with Comparative Example 1.




Example 2




Using the conventional mounting structure (Comparative Example 1), the periphery of the adhesion portion between the conductive adhesive and the electrode on the mother substrate side was covered with an electrical insulating layer and H2 was set so as to satisfy H2>0.01 H (where H=100 and H2=10 or 1.2). As a result, resistance to shearing force was improved compared with Comparative Example 1.




Example 3




Using the conventional mounting structure (Comparative Example 1), the peripheries of the adhesion portions between the conductive adhesive and the electrodes on both the CSP side and the mother substrate side were covered with an electrical insulating layer, and H1 and H2 were set so as to satisfy H1>0.01 H and H2>0.01 H (where H=100, H1=10, H2=10; or H=100, H1=1.2, H=1.2). As a result, resistance to shearing stress was improved compared with Examples 1 and 2.




Example 4




Using the mounting structure of Example 1, the diameters of the electrical insulating layer in a plane direction on the CSP side was prescribed to be larger than that in Example 1, and D1 was set so as to satisfy D>1.01 D1 (where D=500, D1=300 or 495). As a result, resistance to bending stress (Test 2) was improved compared with Example 1.




Example 5




Using the mounting structure of Example 2, the diameter of the electrical insulating layer in a plane direction on the mother substrate side was prescribed to be larger than that in Example 1, and D2 was set so as to satisfy D>1.01 D2 (where D=500, D2=300 or 495). As a result, resistance to bending stress was improved compared with Example 2.




Example 6




Using the mounting structure of Example 3, the diameter of the electrical insulating layer in a plane direction on both the CSP side and the mother substrate side was prescribed to be larger than that in Example 3, and D1 and D2 were set so as to satisfy D>1.01 D1 and D>1.01 D2 (where D=500, D1=300, D2=300; or D=500, D1=495, D2=495). As a result, resistance to bending stress was improved compared with Example 3.




Example 7




Using the mounting structure of Example 3, when H1 and H2 were set so as to satisfy H1<0.01 H and H2<0.01 H (where H=100, H1=H2=0.8), the resistance to shearing stress was degraded compared with Example 3; however, it was more excellent than that of Comparative Example 1.




Example 8




Using the mounting structure of Example 6, when D1 and D2 were set so as to satisfy D<1.01 D1 and D<1.01 D2 (where D=500, D1=D2=498), the resistance to bending stress was degraded compared with Example 6; however, it was more excellent than that of Comparative Example 1.




Comparative Example 1





FIG. 7

shows a conventional mounting structure. In

FIG. 7

, electrodes


25


on a ceramic CSP


24


are connected to electrodes


28


on a mother substrate


27


via a conductive adhesive


26


. There is no electrical insulating layer around the peripheries of adhesion portions between the conductive adhesive


26


and the electrodes


25


and


28


, so that resistance to shearing stress and resistance to bearing stress are unsatisfactory, compared with Examples 1 to 8.




As described in Examples 1 to 8, the mounting structure of the present invention has improved resistance to stress (i.e., adhesion reliability), compared with the conventional mounting structure in Comparative Example 1. In particular, in Example 6, the peripheries of adhesion portions between the conductive adhesive and the electrodes are covered with an electrical insulating layer on both the CSP side and the mother substrate side, the conductive adhesive is allowed to adhere to the flat surface of the electrical insulating layer as well as the electrodes, and the dimension is set under predetermined conditions, whereby the most excellent reliability is obtained.




Example 9





FIG. 8

shows a mounting structure used in Example 9. In Example 6, the electrical insulating layer is disposed only around the conductive adhesive, whereas in the mounting structure of Example 9, electrical insulating layers


31


and


35


are provided over the entire surfaces of a CSP


29


and a substrate


33


except for electrodes


30


and


34


(electrically connected to each other via a conductive adhesive


32


). In this case, substantially the same results as those in Example 6 as shown in Table 1 were obtained.




In Example 9, only the mounting structure has been shown, in which a CSP is mounted on a mother substrate; however, it is appreciated that the present example is applicable to any other mounting. Other examples include mounting in which electronic components (chip components, bare chips, etc.) other than package components are mounted on a mother substrate, primary mounting in which a semiconductor chip in a package component is mounted on a carrier substrate, etc.




Example 10




As shown in

FIG. 12

, the mounting structure of Example 10 has a ceramic CSP


51


with metal electrodes


53


formed thereon and a mother substrate


52


with metal electrodes


54


formed thereon, and the metal electrodes


53


and


54


are electrically connected to each other via a conductive adhesive


55


.




The mounting structure of Example 10 was produced as follows. First, a solvent (diethylene glycol dibutyl ether) was sprayed onto the surfaces of the metal electrodes


53


and


54


. The resultant metal electrodes


53


and


54


were dried at 150° C. for 10 minutes, whereby a solvent layer was formed to a thickness of 5 μm in a coating amount of 5 mg/cm


2


on each surface of the metal electrodes


53


and


54


.




Then, the conductive adhesive


55


was supplied to the surfaces of the solvent layers formed on the metal electrodes


54


by screen printing. Thereafter, the ceramic SCP


51


was placed on the mother substrate


52


in such a manner that the metal electrodes


53


faced the conductive adhesive


55


. The layered structure thus obtained was heated at 150° C. for 30 minutes, whereby the conductive adhesive


55


was cured. At this time, the solvent layer flowed along the adhesion interface to evaporate due to the heat, so that the solvent layer did not remain in the completed mounting structure.




As shown in

FIG. 13

, in the mounting structure of Example 10, binder resin


55




a


in the conductive adhesive


55


flowed along the adhesion interface between the conductive adhesive


55


and the metal electrode


54


. Then, the binder resin


55




a


adhered to a portion formed of a side surface


54




a


of the metal electrode


54


and a surface


52




a


on the mother substrate


52


to form a fillet


56


. Furthermore, the content of a conductive filler


55




b


in the conductive adhesive


55


became highest at the adhesion interfaces between the conductive adhesive


55


and the metal electrodes


53


and


54


. In contrast, the content of the binder resin


55




a


in the fillet


56


was high.




In the present example, NH-010A (Trade name) produced by Nippon Handa Co., Ltd. was used as the conductive adhesive


55


. The conductive adhesive


55


was a silver-type conductive adhesive containing silver powder as a metal filler in binder resin made of epoxy resin.




The detail of the constitution of the metal electrodes


53


and


54


is as follows.




Land number: 10×10 (lattice-shaped arrangement)




Land diameter: 0.5 mm




Land pitch: 1.0 mm




Land metal: Ni/Au-plated




The mounting structure of the present example produced as described above was evaluated for reliability in terms of adhesion strength and connection resistance as shown in the following Tests 3 and 4.




Test 3: Adhesion Strength Evaluation Test




The side face of the ceramic CSP was pressed in a direction orthogonal to a layered direction (i.e., in an in-plane direction of the ceramic CSP) after the mounting structure was fixed, whereby shearing stress was applied to the adhesion portion between the metal electrode and the conductive adhesive, and the force was measured when the adhesion portion was broken.




Test 4: Connection Resistance Evaluation Test




The mounting structure was placed in a temperature cycle test tank, whereby connection resistance was monitored. The test was conducted at −40° C. to 125° C., with each temperature being kept for 30 minutes (one cycle). The test was conducted up to 1000 cycles. The connection resistance was obtained by measuring series resistance of adhesion portions connected to each other by using a daisy-chain.




For comparison, a mounting structure (Comparative Example 2) was produced by a conventional method in which a metal electrode is directly connected to a conductive adhesive without using a solvent. The mounting structure was subjected to the tests under the same conditions as the above.




Comparative Example 2




Using the same materials as those of the mounting structure of Example 10, electrodes were directly connected to a conductive adhesive, whereby a mounting structure was produced. Comparative Example 2 is different from Example 10 in that a solvent layer was not formed on the electrodes, and the electrodes were directly connected to the conductive adhesive in the course of production.




In the mounting structure of Comparative Example 2, as shown in

FIG. 14

, a conductive adhesive


65


(containing binder resin


65




a


and a metal filler


65




b


) was cured while keeping its shape in coating. The binder resin


65




a


was not found to flow along the adhesion interfaces between the conductive adhesive


65


and metal electrodes


63


on a CSP


61


and electrodes


64


on a substrate


62


.




As shown in

FIG. 15

, in the mounting structure of Comparative Example 2, the content of the binder resin


65




a


in the conductive adhesive


65


was substantially uniform at the adhesion interfaces between the conductive adhesive


65


and the metal electrodes


63


and


64


and in the other portions. More specifically, a relatively large amount of the binder resin


65




a


was present even at the adhesion interfaces between the conductive adhesive


65


and the metal electrodes


63


and


64


.




The result of Test 3 of Comparative Example 2 was 10.4 kgf, and the result of Test 4 thereof was 12.5 Ω (increased at the 25th cycle). In contrast, the result of Test 3 of Example 10 was 17.4 kgf, and the result of Test 4 thereof was 7.5 Ω (increased at the 667th cycle)




More specifically, it is understood that in the mounting structure of Example 10, adhesion strength was improved, and connection resistance was decreased and stabilized, compared with the mounting structure of Comparative Example 2 by the conventional mounting method.




In the present example, diethylene glycol dibutyl ether was used as a solvent. However, monovalent alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, etc.), ketones (acetone, methyl ethyl ketone, etc.), esters (acetic acid n-butyl, etc.), glycols (ethylene glycol, diethylene glycol, propylene glycol, etc.), or glycol ethers (ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, etc.) may be used.




In the present example, a silver filler was used as a filler for the conductive adhesive. However, a nickel filler, a copper filler, a silver-palladium filler, or a silver-coated copper filler may be used. Furthermore, as the binder resin, epoxy resin was used. However, acrylic resin, silicon resin, etc. may be used.




Example 11




A mounting structure was produced in the same way as in Example 10, by using 100 parts of the solvent (diethylene glycol dibutyl ether) used in Example 10 with 5 parts of iminodiacetic acid added thereto as a component having a metal-adsorbing functional group or a functional group that chemically reacts with metal.




Observation of the resultant mounting structure revealed that, in the same way as in Example 10, the binder resin in the conductive adhesive flowed along the adhesion interface to adhere to the cross-section of the electrode, thereby forming a fillet. It was also found that the content of the binder resin in the conductive adhesive was lowest at the adhesion interface.




The results of Tests 3 and 4 of the mounting structure of Example 11 were 23.6 kgf, and 5.3 Ω (increased at the 779th cycle), respectively. It is understood from these results that the mounting structure of the present example had its adhesion strength improved and its connection resistance decreased and stabilized, compared with those of Comparative Example 2 and Example 10.




In the present example, diethylene glycol dibutyl ether was used as a solvent. However, monovalent alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, etc.), ketones (acetone, methyl ethyl ketone, etc.), esters (acetic acid n-butyl, etc.), glycols (ethylene glycol, diethylene glycol, propylene glycol, etc.), or glycol ethers (ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, etc.) may be used.




In the present example, a silver filler was used as a filler for the conductive adhesive. However, a nickel filler, a copper filler, a silver-palladium filler, or a silver-coated copper filler may be used. Furthermore, as the binder resin, epoxy resin was used. However, acrylic resin, silicon resin, etc. may be used.




Furthermore, in the present example, as a component having a metal-adsorbing functional group or a functional group that chemically reacts with metal, iminodiacetic acid was used. However, a component having at least one functional group selected from a hydroxyl group, a carboxyl group, a vinyl group, an epoxy group, an amino group, a methacryl group, a mercapto group, an iminodiacetic acid group, an iminodipropionic acid group, an ethylenediamine acetic acid group, and an aminocarboxyl group may be used.




Example 12




A mounting structure was produced in the same way as in Example 10, by using 100 parts of the solvent (diethylene glycol dibutyl ether) used in Example 10 with 5 parts of ascorbic acid added thereto as a component having a reducing property.




Observation of the resultant mounting structure revealed that, in the same way as in Example 10, the binder resin in the conductive adhesive flowed along the adhesion interface to adhere to the cross-section of the electrode, thereby forming a fillet. It was also found that the content of the binder resin in the conductive adhesive was lowest at the adhesion interface.




The results of Tests 3 and 4 of the mounting structures of the present example were 25.8 kgf, and 3.7 Ω (increased at the 995th cycle), respectively. It is understood from these results that the mounting structure of the present example had its adhesion strength further improved and its connection resistance further decreased and stabilized, compared with those of Comparative Example 2 and Examples 10 and 11.




In the present example, diethylene glycol dibutyl ether was used as a solvent. However, monovalent alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, etc.), ketones (acetone, methyl ethyl ketone, etc.), esters (acetic acid n-butyl, etc.), glycols (ethylene glycol, diethylene glycol, propylene glycol, etc.), or glycol ethers (ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, etc.) may be used.




In the present example, a silver filler was used as a filler for the conductive adhesive. However, a nickel filler, a copper filler, a silver-palladium filler, or a silver-coated copper filler may be used. Furthermore, as the binder resin, epoxy resin was used. However, acrylic resin, silicon resin, etc. may be used.




Furthermore, in the present example, ascorbic acid was used as a component having a reducing property. However, at least one selected from reducing sugars, reducing vitamins, hydroxybenzenes, amines, formic acid, polyhydric alcohols, glycol ethers, hydrazines, Rochelle salt, acetoaldehyde, gluoxal, and hypophosphorous acid may be used.




Example 13




In the mounting structure of Example 13, as shown in

FIG. 16

, metal electrodes


73


on a ceramic chip capacitor (size 3012)


71


are electrically connected to metal electrodes


74


on a mother substrate


72


via a conductive adhesive


75


(containing a conductive adhesive


75




a


and a metal filler


75




b


).




The mounting structure of Example 13 was produced as follows. First, a solvent (diethylene glycol dibutyl ether) was sprayed onto the surfaces of the metal electrodes


73


and


74


. The resultant layered structures were dried at 150° C. for 10 minutes, whereby a solvent layer was formed to a thickness of 5 μm in a coating amount of 5 mg/cm


2


on each surface of the metal electrodes


73


and


74


.




Next, the conductive adhesive


75


was supplied to the surfaces of the solvent layers formed on the metal electrodes


74


by screen printing. Thereafter, the ceramic chip capacitor


71


was placed on the mother substrate


72


in such a manner that the metal electrodes


73


faced the conductive adhesive


75


. The layered structure thus obtained was heated at 150° C. for 30 minutes, whereby the conductive adhesive


75


was cured. At this time, the solvent layer flowed along the adhesion interface to evaporate due to the heat, so that the solvent layer did not remain in the completed mounting structure.




As shown in

FIG. 17

, in the mounting structure of the present example, the binder resin


75




a


in the conductive adhesive


75


flowed along the adhesion interface between the conductive adhesive


75


and the metal electrode


74


. Then, the binder resin


75




a


adhered to a side surface


74




a


of the metal electrode


74


and a peripheral portion


72




a


on the mother substrate


72


to form a fillet


76


. The fillet was also formed on the ceramic chip capacitor


71


in the same way as on the mother substrate


72


. Furthermore, the content of the binder resin


75




a


in the conductive adhesive


75


became lowest at the adhesion interfaces between the conductive adhesive


75


and the metal electrodes


73


and


74


.




The conductive adhesive used in the present example is the same as that in Example 10. Furthermore, the constitution of the metal electrodes


73


and


74


is the same as that in Example 10.




For comparison, a mounting structure (Comparative Example 3) was produced by a conventional method in which metal electrodes are directly connected to a conductive adhesive without using a solvent.




Comparative Example 3




Using the same materials as those in Example 13, as shown in

FIG. 18

, a mounting structure was produced, in which metal electrodes


83


on a ceramic chip capacitor (size 3012)


81


are electrically connected to metal electrodes


84


on a mother substrate


82


via a conductive adhesive


85


(containing a conductive adhesive


85




a


and a metal filler


85




b


). The mounting structure of Comparative Example 3 is different from that of Example 13 in that an electrode was directly connected to a conductive adhesive without forming a solvent layer on the electrode in the course of production.




In the mounting structure of Comparative Example 3 thus obtained, as shown in

FIG. 18

, the conductive adhesive


85


was cured while keeping its shape in coating, and no binder resin was found to flow along the adhesion interfaces between the metal electrodes and the conductive adhesive.




As shown in

FIG. 19

, in the mounting structure of Comparative Example 3, the content of binder resin


85




a


in the conductive adhesive


85


was substantially uniform at the adhesion interfaces between the conductive adhesive


85


and the metal electrodes


83


and


84


, and in the other portions. More specifically, a relatively large amount of the binder resin


85




a


was present even at the adhesion interfaces between the conductive adhesive


85


and the metal electrodes


83


and


84


.




The mounting structures of Example 13 and Comparative Example 3 were subjected to Tests 3 and 4. The result of Test 3 of Comparative Example 3 was 3.5 kgf, and the result of Test 4 thereof was 0.45 Ω (increased at the 750th cycle). In contrast, the result of Test 3 of Example 13 was 10.4 kgf, and the result of Test 4 thereof was 0.12 Ω (stable until the 1000th cycle)




More specifically, it was confirmed that in the mounting structure of Example 13, adhesion strength was improved, and connection resistance was decreased and stabilized, compared with the conventional mounting structure of Comparative Example 3.




In Example 13, diethylene glycol dibutyl ether was used as a solvent. However, monovalent alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, etc.), ketones (acetone, methyl ethyl ketone, etc.), esters (acetic acid n-butyl, etc.), glycols (ethylene glycol, diethylene glycol, propylene glycol, etc.), or glycol ethers (ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, etc.) may be used.




In Example 13, a silver filler was used as a filler for the conductive adhesive. However, a nickel filler, a copper filler, a silver-palladium filler, or a silver-coated copper filler may be used. Furthermore, as the binder resin, epoxy resin was used. However, acrylic resin, silicon resin, etc. may be used.




As described above, in the mounting structures of Examples 10 to 13, a solvent layer is formed at an adhesion interface between a metal electrode and a conductive adhesive in the course of production. As a result, compared with the mounting structure produced by directly connecting the metal electrode to the conductive adhesive as in the conventional example, the adhesion reliability is remarkably improved, and connection resistance is decreased and stabilized.




In each of the above-mentioned examples, only mounting structures have been described in which a ceramic CSP is mounted on a mother substrate (Examples 10 to 12) and in which a ceramic chip capacitor is mounted on a mother substrate (Example 13). However, it is appreciated that the present invention is applicable to other mounting in which a quad flood package is mounted on a mother substrate, a BGA is mounted on a mother substrate, a lead component is mounted on a mother substrate, a flip chip is mounted between an LSI chip and a carrier substrate, etc.




The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.



Claims
  • 1. A method for producing a mounting structure for an electronic component including a conductive adhesive and a metal electrode electrically connected to each other, comprising:coating the metal electrode with a solvent that dissolves binder resin in the conductive adhesive; coating the solvent with the conductive adhesive; and curing the conductive adhesive by heating so as to connect the metal electrode to the conductive adhesive.
  • 2. A method for producing a mounting structure for an electronic component according to claim 1, wherein the solvent is at least one selected from the group consisting of monovalent alcohols, ketones, esters, glycols, and glycol ethers.
  • 3. A method for producing a mounting structure for an electronic component according to claim 1, wherein the solvent contains a component having a metal-adsorbing functional group or a functional group that chemically reacts with metal.
  • 4. A method for producing a mounting structure for an electronic component according to claim 3, wherein the component has at least one functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a vinyl group, an epoxy group, an amino group, a methacryl group, a mercapto group, an iminodiacetic acid group, an iminodipropionic acid group, an ethylenediamine acetic acid group, and an aminocarboxyl group.
  • 5. A method for producing a mounting structure for an electronic component according to claim 1, wherein the solvent contains a component having a reducing property.
  • 6. A method for producing a mounting structure for an electronic component according to claim 5, wherein the component having a reducing property is at least one selected from the group consisting of reducing sugars, reducing vitamins, hydroxybenzenes, amines, formic acid, polyhydric alcohols, glycol ethers, hydrazines, Rochelle salt, acetoaldehyde, glyoxal, and hypophosphorous acid.
  • 7. A method for producing a mounting structure for an electronic component according to claim 1, wherein coating of the solvent is conducted by spray coating.
  • 8. A method for producing a mounting structure for an electronic component according to claim 1, wherein a coating amount of the solvent is set in a range of 0.01 mg to 1000 mg/cm2 so as to form a solvent layer.
  • 9. A method for producing a mounting structure for an electronic component according to claim 1, wherein the mounting structure further comprises a second electrode, prior to curing the conductive adhesive, the second electrode is coated with a solvent that dissolves binder resin in a conductive adhesive, and a surface of the solvent on the second electrode is placed onto the conductive adhesive.
Priority Claims (2)
Number Date Country Kind
11-062759 Mar 1999 JP
11-155346 Jun 1999 JP
Parent Case Info

This application is a divisional of application Ser. No. 09/965,768, filed Sep. 27, 2001, now U.S. Pat. No. 6,569,512 which is a division of application Ser. No. 09/519,984, filed Mar. 7, 2000 now U.S. Pat. No. 6,376,051 application(s) are incorporated herein by reference.

US Referenced Citations (7)
Number Name Date Kind
5162087 Fukuzawa et al. Nov 1992 A
5179460 Hinata et al. Jan 1993 A
5525838 Kaneko Jun 1996 A
5651179 Besseho et al. Jul 1997 A
5670826 Besseho et al. Sep 1997 A
6207550 Hase et al. Mar 2001 B1
6264785 Ikeda Jul 2001 B1
Foreign Referenced Citations (5)
Number Date Country
3638858 May 1987 DE
645 805 Mar 1995 EP
59-172571 Sep 1984 JP
403223380 Oct 1991 JP
406053279 Feb 1994 JP