Patent Application
20160138180
1. Field of the Invention
The present invention relates to a method for fabrication of an anisotropic conductive member and a method for fabrication of an anisotropic conductive bonding package.
2. Description of the Related Art
In regard to anisotropic conductive members, since electrical connection between an electronic component such as a semiconductor element and a circuit board can be obtained simply by inserting an anisotropic conductive member between the electronic component and the circuit board and pressing the assembly, those anisotropic conductive members are widely used as electrical connection members for connecting electronic components such as semiconductor elements, or as inspection connectors for inspecting the functions of electronic components such as semiconductor elements.
For example, JP2008-270158A discloses “an anisotropic conductive member in which plural conductive paths composed of conductive members are provided in an insulating matrix such that the plural conductive paths penetrate through the insulating matrix in the thickness direction of the insulating matrix in a state of being insulated from each other, and one end of each of the conductive paths is exposed at one of the surfaces of the insulating matrix, while the other end of each of the conductive paths is exposed at the other surface of the insulating matrix, the density of the conductive paths is 2,000,000 paths/mm2 or more, and the insulating matrix is a structure formed from an anodic oxide film of an aluminum substrate having micropores.”
Furthermore, JP2011-202194A discloses “a method for fabricating a metal-filled microstructure (anisotropic conductive member), the method including a step of filling through-holes with a metal by an electrolytic plating treatment such that the virtual filling ratio of the metal (conductive paths) in the through-holes (micropores) is larger than 100%; and a step of removing, by a polishing treatment, the metal deposited on the surface of an insulating matrix by the electrolytic plating treatment, characterized in that the electrolytic plating treatment is carried out such that the difference between the average crystal grain diameter of the metal filling the interior of the through-holes and the average crystal grain diameter of the metal deposited on the surface of the insulating matrix becomes 20 nm or less.
However, regarding the anisotropic conductive member of JP2008-270158A, in regard to the production process, for example, when plural conductive paths are provided so as to penetrate through the insulating matrix, residual stress is accumulated in the interior, and there is a risk that as energy such as heat is added from the outside, the insulating matrix may become damaged. For this reason, for example, when a wiring for connecting an electronic component to the anisotropic conductive member is formed, there is a problem that damage (for example, cracking) occurs due to the heat applied at the time of wiring formation, and a decrease in the yield of packaged products is caused thereby.
Thus, in order to suppress the damage of the insulating matrix, in JP2011-202194A, production of an anisotropic conductive member is carried out such that residual stress does not occur to a large extent.
It is an object of the present invention to provide, similarly to JP2011-202194A, a method for fabricating an isotropic conductive member which can suppress the damage of an insulating matrix, and a method for fabrication of an anisotropic conductive bonding package.
The inventors of the present invention conducted a thorough investigation in order to achieve the object described above, and as a result, the inventors found that the damage of the insulating matrix is suppressed when a treatment of relaxing the residual stress is applied after conductive paths have been formed, thus completing the invention.
That is, the invention provides a method for fabrication of an anisotropic conductive member and a method for fabrication of an anisotropic conductive bonding package with the following configurations.
(1) A method for fabrication of an anisotropic conductive member, the method including a residual stress relaxation step of obtaining an anisotropic conductive member that has been subjected to a treatment for relaxing residual stress, after fabricating an anisotropic conductive member having plural conductive paths, in which plural micropores of an insulating matrix formed from an anodic oxide film are filled with a conductive member.
(2) The method for fabrication of an anisotropic conductive member according to (1), wherein the residual stress relaxation step includes a step of baking the insulating matrix.
(3) The method for fabrication of an anisotropic conductive member according to (2), wherein the residual stress relaxation step is a step of baking the insulating matrix while applying a load on at least one of one surface and the other surface of the insulating matrix.
(4) The method for fabrication of an anisotropic conductive member according to (3), wherein the load in the residual stress relaxation step is applied at a pressure of 50 g/cm2 to 2,000 g/cm2.
(5) The method for fabrication of an anisotropic conductive member according to any one of (2) to (4), wherein the baking in the residual stress relaxation step is carried out at a temperature of 50° C. to 600° C.
(6) The method for fabrication of an anisotropic conductive member according to any one of (2) to (5), wherein the baking in the residual stress relaxation step is carried out in a vacuum, in a nitrogen atmosphere, or in an argon atmosphere.
(7) The method for fabrication of an anisotropic conductive member according to (1), wherein the residual stress relaxation step is a step of applying ultrasonic vibration while immersed in a liquid.
(8) The method for fabrication of an anisotropic conductive member according to (7), wherein the residual stress relaxation step is a step of applying the ultrasonic vibration at a frequency of 20 kHz to 100 kHz.
(9) The method for fabrication of an anisotropic conductive member according to (7) or (8), wherein the residual stress relaxation step is a step of applying the ultrasonic vibration for 10 minutes or longer.
(10) A method for fabrication of an anisotropic conductive bonding package, the method including a connection unit forming step of applying a conductive material on an anisotropic conductive member obtained by the method for fabrication of an anisotropic conductive member according to any one of (1) to (9), and thereby obtaining an anisotropic conductive bonding package having a connection unit connected to at least one of plural conductive paths.
According to the invention, a method for fabrication of an anisotropic conductive member which can suppress the damage of an insulating matrix, and a method for fabrication of an anisotropic conductive bonding package can be provided.
Hereinafter, the method for fabrication of an anisotropic conductive member and the method for fabrication of an anisotropic conductive bonding package of the invention will be described in detail.
In regard to the method for fabrication of an anisotropic conductive member of the invention, the anisotropic conductive member used in the residual stress relaxation step that will be described below is an anisotropic conductive member having plural conductive paths, in which plural micropores of an insulating matrix formed from an anodic oxide film are filled with a conductive member.
Next, this anisotropic conductive member will be described using
The anisotropic conductive member 1 includes an insulating matrix 2 and plural conductive paths 3 composed of a conductive member.
The insulating matrix 2 has plural micropores 4 that penetrate therethrough in the thickness direction Z, and plural conductive paths 3 are filled in these plural micropores 4.
The plural conductive paths 3 are provided in the plural micropores 4 at least from one surface to the other surface of the insulating matrix 2; however, as illustrated in
Next, in regard to the insulating matrix and the conductive path, the material, dimension, formation and the like will be explained in detail.
[Insulating Matrix]
The insulating matrix constituting the anisotropic conductive member is a structure formed from an anodic oxide film of an aluminum substrate having micropores, and functions so as to maintain the insulating properties in the planar direction.
According to the invention, the thickness of the insulating matrix (total thicknesses of the part represented by Reference Numeral 6 in
According to the invention, from the viewpoint of more reliably securing the insulating properties between the plural conductive paths disposed in the planar direction and suppressing partial disproportionation of stress, the degree of ordering defined by the following Formula (i) for the micropores is preferably 50% or more, more preferably 70% or more, and even more preferably 80% or more.
Degree of ordering (%)=B/A×100 (i)
In Formula (i) above, A represents the total number of micropores in the measurement area. B represents the number of micropores in the measurement area for one particular micropore, in which, when a circle that is inscribed to the edge of another micropore and has the smallest radius is drawn so as to be centered on the center of the particular micropore, the circle includes the centers of six micropores other than the particular micropore.
Regarding the micropore 101 illustrated in
Regarding the micropore 104 illustrated in
Furthermore, regarding the micropore 107 illustrated in
Furthermore, from the viewpoint of making the conductive path that will be described below into a straight pipe structure, it is preferable that the micropores do not have a branched structure, that is, the ratio between the number of micropores A per unit area on one surface of the anodic oxide film and the number of micropores B per unit area on the other surface is preferably such that A/B=0.90 to 1.10, more preferably A/B=0.95 to 1.05, and particularly preferably A/B=0.98 to 1.02.
Furthermore, according to the invention, the width between the conductive paths (part represented by Reference Numeral 7 in
According to the invention, the insulating matrix can be produced by, for example, anodizing an aluminum substrate, and making the micropores generated by anodization to penetrate through the aluminum substrate. Meanwhile, alumina that is used as the material of the anodic oxide film of aluminum has an electrical resistivity of about 1014 Ω·cm, similarly to the insulating matrices (for example, a thermoplastic elastomer) that constitute conventionally known anisotropic conductive films and the like.
Here, the anodization and penetration treatment steps will be described in detail in connection with the method for fabrication of an anisotropic conductive member of the invention that will be described below.
[Conductive Path]
The conductive paths that constitute the anisotropic conductive member are formed from a conductive member, and function as conductive paths that conduct electricity in the thickness direction of the insulating matrix.
The conductive member is not particularly limited as long as it is a material having an electrical resistivity of 103 Ω·cm or less, and as specific examples thereof, gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), and indium-doped tin oxide (ITO) may be mentioned as suitable examples.
Among them, from the viewpoint of electrical conductivity, copper, gold, aluminum, and nickel are preferred, and copper and gold are more preferred. Furthermore, copper and nickel are preferred, for the reason that residual stress can be easily relaxed in the residual stress relaxation step that will be described below.
Furthermore, from the viewpoint of cost, it is more preferable that only the surfaces of the faces of the conductive paths exposed at or protruding from both surfaces of the insulating matrix (hereinafter, also referred to as “end faces”) are formed of gold.
According to the invention, the conductive paths have a pillar shape, and the diameter of the entirety of a conductive path (part represented by Reference Numeral 8 in
Furthermore, according to the invention, the length of the center line of the conductive path with respect to the thickness of the insulating matrix (length/thickness) is preferably 1.0 to 1.2, and more preferably 1.0 to 1.05. When the length of the center line of the conductive path with respect to the thickness of the insulating matrix is in this range, it can be evaluated that the conductive path has a straight pipe structure, and when electric signals are transmitted, a one-to-one response can be reliably obtained. Therefore, the anisotropic conductive member can be used more suitably as an inspection connector or an electrical connection member for electronic components.
Furthermore, according to the invention, in a case in which two ends of the conductive path protrude from both surfaces of the insulating matrix, the height of the protrusions (parts represented by Reference Numerals 3a and 3b in
According to the invention, the conductive paths exist in a state of being mutually insulated by the insulating matrix, and the density of the conductive paths is 2,000,000 paths/mm2 or more, preferably 10,000,000 paths/mm2 or more, more preferably 50,000,000 paths/mm2 or more and even more preferably 100,000,000 paths/mm2 or more.
When the density of the conductive paths is in this range, the anisotropic conductive member can still be used as an inspection connector, an electrical connection member or the like for electronic components such as semiconductor elements, even at the present time when high integration has been further advanced.
According to the invention, the distance between the respective centers of adjacent conductive paths (part represented by Reference Numeral 9 in
For the reason that the anisotropic conductive member can secure conduction of electricity at a high density while maintaining high insulating properties as described above, and can also easily relax residual stress in the residual stress relaxation step that will be described below, the thickness of the insulating matrix is preferably 1 μm to 1,000 μm, and the diameter of the conductive path is preferably 5 nm to 500 nm.
The method for fabrication of an anisotropic conductive member of the invention (hereinafter, also simply referred to as “fabrication method of the invention”) is a method for fabrication of an anisotropic conductive member, the method including a residual stress relaxation step of fabricating the aforementioned anisotropic conductive member having plural conductive paths in which plural micropores of an insulating matrix formed from an anodic oxide film are filled with a conductive member, and then obtaining an anisotropic conductive member that has been subjected to a treatment for relaxing residual stress.
Next, an example of the method for fabrication of an anisotropic conductive member of the invention is described.
It is preferable that the method for fabrication of an anisotropic conductive member of the invention includes an anodization treatment step of anodizing an aluminum substrate; after the anodization treatment step, a penetration treatment step of making plural fine pores generated by the anodization to penetrate through the aluminum substrate, and thereby obtaining an insulating matrix having plural micropores; after the penetration treatment step, a conductive path forming step of filling the interior of the plural micropores in the insulating matrix thus obtained, with a conductive member, and forming plural conductive paths; and after the conductive path forming step, a residual stress relaxation step of obtaining an anisotropic conductive member that has been subjected to a treatment for relaxing residual stress.
Next, each of the treatment steps in the fabrication method of the invention will be described in detail.
[Aluminum Substrate]
The aluminum substrate used in the fabrication method of the invention is not particularly limited, and specific examples thereof include a pure aluminum plate; an alloy plate containing aluminum as a main component and trace amounts of heteroelements; a substrate obtained by vapor depositing high-purity aluminum on low-purity aluminum (for example, a recycled material); a substrate obtained by coating the surface of a silicon wafer, quartz, glass or the like with high-purity aluminum by methods such as vapor deposition and sputtering; and a resin substrate laminated with aluminum.
According to the invention, in the aluminum substrate, the surface on which an anodic oxide film is provided by the anodization treatment step that will be described below preferably has an aluminum purity of 99.5% by mass or higher, more preferably 99.9% by mass or higher, and even more preferably 99.99% by mass or higher. When the aluminum purity is in the aforementioned range, sufficient regularity of the micropore arrangement is obtained.
Furthermore, according to the invention, it is preferable that the surface of the aluminum substrate on which the anodization treatment step that will be described below is carried out, is subjected to a degreasing treatment and a mirror surface finishing treatment in advance.
Here, in regard to the heat treatment, degreasing treatment, and mirror surface finishing treatment, treatments similar to the respective treatments described in paragraphs “0044” to “0054” of JP2008-270158A can be applied.
[Anodization Treatment Step]
The anodization step is a step of subjecting the aforementioned aluminum substrate to an anodization treatment, and thereby forming an oxide coating film having micropores on the surface of the aluminum substrate.
The anodization treatment according to the fabrication method of the invention can be carried out using a conventionally known method; however, from the viewpoint of increasing the regularity of the fine pore arrangement and more reliably securing the insulating properties of the conductive part in the planar direction, it is preferable to use a self-ordering method or a constant voltage treatment.
Here, in regard to the self-ordering method or a constant voltage treatment of the anodization treatment, treatments similar to the respective treatments described in paragraphs “0056” to “0108” and [FIG. 3] of JP2008-270158A can be applied.
[Penetration Treatment Step]
The penetration treatment step is a step of making plural fine pores generated by the anodization to penetrate the aluminum substrate, and thereby obtaining an insulating matrix having plural micropores, after the anodization treatment step.
Specific examples of the penetration treatment step include a method of dissolving an aluminum substrate after the anodization treatment step, and removing the bottom of the anodic oxide film; and a method of cutting the aluminum substrate and the anodic oxide film in the vicinity of the aluminum substrate, after the anodization treatment step.
Here, in regard to these methods for the penetration treatment step, for example, methods similar to the respective methods described in paragraphs “0110” to “0121” and [FIG. 3] and [FIG. 4] of JP2008-270158A may be used.
Through this penetration treatment step, as illustrated in
[Conductive Path Forming Step]
The conductive path forming step is a step of filling the interior of the plural micropores in the insulating matrix thus obtained, with a metal as a conductive member, and forming plural conductive paths, after the penetration treatment step.
Here, the metal to be filled is similar to the metal explained above in connection with the anisotropic conductive member.
Furthermore, regarding the method for filling the micropores with a metal, for example, methods similar to the various methods described in paragraphs “0123” to “0126” and [FIG. 4] of JP2008-270158A may be used.
Here, an insulating matrix having plural micropores is obtained after the penetration treatment step; however, strictly speaking, the inner circumferential surfaces of these plural micropores are not extended in parallel to the thickness direction of the insulating matrix, and for example, the inner circumferential surface has a slightly non-uniform shape, such as a shape which is inclined slightly inward along the direction from one surface side toward the other surface side of the insulating matrix. Therefore, when conductive paths are formed inside the plural micropores by the conductive path forming step described above, the force generated between the inner circumferential surfaces of the plural microporcs and the outer circumferential surfaces of the conductive paths becomes non-uniform depending on the position.
For example, in a case in which the inner circumferential surfaces of the plural micropores are inclined slightly inward along the direction from one surface side toward the other surface side of the insulating matrix, as illustrated in
According to the invention, the residual stress occurring due to this conductive path forming step is to be relaxed by the residual stress relaxation step that will be described below.
Through this conductive path forming step, an insulating matrix 2 having conductive paths 3 is obtained.
[Surface Smoothing Treatment]
In regard to the fabrication method of the invention, it is preferable that the fabrication method includes a surface smoothing treatment step of smothing the front surface and the back surface by a chemical mechanical polishing treatment or the like, after the conductive path forming step described above.
When a Chemical Mechanical Polishing (CMP) treatment is carried out, smoothing of the front surface and the back surface after the filling of metal and removal of any excess metal deposited on the front surface can be achieved.
For the CMP treatment, CMP slurries such as PLANERLITE-7000 manufactured by Fujimi, Incoporated., GPX HSC800 manufactured by Hitachi Chemical Co., Ltd., and CL-1000 manufactured by Asahi Glass (Seimi Chemical) Co., Ltd., can be used.
Meanwhile, since it is not intended to polish the anodic oxide film, it is not preferable to use a slurry for an interlayer insulating film or a barrier metal.
[Trimming Treatment]
According to the fabrication method of the invention, in a case in which the conductive path forming step or the CMP treatment has been applied, it is preferable that the fabrication method includes a trimming treatment step after the surface smoothing treatment step.
The trimming treatment step is a step in which, when the conductive path forming step or the CMP treatment has been applied, only the insulating matrix at the surface of the anisotropic conductive member is partially removed, and the conductive paths are caused to protrude, after the surface smoothing treatment step.
Here, regarding the trimming treatment, if conditions which do not induce dissolution of the metal that constitutes the conductive paths are adopted, the trimming treatment can be carried out by bringing the insulating matrix into contact with the aqueous acid solution or aqueous alkali solution used at the time of removing the bottom of the anodic oxide film described above, for example, by a dipping method and a spraying method. Particularly, for the trimming treatment, it is preferable to use phosphoric acid for which the dissolution rate can be easily managed.
Through this trimming step, the insulating matrix 2 having plural conductive paths 3 illustrated in
[Residual Stress Relaxation Step]
The aforementioned residual stress relaxation step is a step of applying a treatment for relaxing residual stress and thereby obtaining the anisotropic conductive member described above, after the conductive path forming step. Here, the treatment for relaxing residual stress refers to a treatment for reducing the residual stress of the insulating matrix down to 200 MPa or less.
Regarding the residual stress relaxation step, it is preferable to relax residual stress by applying a treatment for dispersing the force generated between the inner circumferential surfaces of the plural micropores and the outer circumferential surfaces of the plural conductive paths.
For example, in the residual stress relaxation step, the force generated between the inner circumferential surfaces of plural micropores and the outer circumferential surfaces of the conductive paths can be dispersed by baking the insulating matrix having plural conductive paths.
Here, regarding the temperature for baking, it is preferable that baking is performed at 50° C. to 600° C., more preferably at 100° C. to 550° C., and even more preferably at 150° C. to 400° C. When the baking temperature is 50° C. or higher, residual stress can be decreased, and when the baking temperature is 600° C. or lower, normal parts being largely deformed by excessive heating can be suppressed.
Furthermore, in the residual stress relaxation step, it is preferable that the insulating matrix is baked while a load is applied on at least any one of one surface and the other surface of the insulating substrate.
Here, it is preferable that the load is applied onto at least any one of one surface and the other surface of the insulating matrix at a pressure of 50 g/cm2 to 2,000 g/cm2, from the viewpoints of handleability, adhesiveness to the insulating matrix at the time of load application, and durability of the insulating matrix. Furthermore, for the baking temperature, it is preferable that baking is performed at 50° C. to 600° C., more preferably at 100° C. to 550° C., and even more preferably at 150° C. to 400° C., similarly to the case of the baking temperature described above.
As such, it is preferable to decrease the residual stress to 180 MPa or less, and more preferably to 165 MPa or less, by baking the insulating matrix while applying a load to at least any one of one surface and the other surface of the insulating matrix.
Specifically, as illustrated in
Subsequently, baking is performed in a state in which a load has been applied to the one surface 2a of the insulating matrix 2. As such, when baking is performed in a state in which the strain of the insulating matrix 2 has been restored, metal molecules that constitute the plural conductive paths 3 are rearranged, and fine deformation occurs in the surface shape of the plural conductive paths 3. As a result of this deformation of the plural conductive paths 3, the non-uniform force generated between the inner circumferential surfaces of the plural micropores 4 and the outer circumferential surfaces of the plural conductive paths 3 in the conductive path forming step is dispersed, and the force becomes uniform in the thickness direction of the insulating matrix 2. At this time, it is preferable to perform the above-described treatment until the residual stress reaches 180 MPa or less. Thereby, as illustrated in
Meanwhile, the baking in the residual stress relaxation step can be performed in air, in a vacuum, in a nitrogen atmosphere, in an argon atmosphere, or the like, and particularly, from the viewpoint of preventing the metal that constitutes the conductive paths from being oxidized and gaining high resistance, it is preferable to perform baking in a vacuum, in a nitrogen atmosphere, or in an argon atmosphere.
Furthermore, in the residual stress relaxation step, a treatment of dispersing the force generated between the inner circumferential surfaces of the plural micropores and the outer circumferential surfaces of the plural conductive paths by applying ultrasonic vibration while immersing the insulating matrix in a liquid, may also be carried out.
At this time, it is preferable to apply ultrasonic vibration in a state in which the entirety of the insulating matrix having plural conductive paths obtained by the above-described trimming step is immersed in a liquid. Furthermore, regarding the liquid in which the insulating matrix having plural conductive paths is immersed, for example, water, an aqueous solution, or a liquid organic compound is used, and it is preferable to use a liquid organic compound such as isopropyl alcohol (IPA) or methyl ethyl ketone (MEK).
Furthermore, it is preferable to apply the ultrasonic vibration at a frequency of 20 kHz to 100 kHz. When the ultrasonic vibration is applied at 20 kHz or more, the residual stress can be decreased to a large extent, and when the ultrasonic vibration is applied at 100 kHz or less, normal parts and the like being damaged due to excess vibration can be suppressed.
Furthermore, it is preferable to apply the ultrasonic vibration for 10 minutes or longer, more preferably for 100 minutes or longer, and even more preferably for 150 minutes or longer. When the ultrasonic vibration is applied for 10 minutes or longer, the residual stress can be decreased to a large extent.
Through this residual stress relaxation step, an anisotropic conductive member having relaxed residual stress is obtained. This anisotropic conductive member has the same configuration as that explained in connection with the anisotropic conductive member described above.
[Electrodeposition Treatment]
The fabrication method of the invention may be a fabrication method including, instead of the trimming treatment step or after the trimming treatment step, an electrodeposition treatment step of further precipitating the same or different conductive metal only on the surfaces of the conductive paths 3 illustrated in
According to the invention, an electrodeposition treatment is a treatment including an electroless plating treatment which utilizes the difference of the electronegativities of different kinds of metals.
Here, an electroless plating treatment is a step of immersing an object in an electroless plating treatment liquid (for example, a liquid obtained by appropriately mixing a reducing agent treatment liquid having a pH of 6 to 13 with a noble metal-containing treatment liquid having a pH of 1 to 9).
According to the fabrication method of the invention, it is preferable that the trimming treatment and the electrodeposition treatment are applied immediately before the use of the anisotropic conductive member. When these treatments are applied immediately before use, it is preferable because the metal of the conductive paths that constitute the bump parts is not oxidized until immediately before use.
[Anisotropic Conductive Bonding Package]
An anisotropic conductive bonding package will be described in detail below.
An anisotropic conductive bonding package fabricated by the method for fabrication of an anisotropic conductive bonding package of the invention is a package having the anisotropic conductive member described above, and a connection unit formed from a conductive material, which is electrically connected to at least one of the plural conductive paths.
The multi-chip module 11 of
The chip substrate 12 is composed of a printed wiring board, and an electrode, which is not shown in the diagram, in the printed wiring board is electrically connected to the IC chips 13 by a wiring which is not shown in the diagram. The anisotropic conductive bonding package 10 is disposed on the chip substrate 12, and the ends of the conductive paths 3 exposed at one surface 2a of the insulating matrix 2 of the anisotropic conductive member 1 are connected to a flat-shaped electrode 15a (connection unit), while the other ends of the conductive paths 3 exposed at the other surface 2b of the insulating matrix 2 are connected to a flat-shaped electrode 15b (connection unit). Furthermore, the electrode 15a is connected to an internal wiring inside the interposer 14, and the electrode 15b is connected to the IC chips 13 via a wiring, which is not shown in the diagram, of the chip substrate 12.
As such, the electrode 15a and the electrode 15b can be easily connected in the thickness direction via the anisotropic conductive member 1, and the interposer 14 and the like can be disposed by lamination.
The anisotropic conductive bonding package 10 may have a multilayer structure in which connection units formed from a conductive material and anisotropic conductive members are alternately laminated in the thickness direction, and thereby, heat dissipation performance can be enhanced, and reliability of the device can be enhanced.
[Method for Fabricating Anisotropic Conductive Bonding Package]
The method for fabrication of an anisotropic conductive bonding package of the invention is a method for fabrication of an anisotropic conductive bonding package, which includes a connection unit forming step of applying a conductive material on an anisotropic conductive member obtainable by the fabrication method described above, and thereby obtaining an anisotropic conductive bonding package having a connection unit connected to at least one of the plural conductive paths.
Regarding the conductive material, specifically, for example, any one kind of material or two or more kinds of materials selected from gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), ITO, molybdenum (Mo), iron (Fe), palladium (Pd), beryllium (Be), and rhenium (Re) can be used.
The bonding mode is not particularly limited; however, from the viewpoint of having high conduction reliability at the time of bonding, compressive bonding is preferable, and heated compressive bonding is more preferable. Furthermore, ultrasonic bonding is also preferable.
[Specific Examples of Connection Unit]
A specific example of the connection unit is, for example, an electrode, and the electrode may be any electrode formed on any member. However, the electrode is preferably an electrode which is bonded to one surface and the other surface of the anisotropic conductive member described above, and is further connected to an internal wiring inside the interposer.
The interposer is also referred to as a conversion board or a re-wiring board, and the arrangement of the electrodes can be arbitrarily designed depending on the arrangement of an external electrode connected to the surface of the interposer via an internal wiring inside the substrate. The members of the interposer other than electrodes can be produced from inorganic compounds such as a silicon wafer or a GaN substrate; and various plastics such as a glass fiber-impregnated epoxy resin and a polyimide resin.
The interposer may be bonded to one surface of the anisotropic conductive bonding package described above; however, it is preferable that the interposer is bonded as two layers such as an upper layer and a lower layer, sandwiching the anisotropic conductive bonding package as an intermediate layer.
The invention will be described specifically by way of Examples. However, the invention is not intended to be limited to these.
A high-purity aluminum substrate (manufactured by Sumitomo Light Metal Industries, Ltd., purity: 99.99% by mass, thickness: 0.4 mm) was cut to an area which measured 10 cm on each of four sides so that the aluminum substrate could be anodization treated, and the cut aluminum substrate was subjected to an electrolytic polishing treatment using an electrolytic polishing liquid having the following composition under the conditions of a voltage of 25 V, a liquid temperature of 65° C., and a liquid flow rate of 3.0 m/min.
A carbon electrode was used as a negative electrode, and GP0110-30R (manufactured by Takasago, Ltd.) was used as a power supply. Furthermore, the flow rate of the liquid electrolyte was measured using a vortex flow monitor, FLM22-10PCW (manufactured by As One Corporation.).
(Electrolytic Polishing Liquid Composition)
(B) Anodization Treatment Step
Subsequently, the aluminum substrate that had been electrolytic polishing-treated was subjected to an anodization treatment based on a self-ordering method according to the procedure described in JP2007-204802A.
The aluminum substrate that had been electrolytic polishing-treated was subjected to a preliminary anodization treatment for five hours using a 0.50 mol/L liquid electrolyte of oxalic acid under the conditions of a voltage of 40 V, a liquid temperature of 15° C., and a liquid flow rate of 3.0 m/min.
Thereafter, the aluminum substrate that had been preliminary anodization-treated was subjected to a film-removing treatment of immersing the aluminum substrate in a mixed aqueous solution of 0.2 mol/L anhydrous chromic acid and 0.6 mol/L phosphoric acid (liquid temperature: 50° C.) for 12 hours.
Subsequently, the aluminum substrate was subjected to a re-anodization treatment for 10 hours using a 0.50 mol/L liquid electrolyte of oxalic acid under the conditions of a voltage of 40 V, a liquid temperature of 15° C., and a liquid flow rate of 3.0 m/min, and thus an oxide coating film having a film thickness of 80 μm was obtained.
Meanwhile, both the preliminary anodization treatment and the re-anodization treatment were carried out using a stainless steel electrode as a negative electrode, and GP0110-30R (manufactured by Takasago, Ltd.) as a power supply. Furthermore, NcoCool BD36 (manufactured by Yamato Scientific Co., Ltd.) was used as a cooling apparatus, and PAIRSTIRRER PS-100 (manufactured by Eyela Tokyo Rikakikai Co., Ltd.) was used as a stirring and heating apparatus. Also, the flow rate of the liquid electrolyte was measured using a vortex flow monitor, FLM22-10PCW (manufactured by As One Corporation.).
(C) Penetration Treatment Step
Subsequently, the aluminum substrate was dissolved in a 20 mass % aqueous solution of mercury chloride (mercuric chloride) by immersing the aluminum substrate in the aqueous solution at 20° C. for three hours, and the bottom of the anodic oxide film was removed by immersing the aluminum substrate in 5 mass % phosphoric acid at 30° C. for 30 minutes. Thus, a structure formed from an anodic oxide film having micropores (insulating matrix) was produced.
(D) Heating Treatment
Subsequently, the structure obtained as described above was subjected to a heating treatment at a temperature of 400° C. for one hour.
(E) Electrode Film Forming Treatment
Subsequently, the structure was subjected to a treatment for forming an electrode film on one surface of the oxide coating film after the heating treatment.
That is, a 0.7 g/L aqueous solution of chloroauric acid was applied on one surface and dried at a rate of 140° C./min, and a baking treatment was carried out at a rate of 500° C./hour. Thus, a gold plating core was produced.
Thereafter, the structure was subjected to an immersion treatment at 50° C./hour using PRECIOUSFAB ACG2000 base liquid/reducing liquid (manufactured by Electroplating Engineers of Japan, Ltd.) as an electroless plating liquid, and thus a poreless electrode film was formed.
(F) Conductive Path Forming Step
Subsequently, a copper electrode was closely adhered to the surface on which the electrode film had been formed, and the structure was subjected to an electrolytic plating treatment using the copper electrode as a negative electrode and platinum as a positive electrode.
A structure in which micropores were filled with copper (anisotropic conductive member) was fabricated by using a mixed solution of copper sulfate/sulfuric acid/hydrochloric acid=200/50/15 (g/L) maintained at 25° C. as a liquid electrolyte, and performing constant-voltage pulse electrolysis.
Here, the constant-voltage pulse electrolysis was performed using a plating apparatus manufactured by Yamamoto-MS Co., Ltd., using a power supply (HZ-3000) manufactured by Hokuto Denko Corp., by performing cyclic voltammetry in a plating liquid to check the precipitation potential, and then setting the potential on the coating film side to −2 V. Furthermore, the pulse waveform of the constant-voltage pulse electrolysis was a square waveform. Specifically, an electrolysis treatment with a cycle of 60 seconds for one electrolysis time was carried out five times so that the total treatment time of electrolysis would be 300 seconds, while a resting time of 40 seconds was provided between each electrolysis treatment cycle.
(G) Surface Smoothing Treatment Step
Subsequently, the front surface and the back surface of the metal-filled structure were subjected to a CMP treatment, the electrode film formed on the oxide coating film was removed by polishing the structure having a film thickness of 80 pun, up to 15 μm each from both surfaces, and the front surface and the back surface of the oxide coating film were smoothed. Thus, a structure having a film thickness of 50 μm was obtained.
As the CMP slurry, PLANERLITE-7000 manufactured by Fujimi, Incorporated. was used.
After the CMP treatment, the surface of the structure was observed by FE-SEM, and the surface had a form in which the filling metal partially overflowed from the surface of the oxide coating film.
(H) Trimming Treatment
Subsequently, the structure that had been CMP-treated was immersed in a phosphoric acid solution, the anodic oxide film was selectively dissolved therein, and thereby pillars of the filling metal filling the micropores were caused to protrude. Thus, a structure was obtained. For the phosphoric acid solution, the same liquid as that used for the penetration treatment was used, and the treatment time was set to 5 minutes.
(I) Residual Stress Relaxation Step
Next, the structure that had been trimming-treated was subjected to baking for 45 minutes at a temperature of 210° C. while a load of 50 g/cm2 was added thereto in an open-air environment, and thus an anisotropic conductive member was obtained.
(H) Packaging Step
Next, the anisotropic conductive member obtained after the residual stress relaxation step was subjected to a thermal compression test using a thermal compression apparatus (manufactured by Kitagawa Seiki Co., Ltd., HVHC-PRESS, cylinder area: 201 cm2). Copper was used as a conductive material, and thermal compression was carried out under the conditions of a compression temperature of 240° C., a compression pressure per unit area of the electrode of 50 MPa or less, and a compression time of one minute. Thereby, an anisotropic conductive bonding package was fabricated.
Anisotropic conductive members and anisotropic conductive bonding packages were fabricated in the same manner as in Example 1, except that the baking temperature and the baking atmosphere were modified according to Table 1.
An anisotropic conductive member was fabricated in the same manner as in Example 1, except that the conductive path forming step was carried out by the method described below. Furthermore, an anisotropic conductive bonding package was fabricated in the same manner as in Example 1, except that the conductive material used in the packaging step was changed to nickel.
[Conductive Path Forming Step]
A nickel electrode was adhered to the surface on which the electrode film was formed, and the structure was subjected to an electrolytic plating treatment using the nickel electrode as a negative electrode and platinum as a positive electrode. Then, constant-current electrolysis (5 A/dm2) was carried out using a mixed solution of nickel sulfate/nickel chloride/boric acid=300/60/40 (g/L) as a liquid electrolyte in a state of being maintained at 50° C., and thereby metal filling was carried out.
Anisotropic conductive members and anisotropic conductive bonding packages were fabricated in the same manner as in Example 17, except that the baking temperature and the baking atmosphere were changed according to Table 1.
Anisotropic conductive members were fabricated in the same manner as in Example 1, except that the residual stress relaxation step was carried out by the method described below.
[Residual Stress Relaxation Step]
Anisotropic conductive members and anisotropic conductive bonding packages were fabricated by applying, after the trimming treatment, ultrasonic vibration at a frequency of about 20 kHz to 100 kHz in an isopropyl alcohol (IPA) solution for 150 minutes, 100 minutes, and 10 minutes, respectively.
Anisotropic conductive members and anisotropic conductive bonding packages were fabricated in the same manner as in Example 17, except that the residual stress relaxation step was carried out by the method described below.
[Residual Stress Relaxation Step]
Anisotropic conductive members were fabricated by applying, after the trimming treatment, ultrasonic vibration at a frequency of about 20 kHz to 100 kHz in an isopropyl alcohol (IPA) solution for 150 minutes, 100 minutes, and 10 minutes, respectively.
An anisotropic conductive member and an anisotropic conductive bonding package were fabricated in the same manner as in Example 13, except that baking was carried out without applying a load in the residual stress relaxation step.
An anisotropic conductive member and an anisotropic conductive bonding package were fabricated in the same manner as in Example 16, except that baking was carried out without applying a load in the residual stress relaxation step.
An anisotropic conductive member and an anisotropic conductive bonding package were fabricated in the same manner as in Example 21, except that baking was carried out without applying a load in the residual stress relaxation step.
An anisotropic conductive member and an anisotropic conductive bonding package were fabricated in the same manner as in Example 24, except that baking was carried out without applying a load in the residual stress relaxation step.
An anisotropic conductive member and an anisotropic conductive bonding package were fabricated in the same manner as in Example 1, except that the residual stress relaxation step was excluded.
An anisotropic conductive member and an anisotropic conductive bonding package were fabricated in the same manner as in Example 17, except that the residual stress relaxation step was excluded.
(Evaluation Method)
The residual stress was calculated by the 2θ·sin2ψ method using an X-ray diffraction apparatus (XRD, manufactured by Bruker BioSpin K.K., D8 Discover with GADDS). Measurement was made under the conditions of voltage/current of 45 kV/110 mA, CrKα line for the X-ray wavelength, and an X-ray irradiation diameter of 500 μm, and using Cu (311) surface or Ni (311) surface as the evaluation crystal plane. These results are presented in the following Table 1.
Regarding the number of cracks, ten samples of anisotropic conductive bonding packages were fabricated, the number of cracks was determined for each of the samples by observing the internal structure of the anisotropic conductive bonding package using a microfocus X-ray CT (manufactured by Shimadzu Corp, SMX-160CTS), and the average value of the numbers of cracks was calculated. These results are presented in the following Table 1.
Regarding the fluctuation of the wiring resistance value, ten samples of anisotropic conductive bonding packages were fabricated, the wiring resistance was measured 30 times per sample, and the standard deviation of the resistance values (Ω) thus obtained was calculated. As the standard deviation is smaller, there is no breakdown at the time of wiring, and the yield of the anisotropic conductive bonding package is improved. For the measurement of the wiring resistance value, it was checked that electrical connection was achieved for each conductive path, by polishing a cross-section of the anisotropic conductive film, and the direct current voltage and current were measured using the anisotropic conductive bonding package for which electric connection could be confirmed. Thus, the resistance value was calculated. The results are presented in the following Table 1.
From the results shown in Table 1, in Examples 1 to 34 that had been subjected to the residual stress relaxation step, the residual stress and the number of cracks decreased compared to Comparative Examples 1 and 2, and thus, it was found that damage of the insulating matrix can be suppressed.
Particularly, in Examples 1 to 24 that had been baked while a load was applied thereto in the residual stress relaxation step, the residual stress decreased to a large extent as compared to Examples 31 to 34 that had been baked without applying a load, and thus, it was found that baking under a load can significantly contribute to a decrease in residual stress.
Furthermore, in Examples 25 to 30 that had been subjected to ultrasonic vibration in the residual stress relaxation step, the residual stress decreased to a large extent as compared to Comparative Examples 1 and 2 to which ultrasonic waves were not applied, and thus, it was found that application of ultrasonic waves can significantly contribute to a decrease in residual stress.
Furthermore, in Examples 1 to 24 that had been baked while a load was applied thereto in the residual stress relaxation step, when a comparison was made with samples produced under the same conditions of the baking atmosphere, the metal species of the conductive paths, and load application, the residual stress decreased more as the baking temperature became higher, and thus, it was found that the baking temperature can significantly contribute to a decrease in residual stress.
Furthermore, in Examples 25 to 30 that had been subjected to ultrasonic vibration in the residual stress relaxation step, when a comparison was made with samples produced under the same conditions of the baking atmosphere and the metal species of the conductive paths, the residual stress decreased more as the time for applying ultrasonic vibration became longer. Thus, it was found that the time for applying ultrasonic vibration can significantly contribute to a decrease in residual stress.
Furthermore, in Examples 1 to 24 that had been subjected to baking in the residual stress relaxation step, the residual stress decreased down to 180 MPa or less independently of the difference in the baking atmosphere, and it was found that none of the baking atmospheres of air, nitrogen, argon, and vacuum disrupts relaxation of the residual stress.
Furthermore, in Examples 1 to 30, the residual stress decreased down to 180 MPa or less independently of the metal species of the conductive path, and it was found that relaxation of the residual stress is not disrupted even if any metal between copper and nickel is used in the conductive path.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-151603 | Jul 2013 | JP | national |
This application is a Continuation of PCT International Application No. PCT/JP2014/069239 filed on Jul. 18, 2014, which claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2013-151603 filed on Jul. 22, 2013. The above application is hereby expressly incorporated by reference, in its entirety, into the present application.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2014/069239 | Jul 2014 | US |
| Child | 15003154 | US |
