Patent Application
20110311831
The present invention relates to a method for manufacturing a substrate for a light emitting element package used in packaging a light emitting element such as a LED chip, as well as to a light emitting element package using a substrate for a light emitting element package manufactured by this manufacturing method.
In recent years, as illuminating and light-emitting means that can reduce the weight and thickness and can save electric power consumption, a light emitting diode has been attracting people's attention. As a mode of mounting a light emitting diode, there are known a method of mounting a bare chip (LED chip) of a light emitting diode directly on a circuit board and a method of packaging a LED chip by bonding on a small substrate so that the LED chip can be easily mounted on the circuit board and mounting this LED package on the circuit board.
A conventional LED package has a structure such that a LED chip is die-bonded onto a small substrate; the electrode part of the LED chip and the electrode part of the lead are connected with each other by wire bond or the like, and the resultant is sealed with a sealing resin having a light transmitting property.
On the other hand, a LED chip has a property such that, in an ordinary temperature region for use as an illumination appliance, the light-emitting efficiency increases according as the temperature goes down, and the light-emitting efficiency decreases according as the temperature goes up. For this reason, in a light source apparatus using a light emitting diode, quick dissipation of the heat generated in the LED chip to the outside so as to lower the temperature of the LED chip is an extremely important goal to be achieved in improving the light emitting efficiency of the LED chip. Also, by enhancing the heat dissipation characteristics, the LED chip can be energized with a large electric current, whereby the optical output of the LED chip can be increased.
Therefore, in order to improve the heat dissipation characteristics of a LED chip in place of a conventional light emitting diode, some light source apparatus are proposed in which the LED chip is directly die-bonded to a thermally conductive substrate. For example, in the following patent document 1, there is known an apparatus in which a recess is formed by performing a pressing treatment on a substrate made of a thin aluminum plate and, after a thin insulator film is formed on the surface thereof, a LED chip is die-bonded onto a bottom surface of the recess via the thin insulator film; the wiring pattern formed on the insulator film layer and the electrode on the LED chip surface are electrically connected via a bonding wire; and the inside of the recess is filled with a sealing resin having a light-transmitting property. However, with this substrate, the structure will be complex, raising problems such as a high processing cost.
Also, the following patent document 2 discloses an apparatus in which a substrate for mounting a light emitting element includes a metal substrate, a columnar metal body (metal protrusion) formed by etching at a mounting position of the metal substrate for mounting the light emitting element, an insulating layer formed around the columnar metal body, and an electrode section formed in a neighborhood of said columnar metal body.
However, according to the studies made by the present inventors, it has been found out that, in the case of mounting a LED chip on the circuit board, it will be important to dispose a columnar metal body at the mounting position thereof; however, in the case of mounting a LED package, there is not necessarily a need to dispose a columnar metal body on its substrate. In other words, it has been found out that, in the case of mounting a LED package, a sufficient heat dissipation property can be obtained by using a resin containing highly heat-conductive inorganic fillers as a material of the insulating layer of the substrate on which the LED package is to be mounted.
When reference is made to the patent document 2 from this viewpoint, with regard to the substrate for mounting a light emitting element disclosed in this document, there has further been a room for improvement as to the penetration structure of the columnar metal body, the wiring for electric power feeding, the insulating layer, and the like in packaging the LED chip.
Also, as a small substrate for packaging a LED chip, there is known one in which the insulating layer is made of ceramics; however, in manufacturing the same, firing of the ceramics and the like will be needed, so that it has not been possible to say that it is advantageous in terms of production costs and the like, and it has been disadvantageous for mass production.
Therefore, an object of the present invention is to provide a method for manufacturing a substrate for a light emitting element package that can obtain a sufficient heat dissipation effect from a light emitting element and can also enable mass production, cost reduction, and downsizing as a substrate for packaging the light emitting element, as well as a light emitting element package using the substrate for a light emitting element package manufactured by this manufacturing method.
The aforementioned object can be achieved by the present invention such as described below.
A method for manufacturing a substrate for a light emitting element package of the present invention is a method for manufacturing a substrate for a light emitting element package provided with a thick metal section formed under a mounting position of a light emitting element, characterized by having a lamination step of laminating and integrating a laminate having an insulating adhesive agent which is composed of a resin containing heat conductive fillers and has a heat conductivity of 1.0 W/mK or more and a metal layer member, with a metal layer member having a thick metal section while drawing out each member.
According to the method for manufacturing a substrate for a light emitting element package of the present invention, the laminate having an insulating adhesive agent with a good heat conductivity and a metal layer member can be laminated and integrated with the metal layer member having a thick metal section. By producing the laminate in advance, the production of the substrate for a light emitting element package can be easily carried out, thereby providing excellent mass productivity and enabling cost reduction and downsizing of the package. Further, for example, when the light emitting element is mounted on the metal layer surface side opposite to the thick metal section, the heat generated in the light emitting element is efficiently conducted by the thick metal section, and the heat is efficiently conducted further by the insulating layer having a high heat conductivity, whereby a sufficient heat dissipation effect can be obtained as a substrate for packaging.
Also, as one example of a suitable embodiment of the present invention, it is preferable that the laminate having the insulating adhesive agent and the metal layer member and/or the metal layer member having the thick metal section are provided in a roll form in advance. With this construction, the continuous production property and the mass production property will be excellent and also the yield efficiency will be good as compared with the production in sheet units.
Also, as one example of a suitable embodiment of the present invention, it is preferable that the thick metal section is laminated so that the thick metal section will be contained in the inside of the insulating layer of the laminate. With this construction, the top side of the thick metal section is buried in the insulating layer having a high heat conductivity (a state in which the insulating adhesive agent is cured; the same applies hereafter), thereby increasing the heat conduction area. Therefore, the heat from the thick metal section can be more efficiently conducted to the whole package.
Also, as one example of a suitable embodiment of the present invention, the method is characterized by having a removal step of removing the laminate so that the thick metal section will be exposed. With this construction, the top side of the thick metal section is exposed (a state in which the thick metal section penetrates through the insulating layer), and the light emitting element can be mounted directly or via an indirect layer such as a pad onto this top side of the thick metal section. In the case of such a structure, the light emitting element is mounted on the thick metal section side, so that the heat generated in the light emitting element is efficiently conducted. Furthermore, the heat is efficiently conducted to the insulating layer side via the thick metal section.
Also, as one example of a suitable embodiment of the present invention, it is preferable that the method further includes a step of winding and collecting in a roll form after the lamination step. With this construction, by winding and collecting the laminate (substrate member) having been subjected to the lamination step in a roll form, the laminate can be easily transported to the next step, and the laminate (substrate member) can be easily drawn out, for example, in the patterning step or in the cutting step. Also, the area for storage can be reduced.
Also, the light emitting element package of the present invention is constructed by using a substrate for a light emitting element package manufactured by the above-described manufacturing method. Therefore, the light emitting element package can be manufactured at a low cost and to have a small scale.
Hereafter, embodiments of the present invention will be described with reference to the drawings.
Referring to
In the present embodiment, the light emitting element 4 is mounted directly on the mounting surface 2a of the metal layer 21. The thick metal section 2 is formed to be thick from the mounting surface 2a towards a back side of the insulating layer 1, and the top side thereof is contained in the inside of the insulating layer 1 (buried state). In this manner, in the case of a structure in which the top side of the thick metal section 2 does not penetrate through the insulating layer 1, the structure can be produced by a later-mentioned pressing treatment, thereby enabling mass production, cost reduction, and downsizing.
The insulating layer 1 in the present invention has a heat conductivity of 1.0 W/mK or more, preferably a heat conductivity of 1.2 W/mK or more, more preferably a heat conductivity of 1.5 W/mK or more. By this, the heat from the thick metal section 2 can be dissipated efficiently to the whole package. Here, the heat conductivity of the insulating layer 1 is determined by suitably selecting a blend in consideration of the amount of blending the heat conductive fillers and the particle size distribution. Typically, however, in consideration of the application property of the insulative adhesive agent before curing, the heat conductivity preferably has an upper limit of about 10 W/mK.
The insulating layer 1 is preferably composed of heat conductive fillers 1b, 1c, which are metal oxide and/or metal nitride, and a resin 1a. The metal oxide and metal nitride are preferably excellent in heat conductivity and electrically insulative. As the metal oxide, aluminum oxide, silicon oxide, beryllium oxide, and magnesium oxide can be selected. As the metal nitride, boron nitride, silicon nitride, and aluminum nitride can be selected. These can be used either alone or as a combination of two or more kinds. In particular, among the aforesaid metal oxides, aluminum oxide facilitates obtaining an insulating adhesive agent layer having both a good electric insulation property and a good heat conduction property, and also is available at a low price, so that it is preferable. Also, among the aforesaid metal nitrides, boron nitride is excellent in electric insulation property and heat conductivity, and further has a low electric permittivity, so that it is preferable.
As the heat conductive fillers 1b, 1c, those containing small-diameter fillers 1b and large-diameter fillers 1c are preferable. In this manner, by using two or more kinds of particles having different sizes (particles having different particle size distributions), the heat conductivity of the insulating layer 1 can be further improved by the heat conduction function provided by the large-diameter fillers 1c themselves and the function of enhancing the heat conductivity of the resin between the large-diameter fillers 1c that is provided by the small-diameter fillers 1b. From such a viewpoint, the median diameter of the small-diameter fillers 1b is preferably 0.5 to 2 μm, more preferably 0.5 to 1 μm. Also, the median diameter of the large-diameter fillers 1c is preferably 10 to 40 μm, more preferably 15 to 20 μm.
Also, even with a structure in which the top side of the thick metal section 2 does not penetrate through the insulating layer 1 as in the present embodiment, the large-diameter fillers 1c intervene between the top part 2b of the thick metal section 2 and the metal pattern 5a, whereby the large-diameter fillers 1c are more easily brought into contact with the top part 2b and the metal pattern 5a at the time of pressing. As a result of this, a path of heat conduction is formed between the top part 2b of the thick metal section 2 and the metal pattern 5a, thereby further improving the heat dissipation property from the thick metal section 2 to the metal pattern 5a.
As the resin 1a constituting the insulating layer 1, those having an excellent bonding force to the surface electrode section 3 and the metal pattern 5a under a cured state and not deteriorating the breakdown voltage characteristics and the like though containing the aforesaid metal oxide and/or metal nitride are selected.
As such a resin, in addition to epoxy resin, phenolic resin, and polyimide resin, various engineering plastics can be used either alone or by mixing two or more kinds. Among these, epoxy resin is preferable because of having an excellent bonding force between metals. In particular, among the epoxy resins, a bisphenol-A type epoxy resin, a bisphenol-F type epoxy resin, a hydrogenated bisphenol-A type epoxy resin, a hydrogenated bisphenol-F type epoxy resin, a triblock polymer having a bisphenol-A type epoxy resin structure at both terminal ends, and a triblock polymer having a bisphenol-F type epoxy resin structure at both terminal ends, which have a high fluidity and are excellent in the mixing property with the aforesaid metal oxide and metal nitride, are further more preferable resins.
For the metal layer 21 having the thick metal section 2, the surface electrode section 3, and the metal pattern 5a in the present invention, various metals can be used. Typically, however, any one of copper, aluminum, nickel, iron, tin, silver, and titanium or an alloy or the like containing these metals can be used. In particular, from the viewpoint of heat conduction property and electrical conduction property, copper is preferable.
The thick metal section 2 is provided in the metal layer 21. The thickness of the thick metal section 2 is preferably larger than the thickness of the metal layer 21. Also, the thickness of the metal layer 21 (h1: see
Also, in view of sufficiently conducting the heat from the light emitting element 4 to the insulating layer 1, the shape of the thick metal section 2 as viewed in a plan view is suitably selected; however, the shape is further preferably a polygonal shape such as a triangle or a quadrangle, a star-like polygonal shape such as a pentagram or a hexagram, or one in which the corners of any of these are rounded with a suitable circular arc, or further can be a shape that gradually changes from the 2a surface of the thick metal section towards the surface electrode section 3. Also, from similar reasons, the maximum width of the thick metal section 2 as viewed in a plan view is preferably 1 to 10 mm, more preferably 1 to 5 mm.
As a method for forming the thick metal section 2 in the metal layer 21, known forming methods can be adopted, so that the thick metal section 2 can be formed, for example, by etching using the photolithography method, pressing, printing, or bonding, or by a known bump-forming method. Also, in the case of forming the thick metal section 2 by etching, a protective metal layer may intervene. As the protective metal layer, for example, gold, silver, zinc, palladium, ruthenium, nickel, rhodium, a lead-tin series solder alloy, a nickel-gold alloy, or the like can be used.
The thickness of the surface electrode section 3 is preferably about 25 to 70 μm, for example. Also, the thickness of the metal pattern 5a is preferably about 25 to 70 μm, for example. Here, the metal pattern 5a may cover the whole of the back surface of the insulating layer 1 or may have a thick metal section 2 in the same manner as the metal layer 21. Regarding the metal pattern 5a, in view of evading a short circuit of the surface electrode section 3, it is preferable that at least the metal patterns 5a of the back surfaces of the surface electrode sections 3 on both sides are not electrically conducted. In particular, when the thick metal section 2 is provided also in the metal pattern 5a, attention must be paid so that a positional shift may not be generated in the following lamination and integration step. Also, it is preferable that the metal pattern 5a is formed in advance in a B-stage state of an insulating adhesive agent.
In view of enhancing the reflection efficiency, it is preferable to perform plating with a noble metal such as silver, gold, or nickel on the thick metal section 2, the metal layer 21, and the surface electrode section 3. Also, in the same manner as a conventional interconnect substrate, a solder resist may be formed, or partial solder plating may be performed.
Next, a suitable method for manufacturing a substrate for a light emitting element package of the present invention such as shown above will be described with reference to
Also, a roll body 23 is prepared in which a laminate 24 of a long insulating layer 1 in a B-stage state and a long metal layer 5 is wound up. The size in the width direction is appropriately set; however, it is preferably of the same degree as the size of the metal layer roll body 22 in the width direction. A release protective layer may be provided on the surface of the long insulating layer 1. In this case, the release protective layer is peeled off at the time of laminating with the metal layer 21.
The roll for lamination is constructed with a pair of rolls (30a, 30b), as shown in
The distance between the roll pair (30a, 30b) is constructed to be adjustable. This distance is set in accordance with the conditions such as the thickness of the laminate 25 in which the metal layer 21 and the laminate 24 are laminated, the thickness of the portion of the thick metal section 2 that is contained in the inside of the insulating layer 1, and the lamination step operation conditions (transportation speed and the like). The pressing force of the roll pair (30a, 30b) is set in accordance with the specification of each of the metal layer 21, the insulating layer 1 and the metal layer 5 constituting the laminate 24, and the laminate 25 in which these are laminated. Also, the distance between the roll pair (30a, 30b) may be fixed at the time of forming the laminate 25, or may be constructed to be movable in the vertical direction relative to the laminate 25. In the case of constructing to be movable in the vertical direction, known means can be applied and, for example, a spring, a hydraulic cylinder, an elastic member, and the like can be exemplified.
Hereafter, the manufacturing method shown in
Also, it is possible to adopt a construction in which the roll itself is heated and pressing (simultaneous heating pressing) is carried out while allowing the heat to act. It will be effective if the bonding property to the metal layer 21 is improved when the insulating layer 1 is heated. Further, it is possible to adopt a construction in which a heating apparatus is disposed on the upstream side and/or the downstream side of the roll pair (30a, 30b), whereby the bonding of the insulating layer 1 to the metal layer 21 can be efficiently carried out.
Also, it is possible to adopt a construction in which an adhesive agent is applied on the lamination surface side of the metal layer 21 and/or the insulating layer 1, whereby the bonding force can be reinforced.
Also, for the purpose of retaining and stabilizing the thickness, it is possible to adopt a construction in which a plurality of roll pairs (pressing roller pairs) and/or flat plate section pairs are disposed on the downstream side of the roll pair (30a, 30b), whereby the thickness precision of the laminate 25 can be made to be a high precision. Also, for the purpose of cooling, a cooling roller, a cooling apparatus, or the like can be provided on the downstream side of the roll pair (30a, 30b).
The laminate 25 in which the metal layer 21 and the laminate 24 are laminated with use of a roll is introduced to and passed through the inside of a heating apparatus in a suitable condition, so as to cure the insulating layer 1 in a B-stage state into a C-stage state. Subsequently, this is cut into a predetermined size with use of a cutting apparatus such as a dicer, a router, a line cutter, or a slitter. Here, the curing of the laminate 25 can be carried out after the cutting. Also, upon progressing the curing reaction before the cutting, a post-curing treatment can be carried out after the cutting. In this case, an in-line heating apparatus can be provided before the cutting or, alternatively, the curing reaction can be carried out off-line in a heating apparatus after winding and collecting in a roll form.
Subsequently, both surfaces of the laminate 25 are patterned by etching using the photolithography method or the like, so as to form the surface electrode section 3 and the metal pattern 5a, whereby the substrate for a light emitting element package of the present invention can be obtained. In this case, it is possible to adopt a construction in which a part of the metal layer 21 is removed so that the remaining part may form the surface electrode section 3. Also, it is possible to adopt a construction in which a part of the metal layer 5 is removed so that the remaining part may form the metal pattern 5a.
At this time, the substrate for a light emitting element package of the present invention may be of a type in which a single light emitting element is mounted as shown in
Also, the substrate for a light emitting element package is used by mounting a light emitting element 4 on the metal layer 21 above the thick metal section 2 of the substrate for the light emitting element package and sealing the light emitting element 4 with a sealing resin 7, for example, as shown in
In other words, the light emitting element package includes a substrate for a light emitting element package including an insulating layer 1 composed of a resin la containing heat conductive fillers 1b, 1c, a metal layer 21 provided with a thick metal section 2 formed under a mounting position of a light emitting element 4, and a surface electrode section 3 formed on a mounting side surface of the insulating layer 1; a light emitting element 4 mounted above the thick metal section 2; and a sealing resin 7 for sealing the light emitting element 4.
As the light emitting element 4 to be mounted, a LED chip, a semiconductor laser chip, and the like can be exemplified. Besides a face-up type in which both electrodes are present on an upper surface, the LED chip may be of a cathode type, an anode type, a face-down type (flip chip type), or the like depending on the back surface electrode. In the present invention, it is preferable to use a face-up type in view of the heat dissipation property.
The mounting method of the light emitting element 4 on the mounting surface of the metal layer 21 may be any bonding method such as bonding with use of an electrically conductive paste, a two-sided tape, or a solder, or a method using a heat dissipating sheet (preferably a silicone series heat dissipating sheet), a silicone series or epoxy series resin material; however, bonding by metal is preferable in view of heat dissipation.
The light emitting element 4 is electrically conducted and connected to the surface electrode sections 3 on both sides. This electrical conduction and connection can be implemented by wiring between the upper electrode of the light emitting element 4 and each of the surface electrode sections 3 by wire bonding or the like using fine metal lines 8. For wire bonding, supersonic wave, a combination of this with heating, or the like can be used.
With regard to the light emitting element package of the present embodiment, an example is shown in which a dam section 6 at the time of potting a sealing resin 7 is disposed; however, the dam section 6 can be omitted, as shown in
As a resin used for potting, a silicone series resin, an epoxy series resin, and the like can be suitably used. For potting of the sealing resin 7, the upper surface thereof is preferably formed in a convex shape in view of imparting a function of a convex lens; however, the upper surface may be formed in a planar shape or in a concave shape. The upper surface shape of the potted sealing resin 7 can be controlled by the viscosity, the application method, the affinity to the applied surface, and the like of the material to be used.
In the present invention, a transparent resin lens having a convex shape may be provided above the sealing resin 7. When the transparent resin lens has a convex shape, light can be efficiently emitted upwards from the substrate in some cases. As the lens having a convex shape, those having a circular or elliptic shape as viewed in a plan view and the like can be raised as examples. Here, the transparent resin or the transparent resin lens may be a colored one or may be one containing a fluorescent substance. In particular, in the case of containing a yellow series fluorescent substance, white light can be generated by using a blue light emitting diode.
(1) In the above-described embodiments, an example has been shown in which a light emitting element of a face-up type is mounted. However, in the present embodiment, a light emitting element of a face-down type provided with a pair of electrodes on the bottom surface may be mounted. In that case, there are cases in which there will be no need of wire bonding or the like by performing solder bonding or the like. Also, in the event that the front surface and the back surface of the light emitting element has an electrode, the wire bonding or the like can be formed with use of a single line.
(2) As another manufacturing method, the method has the following steps. From the laminate 25 obtained by lamination of the metal layer 21 and the laminate 24, the insulating layer 1 and the metal layer 5 are removed so that the thick metal section 2 may be exposed. As a removing apparatus, an apparatus that can expose the thick metal section 2 while retaining the planar property may be, for example, polishing means, exposure development, chemical treatment, or the like. Also, it is possible to adopt a construction in which only the metal layer 5 and the insulating layer 1 are removed so that the top of the thick metal section 2 may be exposed, so that, for example, it is possible to adopt a construction in which only the metal layer 5 and the insulating layer 1 are bored. Subsequently, the side on which the thick metal section 2 is exposed is patterned by etching using the photolithography method or the like, thereby to form a surface electrode section 31. Also, the metal layer 21 side can be patterned by etching using the photolithography method or the like, thereby to form a metal pattern 51. Subsequently, this is cut into a predetermined size by using a cutting apparatus such as a dicer, a router, a line cutter, or a slitter, thereby to obtain a substrate for a light emitting element package of the present invention.
Hereafter, an example will be shown that uses a substrate for a package in a state in which the thick metal section 2 manufactured by the above-described manufacturing method is exposed. As shown in
Also, as shown in
(3) In the above-described embodiment, an example has been shown having a structure such that the surface electrode section 31 is not electrically conducted to the back surface of the insulating layer 1. However, in the present invention, it is preferable that an interlayer conduction section 10 for establishing electrical conduction between the surface electrode section 31 and the back surface of the insulating layer 1 is further provided, as shown in
In the present invention, a substrate for a light emitting element package such as shown in
In this example, the lens 9 having a convex surface is bonded to the upper surface of the sealing resin 7, and a dam 6 is formed. However, the lens 9 and the dam 6 can be omitted. Also, a pad may be disposed on an upper surface of the metal bumps.
Here, as shown in
(4) In the above-described embodiment, an example has been shown in the case where the light emitting element is mounted on a substrate in which the wiring layer is a single layer. However, in the present invention, the light emitting element may be mounted on a multi-layer wiring substrate in which the wiring layers are provided as plural layers. Details of the method for forming the electrically conductive connection structure in that case are disclosed in International Patent Publication WO00/52977, and any of these can be applied.
(5) Also, as another embodiment, there is a case in which the laminate 24 is not constructed in a roll form. In this case, while drawing out the metal layer 5 provided in a roll form, an insulating adhesive agent is continuously applied on the surface, thereby to construct the laminate 24. On this laminate 24, the metal layer 21 is continuously laminated by using the aforesaid process, so as to obtain the laminate 25. At this time, the insulating adhesive agent of the laminate 24 may be half-cured into a B-stage state before lamination to the metal layer 21.
(6) As another embodiment, the base metal of the metal layer 21 is constructed in a roll form and, while drawing out this base metal provided in a roll form, a thick metal section is continuously formed by using the aforesaid process, thereby to obtain the metal layer 21. On this metal layer 21, the laminate 24 is continuously laminated by using the aforesaid process, thereby to obtain the laminate 25.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/071340 | 11/25/2008 | WO | 00 | 8/15/2011 |
