JPH09232485A - Compound material for electric part and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small, thin, light heat spreader. SOLUTION: The compound material for electronic part is provided with a sintered layer 8 made from particles mainly comprising copper of copper alloy at least on one surface of a low expansion Fe-Ni base alloy thin plate 6 and bore holes 7. At this time, the sintered layer, preferably fills up said bore holes 7 also covering the bore hole 7 part and non-bore holes parts to form a flat surface. In such a constitution, the material can be manufactured by thermal sintering step or rolling step after further thermal sintering step after coating at least one surface of low expansion Fe-Ni base alloy 6 having a plurality of bore holes and the bore holes 7 with particles mainly comprising copper and copper alloy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer substrate such as a heat spreader for a semiconductor element or a heat sink,
In particular, the present invention relates to a composite material for electronic parts having improved heat dissipation in the plate thickness direction and a method for producing the same.

[0002]

2. Description of the Related Art PGAs (Pin Grid A) are mainly used in CPUs (Central Processing Units) of large computers, workstations, personal computers (PCs), etc.
A ceramic package called “ray” is applied, and the heat generated from the Si chip is generated by the Si chip and Al.
It is dissipated through a heat transfer substrate (heat spreader) between the heat sink fins. On the other hand, in recent LSIs, dissipation of heat generated from a Si chip has become an extremely important issue due to higher speed and higher power consumption. In particular, a microcomputer or a logic ASIC (Application).
In LSIs for n Specific ICs) and the like, a heat spreader is brought into contact with a Si chip to promote heat dissipation.

For example, a BGA (Ball G) shown in FIG.
An example of a "rid Array" package includes a heat sink 1, a silicon chip 2, Cu wiring 3, a polyimide film 4 for insulation, and solder balls as terminals 5. In this structure, the heat sink is in contact with the silicon chip 2, and it is important that the thermal expansion coefficient of the heat dissipation from the heat generated from the LSI and the thermal expansion coefficient of the silicon chip are matched. Demand for these new types of packages is expected to increase in the future. Such heat transfer substrate (heat spreader) is made of Si
In order to contact the chip, its thermal expansion must match that of the Si chip, and the coefficient of thermal expansion is generally 1
It is said that a material of about 11 × 10 -6 powers / ° C is desirable.

In order to satisfy these characteristics, a plate of 0.5 to 1 mm thick and made of Cu-W or Mo and about 30 mm square has been conventionally used for a heat spreader. However, since these materials are expensive and have a large specific gravity, the weight of the package is inevitably large, which is a major drawback in terms of downsizing which is a recent trend of LSI.

In the package of the type that uses a lead frame among LSIs, a method of forming the lead frame itself from copper and a copper alloy having a good heat dissipation property is also adopted, but in this case, the coefficient of thermal expansion is a Si chip. Since it is larger than the above, internal stress at the interface between the Si chip and the lead frame becomes a problem, and cracks may occur in the Si chip due to stress generation during the process or during use. As a material for solving this point, the present inventors have made a composite material for electronic parts in which a sintered layer of a powder mainly composed of copper or a copper alloy is formed on at least one surface of a low-expansion Fe-Ni alloy thin plate, and a composite material thereof. Japanese Patent Application No. 7-
It has been filed as No. 59708.

However, in the package of the type which does not use the lead frame, the above-mentioned heat dissipation by the lead frame cannot be applied, and in this respect, it is possible to replace the Cu-W and Mo plates with inexpensive and small size, thin and lightweight. Heat spreader is needed. The type of package that does not use the lead frame is the PGA mentioned above.
Recently, the BGA (Ball) shown in FIG.
Grid Array), CSP (Chip Siz)
ePackage) has been put to practical use, and great demand is expected in the future.

[0007]

As a low-expansion material replacing the Cu-W and Mo plates, Japanese Patent Laid-Open No. 3-179768 discloses a composite material of Fe-Ni alloy and copper or copper alloy. . However, the composite material described in Japanese Patent Application Laid-Open No. 3-179768 and the like is a material that is subjected to melting, hot working, cold working and mechanically pressure-bonded by cold rolling or the like, and an unbonded portion is generated. However, the manufacturing cost and the production yield are considerably high.

Further, in Japanese Patent Laid-Open No. 2-231751 and Japanese Patent Publication No. 7-80272, a low thermal expansion metal plate having a through hole in the thickness direction is pressure-welded and integrated with one or both surfaces of a copper or copper alloy plate. A lead frame material or a heat conductive composite material in which copper or a copper alloy is exposed has been proposed. In this method, the above-mentioned JP-A-3-17976 is used.
As in the case of No. 8 etc., the cost is inevitably high in terms of manufacturing man-hours and yield, and copper or copper alloy in the through hole is exposed in the low expansion metal plate, When plating is performed, the surface state after plating may be non-uniform due to corrosion of the acid solution at the boundary of the through holes during the pretreatment or the exposure of different metals.
INDUSTRIAL APPLICABILITY The present invention is advantageous in cost and has excellent heat dissipation properties, particularly in the plate thickness direction, and is for electronic components that enables miniaturization, thinning, and weight reduction of heat transfer substrates (heat spreaders) such as LSIs. A composite material and a method for manufacturing the same are provided.

[0009]

DISCLOSURE OF THE INVENTION The inventor of the present invention aims to develop a material that is inexpensive and has excellent heat dissipation properties, particularly heat dissipation properties in the plate thickness direction, and that does not have unevenness on the surface during plating treatment. , A method of forming a layer mainly composed of copper or a copper alloy excellent in heat dissipation in at least one surface of a low expansion Fe-Ni alloy thin plate having a plurality of perforations and in the perforations, and copper or a copper alloy The present inventors have succeeded in developing an inexpensive composite material having excellent heat dissipation properties by powder-metallurgically bonding a powder mainly composed of Fe to a Fe-Ni alloy having a plurality of perforations.

That is, the present invention is a composite for electronic parts in which a sintered layer of a powder mainly composed of copper or copper alloy is formed in at least one surface of a low expansion Fe-Ni alloy thin plate having a plurality of perforations and in the perforations. It is a material. Preferably, a sintered layer fills the perforations and the Fe-Ni
A composite material for electronic parts, characterized in that a flat surface is formed by covering a perforated portion and a non-perforated portion of a system alloy. The composite material for electronic parts of the present invention is obtained by applying a powder containing copper or a copper alloy as a main component to at least one surface of a low expansion Fe-Ni alloy thin plate having a plurality of perforations and the perforations, and then heating and sintering. Alternatively, it can be obtained by the method for producing a composite material for electronic parts according to the present invention, in which heating and sintering are followed by rolling.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION One of the features of the present invention is that a low-expansion Fe-Ni alloy thin plate having perforations is used to form a sintered layer mainly composed of copper or a copper alloy. By using a sintered layer, the number of manufacturing steps can be reduced compared to the conventional pressure bonding method, and the yield is high, so that it can be manufactured at low cost. Further, by forming a sintered layer, it is a sintered layer mainly composed of copper or a copper alloy excellent in heat dissipation, and the Fe-Ni alloy having a low expansion property is sufficiently integrated through the holes. Excellent heat dissipation, particularly excellent heat dissipation in the plate thickness direction.

In the present invention, the formation of a plurality of perforations is important for performing heat diffusion in the plate thickness direction. That is,
Due to the copper or copper alloy filled in the perforations, the thermal conductivity in the plate thickness direction can be made significantly higher than in the case where no perforations are provided. Further, by performing rolling after sintering, it is possible to reduce voids or voids existing in the as-sintered state, and to firmly integrate the Fe—Ni-based alloy and the sintered layer. In addition, rolling can increase the plate thickness accuracy of the material and at the same time make the surface condition smoother and more uniform, which is effective in obtaining a good surface texture in the plating treatment as described above. . This rolling also improves the mechanical strength of the composite material.

The composite material of the present invention can also be obtained by forming a layer containing copper or a copper alloy as a main component on an Fe-Ni alloy material, rolling it after drying, and then sintering it. In this case, rolling is more effective in reducing voids or voids as described above. Further, rolling may be further performed after sintering. In this case, in addition to the reduction of voids or voids as described above, there are the effects of improving the plate thickness accuracy, improving the surface condition, and improving the mechanical strength. FIG. 1 shows the basic structure of a composite material of the present invention in which a sintered layer mainly composed of copper or a copper alloy (hereinafter referred to as Cu sintered layer) is formed of a low expansion Fe—Ni-based alloy. FIG. 1A shows a composite material of the present invention after formation of a sintered layer, and as an example, Cu sintering mainly composed of copper or copper alloy in the perforations 7 of the Fe—Ni alloy thin plate 6 and on both surfaces. FIG. 1 (b) shows a case where the layer 8 is provided, and FIG. 1 (b) shows a Cu sintered layer 8 mainly composed of copper or copper alloy in the perforations 7 of the Fe—Ni alloy thin plate 6 and on one surface. This is the case. 3 shows a Fe—Ni alloy thin plate 6 having a large number of perforations before forming a sintered layer in the composite material of the present invention.

In the present invention, the Cu sintered layer is defined to be mainly composed of copper or a copper alloy. Pure copper is extremely superior in terms of thermal conductivity and is effective as a heat spreader for which thermal conductivity is important, but in some cases mechanical strength, solderability, silver brazing, heat resistance, etc. It is possible to add an alloying element in order to improve the characteristics according to the above. For the addition of the alloying element, a copper alloy powder which has been alloyed in advance may be used, or a powder obtained by mixing pure copper powder and additive element powder may be used. For example, Sn or Ni can form a solid solution in copper or a copper alloy to improve the mechanical strength. Further, when Ti is added in combination with Ni, it precipitates as a Ni and Ti compound in the copper matrix and improves mechanical strength and heat resistance. Zr also improves solder weather resistance.
Al, Si, Mn, and Mg are known to improve the adhesiveness with the resin.

Since the purpose of the sintered layer of the present invention is to dissipate heat, the above-mentioned additional element that reduces the heat dissipation is preferably 10% by weight or less. Further, the low expansion F of the present invention
The e-Ni alloy is based on the balance of 30 to 90% by weight of Ni and the balance Fe composition, and can contain an additive element substituting for Ni within the range of the austenite structure. As additive elements, it is desirable to contain Co in an amount of 30% by weight or less and Cr in an amount of 15% by weight or less alone or in combination. The additive element can be selected according to various requirements such as thermal expansion characteristics, mechanical strength, and surface oxide film forming characteristics, and is not limited to Co and Cr. For example, as an element for improving strength, Nb, Ti, Zr, W, Mo, C of 5% by weight or less is used.
As elements for improving u and hot workability, Si, Mn or 0.1% by weight or less of Ca, B, Mg can be used.

Further, in the present invention, it is defined that a sintered layer of powder containing copper or copper alloy as a main component is formed on at least one surface. However, in the case of plating on both sides, the surface condition after plating will be uneven because the acid solution is eroded at the boundary of the through hole during the plating process and the dissimilar metal is exposed. It is desirable to form sintered layers on both surfaces so that the dissimilar metals are not exposed on the surfaces.

[0017]

[Example] Fe-3 as a low expansion Fe-Ni alloy material
6 wt% Ni alloy, Fe-42 wt% Ni alloy, Fe-
29 wt% Ni-17 wt% Co alloy and Fe-42
A wt% Ni-6 wt% Cr alloy was selected, cold rolled and annealed to obtain an Fe—Ni alloy thin plate having a thickness of 0.5 mm. As shown in Fig. 2, a hole with a diameter of 1 mm is formed on this thin plate for 1 m.
Low expansion F with a plurality of perforations, with m pitches or φ3 mm holes formed by pressing at 3 mm pitch
An e-Ni alloy material was produced.

Next, the thin plate having the perforations has an average grain size of 1
Pure copper powder of 5 μm (corresponding to JIS KE21) and copper alloy of composition shown in Table 1 (particle size 150 μm or less) are added to pure water using polyvinyl alcohol as a binder to make a slurry, and various one or both sides of this material are sprayed. To form copper and copper alloy layers.
It is then dried at 80 ° C. for 2 hours and then in hydrogen for 9 hours.
Sintering was performed at 50 ° C. for 1 hour to obtain the composite material for electronic parts of the present invention. Further, a product which was dried, cold-rolled to a thickness of 0.3 mm, and then sintered at 950 ° C. for 1 hour was also manufactured. Further, the obtained sintered material was further subjected to final cold rolling to prepare a composite material for electronic parts of the present invention which was a thin plate of 0.15 mm. The materials of the present invention thus obtained are summarized in Table 1.

Further, the obtained electronic component material of the present invention has a structure having a Cu sintered layer shown in FIG.
This is a structure having the Cu sintered layer shown in (b) on one side. Further, the material of the present invention has a sintered state (sintered material) and a state further cold-rolled thereafter (cold rolled material). Further, both the sintered material and the cold-rolled material include a material obtained by performing cold rolling after drying and then performing heat sintering (rolling-sintering). In addition, as a comparative example, a composite material in which a sintered layer was similarly formed using a material in which no perforation was formed by pressing the above-described low expansion Fe-Ni alloy was obtained. Regarding these composite materials, the thermal conductivity in the plate thickness direction was measured, and the thermal expansion (α _{30-300 ° C} ) was also measured. These results are shown in Table 1.
Are shown together. As a comparative example, Table 1 also shows the characteristics of Cu-W which is a typical heat spreader or heat sink material.

[0020]

[Table 1]

As shown in Table 1, the composite material for electronic parts of the present invention has excellent thermal conductivity in the plate thickness direction,
It can be seen that the material has excellent heat dissipation. Also,
The material of the present invention can be significantly reduced in cost as compared with the current heat spreader or heat sink materials such as Cu-W and Mo, and can also be expected to have great effects in terms of size reduction, thinness, and weight reduction.

[0022]

EFFECTS OF THE INVENTION The composite material for electronic parts of the present invention has low cost by forming perforations in a low expansion Fe-Ni alloy and forming a sintered layer mainly composed of copper or copper alloy in this material. In addition, the material is excellent in heat dissipation, especially in the thickness direction. Therefore, it is extremely effective as a material for a heat spreader or a heat sink for a semiconductor element, and can be an effective electronic component material that solves the problem of heat dissipation due to higher speed and higher power consumption of the semiconductor element.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a composite material of the present invention.

FIG. 2 is a diagram showing an example of an Fe—Ni-based alloy thin plate having a large number of perforations.

FIG. 3 is a diagram showing a structure example of an LSI package using a heat sink.

[Explanation of symbols]

1 heat sink, 2 LSI chip, 3 Cu wiring,
4 Polyiside film, 5 Solder balls, 6 Fe-
Ni-based alloy thin plate, 7 perforated, 8 Cu sintered layer

Claims (6)

[Claims] 1. An electronic component, comprising a sintered layer of a powder mainly composed of copper or copper alloy in at least one surface of a Fe—Ni alloy thin plate having a plurality of perforations and in the perforations. Composite material. 2. The electronic component, wherein the sintered layer fills the inside of the perforations and covers the perforated portions and non-perforated portions of the Fe—Ni alloy to form a flat surface. For composite materials. 3. An electronic device characterized in that a powder containing copper or a copper alloy as a main component is applied to at least one surface of a Fe—Ni-based alloy thin plate having a plurality of perforations and the perforations, followed by heating and sintering. Manufacturing method of composite material for parts. 4. The method for producing a composite material for electronic parts according to claim 3, wherein rolling is performed after the heating and sintering. 5. A powder layer containing copper or a copper alloy as a main component is formed on at least one surface of the Fe—Ni alloy thin plate having a plurality of perforations and in the perforations, followed by rolling and then heat sintering. A method of manufacturing a composite material for electronic parts, comprising: 6. The method for producing a composite material for electronic parts according to claim 5, wherein rolling is performed after the heating and sintering.