JPH09312364A - Composite material for electronic component and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure high heat conductivity in a stacking direction and to provide low thermal expansibility. SOLUTION: In the composite material, the high heat conductive layers 3 of copper or copper alloy and the low thermal expansion layers 1 of Fe-Ni system alloy are alternately stacked desirably for more than 10 layers. Plural through holes 2 are formed in the low thermal expansion layers 1 in a thickness direction, copper or copper alloy is filled in the through holes 2 and a diffused layer having the thickness of not less than 5% of that of the low thermal expansion layer 1 is formed on the stacking interface of the low thermal expansion layer 1. Then, it is used for a heat sink or a heat spreader. In the composite material, the thin sheets of copper or copper alloy and the thin sheets of Fe-Ni system alloy, in which the plural through holes are formed, are alternately stacked, pressure is reduced lower than 10<-3> Torr, pressurization is executed not less than 50MPa, at 700-1050 deg.C, a junction processing is executed and the material is made into a prescribed board thickness by rolling.

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 or a heat sink for a semiconductor device, and more particularly to a composite material for electronic parts having improved heat dissipation in the plate thickness direction and a method for manufacturing 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 rray) is applied, and heat generated from the Si chip is dissipated via a heat transfer substrate (heat spreader) between the silicon chip and the Al heat sink fin. Recently, BGA (Ball Gri) using solder balls as terminals is used.
A package called dArray) is also used. On the other hand, in recent LSIs, dissipation of heat generated from a silicon chip has become a very important problem due to the increase in speed and power consumption, and especially in the microcomputer or logic A
SIC (Application Specific)
In LSIs for IC) and the like, the heat spreader is brought into contact with a silicon chip to promote heat dissipation. Since such a heat transfer substrate (heat spreader) is in contact with the silicon chip, its thermal expansion must be matched with that of the silicon chip, and the coefficient of thermal expansion is generally 4 to 11 × 10 -6 powers / ° C.
It is said that some degree is desirable.

In order to satisfy these characteristics, conventionally, a heat spreader made of Cu-W or Mo having a thickness of 0.5 to 1 mm and a size of about 30 mm square has been used. 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.

Incidentally, in a conventional LSI package of a type using a lead frame, 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, a thermal expansion coefficient is used. Since it is larger than the silicon chip, internal stress at the interface between the silicon chip and the lead frame becomes a problem, and cracks may occur in the silicon 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. An invention relating to the manufacturing method is filed as Japanese Patent Application No. 7-59708.

However, a PG that does not use a lead frame
For packages such as A and BGA, simply use copper and Fe-Ni.
In a structure in which the system alloy is delaminated, it cannot be applied as a heat spreader due to poor heat conduction in the plate thickness direction, in other words, the stacking direction. New heat spreaders that can be made thinner and lighter are needed. In addition, the package of the type that does not use the lead frame is
GA and BGA, CSP (Chip Size P
is becoming more practical,
Great demand is expected in the future.

[0006]

As a low expansion material to replace Cu-W and Mo plates, Japanese Patent Publication No. 7-80272 discloses a low thermal expansion metal plate having through holes in the thickness direction on one surface of a copper or copper alloy plate. Alternatively, there has been proposed a lead frame material or a heat spreader composite material in which both surfaces are pressed and integrated to expose copper or a copper alloy from a through hole.
In this method, the copper or copper alloy with which the through holes are filled can ensure high thermal conductivity in the stacking direction, which cannot be obtained with a simple stack, and is effective as a heat spreader.

However, according to the study by the present inventors, the composite material described in Japanese Patent Publication No. 7-80272 is mechanically laminated by cold rolling, and diffusion annealing is applied after lamination. However, since the diffusion layer formed between the layers is thin and some unbonded portions may occur, it cannot be said that it is necessarily superior in terms of reliability as a joining component with a semiconductor. . In view of the above-mentioned problems, an object of the present invention is to ensure a high thermal conductivity in the stacking direction, and a composite material for electronic components that can be used as a highly reliable heat spreader that also has a low thermal expansion property and the same. It is to provide a manufacturing method.

[0008]

DISCLOSURE OF THE INVENTION The inventor of the present invention, when the Fe--Ni alloy having a plurality of through holes as described above and copper or copper alloy are mechanically pressure-bonded to each other, the occurrence of a peeled portion becomes a problem. To prevent this, a hot isostatic press was applied to the formation of the composite layer to form a sufficient diffusion layer at the time of composite, and to prevent the occurrence of peeling parts and to form a highly reliable integrated product. The present invention has been accomplished by discovering that a composite material can be obtained.

That is, the present invention relates to a composite material for electronic parts, which is excellent in heat dissipation, in which a high thermal conductive layer of copper or a copper alloy and a low thermal expansion layer of a Fe--Ni alloy are alternately laminated,
A plurality of through holes are formed in the low thermal expansion layer in the thickness direction, the through holes are filled with copper or a copper alloy continuous to the high thermal conductive layer, and the low thermal expansion layer has the low thermal expansion layer. It is a composite material for electronic parts in which a diffusion layer having a thickness of 5% or more of the thickness of the expansion layer is formed.

The above-mentioned composite material for electronic parts of the present invention is
Copper or copper alloy sheet and Fe with multiple through holes
-Ni-based alloy thin plates are alternately laminated and filled in a can body, and then the pressure is reduced to less than 10 -3 torr and then sealed, and then 5 in a temperature range of 700 to 1050 ° C.
It is obtained by a manufacturing method of the present invention in which a joining process is performed by applying a pressure of 0 MPa or more, copper or a copper alloy is filled in the through holes and diffusion joining is performed, and then hot rolling and cold rolling are performed to obtain a predetermined plate thickness. be able to.

The composite material for electronic parts of the present invention obtained by this method has a structure in which the high thermal conductive layers are bonded to each other in the middle of the through-hole formed in the low thermal expansion layer, and a desirable bonding is a structure in which the bonding portion is diffusion bonded. Is. The preferred overall structure of the composite material in the present invention is to stack a continuous high thermal conductive layer of copper or a copper alloy on the outermost layer, or Fe- on the outermost layer.
A continuous low thermal expansion layer of a Ni-based alloy is laminated. Also, more preferably, a thin plate of copper or copper alloy,
A laminated structure is formed by alternately laminating 10 or more Fe—Ni based alloy thin plates having a plurality of through holes.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION One of the features of the present invention is to provide an Fe-Ni alloy having a plurality of through holes and copper or a copper alloy,
A diffusion layer having a thickness of 5% or more of the thickness of the low thermal expansion layer, which cannot be obtained by a conventional method of pressure bonding by cold rolling and then diffusion annealing, is obtained. Is. As a result, it has excellent adhesiveness required as a composite material for a heat spreader or a heat sink of a semiconductor element or the like, and the reliability can be greatly improved.

In the present invention, the through holes are filled with continuous copper or copper alloy in the high thermal conductive layer, and it is particularly desirable that the high thermal conductive layer (for example, Cu or Cu alloy) is structurally characterized. That is, the high thermal conductive layers are projected to both sides of the through hole opened in the low thermal expansion layer, and the high thermal conductive layers are in contact with each other in the middle of the through hole. In this state, it suffices that the heat is in contact with the high thermal conductive layer so as to escape.
It goes without saying that it is good that the contacting is sufficient. In the present invention, these states are collectively referred to as "bonding".

In reality, as shown in FIG. 5A, it is difficult in manufacturing to completely communicate the through hole 2 formed in the low thermal expansion layer 1 with another low thermal expansion layer 1. The position is not a little and there is a deviation. In the present invention, it suffices that the high thermal conductive layers are joined to each other, and the configuration shown in FIG. 5A is sufficient. In addition, in order to further improve the thermal conductivity, FIG.
It is desirable that the through holes communicate with each other as shown in (b). In addition, it is preferable that the joint between the high thermal conductive layers is not clearly formed by diffusion bonding or the like because the thermal conductivity is improved. If the layer of the Fe-Ni-based alloy that secures the low thermal expansion characteristics is a continuous layer having no through holes, heat transfer across the Fe-Ni-based alloy layer is significantly hindered. In the present invention, Fe-
Fe so as not to hinder the heat conduction across the Ni-based alloy layer
By providing the through-hole in the -Ni-based alloy layer, the high thermal conductivity layer of copper or copper alloy is continuous without being interrupted by the Fe-Ni-based alloy layer through the through-hole.
This makes it possible to ensure heat transfer across the Fe-Ni alloy layer.

Another important feature of the present invention is that the high thermal conductivity layer of copper or copper alloy and the low thermal expansion layer of Fe-Ni alloy have a difference in thermal expansion coefficient, preferably in a multilayer structure of 10 layers or more. It is to suppress deformation such as warpage. When bonded to a semiconductor element, there is a risk of peeling if warpage or the like occurs. If peeled off, heat cannot be radiated from the semiconductor element, which not only deteriorates the performance of the semiconductor element but also causes damage to the semiconductor. Preferably, a continuous high thermal conductive layer of copper or copper alloy is laminated on either one or both surfaces of the outermost layer, or Fe-Ni-based alloy is continuous on either one or both surfaces of the outermost layer, That is, a low thermal expansion layer having no through holes is laminated.

By forming a continuous high thermal conductivity layer of copper or copper alloy having no through holes or a continuous low thermal expansion layer of Fe-Ni alloy in the outermost layer, non-uniformity of the surface is eliminated during plating treatment. Therefore, good plating property can be obtained. Whether the outermost layer is a high thermal conductive layer or a low thermal expansion layer can be arbitrarily selected depending on the required characteristics of the element to be radiated. For example, the outermost layer may be a low thermal expansion layer when the low thermal expansion property of the joint surface is particularly required, and may be a high thermal expansion layer when the high thermal conductivity property is particularly required.

A high thermal conductive layer of copper or a copper alloy of the present invention and a low thermal expansion layer of a Fe--Ni alloy having a plurality of through holes are laminated, and the outermost layer is a continuous copper or copper alloy having no through holes. FIG. 1 shows the basic structure of a composite material in which a high thermal conductive layer or a continuous low thermal expansion layer of an Fe—Ni alloy is formed. FIG. 1 shows a portion where a low thermal expansion layer 1 and a high thermal conductivity layer 3 of a composite material having a multilayer structure are joined. As shown in FIG. 1, the high thermal conductive layers 3 on both sides of the low thermal expansion layer 1 are continuous by the copper or copper alloy with which the through holes 2 are filled. By doing so, F
This ensures heat transfer across the low thermal expansion layer of the e-Ni alloy. It should be noted that FIG. 1 shows an example of the basic constituent parts of the composite material of the present invention. Further, as shown in FIG. 2, in the present invention, as the outermost layer 4 of the composite material 5, a continuous high heat conductive material of copper or a copper alloy having no through holes or a continuous low heat resistance of an Fe-Ni-based alloy having no through holes. It is possible to place the expandable material on one or both sides.

The diffusion layer specified in the present invention was quantified as follows. FIG. 4 is an optical microscope photograph observed at 400 times after etching the joint interface between the high thermal conductivity layer and the low thermal expansion layer of the present invention with a nital solution. As shown in the photograph of the metal structure, Cu diffuses to the low thermal expansion layer side to form a Cu diffusion layer. The thickness D of the diffusion layer is shown in FIG.
As shown in, it can be easily quantified with a 400 × optical microscope.

In the present invention, in order to obtain a sufficiently thick diffusion layer of 10 μm or more, 700 to 1050 ° C.
A pressure of 50 MPa or more is applied in the temperature range of.
When a high pressure of 50 MPa or more is applied, 700 to
In the temperature range of 1050 ° C, the thickness of the low thermal expansion layer is 5
It is possible to form a diffusion layer having a thickness of at least%, which is significantly thicker than that formed by the conventional pressure bonding and annealing by cold rolling. In addition, this method has an advantage that a diffusion layer can be formed in a multi-layer laminate by a single treatment. It is preferable that the pressure is as high as possible.
MPa or less is realistic, preferably 80 to 150M
Pa range. In the present invention, at a temperature of 700 ° C. or less, diffusion becomes insufficient and sufficient bonding strength cannot be obtained. At a temperature of 1050 ° C. or more, the surface oxidation of copper or a copper alloy becomes remarkable, and a sufficient bonding strength cannot be obtained, and the copper or the copper alloy may be dissolved, which is not preferable. Therefore, in the present invention, 700 to 1050
Specified in the temperature range of ° C.

Further, in the present invention, prior to the above-mentioned joining treatment, after the can body is filled with 10 to the third power To.
A step of sealing after applying a reduced pressure rather than rr is added. According to the present invention, when gas remains in the through-hole formed in the Fe-Ni alloy material, the through-hole cannot be sufficiently filled with copper or copper alloy, or the copper or the copper filled from both sides of the through-hole is not filled. Since the alloy cannot bond enough to dissipate heat, degassing is performed. Further, in the present invention, after the above-mentioned joining treatment,
It is finished to a predetermined plate thickness by rolling. In the present invention, the joining process is performed under high pressure, but with this alone,
In some cases, the through holes may not be sufficiently filled with copper or copper alloy. Bending often occurs in the materials subjected to the joining process. Therefore, in the present invention, a rolling process is applied after the joining process. In this way, the high thermal conductive layers flow from both sides into the through holes formed in the low thermal expansion layer by applying high pressure, and the high thermal conductive layers are joined together in the middle of the through holes.

In the present invention, the low thermal expansion layer of the Fe-Ni alloy is provided for the first purpose of reducing the thermal expansion of the composite material of the present invention. It is preferable that the composite material has a coefficient of thermal expansion of 3 so as to approximate the coefficient of thermal expansion of the semiconductor device.
It is desirable to arrange so that the coefficient of thermal expansion at 0 ° C. to 300 ° C. is in the range of 4 to 11 × 10 −6 / ° C. Therefore, the Fe-Ni alloy preferably has a Ni content of 25 to 60% by weight, and one or two of Fe and Co as other main elements. Fe-Ni alloys specifically used include Fe-
42% Ni alloy, so-called Invar alloy of Fe-36% Ni alloy, so-called Super Invar alloy of Fe-31% Ni-5% Co alloy, Fe-29% Ni-17% Co
It is possible to use an alloy or the like having 30 to 60% of Ni and the balance of Fe or a material in which Ni is partially replaced with Co as a basic element.

It is also possible to include other additional elements. For Cr, 15% by weight or less, and elements of the 4A, 5A, and 6A groups according to various requirements such as thermal expansion characteristics and mechanical strength. It can be added as long as an austenite structure that does not impair the low thermal expansion characteristics can be maintained. For example,
Cr, which is effective for forming an oxide film, is 15% by weight or less, and 5% by weight or less of Nb, T as an element for improving strength.
i, Zr, W, Mo, Cu, and when hot workability is applied, Si, Mn of 5 wt% or less or Ca, B of 0.1 wt% or less as an element for improving hot workability, Mg
Can be used.

In the present invention, the high thermal conductive layer is defined as copper or copper alloy. Pure copper is extremely excellent in terms of thermal conductivity and is effective for heat sinks or heat spreaders that emphasize thermal conductivity, but in some cases mechanical strength, solderability, silver brazing, heat resistance, etc. It is possible to add an alloying element for the purpose of improving the characteristics. For example, Sn or Ni can form a solid solution in copper or a copper alloy to improve the mechanical strength. Also, Ti is N
When combined with i, Ni and Ti are added to the copper matrix.
It precipitates as a compound with and improves the mechanical strength and heat resistance. Zr also improves solder weather resistance. Al,
Si, Mn, and Mg are known to improve the adhesion with the resin. Since the copper or copper alloy layer of the present invention is for the purpose of imparting heat dissipation properties, the above-mentioned additional element that reduces the heat dissipation properties is preferably 10% by weight or less in the copper alloy.

[0024]

The present invention will be described below with reference to examples. As a material for the low thermal expansion layer, Fe-42% Ni alloy, Fe-3
6% Ni alloy, Fe-31% Ni-5% Co alloy and Fe-29% Ni-17% Co alloy are selected, cold rolling and annealing are repeated, and a thin plate of Fe-Ni alloy having a thickness of 0.3 mm is selected. Got By etching this Fe-Ni alloy, the entire surface of the thin plate is φ0.8 mm, 1 m.
Through holes of m pitch were formed to obtain a low thermal expansion layer material 5 shown in FIG. 3 (b). Pure copper (oxygen-free copper), Cu-2.4% Fe-0.07% P-, as a material for the high thermal conductive layer.
0.12% Zn alloy (referred to as Cu alloy A) and Cu-
2.0% Sn-0.2% Ni-0.04% P-0.15
% Zn alloy (referred to as Cu alloy B) was selected to obtain a thin plate having a thickness of 1 mm. Each of these thin plates was slit into a width of 120 mm, and then cut into a length of 800 mm with a standard length cutting machine to obtain a high thermal conductive layer material 6 shown in FIG. 3 (a). The composition of the Cu alloy is% by weight.

Next, by combining these sheets as shown in Table 1, a low thermal expansion layer of Fe--Ni alloy is sandwiched by a high thermal conductive layer of copper or copper alloy in a case of S15C material having a thickness of 5 mm. By alternately laminating the layers, 6 layers of low thermal expansion layers and 7 layers of high thermal conduction layers were obtained to obtain a laminated body in which the outermost layers were continuous high thermal conduction layers. (Layered structure A) As another example, a thin plate which is the same material as the low thermal expansion layer constituting the laminated body and does not form a through hole is arranged further outside the layered structure A so that the outermost layer penetrates. A laminate having a low thermal expansion layer having no holes was obtained. (Layered structure B) Next, the case of S15C material is set to 10 minus 3 torr Torr.
The pressure was reduced more than that and then sealed by welding. The S15C case (hereinafter referred to as a can material) having the laminated body after degassing was joined and integrated by hot isostatic pressing under the conditions of the temperature shown in Table 1 and 1000 atm. S1 on the upper and lower surfaces of the can material after this hot isostatic pressing
The laminate obtained by removing the 5C case material by grinding was cold-rolled to obtain a plate having a thickness of 1.5 mm.

Next, a sample for measuring thermal conductivity and a sample for measuring thermal expansion were manufactured from this plate, and the thermal conductivity and the coefficient of thermal expansion were measured. The thermal conductivity was measured by the laser flash method, and the coefficient of thermal expansion was measured in the temperature range of 30 to _{300 ° C} , α 30 to _{300 ° C.} Further, as shown in FIG. 4, in each sample, the vicinity of the boundary between copper or the copper alloy and the Fe—Ni-based alloy was photographed with a 400 × optical microscope, and the thickness of the diffusion layer was measured.

[0027]

[Table 1]

As shown in Table 1, in the composite material for electronic parts of the present invention, the thickness of the diffusion layer is as large as 5% or more of the thickness of the low thermal expansion layer, and the adhesion reliability is excellent, and in the plate thickness direction. It can be seen that the heat dissipation is excellent. That is, 100 (W / m ·
It is possible to obtain a high thermal conductivity characteristic of about K or more) and a low thermal expansion characteristic of 7 (× 10 −6 power / ° C.) or less. In addition, as a comparative example, the same material for high thermal conductivity layer as that of the above-described example and the material for low thermal expansion layer having through holes are used one by one, and cold rolling is performed by applying 60% reduction. After that, diffusion annealing was carried out at 900 ° C. for 3 hours after rolling, but with partial peeling,
Only a diffusion layer having a thickness of about 2% of the thickness of the low thermal expansion layer was observed at the joint.

[0029]

According to the present invention, it becomes possible to obtain a composite material for electronic parts having a thick diffusion layer. Therefore, as compared with the conventional cold pressure bonding-diffusion annealing method, the bonding is performed by applying high pressure in the hot state, so that the adhesion reliability is remarkably improved and the reliability of the parts is greatly improved. . Further, according to the present invention, it is possible to have a multi-layer structure, a more dense composite structure, and it is possible to prevent deformation such as warpage due to a difference in thermal expansion when used as a heat spreader.

[Brief description of drawings]

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

FIG. 2 is a conceptual diagram showing a preferred example of the outermost layer portion of the composite material of the present invention.

FIG. 3 is a diagram illustrating a raw material of the composite material of the present invention.

FIG. 4 is a metal microstructure photograph showing an example of a diffusion layer formed at the interface between the high thermal conductive layer and the low thermal expansion layer of the composite material of the present invention.

FIG. 5 is an enlarged view of a through hole portion of the present invention.

[Explanation of symbols]

1 low thermal expansion layer, 2 through holes, 3 high thermal expansion layer, 4 outermost layer, 5 low thermal expansion layer material, 6 high thermal conductivity layer material
7 composite materials

Claims (9)

[Claims] 1. A high thermal conductive layer of copper or a copper alloy, and Fe--
A composite material for electronic parts, in which low thermal expansion layers of Ni-based alloy are alternately laminated, wherein a plurality of through holes are formed in the low thermal expansion layer in a thickness direction, and the high thermal conductive layer is continuous with the through holes. And a copper alloy is filled, and a diffusion layer having a thickness of 5% or more of the thickness of the low thermal expansion layer is formed at a laminated interface of the low thermal expansion layer. For composite materials. 2. A high thermal conductive layer of copper or a copper alloy, and Fe--
A composite material for electronic parts, in which low thermal expansion layers of a Ni-based alloy are alternately laminated, wherein a plurality of through holes are formed in the low thermal expansion layer in the thickness direction, and high thermal conductivity layers are provided in the middle of the through holes. And a diffusion layer having a thickness of 5% or more of the thickness of the low thermal expansion layer is formed at the laminated interface of the low thermal expansion layer. 3. A continuous high thermal conductive layer of copper or copper alloy is formed as the outermost layer.
Alternatively, the composite material for electronic components according to 2. 4. The composite material for electronic parts according to claim 1, wherein a continuous low thermal expansion layer of an Fe—Ni alloy is formed as the outermost layer. 5. The composite material for electronic parts according to claim 1, which has a layered structure of 10 or more layers. 6. A copper or copper alloy thin plate and a Fe—Ni alloy thin plate having a plurality of through holes are alternately laminated and filled in a can body, and then the pressure is reduced to less than 10 −3 torr. Sealing, then pressurizing to 50 MPa or more in a temperature range of 700 to 1050 ° C. to perform a joining process, filling the inside of the through hole with copper or a copper alloy and joining, and then rolling to a predetermined plate thickness. A method for producing a composite material for electronic parts, comprising: 7. The method for producing a composite material for electronic parts according to claim 6, wherein a continuous high thermal conductive layer of copper or a copper alloy is laminated on the outermost layer. 8. The method for producing a composite material for electronic parts according to claim 6, wherein a continuous low thermal expansion layer of a Fe—Ni alloy is laminated on the outermost layer. 9. The thin plate of copper or copper alloy and the Fe—Ni alloy thin plate having a plurality of through holes are alternately laminated in 10 layers or more, according to claim 6. Manufacturing method of composite material for electronic parts.