JP3462308B2 - Manufacturing method of heat conductive composite material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a heat conductive composite material for efficiently dissipating heat generated by a semiconductor chip to the outside, such as a heat dissipation board for mounting a power semiconductor chip. The thermal expansion coefficient and the thermal conductivity are arbitrarily changed so that the matching of the thermal expansion coefficient with the material and good thermal conductivity can both be achieved. In obtaining a three-layer material or a further multilayer material in which the high-thermal-conductivity metal is exposed on the surface of the low-thermal-expansion metal plate from the through-hole by press-contacting the low-expansion metal plate, the low-heat-expansion metal plate and the high-heat-conduction metal plate are joined at a predetermined temperature. By performing hot pressing that simultaneously performs plastic deformation into the required shape, high joint strength can be obtained regardless of the plate thickness, and since shape processing is performed at the same time, high-quality heat conductive composite material with good mass productivity It relates to a method for manufacturing.

[0002]

2. Description of the Related Art LSIs and ULSs for large computers
In I, the degree of integration is high and the calculation speed is high, and the amount of heat generated by the increase in power consumption during operation is extremely large.
It is also known that the power semiconductor package also has a very large amount of heat generation. Along with this, the design of semiconductor packages also takes heat dissipation into consideration, so that the board on which the chip is mounted also requires heat dissipation, and the board material is required to have high thermal conductivity. Is required to have a thermal expansion coefficient close to that of the chip and high thermal conductivity.

Various structures have been proposed as conventional semiconductor packages. For example, there is a structure in which a radiation fin is attached to a substrate, and a clad plate or C is used to secure heat radiation.
Composite materials for heat dissipation substrates such as u-Mo or Cu-W alloys (Japanese Patent Laid-Open Nos. 59-141247 and 62-29).
No. 4147) has been proposed. Although the above-mentioned composite material satisfies both the thermal expansion coefficient and the thermal conductivity in terms of practical use, it is heavy and brittle because of high density of Mo, W, etc. Molding has to be performed by plastic working, resulting in high processing cost and poor yield.

Copper alloys for lead frames, which are widely used in resin-sealed semiconductor packages, have excellent thermal conductivity but low mechanical strength, and have a poor thermal expansion coefficient matching with the chip. N having a low coefficient of thermal expansion, such as a 42% Ni-Fe alloy, whose thermal expansion coefficient is consistent with
Since the i-Fe alloy has a poor thermal conductivity, it has not been able to obtain heat dissipation enough to meet the current requirements.

Therefore, in order to solve the above-mentioned problem of the matching of the thermal expansion coefficient and / or the thermal conductivity in the semiconductor package, the applicant has a low thermal expansion metal plate having a required through hole in the thickness direction in the high thermal conductivity metal plate. And the high thermal conductive metal foil is pressure-welded to both surfaces of the core material in which the high thermal conductive metal is exposed on the surface of the low thermal expansion metal plate from the through hole, and the thickness ratio and the through hole area ratio of these metal plates are appropriately selected. As a result, the coefficient of thermal expansion and thermal conductivity are variable, uniform heat reception is achieved, and the heat diffusion effect is improved. A heat conductive composite material has been proposed (Japanese Patent Laid-Open No. 3-227621).

In order to obtain the above-mentioned heat-conductive composite material, first, punching with a press is performed to form a number of small holes into a mesh shape, and a coil of low thermal expansion metal such as a Kovar plate wound after annealing is used to form a coil. When rewinding a coil of a high thermal conductive metal plate such as a copper plate, it is rewound from above and below, and after cold or warm rolling and joining with a large diameter roll and diffusion annealing to obtain a core material, the core material is further It is manufactured by stacking high heat conductive metal foils of Cu, Al, etc. unwound from above and below, press-bonding them with a rolling roll cold or warm, and diffusion annealing.

At the time of manufacturing, Cu is added to the above core material,
High heat conductive metal foils such as Al are stacked and cold pressed, but if the reduction force is increased to increase the bonding strength, the exposed surface of the high heat conductive metal such as Cu or Al on the surface of the core material will be round or oval. It becomes a long elliptical shape, and a void is created between the through-hole and the high thermal conductive metal to deteriorate the filling property, and the surface area ratio between the selected high thermal conductive metal and low thermal expansion metal is changed to change the thermal expansion coefficient and / or the thermal conductivity. There is a problem that the coefficient fluctuates and the coefficient of thermal expansion becomes anisotropic.

[0008] Therefore, the Applicant, as a manufacturing method for increasing the bonding strength without greatly changing the shape of the through hole provided in the low thermal expansion metal plate by increasing the rolling force when manufacturing the heat conductive material by pressure welding, A low thermal expansion metal plate having a required through hole in the thickness direction is pressed against a heated high thermal conductivity metal plate, and high heat is applied to both surfaces of a three-layer material in which the high thermal conductivity metal is exposed on the surface of the low thermal expansion metal plate from the through hole. Proposal of a method for manufacturing by pressing a conductive metal foil
No. 75008).

[0009]

The heat-conducting material proposed above has properties such that the coefficient of thermal expansion and the coefficient of thermal conductivity can be arbitrarily changed, and the bondability with the mating material and the surface properties are excellent. However, because it is molded into various shapes such as stepped shapes and cap shapes required for semiconductor packages,
When complicated drawing, press punching, cutting and bending are performed, there is a concern that partial peeling may occur in the laminated composite material.

On the surface of the obtained three-layer core material, Cu, Al
It is conceivable to use a plating method instead of the above-mentioned pressure welding method to coat the high thermal conductivity metal foil such as the above, but when immersed in a plating bath, the high thermal conductivity metal and the low thermal expansion metal of the core material surface The plating solution may remain at the boundary, and this may vaporize during the subsequent diffusion annealing, causing plating swelling or peeling. With the plating method, large peeling of low thermal expansion metal cannot be covered,
It also leads to a decrease in thermal conductivity.

The present invention impairs the ability to arbitrarily change the thermal expansion coefficient and the thermal conductivity of the previously proposed thermal conductive composite material, the bondability with the mating material and the excellent surface properties. In other words, it is an object of the present invention to provide a heat conductive composite material which has significantly improved joint strength and which is not peeled off even when subjected to complicated press punching, cutting and bending, and a manufacturing method thereof.

[0012]

When the low thermal expansion metal plate and the high thermal conductivity metal plate are used as a required multilayer material, the inventor has variously studied for the purpose of significantly increasing the bonding strength between the pressure-bonded and laminated metal plates. As a result, in a non-oxidizing, inert gas atmosphere or vacuum, for example, a high thermal conductive metal and a low thermal expansion metal plate having a large number of through holes are heated to a predetermined temperature to be softened, and the thickness direction of the metal When pressure is applied to the joint and shape processing is performed at the same time, the high thermal conductive metal is exposed from the through hole to the surface of the low thermal expansion metal plate and integrated, and then annealed as necessary to form a diffusion layer of both metals. The filling into the through-holes is performed uniformly without impairing the hole shape, and the joining strength can be significantly improved, and there is no peeling even if complicated press punching, cutting, and bending are performed at the same time as pressure welding,
Further, they have found that a multi-layered heat conductive composite material can be obtained with good mass productivity by the same effect in joining single plates without providing through holes, and completed the present invention.

That is, the present invention is a Ni--Fe alloy
Or it is made of Ni-Co-Fe alloy and has many in the thickness direction.
Low thermal expansion metal plate with through holes of Cu, Cu alloy, A
1 and a high thermal conductive metal plate made of an Al alloy are laminated in a multi-layer, and are laminated in an inert gas atmosphere or in a vacuum.
Heat to 0 ° C to 1000 ° C , 50 to 250 in the plate thickness direction
a method for producing a thermally conductive composite material characterized by applying a pressure of kg / cm ² performs plastic deformation of the joint as well as a desired shape at the same time. In the present invention, the obtained multi-layered material is a three-layered material manufactured by the manufacturing method described below, and the three-layered materials,
Or 3 layer material and other metal material are laminated and 4 layer or 5 layer
It is also possible to manufacture various laminated structures that are required depending on the application, such as layers and more layers.

Further, the present invention is a method of manufacturing the thermally conductive composite material, the <br/> low thermal expansion metal plate provided with many through holes in the thickness direction on both sides of the high thermal conductivity metal plate is pressed against method for producing a thermally conductive composite material characterized by obtaining a three-layer material that combines high thermal conductivity metal is exposed to the low thermal expansion metal plate surface from the through-hole Te, provided with a plurality of through holes in the thickness direction combined method for producing thermally conductive composite material characterized by obtaining a three-layer material high thermal conductivity metal in the through-hole wherein the high thermal conductive metal plate on both sides of the low thermal expansion metal plate is pressed against the integrated filled To propose.

[0015]

The manufacturing method and operation of the heat conductive composite material according to the present invention will be described in detail with reference to the drawings. 1 to 3 are perspective explanatory views of respective materials before hot pressing, and respective B are longitudinal explanatory views of the heat conductive composite material after hot pressing. In the manufacturing method shown in FIG. 1, first, a low thermal expansion metal plate 1 having a predetermined thickness 1
2 is provided with a large number of through holes 3 by mechanical processing such as press punching, and low thermal expansion metal plates 1 and 2 are laminated on both sides of a high thermal conductive metal plate 4 and these are placed in a non-oxidizing, inert gas atmosphere or in a vacuum. Then, it is heated to a temperature of 400 ° C. to 1000 ° C. selected according to the types of the low thermal expansion metal plates 1 and 2 and the high thermal conductive metal plate 4, and further pressed in the plate thickness direction with a predetermined pressure selected according to the material thickness. Then, the three-layer composite material is produced by pressing and contacting, exposing the high thermal conductive metal material from the through hole 3 to the surface of the low thermal expansion metal plates 1 and 2 and integrating them.

In the above hot pressing, by giving the press die a desired use shape, it is possible to press in the plate thickness direction and perform pressure contact and plastic deformation to the required shape at the same time. By changing the pressure of the pressing device depending on the thickness of the composite material, it is possible to obtain a relatively thick product, and because the material is pressed and plastically deformed when the material softens, the adhesion strength is stable regardless of the plate thickness. Since it is different from the rolling method described above, the filling of the through holes 3 is uniformly performed on the entire material without deforming the hole shape.

Further, the high thermal conductive metal and the low thermal expansion metal are diffused at the time of hot press heating, and high bonding strength can be obtained.
Furthermore, after that, in an atmosphere of non-oxidizing and inert gas, 3
Low thermal expansion metal plates 1 and 2 and high thermal conductivity metal plate 4 of layer composite material
Temperature range above the above heating temperature selected according to the type of
For example, when annealing is performed in an atmosphere of 500 ° C. to 1050 ° C., mutual diffusion proceeds at the pressure contact interface between both materials to form a diffusion layer, and the bonding strength of the three-layer material obtained by this diffusion layer is significantly improved. No peeling occurs between the high thermal conductivity metal and the low thermal expansion metal after the complicated drawing process, press punching process, cutting process, and bending process applied to the.

In the present invention, since the high thermal conductivity metal plate is press-fitted into the through hole of the low thermal expansion metal plate by pressure welding, Cu, Cu alloy, Al, Al alloy and the like are rich in extensibility and high. It is preferable to use a material having thermal conductivity. In addition, the low thermal expansion metal plate,
Ni-Fe based alloy containing 30 to 50 wt% Ni, 2
N containing 5 to 35 wt% Ni and 4 to 20 wt% Co
An i-Co-Fe based alloy, W or the like can be used.

In the present invention, the heating temperature at the time of hot pressing is set to 400 ° C. to 1000 ° C. because the high thermal conductive metal as a filler is work-hardened at the time of pressurizing, so that it is always in a softened state and has a low thermal expansion. This is for easily filling the through holes of the metal plate. Further, the pressing force may be selected depending on the hardness and the filling depth of the filler (highly heat-conductive metal), but generally 50 to 250 kg / cm ² is desirable.

Further, a high thermal conductive metal film layer can be provided on the outermost layer of the composite material if necessary, and Cu, Cu alloy,
Materials such as Al, Al alloys, Ni, Ni alloys can be selected, and in consideration of the application and the material of the thin film layer to be deposited, the same or different material as the high thermal conductive metal plate of the core material is pressed or plated. Appropriate selection may be made such as joining. In addition, mechanical processing such as press punching and chemical processing such as etching can be adopted for the through holes provided in the plate thickness direction of the low thermal expansion metal plate, and the cross section of the through hole is circular, polygonal, etc. However, various shapes such as straight and tapered can be adopted.

In the manufacturing method shown in FIG. 2, first, a large number of through holes 6 are formed in a low-thermal-expansion metal plate 5 having a predetermined thickness by mechanical processing such as press punching, and then the low-heat-expansion metal plate 5 is predetermined on both sides. By stacking the high thermal conductive metal plates 7 and 8 having a thickness,
400 ° C which is selected according to the kind of metal material selected in non-oxidizing, inert gas atmosphere or vacuum
Heating to a temperature of up to 1000 ° C., and further pressing and pressing in the plate thickness direction at a predetermined pressure selected according to the material thickness,
When a high thermal conductive metal material is fitted into the through hole 6 of the low thermal expansion metal plate 5 to produce an integrated three-layer composite material, the press die is given a desired use shape to obtain a plate thickness. By pressing in the same direction, pressure welding and plastic deformation to the required shape can be performed simultaneously.

After that, in a non-oxidizing, inert gas atmosphere, the temperature of 500 ° C. selected according to the metal type of the three-layer composite material
When annealing is performed in an atmosphere of 1050 ° C., mutual diffusion proceeds at the pressure contact interface between both materials to form a diffusion layer, the bonding strength of the three-layer material obtained by this diffusion layer is significantly improved, and high heat treatment is performed after pressure welding and shape processing. No peeling occurs between the conductive metal and the low thermal expansion metal.

In the manufacturing method shown in FIG. 3, the high thermal conductive metal plates 11 and 12 are laminated on both surfaces of the low thermal expansion metal plate 10 in the case where the through holes are not provided in the material, and these are placed in a non-oxidizing, inert gas atmosphere. While heating in a vacuum or in vacuum to a temperature of 400 ° C to 1000 ° C selected according to the type of the selected metal material, pressing in the plate thickness direction at a predetermined pressure selected according to the material thickness, and pressing Performs plastic deformation into a shape. By changing the pressure of the pressing device depending on the thickness of the three-layer composite material, a relatively thick product can be obtained.
Since the material is pressed and plastically deformed when the material is softened, the adhesion strength is improved regardless of the plate thickness. Further, in a non-oxidizing, inert gas atmosphere, annealing treatment is performed in an atmosphere of 500 ° C. to 1050 ° C. selected according to the metal type of the three-layer composite material, and the low thermal expansion metal plate 10 and the high thermal conductive metal plates 11 and 12 are used. It is possible to form a diffusion layer at the bonding interface of (3) to significantly improve the bonding strength of the three-layer material.

According to the heat conductive composite material of the present invention, when the low thermal expansion metal plate is laminated on both surfaces of the high heat conductive metal plate, through holes in the thickness direction are formed on the entire surface of the low heat expansion metal plate or partially in the thickness direction, The thickness of the core metal plate, for example, by arranging in a pattern, for example, changing the hole size, shape, arrangement pattern, etc. of the through holes, and making cuts or through holes in the thickness direction in consideration of deformation during rolling. The ratio and / or the means for selecting the surface area ratio of the high thermal conductive metal and the low thermal expansion metal exposed on the surface of the low thermal expansion metal plate can be selected and combined to suit the whole or part of the material according to the use and purpose. You can set the thermal expansion coefficient and thermal conductivity,
For example, required metals, ceramics, semiconductors such as Si,
It is possible to obtain a material, such as plastics, having a matching thermal expansion coefficient with that of the mating material and having a required thermal conductivity.

[0025]

Example 1 A Kovar plate (29Ni-17Co-) having a plate thickness of 0.35 mm
Fe alloy) with 0.8 mm hole diameter and 1.3 mm hole spacing
Made a large number of perforations with a plate thickness of 0.75 mm, 40 mm x 4
Plate thickness 0.35 with through holes on both sides of 0 mm Cu plate
mm, 40 mm × 40 mm Kovar plates are laminated facing each other, heated to 1000 ° C. in a nitrogen gas atmosphere, and pressure is 15
Hot press molding at 0 kg / cm ² and plate thickness 1.0 m
m, an inner diameter of 20 mm, a depth of 0.3 mm, and a brim outer diameter of 30 mm, a cap-shaped three-layer material sample was obtained. Furthermore, the obtained three-layer material sample was annealed in a hydrogen atmosphere at 1000 ° C. for 15 minutes, and a cap material without cracking or peeling could be manufactured. The exposed Cu surface of the main surface of the obtained three-layer material was substantially circular with little deformation, and the hole spacing did not change.

The average thermal expansion coefficient of the Kovar plate at 30 to 200 ° C. is 5.2 × 10 ^-6 / ° C.,
The average thermal expansion coefficient of the Cu plate at 30 to 200 ° C is 1
It is 7.2 × 10 ^-6 / ° C, the thermal conductivity of the obtained three-layer material in the thickness direction is 160 W / m · K, and the thermal expansion coefficient of each main surface is 8 × 10 ^-6 / ° C. there were. Further, as a comparative example, when a sample of a cap-shaped three-layer material was press-molded under exactly the same material conditions except that it was not heated at the time of pressure welding, cracking or peeling occurred in the portion where the vicinity of the through hole was narrowed and stretched.

Example 2 Kovar plate (29Ni-17Co-F) having a plate thickness of 0.5 mm
(e-alloy) with a large number of holes each having a hole diameter of 0.8 mm and a hole interval of 1.3 mm, and a plate thickness of 0.5 mm, 40 mm × 40 m
m Kovar plate on both sides, 1.0 mm thick, 40 mm x
40 mm Cu plates are laminated facing each other, heated to 1000 ° C. in a nitrogen gas atmosphere, and hot-press molded at a pressure of 200 kg / cm ² to obtain a plate thickness of 1.8 mm, an inner diameter of 20 mm,
Cap-shaped 3 with a depth of 0.8 mm and an outer diameter of 30 mm
A layer material sample was obtained. A cap material without cracking or peeling could be manufactured.

As a comparative example, when a sample of a cap-shaped three-layer material was press-molded under exactly the same material conditions except that it was not heated at the time of pressure welding, cracks and swelling occurred at the bent portion.

Example 3 A Cubar plate having a plate thickness of 3.0 mm and 40 mm × 40 mm was laminated on both surfaces of a Kovar plate having a plate thickness of 2.0 mm and 40 mm × 40 mm so as to face each other, and heated to 1000 ° C. in a nitrogen gas atmosphere. Hot press molding at a pressure of 250 kg / cm ² , plate thickness 5.5 mm, inner diameter 20 mm, depth 2 mm, flange outer diameter 3
A cap-shaped three-layer material sample having a size of 0 mm was obtained. further,
The obtained three-layer material sample was stored in a hydrogen atmosphere at 1000 ° C. for 15
When the annealing treatment was performed under the condition of minutes, a cap material without cracking or peeling could be produced.

As a comparative example, when a sample of a cap-shaped three-layer material was press-molded under the same material conditions except that it was not heated at the time of pressure contact, cracking and swelling and peeling occurred in almost all parts.

[0031]

The present invention, as is apparent from the examples,
In a non-oxidizing, inert gas atmosphere or in a vacuum, a high thermal conductive metal and a low thermal expansion metal plate provided with a large number of through holes are heated to a predetermined temperature to soften it, and pressure is applied in the thickness direction of the metal. After joining and shaping at the same time, exposing the high thermal conductive metal from the through hole to the surface of the low thermal expansion metal plate and integrating it, the filling into the through hole is performed uniformly without damaging the hole shape, and the bonding strength It is possible to remarkably improve the bonding strength, and also to significantly improve the bonding strength between single plates as well. A heat conductive composite material can be obtained, and in particular, it is excellent in mass productivity because it can perform bonding and shape processing at the same time.

[Brief description of drawings]

FIG. 1A is a perspective explanatory diagram of each material before hot pressing, and each B is a longitudinal sectional explanatory diagram of a heat conductive composite material after hot pressing.

FIG. 2A is a perspective explanatory diagram of each material before hot pressing, and each B is a longitudinal sectional explanatory diagram of a heat conductive composite material after hot pressing.

FIG. 3A is a perspective explanatory diagram of each material before hot pressing, and each B is a vertical sectional explanatory diagram of the heat conductive composite material after hot pressing.

[Explanation of symbols]

1,2,5,10 low thermal expansion metal plate 3,6 through holes 4,7,8,11,12 High heat conductive metal plate

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuhiro Sadatomi 2-19-1 Minami Suita, Suita City, Osaka Prefecture Sumitomo Special Metals Co., Ltd., Suita Works (72) Masakazu Umeda 2-19 Minami Suita, Suita City, Osaka Prefecture -1 Sumitomo Special Metals Co., Ltd. in Suita Works (56) Reference JP-A-6-268115 (JP, A) JP-A-5-75008 (JP, A) JP-A-3-13331 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) B23K 20/00-20/26

Claims (3)

(57) [Claims] 1. A Ni-Fe based alloy or Ni-Co-Fe
Any of a low thermal expansion metal plate made of a system alloy and having a large number of through holes in the thickness direction and Cu, Cu alloy, Al, Al alloy
A high heat conductive metal plate composed of the above is laminated in multiple layers, heated to 400 ° C. to 1000 ° C. in an inert gas atmosphere or in a vacuum, and a pressure of 50 to 250 kg / cm ² is applied in the plate thickness direction for bonding and required. A method for manufacturing a heat-conducting composite material, which comprises simultaneously performing plastic deformation into a shape. 2. The method of claim 1, 3-layer material the low thermal expansion metal plate on both surfaces of the high thermal conductivity metal plate are integrated by exposed from the through hole is pressed against the high thermal conductivity metal to the low thermal expansion metal plate surface A method for producing a heat-conductive composite material, comprising: 3. The method of claim 1, wherein the high thermal conductive metal to obtain a three-layer material and integrated filled in the low thermal expansion metal plate the through-hole wherein the high thermal conductive metal plate on both surfaces is pressed against the And a method for producing a heat conductive composite material.