JPH03227621A - Thermally conductive composing material - Google Patents

Abstract

PURPOSE:To improve the matching properties of the subject material with materials to which the former is bonded such as chips or sealing resin in terms of coefficient of thermal expansion and also improve thermal conductivity by constituting the subject material with a core consisting of a metal plate having a low thermal expansion factor with through holes in a thickness direction formed in a single piece and a high thermal expansion metal foil layer attached to the both surfaces of the core under pressure, on the both surfaces of a high thermal expansion metal plate. CONSTITUTION:A thermally conductive composite material 10 consists of for example, a core 14 obtained by press bonding a copal plate 12 having may through holes 13 in a thickness direction onto both surfaces of a copper plate 11 and a high thermal expansion metal foil layer 16 press bonded to the both surfaces of the core 14. In addition, an exposed copper surface 15 appearing on the surface of the copal plate 12 through a through hole 13 is formed on the both surfaces of the core 14. Subsequently, the heat dissipation effect and the functioning properties of the subject material with matching materials and the coating properties of a film are enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application This invention is applicable to materials such as metals, ceramics, S
In order to achieve both good thermal conductivity and consistency in thermal expansion coefficient with other materials such as semiconductors such as i and plastics,
A low thermal expansion metal having a high thermal expansion metal plate with the required through holes in the thickness direction, which is a thermally conductive composite material whose thermal expansion coefficient and thermal conductivity can be arbitrarily changed, and which has excellent bonding properties with mating materials and surface properties. The plates are integrated, and high thermal expansion metal foils are pressed onto both sides of the core material in which the high thermal expansion metal is exposed on the surface of the low thermal expansion metal plate through the through hole, and the thickness ratio of these metal plates and the through hole area ratio are appropriately selected. This makes the coefficient of thermal expansion and thermal conductivity variable, making heat reception uniform and improving the heat diffusion effect.Thermal conductive composite has no surface micropores and has excellent adhesion to thin films such as plating and brazing materials. Regarding materials.

Background Art Integrated circuit chips (hereinafter referred to as chips) in semiconductor packages, especially LSIs and ULSIs for large computers,
The trend is toward higher integration and faster calculation speeds, and the amount of heat generated during operation is increasing due to increased power consumption.

In other words, chips have become larger in capacity and generate more heat, and if the coefficient of thermal expansion of the substrate material is significantly different from that of the chip material, such as silicon or gallium arsenide, there is a problem that the chip may peel off or crack. .

Along with this, the design of semiconductor packages has also begun to take heat dissipation into consideration, and the substrate on which the chip is mounted is also required to have heat dissipation, and the substrate material is required to have high thermal conductivity. There is.

Therefore, the substrate is required to have a coefficient of thermal expansion close to that of the chip and a high thermal conductivity. Various configurations have been proposed for conventional semiconductor pancages, and for example, configurations shown in FIGS. 9a and 9b are known.

In the case of Figure 9a, M is close to the thermal expansion coefficient of chip (1).
o material (2) and alumina material (
Kovar alloy material (4) with a thermal expansion coefficient close to that of 3) is laminated by brazing, a chip is mounted on the Mo(2) material, it is bonded to the package substrate via the Kovar alloy material (4), and a heat dissipation fin is added. There is a configuration with (5) added.

In this configuration, the alumina material (3) and the Kovar alloy material (4) have similar coefficients of thermal expansion, so there is little risk of peeling or cracking, but the material that dominates heat dissipation is the Kovar alloy material with low thermal conductivity. (4), so the radiation fin (5
), there was a problem that sufficient heat dissipation could not be obtained.

Therefore, as a material that satisfies the conflicting demands of having consistency with the coefficient of thermal expansion of the chip and having high thermal conductivity, composite materials for heat dissipation substrates such as clad plates and Cu-Mo or Cu-W alloys have been developed. Proposed.

As the clad plate for the heat dissipation board, a material made by laminating a copper plate and an invar alloy plate is used.

In other words, since copper has good thermal conductivity but a large coefficient of thermal expansion, the clad plate has an invar alloy layered and pressure welded to suppress this, so that thermal expansion in the longitudinal direction of the plate is similar to that of semiconductor elements. This is to obtain consistency. Furthermore, by adopting a sandwich structure in which invar alloy plates are laminated and pressure-welded on both sides of a copper plate, the structure prevents warping due to temperature rise.

This clad plate can be made to have almost the same coefficient of thermal expansion as the chip, but the thermal conductivity in the thickness direction is
Similar to the structure shown in FIG. 9a, since an invar alloy plate is interposed, this is not necessarily sufficient.

In addition, N has a coefficient of thermal expansion close to that of semiconductor elements.
A semiconductor element support body in which a punched metal made of i-Fe is embedded in a semiconductor element support surface made of Cu or the like has also been proposed (Japanese Patent Publication No. 58-46073).

This has a structure in which punching metal is embedded in one side, so there is a problem that warping occurs due to the bimetal effect.

Ni-F has a coefficient of thermal expansion close to that of semiconductor elements
We have also proposed a heat dissipation support for semiconductor devices in which a grid made of e is laminated so as to be embedded in a semiconductor device support made of Cu etc. (U,
S, P 3,399,332).

This is because there is a concern that gas and dust may be occluded during manufacturing and cause blistering during heating, and also because there is a Ni-Fe lattice for thermal expansion adjustment in the center of the thickness of the support such as Cu. In order to make the thermal expansion coefficient of the surface comparable to that of a lattice, C
It is necessary to reduce the thickness of u, and heat transfer is good in the thickness direction, but delamination is poor in the plane-parallel direction.

Furthermore, a heat conductive metal plate was proposed in which Cu or AI was sandwiched between a pair of Co-Ni-Fe or Ni-Fe plates with the same coefficient of thermal expansion as a heat source having multiple through holes, and the through holes were filled in. -3741)).

However, when processing the above-mentioned heat conductive metal plate, there is a concern that it may peel off, and if Ni plating is applied to the surface to enable brazing, the plated layer and copper may react and cause unevenness of the plated layer. There is a concern that gas and dust may be occluded at the interface between the plating layer and the material, causing blisters when heated.

In addition, in the above-mentioned heat conductive metal plate, the heat of the heating element is different from the case where the base is Cu and the case where the base is Co-Ni-Fe or Ni-Fe plate when viewed locally.
There is a problem that heat on -Fe and Ni-Fe tends to accumulate and is not uniformly received.

On the other hand, Cu-Mo and Cu-W alloy substrates are produced by sintering Mo and W powders, which have approximately the same coefficient of thermal expansion as the chip, to create a sintered body with a high porosity, and then impregnating it with molten copper. (Japanese Unexamined Patent Publication No. 59-141247), or by sintering Mo, W powder and copper powder (
It is a composite of Mo or W and Cu obtained by the method (Japanese Patent Application Laid-Open No. 62-294147).

When this composite substrate (6) is attached to a package, as shown in FIG. It has a structure in which a flange part (7) is attached and heat is radiated by a turning part.

Although the above-mentioned composite has a thermal expansion coefficient and thermal conductivity that meet practically satisfactory conditions, it is heavy due to the high density of Mo, W, etc., and requires mechanical molding to obtain the specified dimensions. This resulted in high processing costs and low yields.

In addition to the above-mentioned heat dissipation substrate, the lead frame also needs to match the coefficient of thermal expansion with the material to be adhered and improve the thermal conductivity at the same time.

In a resin-sealed semiconductor package as shown in Figure 10, the lead frame not only serves as a route for electrical connections to the outside of the chip, but also plays an important role as a dissipation route for the heat generated in the chip. .

That is, in a semiconductor package, a chip (84)
is placed on the island (81) formed in the center of the lead frame (8o) and fixed with brazing material, adhesive, solder, etc., and the stitching (82X inner lead part) and bonding wire (85 ), and the periphery is further sealed with resin (86).

The heat generated from the chip (84) is transferred to the island (81)
, the resin (86), and the stitches (82) to reach the lead portion (83) of the lead frame (8o) and be dissipated to the outside.

Therefore, the lead frame (8o) is desired to be made of a material with good thermal conductivity in order to dissipate the heat generated from the chip to the outside of the semiconductor package.

On the other hand, peeling of the adhesive interface between the chip (84) and the island (81) and cracks observed in the resin (86) may occur between the chip (84), the sealing resin (86), and the lead frame (86).
This occurs due to the difference in thermal expansion coefficient between the chip (84) and the resin (o).
It is essential that the thermal expansion coefficients of the lead frame (86) and the lead frame (8o) match.

As described above, node frames made of a copper alloy with good thermal conductivity have been frequently used as lead frames in plastic semiconductor packages from the viewpoint of heat dissipation.

However, for applications that require high reliability, copper alloys are
Due to the low mechanical strength, poor consistency of the curved band characteristic with the chip, and the possibility of peeling of the adhesive interface between the chip and the island, 42%N was selected due to the consistency of the coefficient of thermal expansion with the chip.
Semiconductor packages employing Ni-Fe alloys having a low coefficient of thermal expansion, such as i-Fe alloys, have also been proposed.

However, since Ni--Fe alloys have poor thermal conductivity, they do not have sufficient heat dissipation properties to meet current requirements. In addition, the difference in thermal expansion between the chip and the encapsulating resin is very large. It has been difficult to completely prevent cracks from occurring.

Furthermore, in ceramic semiconductor packages, a Ni--Fe alloy with an AI provided at the sealing position is often used in the lead frame for glass sealing. However, Ni
As mentioned above, the -Fe alloy has poor heat dissipation properties and has a problem in matching the coefficient of thermal expansion with ceramics.

Purpose of the Invention As clarified in the above-mentioned example of the heat dissipation problem in semiconductor packages, the present invention provides excellent thermal expansion coefficient matching with the thermal expansion coefficient of the bonding material such as a chip or sealing resin, and a heat conductive material. The objective is to provide a composite material whose thermal expansion coefficient and thermal conductivity can be arbitrarily selected depending on the use and purpose, such as good properties.

For example, when mounting a semiconductor chip, this invention makes the thermal expansion coefficient and thermal conductivity variable, uniformizes heat reception, improves the heat diffusion effect, and eliminates surface micropores, allowing thin films such as plating and brazing filler metal to adhere. The purpose of the present invention is to provide a thermally conductive composite material with excellent properties, as well as a composite material that can be used as a heat dissipation substrate for semiconductor packages, which has excellent processability and manufacturability during mounting, and can be provided at low cost.

Summary of the Invention As a result of various studies aimed at creating a metal material that can ensure consistency in thermal expansion coefficient and heat dissipation depending on the mating material and has excellent manufacturability, the present invention has been developed by applying a large number of metal materials in the thickness direction to a high thermal expansion metal plate. A composite material with a five-layer structure, in which a low thermal expansion metal plate having a through hole is integrally welded together, and a high thermal expansion metal foil is pressed on both sides of a core material in which a high thermal expansion metal is exposed from the through hole on the surface of the low thermal expansion metal plate. By doing so, the thermal expansion coefficient and thermal conductivity can be changed arbitrarily by appropriately selecting the thickness ratio of the metal plate of the core material and the exposed area ratio of the metal plate, and the heat reception by the high thermal expansion metal foil layer on the surface is possible. In order to make the heat more uniform and improve the heat diffusion effect, the surface has no micropores and has excellent adhesion for thin films such as plating and brazing filler metal.It also has a high thermal expansion metal plate that serves as the core material and a large number of through holes in the thickness direction. The inventors have discovered that the desired composite material can be easily produced by pressure-rolling a low thermal expansion metal plate and a high thermal expansion metal foil as the outermost layer.

That is, the present invention has a configuration in which a low thermal expansion metal plate having a large number of through holes in the thickness direction is integrated on both sides of a high thermal expansion metal plate, and the high thermal expansion metal is exposed on the surface of the low thermal expansion metal plate from the through holes. This is a thermally conductive composite material comprising a core material and high thermal expansion metal foil layers of the same type or different type as the high thermal expansion metal of the core material, which are pressed against both sides of the core material.

Furthermore, in the above configuration, the thickness ratio and l of the metal plate of the core material or the surface area ratio of the high thermal expansion metal and the low thermal expansion metal exposed on the surface of the low thermal expansion metal plate are selected, and the thermal expansion coefficient and l Alternatively, it is a thermally conductive composite material characterized by changing thermal conductivity to a required value.

Furthermore, in the above configuration, the high thermal expansion metal plate is any one of Cu, Cu alloy, Al, Al alloy, and steel, and the low thermal expansion metal plate is Mo, a Ni-Fe alloy containing 30 to 50 wt% Ni, 25-35wt%Ni and 4-2
Ni-Co-Fe alloy containing 0 wt% Co, any of W, high thermal expansion metal foil is Cu, Cu alloy, A
Thickness t1 of the high thermal expansion metal plate that is made of one of Al alloy, Ni, and Ni alloy and constitutes the core material, thickness t2 of the low thermal expansion metal plate, and thickness t3 of the high thermal expansion metal foil layer.
is a thermally conductive composite material that satisfies t1=:tt2-3t2, t3≦1/10 t2.

Furthermore, in the above configuration, Cu is provided at a predetermined position on at least one main surface of the thermally conductive composite material
, A1, Ni, and Sn.

For example, on the amphibian side of a high thermal expansion metal plate such as Cu or A1,
Ni-Fe alloy with many through holes in the thickness direction, N
A low thermal expansion metal plate such as an i-Co-Fe alloy is integrated, and the high thermal expansion metal is exposed on the surface of the low thermal expansion metal plate through the through hole, and the outermost layer is made of a high thermal expansion metal such as Cu, AI, or Ni. By press-welding foils to make composite materials and performing processes such as press molding, lamination, plating, and adhesion of brazing materials, they can be used for various purposes such as heat dissipation substrates for mounting chips such as ceramic packages and metal packages, and lead frames. A thermally conductive composite material is obtained.

Composition of the Invention This invention integrates a high thermal expansion metal plate with a low thermal expansion metal plate having a large number of through holes in the thickness direction, and exposes the high thermal expansion metal on the surface of the low thermal expansion metal plate from the through holes. It features a five-layer structure in which a high thermal expansion metal foil is pressure-bonded to the core metal plate, and the coefficient of thermal expansion can be changed arbitrarily by selecting the thickness ratio of the core metal plate, and the high thermal expansion metal of the core material has high thermal conductivity. By using metal, the thermal conductivity can be arbitrarily changed by appropriately selecting the area ratio of the exposed high thermal expansion metal to the surface of the low thermal expansion metal plate, and the material selection of the high thermal expansion metal plate and the low thermal expansion metal plate, By selecting the combination and the thickness ratio and exposed area ratio, the coefficient of thermal expansion and thermal conductivity can be set according to various uses and purposes, and a wide variety of composite materials can be provided.

In addition, the outermost high thermal expansion metal foil layer ensures uniform heat reception.
Improved heat diffusion effect, excellent bonding with mating materials,
Composite materials with excellent surface properties, no micropores, and excellent adhesion of thin films such as plating and brazing materials can be provided for various uses.

In the thermally conductive composite material according to the present invention, when a low thermal expansion metal plate is laminated on the entire surface of both sides of a high thermal expansion metal plate, through holes are arranged in the thickness direction on the entire surface or part of the low thermal expansion metal plate at required intervals and in a pattern. However, the thickness ratio and / Alternatively, by selecting and combining means such as selecting the surface area ratio of the high thermal expansion metal and the low thermal expansion metal exposed on the surface of the low thermal expansion metal plate, the thermal expansion of the entire or partial composite material can be adjusted according to the use and purpose. Composite materials whose coefficients and thermal conductivities can be set to match the thermal expansion coefficients of mating materials such as metals, ceramics, semiconductors such as Si, and plastics, and which have the required thermal conductivity. is obtained.

For example, if the coefficient of thermal expansion that matches the chip and the coefficient of thermal expansion that matches the sealing resin are different, the area occupancy factor of the high thermal expansion metal plate on the surface of the low thermal expansion metal plate where the chip is placed, or the low thermal expansion By changing the conditions such as the thickness of the metal plate and the conditions of the surface directly in contact with the sealing resin on the back side as described above, the thermal characteristics of each main surface can be approximated to the required values.

Furthermore, by selecting the material of the outermost high thermal expansion metal foil layer according to the application and the mating material, the bondability with the mating material, the strength of the thin film to be adhered, etc. can be arbitrarily selected.

In addition, in the structure of the core material in which low thermal expansion metal plates are laminated on both sides of a high thermal expansion metal plate, as a laminate of high thermal expansion metals, the high thermal expansion metal exposed to the surface from the through hole of the low thermal expansion metal plate is made of a different material. Various configurations can be taken, such as.

The difference in thermal expansion coefficient between the high thermal expansion metal plate and the low thermal expansion metal plate of the core material does not necessarily have to be large; as long as the thermal expansion coefficients are different, different metal plates can be combined depending on the application. .

The coefficient of thermal expansion of the composite material according to the present invention is determined by the volume ratio of the high thermal expansion metal plate and the low thermal expansion metal plate of the core material, that is, the thickness ratio of the laminate. It is possible to choose any value between.

For example, in order for existing chips to be unaffected by thermal strain, the average coefficient of thermal expansion α at 30°C to 200°C needs to be 3 to 8 x 10'/'C, More preferably, it is 4 to 6xlO'/''C.

In the case of the heat dissipation substrate for chip mounting, Ni-
Low thermal expansion metal plates such as Fe-based alloys and Ni-Co-Fe-based alloys, and average thermal expansion coefficients of 1 at 30°C to 200°C.
High thermal expansion metal plates such as Cu and Cu alloys exceeding 0xlO'/''C can be used in combination, and it is particularly desirable that the thermal conductivity of the high thermal expansion metal plates at 20°C is 140 W/m- or more. .

Further, it is desirable to appropriately select the area ratio of the high thermal expansion metal plate on the surface of the low thermal expansion metal plate within a range of 20 to 80%. The area ratio can be changed by appropriately selecting means such as changing the diameter, size, arrangement pitch, etc. of the through holes.

Since the high thermal expansion metal plate of the core material is filled into the through hole of the low thermal expansion metal plate by pressure welding, forging, etc., Cu, C
It is preferable to use materials with high malleability such as u-alloy, AI, A1-alloy, and steel.

In addition, the low thermal expansion metal plate includes malleable Mo, 30~
Ni-Fe alloy containing 50 wt% Ni, 25-3
Ni-C containing 5 wt% Ni, 4-20 wt% Co
An o-Fe alloy, W, etc. can be used.

Materials such as Cu, Cu alloy, Al, Al alloy, Ni, and Ni alloy can be selected for the high thermal expansion metal foil that is the outermost layer on both sides of the core material.
It is preferable to appropriately select the same material as the high thermal expansion metal plate of the core material or a different material.

The thermally conductive composite material according to the present invention is characterized by the above-mentioned five-layer structure, but depending on the application, brazing may be used to improve properties and corrosion resistance, or to improve the adhesion of Au or Ag plating. In order to achieve this, Cu, Ah Ni,
Plating, vapor deposition, ion blating, CV etc. with Sn etc.
D (chemical vapor deposit)
In addition to coating by known coating techniques such as on), solder Ag brazing material, ceramics, glass layers, etc. can be coated or deposited at desired positions.

The manufacturing method includes, for example, forming a core material by punching a large number of through holes in the thickness direction at desired positions of a low thermal expansion metal plate, and then cleaning the adhered surface by pickling or brushing. Known pressure welding, rolling or forging techniques can be used, such as cold or warm pressure welding of the plate and high thermal expansion metal plate, and if necessary, diffusion heat treatment to improve adhesion. Since the composite material is obtained by cold or warm pressure welding high thermal expansion metal foils on both sides and then subjecting it to heat treatment if necessary, it is possible to provide a composite material with stable properties even when mass-produced on an industrial scale.

In addition, after cleaning each of the five layers of materials mentioned above, the five layers of materials can be cold or warm pressure welded at the same time and further heat treated. It is necessary to select cold or warm, as well as the diameter of the press roll, the number of roll stages, and the rolling reduction rate, depending on the dimensions and arrangement pattern of through holes or cuts in the thickness direction of the plate. For example, even in cold pressure welding, the high thermal expansion metal of the core material is heated immediately before welding, and depending on the combination of materials of the five layers, thickness, and other conditions, cold or warm welding, or even inert Various atmospheres such as , non-oxidizing, and reduced pressure can also be selected as appropriate.

In order to mass-produce the thermally conductive composite material of the present invention on an industrial scale, it is most effective to carry out cold and warm pressure rolling using pressure rolls, as described above. If the thickness is relatively thick and it is obtained in the form of individual pieces of about 1 mm or more, the specified materials are laminated in a die and pressure is applied below the recrystallization temperature of each material, or the hot-pressure method is used. It is also possible to adopt a method of pressure welding and integration using a thermopressure method in which pressure is applied below the melting point temperature.

Furthermore, on both sides of the core material mentioned above, 2 to 5 layers of Cu, Ni etc.
After applying thick plating in Step 2, a heat-conductive composite material having a five-layer structure having a high thermal expansion metal foil layer as the outermost layer can be manufactured by performing a known homogenization heat treatment, further rolling, and diffusion annealing.

Furthermore, the shape and arrangement of the high thermal expansion metal exposed on the surface of the low thermal expansion metal plate in the composite material of the present invention can take various forms depending on the purpose or manufacturing method as described above.

For example, in order to make the mechanical strength uniform in the width direction of the material, hole patterns with the same size and shape are arranged so that they are not repeated, or the through holes in the core material after pressure welding and rolling are tilted so that they do not coincide with the thickness direction of the material. It is desirable that the holes be tapered so that the hole sizes are different on the front and back sides, and that adjacent holes be arranged so that they have a combination of large and small hole sizes.

In addition, narrower through-hole intervals are advantageous in reducing product variations, and are usually 3 mm or less, preferably 1 mm.
It is not more than 0.5 mm, more preferably not more than 0.5 mm.

In addition, in addition to mechanical processing such as press punching, chemical processing such as etching can be used to form through holes in the thickness direction of low thermal expansion metal plates. Various shapes such as a straight or tapered surface can be adopted, and when the surface is tapered, it can be easily press-fitted into the through hole and the bonding strength can be increased.

Further, the through holes in the thickness direction of the low thermal expansion metal plate may be the required through holes filled with the high thermal expansion metal plate after pressure welding and rolling. Various selections can be made to achieve the above-mentioned through-hole arrangement by penetrating in the desired direction or by making a cut immediately before penetration, or by changing the direction of the cut or the shape of the various cuts from both sides of the metal plate. Various shapes such as -+< can be adopted, and wedge-shaped cuts (1) such as triangular pyramids can also be made in the desired direction of the thickness of the plate.

The composite material of this invention has a unique coefficient of thermal expansion and thermal conductivity due to the above-mentioned configuration, but furthermore, the composite material of this invention having different coefficients of thermal expansion and thermal conductivity is laminated in the thickness direction, and an arbitrary Thermal expansion coefficient and thermal conductivity can be set. Furthermore, a composite material having a high thermal expansion metal foil layer as the outermost layer can be obtained by laminating a plurality of the core materials described above.

In this invention, the high thermal expansion metal foil layer as the outermost layer is intended to improve uniformity of heat reception, thermal diffusion effect, bondability with the mating material, and adhesion of the thin film. 2
A thickness of 11 m or more is required, but if it exceeds 1100p, it becomes difficult to obtain consistency in the coefficient of thermal expansion, so
Let it be p.

Further, the thickness of the core material varies depending on the intended use, but it is required to be at least 0.1 mm, and if it exceeds 30 mm, it becomes difficult to manufacture by rolling.

In addition, the thickness ratio of the high thermal expansion metal and the low thermal expansion metal of the core material is as shown in Fig. 1.
When the low thermal expansion metal thickness is t2 and the high thermal expansion metal foil layer thickness of the outermost layer is t3, it is preferable that t1=it2 to 3t2, t3≦1/10 t2.

As will be made clear in the Examples described below, the thermally conductive composite material according to the present invention can be used by cutting it into a flat plate and brazing it, punching it into a desired shape and laminating a plurality of them, or laminating them with other thermally conductive materials. It can be processed in various ways, such as press molding into a cap shape, or bending into a desired shape to make an elastic thermally conductive composite material.
Glass layers etc. can be coated and applied before and after processing.

Based on the Drawings (Disclosure of the Invention) Figures 1a and 1b are perspective explanatory views showing a thermally conductive composite material according to the present invention.

FIGS. 2a, 3a, 4a and 6 are explanatory diagrams showing examples of semiconductor packages using the thermally conductive composite material of the present invention. FIG. 2b, FIG. 3b, and FIG. 4 are explanatory views of the thermally conductive composite material of the present invention.

Figure 4C is a partially enlarged view showing details of Figure 4a, Figure 4d
, e are explanatory diagrams of a thermally conductive composite material according to another embodiment of the present invention. FIG. 5 is an explanatory diagram showing a part of a high power module using the thermally conductive composite material of the present invention.

FIGS. 7a, 7b, and 8 are perspective explanatory views showing the concept of the method for manufacturing a composite material according to the present invention.

In the following description, a copper plate is used as the high thermal expansion metal plate of the core material, and Kovar (Fe-Co-Ni) is used as the low thermal expansion metal plate of the core material.
An example using a (alloy) plate will be explained.

The thermally conductive composite material (10) shown in FIGS. 1a and 1b has a large number of through holes (13
) A core material (14) to which a Kovar plate (12) having a
) and a high thermal expansion metal foil layer (16) pressure-welded to both sides of the core material (14).

Copper exposed surfaces (15) are formed on both sides of the core material (14) through the through holes (13) and exposed to the surface of the Kovar plate (12). Through holes (13) are formed and oblong copper exposed surfaces (15) are arranged. In the case of Figure 1, the holes are tapered so that the hole dimensions are different on the front and back sides, and the adjacent holes have the same hole size. They are arranged so that they are a combination of sizes.

In any of these configurations, the Kovar plate (12) is pressed against both sides of the copper plate (11) in the core material (14).
By selecting the thickness of each main surface, the ratio of the exposed copper surface (15), the dispersion state, etc., the thermal characteristics of each main surface can be approximated to the required characteristics.

Furthermore, the outermost high thermal expansion metal foil layer (16) pressed against both sides of the core material (14) is coated with Cu, Cu alloy, Al, Al alloy, Ni, taking into account the application and the material of the thin film layer to be applied.
, Ni alloy foil, etc. are selected, so that uniform heat reception, thermal diffusion effects, bondability with the mating material, and improvement of thin film adhesion can be achieved.

Wholesaler 1 The thermally conductive composite material (20) shown in Figures 2a and 2b is an example used as a heat dissipation substrate for a ceramic package.It is cut into rectangular plates with dimensions according to the package, and the required surface area is cut as shown in the figure. Ag solder (32) is deposited on the surface.

The heat conductive composite material (20) is, for example, in the heat conductive composite material (10) shown in FIGS. 1a and 1b, the core material (14) is made of a copper plate (11 )
The thickness ratio of the metal foil layer (12) and the ratio of the Kovar plate (12) to the copper exposed surface (15) are appropriately selected.
It consists of a structure in which Cu foil is selected for 6) and further plated with Ni, or Ni foil is selected for the metal foil layer (16), which has good adhesion to the Ag solder (32), and is plated with Ni. ).

That is, when the surface of the heat conductive composite material (20) is Cu foil, the Ag solder (32) reacts with the Cu foil when melting, and the formation of this reaction surface causes a decrease in heat conduction. Usually, Ni plating with a thickness of about 2 to 10 pm is required.

In particular, in order to improve the adhesion of Ni plating, after depositing Ni plating on the surface (Cu) of the thermally conductive composite material (20), use an inert atmosphere such as Ar or N2 or a reducing atmosphere such as N2. It is desirable to perform homogenization treatment (recrystallization annealing) at 750° C. to 950° C. for 2 minutes to 1 hour in a neutral atmosphere.

In the configuration shown in Fig. 2, the Ag solder (32) is applied only to the required position on one side of the thermally conductive composite material (20), but depending on the application, the thermally conductive composite material (20) Ag solder may be applied to one or both sides of the
In either configuration, it is desirable to apply Ni plating to the surface of the thermally conductive composite material (20) before applying Ag solder.As mentioned above, Ni plating only has the effect of preventing the reaction between Ag solder and Cu. Instead, it is possible to improve the flowability of the Ag solder and improve the airtightness of the package.

In addition, as shown in Fig. 2, the heat conductive composite material (20)
When applying Ag solder to the surface, the thickness of the Ag solder should be 30 to 1 mm, considering bondability with the package, workability, etc.
Approximately 20 screams are desirable. Note that the chip (31) in the figure is attached using Au-8i solder.

The thermally conductive composite material (21) shown in Figures 3a and 3b is an example used for a heat dissipation substrate for a ceramic package.
It is the same as the heat conductive composite material (20) in Figures a and b, but it also has a structure in which a heat conductive composite material (22) with a similar structure is laminated by brazing in the center, and a chip (31
) is brazed with Au-8i.

In this case, the main heat conductive composite material (21) is made to approximate the thermal properties of the ceramic (30), and the laminated heat conductive composite material (22) is made to closely approximate the thermal properties of the chip (31). It is preferable to consider the material and structure of the core material (14) and the material of the metal foil layer (16) so as to achieve this.

In the configuration shown in FIG. 3, a pair of thermally conductive composite materials (2
1) When integrating (22) with Ag solder, Ni plating should be applied to at least the surface to which the Ag solder of each thermally conductive composite material is applied, as explained in the configuration shown in Figure 2. is desired.

However, it is undesirable for Ag solder to adhere to the surface on which the chip is placed, as it creates unevenness on the surface where the chip is placed and reduces the accuracy of chip positioning. The outer peripheral side of the conductive composite material (22) is intentionally
It is desirable to reduce the flow of Ag solder without applying Ni plating, which improves the flowability of Ag solder.

In addition, when the heat conductive composite materials are laminated and arranged in a ceramic package as shown in the figure, the pair of heat conductive composite materials (21) and (22) are integrated in advance with Ag solder, and then one of the heat conductive composite materials is (21) and ceramics (30
) with Ag solder, but as another method to ensure the positional accuracy of the chip (31), it is possible to use Ag brazing on the -main surface of one of the heat conductive composite materials (21)
A solder is applied, and the other thermally conductive composite material (22) is temporarily fixed to the surface to which the Ag solder is applied using mechanical pressure bonding means, etc., and the thermally conductive composite material (21) and the ceramic (30) are bonded together.
It is possible to adopt a method in which Ag brazing is completed at the same time as joining with.

Kakeya J The thermally conductive composite material (23) shown in Figures 4a and b is an example used for a heat dissipation substrate for a ceramic package, and is equivalent to the thermally conductive composite material (20) shown in Figures 2a and b described above. and
It is press-molded into a cap shape with dimensions according to the package, and the peripheral edge is brazed with ceramics (30), and the chip (31) is brazed with Au-8i on the convex part.

This configuration can be easily manufactured by press molding,
In addition to the effect of the inherent thermal properties of the thermally conductive composite material (23), the formation of the cap-shaped cylindrical part (see 231
Also, the influence of the difference in thermal expansion between the chip and the thermally conductive composite material (23) can be further alleviated.

When adopting this configuration, it is necessary to select the thickness of the thermally conductive composite material (23) within a range that allows press molding. In particular, in order to satisfy the required thermal properties, if the thickness of the thermally conductive composite material (23) is increased, the fourth
As shown in Figure (e), since the radius of the bent portion (232) increases and the hole diameter of the ceramic package inevitably increases, a notch (301) is provided at the inner diameter open end of the ceramic package. This is desirable.

In addition, in consideration of press formability etc., thermally conductive composite material (2
If the thickness of 3) is made thinner, there is a concern that not only will the chip be deformed due to stress during chip bonding, making it difficult to properly place the chip, but also that the required heat dissipation effect, especially in the plane-parallel direction, will not be achieved. be done.

In such a case, as shown in Fig. 4(d), a heat conductive composite material (23) formed into a cap shape is made of a high heat conductive material such as Cu, Cu alloy, AI, or A1 alloy, and a convex part is formed in the center. It is desirable to bond the reinforcing material (40) with the shaped protrusions (401).

If the optimal shape and dimensions are selected for this reinforcing material (40), a conventional heat dissipating fin (5) as shown in FIG. 9(a) can be obtained.
can be made unnecessary.

Moreover, this reinforcing material (40) is thin and the heat conductive composite material (2
3), if there is a concern that warpage may occur due to the bimetallic effect, apply a Ni-Fe based material to one side of the reinforcing material (40), that is, the main surface opposite to the surface to which the thermally conductive composite material (23) is adhered. It is desirable to join low thermal expansion alloys.

In addition, in order to prevent deformation during chip bonding and to take into account the difference in thermal expansion with the chip, the chip mounting surface of the thermally conductive composite material (23) has a predetermined thickness as shown in FIG. 4(e). Other thermally conductive composite materials, Mo, Cu-M.

It is also a preferable configuration to bond a reinforcing plate material (42) such as alloy or Cu-W alloy.

As shown above, the present inventor has proposed various configurations that effectively use the thermally conductive composite material (23) press-formed into a cap shape, but usually the thermally conductive composite material (23) with a thickness of about 0.2 to 0.3 mm is used. It was confirmed that the material could be press-formed into the required cap shape and also provide good thermal properties.

In any of the configurations shown above, it is undesirable for Ag solder to adhere to the chip mounting surface, as in the configuration shown in FIG.
It is desirable to have a structure in which the surface of a high thermal expansion metal foil such as Cu is exposed as it is, without applying Ni plating to improve the flowability of solder.

Configuration 4 The thermally conductive composite material (24) shown in Figure 5 is an example used in a high-power module, and is made by bending a plate into a U-shape, with a solder layer adhered to the required surface, and one end of the thermally conductive composite material (24). The Cu lead (33) is connected to the other plate-shaped thermally conductive composite material (2).
5) are brazed so that the chip (31) is sandwiched between them, and the whole is resin molded.

In this configuration, a pair of thermally conductive composite materials (24) (2
5) is a lead for passing a large current, and also has the function of dissipating the heat generated from the chip (31). In particular, the heat conductive composite material (24) reduces the effects of external vibrations, etc. In order to do this, it is made into a U-shape and has the function of an elastic body.

The thermally conductive composite material (24x25) is the thermally conductive composite material (10) shown in Figures 1a and 1b, in which the core material (14) is made of a copper plate ( The thickness ratio of 11) and the Kovar plate (12) and the ratio of the Kovar plate (12) to the exposed copper surface (15) are selected appropriately, and Cu foil is selected for the metal foil layer (16), which is further plated with Ni. Alternatively, the metal foil layer (16) is made of Ni foil, which improves adhesion with solder and improves bondability with the chip (31).

That is, as shown in FIG. 5, when the chip (31) and the thermally conductive composite material (24x25) are integrated by solder, the entire surface of the thermally conductive composite material (24) (25) is formed of Cu. Because of this, the solder flows well and a good bond can be obtained.

In particular, when the thermally conductive composite material of the present invention and other members are integrated with a low melting point bonding agent such as solder, FIG.
As shown in Figures 3 and 4, Ag brazing material ζCu
There is no need to worry about the reaction with the Cu surface.
There is no need to apply i-plating.

Furthermore, in the configuration shown in Fig. 5, the solder layer is formed only at a predetermined position of the thermally conductive composite material, but depending on the application, the solder layer may be pre-soldered on one principal surface or the entirety of both surfaces of the thermally conductive composite material. A configuration in which layers are formed can also be adopted.

Configuration 5 The thermally conductive composite material (26) shown in Fig. 6 is an example used as a heat dissipation board for a metal package, and is formed into a boat shape to accommodate a chip (34), with the chip (34) in the four central parts.
34) for brazing, and place a metal cap (37) on the periphery.
) is placed and sealed, the lead frame (35) is sandwiched and the glass (36) is sealed.

The heat conductive composite material (26) is the heat conductive composite material (10) shown in FIGS.
The thickness ratio of the copper plate (11) to the Kovar plate (12) and the ratio of the Kovar plate (12) to the exposed copper surface (15) are appropriately selected to obtain thermal matching with the metal foil layer (16). ) to A
It has a structure in which I-foil is selected, and has excellent sealing properties to glass (36) and good adhesion to Ag wax or solder.

In addition, since AI foil is selected for the metal foil layer (16) of the heat dissipation board, the chip (34) is attached via the insulating layer.
In addition, in order to improve corrosion resistance after sealing, a metal foil layer (
16) The outer surface is coated with ceramics such as alumina or anodized.

Furthermore, even in a configuration in which a heat dissipation substrate in which Cu foil is selected as the metal foil layer (16) used in configuration 1 described above, and an AI film is formed on the required sealing area, the glass sealing property is excellent, and Ag wax or Good adhesion with solder etc.

Manufacturing method To explain the manufacturing method of the composite material (10) having the configurations shown in FIG. 1a and b, as shown in FIG. For example, a large number of small holes are punched to form a mesh shape, and after annealing, a surface treatment is performed and the material is wound into a coil.

A copper plate (11) coil of required dimensions and thickness is unwound, and the unwound Kovar plates (12) are stacked from above and below and rolled and bonded using a large-diameter rolling roll (50) in a cold or warm state. Furthermore, if necessary, after bonding, diffusion baking is performed to improve adhesion.

As a result of pressure welding, as shown in Figure 1, Kovar plate (12)
Copper enters into the numerous through holes (13) of the Kovar plate (12), and the exposed copper surface (15) is partially disposed at the required position of the Kovar plate (12).
A formed core material (14) is obtained. Furthermore, it is diffusion annealed, subjected to surface treatment, and wound into a coil.

Next, as shown in Figure 7, the core material (14) coil is unwound, unwound Cu, A1, etc. σ metal foil (16x16) is overlaid from above and below, and rolled on a cold or warm rolling roll. Pressure welding is performed by (51).

Next, if necessary, this composite material is diffusion annealed and further rolled to a required thickness.

In addition, as shown in Fig. 8, after annealing, a copper plate (11) of the required dimensions and thickness was wound into a coil after surface treatment. The Kovar plate (12 x 12) that has been applied and wound into a coil is unwound from above and below and stacked on the copper plate (11), and then each Kovar plate (12) (1
From above 2), the metal foil (16×16) that has been surface-treated and wound into a coil is preferably unwound and stacked, and then joined together by pressing and rolling with the required number of rolling rolls (52).

As mentioned above, the heat conductive composite material of the present invention can be obtained in the form of a plate of predetermined dimensions by rolling and pressure welding, so there is no need to use complicated processing methods such as mechanical processing to finish it to a predetermined thickness. It has the advantage that it can be manufactured at low cost, has excellent cutting workability, and can be easily processed depending on the package substrate or chip.

Examples Example 1 A pair of Kovar plates with a thickness of 0.5 mm and a width of 30 mm (
29Ni-16Co-Fe alloy), each with a pore size of 1. Om
m, a large number of holes were made with a hole spacing of 1.5 mm, and further, 9
After annealing at 00''C, wire brushing was performed.

The average coefficient of thermal expansion of Kovar plate at 30-200°C is 1;! : 5.2xlO-6/'Cte.

Further, a Cu plate having a thickness of 1.0 mm and a width of 30 mm was similarly annealed and wire brushed. Cu plate 3
Average thermal expansion coefficient Lt at 0-200°C 17.2
It was X10-610C.

The Kovar plate and the Cu plate were pressure-welded using a cold pressure welding machine shown in FIG. 7a to obtain a core material with a plate thickness of 0.85 mm.

That is, copper entered the through holes of the Kovar plate during cold welding, and the core material shown in FIG. 1 was obtained in which the surface of the copper plate was partially exposed at a predetermined position on the surface of the Kovar plate.

This core material was diffusion annealed at 800° C. for 5 minutes to be joined and integrated.

The Cu exposed surface on the main surface of the obtained core material had an elliptical shape elongated in the rolling direction, the hole interval was 1.0 mm in the rolling direction, and the ratio of the Cu exposed surface to the Kovar plate was 35%.

The thermal conductivity in the thickness direction of the obtained core material was 230 w/m-K, and the coefficient of thermal expansion on each principal surface was 8.
xlO'/"C.

0.05mmJ' on both sides of the core material with a thickness of 0.85mm
*Cu foil was pressure-welded using a two-stage cold pressure welding machine to obtain a thermally conductive composite material with a plate thickness of 0.370.

The thickness (tl) of the Cu plate constituting the core material in this thermally conductive composite material is 0.166 mm, and the thickness (t2) of the Kovar plate
) is 0.095 mm, respectively, and the thickness of the surface Cu foil (t
3) were each 0.007 mm (see Figure 1a).

A thermally conductive composite material having a plate thickness of 0.37 mm was cut into required dimensions, and two sheets were laminated to form a heat dissipation board as shown in FIG. 3a.

When a ceramic package was manufactured using the above heat dissipation substrate, it was confirmed that good heat dissipation properties were obtained and the thermal consistency was also excellent.

Furthermore, after annealing the heat conductive composite material with a plate thickness of 0.37 mm,
It was cold rolled to a plate thickness of 0.15 mm. In the obtained thermally conductive composite material, the CuN W ” constituting the core material
s (+,) l'r n nAQ,,,,,, z Barrel oga's easiness/+,) I dimension each 0.038 mm,
The thickness (t3) of the Cu foil on the surface is 0.003 mm.
Met.

After that, when we processed the lead frame into a lead frame using a known method and produced a semiconductor package, we found that there was no peeling of the adhesive interface between the chip and the island, no cracking of the sealing resin, etc., and no conventional copper alloy was used. Good heat dissipation properties similar to those of conventional lead frames were obtained.

Example 2 The same material as in Example 1 was used, and the manufacturing method and conditions were the same as in Example 1, except that the copper plate of the core material and the Kovar plate were pressed together while being heated. A thermally conductive composite material with a thickness of 0.37 mm was produced.

In this thermally conductive composite material, the thickness (tl) of the Cu plate constituting the core material is 0.158 mm, and the thickness (tl) of the Kovar plate constituting the core material is 0.158 mm.
2] are each 0.100 mm, and the thickness of the surface Cu foil (
t3) were each 0.006 mm.

After annealing a heat conductive composite material with a thickness of 0.37 mm, the thickness of the composite material is 0.
．． It was cold rolled to 25 mm. In the obtained thermally conductive composite material, the thickness (tl) of the Cu plate constituting the core material was 0.
106 mm, and the thickness (t2) of the Kovar plate is 0.
068 mm, and the thickness (t3) of the Cu foil on the surface is 0.
．． It was 0.004 mm. This thermally conductive composite material is shown in Figure 4a.
As shown in Figure 2, when a heat dissipating substrate was made by press forming into a camp shape, it was confirmed that various deep drawings were possible and the press formability was excellent.

Furthermore, when a ceramic span cage was manufactured using the above-mentioned heat dissipation substrate, it was confirmed that good heat dissipation properties were obtained and the thermal consistency was also excellent.

Example 3 A pair of Kovar plates (29Ni-16Co-Fe alloy) with a plate thickness of 0.5 nm and a plate width of 30 mrn, each having a width of 1.0 m.
A large number of wedge-shaped cuts of 0.5 mm and 0.5 mm were made on both sides, and after annealing at 900° C., wire brushing was performed.

Further, a Cu plate having a thickness of 1.0 mm and a width of 30 mm was similarly annealed and wire brushed.

Kovar plates were stacked on both sides of the Cu plate, and then a 0.05 mm thick Al foil whose surface had been cleaned was pressed onto the upper surface of each Kovar plate using a warm pressure welding machine equipped with multiple rolls. A heat conductive composite material having a plate thickness of 0.4 plate as shown in the figure was obtained. In this thermally conductive composite material, the thickness (tl) of the Cu plate constituting the core material is 0.105 mm, the thickness (L2) of the Kovar plate is 0.178 mm, and the surface AI
The thickness (t3) of each foil was 0.006 mm.

The thermal conductivity in the thickness direction of the obtained core material was 230 w/m-K, and the coefficient of thermal expansion on each principal surface was 8.
It was xlO-6/°C.

This composite material was processed into a plate thickness of 0.25 mm by cold rolling, and then processed into a heat dissipation board by a known method. In the obtained thermally conductive composite material, the thickness (tl) of the Cu plate constituting the core material is 0.110 mm, and the thickness (t2) of the Kovar plate.
are 0.067 mm, respectively, and the thickness of the AI foil on the surface (t3
) were each 0.003 mm. When we fabricated a semiconductor metal package, we were able to obtain good heat dissipation.
Moreover, excellent glass sealing properties were obtained.

[Brief explanation of drawings]

FIGS. 1a and 1b are perspective explanatory views showing a thermally conductive composite material according to the present invention. FIG. 2a, FIG. 3a, FIG. 4a, and FIG. 6 are explanatory diagrams showing examples of semiconductor packages using the thermally conductive composite material of the present invention. FIG. 2b, FIG. 3b, and FIG. 4 are explanatory views of the thermally conductive composite material of the present invention. Figure 4C is a partially enlarged view showing details of Figure 4a, Figure 4d
, e are explanatory diagrams of a thermally conductive composite material according to another embodiment of the present invention. FIG. 5 is an explanatory diagram showing a part of a high power module using the thermally conductive composite material of the present invention. FIGS. 7a, 7b, and 8 are perspective explanatory views showing the concept of the method for manufacturing a composite material according to the present invention. FIGS. 9a and 9b are longitudinal cross-sectional views of a package showing a conventional heat dissipation board. FIG. 10 is a schematic diagram of a semiconductor package. 1.31,32,34...chip, 2...MO material,
3... Alumina material, 4... Kovar material, 5... Radiation fin, 6... Composite board, 7... Flange part,
8o...Lead frame, 81...Island, 8
2... Stitch, 83... Lead portion, 84... Chip, To 8... Bonding wire, 8a... Resin, 10. 20, 21, 22, 23, 24, 25... Heat Conductive composite material, 11... Copper plate, 12... Kovar plate, 13... Through hole, 14... Core material, 15... Copper exposed surface, 16... Metal foil layer, 231...・Cylindrical part, 23
2...Bending portion, 30...Ceramics, 301...
... Notch, 33... Cu lead, 36... Glass, 37... Metal gap, 40... Reinforcement material, 40
1... Convex projection, 41... Reinforcement plate material, 50.51.
52...Reduction roll.

Claims (1)

[Claims] 1. A low thermal expansion metal plate having a large number of through holes in the thickness direction is integrated on both sides of a high thermal expansion metal plate, and the high thermal expansion metal is exposed on the surface of the low thermal expansion metal plate from the through holes. 1. A thermally conductive composite material comprising: a core material; and a high thermal expansion metal foil layer of the same or different type as the high thermal expansion metal of the core material, which is pressed against both sides of the core material. 2 Select the thickness ratio of the metal plate of the core material and/or the surface area ratio of the high thermal expansion metal and the low thermal expansion metal exposed on the surface of the low thermal expansion metal plate, and change the thermal expansion coefficient and/or thermal conductivity to the required value. The thermally conductive composite material according to claim 1, wherein the thermally conductive composite material is 3 The high thermal expansion metal plate is Cu, Cu alloy, Al, Al alloy,
Any of the steels, the low thermal expansion metal plate contains Mo, a Ni-Fe alloy containing 30 to 50 wt% Ni, 25 to 35 wt% Ni and 4 to 2
Ni-Co-Fe alloy containing 0 wt% Co, any of W, the high thermal expansion metal foil layer is Cu, Cu alloy, A
Thickness t_1 of the high thermal expansion metal plate that is made of any one of Al alloy, Ni, and Ni alloy and constitutes the core material, thickness t_2 of the low thermal expansion metal plate, and thickness t_ of the high thermal expansion metal foil.
3 is t_1=1t_2~3t_2, t_3≦1/10
The thermally conductive composite material according to claim 1 or 2, characterized in that it satisfies t_2. 4. Cu at a required position on at least one main surface of the thermally conductive composite material.
4. The thermally conductive composite material according to claim 1, wherein the thermally conductive composite material is coated with a metal plating consisting of any one of , Al, Ni, and Sn.