JPH11297908A - Heat spreader and manufacture thereof, and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an increase in a coefficient of thermal expansion and have excellent thermal expansion characteristic and sufficient thermal conductive characteristic, by a method wherein a thermal expansion restriction layer is formed with a high thermal conductive layer of a Cu-based material, low thermal expansion layer of a Fe-Ni-based alloy having a through hold, and a metal having a coefficient of thermal expansion of a specified value or less. SOLUTION: A high thermal conductive layer of a Cu-based metal and a low thermal expansion layer of a Fe-Ni-based alloy having a plurality of through holes are laminated to form a basic structure 4 of a multilayer structure. A high thermal conductive layer 3 is filled up in a through hole 2 on both sides of a low thermal expansion layer 1, and continued via the through hole 2. As a thermal expansion restriction layer 5 composed of a metal in which a coefficient of thermal expansion α30-800 deg.C is 7.5×10<-6> / deg.C or less, at least one species of metal layer out of a Mo-based metal and a W-based metal is disposed outside the basic structure 3 of a multilayer structure. Thus, it is possible to obtain low thermal expansion characteristic in a high temperature region of 500 deg.C or more and ensure high thermal conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat spreader capable of coping with an increase in heat generation due to, for example, high integration of a semiconductor device, a semiconductor device using the same, and a method of manufacturing a heat spreader.

[0002]

2. Description of the Related Art PGA (Pin Grid Array) is mainly used in CPUs (Central Processing Units) of computers, workstations, personal computers (PCs) and the like.
A ceramic package called y) is applied, and heat generated from the silicon chip is dissipated via a heat transfer substrate (heat spreader) between the silicon chip and an aluminum heat sink fin. On the other hand, recent L
In the case of SI, dissipation of heat generated from a silicon chip has become an extremely important problem due to high speed and high power consumption. In particular, a microcomputer or a logic ASIC (Appl.
LSIs for IC (Specialization IC)
For example, a heat spreader is brought into contact with a silicon chip to promote heat dissipation.

For example, a PGA (Pin Gr) shown in FIG.
An example of an (id Array) package is a heat spreader (11), a silicon chip (8), a bonding wire (9), a ceramic substrate (10), and a pin (1).
2), a silver brazing (13) and a lid (14).
In this structure, the heat spreader (11) is in contact with the silicon chip (8), and has not only a heat dissipation property for dissipating the heat generated from the silicon chip (8) but also a thermal expansion coefficient similar to that of the silicon chip (8). Is important. Further, since the heat spreader (11) is directly silver-brazed to the ceramic substrate (10), it is important that the thermal expansion coefficient is close to that of the ceramic substrate (10). It is anticipated that demand for these types of packages will continue to increase. In addition, in order to make contact with the silicon chip, the heat spreader for such an application needs to have its thermal expansion matched with the silicon chip, and generally has an average thermal expansion coefficient of 30 to 150 ° C. of 4 to 4.
It is said that a material having a density of about 11 × 10−6 / ° C. is desirable.

In order to satisfy such characteristics, conventionally, a heat spreader for a semiconductor device has been formed of a plate of Cu-W or Mo and having a thickness of 0.5 to 1 mm and a size of about 30 mm square. However, these materials are expensive and have a specific gravity of 89W-11Cu.
0 × 10 ³ kg / m ³ , Mo: 10.2 × 10 ³ kg / m ³
a large weight for packaging and m ³ is inevitably large, downsizing is a trend of recent LSI,
It is also a major drawback in weight reduction.

It is to be noted that, instead of the above-mentioned PGA type LSI, an LSI of a type using a conventional lead frame is used.
Although the lead frame itself adopts a method in which the lead frame itself is made of copper and a copper alloy with good heat dissipation, the thermal expansion coefficient in this case is larger than that of the silicon chip, so the interface between the silicon chip and the lead frame is Internal stress in the silicon chip may cause a problem, and cracks may occur in the silicon chip due to stress generated during the process or during use. As a material for solving this problem, the present inventors have developed a composite material for electronic components 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 thermal expansion Fe-Ni-based alloy thin plate, and An invention relating to a manufacturing method is proposed as Japanese Patent Application Laid-Open No. Hei 8-23249. Further, Japanese Patent Application Laid-Open Nos. 2-231751, 7-80272, and the like also propose a combination of a low expansion material having a through hole and a high thermal conductive material.

However, a PG that does not use a lead frame
In a package such as A, a structure in which copper and an Fe-Ni-based alloy are simply multi-layered cannot be applied as a heat spreader due to poor heat conduction in the thickness direction, in other words, in the lamination direction. There is a need for a new heat spreader that is inexpensive and can be reduced in size, thickness, and weight in place of Cu-W and Mo plates. Note that a package that does not use a lead frame is provided with PGA and BGA (Ball Grid Array) or CS
P (Chip Size Package) has been put into practical use, and great demand is expected in the future.

[0007]

When the above-mentioned heat spreader was examined, it was found that the used Fe-Ni
When the Curie point of the system alloy exceeds the Curie point around 230 ° C., the thermal expansion rapidly increases, and the low thermal expansion characteristic cannot be obtained up to a heating temperature range of 500 ° C. or more performed at the time of silver brazing. For this reason, when the above-mentioned heat spreader is joined to an extremely thin ceramic of 1 mm or less, which is expected to be used in the future, by silver brazing, in the cooling and hardening process after the silver brazing, the difference in the amount of shrinkage between the heat spreader and the ceramic causes In some cases, there was a problem of breakage or delamination, and it was necessary to study how to reduce the thermal expansion at high temperatures. Further, in the case where the joining is performed by cooling different materials from a high-temperature heating state as in the case of silver brazing, the above-mentioned problem is an unavoidable problem. When bonding with a metal called a sealing material such as
It is necessary to match up to a high temperature of 00 ° C. or more. SUMMARY OF THE INVENTION An object of the present invention is to provide a heat spreader which can reduce an increase in thermal expansion coefficient up to a high temperature of 500 ° C. or more, has excellent thermal expansion characteristics and sufficient heat conduction characteristics, a semiconductor device using the same, and a method of manufacturing a heat spreader. To provide.

[0008]

The inventor of the present invention has conducted detailed studies on the heat spreader exposed to a high temperature of 500 ° C. or more to solve the above-mentioned problems. After a Ni-based alloy and a Cu-based metal are alternately or continuously laminated to form a multilayer structure, a coefficient of thermal expansion α30-800 ° C. is 7.5 × 10−6 / ° C. or less outside or between layers. It has been found that the formation of the thermal expansion suppressing layer can realize low thermal expansion characteristics from room temperature to a high temperature range of 500 ° C. or more, and have reached the present invention.

That is, the present invention provides a high thermal conductive layer of a Cu-based metal, a low thermal expansion layer of an Fe-Ni-based alloy having a plurality of through holes, and a thermal expansion coefficient α30-800 ° C. of 7.5 × 10−6. This is a heat spreader provided with a thermal expansion suppressing layer made of a metal having a power of not more than a power of / ° C.

The present invention also provides a high thermal conductive layer of a Cu-based metal, a low thermal expansion layer of an Fe-Ni-based alloy having a plurality of through holes, and a thermal expansion coefficient α30-800 ° C. of 7.5 × 10−6. A heat spreader comprising a thermal expansion suppressing layer made of a metal having a power of not more than a power of / ° C., wherein the coefficient of thermal expansion α30-800 ° C. is 7.5 × 10−6.
The volume ratio of the thermal expansion suppressing layer made of a metal having a temperature of
% Heat spreader.

Further, the present invention provides a multi-layer structure in which a high thermal conductive layer of a Cu-based metal and a low thermal expansion layer of an Fe-Ni-based alloy are alternately or continuously laminated to form a multilayer structure. The high thermal conductive layer is a heat spreader continuous through a plurality of through-holes formed in the low thermal expansion layer, and between the layers of the heat spreader and the surface on which the heat-dissipating component is mounted and the opposite surface side on which the heat-dissipating component is mounted. At least one of them has a thermal expansion coefficient α30-800 ° C of 7.5.
It is a heat spreader formed by a thermal expansion suppression layer made of a metal having a density of × 10−6 / ° C. or less.

Preferably, in the present invention, the thermal expansion suppressing layer is a heat spreader on which at least one metal layer of a Mo-based metal and a W-based metal is formed. In the present invention, the outermost layer is more preferably a Cu-based metal. Laminate metal. The preferred number of layers of the present invention is 5 to 15 layers. Further, the present invention is a semiconductor device in which a semiconductor chip is mounted on the above-described heat spreader.

The above-described heat spreader of the present invention has a C
Fe-Ni having a thin plate of u-based metal and a plurality of through holes
Alternately or continuously laminating a plurality of alloy thin plates,
Thermal expansion coefficient α30−
A thermal expansion suppression layer made of a metal at 800 ° C. of 7.5 × 10 −6 power / ° C. or less is arranged, and after filling in a can body, the pressure is reduced to less than 10 −3 Torr, and then sealing is performed. In a temperature range of 1050 ° C., a bonding process is performed by applying a pressure of 50 MPa or more, a Cu-based metal is filled in the through-hole, and the respective layers are bonded together, and then finished to a predetermined thickness by rolling. Obtainable.

In the present invention, when a Cu-based metal is laminated on the outermost layer, a plurality of Cu-based metal sheets and a plurality of Fe—Ni-based alloy sheets having a plurality of through holes are laminated alternately or continuously. The coefficient of thermal expansion α30-800 ° C. is 7.5 × 10−6 /
After placing a thermal expansion suppressing layer made of a metal having a temperature of not more than 0 ° C. and further placing a Cu-based metal on its outermost layer and filling the can body,
Sealing after reducing the pressure to less than -3 Torr, and then 50 MPa in a temperature range of 700 to 1050 ° C.
A bonding process is performed by applying a pressure as described above, and the through-hole is filled with a Cu-based metal and bonded together, and then rolled to obtain a sheet having a predetermined thickness.

In the heat spreader of the present invention obtained by this method, the high heat conductive layers are joined together in the middle of the through hole formed in the low thermal expansion layer, and a continuous high heat conductive layer is formed via the through hole. Further, as a preferable laminated structure of the composite material, Cu-based metal is disposed on the upper and lower surfaces of the thermal expansion suppressing layer.

[0016]

As mentioned above, an important feature of the present invention is that the coefficient of thermal expansion α30-800 ° C. is 7.5 × 10−6 at the outer side of the multilayer structure and at least one of the layers.
That is, a thermal expansion suppressing layer made of a metal having a power / ° C or lower is provided. In order to realize the low thermal expansion characteristic of the present invention in a high temperature range of 500 ° C. or higher, the thermal expansion coefficient α30-800 ° C. is 7.5 × 1.
It is necessary to form a thermal expansion suppressing layer of 0-6 / ° C or less. Specifically, it is a characteristic possessed by metals such as Mo-based metals, W-based metals, Nb-based metals, and Ta-based metals. By arranging these metals outside the multilayer structure and at least one of the layers, Fe -It is possible to obtain a low thermal expansion characteristic in a high temperature region of 500 ° C. or higher, which was impossible with a composite material having a multilayer structure composed of only a Ni-based alloy and a Cu-based metal. Breakage, peeling, and the like can be prevented.

The main purpose of using the Cu-based metal constituting the multilayer structure of the present invention is to secure a high thermal conductivity. It is effective to use a Cu-based metal having about 330 W / m · K or more. In addition, Fe constituting the multilayer structure
The primary purpose of using a Ni-based alloy is to ensure excellent low thermal expansion characteristics below the Curie point. With the above-mentioned multilayer structure composed of Cu-based metal and Fe-Ni-based metal,
It is possible to obtain basic characteristics as a heat spreader having both excellent heat conduction characteristics and excellent low thermal expansion characteristics in a low temperature range below the Curie point.

Further, as in the present invention, Cu-based metal and Fe-
By forming a composite material in which a Ni-based metal and a Mo-based metal are combined, for example, a Mo-based metal alone or
Compared to composite materials combining o-based metal and Cu-based metal,
While minimizing the use of expensive Mo-based metal elements, excellent low thermal expansion characteristics can be obtained up to a high temperature range, which is advantageous for cost reduction. Furthermore, by using a pure Cu in the example a specific gravity of about 8.95 g / cm ³ as in the present invention, for example, a Fe-36 Ni alloy having a specific gravity of about 8.15 g / cm ^3,
For example, by using a composite material in combination with a Mo-based metal having a specific gravity of 10.2 g / cm ³ , it is possible to obtain excellent low thermal expansion characteristics up to a high temperature range while minimizing the use of a Mo-based metal element having a large specific gravity. This also has the advantage that the weight of the heat spreader can be reduced.

The thermal expansion suppressing layer of the present invention needs to have a thermal expansion coefficient α30-800 ° C. in a high temperature range of 500 ° C. or more of 7.5 × 10−6 / ° C. or less. Specifically, it is preferable to use a Mo-based metal or a W-based metal having excellent heat conduction properties as compared with an Nb-based metal or a Ta-based metal.
Since the thermal conductivity of the base metal and the W-based metal has a high property of 130 W / m · K or more, excellent low thermal expansion properties at high temperatures and particularly excellent thermal conductivity properties can be realized. In particular, Mo-based metals are excellent in workability, and are particularly effective when working after joining as in the production method of the present invention.

It is effective to form a Cu-based metal layer on the outermost layer of the heat spreader in order to quickly spread the heat from the component to be radiated to the entire surface of the heat spreader.
Further, the Cu-based metal layer as the outermost layer of the heat spreader also has an effect as a buffer layer for relieving thermal stress generated between the ceramic and the heat spreader at the time of silver brazing.

FIG. 1 shows a basic structure (4) of a multilayer structure in which a high thermal conductive layer of a Cu-based metal and a low thermal expansion layer of an Fe—Ni-based alloy having a plurality of through holes are laminated according to the present invention. As shown in FIG. 1, the high thermal conductive layers (3) on both sides of the low thermal expansion layer (1)
Are filled in the through hole (2) and are continuous via the through hole (2). By doing so, Fe
-Heat transfer across the low thermal expansion layer of the Ni-based alloy in the thickness direction is ensured. In the present invention, as shown in FIG. 2, a thermal expansion coefficient α30-80 is provided outside the basic structure (4) of the multilayer structure.
For example, at least one metal layer of a Mo-based metal and a W-based metal is disposed as the thermal expansion suppressing layer (5) made of a metal whose 0 ° C. is 7.5 × 10−6 / ° C. or less.

In the present invention, the basic structure of the multilayer structure (4)
The Fe-Ni alloy suppresses the thermal expansion of the Cu alloy in the planar direction of the laminated material. But F
At a high temperature exceeding the Curie point, the coefficient of thermal expansion of the e-Ni-based alloy also rapidly increases, so that the effect of suppressing the thermal expansion of Cu is reduced. On the other hand, the present invention has a smaller thermal expansion coefficient α30-800 ° C of 7.5 × 10−6 / ° C or less even in a high-temperature region of 500 ° C or more, and more equal to Fe—Ni-based alloys. M with anisotropic thermal expansion coefficient
By arranging at least one metal layer of an o-based metal and a W-based metal, low thermal expansion at a high temperature can be realized.

In the present invention, if a Cu-based metal layer is formed on the outermost layer of the heat spreader on which the heat-dissipating component is mounted, heat from the heat-dissipating component such as a semiconductor chip can be quickly diffused in the plane direction. Will be possible. Specifically, as shown in FIG. 3, a thermal expansion suppression layer (a metal having a thermal expansion coefficient α30-800 ° C. of 7.5 × 10−6 / ° C. or less) is provided outside the basic structure (4) of the multilayer structure. 5)
For example, a metal layer of at least one of a Mo-based metal and a W-based metal is disposed, and a high thermal conductive layer (3) made of a Cu-based metal is disposed outside the thermal expansion suppressing layer (5).

As described above, the Cu-based metal layer, that is, the high thermal conductive layer (3) disposed on the surface of the heat spreader is generated at the time of brazing the heat spreader to a package constituent material made of a semiconductor chip or the like and a ceramic or the like to be radiated. This is effective because it also acts as a layer for buffering thermal stress. Also, as shown in FIG. 3, providing a Cu-based metal layer on the side opposite to the above-mentioned surface is effective in securing the symmetry of the layers constituting the heat spreader and reducing the occurrence of warpage. .

In the present invention, as shown in FIGS. 5 and 6, it is also possible to arrange a thermal expansion suppressing layer (5) between layers inside the basic structure (4) of the multilayer structure. in this case,
As shown in FIGS. 5 and 6, in order to ensure that the high thermal conductive layer (3) is filled in the through holes (2) provided in the low thermal expansion layer (1), the thermal expansion suppressing layer (5) is used. It is preferable to dispose a high thermal conductive layer (3) in a layer adjacent to.

In the present invention, the thermal expansion coefficient is α30-800 ° C.
Is, for example, at least one metal selected from the group consisting of Mo-based metals and W-based metals. The volume ratio of the thermal expansion suppressing layer in the heat spreader of the present invention is at most 3%.
It is desirable to be 5% or less, and when the volume ratio of the Cu-based metal is decreased due to too large volume ratio of the thermal expansion suppressing layer, it may be difficult to maintain excellent heat conduction characteristics. Practical thermal conductivity 150W / m · as a heat spreader
The volume ratio of the thermal expansion suppressing layer that can obtain K or more is 3% to 25%.
% Range.

In the present invention, the form in which the above-described heat spreader is used for a semiconductor device is not limited. A typical example is the BGA (Bal
An iGrid Array package has a structure including a heat spreader (11), a silicon chip (8), a Cu wiring (9), a polyimide film (10) for insulation, and a solder ball (12) as a terminal. be able to.

The Cu-based metal layer used in the present invention and F
6. e-Ni-based metal layer and thermal expansion coefficient α30-800 ° C.
Sufficient reliability to ensure that no delamination occurs between the layers of the thermal expansion suppression layer made of a metal having a density of 5 × 10−6 / ° C. or less, due to environmental changes such as plastic working such as rolling, thermal shock, and temperature cycles. 700-105 to obtain a joint with
Bonding is performed in a temperature range of 0 ° C. by applying a pressure of 50 MPa or more. When a high pressure of 50 MPa or more is applied in a temperature range of 700 to 1050 ° C., Cu
A diffusion layer can be formed between the Fe-Ni-based metal layer and the Fe-Ni-based metal layer extremely easily as compared with the conventional bonding method of performing pressure bonding and annealing by cold rolling, thereby improving reliability. Excellent bonding is obtained.

When a high pressure of 50 MPa or more is applied in a temperature range of 700 to 1050 ° C., C
7.5 × 1 with u-based metal layer and thermal expansion coefficient α30-800 ° C.
A thermal expansion suppressing layer made of a metal having a value of 0-6 or less or a Fe-Ni-based metal layer and a thermal expansion coefficient α30-800
A new surface of each layer can be exposed and bonded in an active state between each layer and a thermal expansion suppressing layer made of a metal having a temperature of 7.5 × 10 −6 power / ° C. or less. It is possible to perform bonding with higher reliability than the pressure bonding by cold rolling.

The temperature at which the above bonding is performed is preferably 7
The temperature range is from 00 to 1050C. In the present invention, at a temperature lower than 700 ° C., particularly, the active state between the thermal expansion suppressing layer and the Cu-based metal layer, or between the thermal expansion suppressing layer and the Fe—Ni-based metal layer, is insufficient, and is stable. This is not preferable because a poor bond cannot be obtained and partial peeling and cracking occur. At a high temperature exceeding 1050 ° C., the interdiffusion between the Cu-based metal layer and the Fe—Ni-based metal layer remarkably progresses, and the Fe-based element or the Ni element dissolved in the Cu-based metal layer causes the Cu-based metal layer to become insoluble. It is not preferable because the high thermal conductivity is impaired. Further, the Cu-based metal layer may melt, which is dangerous. Therefore, in the present invention, the temperature at which the bonding is performed is specified in a temperature range of 700 ° C. to 1050 ° C. The pressure is preferably as high as possible,
From the viewpoint of device performance, 200 MPa or less is realistic, and is preferably in the range of 80 to 150 MPa.

Further, in the present invention, prior to the above-described bonding treatment, the Cu-based metal layer and the Fe-Ni-based metal layer and the metal having a coefficient of thermal expansion α30-800 ° C. of 7.5 × 10−6 / ° C or less are used. After the thermal expansion suppressing layer is filled in the can body, a step of sealing after reducing the pressure to less than 10 −3 Torr is provided. This is because the present invention
When gas remains in the through holes formed in the Ni-based alloy material,
Because the through-hole cannot be sufficiently filled with the Cu-based metal, or because the Cu-based metal filled from both sides of the through-hole is unjoined in the middle of the through-hole to hinder heat conduction,
The deaeration process is performed. Further, in the present invention, after the above-described joining processing, the sheet is finished to a predetermined thickness by hot rolling or cold rolling.

In the present invention, the bonding process is performed under a high pressure as described above.
It may be difficult to fill the u-based metal. Therefore,
In the present invention, hot rolling or cold rolling is applied after the above-described joining process. According to the heat spreader of the present invention obtained by this method, a structure in which the high thermal conductive layers are joined in the middle of the through hole formed in the low thermal expansion layer can be obtained. In other words, the high heat conductive layer flows from both sides of the through hole into the through hole formed in the low thermal expansion layer by application of high pressure, and the high heat conductive layer is joined in the middle of the through hole.
When cold rolling is applied, cleanliness and flatness that can be used as a composite material for electronic components can be easily obtained.

In the present invention, the low thermal expansion layer made of an Fe—Ni alloy is disposed for the first purpose to reduce the thermal expansion of the heat spreader of the present invention. Preferably, in order to approximate the thermal expansion coefficients of the heat spreader and the semiconductor element, it is desirable to arrange the heat spreaders so that the thermal expansion coefficient at 30 ° C. to 300 ° C. is obtained in the range of 4 to 11 × 10−6 / ° C. Specific examples of the Fe—Ni alloy used include a so-called invar alloy of Fe-42% Ni alloy and Fe-36% Ni alloy;
e-31% Ni-5% Co alloy, so-called Super Invar alloy, Fe-29% Ni-17% Co alloy, etc.
30 to 60%, with the balance Fe or Ni partially substituted with Co as a basic element, can be used.

Further, it is naturally possible to contain other additive elements. In accordance with various requirements such as thermal expansion characteristics and mechanical strength, elements of Group 4A, 5A and 6A are replaced with an austenitic structure which does not impair the low thermal expansion characteristics. It can be added as long as it can be retained. For example, Cr effective for forming an oxide film or the like is 8% by weight or less, and Nb, Ti, Zr, W, Mo, Cu which is 5% by weight or less as an element for improving strength, and an element for improving hot workability. 5% by weight or less of Si, Mn or 0.1% by weight or less of Ca, B, Mg.

In the present invention, the high thermal conductive layer is defined as a Cu-based metal. Pure copper is extremely excellent in terms of thermal conductivity and is effective as a heat sink or heat spreader for which thermal conductivity is important, but depending on the case, mechanical strength, solderability, silver brazeability, heat resistance, etc. It is possible to add an alloy element to improve the characteristics according to the temperature. For example, Sn or Ni can be dissolved in copper or a copper alloy to improve mechanical strength. Ti is N
When added in combination with i, Ni and Ti
Precipitates as a compound with, and improves mechanical strength and heat resistance. Zr improves solder weather resistance. Al,
It is known that Si, Mn, and Mg improve adhesion to a resin. Since the purpose of the present invention is to impart heat dissipation to the copper or copper alloy layer, the above-mentioned additive element for reducing the heat dissipation is preferably 10% by weight or less in the copper alloy.

The Mo-based metal which can be used in the thermal expansion suppressing layer of the present invention may be an alloy mainly composed of pure Mo or Mo, and the W-based metal may be an alloy mainly composed of pure W or W. Is fine. Further, Nb-based metals and Ta-based metals are similarly
A pure metal or a metal alloy may be used. Of course, it goes without saying that the coefficient of thermal expansion α30-800 ° C. must be 7.5 × 10−6 / ° C. or less.

[0037]

Embodiments of the present invention will be described below. As a material for the low thermal expansion layer, an Fe-36% Ni alloy was selected, and cold rolling and annealing were repeated to obtain a 0.32 mm thick Fe-
A Ni-based alloy thin plate was obtained. This Fe-Ni-based alloy is photo-etched to a diameter of 0.5 mm over the entire surface of the thin plate.
Through holes with a 1.065 mm pitch were formed. The ratio of the through holes to the flat surface of the thin plate is about 20% in area ratio. This thin plate is slit into a width of 300 mm, and then a length of 50 mm is cut.
Cut to a fixed length of 0 mm to obtain a low thermal expansion layer material (6) shown in FIG. 4 (b).

Further, pure copper (oxygen-free copper) was selected as a material for high heat conduction, and cold rolling and annealing were repeated to obtain a thickness of 0.1 mm.
A thin plate having a thickness of 25 mm and a thickness of 0.35 mm was obtained. This thin plate is slit into a width of 300 mm and then a length of 500 m
m was cut to a fixed size to obtain a material (7) for a high thermal conductive layer shown in FIG. Further, pure Mo having a coefficient of thermal expansion α30-800 ° C. of 5.85 × 10−6 / ° C. was selected as a material for suppressing thermal expansion, and was 0.2 mm thick and 0.1 mm thick.
mm plate was obtained. These plates were slit to a width of 300 mm, and then cut to a fixed length of 500 mm to obtain a material for a thermal expansion suppressing layer.

Next, these materials were laminated in combinations shown in Table 1. The laminated structure of FIG. 5 is referred to as a laminated structure A, the laminated structure of FIG. 6 is referred to as a laminated structure B, and the laminated structure of FIG. The laminated structure A has a basic structure of a multilayer structure in which three low thermal expansion layers and four high thermal conductive layers are alternately laminated such that a low thermal expansion layer of an Fe-Ni alloy is sandwiched between pure copper high thermal conductive layers. , Placing a thermal expansion suppression layer on both outer sides of this basic configuration,
Further, the laminated structure has a high thermal conductive layer of pure copper disposed outside the thermal expansion suppressing layer. Pure Cu had a thickness of 0.25 mm. In addition, pure Mo as the thermal expansion suppressing layer has a Mo volume ratio of 15.2 in the entire heat spreader by using two types of thicknesses of 0.2 mm and 0.1 mm.
Two types, 0% and 8.1%, were produced.

The laminated structure B is a laminated structure obtained by replacing the low thermal expansion layer of the Fe—Ni alloy located at the center of the basic structure of the multilayer structure in the laminated structure A with a thermal expansion suppressing layer of pure Mo. That is, the thermal expansion suppressing layer included in the laminated structure B has three layers. Pure Cu has a thickness of 0.25 mm, and pure Mo has a thickness of 0.2 mm.
o Volume ratio is 23.0%. The laminated structure C has a basic structure of a multilayer structure in which five low thermal expansion layers and six high thermal conductive layers are alternately laminated such that a low thermal expansion layer of an Fe-Ni alloy is sandwiched between pure copper high thermal conductive layers. , Fe located at its center
-A laminated structure in which a low thermal expansion layer of a Ni-based alloy is replaced with a thermal expansion suppressing layer. That is, the thermal expansion suppressing layer included in the multilayer structure C is one layer. Only pure Cu located on the outermost surface has a thickness of 0.35 mm, and other pure Cu has a thickness of 0.25 mm
It was used. In addition, two types of pure Mo having a thickness of 0.2 mm and 0.1 mm were used to prepare two types of Mo volume ratios of 6.8% and 3.5%.

For comparison of characteristics, a laminated structure D not including a thermal expansion suppressing layer was also implemented. In the laminated structure D, in the basic structure of the multilayer structure of the laminated structure C, the low thermal expansion layer and the high thermal conductive layer are replaced with five layers without replacement with the thermal expansion suppressing layer.
It has a structure in which layers are alternately stacked. Like the laminated structure C,
Only pure Cu located on the outermost surface had a thickness of 0.35 mm, and the other pure Cu had a thickness of 0.25 mm. The Mo volume ratio is 0%.

Six sets of the above-described six kinds of laminates having different thermal expansion suppressing layers and different volume ratios were prepared. In addition, thickness 0.5mm, width 300mm, length 50
A product obtained by applying BN powder to the surface of a SUS304 plate cut to 0 mm was prepared. By using this as a partition for each set of laminates, each set can be easily separated even after the above-described laminates are stacked and subjected to the bonding process at a time under high temperature and pressure.

Next, the laminate and the SUS304 plate coated with BN powder were alternately placed in a 5 mm thick S15C case. In this case, 10 minus 3 Torr
After degassing was performed so as to reduce the pressure more than the pressure was reduced, sealing was performed by welding. The S15C case (hereinafter referred to as “can material”) having the deaerated laminate was held for 3 hours under a pressure of 100 MPa at various temperatures shown in Table 1 using a hot isostatic press. Each layer in the body was joined and integrated. S15C on the upper and lower surfaces of can material after hot isostatic pressing
The case material was removed by grinding, and the laminate was separated one by one by a SUS304 plate coated with the above-mentioned BN powder to obtain a material before rolling. The material before rolling was subjected to cold rolling and annealing to obtain a plate having a thickness of 1 mm.

Next, a sample for measuring thermal conductivity and a sample for measuring thermal expansion were prepared from these plates, and the thermal conductivity and the coefficient of thermal expansion in the plate width direction were measured. The thermal conductivity was measured at room temperature by a laser flash method. The measurement of the coefficient of thermal expansion was performed at 150 ° C (α30-150 ° C) and 300 ° C (α30-
(300 ° C.) and 800 ° C. (α30-800 ° C.). Table 1 shows the measurement results of these characteristics.

[0045]

[Table 1]

As shown in Table 1, the heat spreader according to the present invention was prepared by adjusting the ratio of the thermal expansion suppressing layer.
While having high thermal conductivity of 0 W / mk
Even at a high temperature of 0 ° C., 6.5 to 10.5 × 10−6th power /
It is possible to obtain a low thermal expansion characteristic of about ° C. Especially,
When pure Mo is used as the thermal expansion suppressing layer as in this embodiment, when the volume ratio is 15.0%, α30-800
° C. = 7.9 × 10−6 / ° C., and α30-800 of the alumina ceramic shown as a reference value in Table 1.
A value close to ° C is obtained. Therefore, when a thin, low-strength alumina ceramic is brazed to the heat spreader of the present invention with silver brazing, it is possible to achieve a flat joint without cracking or cracking of the ceramic.

Actually, silver brazing of a 1.5 mm thick alumina ceramic and a 1.0 mm thick heat spreader of the present invention was carried out. The heat spreader was manufactured by punching with a press. A eutectic silver wax (melting point: about 780 ° C.) was used as the silver braze, and was heated to 830 ° C., cooled, and joined. In the case of a heat spreader that does not include a thermal expansion suppressing layer, cracks occur in the ceramic, and the size is 30 mm × 30 m.
m, the amount of warpage of the heat spreader surface reached 250 μm. The product of the present invention, as the thermal expansion suppressing layer, has a volume ratio of 1
In the case of the heat spreader containing 5.0% Mo, there were no cracks or cracks in the ceramic, and the amount of warpage of the heat spreader surface was 30 μm, and bonding with extremely good flatness was realized.

When pure Mo is used as the thermal expansion suppressing layer as in this embodiment, when the volume ratio is 8.1%, α30-800 ° C. = 10.0 × 10−6 power / ° C.
Was obtained, and Kovar (Fe-29% Ni-) shown in Table 1 was obtained.
(17% Co alloy) and a value close to α30-800 ° C. Therefore, when the Kovar material is joined to the heat spreader of the present invention by silver brazing as a semiconductor package application requiring accuracy, a package having a small amount of warpage and excellent flatness can be obtained.

Actually, the thickness is 1.0 mm and the width is 12.7 mm ×
A Kovar frame with a length of 30.5 mm x height of 4.5 mm,
Silver brazing of the heat spreader of the present invention having a thickness of 1.3 mm was performed. The heat spreader was manufactured by punching with a press. A eutectic silver wax (melting point: about 780 ° C.) was used as the silver braze, and was heated to 830 ° C., cooled, and joined. After silver brazing, the amount of warpage in the length direction of the heat spreader surface was measured inside the Kovar frame. In the case of a heat spreader that does not include a thermal expansion suppressing layer, the amount of warpage deformation is 6
It reached 5 μm. In the case of the heat spreader containing Mo having a volume ratio of 8.1% as the thermal expansion suppressing layer according to the present invention,
The amount of warpage was 10 μm or less, and bonding with extremely excellent flatness was realized.

[0050]

According to the present invention, the use of expensive materials is minimized, the coefficient of thermal expansion at high temperatures is small, the thermal expansion of ordinary semiconductors in the temperature range of heat generation is small, and the heat conduction is further improved. A material with good characteristics can be obtained. In addition, the composite material of the present invention is bonded by applying a high pressure during hot as compared with the conventional cold compression-diffusion annealing method. Is greatly improved.

[Brief description of the 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 an example in which the outermost layer of the composite material of the present invention is a thermal expansion suppressing layer.

FIG. 3 is an example in which the outermost layer of the composite material of the present invention is a high heat conductive layer.

FIG. 4 is a view for explaining a material of the composite material of the present invention.

FIG. 5 is an example in which the outermost layer of the composite material of the present invention is a high heat conductive layer.

FIG. 6 is an example in which a thermal expansion suppressing layer is arranged between layers of the composite material of the present invention.

FIG. 7 is an example in which a thermal expansion suppressing layer is arranged between layers of the composite material of the present invention.

FIG. 8 is a configuration example of a PGA package to which the present invention is applied.

[Explanation of symbols]

1 low thermal expansion layer, 2 through hole, 3 high thermal conductive layer, 4 basic structure of multilayer structure, 5 thermal expansion suppressing layer, 6 material for low thermal expansion layer, 7 material for high thermal conductive layer, 8 silicon chip,
9 bonding wire, 10 ceramic substrate, 1
1 heat spreader, 12 pins, 13 silver brazing, 14
Lid

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hideya Yamada 2107-2 Yasugi-cho, Yasugi-shi, Shimane Pref.

Claims (8)

[Claims] 1. A high thermal conductive layer of a Cu-based metal, a low thermal expansion layer of an Fe-Ni-based alloy having a plurality of through holes, and a thermal expansion coefficient α30-800 ° C. of 7.5 × 10−6 / ° C. A heat spreader comprising a thermal expansion suppressing layer made of the following metal. 2. A high thermal conductive layer of a Cu-based metal, a low thermal expansion layer of an Fe—Ni-based alloy having a plurality of through holes, and a thermal expansion coefficient α30-800 ° C. of 7.5 × 10−6 / ° C. A heat spreader comprising a thermal expansion suppressing layer made of the following metal, wherein the thermal expansion coefficient α30−
A heat spreader characterized in that the volume ratio of the thermal expansion suppressing layer made of a metal whose 800 ° C. is 7.5 × 10−6 / ° C. or less is adjusted to 3 to 25%. 3. A high thermal conductive layer made of a Cu-based metal, Fe-Ni
A plurality of low-thermal-expansion layers of the system alloy are alternately or continuously laminated, and the high-thermal-conductivity layer sandwiching the low-thermal-expansion layer is a heat spreader that is continuous through a plurality of through holes formed in the low-thermal-expansion layer, At least one of the layers of the heat spreader, the surface on which the heat-dissipating component is mounted and the opposite surface on which the heat-dissipating component is mounted has a coefficient of thermal expansion α30−
A heat spreader comprising a thermal expansion suppressing layer made of a metal having a temperature of 800 ° C. of 7.5 × 10−6 / ° C. or less. 4. The heat spreader according to claim 1, wherein the thermal expansion suppressing layer is at least one of a Mo-based metal and a W-based metal. 5. The heat spreader according to claim 1, wherein a Cu-based metal layer is formed on an outermost layer. 6. A semiconductor device comprising a semiconductor chip mounted on the heat spreader according to claim 1. 7. A thin plate of a Cu-based metal and a plurality of Fe-Ni-based alloy thin plates having a plurality of through holes are alternately or continuously laminated, and at least one of the interlayer and the outside has a thermal expansion coefficient α30. A thermal expansion suppression layer made of a metal having a temperature of −800 ° C. or lower than 7.5 × 10 −6 / ° C. is disposed, and after filling in a can body, the pressure is reduced to a pressure lower than 10 −3 Torr, and then sealing is performed. In a temperature range of 〜１０1050 ° C., a bonding treatment is performed by applying a pressure of 50 MPa or more, a Cu-based metal is filled in the through hole, and the respective layers are bonded, and then finished to a predetermined thickness by rolling. Heat spreader manufacturing method. 8. A thin plate of a Cu-based metal and a plurality of thin sheets of an Fe—Ni-based alloy having a plurality of through holes alternately or continuously laminated, and a thermal expansion coefficient α30 is provided at least in one of the layers and the outside. After placing a thermal expansion suppressing layer made of a metal having a temperature of −800 ° C. or less than 7.5 × 10 −6 / ° C. or less, further placing a Cu-based metal on the outermost layer and filling the can body,
Sealing after reducing the pressure to less than 0 minus the third power Torr,
Then, in a temperature range of 700 to 1050 ° C., 50MP
a to perform a bonding process by applying a pressure of at least
A method for manufacturing a heat spreader, comprising filling and joining a base metal, and then finishing to a predetermined thickness by rolling.