JPH10163600A - Heat dissipation flexible adhesive composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To radiate generated heat and to alleviate a stress, generated simultaneously in assembling a semiconductor device by using a validating flexible adhesive composite material impregnated with a flexible adhesive in high thermal conductive electric insulating cloth. SOLUTION: A semiconductor chip 1 is connected to a substrate electrode 5 via a bump 10 and simultaneously fixed to a circuit board 2. An entire apparatus is sealed by a resin layer 9. The radiating flexible adhesive composite material 22 is mounted on the chip 1. The material 22 is obtained by impregnating a woven fabric of alumina fiber with silicone adhesive. Accordingly, by having a semiconductor device reduced in size for being effective effectively radiating heat generated from the chip 1. Further, the heat from the chip 1 generates a stress in the device, so that when the material is used, heat radiation is expedited, contributing to alleviation of stresses.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-radiating flexible adhesive composite used for processing a semiconductor, particularly a high-density surface-mount type highly integrated semiconductor. More specifically, the present invention relates to a heat dissipating flexible adhesive composite used when processing a high-density surface mount type semiconductor, which further has a function of dissipating heat in addition to the properties of adhesiveness and stress relaxation.

[0002]

2. Description of the Related Art The electronics industry has undergone significant development, and various electronic devices have entered factories, offices or homes. There is a strong demand for small, high-performance and low-cost electronic devices.

In order to cope with this, semiconductor devices are becoming more highly integrated and packages are becoming lighter and smaller. On the other hand, the substrate mounting method has shifted to surface mounting in which the entire semiconductor surface rises to the solder melting temperature. In the surface mounting, the stress applied to the semiconductor element at the time of soldering becomes very large. Further, when moisture is contained in a resin composition or the like for encapsulating a semiconductor, the moisture evaporates due to the high temperature of the solder and generates high pressure, which makes the function of the semiconductor device insufficient and further reduces the It can also cause equipment damage. Against this background, there is a strong demand for a technology for dramatically improving the reliability of a semiconductor device.

In response to demands for small, high-performance and low-cost semiconductor devices, there is a processing method called a flip chip bonding in which a semiconductor bare chip is directly attached to a substrate. Compared to wire bonding, which has conventionally been the mainstream of semiconductor device processing, flip chip bonding has a feature that a product, that is, a semiconductor device can be reduced in size. However, in order to perform high-density mounting, it is necessary to increase the wiring density on the substrate. In this regard, a CSP (chip size package) in which electrodes are arranged in a plane has an advantage that the mounting area can be made substantially equal to that of a single chip due to a normal wiring density.

On the other hand, when assembling a semiconductor device, resin sealing is generally performed to absorb stress during processing and to protect the semiconductor from the outside. The purpose is to alleviate the stress caused by the difference in thermal expansion during processing between the semiconductor chip and the substrate with the resin. At present, epoxy resin compositions are mainly used as sealing resins for semiconductor devices. Various ideas have been devised for the resin composition, and many patents have been filed.

However, in miniaturizing a semiconductor device,
It has already come to a point where improvement of the resin composition alone is not sufficient. That is, it has become necessary for resin compositions to satisfy mutually conflicting requirements. For example,
Silicone rubber alone is effective in relieving stress, but when used in combination with an epoxy resin, the adhesion between the silicone rubber and the epoxy resin deteriorates, resulting in joint defects. As a result, the performance of the semiconductor device becomes insufficient or the semiconductor device is destroyed. There is also a method of mixing inorganic fine particles such as silica with the elastomer, but when such inorganic fine particles are mixed with the elastomer,
Elasticity, which is a characteristic of the elastomer, is lost, and as a result, stress during semiconductor processing cannot be sufficiently reduced. Further, the resin to be used is required to have elasticity, that is, flexibility, and is required to have confidentiality, conductivity, heat dissipation, or deaeration. Various studies have been made to solve these problems, but at present, no effective method has been found yet.

As semiconductor devices become lighter and thinner, how to dissipate heat generated by the semiconductor itself has become a problem. Since the mounting density of the semiconductor chip is increased by reducing the size and weight of the semiconductor device, heat generated from the semiconductor is not easily diffused, and the temperature of the device itself is increased. This high temperature generates thermal stress, which has a great effect on the reliability of the semiconductor device.

[0008]

As described above, in order to manufacture a small, high-performance, and low-cost semiconductor device, it is necessary to satisfy mutually contradictory requirements. The present invention solves these problems and is intended to assemble a small, high-performance and low-cost semiconductor device.
An object of the present invention is to provide a heat dissipating flexible adhesive composite in which a flexible adhesive is impregnated into a high heat conductive and electrically insulating cloth.

The inventor of the present invention has determined that it is difficult to satisfy the demands of the semiconductor device only by improving the resin composition by the conventional method, and uses a flexible material having sufficient performance for stress relaxation. By giving heat dissipation to the flexible material, it is thought that an effect that has not existed before can be realized,
The present inventors completed the present invention after diligently studying a heat-radiating flexible adhesive composite in which a flexible adhesive is impregnated into a cloth having high thermal conductivity and electrical insulation during processing of a semiconductor device.

[0010]

SUMMARY OF THE INVENTION The gist of the present invention is a heat-dissipating flexible adhesive composite used for directly mounting a semiconductor element on a circuit board, wherein the flexible adhesive is attached to a high heat conductive and electrically insulating cloth. Is a heat-radiating flexible adhesive composite, characterized by being impregnated with.

Examples of the high heat conductive and electrically insulating cloth include ceramic fibers, fibers obtained by introducing or coating a high heat conductive and electrically insulating substance to organic fibers to impart heat radiation, and fibers obtained by insulating conductive fibers. And at least one selected from the group consisting of woven fabric, knitted fabric, nonwoven fabric, and the like. Further, as the adhesive, for example, an elastomeric adhesive having flexibility can be used.

Conventionally, a stress generation suppression method and a stress relaxation method have been adopted as stress relaxation methods. The stress generation suppression method
This method is intended to reduce the thermal expansion by highly filling spherical silica with excellent fluidity.However, when spherical silica is used, interface delamination occurs, causing problems such as reduced strength and water penetration corrosion. This is a method of lowering the elastic modulus by using excellent silicone. However, since silicone has an extremely weak adhesive force, it is difficult to adhere to an epoxy resin, and the resulting semiconductor device has a problem of a decrease in strength and water penetration corrosion.

The present invention is characterized in that a high heat conductive and electrically insulating cloth having heat dissipation properties is used as a stress relieving material, and at the same time, a flexible adhesive is used. Rather than mixing an inorganic or flexible substance into the sealing resin of the prior art, the present invention is based on a completely different technology.

The highly heat conductive and electrically insulating cloth used in the present invention can be obtained from a woven fabric, a knitted fabric, a nonwoven fabric, or the like of a fiber having high heat conductivity and electric insulation. Ceramic fibers are known as high heat conductive and electrically insulating fibers. In addition, high heat conductive and electrically insulating fibers
It can be obtained by mixing and introducing a thermoconductive and electrically insulating substance such as ceramics into organic fibers, or by coating organic fibers. Further, it can also be obtained by insulating the conductive fiber.
In addition, the high heat conductive and electrically insulating cloth is such that a high heat conductive and electrically insulating cloth is placed on the side where insulation is required, and a high heat conductive and electrically insulating cloth is formed on a high heat conductive cloth such as a metal fiber cloth. It may be a laminated composite.

[0015] Ordinary organic fibers can be produced by a melt spinning method, a dry spinning method or a wet spinning method.
Various methods are employed for ceramic fibers depending on the type. There are a method of melt spinning, a method of heat treatment after wet spinning, a method of first forming a filament in a precursor state, and performing a heat treatment. For example, silica fibers can be obtained by spinning an aqueous solution of water glass into an acidic bath and subjecting the resulting yarn to heat treatment. Further, carbosilane obtained by converting dimethylchlorosilane to polysilane by dechlorination and further heat-transferring the same is dry-spun and then heat-treated to produce carboxycarbon fibers.

Alumina fiber is obtained by adding a polyethylene oxide or the like to an aqueous solution of aluminum salt of acetic acid to impart viscosity, adding a keiso compound, extruding from a nozzle to form a thread, firing at a high temperature, and forming a viscous slurry comprising alumina, magnesium chloride, or the like. Spinning and firing at high temperature, or (A
1R—O) _n (R is an alkyl, alkoxy, organic acid group, etc.) polymer can be obtained by dissolving the polymer in an organic solvent, spinning and firing at a high temperature. Further, the zirconia fiber can be obtained by immersing a polymer fiber or a woven fabric in a solution obtained by adding yttrium chloride to a zirconium chloride solution, followed by drying and firing.

Next, the method of ceramic coating will be described. As a basic method of coating,
Physical vapor deposition called PVD and chemical vapor deposition called CVD are known. PVD further includes methods such as vacuum deposition, ion plating, and sputtering. Vacuum vapor deposition and ion plating are methods in which vapor-deposited particles are created by heating in a vacuum and deposited on the surface of a low-temperature deposition target. At this time, the deposited particles are neutral in vacuum deposition, but are partially ionized in ion plating. In sputtering, a vacuum is filled with an argon gas, a cathode is made into a substance to be sputtered, and a high voltage is applied using an anode as an object to be deposited to form a thin film. CVD
Is to form a thin film by introducing a raw material gas into a reactor and causing a chemical reaction in a gas phase or on a surface of an object to be deposited.

The present invention is characterized in that the above-mentioned highly heat conductive and electrically insulating cloth is impregnated with a flexible adhesive. The adhesive used here is preferably an elastomeric adhesive or the like. That is, it is an adhesive based on silicone, natural rubber, synthetic rubber, elastomer or the like. Specifically, a silicone adhesive, a chloroprene rubber adhesive, a nitrile rubber adhesive, an SBR rubber adhesive, a butyl rubber adhesive, a polyolefin rubber adhesive, a polyester elastomer adhesive, or the like can be used. These adhesives may have functions such as thermal conductivity and electrical insulation as required.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a semiconductor device using the heat dissipating flexible adhesive composite of the present invention will be specifically described. Before that, an example of a flip-chip type semiconductor device is shown in FIG. In this case, the semiconductor chip 1
The bump 10 is connected to the substrate electrode 5 and is fixed to the circuit board 2. The bumps 10 serve to bond the semiconductor chip to the circuit board and to connect to the board electrodes. For protection of the semiconductor device, the semiconductor chip is sealed with a resin layer 8.

FIG. 2 shows an example of an embodiment using the heat-releasing flexible adhesive composite of the present invention. The heat dissipating flexible adhesive composite 4 of the present invention is mounted between the substrate electrode 5 and the semiconductor chip electrode 3. The heat-radiating flexible adhesive composite 4 is obtained by impregnating a cloth obtained from alumina fiber with SEBS which is a block elastomer made of styrene, ethylene, butylene and the like. A hole is formed in the heat-releasing flexible adhesive composite 4, and a bump 10 is mounted thereon. By subjecting the three members of the heat dissipating flexible adhesive composite 4 on which the semiconductor chip and the bump are mounted and the substrate electrode 5 to heat treatment under pressure, a semiconductor device in which the three members are integrated can be obtained. In addition, there is no problem if the whole is separately sealed with epoxy resin or the like.

Since the heat-radiating flexible adhesive composite has an adhesive property, it is located between the substrate and the semiconductor chip and adheres to the substrate and the semiconductor chip. From the viewpoint of conductivity, the bump plays a role, and the heat-releasing flexible adhesive composite plays a role of fixing the semiconductor chip to the substrate and as a stress relieving material. The heat dissipating flexible adhesive composite has flexibility and heat dissipating properties, and thus effectively acts on heat dissipation as well as stress relaxation.

As described above, in mounting a semiconductor device, high performance, miniaturization and low cost are required. From this viewpoint, a CSP (chip size package) in which electrodes are arranged in a plane has a feature that a mounting area can be made substantially equal to that of a single chip, and is attracting attention as a mounting method. In this CSP, for example, as shown in FIG. 3, the number of electrodes or pins 42 of the semiconductor chip is large. A hole is formed in a place on the insulating cloth corresponding to the position of the pin, a bump is provided, and the semiconductor chip and the circuit board are pressure-bonded by sandwiching the heat-radiating flexible adhesive composite having the bump provided thereon. Thus, a highly mounted semiconductor device can be efficiently obtained.

FIG. 4 shows another embodiment using the heat-releasing flexible adhesive composite of the present invention. The semiconductor chip 1 is connected to the substrate electrodes 5 by bumps 10 and is fixed to the circuit board 2 at the same time. The entire device is sealed with a resin layer 8. The heat dissipating flexible adhesive composite 22 of the present invention is mounted on the semiconductor chip 1. Heat dissipation flexible adhesive composite 22
Is obtained by impregnating a woven cloth made of alumina fibers with a silicone adhesive. With the miniaturization of semiconductor devices, treatment of heat generated from semiconductor chips has become a problem. That is, it is necessary to efficiently radiate the heat generated from the semiconductor chip. The embodiment of FIG. 4 is useful for efficiently dissipating heat generated from such a semiconductor chip. Further, since heat generated from the semiconductor chip generates stress in the semiconductor device, the use of the heat dissipating flexible adhesive composite of the present invention promotes heat dissipation and contributes to stress relaxation.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.

Embodiment 1 In the embodiment of FIG. 4, a semiconductor chip 1 is connected to a substrate electrode 5 by bumps 10 and is simultaneously fixed to a circuit board 2. The entire device is sealed with a resin layer 8. The heat dissipating flexible adhesive composite 22 of the present invention is mounted on the semiconductor chip 1. The heat-radiating flexible adhesive composite 22 is obtained by impregnating a woven fabric made of alumina fiber with a silicone adhesive. Here, an adhesive (product number SE1816CV) manufactured by Dow Corning Toray Silicone Co., Ltd. was used as the silicone adhesive. The performance of the manufactured semiconductor device was evaluated by a simulation test. The number of generated cracks was 0/20, which was a good result. Evaluation conditions are as shown below. Evaluation conditions: 1) Performance evaluation size Size of the simulated IC: Outer dimensions 10 × 10 × 0.5 mm, pad dimensions: 100 μm □ 2) Circuit board: FR-4 (Toshika Kogyo), single-sided copper foil, partial gold plating 3) Moisture absorption , Solder test The condition of PCT moisture absorption (125 ° C * 100% * 20 hrs) + solder erosion (260 ° C * 10 sec) was repeated five times. The evaluation results were expressed as the number of cracks (> 50 μm) after treatment as the number of cracks out of 20 samples as the number of cracks.

[0025]

Second Embodiment In the embodiment shown in FIG. 4, the semiconductor chip 1 is connected to the substrate electrode 5 by bumps 10 and is fixed to the circuit board 2 at the same time. The entire device is sealed with a resin layer 8. The heat dissipating flexible adhesive composite 22 of the present invention is mounted on the semiconductor chip 1. The woven fabric obtained from the stainless steel fiber was immersed in a zirconium chloride solution, dried and heat-treated to obtain a woven fabric coated with zirconia. SEBS made by Shell Japan Co., Ltd.
Impregnated with an elastomer of the structure (Part No. G1726)
The heat-releasing flexible adhesive composite was obtained. The performance of the manufactured semiconductor device was evaluated by a simulation test in the same manner as in Example 1. The number of generated cracks was 0/20, which was a good result. This indicates that not only the thermal stress at the time of assembling the semiconductor device but also the effect of effectively reducing the stress due to the heat generated from the semiconductor chip during use of the semiconductor device is obtained.

[0026]

Comparative Example 1 The use of alumina powder instead of the alumina fiber of Example 1 was examined. That is, a silicone adhesive manufactured by Toray Dow Corning Silicone Co. (product number SE1)
816CV) and alumina powder were mixed and cured,
The semiconductor device was not obtained without curing.

[0027]

Comparative Example 2 The use of alumina powder instead of the zirconia-coated stainless steel woven fabric of Example 2 was examined. That is, an elastomer having an SEBS structure (product number G1726) manufactured by Shell Japan Co., Ltd. and alumina powder were mixed under heating to obtain a heat-radiating adhesive. In the embodiment shown in FIG. 4, this heat dissipating adhesive is used as a heat dissipating plate on a semiconductor chip. In this example, a performance test was performed in the same manner, and the number of cracks was 18/20.
The occurrence of defective products was high. This is because the introduction of the alumina powder increased the hardness of the elastomer and could not alleviate the stress.

[0028]

Comparative Example 3 In Example 2, a zirconia plate was used instead of a woven fabric obtained from stainless steel fibers treated with zirconia. When a performance test was performed in the same manner in this comparative example, the number of cracks was 2
Cracks were observed in all 20 samples on 0/20. This is because the heat radiation plate made of only zirconia has no flexibility, so that the stress generated by heat cannot be reduced.

[0029]

According to the present invention, a semiconductor device is assembled by using a heat dissipating flexible adhesive composite in which a flexible adhesive is impregnated into a highly heat conductive and electrically insulating cloth, thereby dissipating generated heat and reducing a stress generated at the same time. Can be eased. Further, since the heat-radiating flexible adhesive composite has adhesiveness, a small, high-performance and low-cost semiconductor device can be easily assembled.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a flip chip bonding method.

FIG. 2 is a diagram illustrating an example of an embodiment;

FIG. 3 is a diagram showing an example of an arrangement state of electrodes of a CSP.

FIG. 4 is a diagram showing an example of an embodiment used as a heat sink.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor chip 2 Circuit board 3 Semiconductor chip electrode 4, 22 Heat dissipation flexible adhesive composite 5 Board electrode 8 Resin layer 10 Bump 42 pin

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 23/28 G11C 11/34 H05K 3/34 505 H01L 23/14 R

Claims (3)

[Claims] 1. A heat-dissipating flexible adhesive composite used when a semiconductor chip is directly mounted on a circuit board, wherein a highly heat-conductive and electrically insulating cloth is impregnated with a flexible adhesive. Flexible adhesive composite 2. A high heat conductive / electrically insulating cloth is made of ceramic fiber, organic fiber, or a fiber obtained by introducing or coating a high heat conductive / electrically insulating substance to impart heat radiation, and a fiber obtained by insulating a conductive fiber. 2. The heat-dissipating flexible adhesive composite according to claim 1, wherein at least one selected from the group consisting of a woven fabric, a knitted fabric, and a non-woven fabric obtained from the main component is used as a main component. 3. The heat-radiating flexible adhesive composite according to claim 1, wherein the adhesive comprises a flexible elastomeric adhesive.