JP2003261833A - Thin filmy adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a filler-containing thin insulating filmy adhesive material which has high thickness accuracy and positioning accuracy, reduces voids and, in addition, inhibits the stress to be generated on joining different types of substances such as joining of a semiconductor chip to a lead frame or a circuit substrate and on joining a chip to a chip in forming a stacked structure of making overlapping two or more semiconductor chips in a package and, simultaneously, excels in adhesion workability. <P>SOLUTION: The thin filmy adhesive has a film thickness of ≤60 μm, and comprises 100 pts.wt. resin containing 10-50 wt.% thermoplastic resin and 50-90 wt.% thermosetting resin such as an epoxy resin and its curing agent and 150-300 pts.wt. silica, and the above silica is a mixture of (b1) silica having an average particle diameter of 3-10 μm and (b2) fine particle silica having an average particle diameter of 0.1-2 μm, and the maximum particle diameter of the silica is ≤0.8T of the film thickness T. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film-like adhesive, and more specifically, a thin insulating film-like adhesive suitable for joining a semiconductor chip to a lead frame or a circuit board and a semiconductor chip to a semiconductor chip. It is related to agents.

[0002]

2. Description of the Related Art DIP (Dual In-line Package), SOP
(Small Outline Package), QFP (Quad Flat Package)
, BGA (Ball Grid Array), CSP (Chip Sized Pack)
Among the materials constituting the semiconductor package represented by age), the Au-Si eutectic alloy, solder, silver paste, etc. have been conventionally used as the die bonding material for bonding the semiconductor chip to the lead frame or the circuit board. . Currently, for general-purpose and large-sized packages, adhesion with silver paste has become the mainstream from a comprehensive judgment of productivity, heat dissipation, large chip applicability, price, and the like. Silver paste can be applied to the lead frame or circuit board by the dispense method, and can easily perform temporary pressure bonding of the semiconductor chip, which shows excellent productivity.On the other hand, because it is a liquid, the adhesive thickness accuracy, application position accuracy and voidless control can be controlled. There was a problem that it was difficult.

In recent years, an area array type chip size package has been introduced, which greatly contributes to the miniaturization of portable equipment. However, in such a package, the size of the semiconductor chip and that of the package are infinitely close to each other. Therefore, a minimum area is required for the fillet area when the semiconductor chip is bonded to the lead frame and the circuit board, and the chip bonding surface is completely At the same time, it is required to be covered with an adhesive layer. Further, since the voids inside the formed adhesive layer have a great influence on the moisture resistance reliability and the package crack, it is preferable that the voids are void-free.
From the above circumstances, the demand for adhesives with higher positional accuracy is increasing, and while maintaining the productivity of conventional pasty adhesives, there is a demand for film adhesives that have high thickness accuracy and positional accuracy and are less likely to cause voids. It was being done. In addition, when an area array type semiconductor package is mounted on a mother board and then evaluated to accelerate damage due to stress, such as in a temperature cycle test, the difference in the coefficient of linear expansion between the package constituent material and the joint part with the mother board material is different. Since there is also a problem of being destroyed by the stress generated at 1, the adhesive that suppresses the stress caused by the difference in linear expansion coefficient of different materials to be joined is also required.

On the other hand, as an adhesive composition used for a film adhesive, JP 2001-49220 A describes an adhesive composition containing silica, a phenoxy resin, a glycidyl ether type epoxy resin and an epoxy resin curing agent as essential components. ing. However, with the film-like adhesive described here, when the sheet thickness is about 60 μm, the presence of particulate foreign matter is confirmed on the sheet surface. Such particulate foreign matter deteriorates the thickness accuracy of the film and may cause chip damage when the semiconductor chip is bonded to the lead frame, the circuit board and the like.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to bond a semiconductor chip to a lead frame or a circuit board in addition to having a film-like adhesive property that has high thickness accuracy and positional accuracy and minimizes the occurrence of voids. Suppresses the stress generated at the time of joining different kinds of materials like this, or even in the adhesion between the same kind of material between chips, excellent temporary pressure bonding property,
An object of the present invention is to provide an insulating film adhesive having a thickness of 60 μm or less in which no surface foreign matter is present.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors, when a film-like adhesive containing silica having a thickness of 60 μm or less was prepared, silica was used as a specific silica mixture and the maximum particle size was changed. With respect to the film thickness T, 0.
It has been found that 8T or less is effective for solving the above problems, and has completed the present invention.

That is, the present invention is a thin film having a thickness of 60 μm or less formed from a thermosetting resin composition prepared by mixing 150 to 300 parts by weight of silica (B) with 100 parts by weight of a resin component (A). In film adhesives, resin content
(A) contains 10 to 50% by weight of a thermoplastic resin, 50 to 90% by weight of a thermosetting resin or a thermosetting resin and a curing agent, and silica (B) is a silica (b1) having an average particle size of 3 to 10 μm. ) And fine particle silica (b2) having an average particle diameter of 0.1 to 2 μm, and the maximum particle diameter of silica (B) is 0.8 T or less with respect to the film thickness T. It is an adhesive. In the above thin film adhesive, silica (b1) and silica (b2) are spherical silica,
The weight ratio is preferably 95/5 to 50/50.
Further, it is also preferable that the resin component (A) is 30 to 60% by weight of the epoxy resin (a1), 10 to 50% by weight of the thermoplastic resin (a2) and 30 to 50% by weight of the epoxy resin curing agent (a3).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The type of silica (B) used in the present invention is not particularly limited, and crushed or spherical fused silica powder is exemplified. Preferred is spherical silica. Silica is at least silica (b) having an average particle size of 3 to 10 μm.
2) of 1) and fine particle silica (b2) with an average particle size of 0.1 to 2 μm
It is a mixture having the average particle size of the seeds. The maximum particle size of the silica (B) needs to be 80% or less with respect to the thickness T of the adhesive film to be produced. Film thickness
When silica having a maximum particle size of 80% or more with respect to T is used, when a film is formed, particulate foreign matter begins to be generated on the surface thereof. Therefore, the maximum particle size of silica used must be 0.8 T or less. Here, the average particle diameter means the median diameter by the number average particle diameter,
The maximum particle size means that substantially all (99.9% or more) is below that size. In the measurement of the particle size of silica, a part of the silica to be used will be measured as a sample for measurement, but the measurement results of most of the randomly sampled samples will meet the above requirements and definitions. Just fill.

The average particle size of silica (B) in the present invention is not limited to the measuring method. That is, as long as it is a known particle size measuring method such as a microscopic method, a sedimentation method, a light transmission method and a light scattering method, any measured value thereof is within the scope of the present invention as long as it is within the range specified by the present invention. Is. Similarly, the maximum particle size is not limited to the measuring method.

The total amount of silica used in the adhesive should be as large as possible in order to reduce the linear expansion coefficient.
It is necessary that the amount of silica (B) is 150 to 300 parts by weight with respect to 100 parts by weight. If the silica content exceeds 300 parts by weight, the viscosity of the composition increases due to the lack of a resin component that functions as a binder, resulting in a brittle film-like adhesive, which significantly reduces the provisional pressure-bonding performance. If the silica content is less than 150 parts by weight, the coefficient of linear expansion cannot be sufficiently reduced, and the effect of suppressing the stress between the semiconductor chip and the lead frame and the circuit board is small, which is not preferable. For example, a temperature cycle test (-65 to 1 after assembled into a package)
In some cases, it cannot withstand the stress generated at the time of 50 ° C.

It is necessary that the resin component (A) contains a thermoplastic resin, and the thermoplastic resin is 10 to 50% by weight, and the thermosetting resin or the thermosetting resin and the curing agent are 50 to 90% by weight. It is contained. Preferred resin composition is epoxy resin (a1), thermoplastic resin (a2) and epoxy resin curing agent (a
It is composed of 3).

The preferred epoxy resin (a1) is a glycidyl ether type epoxy resin, which can be used alone or as a mixture of two or more. Glycidyl ether type epoxy resins that can be used include phenol novolac glycidyl ether type, orthocresol novolac glycidyl ether type, fluorene bisphenol glycidyl ether type, triazin glycidyl ether type, naphthol glycidyl ether type, naphthalene diol glycidyl ether type, triphenyl glycidyl ether type. Examples of the epoxy resin include tetraphenyl glycidyl ether type, bisphenol A glycidyl ether type, bisphenol F glycidyl ether type, bisphenol AD glycidyl ether type, bisphenol S glycidyl ether type, and trimethylolmethane glycidyl ether type. Among these, those having two or more glycidyl ether groups in the molecule are preferable.

Examples of the thermoplastic resin (a2) include thermoplastic resins such as phenoxy resin, polycarbonate resin and polystyrene resin. Among these, a phenoxy resin is preferable because it has a good compatibility and a good adhesiveness because it has a structure similar to that of an epoxy resin. When using a phenoxy resin, a known phenoxy resin can be used. The preferred molecular weight range of the phenoxy resin used is 10,000 in terms of weight average molecular weight.
Above, especially in the range of 30,000 to 70,000. The preferred phenoxy resin has a main skeleton of bisphenol A type, but other commercially available phenoxy resins such as bisphenol A / F mixed type phenoxy resin and brominated phenoxy resin are preferred.

As the epoxy resin curing agent (a3), general-purpose curing agents such as amines, acid anhydrides and polyhydric phenols and latent curing agents can be used. Examples of the latent curing agent include dicyandiamide, imidazoles, hydrazides, boron trifluoride-amine complex, amine imide, polyamine salt and modified products thereof, and microcapsule type ones. In particular, a latent curing agent that exhibits curability at a predetermined temperature equal to or higher than room temperature, for example, a temperature equal to or higher than the temperature at which the resin component exhibits the necessary adhesiveness, and exhibits rapid curability is preferable. By using a latent curing agent, it is possible to provide a composition for a film adhesive having high storage stability, which enables long-term storage at room temperature. The epoxy resin curing agent can be used alone or in combination of two or more kinds.

The preferred blending ratio of each of the components (a1) to (a3) in the resin component (A) is 30 to 60% by weight of the epoxy resin (a1), 10 to 50% by weight of the thermoplastic resin (a2) and epoxy. The resin curing agent (a3) is 20 to 50% by weight. Considering film characteristics such as flexibility, adhesiveness and handling property as a film adhesive, the epoxy resin and the thermoplastic resin are preferably in the above range. If the amount of each component is not within the above range, phase separation during varnishing and deterioration of adhesive strength and tackiness during filming occur, and in the case of a cured product, a desired strength and elastic modulus can be obtained. Absent.

The above composition may contain other additives such as a coupling agent, a leveling agent, an antioxidant, a flame retardant, a coloring agent and a butadiene rubber or a silicone rubber as a stress relaxation agent. It is possible.

Coupling agents are preferred for the purpose of reinforcing the interface with silica, exhibiting high breaking strength, and improving the adhesive strength. The coupling agent preferably contains an amino group and an epoxy group.

The film adhesive of the present invention is, for example, an aromatic hydrocarbon such as toluene or xylene, a ketone type such as methyl isobutyl ketone (MIBK) or methyl ethyl ketone (MEK), or an ether type such as monoglyme or diglyme, alone or as a mixture. A varnish obtained by mixing the above resin component and silica is applied to a release-treated base material (protective film) such as PP, PE, PET, etc., subjected to a heat treatment at a temperature not higher than the curing start temperature of the resin mixture, and dried. Can be obtained at. Here, by allowing the varnish to stand under a certain condition after being prepared, it is possible to improve the familiarity of the interface between the filler and the resin. Specifically, first, prepare a resin varnish that is a mixture of epoxy resin, epoxy resin curing agent, thermoplastic resin, silica and solvent,
Knead. The kneading can be performed at room temperature using any kneading means such as a three-roll. Then 1 in a closed container
It is preferable to let it stand for 5 days or more under refrigerated conditions (10 ° C. or less). Then, the resin varnish thus prepared can be used as a raw material for forming an adhesive film by adding a curing catalyst and other additives as necessary. The thickness of the film adhesive of the present invention is 60 μm or less, preferably 20 to 60 μm.

The film adhesive of the present invention is not limited to the one obtained by preparing the resin component (A) and silica (B) in advance and mixing them. For example, the component constituting the resin component (A) and the component constituting the silica (B) or other additives may be mixed at once to form an adhesive, or may be mixed at least twice to form an adhesive. Well, when mixing two or more times, they may be mixed in any order. Further, an adhesive may be prepared by previously mixing a part of the component constituting the resin component (A) and a part of the component constituting the silica (B). Further, the film adhesive of the present invention may contain the above-mentioned additives and solvent in addition to the resin component (A) and silica (B), but is a solid (a component that remains after drying or curing. It is advantageous that the resin component (A) and silica (B) are contained in the solvent (excluding the solvent) in an amount of 95 wt% or more, preferably 98 wt% or more.

The film adhesive of the present invention is used in various applications and can be used in various usages, but is suitable for the following usages. For example, when bonding a chip or the like to a substrate, first, a film adhesive cut into a predetermined shape and size is placed at a predetermined position on the substrate, heated to 50 ° C. or higher, and heated to 50 to 500 kPa · Gauge. Apply pressure to temporarily press-bond. At this time, the shape and size of the film should not change as much as possible. The film adhesive has almost no tackiness at room temperature and preferably exhibits tackiness at 50 ° C. or higher, but is temporarily pressure-bonded at the curing temperature or lower. Pressure is required to prevent the generation of voids, but if it is too high, the film may be deformed. After temporarily pressure-bonding the film adhesive, peel off the protective film on the surface side, put the chip on this and perform temporary pressure bonding, cure the film adhesive,
The substrate and the chip are completely bonded via the cured film adhesive. Curing is performed by applying heat at the curing temperature or higher. The term “excellent temporary pressure-bonding property” as used herein means that the film-like adhesive is less deformed, that voids are less likely to occur, and that a predetermined adhesive strength is produced by the adhesive force.

[0021]

EXAMPLES The present invention will be described below based on examples.
The silica (B) used in the examples was the following spherical silica. The values of the average particle diameter and the maximum particle diameter are values obtained by the light scattering method. Silica C: Spherical silica silica with an average particle size of 5.0 μm and maximum particle size of 24 μm or more D: Fine particle spherical silica silica with an average particle size of 0.5 μm and maximum particle size of 0.6 μm E: Spherical silica silica F with an average particle size of 6 μm and maximum particle size of 48 μm : Spherical silica with an average particle size of 17 μm and maximum particle size of 48 μm

Example 1 As a thermosetting resin component, 28 g of Epicoat 828 (bisphenol A type epoxy resin; manufactured by Japan Epoxy Resin Co., Ltd.), ZX-10
59 (Equivalent mixture of bisphenol A type and bisphenol F type epoxy resin; manufactured by Tohto Kasei Co., Ltd.) 27 g, PKHP-200 (weight average molecular weight 5
16 g of 8000 phenoxy resin (manufactured by Inchem) was prepared, and 40 g of MIBK was used as a solvent together with this resin component in a flask to heat and stir at 140 ° C. for 2 hours to obtain a resin varnish. In addition, 47 g of SN-170 (phenolic resin; manufactured by Nippon Steel Chemical Co., Ltd.) was charged and melted at 100 ° C., and then 2
3.5 g of MIBK was added and the mixture was stirred at 100 ° C. for 1 hr to obtain a resin solution. The total amount of the resin solution and the resin varnish was charged into a planetary mixer, and 256 g of silica C and 28.5 g of silica D were added and mixed with stirring. Next, this was further kneaded with a three-roll mill. To this mixture, 1 g of a microcapsule type imidazole-based latent curing agent was added, and the mixture was stirred and mixed by a planetary mixer, followed by vacuum degassing to obtain a mixed varnish (method A). After coating the mixed varnish produced by the above method A on a PET film having a thickness of 50 μm and subjected to a mold release treatment, it is dried with hot air (80 ° C .: 16 minutes and 150 ° C .: 1 minute) to obtain 50 μm.
An m-thick adhesive sheet, that is, a film adhesive was obtained.

The film properties were evaluated by observing the surface condition of the adhesive film, the flexibility and the brittleness which are indicators for handling, and evaluated in four grades of ⊚ good, ∘ somewhat good, Δ slightly bad, and × bad.

As an alternative to the above method A, after kneading with three rolls, 15 to 2 is used for the purpose of improving the familiarity between the resin and the filler.
An experiment was carried out to obtain a mixed varnish by refrigerating and storing for 0 days, then adding a latent curing agent and stirring and mixing with a planetary mixer as in the method A, and then degassing in vacuum to obtain a mixed varnish (method B). The following example is an example in which a film-like adhesive was produced and evaluated in the same manner as in Example 1 except that the type of silica, the film thickness or the method A and the method B were changed.

Example 2 An adhesive sheet was produced in the same manner as in Example 1 except that the method B was used, silica C and silica D were used as silica, and the mixture was kneaded for 3 rolls and then kept refrigerated for 15 days. ,evaluated.

Example 3 Using silica C and silica D as silica, an adhesive sheet having a thickness of 30 μm was produced and evaluated in the same manner as in Example 1.

Example 4 Silica C and Silica D were used as silica, and after kneading with three rolls, they were stored for 15 days according to the method B, and an adhesive sheet having a thickness of 30 μm was produced in the same manner as in Example 1 and evaluated. did.

Comparative Example 1 An adhesive sheet was produced and evaluated in the same manner as in Example 1, except that Silica E and Silica D were used as silica.

Comparative Example 2 An adhesive sheet was produced and evaluated in the same manner as in Example 1, except that Silica F and Silica D were used as silica.

Comparative Example 3 An adhesive sheet was produced and evaluated in the same manner as in Example 1, except that only silica C was used as silica.

Comparative Example 4 An adhesive sheet was produced and evaluated in the same manner as in Example 1 except that only silica D was used as silica. Table 1 summarizes the results of visual inspection of the individual sheet support, flexibility, brittleness and surface state of the above film adhesives.

[0032]

[Table 1]

Examples 1 to 4 in which Silica C and Silica D are used in combination
In this system, the film characteristics are good and the surface condition is also excellent.
In particular, the one produced by the method B was improved in the repellant portion called a crater than the one produced by the method A. In Comparative Example 3 in which only silica C was used, a smooth surface free of foreign matter was obtained by visual observation, but the sheet properties were hard and brittle. Further, in Comparative Example 4 in which only Silica D was used, the film properties were hard as in Comparative Example 3, and there were many foreign substances on the surface, which are thought to be caused by aggregates of silica fine particles.

[0034]

The thin film adhesive of the present invention contributes to making the package lighter, thinner and shorter, and is also advantageous in packages having a stacked structure or the like. Furthermore, it is possible to perform temporary pressure bonding under mild conditions, and is excellent as a film adhesive for semiconductor chip bonding, which has characteristics of low linear expansion coefficient. In addition, since the thin film adhesive of the present invention has a uniform surface condition, compared with the dispensing method when using a paste material, it does not reduce the production speed, and voids are less likely to occur, so that smooth position accuracy can be obtained. It becomes possible to form a high adhesive layer.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Chihiro Hatano             1 Tsukiji, Kisarazu City, Chiba Nippon Steel Chemical Co., Ltd.             Shiki Company Electronic Materials Research Center (72) Inventor switch Tokuyuki             1 Tsukiji, Kisarazu City, Chiba Nippon Steel Chemical Co., Ltd.             Shiki Company Electronic Materials Research Center F-term (reference) 4J004 AA13 BA02 FA05                 4J040 DB032 EC071 EC081 EH012                       EL022 HA306 HB22 HB36                       HC01 HC10 HC15 HC23 HD38                       JA09 JB09 KA16 KA42 NA20                       PA23

Claims (3)

[Claims] 1. Silica based on 100 parts by weight of the resin component (A)
(B) In a thin film adhesive having a film thickness of 60 μm or less formed from a thermosetting resin composition containing 150 to 300 parts by weight, the resin component (A) is 10 to 50% by weight of the thermoplastic resin, A thermosetting resin or a thermosetting resin and a curing agent are contained in an amount of 50 to 90% by weight, and the silica (B) has an average particle diameter of 3 to 10 μm (b1) and an average particle diameter of 0.1 to 2
A thin film adhesive characterized in that it is a mixture of fine particle silica (b2) having a particle size of μm, and the maximum particle diameter of silica (B) is 0.8 T or less with respect to a film thickness T. 2. The silica (B) is a mixture of spherical silica (b1) and spherical silica (b2), and the weight ratio of (b1) / (b2) is 95/5 to 50/50. Item 2. A thin film adhesive according to item 1. 3. The epoxy resin (a1) 30-containing resin component (A)
The thin film adhesive according to claim 1 or 2, which comprises 60% by weight, 10 to 50% by weight of the thermoplastic resin (a2) and 30 to 50% by weight of the epoxy resin curing agent (a3).