JPH01171232A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent package cracks even under severe conditions as observed in solder packaging operation or the like, by resin sealing a semiconductor element with a special epoxy resin composition containing particular epoxy and phenol resins. CONSTITUTION:A semiconductor element mounted on a die bond pad of a lead frame is sealed with an epoxy resin composition principally composed of an epoxy resin chief component partially composed of an epoxy resin of formula 1, a phenol resin curing component partially composed of a phenol resin of formula II and an inorganic filler. The rear face of the die bond pad is covered with polyimide. In a semiconductor device thus obtained, the sealing resin is allowed to have strength higher than conventional ones. Particularly under high temperatures, it is allowed to have strength three or four times as high as that of the conventional ones by the effects of the special epoxy resin of the formula I and the special phenol resin of the formula II contained in the epoxy resin composition. Thus, the semiconductor device is freed of package cracks or the like when it is packaged with solder. In the formulae, (n) is an integer of 0-10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a semiconductor device in which package cracks are less likely to occur during surface mounting.

[Conventional technology]

2. Description of the Related Art Semiconductor elements such as transistors, ICs, and LSIs are sealed in plastic packages or the like to form semiconductor devices from the viewpoint of protecting the external environment and enabling handling of the elements. A typical example of this type of package is the dual inline package (DIF).
There is. This DrP is a pin insertion type, and a semiconductor device is attached by inserting a pin into a mounting board.

Recently, the integration and speed of semiconductor devices such as LSI chips have been increasing, and in addition, the demand for smaller and more highly functional electronic devices has led to higher density packaging. From this point of view, surface mount packages have become mainstream instead of pin insertion type packages such as DIP. In a semiconductor device using this type of package, pins are taken out in a plane and fixed directly to the surface of the mounting board by soldering or the like. These surface-mounted semiconductor devices have pins that can be taken out on a flat surface, and have the advantages of being thin, light, and small.
Therefore, it has the advantage that it occupies only a small area on the mounting board, and also has the advantage that it can be mounted on both sides of the board.

[Problem that the invention seeks to solve]

However, in a semiconductor device using a surface mount package as described above, if the package itself absorbs moisture before surface mounting, there is a problem that cracks occur in the package due to the vapor pressure of moisture during solder mounting. That is, in the surface-mounted semiconductor device as shown in FIG. It invades and accumulates mainly on the back surface of the Guibond pad 4 of the lead frame 2. Then, when performing solder surface mounting such as paper phase soldering, the accumulated moisture is vaporized by the heating during the solder mounting, and its vapor pressure causes the back surface of the Guibond batt 4 to be heated as shown in FIG. The resin portion is pushed downward, creating a gap 5 there and at the same time creating a crack 6 in the package 3.

In FIGS. 3 and 4, 7 is a semiconductor element.

8 is wire bonding.

As a solution to such problems, there are methods in which the semiconductor element is sealed in a package, the entire semiconductor device obtained is sealed, and the package is opened and used immediately before surface mounting, or the semiconductor device is sealed in a package immediately before surface mounting. A method of drying at 100° C. for 24 hours and then performing solder mounting has been proposed and has already been implemented. However, such a pretreatment method has the problem that the manufacturing process is long and labor-intensive.

The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a semiconductor device that does not require pretreatment when mounted on electronic equipment and can withstand heat during solder mounting.

[Means for solving problems]

In order to achieve the above object, the semiconductor device of the present invention includes:
An epoxy resin main component consisting of an epoxy resin at least partially represented by the following general formula (I); and a phenolic resin curing agent component consisting of a phenol resin at least partially represented by the following general formula (n). , a semiconductor device in which a semiconductor element mounted on a die bond pad of a lead frame is encapsulated using an epoxy resin composition containing an inorganic filler as a main component, the back surface of the die bond pad being coated with polyimide. The structure is that

(n-0 to 10) (blank below) (n = 0 to 10) In addition, in the above formulas (I) and (n), the number of repetitions n is
It is determined from the weight average molecular weight Mw value.

[Effect]

As a method to prevent the occurrence of package cracks, ■
Three methods can be considered: suppressing moisture absorption into the sealing resin; (1) increasing the adhesive force between the back surface of the Guibond bat and the surface of the semiconductor element and the sealing resin; and (2) increasing the strength of the sealing resin itself. This invention prevents the occurrence of package cracks by increasing the adhesive strength between the back side of the die bonding bat and the surface of the semiconductor element and the sealing resin as described in (■) above, and increasing the strength of the sealing resin itself as described in (■) above. By using the special epoxy resin represented by type (1) above and the special phenol resin represented by type (II) above, The strength of the sealing resin is improved by about 3 to 4 times compared to the current resin. Furthermore, as shown in FIG. 1, since the back surface of the die bond pad 4 is covered with the polyimide thin film 9, excellent adhesive force is generated between the sealing resin 1 and the die bond pad 4.

The semiconductor device of the present invention is directed to a semiconductor element attached to a lead frame in which the back surface of the die bond pad is coated with polyimide, and all or part of which is a special semiconductor device represented by the above-mentioned type (I). An epoxy resin composition whose main components are an epoxy resin main component made of an epoxy resin, a phenolic resin curing agent component made of a special phenol resin whose whole or part is represented by the above-mentioned form (II), and an inorganic filler. It is something that can be obtained using things. The epoxy resin composition is usually in the form of a powder or a tablet formed by compressing it.

The special epoxy resin of type (I) that constitutes all or part of the epoxy resin base component has a structure in which phenyl glycidyl ether is bonded to a methylene group in the main chain of a novolac type epoxy resin. By adopting such a molecular structure, the number of crosslinking points increases and a structure with high crosslinking density can be obtained. Note that the epoxy resin base component may be composed only of the above-mentioned special epoxy resin, or may be used in combination with other commonly used epoxy resins. The commonly used epoxy resin is Talesol novolac type.

Examples include various epoxy resins such as phenol novolac type and bisphenol A type. Among these resins,
Good results can be obtained by using a material having a melting point above room temperature and exhibiting a solid state or a highly viscous solution state at room temperature. The novolac type epoxy resin usually has an epoxy equivalent of 150 to 250. A Talesol novolac type epoxy resin with a softening point of 50 to 130°C is used, and an epoxy equivalent of 180 to 210. Softening point 60-1
A temperature of 10°C is generally used. In this way, when both are used together, the special epoxy resin represented by the above-mentioned form (1) and the above-mentioned ordinary epoxy resin are the former 1.
The latter 0 to 10 parts by weight (hereinafter abbreviated as "parts")
It is preferable to set it within the range of 0 copies.

The special phenolic resin represented by form (II) above, which constitutes all or part of the phenolic resin curing agent component, has a structure in which phenol is bonded to the methylene group in the main chain of phenol novolac. Such a molecular structure increases the number of crosslinking points, thereby increasing the crosslinking density and making it possible to obtain a three-dimensional structure. The above-mentioned special phenolic resin may constitute the phenolic resin curing agent component by itself, or may be used in combination with other commonly used phenolic resins. Examples of other phenolic resins include phenol novolak, cresol novolak, and alkylated phenol novolak. These novolac resins have a softening point of 50 to 11
It is desirable to use one having a 0°C2 hydroxyl equivalent of 70 to 150.

Particularly, among the above-mentioned novolac resins, use of Talesol novolac brings about good results. Above - Format (ff
) When using a special phenolic resin represented by ( ) and such a normal phenolic resin, the effective point is to set the ratio of both in the range of 0 to 100 parts to 100 parts of the former. It is preferable.

Examples of the inorganic filler used together with the epoxy resin base component and the phenolic resin curing agent component include crystalline and meltable fillers, as well as aluminum oxide, beryllium oxide, silicon carbide, silicon nitride, and the like.

The polyimide used for coating the back surface of the die bond pad includes conventionally known polyimides, and is usually synthesized from an organic tetracarboxylic dianhydride and an organic diamine.

Examples of the organic tetracarboxylic dianhydride include those represented by the following general formula.

(Left white) 1, -CH2-C (CHri 2-CH2-, etc.).

Specific examples of such organic tetracarboxylic dianhydrides include, for example, 3.3', 4.4'
-Butanetetracarboxylic dianhydride, cyclopenkune tetracarboxylic dianhydride, and 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene represented by the following formula (a) -1゜2-dicarboxylic anhydride and bicyclo[2,2,2]octene-(7)-2,3,5, represented by the following formula (b),
6-tetracarboxylic dianhydride, aliphatic tetracarboxylic dianhydride such as pyromellitic dianhydride, 3.3', 4.4'-biphenyltetracarboxylic dianhydride, 2,3.3 ',4'-Biphenyltetracarboxylic dianhydride, 21.3.6.7-naphthalenetetracarboxylic dianhydride, 1,2,4.5-naphthalenetetracarboxylic dianhydride, 1,2,5 .6-Naphthalene tetracarboxylic dianhydride, 3.3', 4.4'-
Benzophenone tetracarboxylic dianhydride, 2,2-bis[4-(2,3-dicarboxyphenoxy)phenyl]propanihydride, 4,4'-bis(2,3-dicarboxyphenoxy)diphenyl ether dianhydride These aromatic tetracarboxylic dianhydrides can be used alone or in combination. Examples of derivatives of organic tetracarboxylic dianhydrides include tetracarboxylic oxides, lower alkyl esters, and polyhydric alcohol esters of the above-mentioned tetracarboxylic dianhydrides.

Next, examples of the above-mentioned organic diamine include those represented by the following format.

HzNRs NHz Specific examples of the above organic diamine include 1.2-
Ethylenediamine, 1,6-hexamethylenediamine,
Xylylenediamine, isophoronediamine, p-cyclohexyldiamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro-(5,5
)-Aliphatic diamines such as undecane, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'
-diaminodiphenyl ether, 3,3'-dimethoxy-4,4'-diaminodiphenyl ether, 3,3'-
Diphenyl ether diamines such as diaminodiphenyl ether and 3,4′-diaminodiphenyl ether, 4
, 4'-diaminodiphenylthioether, 3,3'-
Diphenylthioether diamines such as dimethyl-4,4'-diaminodiphenylthioether, 3,3'-dimethoxy-4,4'-diaminodiphenylthioether, 3.3'-diaminodiphenylthioether, 4.4
'-Diaminobenzophenone, 3,3'-dimethyl-4
, 4'-diaminobenzophenone, benzophenone diamines such as 3,3'-diaminobenzophenone, 3,3
'-Diamino diphenylmethane, 4.4'-diaminodiphenylmethane, 3.3'-dimethoxy-4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4
Diphenylmethane diamines such as '-diaminodiphenylmethane, bisphenylpropane diamines such as 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)propane, 4,4'-diaminodiphenyl sulfoxide, diphenyl sulfoxide diamines such as 3.3'-diaminodiphenylsulfoxide, 4.4'-diaminodiphenylsulfone, 3.3'-
Diphenylsulfone diamines such as diaminodiphenylsulfone, benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, biphenyl diamines such as 3°3'-diaminobiphenyl, 2,6-diaminopyridine, 3,6-diaminopyridine, 2,5-
Pyridine diamines such as diaminopyridine, 3゜4-diaminopyridine, o-, m- or p-diaminobenzene, 3,5-diaminobenzoic acid, 4,4'-di(m-
aminophenoxy) diphenyl sulfone, 4.4'-
Di(p-aminophenoxy)diphenylsulfone, 4.
4'-di(m-aminophenoxy)diphenyl ether, 4.4'-di(p-aminophenoxy)diphenyl ether, 4.4'-di(m-aminophenoxy)diphenylpropane, 4.4'-di(p- aminophenoxy)
Diphenylpropane, 4,4'-di(m-aminophenylsulfonyl)diphenyl ether, 4,4'-di(p
-aminophenylsulfonyl) diphenyl ether,
4.4'-di(m-aminophenylthioether) diphenyl sulfide, 4.4'-di(p-aminophenylthioether) diphenyl sulfide, 4,4'-di(
m-aminophenoxy)diphenylketone, 4,4'-
Di(p-aminophenoxy)diphenylketone, 4.4
'-di(m-aminophenoxy)diphenylmethane, 4
．． Examples include aromatic diamines such as 4'-di(p-aminophenoxy)diphenylmethane.

Furthermore, examples of silicon-based diamines include those represented by the following formulas (a) to (g).

CH3CH3 a) nzN+cHz→TSi-0-Si+CH,-)
-r-NH2CH3CHi CbHs Ci, H5 l CH3CHi CHs 0CHz CH:I Il+ Such organic diamines can be used alone or in combination.

The coating treatment of the die bond pad with the above-mentioned polyimide can be carried out by coating at least the back side of the die bond pad of the lead frame in the state of a polyamic acid solution using conventionally known treatment methods such as spin cord method, screen printing method, spraying method, coating method, etc. After applying by dipping method etc., temperature 2
This is done by performing heat treatment at 50°C for about 5 hours to obtain a polyimide thin film. Appropriate conditions for curing by heat treatment vary depending on the type of polyimide, but usually sufficient adhesive strength to the coated surface can be obtained by curing at a temperature of 200° C. for 3 hours. The thickness of the coating polyimide is 1 to 200 μm, preferably 5 to 30 μm.
Good results can be obtained by setting it to . Note that the coating treatment with polyimide may be performed not only on the back surface of the die bond pad, but also on the side surface of the die bond pad, the outer peripheral surface 9 of the semiconductor element, and the surface of the lead frame. Furthermore, the coating may be applied not only to the entire back surface of the die bond pad but also to a portion thereof.

In addition, the epoxy resin composition used in this invention may contain flame retardants, coupling agents,
A curing accelerator, wax, etc. are used.

As the flame retardant, compounds such as novolac type brominated epoxy, bis A type epoxy, antimony trioxide, and antimony pentoxide may be used alone or in combination as appropriate.

The above-mentioned coupling agents include glycidyl ether type, amine type, and thiocyan type.

Methoxy or ethoxysilane such as urea type,
They may be used alone or in combination as appropriate.

It can be used in any manner, such as by triblending or preheating the filler, or by premixing the organic component raw material.

Examples of the curing accelerator include amine-based (tertiary amines, quaternary ammonium salts, imidazoles), phosphorus-based, boron-based curing accelerators, etc., which may be used alone or in combination.

Examples of the wax include compounds such as higher fatty acids, higher fatty acid esters, and higher fatty acid calcium, which may be used alone or in combination.

The epoxy resin composition used in this invention can be produced, for example, as follows.

That is, after suitably blending and pre-mixing the above-mentioned component raw materials, they are kneaded and melt-mixed in a heated state using a kneading machine such as a mixing roll machine, and after cooling this to room temperature, it is pulverized by known means, and as necessary. It can be manufactured by a series of steps of tabletting according to the appropriate conditions.

The semiconductor device of the present invention can be manufactured using the epoxy resin composition as described above, for example, in the following manner. That is, it can be obtained by first coating the back surface of the die bond pad of a lead frame to be sealed with polyimide, then attaching a semiconductor element to this lead frame, and sealing it with the above-mentioned epoxy resin composition. The above sealing is not particularly limited, and can be performed by a known molding method such as normal transfer molding.

The semiconductor device thus obtained is produced by the action of the special epoxy resin represented by the above-mentioned form (I) and the special phenol resin represented by form (1) contained in the epoxy resin composition. Since the strength of the sealing resin, especially the strength at high temperatures, is three to four times higher than that of conventional ones, package cracks do not occur even during solder mounting. Furthermore, since the back surface of the die bond pad of the lead frame is coated with polyimide, the adhesive strength between the sealing resin and the lead frame is extremely excellent.

〔Effect of the invention〕

In the semiconductor device of the present invention, the semiconductor element is resin-sealed using a special epoxy resin composition containing the above-mentioned special epoxy resin and phenol resin, so it can withstand harsh conditions such as solder mounting. No package cracks will occur even in this case. Furthermore, since the back surface of the die bond pad of the lead frame is coated with polyimide, the adhesive strength between the sealing resin and the lead frame is improved, and the lead frame has extremely excellent moisture resistance reliability. In particular, by sealing with the above-mentioned special epoxy resin composition, 8
Pins or more, especially 16 pins or more or the long side of the chip is 4
This makes it possible to obtain high reliability orbits as described above in large-sized semiconductor devices of mm or more, and this is a major feature.

Next, examples will be described together with comparative examples.

[Examples 1 to 10, Comparative Examples 1 to 5] First, the component raw materials used in the Examples and Comparative Examples are as follows.

(Main agent) A knee format (I) component (n = 3) B: Epoxy cresol novolac (n = 4) (n is G
Calculated from the weight average molecular weight of PC polyethylene conversion data. ) (Curing agent) C: mAII) component (n = 3) D: Phenol novolac (n = 4) (n was calculated from the weight average molecular weight of GPC polyethylene conversion data.) <Filler> E: Maximum particle size = 150 um, average particle size = 20 μm
.

Crushed type molten SiO□ (Flame retardant) F: Novolac type Br epoxy G: Niantimony dioxide (curing catalyst) H Nidimethylimidazole (Release agent) ■: Polyethylene wax (Additive) J Nitrimethoxysilane glycidyl Ether (polyimide synthetic material) <Acid anhydride><Amine> CH.

C! o) H2N-()-0riFC-Q-0-Q-NH4
ICH.

(C) H2N+0eNH2 (Polyimide application method) (d) Brush coating (e) Dipping coating) Spin coating (curing conditions by heat treatment) (Cask temperature 200°C, 3 hours (5) Temperature 250'C, 5 hours ( i) Temperature: 250°C, 920 hours The raw materials shown in Table 1 below were blended in the proportions shown in the same table, and kneaded using a mixing roll machine at 100°C for 10 minutes to obtain a sheet-like composition. The sheet composition was pulverized to obtain the desired powdered epoxy resin composition.

(The following is a blank space) A semiconductor device was obtained by molding a semiconductor element by transfer molding using the powdered epoxy resin composition obtained in the above Examples and Comparative Examples. This semiconductor device is packaged in an 80-bin QFP package (20×14
mm, thickness 2.25 mm), and has a chip size of 7 x 7 mm.

Measurement tests were conducted on the semiconductor device thus obtained. The results are shown in Table 2 below. Note that the adhesive force between the die bond pad and the sealing resin is as shown in FIG. ) The shear adhesive force between 4a was measured by applying stress in the direction of arrow B.

(Margins below) From the results in Table 2, the properties of the example product, especially the bending properties at room temperature, are not significantly different from those of the comparative height measurement, but the 215
At high temperatures such as °C, the results are significantly better than the comparative height measurements, and it can be seen that the strength of the package at high temperatures is significantly improved. Furthermore, it can be seen that the number of package cracks occurring in the example products is extremely small, and the moisture resistance reliability is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of a method for measuring adhesive force between a die bond pad and a sealing resin, and FIGS. 3 and 4 are explanatory diagrams of a conventional example. 1... Sealing resin 2... Lead frame 3...
Package 4...Die bond pad 7...Semiconductor element 8...Wire bonding 9...Polyimide thin film patent applicant Nitto Electric Industry Co., Ltd. Representative Patent attorney Yukihiko Nishifuji Figure 2

Claims (1)

[Claims] (1) Curing of a phenolic resin consisting of an epoxy resin main component, at least a part of which is an epoxy resin represented by the following general formula (I), and a phenol resin, at least a part of which is a phenol resin represented by the following general formula (II). A semiconductor device in which a semiconductor element attached to a die bond pad of a lead frame is encapsulated using an epoxy resin composition whose main components are a filler and an inorganic filler, and the back surface of the die bond pad is made of polyimide. A semiconductor device characterized by being coated. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(I) (n=0-10) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(II) (n=0-10)