JP2519278B2 - Semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device in which package cracks are less likely to occur during surface mounting.

[Conventional technology]

Semiconductor elements such as transistors, ICs, and LSIs are made into semiconductor devices by being sealed with a plastic package or the like from the viewpoints of protecting the external environment and enabling the handling of the elements. A representative example of this type of package is a dual in-line package (DIP). The DIP is of a pin insertion type, and attaches a semiconductor device by inserting a pin into a mounting board.

Recently, high integration and high speed of semiconductor devices such as LSI chips have been advanced, and in addition, high density mounting has been advanced due to a demand for making electronic devices small and highly functional. From this point of view, instead of a pin insertion type package like DIP,
Surface mount packages are becoming mainstream. In a semiconductor device using this kind of package, pins are taken out in a plane and are fixed directly to the surface of the mounting board by soldering or the like. Such a surface-mount type semiconductor device has an advantage that pins can be taken out in a plane and has the advantages of being thin, light, and small, and therefore has the advantage of occupying a small area on the mounting board. In addition, it has the advantage that double-sided mounting on a substrate is also possible.

[Problems to be solved by the invention]

However, when the package itself absorbs moisture before the surface mounting as described above, there is a problem that the package is cracked due to the vapor pressure of water during solder mounting. That is, in the surface mount type semiconductor device as shown in FIG. 1, moisture enters the package 3 through the sealing resin 1 and the gap between the lead frame 2 and the resin 1 as shown by arrow A. , Mainly on the back surface of the die bond pad 4 of the lead frame 2. Then, when solder surface mounting such as vapor phase soldering is performed, the accumulated water is vaporized by heating in the solder mounting, and the vapor pressure thereof causes a resin on the back surface of the die bond pad 4 as shown in FIG. The part is pushed downwards, creating a void 5 therein and at the same time creating a crack 6 in the package 3. 1 and 2, reference numeral 7 denotes a semiconductor element, and reference numeral 8 denotes a wire bonding.

As a solution to such a problem, after sealing a semiconductor element with a package, the whole obtained semiconductor device is sealed and opened immediately before surface mounting, or the above semiconductor device is mounted immediately before surface mounting. A method has been proposed and already implemented in which the solder is dried at 100 ° C for 24 hours and then solder mounting is performed. However, according to such a pretreatment method, there is a problem that the manufacturing process becomes long and labor is required.

The present invention has been made in view of such circumstances, and an object thereof is to provide a semiconductor device which does not require pretreatment for mounting on an electronic device and can withstand heating during solder mounting.

[Means for solving problems]

In order to achieve the above-mentioned object, the semiconductor device of the present invention has an epoxy resin main component comprising at least a part of an epoxy resin represented by the following general formula (I) and at least a part of the following general formula (II ), A semiconductor resin is encapsulated with a phenol resin curing agent component composed of a phenol resin and an epoxy resin composition containing an inorganic filler as a main component.

In the above formulas (I) and (II), the number of repetitions n
Is determined from the weight average molecular weight Mw value.

[Action]

As a method to prevent the occurrence of package cracks,
Three methods are conceivable: suppression of moisture absorption with respect to the sealing resin, enhancement of the adhesive force between the back surface of the die bond pad and the surface of the semiconductor element and the sealing resin, and enhancement of the strength of the sealing resin itself. This invention prevents the occurrence of package cracks by increasing the strength of the encapsulating resin itself. The special epoxy resin represented by the general formula (I) and the general formula (II By using a special phenol resin represented by), the strength of the encapsulating resin under high temperature such as solder mounting is improved about 3 to 4 times as compared with the current resin. Is.
In particular, as an inorganic filler of the epoxy resin composition used for sealing, if a crushed filler having a maximum particle diameter of 50 μm and an average particle diameter of 2 to 15 μm and a spherical filler having a maximum particle diameter of 100 μm or less and an average particle diameter of 10 to 25 μm are used together. In addition, the effect of improving the resin strength at high temperatures as described above can be obtained, and at the same time, the epoxy resin composition itself can be provided with excellent fluidity.

The epoxy resin composition used in the present invention comprises an epoxy resin main component consisting of a special epoxy resin represented by the general formula (I) in whole or in part and represented by the general formula (II) in whole or in part. It is obtained by using a phenol resin curing agent component composed of a special phenol resin described above and an inorganic filler, etc., and is usually in the form of a powder or a tablet formed by tableting.

The special epoxy resin of the general formula (I) constituting all or a part of the above-mentioned epoxy resin main component has a structure in which phenyl glycidyl ether is bonded to a methylene group in the main chain of a novolak type epoxy resin. With such a molecular structure, the number of crosslinking points is increased and a structure having a high crosslinking density can be obtained. The epoxy resin main component may be composed of only the special epoxy resin described above, or may be used in combination with other commonly used epoxy resins. Examples of commonly used epoxy resins include various epoxy resins such as cresol novolak type, phenol novolak type, and bisphenol A type. Among these resins, the melting point is higher than room temperature, and it does not bring high results to use a solid or highly viscous solution at room temperature, and as a novolak type epoxy resin, an epoxy equivalent is usually used. 150-250,
Those having a softening point of 50 to 130 ° C. are used, and as the cresol novolak type epoxy resin, an epoxy equivalent of 180 to 210,
A softening point of 60 to 110 ° C is generally used. When both are used in this way, the special epoxy resin represented by the general formula (I) and the normal epoxy are the former 100 parts by weight (hereinafter abbreviated as "part") and the latter 100 parts by weight. 0-100
It is preferable to set it within the range of parts.

The special phenol resin represented by the above general formula (II), which constitutes all or part of the phenol resin curing agent component, has a structure in which a phenol is bonded to the methylene group of the main chain of the phenol novolak, Due to such a molecular structure, the number of cross-linking points increases, whereby a three-dimensional structure having a high cross-linking density can be obtained. The above-mentioned special phenol resin may constitute a phenol resin curing agent component by itself, or may be used in combination with other commonly used phenol resin. Examples of other phenol resins include phenol novolak and cresol novolak. These novolak resins are
It is desirable to use one having a softening point of 50 to 110 ° C and a hydroxyl equivalent of 70 to 150. Especially among the above Novorak resin,
The use of cresol novolak has been successful. The ratio of the special phenol resin represented by the general formula (II) and the case where such a normal phenol resin is used in combination is set in the range of 0 to 100 parts with respect to 100 parts of the former. Is preferable in terms of the effect.

Silica is usually used as the inorganic filler used together with the epoxy resin main component and the phenol resin curing agent component. In addition to the crystalline and fusible fillers, fillers such as aluminum oxide, beryllium oxide, silicon carbide and silicon nitride may be used. As such an inorganic filler, it is effective to use a crushed filler having a maximum particle size of 50 μm or less and an average particle size of 2 to 15 μm and a spherical filler having a maximum particle size of 100 μm or less and an average particle size of 10 to 25 μm. Is preferred. By using both of them together in this manner, it is possible to obtain about four times the strength as compared with the conventional sealing resin, and at the same time, to impart excellent fluidity to the epoxy resin composition. .

In the epoxy resin composition used in the present invention, a flame retardant, a coupling agent, a curing accelerator, wax, etc. may be used, if necessary, in addition to the above components.

As the flame retardant, compounds such as novolak type brominated epoxy or bis A type epoxy, antimony trioxide and antimony pentoxide are appropriately used alone or in combination.

As the above-mentioned coupling agent, methoxy or ethoxysilane such as glycidyl ether type, amine type, thiocyan type and urea type may be used alone or in combination as appropriate. As a method of using the filler, it is possible to dry blend the filler, or carry out a preliminary heating reaction, and further preliminarily mix the organic component raw material.

Examples of the curing accelerator include amine-based, phosphorus-based, and boron-based curing accelerators, 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 appropriately mixing and premixing the above component raw materials, the mixture is kneaded in a heating state by a kneading machine such as a mixing roll machine to be melt mixed, cooled to room temperature, and then pulverized by a known means, It can be manufactured by a series of steps of tableting as necessary.

The sealing of the semiconductor element using such an epoxy resin composition 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 general formula (I) and the special phenol resin represented by the general formula (II) contained in the epoxy resin composition. Since the strength of the sealing resin, especially at high temperature, is 3 to 4 times as high as the conventional one, package cracks and the like do not occur during solder mounting.

〔The invention's effect〕

In the semiconductor device of the present invention, since the semiconductor element is resin-sealed with the special epoxy resin composition containing the special epoxy resin and the phenol resin as described above, the semiconductor device is soldered under severe conditions. Also does not cause a package crack. In particular, by encapsulating with the above special epoxy resin composition, 8 pins or more,
In particular, in a large-sized semiconductor device having 16 pins or more or a chip long side of 4 mm or more, the above high reliability can be obtained, which is a major feature.

 Next, examples will be described together with comparative examples.

[Examples 1 to 12, Comparative Examples 1 to 6] First, the component raw materials used in Examples and Comparative Examples are as follows.

<Main agent> A: Component of general formula (n = 3; calculated from weight average molecular weight) B: Component of general formula (n = 5; calculated from weight average molecular weight) C: Epoxycresol novolac (n = 4; weight average) Calculated from molecular weight) D: Same as above (n = 7; calculated from weight average molecular weight) (Weight average molecular weight was calculated in terms of polystyrene by GPC measurement.) <Curing agent> E: General formula component (n = 3; weight average) F: same as above (n = 5; calculated from weight average molecular weight) G: phenol novolak (n = 4; calculated from weight average molecular weight) H: same as above (n = 7; calculated from weight average molecular weight) (weight The average molecular weight was measured by GPC and calculated in terms of polystyrene.) <Filler> I: maximum particle size = 50 μm average particle size = 3 μm (shape = crush type) J: maximum particle size = 100 μm average particle size = 15 μm (shape = Spherical) K: maximum particle size = 150 μm average particle size = 20 μm (shape = crushed diameter) <flame retardant > L: Novolac-type Br-epoxy M: Niantimony trioxide <Curing catalyst> N: Triphenylphosphine O: Dimethylimidazole <Release agent> P: Polyethylene wax Q: Higher fatty acid ester wax <Additives> R: Trimethoxysilane glycidyl ether The raw materials shown in Table 1 below are mixed in the proportions shown in the same table,
The mixture was kneaded with a mixing roll machine at 100 ° C. for 10 minutes to obtain a sheet composition. Then, the obtained sheet-shaped composition was pulverized to obtain a desired powdered epoxy resin composition.

A semiconductor device was obtained by molding a semiconductor element by transfer molding using the powdery epoxy resin compositions obtained in the above Examples and Comparative Examples. This semiconductor device is an 80-pin QFP package (20 x 14 mm, thickness 2.
25 mm) and has a chip size of 7 × 7 mm.

The semiconductor device thus obtained was subjected to a measurement test. The results are shown in Table 2 below.

From the results in Table 2, the example products are not so different from the comparative examples in each property, especially in bending property at room temperature (RT),
At a high temperature such as 215 ° C., the result is remarkably superior to that of the comparative example, and it can be seen that the strength of the package at a high temperature is significantly improved.

[Brief description of drawings]

 1 and 2 are explanatory views of a conventional example.

Claims (1)

(57) [Claims] An epoxy resin base component at least partially composed of an epoxy resin represented by the following general formula (I):
A semiconductor obtained by encapsulating a semiconductor element by using a phenol resin curing agent component at least a part of which is represented by the following general formula (II) and an epoxy resin composition containing an inorganic filler as a main component. apparatus.