JP2519277B2 - Semiconductor device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device which is less likely to cause package cracks during surface mounting and has excellent moisture resistance reliability.

[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, in a semiconductor device using a surface mounting package as described above, when the package itself absorbs moisture before surface mounting, there is a problem that cracking occurs in the package due to vapor pressure of water during solder mounting. is there.
That is, in the surface-mounted semiconductor device as shown in FIG. 1, moisture enters the package 3 through the sealing resin 1 as shown by an arrow A and the gap between the lead frame 2 and the sealing resin 1. It intrudes and stays mainly on the back surface of the die bond pad 4 of the lead frame 2. When the solder surface mounting such as vapor phase soldering is performed, the accumulated water is vaporized by heating in the solder mounting,
The vapor pressure pushes the resin portion on the back surface of the die bond pad 4 downward as shown in FIG.
And at the same time, a crack 6 is generated 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 in a package, the obtained semiconductor device is hermetically sealed, and opened and used just 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, 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 the above circumstances, and an object thereof is to provide a semiconductor device that does not require pretreatment for mounting on an electronic device and can withstand heating during solder mounting and has excellent moisture resistance reliability. .

[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 phenol resin curing agent component consisting of a phenol resin and an inorganic filler as main components, and an epoxy resin composition containing a hydrotalcite compound and at least one of a bismuth hydroxide / antimony pentoxide compound is used. The semiconductor element is sealed with the structure.

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 (4), the strength of the sealing resin under high temperature such as solder mounting is improved about 3 to 4 times as compared with the current resin. And
Harmfulness due to ionic impurities contained in the high-strength sealing resin as described above (impurities are ionized when the resin absorbs water, and the ions cause damage to the bonding ties and electrodes)
In order to prevent the deterioration of moisture resistance by eliminating the above, at least one of a hydrotalcite compound and a bismuth hydroxide / antimony pentoxide compound is blended as an ion trapping agent to trap impurity ions.

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. A phenolic resin hardener component made of a special phenolic resin, and an inorganic filler,
It is obtained by using a hydrotalcite compound and at least one of bismuth hydroxide and antimony pentoxide, etc., and is usually in the form of powder or a tablet formed by compressing it.

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, it is preferable to use a resin having a melting point exceeding room temperature and exhibiting a solid state or a highly viscous solution state at room temperature. As the novolak type epoxy resin, usually, epoxy equivalent 150 to 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 manner, the special epoxy resin represented by the general formula (I) and the ordinary epoxy resin are used in an amount of 100 parts by weight (hereinafter abbreviated as "part") with respect to the former. The latter is preferably set within the range of 0 to 100 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.

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

The hydrotalcite-based compound is a component that effectively traps anions such as chlorine ions or bromine ions that are derived from the epoxy resin composition and exist as impurity ions in the sealing resin. The hydrotalcite-based compound is represented by, for example, the following general formula.

Mg _x Al _y (OH) _{2x + 3y-2z} (CO ₃ ) _z・ mH ₂ O The above-mentioned bismuth hydroxide / antimony pentoxide is a component that effectively traps cations such as sodium ions, while the above-mentioned hydrotalcite compounds trap anions. As an example of this, Toa Gosei Co., Ltd., A
HK-600 [Bi (OH) ₂ · Sb ₂ O ₅ · 4H ₂ O] can be mentioned.

The content of at least one of the above-mentioned hydrotalcite compounds and bismuth hydroxide / antimony pentoxide is 0.5 to 15% by weight with respect to the organic component of the epoxy resin composition.
It is preferable to set (hereinafter abbreviated as “%”). That is, when the content exceeds 15%, various characteristics other than the moisture resistance reliability of the sealing resin tend to be adversely affected.

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 that of the conventional one, package cracks and the like do not occur during solder mounting. Furthermore, since at least one of the hydrotalcite-based compound and bismuth hydroxide / antimony pentoxide is added, no harmful effects due to impurity ions occur and extremely excellent moisture resistance reliability is provided.

〔The invention's effect〕

A semiconductor device according to the present invention has a semiconductor element using a special epoxy resin composition containing at least one of the above-mentioned special epoxy resin, phenol resin, hydrotalcite compound and bismuth hydroxide / antimony pentoxide. Since it is resin-sealed, package cracking does not occur even under severe conditions such as solder mounting, and since the anions and cations are captured by the trapping agent in the sealing plastic package, the humidity resistance is high. Is extremely high. In particular, by encapsulating with the above special epoxy resin composition, more than 8 pins, especially
This is a major feature because the above high reliability can be obtained in a large-sized semiconductor device having 16 pins or more or a long side of a chip of 4 mm or more.

 Next, examples will be described together with comparative examples.

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

<< Main agent >> A: General formula component (n = 3) B: Epoxycresol novolak (n = 4) (n was calculated from the weight average molecular weight of GPC polystyrene conversion data.) << Curing agent >> C: General formula component ( n = 3) D: phenol novolak (n = 4) (n was calculated from the weight average molecular weight of GPC polystyrene conversion data.) << Filler >> E: Maximum particle size = 150 μm, average particle size = 20 μm, crushed type SiO ₂ << Flame Retardant >> F: Novolac type Br epoxy epoxy G: 3 antimony oxide 2 << Curing catalyst >> H: Triphenylphosphine I: Dimethylimidazole << Release agent >> J: Polyethylene wax << Additive >> K : Trimethoxysilane glycidyl ether << Ion trapping agent >> L: Hydrotalcite compound M: Bismuth hydroxide / antimony pentoxide compound The raw materials shown in Table 1 below are blended 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. In addition, in the PCBT test, the product of the example has a significantly long anode and cathodic corrosion life, and it can be seen that the moisture resistance reliability is significantly improved as compared with the product of the comparative example.

[Brief description of drawings]

 1 and 2 are explanatory views of a conventional example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Oizumi 1-2-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Electric Industrial Co., Ltd. (72) Inventor Junichi Adachi 1, Shimohozumi, Ibaraki City, Osaka Prefecture No. 1 and 2 Nitto Electric Industry Co., Ltd.

Claims (1)

(57) [Claims] An epoxy resin base component at least partially composed of an epoxy resin represented by the following general formula (I):
At least a part of a phenol resin curing agent component consisting of a phenol resin represented by the following general formula (II) and an inorganic filler as a main component, and at least a hydrotalcite compound and a bismuth hydroxide / antimony pentoxide compound. A semiconductor device obtained by encapsulating a semiconductor element with an epoxy resin composition containing one of them.