JPH0839549A - Tablet for sealing semiconductor - Google Patents

Abstract

PURPOSE:To obtain a semiconductor package with a small number of inner voids by making voids as small as possible in number which are contained in a tablet obtained by press-forming an epoxy resin composite for sealing semiconductors. CONSTITUTION:The particle size distribution of an epoxy resin composition is controlled in the ratio of 90mum or less to 0-15wt.%, 91mum-500mum to 5-45wt.%, 50mum-1000mum to 30-60wt.%, 1001mum-2300mum to 0-10wt.%, and 2301mum or more to 0%. These are formed into tablets by the use of a tablet forming machine. The punching out density of tablet is in the range of 91-99%. Even if the destroyed substances in the particle size distribution are used, when the punching out density is 91% or less, the ratio of voids is increased with the result that inside voids are not reduced in number. When the destroyed substances in the particle size distribution are used and forming is conducted by a maximum forming, the punching out density is of the order of about 98%. In this manner, inside voids almost never occur, thereby enhancing adhesiveness between the chip and the frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor encapsulating tablet which is excellent in moldability, solder heat resistance and moisture resistance reliability.

[0002]

2. Description of the Related Art Resin encapsulation using an epoxy resin composition is widely used as a method for encapsulating semiconductor elements such as ICs and LSIs because it is economically suitable for mass production. This sealing method is carried out by inserting a tablet obtained by pressure-molding an epoxy resin composition into a cylindrical shape into a pot of a mold set in a transfer molding machine, and pressing a plunger to remove the inside of the mold. The epoxy resin composition is cured by passing the gate through the runner, filling a cavity in which a lead frame mounting a semiconductor element is set in advance, and curing the epoxy resin composition. The tablet used in this encapsulation method is obtained by heating and kneading the entire composition such as an epoxy resin and an inorganic filler with a heating kneader or a heating roll, followed by cooling and crushing and pressing the mixture into a tablet molding machine. It was obtained. In addition, in recent market trends of miniaturization, weight reduction, and high performance of electronic devices, semiconductor integration has advanced year by year, and surface mounting of semiconductor packages has been promoted. The demands are becoming more stringent. As the package becomes thinner, the thickness of the semiconductor encapsulating material in the package is becoming thinner. For example, in the case of 1 mm thick TSOP,
The thickness of the sealing material formed on the upper surface of the chip and the lower surface of the island is about 0.2 to 0.3 mm. Therefore, problems such as moisture resistance reliability, solder crack resistance, and electrical insulation have been raised due to the presence of voids inside the cured product after molding.

[0003]

For semiconductor encapsulation most suitable for manufacturing a semiconductor device which prevents generation of voids inside a cured product after forming a semiconductor package and has excellent reliability such as humidity resistance reliability. To provide a tablet.

[0004]

According to the present invention, a kneaded product of an epoxy resin composition containing an epoxy resin, a phenol resin curing agent, a curing accelerator, an inorganic filler and a silane coupling agent as essential components is pulverized. Grain size distribution is 9
0 to 15 μm or less for 0 μm or less, 5 to 91 to 500 μm
45% by weight, 501 to 1000 μm is 30 to 60% by weight, 1001 to 2300 μm is 0 to 10% by weight, 230
A tablet for semiconductor encapsulation, wherein 1 μm or more is 0% by weight, and the tableting density of the tablet obtained by press-molding the pulverized product is 91 to 99%.

The present invention will be described in detail below. The epoxy resin used in the present invention refers to all monomers, oligomers and polymers having an epoxy group, and the molecular weight and the molecular structure are not particularly limited. Examples thereof include, but are not limited to, bisphenol A type epoxy resin, biphenol type epoxy resin, orthocresol novolac type epoxy resin, naphthalene type epoxy resin, triphenol methane type epoxy resin and hydroquinone type epoxy resin. Further, these epoxy resins may be used alone or in combination. The phenol resin curing agent refers to all monomers, oligomers and polymers having a phenolic hydroxyl group capable of forming a crosslinked structure by curing reaction with the epoxy resin, and the molecular weight and the molecular structure are not particularly limited. Examples thereof include, but are not limited to, phenol novolac resin, paraxylylene-modified phenol resin, terpene-modified phenol resin, dicyclopentadiene-modified phenol resin, bisphenol A, and triphenolmethane.
Further, these phenol resin curing agents may be used alone or in combination.

[0006] The curing accelerator refers to one which can serve as a catalyst for the crosslinking reaction between the epoxy resin and the phenol resin curing agent, and specifically, amine compounds such as 1,8-diazabicycloundecene and triphenylphosphine. And organic phosphine compounds such as 2-methylimidazole and the like. Further, these curing accelerators may be used alone or in combination. Examples of the inorganic filler include fused silica powder, crystalline silica powder, alumina and silicon nitride. The blending amount of these inorganic fillers is 70 in the total epoxy resin composition from the balance of moldability and reliability.
It is preferable that the content is ˜90 wt%. Particularly in the case of a compound having a large amount of filler, spherical fused silica is generally used. Specific examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and vinyltriethoxysilane, but are not limited thereto. Not a thing. Further, these silane coupling agents may be used alone or in combination.

The epoxy resin composition used in the present invention contains an epoxy resin, a phenol resin curing agent, a curing accelerator, an inorganic filler and a silane coupling agent as essential components.
In addition to these, brominated epoxy resins, flame retardants such as antimony trioxide, colorants typified by carbon black, release agents such as natural wax and synthetic wax, silicone oil, silicone rubber, synthetic rubber, etc. The low-stress additive may be appropriately blended. When forming a molding material, all components are heated and kneaded by a heating kneader or a heating roll, followed by cooling, an Eck crusher, a medium crusher, and a horizontal type 1.
The desired epoxy resin composition for semiconductor encapsulation can be obtained by crushing with a shaft crusher or the like.

In order to obtain a semiconductor package having a small number of internal voids, which is the object of the present invention, voids contained in a tablet obtained by press-molding the epoxy resin composition for semiconductor encapsulation prepared above are formed. It is important to keep it as low as possible. In order to reduce voids, the particle size distribution of the epoxy resin composition pulverized by the above method should be 90
0 to 15% by weight for μm or less, 5 for 91 μm to 500 μm
~ 45 wt%, 501 ~ 1000 ~ 30 ~ 60
% Of 100% to 2300 μm, 0 to 10% by weight, and 2301 μm or more to 0% are molded into tablets using a pressure type tablet molding machine. The particle size distribution in the present invention was measured by a sieving method.

When the particle size of 90 μm or less in particle size distribution exceeds 15% by weight, the tableting density does not reach 91% or more, the porosity increases and the amount of internal voids does not decrease, and 1001 μm.
Particle size of ~ 2300 μm exceeds 10% by weight, or 2
Even if 301 μm or more is present, the porosity is large and the tableting density does not reach 91% or more, and the amount of internal voids does not decrease. Furthermore, if 91 to 500 μm is less than 5% by weight, 501 μm
It is not possible to sufficiently fill the gaps of the above particle size, and when it exceeds 45% by weight, the porosity is large, the tableting density does not reach 91% or more, and when 501 to 1000 μm is less than 30% by weight, it is 500 μm or less. The tableting density does not reach 91% or more due to the increase in the fine particles, and the porosity increases when the weight exceeds 60% by weight and the tablet density exceeds 91%.
% Tableting density cannot be obtained. The pressure for molding the tablet is not particularly limited, but is usually 10
It is 0 to 200 kg / cm ² . Even if the pulverized product having the particle size distribution of the present invention is used, if the tableting density is less than 91%, the porosity increases and the amount of internal voids does not decrease. When the pulverized product having the particle size distribution of the present invention is used and molded at the maximum molding pressure, the tableting density is about 98%. The tableting density of the tablet obtained by press-molding the epoxy resin composition is [tablet density = (tablet weight (g)) / (tablet volume (cm
³ ))] / [resin cured product density = (resin cured product weight (g)) / (resin cured product volume (cm ³ ))] × 100
Expressed as (%).

The present invention will be specifically described below with reference to examples. Example 1 Biphenyl type epoxy resin (melting point 103 ° C., epoxy equivalent 195) 8.3 parts by weight Paraxylylene modified phenol resin (softening point 70 ° C., hydroxyl equivalent 175) 3.04 parts by weight Phenol novolac resin (softening point 85 ° C., hydroxyl group Equivalent 105) 3.04 parts by weight Brominated bisphenol A type epoxy resin 1.0 parts by weight Triphenylphosphine 0.22 parts by weight Fused silica powder 81.5 parts by weight γ-aminopropyltriethoxysilane 0.6 parts by weight Trioxide Antimony 1.5 parts by weight Carnauba wax 0.5 parts by weight Carbon black 0.3 parts by weight are mixed with a mixer at room temperature and heated and kneaded by a twin-screw roll at 70 to 100 ° C., and the kneaded product is 2 by a sheeting roll.
A sheet having a thickness of mm was obtained, and the sheet was cooled and pulverized to obtain a sealing material. The particle size of the obtained molding material after crushing is adjusted, and the tablet is pressed by a tablet molding machine to prepare a tableting tablet, which is 175 ° C. at 75 kg / cm with a low-pressure transfer molding machine.
² , 160 seconds for internal void observation under the condition of 120 seconds
7. Sealed in pQFP and used for solder moisture resistance reliability test.
After mounting the chip of 5 × 7.5 mm, the bonding pad part of the chip and the lead frame were connected with a gold wire.
Sealed in pQFP. These test packages were post-cured at 175 ° C. for 8 hours after molding.

The following internal void observation and solder moisture resistance reliability test were conducted on the sealed package. Internal void observation: The inside of eight sealed packages was observed by using an ultrasonic flaw detector (mi-scope manufactured by Hitachi Construction Machinery Co., Ltd.), and the number of internal voids having a size of 30 μm or more was counted.
Expressed as an internal void. Solder Moisture Resistance Reliability Test: Sealed test element in an environment of 85 ° C, 85% RH 72
Time treatment, then IR reflow treatment at 240 ° C for 10 seconds, and pressure cooker test (125 ° C, 100%
RH), the open circuit failure was measured, and the pressure cooker processing time until the failure rate reached 50% was expressed as moisture resistance reliability. Table 1 shows the test results.

Examples 2 and 3 Blended in accordance with the formulation of Example 1 to obtain a molding material in the same manner, prepare particles after crushing and pressurize with a tablet molding machine to prepare tablets, and in the same manner as in Example 1. Internal void observation and solder moisture resistance reliability test were performed. Table 1 shows the test results. Comparative Examples 1 to 3 Compounded according to the formulation of Example 1, a molding material was obtained in the same manner, particles after pulverization were adjusted, and a tablet was prepared by pressurizing with a tablet molding machine, and internal voids were observed as in Example 1. And a solder moisture resistance reliability test was conducted. Table 1 shows the test results.

[0013]

[Table 1]

[0014]

According to the present invention, since the volume ratio of the air contained in the tablet obtained by pressure-molding the epoxy resin composition for semiconductor encapsulation is small, internal voids are almost generated in the molded product package. Without improving the adhesiveness between the chip and the frame, the adhesive force at these interfaces is increased, and the moisture absorption rate is lowered, so that the moisture resistance reliability after soldering is improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/56 C

Claims (1)

[Claims] 1. An epoxy resin, a phenol resin curing agent,
The particle size distribution of a pulverized product obtained by pulverizing a kneaded product of an epoxy resin composition containing a curing accelerator, an inorganic filler and a silane coupling agent as essential components is 0 to 15% by weight of 90 μm or less and 91 to 500 μm. 5 to 45% by weight, 501 to 10
00 μm is 30 to 60% by weight, 1001 to 2300 μm
Is 0 to 10% by weight, 2301 μm or more is 0% by weight, and the tableting density of the tablet obtained by press-molding the pulverized product is 9
A tablet for semiconductor encapsulation, which is 1 to 99%.