JPS5975923A - Epoxy resin composition for semiconductor sealing - Google Patents

Abstract

PURPOSE:The titled resin composition excellent in storage stability and electrical properties, prepared by adding a specified phenylborate as a cure accelerator to a novolak epoxy resin composition. CONSTITUTION:As a cure accelerator there is used tetraphenylborate of 1,8- diazabicyclo(5.4.0)undencene-7. Namely, 4-20wt%, based on curing agent, above phenylborate is added to a composition comprising a novolak epoxy resin [a polymer prepared by condensing a phenol (phenol, cresol, xylenol, or the like) with a formaldehyde with the aid of an acid catalyst to form novolak, and then etherifying this novolak with epichlorohydrin into a glycidyl ether] and novolak of the above phenol (curing agent).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an epoxy resin composition for semiconductor encapsulation that has excellent storage stability and excellent electrical properties.

Low-pressure transfer molding using epoxy resin has become mainstream for semiconductor encapsulation due to its economical advantages, and among these, systems in which novolac-based epoxy resin with excellent moisture resistance is cured with phenol novolac are preferred. In this system, it is common to use a curing accelerator to shorten the cycle during molding, and in order to achieve a curing speed that can be put to practical use, the reaction progresses even at room temperature, and the molding material is stored during storage. The pressure flow is shortened, causing molding problems or the inability to mold.For this reason, the molding material must be stored and transported at low temperatures, resulting in great inconvenience and cost.Furthermore, the addition of a curing accelerator is necessary. This generally results in impurities being introduced into the material, which deteriorates the electrical properties of the material.This is fatal to modern molding materials for semiconductor encapsulation, which require increasingly high reliability.

There has been a long-awaited need for a curing accelerator that has rapid reactivity during molding, does not react at the storage temperature (room temperature) of the material, that is, has latent properties, and does not reduce the electrical properties of the molding material. .

Many studies have been conducted on such curing accelerators.

Boron salts of amines or boron complex salts of amines have long been known as curing accelerators that improve latent properties, but these have poor electrical properties and are slow to cure and cannot be used for the intended molding material. It wasn't. As an improvement, there is an example of using an amine salt of a tetraphenylborate salt (e.g. EVA JP-A-49-118798), but the electrical properties were insufficient, and the amine was limited to triethylammonium, and the amine was mixed with a curing agent in advance. Considerable improvements have been made to the electrical characteristics by the method (for example, JP-A-54-110297).

We have continued to conduct intensive studies to achieve both superior electrical properties and storage stability, and as a result, we have arrived at this invention.

That is, the gist of the present invention is that in a system using a novolak epoxy resin and a phenolic novolak as a curing agent, 1.8 diazabicyclo(5,4,0) undecene 7 (hereinafter referred to as It is called OBU.)
4 to 20 parts by weight, preferably 5 to 10 parts by weight, of tetraphenylborate (hereinafter referred to as TPB) to the curing agent are blended in advance in solid form with the curing agent.

Particularly suitable as the novolac-based epoxy resin are resins produced by condensing phenol, cresol, xylenol, etc. with formaldehyde, etc. using an acidic catalyst as a raw material, and glycidyl etherified with epichlorohydrin.

Furthermore, as the novolac of heptanenol as a curing agent, those similar to the above-mentioned raw material novolak are particularly suitable.

Only by combining these with the DBU-TPB curing accelerator will the objective be achieved. It is already known to use DBU or its salt as a curing accelerator (
For example, JP-A-51-26999) does not have latent properties, and can only be imparted with latent properties by complex salts such as BP, BF4° salts, and TPB salts, but from this point of view, TPB salts do not have sufficient electrical properties. Required.

The blending amount is 4 to 20 parts by weight, preferably 5 parts by weight based on the curing agent.
~10 parts by weight. If the amount is less than this, the material will not have sufficient curability, and if it is too much, the curing accelerator will be too bulky, resulting in poor mixing and adversely affecting the properties.

The method of addition is triblend to the curing agent. In order to maintain the electrical properties, there is a method of mixing with a curing agent (for example, Japanese Patent Application Laid-Open No. 110297/1983), but when mixing, the incubation property of the liver and kidneys is impaired. DBU-TPB does not mix and melt, and sufficient electrical properties can be obtained with Drablend. As a method, a blender or the like may be used, but it is preferable to use a ball mill to obtain good results. These resin-hardening accelerator systems contain inorganic fillers, mold release agents,
Colorants and other additives, etc., and the usual methods (roll cross-wiring,
It is kneaded by screw extrusion (mixing wire, etc.) and used as a molding material.

This will be explained below using examples. Amounts are expressed in parts by weight unless otherwise noted.

Example 1 10 parts of phenol novolak curing agent and 1.0 part of DBU-TPB salt were pulverized and mixed for 1 hour using a ball mill.

This was blended with 20 parts of epoxy orthocresol novolak, 64 parts of fused silica powder, 1.0 part of stearic acid, 2.0 parts of a 7-run coupling agent, and 2.0 parts of carbon black, and heated with a hot roll at 70 to 90°C. After cooling for about 10 minutes, the mixture was crushed to obtain a molding material.

Using this material, curability, material storage stability, and volume resistivity at 150°C were measured (measurement methods will be described later).

From Table 1, it shows that both curability and preservability are achieved, and the volume resistivity at 150°C is also at a high level.

Example 2 A material was obtained in the same manner as in Example 1 using epoxyphenol novolac instead of epoxy orthocresol novolac, and the results shown in Table 1 were obtained.

A material with properties similar to those of Example 1 was obtained.

Comparative example 1゜ Triethylamine-TPB as curing accelerator.

Using 2-methylimidazole-TPB salt and materials obtained in the same manner as in Example 1, the results shown in Table 1 were obtained.

Although the storage stability is good, the volume resistivity is inferior to that of Example 1. This level is low for LSI.

Comparative Example 2 Using a phenol salt of DBU and 2-ethylhexanoate as a curing accelerator, and using a material obtained in the same manner as in Example 1, the results shown in Table 1 were obtained. Although its electrical properties are good, it shows no latent properties and is no better than conventional materials.

Example 3 A material with the same composition as in Example 1 was obtained using a co-kneader instead of a roll.

Co-kneader conditions Initial flow: 90α Flow residual rate: 92% Curing property: 70 Volume resistivity (150°C): 6.8×10 The target material is obtained in the same way as 130-L.

Example 4 DBtJ- for 100 parts of phenol novolac curing agent
Add 0.4 parts and 2 parts of TPB, respectively,
The rest of the material was obtained by the method of Example 1. When 2 parts of curing accelerator was added during material trial production, the curing accelerator was bulky, and mixing in a ball mill took time. Table 2 characteristics
Shown below. 0.4 parts is the lower limit in terms of curability, and 2 parts is the upper limit in terms of electrical characteristics, spiral flow, and material production.

Table 2 Example 5 40 parts of phenol novolak curing agent and DBLI-TPB
1.0 parts were melt-mixed at 150°C. The melt forms a transparent homogeneous layer. After cooling, the material was pulverized in the same manner as in Example 1 to obtain a material. The flow changes are as follows.

Initial flow 75 crL Flow residual rate 50% (40°C 7 days) Example 6 Using the material of Example 1, a reliability test was conducted using a simulated element.

A simulated element with aluminum wiring is enclosed in material 1
It was treated in water vapor at 20° C. and 2.2 atm, and the deterioration of its insulation resistance was monitored.

As the blank, a commercially available molding material for LSI encapsulation was used. As a result, the material of the present invention showed good results.

Table 3 Shown as defective rate out of 10 items.

Measurement method (1) A molded product of 10 x 50 x 3 m was molded using e-transfer molding, and after 10" of removal from the mold, it was measured using a Barcol hardness tester (
4935) to measure the hardness when heated.

Molding conditions are pressure 50 Ky/ci, 165°C, 90″
It is.

(2) Preservability The material was placed in a polyethylene bag and stored in a dryer at 40° C. for a certain period of time, and the EMM method spiral flow was measured for the flow before and after storage.

(3) Volume resistivity at 150°C According to the volume resistivity measuring method of JIS6911, the sample was left in an atmosphere K at 150°C for 30 minutes and then measured in the same atmosphere. The test piece used was after-cured at 165°C for 12 hours.

Claims (3)

[Claims] (1) In a system that uses a novolac epoxy resin and a phenolic novolac as a curing agent, a tetraphenylborate salt of 1.8 diazabicyclo(5,4,0) undecene 7 is used as a curing accelerator. Against 4-2
An epoxy resin composition characterized in that 0 parts by weight, preferably 5 to 10 parts by weight, is blended in advance with a curing agent in a solid state. (2) Novolac-based epoxy resin or (and) phenolic novolac as a curing agent is glycidyl etherified with epichlorohydrin using a resin produced by condensing phenol, cresol, or xylenol, etc., and formaldehyde, etc. with an acidic catalyst as a raw material. An epoxy resin composition according to claim (1). (3) The epoxy resin composition according to claim 1 or 2, wherein the tetraphenylborate salt of 1.8 diazabicyclo(5,4,0) undecene 7 is contained in an amount of 5 to 10 parts by weight.