JPH09216936A - Cure accelerator for epoxy resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cure accelerator which retains adhesion characteristic of a phenol novolac salt of DBU and is improved in storage stability in which it is not satisfactory. SOLUTION: This accelerator is prepared by homogeneously melt-mixing 10-20wt.% 1,8-diazabicyclo(5,4,0)undecene-7 (DBU) with 6-18wt.% tetraphenylphosphonium tetraphenylborate and 62-84wt.% phenol novolac resin at 160-220 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin curing accelerator useful for encapsulating electronic parts such as semiconductor encapsulants.

[0002]

2. Description of the Related Art Epoxy resins containing phenol novolacs as a curing agent and a large amount of fillers are excellent in moldability or electrical properties of cured products, and are suitable for encapsulation of electronic parts such as semiconductor encapsulants. Widely used. In recent years, along with the high integration of semiconductors, thinning, or improvement of mounting method, the moldability or storage stability of the encapsulant,
Further, there is a strong demand for improving the reliability of the encapsulated semiconductor, and in response to this demand, the role of the curing accelerator, which is one component of the encapsulating material, is also increasing. 1,8-diazabicyclo (5,4,4) as a curing accelerator for semiconductor encapsulants
0) Undecene-7 (hereinafter abbreviated as DBU), its phenol novolac salt, etc. are already widely known, and for example, provide an encapsulant excellent in adhesion, which is one of the important factors of reliability. (For example, Japanese Patent Fairness 6
-57745 and JP-A-4-369254). However, the performance of these encapsulants is easily affected by the water content of the compounding system, the type of compounding raw materials, molding conditions, etc., and strict process control is required to fully demonstrate the performance. Further, as a result, in the case where the addition amount of DBU is increased, there is a problem that the moldability such as fluidity of the sealing material is adversely affected.

[0003]

In order to solve these problems, DBU or its salts and other curing accelerators,
For example, many methods have already been known in which imidazoles, secondary and tertiary amines, triphenylphosphine, tetraphenylphosphonium tetraphenylborate (hereinafter abbreviated as TPP-B), and the like are used in combination (for example, a special method). JP-A-58-57427 or JP-A-3-157447
Reference). However, these combinations are also associated with the drawbacks of the respective curing accelerators. For example, the combined use of imidazoles and the like causes a large decrease in reliability even with a small amount of combined use, and TPP-B has long been known as a curing accelerator characterized by its latent property. Even when used together, it is extremely difficult to control the process for exhibiting stable performance. Furthermore, TPP
The combination of -B and phenol novolacs (for example, Japanese Patent Laid-Open No. 54-58795) has a drawback that the catalyst activity and the like change due to the difference in thermal history due to the difference in the compounding method. Therefore, an object of the present invention is to provide a curing accelerator for an epoxy resin that has improved adhesiveness, which is a drawback of DBU's phenol novolac salt, while improving its storage stability.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has found that 10 to 20% by weight of 1,
8-diazabicyclo (5,4,0) undecene-7,6
~ 18% by weight of tetraphenylphosphonium tetraphenylborate and 62 ~ 84% by weight of phenol novolaks are uniformly melt-mixed at a temperature of 160 ~ 220 ° C. Heading, completed the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The curing accelerator of the present invention can be produced, for example, according to the method described in JP-B-6-57745. Since DBU and phenol novolacs are likely to form a non-uniform salt, it is important to mix them uniformly in order to exert stable performance. For example, phenol novolacs melted at a temperature above the softening point should be mixed with DBU under stirring. And TPP-B were added, and at 160-220 ° C, 1
It can be produced by uniformly mixing and taking out for about 5 hours, cooling, and usually finely pulverizing. If the mixing temperature is 160 ° C. or less, stable performance cannot be obtained, while if it exceeds 220 ° C., thermal decomposition of phenol novolacs generally begins to occur, which is not preferable. Regarding the order of addition of DBU and TPP-B, the viscosity was high after addition of DBU and TP
Since it is difficult to remove bubbles generated by heat treatment of P-B, it is preferable to add TPP-B first, defoam at the same temperature for 1 to 3 hours, and then add DBU. The defoaming step is preferably finally performed under reduced pressure. The temperature after uniform mixing, for example, the temperature at the time of taking out is preferably as low as 200 ° C. or less as much as possible from the viewpoint of safety and yield, and 20 ° C. or more higher than the softening point of the product. It should be noted that the present invention does not prevent the curing accelerator separately produced using DBU or TPP-B by the above method from being used together during the production of the encapsulant. One of the advantages of the present invention is to avoid a complicated work such as using a small amount of the curing accelerator, which is harmful to the process control of the sealing material.

As the phenol novolacs used in the curing accelerator of the present invention, the same phenol novolacs as the encapsulant curing agent can be used, for example, the softening point.
Examples include phenol novolac at 50 to 120 ° C., cresol novolac, xylylene phenol resin, and dichloropentadiene phenol resin. The amount of DBU in the curing accelerator of the present invention is 10 to 20% by weight, which is a standard for forming a stable salt with phenol novolacs, and the optimum amount is set depending on the type of phenol novolacs. However, if the content is 10% by weight or less, the moisture absorption of the curing accelerator itself becomes strong, which is not preferable. The amount of TPP-B is 6-18% by weight,
If it is less than 10% by weight, the effect of combination is not recognized, while 18% by weight
The above is not preferable because the adhesion is deteriorated.

The curing accelerator of the present invention is used as a curing accelerator for an epoxy resin containing the above-mentioned phenol novolacs and a filler. As the epoxy compound, a solid one is usually used, and for example, a known bisphenol A type epoxy, an epoxy compound obtained by glycidylation of the phenol novolacs, biphenyl epoxy, brominated phenol novolac epoxy, triglycidyl isocyanurate, etc. Is mentioned. The epoxy resin may be a system in which other additives such as a release agent, a colorant, a flame retardant, a stress reducing agent, a filler coupling treatment agent, and an ion scavenger are blended, if necessary. It goes without saying that it is good. The addition amount of the curing accelerator of the present invention is usually DBU with respect to 100 parts by weight of the epoxy compound.
And TPP-B are 0.5 to 4.0 parts by weight in total, and the optimum addition amount is set according to the required curability and the like.

[0008]

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to the description of the examples. (Example) In a nitrogen stream, 518 g of phenol novolac (softening point 80 ° C) was charged into a 1-liter volume Kolben, and 1
Melts uniformly at 40-150 ℃. Then under stirring TPP
-B (manufactured by Wako Pure Chemical Industries, Ltd.) 84g and gradually added 190
The temperature was raised to 0 ° C., and the mixture was mixed at the same temperature for 1 hour, and then gradually depressurized to defoam (final degree of reduced pressure: about 20 mmHg). Next, the mixture was cooled to 170 ° C, 98 g of DBU (manufactured by San-Apro Co., Ltd.) was gradually added, the temperature was raised to 180-190 ° C using the heat of neutralization, the mixture was mixed at the same temperature for 1 hour, and then taken out in a vat. As a result, 650 g of a yellowish brown homogeneous transparent resin was obtained. This was cooled and then finely pulverized to obtain the curing accelerator of the example. The blending ratio of DBU and TPP-B was determined by NMR analysis using the absorption intensity (area ratio) of H of a part of the methylene groups of DBU and all H of the tetraphenylphosphonium group of TPP-B. I confirmed it. (Comparative Examples 1 and 2) Phenol novolac, TPP-
The curing accelerators of Comparative Examples 1 and 2 were obtained in the same manner as in Example except that the mixing ratios of B and DBU were as shown in Table 1.

[0009]

[Table 1]

Test Examples 1 to 5 Next, an o-cresol novolac epoxy resin having a softening point of 72 ° C. and an epoxy equivalent of 195: 90 parts by weight, a brominated phenol novolac epoxy resin having a softening point of 85 ° C. and an epoxy equivalent of 275: 10 Parts by weight, softening point
Phenol novolac resin at 80 ° C (shows the value including the amount of phenol novolac as a curing accelerator): 50 parts by weight, 1
Fused silica powder treated with wt% silane coupling agent: 400 parts by weight, carnauba wax: 1.5 parts by weight, antimony trioxide: 4 parts by weight, carbon black: 1 part by weight, the curing accelerator obtained in each example and Table 2 for TPP-B
After uniformly pulverizing and mixing with the blending ratio shown in (indicated by the value converted to the amount of DBU and TPP-B), melt mixing for 5 minutes using a hot roll at 100 ° C., cooling and pulverizing to obtain a sealing material. It was For this encapsulant, measure the gel time and flow value (fluidity) by the following methods, and seal the encapsulant at 175 ° C x 2
Transfer molding was performed under the condition of minute (pressing pressure 70 kg / cm ² ) and the hardness immediately after demolding was measured using a Bacol hardness meter. Further, the glass transition temperature (Tg) of the sample which was post-cured under the condition of 175 ° C. × 6 hours was measured after transfer molding the sealing material under the condition of 175 ° C. × 3 minutes. Similarly, the test semiconductor element was sealed with each sealing material, and the reflow crack (adhesion) was measured. On the other hand, the encapsulant was stored under certain conditions, and the Bacol hardness and the glass transition temperature (Tg) were measured to evaluate the storage stability (influence of moisture). These results are shown in Table 2.

(Test method) -Gel time: Hot plate method (175 ° C) -Flow value: 175 ° C according to the method of EMMI 1-66
Measures spiral flow at (70kg / cm ² ) ・ Tg: TMA method ・ Reflow crack: 85% RH /
It was left in an atmosphere of 85 ° C for 72 hours and then immersed in a solder bath at 240 ° C for 30 seconds to determine the number of cracks.・ Storage stability: Put the encapsulant in an open container, 75% RH / 30
Leave in the atmosphere at ℃. After mixing every 1 hour and absorbing moisture for a total of 8 hours, transfer molding was carried out in the same manner, or after transfer molding, post-curing was carried out and measurement was carried out.

[0012]

[Table 2]

From Table 2, it can be seen that the curing accelerator of the present invention is one of the characteristics of DBU phenol novolac salt, which is widely used as a curing accelerator for epoxy resins such as semiconductor encapsulants, and the like. It has been found that the reflow cracking property) is maintained and the storage stability, which is a major drawback, is improved.

[0014]

The curing accelerator of the present invention provides an epoxy resin having excellent moldability, storage stability and adhesion.
Particularly, stable performance is excellent from the viewpoint of process control of epoxy resin, and is extremely useful as a curing accelerator for epoxy resin such as semiconductor encapsulant.

Claims (1)

[Claims] 1. 10 to 20% by weight of 1,8-diazabicyclo (5,4,0) undecene-7, 6 to 18% by weight of tetraphenylphosphonium tetraphenylborate and
62-84% by weight of phenol novolacs, 160-220
A curing accelerator for an epoxy resin, characterized by being uniformly melt-mixed at a temperature of ° C.