JPH0220548A - Sealing resin composition - Google Patents

Abstract

PURPOSE:To obtain a sealing resin composition having a high thermal conductivity and a low coefficient of thermal expansion and excelling in moldability and humidity resistance by adding a specified silicon nitride powder to an epoxy resin containing a novolac phenol resin as a curing agent. CONSTITUTION:A sealing resin composition is obtained by using an epoxy resin (A), a novolac phenol resin (B) and a fine silicon nitride powder (C) of a mean particle diameter <=60 mesh and a metallic silicon content <=1% as essential components in such amounts that component C is 25-90wt.% based on the total resin components. The above composition has a high thermal conductivity and a low coefficient of thermal expansion and excels in moldability and humidity resistance, is freed of problems such as opening of a bonding wire, resin crack and pellet crack, has a good balance among various properties and high reliability and is suitable for sealing electronic and electric components.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention provides a seal with a good balance of properties, which has high thermal conductivity, low thermal expansion coefficient, and excellent moldability and moisture resistance. The present invention relates to a resin composition for stopping use.

(Prior Art) Conventionally, a method has been used in which electronic components such as diodes, transistors, and integrated circuits are sealed with a thermosetting resin. This resin sealing is economically advantageous compared to hermetic sealing methods using glass, metal, or ceramic, and is therefore widely put into practical use. Among thermosetting resins, epoxy resin is most commonly used as the sealing resin in terms of reliability and cost. For epoxy resins, curing agents such as acid anhydrides, aromatic amines, and novolac-type phenolic resins are used. Among these, epoxy resins using novolac type phenolic resin as a curing agent have better moldability and better moldability than those using other curing agents.
It is widely used as a resin for semiconductor encapsulation because it has excellent moisture resistance, is nontoxic, and is inexpensive. On the other hand, as a filler, fused silica powder or crystalline silica powder is most commonly used together with the above-mentioned curing agent. In recent years, as semiconductor components have become more highly integrated, there has been a demand for resins for semiconductor encapsulation that have a small coefficient of thermal expansion and that have better heat dissipation properties as electric power increases.

However, sealing resins made of epoxy resins using novolac-type phenolic resin as a curing agent and fused silica powder have a relatively small coefficient of thermal expansion, and therefore have poor moisture resistance, as well as bonding wires that have been tested in hot and cold cycle tests related to moisture absorption. Although it has the feature of being excellent in resisting cracks in plastics, resin cracks, pellet cracks, etc.
Since the thermal conductivity is low, heat dissipation is poor, and a power semiconductor with a large dissipated power cannot perform its function. On the other hand, for sealing resins made of epoxy resins using novolac-type phenolic resin as a curing agent and crystalline silica powder, increasing the blending ratio of crystalline silica powder increases thermal conductivity and improves heat dissipation. However, it has the drawbacks of a large coefficient of thermal expansion and reduced reliability in moisture resistance. Furthermore, molded products obtained from the latter sealing resin tend to have poor mechanical properties and moldability. Therefore, there is a natural limit to increasing the thermal conductivity of a sealing resin using crystalline silica powder.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and its purpose is to have high thermal conductivity and excellent heat dissipation, while having a small coefficient of thermal expansion and good moldability. , 111 aims to provide a highly reliable sealing resin composition with excellent moisture properties and well-balanced properties.

[Structure of the Invention] (Means for Solving the Problems) As a result of intensive research to achieve the above object, the present inventors have developed a fine grain with an average grain size of 60 mesh or less and a metal silicon content. It was discovered that the above object could be achieved by blending 1% or less of silicon nitride powder, and the present invention was completed.

That is, the present invention uses (A) an epoxy resin, (B) a novolac type phenolic resin, and (C) fine particles with an average particle size of 60 mesh or more and a metal silicon content of 1%.
This is a sealing resin composition characterized in that the following silicon nitride powder is an essential component, and the silicon nitride powder (C) is contained in a proportion of 25 to 90% by weight based on the entire resin composition.

The epoxy resin (A) used in the present invention is not particularly limited in molecular structure, molecular weight, etc., as long as it is a compound having at least two epoxy groups in its molecule, and can include a wide range of commonly used epoxy resins. can. Examples include aromatic resins such as bisphenol type, alicyclic resins such as cyclohexane derivatives, and epoxy novolac type epoxy resins represented by the following general formula.

(However, in the formula, R1 represents a hydrogen atom, a halogen atom, or an alkyl group, R2 represents a hydrogen atom or an alkyl group, and n represents an integer of 1 or more.) These epoxy resins may be used alone or in combination.
Can be used in combination of more than one species.

The novolak phenolic resin (B) used in the present invention includes novolak phenolic resins obtained by reacting phenols such as phenol and alkylphenols with formaldehyde or paraformaldehyde, and modified resins thereof, such as epoxidized or butylated novolaks. Examples include type phenol resins, and these can be used alone or in a mixture of two or more. The blending ratio of the novolac type phenolic resin is such that the molar ratio [(a)/(b)] of the epoxy group (a) of the epoxy resin (A) and the phenolic hydroxyl group (b) of the novolac type phenol resin (B) is It is necessary that it be within the range of 0.1 to 10. This is because if the molar ratio is less than 0.1 or more than 10, the moisture resistance, moldability, and electrical properties of the cured product will be poor, which is undesirable in either case.

The silicon nitride powder (C) used in the present invention has an average particle size of 6
Fine particles with a mesh size of 0 or more and a content of unreacted metal silicon of 1% or less. If the silicon nitride powder is coarse particles with an average particle size of less than 60 mesh, it is not preferable because gate clogging during molding may cause wire flow, die erosion, etc. Furthermore, if the content of unreacted metallic silicon in the silicon nitride powder exceeds 1%, it is undesirable because it will reduce dielectric breakdown and cause leakage defects in products. -3i 3N, ) or hexagonal system (β-3i3N4), and these can be used alone or in a mixture of two or more.
The blending ratio of silicon nitride powder is preferably 25 to 90% by weight based on the entire resin composition. If the blending ratio is less than 25% by weight, the coefficient of thermal expansion is large and the thermal conductivity is low, so it is preferable. If it exceeds 90% by weight, the coverage is large and the moldability is poor, making it unsuitable for practical use. Therefore, it is limited to the above range.

The sealing resin composition of the present invention contains an epoxy resin, a novolac type phenolic resin, and a silicon nitride powder as essential components, but may optionally include natural waxes, synthetic waxes, etc., as long as it does not contradict the purpose of the present invention. metal salts of straight-chain fatty acids, acid amides, esters, mold release agents such as paraffins, flame retardants such as chlorinated paraffin, bromotoluene, hexabromobenzene, antimony trioxide, and coloring such as carbon black and red iron. Agents, silane coupling agents, various curing accelerators, etc. can be added and blended as appropriate.

As a general method for manufacturing the sealing resin composition of the present invention as a molding material, raw material compositions containing epoxy resin, novolak type phenol resin, silicon nitride powder, and others selected at a predetermined composition ratio are mixed using a mixer or the like. After sufficiently uniformly mixing the mixture, the mixture is further melted and mixed using hot rolls, or mixed using a kneader, etc., and then cooled and solidified.
It can be crushed into a suitable size and used as a molding material.

The molding material produced in this manner can be used for sealing electronic or electrical parts, and when applied to coatings, insulation, etc., can provide excellent properties and reliability.

(Function) The sealing resin composition of the present invention achieves its purpose by blending a predetermined amount of silicon nitride powder with a specific size and low content of unreacted metal silicon. That is, since the silicon nitride powder has fine particles with an average particle size of 60 mesh or more, the flow during molding is good, and wear of the mold does not occur. In addition, since the unreacted metal silicon content is less than 1%, dielectric breakdown does not decrease.Furthermore, by incorporating 25 to 90% by weight of the entire resin composition, the thermal conductivity is high and the coefficient of thermal expansion can be reduced. can.

(Examples) Next, the present invention will be specifically explained using Examples, but the present invention is not limited to the following Examples.

In Examples and Comparative Examples, "%" means "% by weight"
” means.

Example 1 Cresol novolak epoxy resin (epoxy equivalent weight 21
5) 18%, novolac type phenolic resin (phenol equivalent: 107), 9% hexagonal silicon nitride powder (
Average particle size 7μl, unreacted metal silicon content 0.5%)7
0%, mold release agent, etc. 3% are mixed at room temperature, and further heated to 90-95℃
The molding material (A>) is produced by kneading, cooling and pulverizing.

Example 2 Instead of the hexagonal silicon nitride powder used in Example 1, hexagonal silicon nitride powder (average particle size 7 μm, unreacted metal silicon content 0.9% > 30%) and crystalline silica powder ( A molding material (B) was produced in the same manner as in Example 1 except that 40% (average particle size: 38 μm) was used.

Comparative example 1 Cresol novolak epoxy resin (epoxy equivalent) 1
8%, novolak type phenolic resin (phenol equivalent: 107) 9%, fused silica powder 70%, mold release agent, etc. 3
A molding material (C) was produced using the same percentage as in Example 1.

Comparative Example 2 A molding material (D) was produced in the same manner as in Comparative Example 1 except that crystalline silica powder (average particle size 28 μm) was used instead of fused silica powder.

Comparative Example 3 Cresol novolak epoxy resin (epoxy equivalent: 21
5) Molding material (E) was made in the same manner as in Comparative Example 1, except that 5% of novolac type phenol resin (i 107 per phenol) and 85% of crystalline silica powder (average particle size 28μ■) were used for 10%. was manufactured.

Comparative Example 4 Cresol novolak epoxy resin (epoxy equivalent: 21
5) All except that 18%, 9% novolac type phenolic resin, 70% hexagonal silicon nitride powder (average particle size 7 μl, unreacted metal silicon content 1.5%), and 3% mold release agent were used. A molding material (F) was produced in the same manner as in Comparative Example 1.

Molding material (A) manufactured in Examples 1-2 and Comparative Examples 1-4
- (F) was transfer-molded in a mold heated to 170°C and cured to obtain a molded product (sealed product).
The obtained molded product was tested for thermal conductivity, coefficient of thermal expansion, moldability, moisture resistance, and dielectric breakdown, and the results are shown in Table 1. In all cases, the remarkable effects of the present invention were confirmed.

*1: The obtained molded product was measured at room temperature using a rapid heat conduction needle (manufactured by Showa Denko K.K., trade name: QTM-MD).

*2: Using a 16-bin DIP mold with 120 cavities, transfer molding was performed at 170° C. for 3 minutes to evaluate filling properties.

*3: Using the molding material, an electrical component having two aluminum wirings was transfer molded at 170°C for 3 minutes, and then cured at 180°C for 8 hours. The 100 sealed electrical components thus obtained were subjected to a moisture resistance test in high-pressure steam at 120° C., and the time required for 50% disconnection (defect generation) due to aluminum corrosion to occur was determined.

[Effects of the Invention] As is clear from the above explanation and Table 1, the encapsulating resin composition of the present invention has high thermal conductivity, low thermal expansion coefficient, and excellent moldability and moisture resistance. Because of this, it is free from bonding wire ovens, resin cracks, and pellet cracks, and is highly reliable with well-balanced properties, making it suitable for sealing electronic and electrical parts.

Claims (1)

[Claims] 1. Essential components: (A) epoxy resin, (B) novolac type phenolic resin, and (C) fine grained silicon nitride powder with an average particle size of 60 mesh or more and a metal silicon content of 1% or less A sealing resin composition characterized in that the silicon nitride powder (C) is contained in a proportion of 25 to 90% by weight based on the entire resin composition.