JPH05175370A - Epoxy resin molding material for sealing electronic component - Google Patents

Abstract

PURPOSE:To obtain an epoxy resin composition excellent in high Tg and reflow resistance by blending a specific epoxy resin having the naphthalene skeleton as the base resin. CONSTITUTION:A material comprises an epoxy resin represented by a formula, a phenolic novolak resin, and an inorganic filler of volume 60% or more. The epoxy resin has a naphthalene skeleton. This resin can be synthesized by epoxidizing a resin having dihydroxynaphthalen and naphthol as materials, which is obtainable by reacting them on a formaldehyde under an acid catalyst. The higher the ratio of the dihydroxynaphthalene, the higher become the glass transition temperature and the strength against higher temperatures. Also, the properties of the reflow cracking resistance become excellent. The equivalent ratio between the epoxy resin and the phenol resin should preferably be within a range of 0.8 to 1.3 from the viewpoint of the properties of setting, heat resistance, and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin molding material for encapsulating electronic parts, and is particularly applicable to surface mount plastic package ICs.

[0002]

2. Description of the Related Art Conventionally, epoxy resin molding materials have been widely used in the field of encapsulating electronic parts such as transistors and ICs. The reason for this is that the epoxy resin is well balanced in various characteristics such as electric characteristics, moisture resistance, heat resistance, mechanical characteristics, and adhesiveness with insert products. In particular, a combination of an oxocresol novolac type epoxy resin and a phenol novolac curing agent has an excellent balance of these, and has become the mainstream as a base resin for a molding material for IC encapsulation.

[0003]

In recent years, high-density mounting of electronic parts on a printed wiring board has been advanced, and along with this, electronic parts have been mainly used from a conventional pin insertion type package to a surface mount type package. Is becoming Surface mount ICs such as ICs and LSIs are thin and small packages in order to increase the mounting density and reduce the mounting height, and the volume occupied by the device with respect to the package is large, and the thickness of the package is very large. It's getting thinner. Furthermore, these packages are different in mounting method from the conventional pin insertion type. That is, in the pin insertion type package, after the pins are inserted into the wiring board, soldering is performed from the rear surface of the wiring board, so that the package is not directly exposed to high temperature. However, the surface-mount type IC is directly exposed to the soldering temperature because it is temporarily fixed to the surface of the wiring board and processed by a solder bath or a reflow device. As a result, when the IC package absorbs moisture, the absorbed moisture rapidly expands during soldering, which causes the package to crack. At present, this phenomenon is a big problem in the surface mount type IC.
In the IC package sealed with the current base resin composition,
Since the above problems cannot be avoided, methods are taken such as shipping the IC in moisture-proof packaging before shipment, or drying the IC sufficiently before mounting it on a wiring board. However, these methods are laborious and costly. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an epoxy resin molding material for electronic component encapsulation, which can be soldered without performing a specific pretreatment at the time of mounting on a wiring board. It is a thing.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors achieved the above object by blending a specific epoxy resin having a naphthalene skeleton as a base resin. Find out
The present invention has been completed. That is, the epoxy resin molding material for electronic component encapsulation of the present invention has (A) structural formula as the main component.

[Chemical 2] The epoxy resin (B) is a novolac resin of phenols and (C) 60% by volume or more of an inorganic filler.

The epoxy resin (A) in the present invention has a naphthalene skeleton, and the purity of the epoxy resin, particularly the amount of hydrolyzable chlorine, is preferably related to the corrosion of aluminum wiring on elements such as ICs, and therefore it is preferable that the epoxy resin is low in moisture resistance. 50 to obtain an epoxy resin molding material with excellent electrical properties for encapsulating electronic components
It is preferably 0 ppm or less, but is not particularly limited. Here, the amount of hydrolyzable chlorine means that 1 g of epoxy resin as a sample is dissolved in 30 ml of dioxane to prepare 1N-KOH.
A value obtained by potentiometric titration after adding 5 ml of a methanol solution and refluxing for 30 minutes is used as a scale. The epoxy resin (A) can be synthesized by epoxidizing a resin obtained by reacting dihydroxynaphthalene and naphthol as raw materials with formaldehyde under an acid catalyst. The higher the proportion of dihydroxynaphthalene, the higher the glass transition temperature, It was found that the high temperature strength was high and the reflow crack resistance was also excellent. Further, in order to efficiently obtain the structure shown in (A), it is desirable to use 2,7-dihydroxynaphthalene and β-naphthol as raw materials.

As the epoxy resin used in the present invention, in addition to the epoxy resin represented by the structural formula (A) above, it is used in combination with a resin generally used in epoxy resin molding materials for sealing electronic parts. Good. For example, phenol novolac type epoxy resin, epoxidized novolac resin of phenols and aldehydes including oxocresol novolac type epoxy resin, glycidyl amine type epoxy resin, and alicyclic epoxy resin Therefore, any number of these can be used in combination. When these epoxy resins are used in combination, there is no particular limitation, but the compounding ratio of the epoxy resin (A) of the present invention is preferably 30% by weight or more, and more preferably 50% by weight or more based on the whole epoxy resin. The reason for this is that if it is less than 30% by weight, the effect on the reflow resistance, which is the object of the present invention, is small, and 50% by weight or more is necessary for exhibiting a particularly effective effect. Further, examples of the phenol novolak resin (B) of the present invention include resins obtained by condensation and / or cocondensation of phenol, cresol, naphthol and the like with aldehydes. The equivalent ratio of the epoxy resin used in the present invention to the phenol resin (B) is preferably in the range of 0.8 to 1.3 from the viewpoint of curability, heat resistance and the like.

Further, a curing accelerator that accelerates the curing reaction between the epoxy resin and the phenol resin can be used.
Examples of the curing accelerator include 1,8-diazabicyclo (5,4,0) undecene-7, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris (dimethylaminomethyl) phenol. Secondary amines, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, imidazoles such as 2-heptadecylimidazole, tributylphosphine,
Organic phosphines such as methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, phenylphosphine, etc., tetra-substituted phosphonium tetra-, such as tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium ethyl triphenylborate, tetrabutylphosphonium tetrabutylborate, etc. There are tetraphenylboron salts such as substituted borates, 2-ethyl-4-methylimidazole tetraphenylborate, N-methylmorpholine tetraphenylborate and the like.

Further, as the filler, it is necessary to use an inorganic filler from the viewpoint of reducing hygroscopicity and improving strength.
As the inorganic filler, crystalline silica, fused silica, alumina, zircon, calcium silicate, calcium carbonate, silicon carbide, silicon nitride, boron nitride, zirconia, zircon,
Fosterite, steatite, spinel, mullite,
Examples thereof include powders such as titania and beads obtained by making them spherical, and one or more types can be used. For the same reason, the compounding amount of the filler needs to be 60% by volume or more, and more preferably 65% by volume or more. Other additives include higher fatty acids, higher fatty acid metal salts, release agents such as ester waxes, colorants such as carbon black, epoxysilanes, aminosilanes, ureidosilanes, vinylsilanes, alkylsilanes, organic titanates,
A coupling agent such as aluminum alcoholate and a flame retardant can be used. As a general method for producing a molding material using the above raw materials, after thoroughly mixing a predetermined amount of raw materials with a mixer or the like, kneading with a mixing roll, an extruder, etc., cooling, and pulverizing A molding material can be obtained by A low-pressure transfer molding method is the most general method for sealing an electronic component using the molding material obtained in the present invention, but an injection molding method or a compression molding method is also possible.

[0009]

The damage that the IC package receives during reflow is caused by the moisture absorbed during storage of the IC rapidly expanding during reflow, resulting in cracks in the package and separation of the resin interface from the element or lead frame. .. Therefore, a resin that is resistant to reflow is required to have low water absorption and high strength at high temperatures. The epoxy resin which is the main component of the present invention is a naphthalene skeleton type resin having excellent skeleton rigidity and hydrophobicity, and since it has many epoxy groups, high temperature strength is high and a composition excellent in hygroscopic property can be obtained. Can be inferred. It is considered that this effect improved the reflow crack resistance.

[0010]

EXAMPLES The present invention is described below with reference to examples, but the scope of the present invention is not limited to these examples.

Example 1 The structural formula is

[Chemical 3] 80 parts by weight of an epoxy resin having an epoxy equivalent of 182, 106 parts of a hydroxyl group, 52 parts by weight of a phenol novolac resin having a softening point of 83 ° C., 20 parts by weight of a brominated bisphenol A type epoxy resin having a bromine ratio of 50% by weight and an epoxy equivalent of 375. , Triphenylphosphine (2.5 parts by weight), carnauba wax (3 parts by weight), carbon black (1 part by weight), γ-glycidoxypropyltrimethoxysilane (4 parts by weight), quartz glass powder (75% by weight) ) Was mixed and a heating roll having a diameter of 10 inches was used to prepare the epoxy resin molding material of Example 1 under the conditions of a kneading temperature of 80 to 90 ° C. and a kneading time of 7 to 10 minutes.

Example 2 The epoxy resin of Example 1 has the structural formula

[Chemical 4] Was produced in the same manner as in Example 1 except that the epoxy resin having an epoxy equivalent of 160 was replaced with the epoxy resin and the compounding amount of the phenol novolac resin was 59 parts by weight. The comparative example uses the epoxy resin of Example 1 with an epoxy equivalent of 200 and a softening point of 73 ° C.
80 parts by weight of oxocresol novolac type epoxy resin, and the compounding amount of phenol novolac resin is 4
It was produced in the same manner as in Example 1 except that 8 parts by weight was used.

The characteristics of Examples 1 and 2 and Comparative Example are shown in Table 1.
Details of the test method are shown in Table 2. In order to clarify the effects of the present invention, the results of crack resistance during reflow using the evaluation IC and moisture resistance after reflow are shown. The IC used for the crack resistance evaluation is a flat package with an outer shape of 19 × 14 × 2.0 (mm), and an 80-pin, 42-alloy lead with an 8 × 10 × 0.4 (mm) element mounted. Is. The test conditions are such that after humidifying at 85 ° C. and 85% RH for a predetermined time, it is heated in a vapor phase reflow furnace at 215 ° C. for 90 seconds. The evaluation was performed by observing the appearance with a microscope and determining the presence or absence of package cracks. Molding of IC package is 180 ℃, 90 seconds, 70kgf / cm
^The molding was performed under the conditions of ² , and after molding, post-curing was performed at 180 ° C. for 5 hours. Table 3 shows the results of the crack resistance test during reflow. The examples were superior in Tg and high temperature strength to the comparative examples, and as a result, good reflow properties were exhibited.

[0012]

[Table 1]

[Table 2]

[Table 3]

[0013]

The epoxy resin molding material obtained according to the present invention can greatly improve the crack resistance during reflow and the moisture resistance after reflow as compared with the conventional ones. In the field of electronic parts, especially in ICs such as FP (flat package) and SOP (small outline package), the package is thin and small, and in combination with the increase in size of the device, package crack resistance is strongly required. , Can be widely applied to these products, and its industrial value is great.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area C08L 63/00 NKT 8830-4J

Claims (1)

[Claims] 1. A structural formula of (A) as a main component is An epoxy resin molding material for electronic component encapsulation, comprising: (B) a phenolic novolak resin and (C) 60% by volume or more of an inorganic filler.