JPH05217702A - Epoxy resin molding material for sealing electronic part - Google Patents

Abstract

PURPOSE:To improve resistance to reflow cracks by obtaining a composition excellent in heat resistance, moisture absorption property, etc., through use of diepoxy resin shown by the formula, phenol resin which includes a specified quantity of two-nucleus substance, and a specified quantity of inorganic filler. CONSTITUTION:The epoxy resin shown by the formula is obtained by epoxidation of 4,4'-bishydroxy 3,3',5,5'-tetramethylviphenyl. Though nothing is limited as regards the distribution of quantity of molecules of the novolak resin of phenol kind, the weight ratio of the ingredients below the two-nucleus substance is 15% or less. Moreover, as a filler, a 60volume% or more of inorganic filler is used for reduction of moisture absorption, etc. For example, 80 pts.wt. of epoxy resin shown by the figure and 50 pts.wt. of phenol novolar resin including 11.5wt.% two-nucleus substances are fused and mixed under the condition of 120 deg.C and 30min. and are cooled to get uniform solid resin. Each kind of additive and 70wt.% quartz glass powder are mixed to this resin, and a molding material is made under the condition of 80-90 deg.C in kneading temperature and 7-100min. in kneading time, using a heat roll of 10in. diameter.

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 orthocresol 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. Along with this, surface mount packages are becoming the mainstream for electronic components, instead of conventional pin insertion packages. Surface-mount type ICs such as ICs and LSIs have a thin and small package in order to increase the mounting density and reduce the mounting height, and the volume occupied by the device in the package is large, so that the package The wall thickness has become very thin. Further, 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 back 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 abruptly expands during soldering, which causes the package to crack. This phenomenon is a major problem in surface mount ICs. With the current IC package sealed with a base resin composition, the above problems are unavoidable, so the IC is shipped in a moisture-proof package before shipping, or the IC is sufficiently dried before it is mounted on a wiring board. The method of is taken. 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 specific pretreatment when mounted on a wiring board. Is.

[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 biphenyl skeleton as a base resin. Found 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 a main component

[Chemical 2] It is characterized in that the epoxy resin and the component (B) binuclear or less are composed of 15% by weight or less of a phenolic nopolak resin and (C) 60% by volume or more of an inorganic filler.

The epoxy resin (A) in the present invention has a biphenyl skeleton, and the purity of the epoxy resin is
In particular, the amount of hydrolyzable chlorine should be as small as possible because it is related to the corrosion of aluminum wiring on elements such as ICs. To obtain an epoxy resin molding material for encapsulating electronic parts with excellent moisture resistance, 500 p
It is preferably pm 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 was used as a scale. The epoxy resin (A) can be obtained by epoxidizing 4,4′-bishydroxy 3,3 ′, 5,5 ′,-tetramethylbiphenyl using epichlorohydrin. As the epoxy resin used in the present invention, in addition to the epoxy resin represented by the structural formula (A) above, it may be used in combination with a resin generally used in epoxy resin molding materials for sealing electronic parts. Examples thereof include phenol novolac type epoxy resins, orthocresol novolac type epoxy resins and epoxidized novolac resins of phenols and aldehydes, glycidyl amine type epoxy resins, and alicyclic epoxy resins. Any number of these may be used in combination.

When these epoxy resins are used in combination, the compounding ratio of the epoxy resin (A) of the present invention is preferably 30% by weight or more, more preferably 50% by weight or more, though not particularly limited. .. 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 aldehydes with phenol, cresol, naphthol and the like. There are no particular restrictions on the molecular weight distribution of the phenolic novolak resin of (B),
The weight ratio of the components below the nucleolus is preferably 15% by weight or less,
Furthermore, 10% by weight or less is preferable. The reason for this is
This is because the glass transition temperature and the high temperature strength decrease when the content of the dinuclear or lower component exceeds 15% by weight. Generally, the glass transition temperature of the molding compound for semiconductor encapsulation is required to be 150 ° C. or higher, which is the guaranteed temperature of the IC, which is an important index. Further, high temperature strength is a physical property value relating to reflow crack resistance, and the higher the strength, the higher the crack resistance.

Further, since the epoxy resin (A) has a very low melt viscosity and generally has a great difference in viscosity from the compound (B), it is difficult to obtain a uniform molding material in the kneading device. Therefore, it is preferable that the epoxy resin of (A) and the phenol resin of (B) are heated and mixed in advance, and then a curing accelerator, a filler, and the like are added and kneading is performed.
The heating and mixing conditions are preferably 110 ° C. or higher at which the epoxy resin (A) melts, and 140 or less at which the reaction between the epoxy group and the phenol group is relatively mild, and the heating and mixing time is (A) and (B). The minimum necessary amount that both resins are uniformly compatible is preferable. Epoxy resin used in the present invention and (B)
The equivalent ratio of the phenol resin is preferably 0.8 to 1.3 from the viewpoint of curability, heat resistance and the like.

Further, a curing accelerator which 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,
Tertiary amides such as dimethylaminoethanol and tris (dimethylaminomethyl) phenol, 2-methylimidazole, 2-phenylimidazole, 2-phenyl-
Imidazols such as 4-methylimidazole and 2-heptadecylimidazole, organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine, tetraphenylphosphonium / tetraphenylborane , Tetraphenylphosphonium / ethyltriphenylborate, tetrabutylphosphonium / tetrabutylborate, etc., tetra-substituted phosphonium / tetra-substituted borate, 2-ethyl-4-methylimidazole /
There are tetraphenylboron, tetraphenylboron salts such as N-methylmorpholine / tetraphenylborate, and the like.

In addition, it is necessary to use an inorganic filler as the filler from the viewpoint of reducing hygroscopicity and improving strength. As the inorganic filler, powder of crystalline silica, fused silica, alumina, zircon, calcium silicate, calcium carbonate, silicon carbide, silicon nitride, boron nitride, zirconia, zircon, fosterite, steatite, spinel, mullite, titania, etc. , Or spheres of these, and the like can be used, and one or more types can be used.
For the same reason, the compounding amount of the filling agent is required to be 60% by volume or more, 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,
Coupling agents such as organic titanates and aluminum alcoholates, and flame retardants can be used. As a general method for producing a molding material using the above raw materials, after sufficiently 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 Using the molding material obtained in the present invention,
The low-pressure transfer molding method is the most common method for sealing electronic components, but the injection molding method and the compression molding method are also possible.

[0011]

[Function] IC package cannot be received during reflow
The cause of the phenomenon is that moisture absorbed during storage of the IC rapidly expands during reflow, resulting in cracks and elements of the package, and peeling of the interface between the lead frame and the resin. Therefore, a resin that is resistant to reflow is required to have low water absorption, high strength at high temperatures, and high adhesive strength. The epoxy resin which is the main component of the present invention is a diepoxy resin based on tetramethylbiphenol having excellent skeleton rigidity and hydrophobicity,
It can be inferred that a composition having excellent heat resistance, hygroscopicity, and adhesiveness could be obtained because a phenol resin having a low binuclear content, which has high high-temperature strength, was used as a curing agent. It is considered that this effect improved the reflow crack resistance.

[0012]

EXAMPLES The present invention will be 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] Epoxy resin 80 having an epoxy equivalent of 190
Weight part and hydroxyl group equivalent 106, softening point 95 ° C, dinuclear body 1
50 parts by weight of 1.5% by weight phenol novolac resin 1
A uniform solid resin obtained by melt-mixing under the conditions of 20 ° C. and 30 minutes and cooled, and a bromine ratio of 50% by weight, an epoxy resin 3
20 parts by weight of 75 brominated bisphenol A type epoxy resin, triphenylphosphine (2.5 parts by weight), carnauba wax (3 parts by weight), carbon black (1 part by weight), γ-glycidoxypropyltrimethoxy Silane (4 parts by weight), quartz glass powder (75% by weight) are mixed,
Using a 10-inch diameter heating roll, kneading temperature 80 ~
The epoxy resin molding material of Example 1 was produced under the conditions of 90 ° C. and kneading time of 7 to 10 minutes.

Example 2 The phenol nopolak resin of Example 1 was prepared by adding 10 equivalents of hydroxyl groups.
6, the softening point was 110 ° C., and the preparation was performed in the same manner as in Example 1 except that the phenol novolac resin in which the dinuclear body was 6.2 wt% was replaced.

Example 3 The phenol nopolak resin of Example 1 has the structural formula

[Chemical 4] Hydroxyl group equivalent 140, softening point 115 ° C, m /
It was produced in the same manner as in Example 1 except that 66 parts by weight of a resin containing 2.6% by weight of a component in which n = 2/1 and n + m was 2 or less was replaced.

Comparative Example 1 The phenol novolac resin of Example 1 was prepared by adding 10 equivalents of hydroxyl groups.
6, the softening point was 82 ° C., and the same procedure as in Example 1 was carried out except that the phenol novolac resin having the dinuclear component of 22.0% by weight was replaced.

Comparative Example 2 Comparative Example 2 was prepared in the same manner as Comparative Example 1 except that the biphenyl skeleton diepoxy resin of Comparative Example 1 was replaced with 80 parts by weight of an orthocresol novolac type epoxy resin having an epoxy equivalent of 200 and a softening point of 73 ° C.

The characteristics of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1, and details of the test method are shown in Table 2. Compared with Comparative Example 1, the ratio of the binuclear body was smaller in Example, so that the water absorption rate and the adhesive strength were not changed and the glass transition temperature was increased. Further, it can be seen that the example has a smaller water absorption rate and excellent adhesive strength as compared with the comparative example 2.

[0018]

[Table 1]

In order to clarify the effect of the present invention, the results of crack resistance during reflow using the evaluation IC and moisture resistance after reflow are shown. IC used for crack resistance evaluation
Is a flat package with an outer shape of 19 × 14 × 2.0 mm, and 8 × 10 × 0.4 (mm) elements are mounted on it.
It is a 0 pin, 42 alloy lead. The test condition is 8
After humidifying at 5 ° C. and 85% RH for a predetermined time, 90 papermaking heating is performed in a vapor phase reflow oven at 215 ° C. The evaluation was performed by observing the appearance with a microscope and determining the presence or absence of package cracks. The IC package was molded under the conditions of 180 ° C. for 90 seconds and 70 kfg / cm ² and then post-cured at 180 ° C. for 5 hours after molding.

[0020]

[Table 2] Table 3 shows the result of the crack resistance test during temporary reflow. Table 3
Compared to Comparative Example 1 as shown in Examples 1 to 3,
Good reflowability was exhibited despite the high g. Further, crack resistance during reflow can be significantly improved as compared with a typical conventional resin-based comparative example 2.

[0021]

[Table 3]

[0022]

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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08J 5/00 CFC 9267-4F C08K 3/00 NKT 7167-4J H01L 23/29 23/31 // C08L 63:00

Claims (2)

[Claims] 1. A structural formula of (A) as a main component is And an epoxy resin (B) containing no more than 15% by weight of a phenolic novolac resin and (C) 60% by volume or more of an inorganic filler. Epoxy resin molding compound for stop. 2. The epoxy resin of (A) and the novolak resin of (B) are heated and mixed in advance, and then a curing accelerator, a filler and the like are added and kneading is performed to produce the resin. 1. An epoxy resin molding material for electronic component encapsulation according to 1.