JP2000290352A - Epoxy resin curing agent and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a curing agent used to give a cured epoxy resin being excellent in humidity resistance and adhesion to a metal or an inorganic matter and having low-stress properties by using as an essential component a cocondensate prepared by condensing an ortho-substituted phenol with formaldehyde and condensing the condensate with phenol. SOLUTION: A cocondensate represented by the formula is obtained by condensing 20-80 mol% ortho-substituted phenol such as an ortho-alkyl-substituted phenol such as o-cresol, 2-ethylphenol, or 2-n-butylphenol with formaldehyde and condensing the formed condensate with 80-20 mol% phenol. In the formula, R is a monovalent organic group; a, b, and c satisfy the relationships: a/(a+b+c)=0.2-0.8, and (b+c)/(a+b+c)=0.8-0.2. It is desirable that the cocondensate has a softening point of 60-110 deg.C, a solution viscosity of 20-90 μm2/s, and a weight-average molecular weight of 400-3,000. It is used as an essential component of an epoxy resin curing agent and is used in an amount of, desirably, at least 60 wt.% based on the entire curing agent.

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 agent, and more particularly to an epoxy resin curing agent which provides an epoxy resin cured product having excellent moisture resistance and low stress, and excellent adhesion to various metals and inorganic substances. .

[0002]

2. Description of the Related Art Conventionally, acid anhydrides, amine compounds, imidazole compounds,
Novolak type phenolic resin has been used, but as a curing agent for epoxy resin for semiconductor encapsulants, novolak type epoxy resin is excellent because of its excellent moldability, heat resistance, moisture resistance and electrical properties after curing. Phenolic resins are widely used.

In recent years, chips have become larger due to higher integration of integrated circuits, the mounting method has changed from the insertion method to surface mounting, and packages have become smaller and thinner. That is, since a large chip is exposed to a higher temperature than before in a state in which it is sealed in a thin package, a problem of a package crack occurs, and further reduction in stress and improvement in moisture resistance of the sealing material have been required. The lead frame material of the package is iron
Nickel alloy (42 alloy) and copper alloy are the mainstream,
As the number of pins increases, copper alloys advantageous in lead punching workability, heat dissipation, and cost reduction are increasing. Then, in addition to the above-mentioned properties, a problem that the adhesion to the sealing material is greatly changed by a trace amount of metal additive in the copper alloy has become a problem, and a material having more excellent adhesion has been demanded.

In order to lower the stress and improve the moisture resistance of the sealing material, use of a xylene-modified phenol resin as a curing agent (Japanese Patent Application Laid-Open No. 59-105017) and use of a fluorine-containing novolak (Japanese Patent Application Laid-Open No. 64-74215). No.) was considered.
Also disclosed is a method for producing a polyhydroxy compound for an epoxy resin curing agent by condensing a phenol with a dimethylol derivative of a 4-alkylphenol or a 4-arylphenol (JP-A-62-119220).
No.). As a known method of improving the adhesiveness, the silane coupling agent can improve the adhesion with an inorganic filler, a metal, a nitride film, and a polyimide coating material. There is a disadvantage of doing it. As described above, even if the stress is reduced, the strength is also reduced, and none of them is sufficiently satisfactory as a curing agent for an epoxy resin sealing material.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an epoxy resin curing agent which is excellent in moisture resistance and low stress when cured with an epoxy resin and has excellent adhesion to various metals and inorganic substances. It is in.

[0006]

According to the present invention, there is provided a compound represented by the general formula (1):
An epoxy resin curing agent containing a co-condensate of a phenol and an ortho-substituted phenol represented by the following formula:

Embedded image

The ortho-substituted phenols used in the present invention include ortho-cresol, 2-ethylphenol, 2-propylphenol, 2-isopropylphenol, 2-n-butylphenol, 2-isobutylphenol, and 2-t-butylphenol. , 2-hexylphenol, 2-octylphenol, 2-nonylphenol, 2-phenylphenol, 2-benzylphenol, 2-cumylphenol and the like. When a phenol resin is used as a curing agent for the epoxy resin, in order to reduce the water absorption of the cured epoxy resin, the phenol compound to be used preferably has a hydrophobic alkyl group as a substituent on a benzene ring, and Orthoalkyl-substituted phenols are preferred in order not to reduce the curability with the epoxy resin. Among them, 2-n-alkylphenol having no bulky substituent is particularly preferable. n
-When the alkyl group is a long-chain alkyl group having 6 or more carbon atoms, the water absorption rate is lowered, but the glass transition temperature is lowered and the heat resistance is lowered, which is not preferable.

[0008] The content of phenol and ortho-substituted phenols in the co-condensate of the present invention is such that the phenol content is 80 to 20 mol% and the ortho-substituted phenols content is 2%.
When the phenol content is more than 80 mol%, the hygroscopicity is reduced. When the content of the ortho-substituted phenols is more than 80 mol%, the curability and heat resistance are reduced. .

In the method for producing a co-condensate represented by the general formula (1) of the present invention, first, an ortho-substituted phenol and an aldehyde are reacted in the presence of an acid catalyst, and then phenol is added to obtain a co-condensate. . When the ortho-substituted phenol and phenol are simultaneously charged and reacted from the beginning of the reaction, the highly active phenol reacts first and a block copolymer cannot be obtained, and the content of the ortho-substituted phenol and phenol in the co-condensate is controlled. There is a drawback that you can not. The co-condensate obtained by a method in which phenol is first reacted and then the ortho-substituted phenol is added, the proportion of the charged amount and the content in the co-condensate do not become the same, and the phenol content tends to increase. There is a disadvantage that it is difficult to control the content.

The formaldehyde source used for synthesizing the co-condensate of the present invention is not particularly limited, but formaldehyde or paraformaldehyde is preferred because it is industrially mass-produced and inexpensive. The acid catalyst used for the cocondensate synthesis in the present invention is not particularly limited, formic acid, acetic acid, propionic acid, paratoluenesulfonic acid, organic acids such as oxalic acid, sulfuric acid, inorganic acids such as hydrochloric acid can be used, Particularly, oxalic acid and hydrochloric acid are preferable.

The softening point of the co-condensate in the present invention is 60 to 11
0 ° C is preferable, and particularly preferably 75 to 95 ° C. If the softening point is less than 60 ° C., the composition is liquid or semi-solid at room temperature, and there is a possibility that the workability may deteriorate, the curability of the resin composition may decrease, or the glass transition temperature of the cured product may decrease. 110
If the temperature exceeds ℃, it does not melt sufficiently during the heating and mixing with the epoxy resin, so that uniform mixing cannot be easily performed, so that the curability and moldability are reduced, and there is a possibility that a non-uniform molded product is obtained.

The solution viscosity of the co-condensate in the present invention is 20 to 9
0μm is preferably ² / s, in particular 30 to 60 m ² / s is more preferable. If the solution viscosity is less than 20 μm ² / s, there are many low molecular components not involved in the curing reaction in the resin, and the curability of the resin composition may be reduced, or the glass transition temperature of the cured product may be lowered. If it exceeds 90 μm ² / s,
The melt viscosity is high, the fluidity is reduced, and poor moldability such as poor filling may occur.

The weight average molecular weight of the co-condensate in the present invention is 4
It is preferably from 00 to 3000, more preferably from 600 to 1500. If the weight-average molecular weight is less than 400, the composition is liquid or semi-solid at room temperature, and there is a possibility that workability problems, curability of the resin composition may decrease, or glass transition temperature of the cured product may decrease. If it exceeds 3,000, the melt viscosity is high and the fluidity is reduced, and poor moldability such as poor filling may occur.

The co-condensate of the present invention may be used alone or in combination with one or more other epoxy resin curing agents. Preferably, it is at least 60% by weight, more preferably at least 80% by weight, based on the total curing agent. Examples of other epoxy resin curing agents include phenol / formaldehyde resin, cresol / formaldehyde resin, phenol / dicyclopentadiene resin, phenol / alkylbenzene resin, etc. Can be set appropriately in accordance with.

The characteristic values described above for the co-condensate of the present invention were measured according to the following methods. 1. Hydroxyl equivalent: A sample was acetylated with pyridine and an excess amount of acetic anhydride, and acetic acid generated from acetic anhydride consumed by the sample was determined by titration with an aqueous sodium hydroxide solution. 2. Softening point: determined by a ring and ball method described in JIS K 7234. 3. Solution viscosity: A solution of sample / ethanol = 5/5 was prepared and determined at 25 ° C. by the method described in JISZ8803. 4. Weight average molecular weight: Tosoh GPC column (G100
0HXL: 1, G2000HXL: 2, G3000
HXL: 1), GPC measurement was performed using a differential refractometer as a detector under the analysis conditions of a flow rate of 1.0 ml / min, an elution solvent of tetrahydrofuran, and a column temperature of 40 ° C., and the values were obtained by conversion with standard polystyrene. 5. Ortho substituted phenol / phenol content ratio: ¹ H N
The phenol content and the ortho-substituted phenol content were measured by MR (manufactured by JEOL Ltd., JNM-EX90), and the ratio was determined. The method for measuring these characteristics is the same for the following examples.

[0016]

The present invention will be described below with reference to examples. The present invention is not limited by these examples,
"Parts" and "%" described in Examples and Comparative Examples
Represents "parts by weight" and "% by weight".

Production Example 1 Orthocresol 298 parts, 37% formalin 112
Parts, a mixture of 3 parts of oxalic acid was reacted at 100 ° C. for 2 hours, and then 259 parts of phenol, 112 parts of 37% formalin,
2.6 parts of oxalic acid are added to the reaction system,
Allowed to react for hours. Thereafter, distillation was performed under reduced pressure until the internal temperature reached 170 ° C to remove water, unreacted orthocresol and phenol, and the reaction was continued until the internal temperature reached 250 ° C. Hydroxyl equivalent 112 g / eq, softening point 80
° C, solution viscosity 30 µm ² / s, weight average molecular weight 870,
477 parts of a co-condensate having an ortho-cresol / phenol content ratio of 48/52 were obtained.

Production Examples 2 and 3 A co-condensate resin of the desired phenol and ortho-substituted phenol was obtained in the same manner as in Production Example 1 with the composition shown in Table 1.

[0019]

[Table 1]

Production Example 4 After reacting a mixture of 518 parts of phenol, 237 parts of 37% formalin and 5.2 parts of oxalic acid at 100 ° C. for 2 hours, the mixture was distilled under reduced pressure until the internal temperature reached 170 ° C., and unreacted with water. The phenol was removed, and the reaction was continued until the internal temperature reached 250 ° C. Hydroxyl equivalent 104g / eq, softening point 90
° C, solution viscosity 45 µm ² / s, weight average molecular weight 1400
448 parts of phenol resin was obtained.

Production Example 5 A mixture of 506 parts of orthocresol, 202 parts of 37% formalin and 5.1 parts of oxalic acid was reacted at 100 ° C. for 2 hours.
Distillation was performed under reduced pressure until the internal temperature reached 170 ° C to remove water and unreacted phenol, and the reaction was performed until the internal temperature reached 250 ° C. Hydroxyl equivalent 120g / eq, softening point 67 ° C,
450 parts of an orthocresol resin having a solution viscosity of 20 μm ² / s and a weight average molecular weight of 530 were obtained.

Examples 1 to 5 and Comparative Examples 1 and 2 The co-condensates obtained in Production Examples 1 to 3, the phenolic resin and ortho-cresol resin obtained in Production Examples 5 and 6, and an ortho-cresol novolac epoxy resin ( Nippon Kayaku EOC
N-1020-65), triphenylphosphine, fused silica and stearic acid were roll-kneaded with the composition shown in Table 2 to obtain a molding material. 100 kg / cm ^{2 of} this molding material,
Press molding at 175 ° C for 10 minutes, then 180
It was post-cured at 6 ° C. for 6 hours to obtain a cured molded product. The glass transition temperature, flexural strength, flexural modulus and water absorption of this molded product were measured, and the results are shown in Table 2.

[0023]

[Table 2]

(Measurement method) 1. Glass transition temperature: measured using a thermomechanical analyzer (TMA) 2. Flexural strength and flexural modulus: JIS K 6911 Water absorption: The size of the test piece is 50 mm in diameter and 3 m in thickness
3. Measure the water absorption (% by weight) by a weight change before and after the treatment at 120 ° C., 100% RH and 80 hours with a circular plate of m. Adhesive strength to metal: press-molded at 75 kg / cm ² at 175 ° C. for 2 minutes using a low-pressure transfer molding machine, and as shown in FIG. 1, a pudding-shaped molded product was formed on coupon 1 of copper alloy MF202. 2 is integrally molded, and 1
Post cure was performed at 80 ° C. for 6 hours. Next, as shown in FIG. 2, the shear strength of the copper coupon and the molded product before and after the moisture absorption treatment was measured by a measuring jig 3 using Tensilon 4 (manufactured by Orientec) (moisture absorption condition: 85 ° C./85% R).
H / 24 hours). Based on the shear strength, the contact area between the coupon and the molded article was considered to be a perfect circle, the diameter was measured and the contact area was calculated, and the adhesive strength per unit area was calculated. 5. Adhesion strength with silicon chip: In the same manner as in the above 4, as shown in FIG. 3, a pudding-shaped molded product 2 is integrally formed on a simulated silicon chip 5 having a surface coated with silicon nitride. Was bonded using a commercially available adhesive to the copper coupon 1 used in, and further post-cured at 180 ° C. for 6 hours. Next, as shown in FIG. 4, tensilon 4 (Toyo Baldwin Co., Ltd.)
Manufactured by Tensilon UTM-III-500) was used to measure the shear strength of the simulated silicon chip coated with silicon nitride and the molded product before and after the moisture absorption treatment (hygroscopic conditions: 85 ° C./85% RH).
/ 24 hours). Hereinafter, the adhesive strength per unit area was calculated in the same manner as in 4 above.

[0025]

As is clear from Table 2, the epoxy resin cured molded product using the epoxy resin curing agent of the present invention is:
It can be seen that the water absorption rate is low, the bending strength is improved, and the bending elastic modulus is low, and the material has low stress and excellent moisture resistance. Further, since the adhesive strength with copper alloy or silicon nitride is good even after moisture absorption, the epoxy resin curing agent of the present invention is used for epoxy resin encapsulating material for high-performance electronic parts, epoxy resin powder coating, and epoxy resin. It is suitable for resin laminates and the like, and is expected to contribute to the improvement of the performance of electronic components.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an integrally molded product of a copper coupon and a pudding shape used for measuring adhesive strength to metal, (a) is a perspective view,
(B) is a side view.

FIG. 2 is a side view showing a method for evaluating adhesive strength.

FIG. 3 (a) is a perspective view of a simulated silicon chip and a pudding-shaped integrally molded product used for measuring the bonding strength with the silicon chip, and FIG. 3 (b) is a diagram illustrating the integrated molded product adhered to a copper coupon. It is a side view of a thing.

FIG. 4 is a side view illustrating a method for evaluating adhesive strength.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Copper alloy coupon 2 Mold 3 Measurement jig 4 Tensilon 5 Simulated silicon chip R Diameter of contact area between copper coupon and molded article r Diameter of contact area between simulated silicon chip and molded article

Claims (4)

[Claims] 1. An epoxy resin curing agent comprising, as an essential component, a cocondensate of a phenol represented by the general formula (1) and an ortho-substituted phenol. Embedded image 2. The epoxy resin curing agent according to claim 1, wherein the ortho-substituted phenol is an orthoalkyl-substituted phenol. 3. The epoxy resin curing agent according to claim 1, wherein the ortho-substituted phenol is orthocresol. 4. The method for producing a co-condensate according to claim 1, wherein the phenol is co-condensed after condensing the ortho-substituted phenol with formaldehyde.