JP2001257219A - Die attach paste and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide die attach paste which can be cured in a very short time while the paste maintains the characteristics of the conventional die attach paste. SOLUTION: This die attach paste is composed of (A) urethane di-(meta-) acrylate obtained by causing a reaction among hydroxyalkyl (meta-)acrylic acid, polyalkylene glycol, and di-isocyanate; (B) a reactive diluent having a (meta-)acrylic group; (C) a silane coupling agent containing sulfur atoms; (D) an organic peroxide and/or an azo compound; and (E) an inorganic filler. The mixing ratio of the component (D) is adjusted to 0.1-5 wt.% of the total weight of the components (A) and (B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor bonding paste which is excellent in adhesiveness, rapid curing property and reliability.

[0002]

2. Description of the Related Art With the recent spread of computers, the production volume of semiconductor packages has been increasing year by year, and accordingly, reduction of manufacturing costs has become an important issue. In the process of assembling a semiconductor package, there is a process of bonding a semiconductor and a lead frame with a die attach paste. In this process, time reduction and low-temperature curing are key points.
The method of curing the die attach paste is roughly classified into a batch oven method and an in-line curing method. A normal die mount using a quick-curing paste used in the in-line is on a hot plate at 200 ° C. or higher. For more than 60 seconds. However, development of a paste that can be cured at a lower temperature for a shorter time is desired.

On the other hand, the reliability of the package is particularly important in terms of solder crack resistance. However, even if the package is exposed to a high temperature during solder bonding, it is necessary to prevent the package from cracking due to peeling of the die attach paste layer. In particular, the die attach paste is required to have low stress and adhesiveness after moisture absorption.

As the base resin of the die attach paste, epoxy resin, cyanate resin, bismaleimide resin and the like are known. For example, the resin can be cured within 60 seconds and has properties (adhesion, No material that satisfies low stress properties) has been found at all.
Further, even if the properties are satisfied, the viscosity at room temperature increases too much, and there are only materials that are not suitable for use.

[0005]

SUMMARY OF THE INVENTION The present invention provides a die attach paste which maintains the characteristics of a conventional die attach paste and can be cured in a very short time.

[0006]

SUMMARY OF THE INVENTION The present invention relates to (A) urethane di (meth) acrylate and (B) (meth) acryl groups obtained by reacting hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate. A reactive diluent, (C) a silane coupling agent containing a sulfur atom, (D) an organic peroxide and / or an azo compound, and (E) an inorganic filler. The die attach paste is 0.1 to 5% by weight based on the total weight of (A) and component (B).

In a more preferred embodiment, (A) a urethane di (meth) acrylate obtained by reacting hydroxyalkylacrylic acid, polyalkylene glycol and diisocyanate with (B) a reactive diluent having a (meth) acrylic group Weight ratio of 80/20 to 20 /
80 is the die attach paste. Further, it is a semiconductor device manufactured using the above-mentioned die attach paste.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The acrylate resin used in the present invention is composed of urethane di (meth) acrylate obtained by reacting hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate with (meth) acrylate.
80/20 weight ratio of reactive diluent having acrylic group
It is preferable that it is 20/80. If the ratio of urethane di (meth) acrylate obtained by reacting hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate is higher than 80/20, the paste viscosity is too high, and the coating workability is significantly deteriorated. on the other hand,
If it is less than 20/80, the adhesiveness and heat resistance will be poor.

The urethane di (meth) acrylate used in the present invention is synthesized by a conventional method by reacting hydroxyalkylacrylic acid or methacrylic acid, polyalkylene glycol, and diisocyanate. Examples of hydroxyalkyl acrylic acid or methacrylic acid include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
-Hydroxypropyl methacrylate and the like. Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polybutylene glycol and the like. Examples of diisocyanates include hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate and hydrogenated products thereof.

Examples of reactive diluents having (meth) acrylic groups which are mixed with urethane di (meth) acrylate include:

Embedded image (Meth) acrylates and polyfunctional (meth) acrylates such as dimethyloltricyclodecanedi (meth) acrylate
Acrylates can be used, and one or more of these can be used in combination.

When the silane coupling agent containing a sulfur atom of the component (C) used in the present invention is mixed with a resin, the adhesiveness to a metal can be remarkably improved.
The amount added is based on the total weight of component (A) and component (B).
It is preferable that 0.001 ≦ (C) / ((A) + (B)) ≦ 0.1. If it is less than 0.001, the effect of improving the adhesiveness is poor, and if it is more than 0.1, the curing speed is undesirably reduced. Examples include bis (3-triethoxysilylpropyl) tetrasulfane, γ-mercaptopropyltrimethoxysilane, and the like.

Next, examples of the polymerization initiator include organic peroxides and azo compounds. The decomposition temperature of the organic peroxide in a rapid heating test (decomposition start temperature when 1 g of a sample is placed on an electric heating plate and heated at a rate of 4 ° C./min) is preferably from 40 ° C. to 140 ° C. When the decomposition temperature is lower than 40 ° C., the storage stability at room temperature becomes poor,
When the temperature exceeds ℃, the curing time becomes extremely long.

Examples of the organic peroxide used in the present invention include cumylperoxyneodecanate, t-butylperoxyneodecanate, 1-cyclohexyl-1-
Methyl ethyl peroxy neodecaneate, 1,1,3
3-tetramethyl peroxyneodecane, 1,1,
3,3-tetramethylbutylperoxy-2-ethylhexanate, bis (4-butylcyclohexyl) peroxydicarbonate, t-butylperoxyisopropyl monocarbonate, 1,1-bis (t-butylperoxy)- 3,3,5-trimethylcyclohexane, t-
Butyl peroxybenzoate, t-butyl peroxy 3,5,5-trimethyl hexanate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-hexyl peroxy-2-ethyl hexanate and the like.
Examples of the azo compound include 2,2′-azobisisobutylnitrile and 1,1′-azobis (1-acetoxy-1
-Phenylethane).

These organic peroxides and azo compounds can be used alone or in combination of two or more to control curability. Further, various polymerization inhibitors can be added in advance in order to improve the storage stability of the resin.

The amount of these organic peroxides and azo compounds to be added is from 0.1% by weight to 5% by weight based on the total weight of the components (A), (B) and (C). preferable. If the content is more than 5% by weight, the viscosity of the paste changes with time, causing a problem in workability. If the amount is less than 0.1% by weight, the curability is remarkably reduced, which is not preferable.

Examples of the inorganic filler used in the present invention include conductive fillers such as silver powder, gold powder, nickel powder, and copper powder, and insulating fillers such as aluminum nitride, calcium carbonate, silica, and alumina.

Silver is preferred as the filler for imparting conductivity, and the content of ionic impurities such as halogen ions and alkali metal ions is preferably 10 ppm or less. In addition, as the shape of the silver powder, a flake shape, a tree shape, a spherical shape, or the like is used. The particle size of the silver powder to be used varies depending on the required viscosity of the paste, but usually the average particle size is preferably 2 to 10 μm and the maximum particle size is preferably about 50 μm. In addition, a mixture of relatively coarse silver powder and fine silver powder can be used, and various shapes may be conveniently mixed.

Next, the silica filler as one of the insulating fillers preferably has an average particle size of 1 to 20 μm and a maximum particle size of 50 μm or less. If the average particle size is less than 1 μm, the viscosity increases, and if the average particle size exceeds 20 μm, bleeding occurs because the resin component flows out during coating or curing, which is not preferable.
On the other hand, if the maximum particle size exceeds 50 μm, it is not preferable because needle clogging occurs when applying the paste with a dispenser. Furthermore, a relatively coarse silica filler and a fine silica filler may be mixed and used, and various shapes may be conveniently mixed.

The die attach paste in the present invention comprises:
If necessary, additives such as a coupling agent, an antifoaming agent, a surfactant, and an elastomer can be used.

As a method for producing the die attach paste of the present invention, for example, the paste is prepared by premixing, using a three roll or the like to obtain a paste, and then defoaming under vacuum. A semiconductor device manufactured using the die attach paste of the present invention is a semiconductor device having high reliability and high productivity. As a method for manufacturing a semiconductor device, a conventionally known method can be used.

[0021]

The present invention will be specifically described below with reference to examples. <Examples 1 to 8> Urethane diacrylate obtained by reacting hydroxyalkylacrylic acid, polyalkylene glycol and diisocyanate (Toagosei Co., Ltd.)
M-1600), a monoacrylate or diacrylate represented by the following structural formula, a silane coupling agent containing a sulfur atom (manufactured by Nippon Unicar Co., Ltd., A-128
9), the following organic peroxides and azo compounds as polymerization initiators, and flake silver powder having an average particle diameter of 3 μm and a maximum particle diameter of 20 μm, or a silica filler having an average particle diameter of 5 μm and a maximum particle diameter of 20 μm as an inorganic filler. The mixture was blended as in Example 1, kneaded using three rolls, and defoamed to obtain a diach paste. The obtained paste was evaluated by the following method.

<Evaluation method> Viscosity: 2.5 rpm using an E-type viscometer at 25 ° C.
The viscosity in m was measured. -Storage property: The viscosity after standing for 72 hours in a thermostat at 25 ° C was measured. If the increase in viscosity was 10% or less of the initial viscosity, it was good, and if it exceeded 10%, it was bad.・ Adhesive strength: 6 × 6m using die attach paste
m silicon chips were mounted on a copper frame and cured under predetermined curing conditions. 85 ° C / 85% after and after curing
After treatment for RH / 72 hours, an automatic shear strength measuring device (DA
The hot die shear strength at 250 ° C. was measured using PC2400 manufactured by GE Corporation.・ Void: A glass chip of 10 mm × 10 mm is mounted on a lead frame using a die attach paste,
After curing under predetermined curing conditions, the appearance was visually checked for voids. Good if the void is 15% or less of the adhered area, 1
Those exceeding 5% were regarded as defective.

Peeling at the time of wire bonding: A chip of 6 mm × 15 mm is mounted on a lead frame using a die attach paste, cured under predetermined curing conditions, and then subjected to wire bonding at 250 ° C.
The adhesion state of the pellet was observed. Good if there is no peeling,
If peeling was observed, it was determined to be defective. -Warpage: Warpage was measured as an evaluation of low stress. Thickness 2
6mm x 15mm x 0.3mm in a 00μm copper frame
Was bonded using a die attach paste so that the paste thickness became 20 μm, the displacement of the chip in the longitudinal direction was measured using a surface roughness meter, and the amount of warpage was measured based on the difference in height.

Package crack resistance: Sumicon EM
Using a sealing material of E-7320 (manufactured by Sumitomo Bakelite Co., Ltd.), a package molded under the following conditions at 85 ° C./6
After water absorption treatment at 0% RH / 168 hours, the sample was subjected to IR reflow (240 ° C., 10 seconds), the number of internal cracks was measured by cross-sectional observation, and this was used as an index of package crack resistance. Package: 80pQFP (14 × 20 × 2mm thickness) Chip size: 7.5 × 7.5mm (aluminum wiring only) Lead frame: Cu Molding: 175 ° C, 2 minutes Post-mold cure: 175 ° C, 4 hours Total number of packages : 12

<Comparative Examples 1 to 5> Each component having the composition shown in Table 2 was blended, a paste was obtained in the same manner as in Example 1, and the same evaluation was performed.

The evaluation results are shown in Tables 1 and 2.

[Table 1]

[0027]

[Table 2]

[0028]

Embedded image

Organic peroxide: Cumyl peroxyneodecanate (decomposition temperature in a rapid heating test: 65 ° C.) manufactured by NOF Corporation Azo compound: manufactured by Wako Pure Chemical Industries, Ltd.
2,2'-azoisobutylnitrile

[0030]

The die attach paste of the present invention is excellent in low stress property by combining urethane di (meth) acrylate having a flexible structure and a reactive diluent having a (meth) acrylic group, and further comprises a silane containing a sulfur atom. By adding a coupling agent, the adhesion to metal is improved, and as a result, the paste is a fast-curing paste having excellent solder crack resistance.

Claims (4)

[Claims] 1. (A) urethane di (meth) acrylate obtained by reacting hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate, (B) a reactive diluent having a (meth) acryl group,
It comprises (C) a silane coupling agent containing a sulfur atom, (D) an organic peroxide and / or an azo compound, and (E) an inorganic filler, and the addition ratio of the (D) component is as follows. A die attach paste, which is 0.1 to 5% by weight based on the total weight of B). 2. A urethane di (meth) acrylate obtained by reacting (A) hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate, and (B) a reactive diluent having a (meth) acryl group. The die attach paste according to claim 1, wherein the weight ratio of the die attach paste is from 80/20 to 20/80. 3. The addition amount of the (C) silane coupling agent containing a sulfur atom is 0.001 ≦ (C) / ((A) + based on the total weight of the components (A) and (B). (B)) ≦
3. The die attach paste according to claim 1, wherein the value is 0.1. 4. A semiconductor device manufactured using the die attach paste according to claim 1.