JP2000265119A - Die attach paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject paste maintaining conventional die attach paste characteristics, curable even in an extremely short time, useful for bonding a semiconductor by making the paste include a specific isocyanuric acid EO modified diacrylate, etc. SOLUTION: This paste comprises (A) an isocyanuric acid EO modified diacrylate or triacrylate of formula I (A is CH2=CHCO or H), (B) a monoacrylate and/or a monomethacrylate of formula II (R1 is CH3 or H; R2 is an alicyclic and/or aromatic >=10C substituent group), (C) an organic peroxide (e.g. cumylperoxy neodecanoate and/or an azo compound (e.g. 2,2'- azobisisobutylnitrile, etc.), (D) an inorganic filler (e.g. silver powder, etc.). The weight ratio of the component A to the component B is preferably 80/20 to 20/80.

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 In recent years, the production volume of semiconductor packages has been on an increasing trend, and accordingly, reduction of manufacturing costs has become an important issue. In the process of assembling a semiconductor package, there is a step of bonding a semiconductor and a lead frame with a die attach paste, and in this step, time reduction and low-temperature curing are key points. The curing process is roughly classified into a batch-type oven method and an in-line curing method, and a normal die mount using a fast-curing paste used in-line is usually 3 to 150 ° C. to 200 ° C.
This is performed between 0 and 60 seconds. However, development of a paste that can be cured at a lower temperature for a shorter time is desired in the future.

[0003] On the other hand, the reliability of the package is particularly important in terms of solder crack resistance, but the die attach paste is also required to have low stress in order to reduce the difference in linear expansion between the silicon chip and the lead frame. It is. Epoxy resin, cyanate resin, bismaleimide resin, and the like are known as the base resin of the die attach paste. For example, the resin can be cured within 30 seconds and has properties (adhesiveness, low stress property) suitable for each application. ) Were not 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.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been completed as a result of intensive studies to find a die attach paste which can maintain the characteristics of a conventional die attach paste and can be cured even in a very short time. It is.

[0005]

The present invention provides (A) an isocyanuric acid EO-modified diacrylate or triacrylate represented by the general formula (1), and (B) a monoacrylate or monomethacrylate represented by the general formula (2). , (C) an organic peroxide and / or an azo compound, and (D) an inorganic filler as a die attach paste.

[0006]

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In a more preferred embodiment, (A) isocyanuric acid EO-modified diacrylate or triacrylate represented by the general formula (1) and (B) monoacrylate and / or monomethacrylate represented by the general formula (2) Is a die attach paste having a weight ratio of 80/20 to 20/80.

The acrylate resin used in the present invention has a weight ratio of the isocyanuric acid EO-modified diacrylate or triacrylate represented by the general formula (1) and the monoacrylate and / or monomethacrylate represented by the general formula (2) of 80/80. It is preferably 20 to 20/80. 80
If it is higher than / 20, the paste viscosity is too high, and the coating workability is significantly deteriorated. On the other hand, if the ratio is smaller than 20/80, the adhesiveness,
Heat resistance deteriorates.

Since the acrylate resin represented by the general formula (1) has a high viscosity, a mono (meth) acrylate containing one (meth) acryl group is added as a reactive diluent. Further, the mono (meth) acrylate used in the present invention is represented by the formula (2), and further, the substituent R ₂ is alicyclic, and / or
Alternatively, it is important that the substituent R ₂ contains an aromatic group and the total number of carbon atoms in the substituent R ₂ is 10 or more. By satisfying this condition, not only the effect as a diluent, but also shrinkage during curing can be suppressed due to the presence of a bulky substituent, and the adhesion reliability at the interface can be enhanced. In the case of a substituent having 10 or more carbon atoms which does not contain an alicyclic or aromatic group, curing shrinkage can be reduced, but the adhesiveness is undesirably reduced due to the characteristics of the aliphatic hydrocarbon.

Examples of mono (meth) acrylates include:

Embedded image And the like, and one or more of these can be used in combination.

In the present invention, other acrylate resins may be mixed and used. Other acrylate resins when mixed with the acrylate resin include, for example, urethane acrylates and polyester acrylates obtained by the reaction of hydroxyalkylacrylic acid, polyalkylene glycol and diisocyanate.

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 addition amount of these organic peroxides and azo compounds is 0.1% based on the total weight of component (A) + component (B).
Preferably it is between 5% and 5% by weight. If the amount is more than 5% by weight, the life of the paste (viscosity change with time) is large, which causes 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 powder is used for imparting conductivity,
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 viscosity of the paste required, but the average particle size is usually 2 to 10 μm.
m, the maximum particle size is preferably about 50 μm. Also,
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.

In the resin paste of the present invention, additives such as an antifoaming agent, a coupling agent and a surfactant can be used if necessary. Of these additives, the coupling agent is preferably added to enhance the adhesiveness.

Examples thereof include, but are not particularly limited to, so-called alkoxysilane compounds containing an epoxy group, an amino group, a mercapto group, a vinyl group, etc., and acrylates or methacrylates having a phosphate group. In the method for producing the paste of the present invention, for example, the paste is premixed to obtain a paste using a three-roll mill or the like, and defoamed under vacuum.

[0021]

The present invention will be specifically described below with reference to examples. <Examples 1 to 8> Isocyanuric acid EO-modified diacrylate represented by the general formula (1) (manufactured by Toagosei Co., Ltd., M-21)
5), a monoacrylate represented by the following structural formula, the following organic peroxides 1 and 2 and an azo compound as a polymerization initiator, a phosphoric acid group-containing methacrylate as a coupling agent, and an average particle size of 3 μm as an inorganic filler, A flake silver powder having a 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 is blended as shown in Table 1,
The mixture was kneaded using three rolls, and a paste was obtained after defoaming. 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: Using a paste, a 2 × 2 mm silicon chip was mounted on a copper frame and cured in an oven at 180 ° C. for 15 minutes. After curing, the die shear strength under heat at 250 ° C. was measured using a push-pull gauge. Void: A glass chip of 10 mm × 10 mm was mounted on a lead frame, and after curing, voids were visually checked for appearance. A void of 15% or less of the adhered area was regarded as good, and a void exceeding 15% was regarded as defective. -Peeling during WB processing: 6 mm x 15 m on lead frame
After mounting the m-type chip and curing, a wire bonding treatment was performed at 250 ° C., and the adhesion state of the pellet was observed. If there was no peeling, it was good, and if peeling was observed, it was bad. -Warpage: Warpage was measured as an evaluation of low stress. Thickness 2
6mm x 15mm x 0.3 in a 00 micron copper frame
mm silicon chip at 175 ° C 15
The paste was adhered so that the thickness of the paste became 20 μm in seconds, 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 height difference. -Package crack resistance: Sumicon EME-7320
A package molded under the following conditions using a sealing material (manufactured by Sumitomo Bakelite Co., Ltd.) at 85 ° C. and a relative humidity of 85
% After a water absorption treatment for 168 hours, followed by IR reflow (240
(10 ° C., 10 seconds), the number of internal cracks was measured by cross-sectional observation, and 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 6> 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]

[0025]

[Table 2]

[0026]

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[0027]

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Organic peroxide 1: Cumyl peroxyneodecanate, manufactured by NOF Corporation (decomposition temperature in a rapid heating test: 65 ° C.) Organic peroxide 2: manufactured by NOF Corporation, t -Butyl peroxyisopropyl monocarbonate (decomposition temperature in rapid heating test: 108 ° C) Azo compound: 2,2'-azoisobutylnitrile, manufactured by Wako Pure Chemical Industries, Ltd.

[0029]

According to the die attach paste of the present invention, adhesion is improved by an isocyanuric EO-modified diacrylate or triacrylate having a limited structure, and shrinkage during curing is reduced by a combination of a monoacrylate having a bulky substituent. This is a fast-curing paste that has excellent low stress and adhesiveness as a result.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J011 PA02 PA03 PA07 PA08 PA13 PA34 PA39 PA43 PA69 PA86 PA99 PB06 PB22 PB23 PB27 PB28 PB30 PB40 4J027 AA04 AC03 BA07 BA13 BA29 CA12 CA18 CA20 CA24 CA36 CB01 CB09 CD06 FA122FA FA161 FA162 HB41 HC14 KA11 KA24 KA32 KA42 LA06 LA07 LA08 MA02 MA10 NA20 PA24 4J100 AL08Q AL65P AL66P BA06Q BA07Q BA11P BC08Q BC43Q BC44Q BC73P CA04 CA31 HA53 HC36 HC54 JA46 5F047 BA33 BB11

Claims (2)

[Claims] (A) isocyanuric acid EO-modified diacrylate or triacrylate represented by the general formula (1):
(B) a monoacrylate represented by the general formula (2) and / or
Alternatively, a die attach paste comprising monomethacrylate, (C) an organic peroxide and / or an azo compound, and (D) an inorganic filler. Embedded image Embedded image 2. A weight ratio of the (A) isocyanuric acid EO-modified diacrylate or triacrylate represented by the general formula (1) to the (B) monoacrylate and / or monomethacrylate represented by the general formula (2). Is 80/20 to 20/80.