JP3473944B2 - Die attach paste and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die attach paste which can be cured while maintaining the characteristics of a conventional die attach paste in a very short time. SOLUTION: A die attach paste consists of (A) a urethandi(metha)acrylate obtainable by reacting a hudroxyalkyl(metha) acrylic acid with a polyalkylene glycol and a diisocyanate, (B) a reactive diluent having a (metha)acrylic group, (C) a diallyl monoglycidyl isocyanurie acid, (D) a phosphoric acid group- containing(metha) acrylate which is shown by general formula (1), (E) an alkoxy silane having an epoxy group, (F) an organic peroxide and/or an azo compound and (G) a die attach paste consisting of an inorganic filler.

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, fast curing property and reliability.

[0002]

2. Description of the Related Art With the recent widespread use of computers, the amount of semiconductor packages produced has been increasing year by year, and as a result, reduction of manufacturing costs has become an important issue. In the semiconductor package assembly, there is a step of adhering the semiconductor and the lead frame with a die attach paste, and the key points are the time reduction and low temperature curing in this step. The method of curing the die attach paste is roughly classified into a batch type oven method and a method of in-line curing. However, a normal die mount using a quick-curing paste used in-line is 30 ° C. at 150 ° C. to 200 ° C.
It is performed in the range from 60 seconds to 60 seconds. However, in the future, it is desired to develop a paste that can be cured at a lower temperature for a shorter time.

On the other hand, regarding the reliability of the package, solder crack resistance is particularly important, but in order to prevent cracking of the package caused by peeling of the die attach paste layer even when exposed to high temperature during solder bonding. In particular, the die attach paste is required to have low stress and adhesiveness after moisture absorption treatment.

Epoxy resin, cyanate resin, bismaleimide resin, etc. are known as the base resin of the die attach paste, but they can be cured within, for example, 30 seconds, and have characteristics (adhesiveness, adhesiveness, No material satisfying the requirements for low stress, etc.) has been found.
Further, even if the properties were satisfied, the viscosity at room temperature increased too much, and only materials suitable for use were available.

[0005]

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

[0006]

The present invention provides a urethane di (meth) acrylate obtained by reacting (A) hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate, and (B) (meth) acrylic group. Reactive diluent having, (C) diallyl monoglycidyl isocyanuric acid, (D) phosphoric acid group-containing (meth) acrylate represented by the general formula (1), (E) epoxy group-containing alkoxysilane, (F) organic peroxide It is a die attach paste comprising an oxide and / or an azo compound and (G) an inorganic filler.

[Chemical 2]

As a further preferred embodiment, the urethane di (meth) acrylate obtained by reacting the (A) hydroxyalkyl acrylic acid, polyalkylene glycol and diisocyanate with the (B) (meth) acryl group-containing reactive diluent 80/20 to 20 /
80 is a die attach paste. In addition, it is a semiconductor device manufactured using a die attach paste.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The acrylate resin used in the present invention is a urethane di (meth) acrylate obtained by reacting hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate with a reactive diluent having a (meth) acrylic group. The weight ratio of the agent is from 80/20
It is preferably 20/80. If the proportion of urethane di (meth) acrylate obtained by reacting hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate is higher than 80/20, the paste viscosity becomes too high and the coating workability becomes significantly poor. on the other hand,
If it is less than 20/80, the adhesiveness and heat resistance will deteriorate.

The urethane di (meth) acrylate used in the present invention is synthesized by a reaction of hydroxyalkyl acrylic acid or methacrylic acid, polyalkylene glycol and diisocyanate by a conventional method. Examples of hydroxyalkyl acrylic acid or methacrylic acid include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2
-Hydroxypropyl methacrylate and the like. Examples of polyalkylene glycols 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:

[Chemical 3] (Meth) acrylates such as methacrylic acid and polyfunctional (meth) acrylates such as dimethyloltricyclodecanedi (meth) acrylate
Acrylate can be used, and it can be used in combination with one or more of these.

The addition amount of (C) diallyl monoglycidyl isocyanuric acid is preferably 0.01≤C / (A + B) ≤0.5 based on the total weight of the components (A) and (B). If it is less than 0.01, no effect is exerted on the adhesiveness after the moisture absorption treatment, and if it is more than 0.5, the paste viscosity is too high and the coating workability is significantly deteriorated.

Examples of the component (D) represented by the general formula (1) include mono (2-methacryloyloxyethyl).
There are acid phosphate, di (2-methacryloyloxyethyl) acid phosphate, mono (2-acryloyloxyethyl) acid phosphate, di (2-acryloyloxyethyl) acid phosphate, and the like. Examples of the component (E) include 3- Glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, etc.
There is.

Next, the total addition amount of the component (D) and the component (E) is 0.001≤ (D + E) / (with respect to the total weight of the component (A), the component (B) and the component (C). A + B + C) ≦ 0.
It is preferably 1. If it is less than 0.001, it has no effect on the adhesiveness, and if it is more than 0.1, the adhesiveness is lowered due to voids during curing.

In the present invention, the component (D) and the component (E) are essential components, and the present invention cannot be embodied even if one of them is missing. The composition ratio is preferably 0.1 ≦ D / E ≦ 10. If it is less than 0.1, the concentration of phosphate groups will be low, and the effect on the lead frame interface will be reduced. Also,
If it exceeds 10, the concentration of phosphoric acid groups increases and acts on the adhesive interface more than necessary, resulting in a decrease in adhesiveness.

Next, examples of the polymerization initiator include organic peroxides and azo compounds. The decomposition temperature of the organic peroxide in the rapid heating test (decomposition start temperature when 1 g of the material is placed on an electric heating plate and heated at 4 ° C./minute) is preferably 40 ° C. to 140 ° C. If the decomposition temperature is less than 40 ° C, the storage stability at room temperature becomes poor, and
This is because if the temperature exceeds ° C, the curing time becomes extremely long.

Examples of the organic peroxides used in the present invention include cumyl peroxyneodecanate, t-butylperoxyneodecanate and 1-cyclohexyl-1-.
Methyl ethyl peroxyneodecanate, 1,1,3
3-tetramethylperoxyneodecanate, 1,1,
3,3-Tetramethylbutylperoxy-2-ethylhexanate, bis (4-butylcyclohexyl) peroxydicarbonate, t-butylperoxyisopropyl monocarbonate, 1,1-bis (t-butylperoxy)- 3,3,5-trimethylcyclohexane, t-
There are butyl peroxy benzoate, 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) and the like.

These organic peroxides and azo compounds may be used alone or in admixture of two or more in order to control the curability. Furthermore, it is possible to add various polymerization inhibitors in advance in order to improve the storage stability of the resin.

The amount of the organic peroxide or azo compound added is 0.1 to 5% by weight based on the total weight of the component (A) + component (B) + component (C). preferable. If it is more than 5% by weight, the viscosity of the paste changes with time and the workability becomes a problem. If it is less than 0.1% by weight, the curability is significantly lowered, 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 preferable as the filler that imparts conductivity, and the content of ionic impurities such as halogen ions and alkali metal ions is preferably 10 ppm or less. The silver powder may have a flake shape, a dendritic shape, a spherical shape, or the like. Although the particle size of the silver powder to be used varies depending on the viscosity of the paste required, it is usually preferable that the average particle size is 2 to 10 μm and the maximum particle size is about 50 μm. Further, a relatively coarse silver powder and a fine silver powder can be mixed and used, and various shapes may be conveniently mixed.

Next, the silica filler, which is 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 becomes high, and if it exceeds 20 μm, the resin component flows out during coating or curing, which causes bleeding, which is not preferable.
If the maximum particle size exceeds 50 μm, needle clogging occurs when the paste is applied with a dispenser, which is not preferable. Further, 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 of the present invention is
If necessary, an additive such as a defoaming agent, a surfactant or an elastomer can be used.

As a method for producing the die attach paste of the present invention, for example, pre-mixing is performed to obtain a paste by using a triple roll or the like, followed by defoaming under vacuum to produce. 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.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples. <Examples 1 to 8> Urethane diacrylate obtained by reacting droxyalkyl acrylic acid, polyalkylene glycol and diisocyanate (Toagosei Co., Ltd.
Manufactured by M-1600), monoacrylate or diacrylate represented by the following structural formula, diallyl monoglycidyl isocyanuric acid (manufactured by Shikoku Chemicals Co., Ltd., MA-DG).
IC), phosphate group-containing methacrylate (Nippon Kayaku Co., Ltd., PM-21) as a coupling agent, and alicyclic epoxyalkoxysilane (Shin-Etsu Chemical Co., Ltd., K)
BM303), the following organic peroxides 1 and 2 as a polymerization initiator, and an azo compound, and further an inorganic filler having a flake-like silver powder having an average particle size of 3 μm and a maximum particle size of 20 μm, or silica having an average particle size of 5 μm and a maximum particle size of 20 μm. The filler was blended as shown in Table 1 and kneaded using a three-roll mill to obtain a paste after defoaming. The obtained paste was evaluated by the following methods.

[Chemical 4]

<Evaluation Method> Viscosity: Rotation speed 2.5 rp at 25 ° C. using E-type viscometer
The viscosity at m was measured. -Preservability: The viscosity was measured after standing still for 72 hours in a constant temperature bath at 25 ° C. If the increase in viscosity was 10% or less of the initial viscosity, it was judged as good, and if it exceeded 10%, it was judged as poor. -Adhesive strength: 6 x 6 m using die attach paste
m silicon chips were mounted on a copper frame and cured under prescribed curing conditions. After curing and 85 ° C / 85 after curing
% RH / 72 hours after treatment, automatic shear strength measuring device (D
The die shear strength at the time of heating at 250 ° C. was measured using PC2400 manufactured by AGE. -Void: Mount a 10 mm x 10 mm glass chip on the lead frame using die attach paste,
After curing under predetermined curing conditions, the appearance was checked visually for voids. Good if the void is 15% or less of the adhered area, 1
Those exceeding 5% were regarded as defective.

Peeling during wire bonding treatment: A 6 mm × 15 mm chip is mounted on a lead frame using a die attach paste, and after curing under predetermined curing conditions, wire bonding treatment is performed at 250 ° C.
The adhered state of the pellet was observed. Good if there is no peeling,
If peeling was observed, it was regarded as defective. Warpage: Warpage was measured as an evaluation of low stress. Thickness 2
6mm x 15mm x 0.3mm on a 00μm copper frame
The silicon chip of No. 2 was bonded using a die attach paste to a paste thickness of 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 by the height difference.

・ Package crack resistance: SUMICON EM
Using a sealing material of E-7320 (Sumitomo Bakelite Co., Ltd.), a package molded under the following conditions was 85 ° C / 6.
After water absorption treatment for 0% RH / 168 hours, it was subjected to IR reflow (240 ° C., 10 seconds) and the number of internal cracks was measured by observing a cross section, which was used as an index of package crack resistance. Package: 80 pQFP (14 x 20 x 2 mm thickness) Chip size: 7.5 x 7.5 mm (only aluminum wiring) Lead frame: Cu (bond the above chip to the lead frame using die attach paste) Molding: 175 ℃, 2 minutes Post mold cure: 175 ℃, 4 hours Total number of packages: 12

<Comparative Examples 1 to 7> Each component having the composition shown in Table 2 was mixed, 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]

[0030]

[Table 2]

Organic peroxide 1: manufactured by NOF CORPORATION, cumyl peroxyneodecanate (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.

[0032]

The die attach paste of the present invention is excellent in low stress due to the combination of a flexible structure urethane di (meth) acrylate and a reactive diluent having a (meth) acrylic group, and further, diallyl monoglycidyl isocyanuric acid. Is a fast-curing paste in which the adhesiveness after moisture absorption is improved, and as a result, excellent solder crack resistance is exhibited.

Claims (4)

(57) [Claims] 1. A urethane di (meth) acrylate obtained by reacting (A) hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate, (B) a reactive diluent having a (meth) acrylic group,
(C) diallyl monoglycidyl isocyanuric acid, (D)
A phosphoric acid group-containing (meth) acrylate represented by the general formula (1), (E) an alkoxysilane having an epoxy group,
A die attach paste comprising (F) an organic peroxide and / or an azo compound and (G) an inorganic filler. [Chemical 1] 2. A urethane di (meth) acrylate obtained by reacting the (A) hydroxyalkyl (meth) acrylic acid, polyalkylene glycol and diisocyanate, and a reactive diluent having the (B) (meth) acrylic group. The die attach paste according to claim 1, wherein the weight ratio of is 20/20 to 20/80. 3. The addition amount of the diallyl monoglycidyl isocyanuric acid (C) is 0.01 ≦ C / (A + B) ≦ 0.5 based on the total weight of the components (A) and (B). The die attach paste according to items 1 and 2. 4. A semiconductor device manufactured using the die attach paste according to claim 1.