JP3209959B2 - Die attach paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die attach paste which is improved in adhesion and curing rate, by a method wherein a specific acrylic resin, a coupling agent, and a polymerization initiator are combined to form the die attach paste. SOLUTION: Die attach paste comprises (A) urethane diacrylate or methacrylate obtained through a reaction which takes place among hydroxy alkyl acrylic acid or methacrylic acid, polyalkylene grycol, and di-isocyanate, (B) copolymer of butadiene with a vinyl group as an end group and acrylonitrile, (C) monoacrylate represented by a formula I or monomethacrylate represented by a formula II (in formulas I and II, R1 includes a cycloaliphatic group and/or an aromatic group and denotes a substituting group whose number of carbons is 10 or above), (D) phosphate group-containing acrylate represented by a formula III or a phosphate group-containing methacrylate represented by a formula IV (in formula III and IV, a denotes 0 or 2, b is 1 or 2, c is 1 or 2, b+c=3), (E) alkoxysilane possessed of a cycloaliphatic epoxy group, (F) organic peroxide or azo compound, and (G) silver powder as integral components, where the weight ratio of them is represented by a formula V ([a] to [f]).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paste for bonding a semiconductor which has excellent low stress, adhesiveness after moisture absorption, and excellent curing properties.

[0002]

2. Description of the Related Art In recent years, the production volume of semiconductor packages has been on a steadily increasing step, and the accompanying reduction in manufacturing costs has become an important issue. A semiconductor package assembly includes a process of bonding a semiconductor (IC chip) and a lead frame with a die attach paste. In this process, time reduction and low-temperature curing are important points in production. The curing process is roughly classified into a batch-type oven method and a method of curing in-line (such as a hot platen). From the viewpoint of cost reduction, a method of curing in-line is spreading. When a so-called fast-curing paste used in-line is used, a usual die mounting (chip bonding) process is performed in 150 steps.
It is carried out at a temperature of from 30 to 60 seconds at a temperature of from 200C to 200C. However, in the future, development of a paste that can be cured at a lower temperature and for a shorter time is desired.

On the other hand, the reliability of a completed package is particularly important for solder crack resistance in a large chip, and prevents cracking of the package caused by peeling of the die attach paste layer even when exposed to high temperatures during solder bonding. For this purpose, the die attach paste is required to have particularly low stress properties and adhesion after moisture absorption.

As the base resin of the die attach paste, a cyanate resin, a bismaleimide resin, and the like are known, mainly an epoxy resin. For example, the resin can be cured within 30 seconds and has characteristics suitable for solder crack resistance. No material to maintain was found. Further, even if the properties were satisfied, there was only a material which was unsuitable for use because the viscosity at room temperature increased too much. As another resin, an acrylate resin can be cited as a candidate. However, there has been a problem such as curing shrinkage, and there has been found no resin which is poor in adhesiveness and suitable for practical use.

[0005] Further, as a material of the lead frame, for example, a metal such as 42 alloy or copper is mainly used, but recently a BGA (ball grid array) package has been frequently used in order to improve the performance of computers. It has become For this reason, the adhesion between the chip (semiconductor) and the solder resist (organic substrate) has been gaining considerable importance. 60 to 12 at 150 ° C to 200 ° C
Paste that cures over 0 minutes has already been commercialized using epoxy resin, but in the future, to improve productivity,
Since curing within 15 minutes has been required,
New materials need to be developed.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to improve the disadvantages of the acrylate resin and to provide a die attach paste having low stress, excellent adhesion to various frames, and excellent curability.

[0007]

Means for Solving the Problems The present inventors have studied to improve such disadvantages of the acrylate resin, and as a result, have found that a combination of a urethane acrylate or methacrylate resin, a specific coupling agent, and a polymerization initiator can be used. It has been found that this is a die attach paste that maintains excellent adhesiveness, low stress, and solder crack resistance and can be cured even in a very short time. However, with respect to the solder crack resistance, it was found that cracks were generated due to the detachment of the die attach layer after solder reflow at a more severe level of moisture absorption processing conditions (higher temperature and higher humidity). Therefore, by adding the hydrophobic component B, the adhesive strength is strengthened, the water absorption rate and the adhesive strength after the moisture absorption treatment are hardly reduced, and a die having sufficient solder crack resistance even after the moisture absorption treatment under more severe conditions. Successfully obtained touch paste. Furthermore, it has been found that even when this paste is cured in a short time (within 15 minutes) with respect to an organic substrate, excellent adhesive strength can be obtained, and the present invention has been completed.

That is, the present invention is a die attach paste comprising the following components (A) to (G) as essential components, and the weight ratio of each component is represented by [a] to [f]. (A) urethane diacrylate or methacrylate obtained by reacting hydroxyalkylacrylic acid or methacrylic acid, polyalkylene glycol and diisocyanate, (B) a copolymer of butadiene having terminal vinyl group and acrylonitrile, (C) a general formula (1
a) a monoacrylate represented by a) or a monomethacrylate represented by the general formula (1b):

[0009]

Embedded image (In the formula, R ₁ : a substituent containing an alicyclic and / or aromatic group and having 10 or more carbon atoms)

(D) a phosphoric acid group-containing acrylate represented by the general formula (2) or a phosphoric acid group-containing methacrylate represented by the general formula (3);

[0011]

Embedded image (In the formula (2), a: 0 or 1, b: 1 or 2, c: 1 or 2, b + c =
3)

[0012]

Embedded image (In the formula (3), a: 0 or 1, b: 1 or 2, c: 1 or 2, b + c =
3)

(E) an alkoxysilane having an alicyclic epoxy group, (F) an organic peroxide or an azo compound, and (G) silver powder. [A] 1 ≦ A / B ≦ 25 [b] 0.3 ≦ (A + B) /C≦6.0 [c] 0.001 ≦ (D + E) / (A + B + C) ≦
0.05 [d] 0.1 ≦ D / E ≦ 10 [e] 0.001 ≦ F / (A + B + C) ≦ 0.05 [f] 0.60 ≦ G / (A + B + C + D + E + F +
G) ≦ 0.85

[0014]

DETAILED DESCRIPTION OF THE INVENTION The urethane acrylate used in the present invention is a hydroxyalkyl acrylic acid,
It is synthesized by the reaction of polyalkylene glycol and diisocyanate.

Examples of hydroxyalkylacrylic acids include 2-hydroxyethyl acrylate or methacrylate, 2-hydroxypropyl acrylate or methacrylate. Examples of polyalkylene glycols are polyethylene glycol and polypropylene glycol,
And polybutylene glycol. Examples of diisocyanates include hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate and hydrogenated products thereof.

An example of the copolymer of butadiene and acrylonitrile having a vinyl group at the terminal of the component B is VTBN (manufactured by Ube Industries, Ltd.). It is necessary that the compounding ratio of the component A and the component B is 1 ≦ A / B ≦ 25. If it is less than 1, the initial adhesiveness is poor, and if it is more than 25, the moisture-resistant adhesiveness is reduced.

Since the components A and B have high viscosities, they are not suitable for practical use due to poor coating workability even if they are pasted. Therefore, 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 has the formula (1a)
Or (1b), wherein the substituent R ₁ is an alicyclic group,
And / or an aromatic group and the total number of carbon atoms in the substituent R1 is 1
It is essential that the number is zero or more. By satisfying this condition, not only the effect as a diluent but also the presence of a bulky substituent can suppress shrinkage during curing, thereby improving the bonding reliability of the interface. 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. As an example of the mono (meth) acrylate, R _{1 in} the general formula (1a) or (1b) is

[0018]

Embedded image

And the like. One or more of them can be blended and added. The ratio of component C to component A and component B is preferably 0.3 ≦ (A + B) /C≦6.0. If it is less than 0.3, the crosslinking density is extremely reduced, and the adhesive strength at the time of heat is reduced. On the other hand, if it exceeds 6.0, the viscosity is too high, and the coating workability deteriorates, which is not preferable. Further, the compounding ratio of the component B to the components A to F is 0.01 ≦ B / (A
+ B + C + D + E + F). 0.0
If it is less than 1, the moisture-resistant adhesiveness is impaired.

The alkoxysilane having an alicyclic epoxy group is, for example, KBM- manufactured by Shin-Etsu Chemical Co., Ltd.
303 and the like are known. The total amount of the components D and E is 0.001 ≦ (D + E) / to the total weight of the components A to C.
It is preferable that (A + B + C) ≦ 0.05. 0.
If it is less than 001, no effect is exerted on the adhesiveness, and if it is more than 0.05, the viscosity is remarkably increased with the reaction between the components D and E, and the adhesiveness is rather decreased.

In the present invention, component D and component E are essential components, and the present invention cannot be embodied even if one of them is applied.
The composition ratio is preferably 0.1 ≦ D / E ≦ 10. 0.1
If it is lower than the above, the concentration of the alkoxysilane becomes low, and the effect on the adhesive interface is lowered. On the other hand, if it exceeds 10, the phosphoric acid group concentration becomes too high and acts on the bonding interface more than necessary, thereby lowering the adhesiveness.

The effects of the components D and E are presumed to be that when they are mixed, the alicyclic epoxy is polymerized, an oligomer having an alkoxysilane in the side chain is formed, and the adhesion to the interface becomes strong. You.

Next, examples of organic peroxides include cumyl peroxyneodecanate, t-butylperoxyneodecanate, 1-cyclohexyl-1-methylethylperoxyneodecanate, 1,1,3 , 3-Tetramethylbutylperoxyneodecanate, 1,1,3,3-
Tetramethylbutylperoxy-2-ethylhexanate, bis (4-butylcyclohexyl) peroxydicarbonate, t-butylperoxyisopropylmonocarbonate, 1,1-bis (t-butylperoxy)-
3,3,5-trimethylcyclohexane, t-butylperoxybenzoate, t-butylperoxy 3,5
5-trimethylhexanate, t-butylperoxy-
Examples include 2-ethylhexyl monocarbonate and t-hexylperoxy-2-ethylhexanate. Examples of azo compounds include 2,2′-azobisisobutyronitrile and 1,1′-azobis (1-acetoxy). -1-phenylethane) and the like.

These organic peroxides and / or 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 / or azo compounds is 0.001 ≦ F / (A + B + C) ≦
Preferably, it is 0.05. If it is less than 0.001, the curing speed will be slow, and if it is more than 0.05, the adhesive strength will be lowered and the pot life of the paste will be unfavorably deteriorated.

Next, as an example of the silver powder, a flake shape is preferable, and further, the average particle size is 0.5 μm to 15 μm.
m is preferred. If the average particle size is smaller than 0.5 μm, the product viscosity increases, and kneading with a roll or the like becomes impossible. If the average particle size is larger than 15 μm, nozzle clogging during paste application using a dispenser or the like, or an adhesive layer Is difficult to control, which is not preferable. The amount added is preferably in the range of 60% by weight to 85% by weight based on the total paste. When it is less than 60%, the volume resistivity increases, and when it exceeds 85%, the paste viscosity increases,
It is not preferable in application workability.

In the resin paste of the present invention, the above-mentioned additives such as a polymerization inhibitor, an antifoaming agent, a surfactant, a solvent, and a thixotropic agent can be used as necessary. Hereinafter, the present invention will be described specifically with reference to Examples.

[0028]

Example 1 Urethane diacrylate obtained by reacting hydroxyethyl acrylate, polybutylene glycol, and isophorone diisocyanate (M-1600, manufactured by Toagosei Co., Ltd.) 47.5 parts by weight Vinyl at the terminal Copolymer of butadiene and acrylonitrile having a group (VTBE (1300X33) manufactured by Ube Industries, Ltd.) 2.5 parts by weight Nonylphenol propylene oxide-modified monoacrylate (M-117 manufactured by Toagosei Co., Ltd.) 25 parts by weight Part Phenoxydiethylene glycol monoacrylate (AMP-20GY, manufactured by Shin-Nakamura Chemical Co., Ltd.) 25 parts by weight Phosphate group-containing methacrylate (Nippon Kayaku Co., Ltd., KAYAMER, PM-21) 1 part by weight Alicyclic epoxy alkoxy Silane (Shin-Etsu Chemical Co., Ltd., KBM-303) 0.5 Parts by weight Organic peroxide initiator (Nippon Yushi Co., Ltd., Park Mill ND) 1.4 parts by weight

The above-mentioned raw materials are kneaded with three rolls to form a transparent uniform viscous solution, and then allowed to stand in a thermostat at 25 ° C. for 3 days. To 25 parts by weight of the obtained solution (referred to as varnish), 65 parts by weight of silver powder (manufactured by Degussa, SF-65) and 10 parts by weight of silver powder (manufactured by Tokurika Chemical Laboratory, TCG-1) were mixed. Then, the mixture is again dispersed and kneaded with three rolls. Subsequently, a degassing treatment was performed under vacuum to obtain a silver paste.

The viscosity of the obtained silver paste was measured at 2.5 rpm using an E-type viscometer. Further 42
6mm after applying the silver paste obtained on the alloy frame
Mount the corner chip and place it on a hot plate (175 ° C, 40 seconds)
And cured. The adhesive strength was measured at room temperature (25 ° C) and hot (250 ° C) by an automatic shear strength measuring device (DAGE, BT
-100). Further, the adhesion to the organic substrate was measured in exactly the same manner. A solder resist (PSR-4000 / manufactured by Taiyo Ink Co., Ltd.) is formed on a bismaleimide-triazine (BT) resin substrate as an organic substrate.
CA-40) was used. The paste was cured in an oven (170 ° C. for 15 minutes).

As a result, at both the 42 alloy frame and the organic substrate, the wire bonding temperature (about 250
) Or at 85 ° C after curing and 85% RH treatment, it was confirmed that sufficient adhesive strength could be obtained, and no chip peeling was observed even with an ultrasonic flaw detector (see Table 1). 1).

Other evaluation methods Peeling after wire bonding: 6 m on lead frame
A chip of 15 mm in size was cured after mounting, and wire bonding was performed at 250 ° C., and the presence or absence of peeling of the chip was observed.

Warpage value: Measured for evaluation of low stress property.
6mmX15mmX0.
175 ° C using a 3 mm silicon chip with paste,
The paste was adhered so that the thickness of the paste became 20 μm in 40 seconds, the displacement of the chip in the longitudinal direction was measured using a contact type surface roughness meter, and the warpage value was measured based on the height difference.

Solder crack resistance: Sumicon EME-73
Using a sealing material of No. 20 (manufactured by Sumitomo Bakelite Co., Ltd.), a package molded under the following conditions was used at 85 ° C. and a relative humidity of 85:
% After a water absorption treatment for 168 hours, followed by IR reflow (240
C., 10 seconds × 3 times), the number of internal cracks was measured by cross-sectional observation, and the index was used as an index of solder crack resistance.

Package: 80pQFP (14X20X
2mm) Chip size: 7.5 x 7.5mm (Aluminum wiring only) Lead frame: 42 alloy Molding: 175 ° C, 2 minutes Post-mold cure: 175 ° C, 4 hours Total package number: 12 Total evaluation: Can be used as die attach paste The sample was evaluated as ○ and the unusable sample was evaluated as ×.

Examples 2 to 6, Comparative Examples 1 to 11 A silver paste was obtained in the same manner as in Example 1 except for the composition and conditions shown in Tables 1 and 2, and the characteristics were evaluated.
The results are as shown in Tables 1 and 2.

[0037]

[Table 1]

[0038]

[Table 2]

Description of Compounds in Table Urethane acrylate 1: Urethane diacrylate obtained by reacting hydroxyethyl acrylate, polybutylene glycol, and isophorone diisocyanate (M-1600, manufactured by Toagosei Co., Ltd.) Urethane acrylate 2: Urethane diacrylate obtained by reacting hydroxyethyl acrylate, polypropylene glycol, and isophorone diisocyanate (UA-160PG, manufactured by Shin-Nakamura Chemical Co., Ltd.) Modified polybutadiene: a copolymer of butadiene and acrylonitrile having a terminal vinyl group (Ube Industries, Ltd.)
VTBN (1300X33)

[0040]

Embedded image

Component D: a = 1, b in the general formula (3)
= 1, C = 2 Component E: Alicyclic epoxy group-containing alkoxysilane (KBM-303, manufactured by Shin-Etsu Chemical Co., Ltd.) Polymerization initiator 1: Cumyl peroxyneodecanate (Nippon Oil & Fats Co., Ltd.) Polymer Initiator 2: Wako Pure Chemical Industries, Ltd., 2,2'-azobisisobutyronitrile silver powder 1: Degussa, SF-65 (average particle size: 11 μm)
m) Silver powder 2: TCG-1 (average particle size: 2 μm), manufactured by Tokuriki Chemical Laboratory Co., Ltd.

[0042]

According to the present invention, the initial adhesive force and low stress can be obtained by combining a specific bulky monoacrylate or methacrylate with urethane acrylate or methacrylate, acrylate or methacrylate containing a phosphate group, or alkoxysilane containing an alicyclic epoxy group. It was clarified that, by expressing the properties and further adding a suitable amount of the modified polybutadiene, the initial adhesion and low stress were maintained, the moisture adhesion was excellent, and as a result, the solder crack resistance was more excellent.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C09J 163/00 C09J 163/00 175/04 175/04 183/04 183/04 // C08F 290/00 C08F 290/00 (56 JP-A-1-304169 (JP, A) JP-A-4-123713 (JP, A) JP-A-7-292048 (JP, A) JP-A-10-130600 (JP, A) 10-330441 (JP, A) JP-A-11-12551 (JP, A) JP-A-11-171943 (JP, A) JP-A-11-171944 (JP, A) JP-A-11-172205 (JP, A) A) JP-A-11-265900 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/52 C09J 4/00 C09J 9/00 C09J 175/00 C08F 290/00

Claims (2)

(57) [Claims] 1. A die attach paste comprising the following components (A) to (G) as essential components, and their weight ratios being represented by [a] to [f]. (A) urethane diacrylate or methacrylate obtained by reacting hydroxyalkylacrylic acid or methacrylic acid, polyalkylene glycol and diisocyanate, (B) a copolymer of butadiene having terminal vinyl group and acrylonitrile, (C) a general formula (1
monoacrylate represented by a) or monomethacrylate represented by the general formula (1b): (Wherein, R ₁ : a substituent containing an alicyclic and / or aromatic group and having 10 or more carbon atoms) (D) a phosphate group-containing acrylate represented by the general formula (2) or a general formula (3) A phosphate group-containing methacrylate represented by the formula: (In the formula (2), a: 0 or 1, b: 1 or 2, c: 1 or 2, b + c =
3) (In the formula (3), a: 0 or 1, b: 1 or 2, c: 1 or 2, b + c =
3) (E) an alkoxysilane having an alicyclic epoxy group, (F) an organic peroxide or an azo compound, and (G) silver powder. [A] 1 ≦ A / B ≦ 25 [b] 0.3 ≦ (A + B) /C≦6.0 [c] 0.001 ≦ (D + E) / (A + B + C) ≦
0.05 [d] 0.1 ≦ D / E ≦ 10 [e] 0.001 ≦ F / (A + B + C) ≦ 0.05 [f] 0.60 ≦ G / (A + B + C + D + E + F +
G) ≦ 0.85 2. The die attach paste according to claim 1, wherein component G has an average particle size of 0.5 to 15 μm.