JPH11335630A - Die attaching paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a die attaching paste capable of maintaining excellent adhesiveness, soldering crack resistance and the like and curable in short time by combinedly including a urethane di(meth)acrylate resin, a specified coupling agent and a specified polymerization initiator. SOLUTION: This paste is obtained by essentially including (A) a urethane di(meth)acrylate, (B) a (meth)acrylic-modified polybutadiene, (C) a monoacrylate of formula I (R<1> is a >=10C substituent such as an alicyclic group), (D) a phosphate group-including (meth)acrylate of formula II or formula III [(a) is 0 or 1; (b) and (c) are each 1 or 2 and (b)+(c)=3], (E) an alicyclic epoxy group- containing alkoxysilane, (F) an organic peroxide or an azo compound and (G) powdered silver. The compounding weight ratios for the respective components are as follows: 1<=A/B<=25, 0.3<=(A+B)/C<=6.0, 0.001<=(D+E)/(A+B+C)<=0.05, 0.1<=D/E<=10 and 0.001<=F/(A+B+C)<=0.05.

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 is excellent in low stress, adhesiveness after moisture absorption, and rapid curing.

[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 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 oven method and an in-line curing method. From the viewpoint of cost reduction, an in-line curing method is becoming widespread. The usual die bonding step using a so-called fast-curing paste used in-line is performed at 150 to 200 ° C. for 30 to 60 seconds. However, in the future, development of a paste that can be cured at a lower temperature and for a shorter time is desired.

[0003] On the other hand, the reliability of the package is particularly important in terms of solder crack resistance in a large chip, but the die attach paste is particularly important in low stress properties and adhesiveness (when absorbing moisture). 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 maintains characteristics suitable for solder crack resistance. No material 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.

[0004]

SUMMARY OF THE INVENTION The present invention has been studied to improve such disadvantages of the acrylate resin, and as a result, urethane diacrylate or methacrylate resin,
It has been found that a combination of a specific coupling agent and a polymerization initiator is a die attach paste that maintains excellent adhesiveness, low stress, and solder crack resistance, and can be cured in a very short time. However, with respect to the solder crack resistance, it was found that cracks were caused by peeling of the die attach layer after solder reflow at a more severe level of the moisture absorption processing conditions. Therefore, by combining hydrophobic acrylate or methacrylate-modified butadiene, the adhesive strength is maintained, and the moisture absorption rate and the adhesive strength after moisture absorption are reduced, and the die crack paste has solder crack resistance at a more severe level (moisture absorption treatment). To complete the invention of the present application.

[0005]

The present invention provides the following (A)
To (G) as essential components, and their weight ratios are [a] to
This is a die attach paste represented by [e]. (A) urethane diacrylate or methacrylate obtained by reacting hydroxyalkylacrylic acid or methacrylic acid, polyalkylene glycol, and diisocyanate, (B) acryl or methacryl-modified polybutadiene, (C) mono represented by the general formula (1) Acrylate, (D) phosphate group-containing acrylate represented by general formula (2) or phosphate group-containing methacrylate represented by general formula (3), (E) alkoxysilane containing alicyclic epoxy group, (F) organic Peroxide or azo compound, (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

[0006]

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

[0007]

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

[0008]

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

The urethane diacrylate used in the present invention is synthesized by a conventional method by reacting hydroxyalkylacrylic acid, polyalkylene glycol, and diisocyanate. Examples of hydroxyalkyl acrylic acids include 2-hydroxyethyl acrylate or methacrylate, 2-hydroxypropyl acrylate or methacrylate. Examples of the polyalkylene glycol include polyethylene glycol, polypropylene glycol, polybutylene glycol, and the like.

Examples of the diisocyanate include hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate and hydrogenated products thereof. Next, examples of acrylic-modified or methacryl-modified polybutadiene include those obtained by adding maleic anhydride to polybutadiene and subjecting the maleic anhydride to a ring-opening reaction with hydroxyalkyl methacrylate, and epoxidizing the double bond of polybutadiene to obtain acrylic acid or methacrylic acid. Examples include those obtained by ring-opening addition of an epoxy group with an acid.

Further, the mixing ratio (A) of urethane diacrylate (A) and acrylic or methacryl-modified polybutadiene (B)
/ (B) needs to satisfy 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 decreases.

Urethane diacrylate or methacrylate (A) and acrylic or methacryl-modified polybutadiene (B)
Cannot be pasted because of its high viscosity. Therefore, a monoacrylate containing one acrylic group is added as a diluent. Further, the monoacrylate used in the present invention is represented by the formula (1), and further the substituent R ₁ is alicyclic,
And / or an aromatic group containing 10 carbon atoms in the substituent R ₁
It is indispensable that the number is at least. 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. Examples of monoacrylates

[0013]

Embedded image

And the like, and one or more kinds can be added. Urethane diacrylate or methacrylate
(A) and the ratio of monoacrylate to acrylic or methacryl-modified polybutadiene (B) ｛(A) + (B)｝ / (C) is 0.3 ≦
It is preferable that {(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 heating 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 components (A) + (B) + (C) + (D) + (E) + (F)
Or methacrylic modified polybutadiene for
(B) compounding ratio (B) /) (A) + (B) + (C) + (D) + (E) + (F)｝ is 0.01 ≦
(B) / {(A) + (B) + (C) + (D) + (E) + (F)}. If it is less than 0.01, the moisture-resistant adhesiveness is impaired.

Next, examples of the acrylate or methacrylate containing a phosphate group include:

Embedded image Wherein a is 0 or 1, b is 1 or 2, c is 1 or 2, and b + c = 3.

As the alkoxysilane containing an alicyclic epoxy group, for example, KBM-303 manufactured by Shin-Etsu Silicone is known. Phosphate group-containing acrylate represented by formula (2) or phosphate group-containing methacrylate represented by formula (3)
The total amount of addition of (D) and alkoxysilane (E) containing an alicyclic epoxy group {(D) + (E)} is urethane diacrylate or methacrylate (A) + acryl or methacryl-modified polybutadiene (B) + monoacrylate (C) total weight {(A) + (B) +
(C)} to {(D) + (E)} / {(A) + (B) + (C)}
It is preferable that 0.001 ≦ {(D) + (E)} / {(A) + (B) + (C)} ≦ 0.05. If it is less than 0.001, there is no effect on the adhesiveness, and 0.0
If it is more than 5, the adhesiveness decreases.

Further, in the present invention, component (D) and component (D)
(E) is an essential component, and the present invention cannot be embodied even if one of them is applied. The composition ratio (D) / (E) is 0.1 ≦ (D) / (E) ≦ 1
0 is preferred. If it is less than 0.1, the concentration of the alkoxysilane becomes low, and the effect on the adhesive interface is reduced. On the other hand, if it exceeds 10, the phosphate group concentration becomes high and acts more than necessary on the adhesive interface, thereby lowering the adhesiveness. Further, it is not preferable because the paste viscosity increases with the rapid reaction with the alicyclic epoxy resin.

As the action of the components (D) and (E), when they are mixed, an alicyclic epoxy polymerizes to form an oligomer having an alkoxysilane in the side chain, and the adhesion to the interface is strengthened. It is estimated that

Examples of the organic peroxide 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.

These organic peroxides and / or azo compounds
As the addition amount of (F), the compounding ratio (F) / {(A) + (B) + (C)} is 0.00
It is preferable that 1 ≦ (F) / {(A) + (B) + (C)} ≦ 0.05. 0.
If it is less than 001, the curing speed is slow, and if it is more than 0.05, the adhesive strength is reduced and the paste has poor hot life, which is not preferable.

Next, as an example of the silver powder (G), a flake shape is preferable, and the average particle size is 0.5 μm to 1 μm.
5 μm is preferred. If the average particle size is smaller than 0.5 μm, the product viscosity increases, and kneading of rolls and the like becomes impossible,
On the other hand, if the average particle size is larger than 15 μm, it is not preferable because nozzle clogging at the time of paste application using a dispenser or the like or the thickness of the adhesive layer is difficult to control. 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, which 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, if necessary.

Hereinafter, the present invention will be described specifically with reference to Examples.

[0026]

Example 1 Urethane diacrylate obtained by reacting hydroxyethyl acrylate, polybutylene glycol, and isophorone diisocyanate (urethane diacrylate 1-Toagosei Co., Ltd., M-1600) 23.75 weight Part Hydroxyalkyl methacrylate modified resin of maleic anhydride-added polybutadiene as methacryl-modified polybutadiene (methacryl-modified polybutadiene 1, MM-1000-80 manufactured by Nippon Oil Co., Ltd.) 1.25 parts by weight Phenoxydiethylene glycol monoacrylate (monoacrylate) as monoacrylate 1, Shin Nakamura Chemical Co., Ltd., AMP-20GY) 25 parts by weight Phosphate group-containing methacrylate (phosphate group-containing methacrylate 1, Nippon Kayaku Co., Ltd., KA YAMER, PM-21) 0 .5 parts by weight alicyclic 0.25 parts by weight of an organic peroxide polymerization initiator (Alicyclic ethoxy group-containing alkoxysilane 1, Shin-Etsu Chemical Co., Ltd., KBM-303) , Park Mill ND) 0.5 parts by weight Silver powder 1 (manufactured by Degussa Corp., SF-65) 130 parts by weight Silver powder 2 (manufactured by Tokurika Chemical Laboratory Co., Ltd., TCG-1) 20 parts by weight The mixture was dispersed and kneaded with a roll, followed by defoaming 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). As a result, wire bonding temperature (about 250 ° C) or 85 ° C, 85% RH after curing
It was confirmed that a sufficient adhesive strength was obtained even with the heat strength after the treatment, and no peeling of the chip was observed even when the ultrasonic flaw detector was used (shown in Table 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 subjected to a water absorption treatment at 85 ° C. and a relative humidity of 85% 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 used as an index of solder crack resistance.

Package: 80pQFP (14 × 20 × 2 mm) Chip size: 7.5 × 7.5 mm (only aluminum wiring) Lead frame: 42 alloy Molding: 175 ° C., 2 minutes Post-mold cure: 175 ° C., 4 hours Total number of packages: 12 : The one that can be used as a die attach paste was evaluated as ○, and the one that could not be used was evaluated as ×.

Examples 2 to 8, Comparative Examples 1 to 13 Except for the compositions and conditions shown in Tables 1, 2 and 3, a silver paste was obtained in exactly the same manner as in Example 1, and its characteristics were evaluated. . The results are as shown in Tables 1, 2 and 3.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

Description of compounds in the table

Embedded image

Polymerization initiator 2: 2,2'-azobisisobutyronitrile, acrylic-modified polybutadiene: polymer obtained by the same reaction as methacryl-modified polybutadiene (MAC-1000-80, manufactured by Nippon Oil Co., Ltd.)

[0038]

According to the present invention, an initial adhesive strength and a low adhesive strength can be obtained by combining a specific bulky monoacrylate or methacrylate with urethane diacrylate or methacrylate, acrylate or methacrylate containing a phosphate group, or alkoxysilane containing an alicyclic epoxy group. It was found that by exhibiting stress properties and further adding an appropriate amount of acrylic or methacryl-modified polybutadiene, the initial adhesion and low stress properties were maintained, and the moisture resistance was excellent, resulting in more excellent solder crack resistance.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09J 175/14 C09J 175/14 H01L 21/52 H01L 21/52 E

Claims (1)

[Claims] 1. A die attach paste comprising the following components (A) to (G) as essential components, and their weight ratios are represented by [a] to [e]. (A) urethane diacrylate or methacrylate obtained by reacting hydroxyalkylacrylic acid or methacrylic acid, polyalkylene glycol, and diisocyanate; (B) acrylic or methacryl-modified polybutadiene; Acrylate, (D) phosphate group-containing acrylate represented by general formula (2) or phosphate group-containing methacrylate represented by general formula (3), (E) alkoxysilane containing alicyclic epoxy group, (F) organic Peroxide or azo compound, (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 (Wherein, R _{1 is} a substituent having an alicyclic and / or aromatic group and having 10 or more carbon atoms) (Where a: 0 or 1, b: 1 or 2, c: 1 or 2,
b + c = 3) (Where a: 0 or 1, b: 1 or 2, c: 1 or 2,
b + c = 3)