JP3389083B2 - Die attach paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a die attach paste which is excellent in adhesiveness, low-stress properties, and solder crack resistance and can be cured in a very short time. SOLUTION: This die attach paste contains (A) a reaction product of a phosphate-group-contg. acrylate and/ or a phosphate-group-contg. methacrylate represented by the formula: [CH2 =CRCOO(CH2 )2 -(OCO(CH2 )5 )a ]c OPO(OH)b (R is H or CH3 ; a is 0 or 1; b is 1 or 2; and c is 1 or 2 provided b+c is 3), a monoacrylate represented by the formula: CH2 =CHCOOR1 or a monomethacrylate represented by the formula: CH2 =CCH3 COOR1 (R1 is a 10C or higher substituent having an alicyclic and/or arom. group), and a polymn. initiator, (B) a urethane diacrylate prepd. by reacting a hydroxyalkylacrylic acid, a polyalkylene glycol, and a diisocyanate, and (C) a silver powder.

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 excellent in low stress property, adhesive property and fast curing property.

[0002]

2. Description of the Related Art In recent years, the production amount of semiconductor packages has been on the rise and the reduction of manufacturing cost has become an important issue. In the process of assembling a semiconductor package, there is a step of adhering a semiconductor and a lead frame with a die attach paste. The key points in this step are time reduction and low temperature curing. The curing process is roughly classified into a batch type oven method and a method of curing with an in-line (heating plate etc.), and shortening the curing time is important in any method from the viewpoint of cost reduction. When using a so-called fast-curing paste used in-line, the usual die mounting is performed at 150 to 200 ° C. for 30 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.

Further, in the case of oven curing as well, improvement in productivity is similarly required, and therefore shortening of curing time is indispensable. In the case of oven curing, usual die mounting is performed at 150 ° C. to 200 ° C. for 60 minutes to 120 minutes, but in the future, it will be required to cure within 20 minutes. In addition, since it is currently in the transitional period from oven curing to in-line curing, it is not possible to completely focus on in-line curing. Therefore, development of an oven / in-line curing combined paste is also required.

On the other hand, the solder crack resistance is particularly important for the reliability of the package, but the die attach paste requires particularly low stress and high adhesiveness.

Epoxy resin, cyanate resin, bismaleimide resin, etc. are known as the base resin of the die attach paste. For example, inline curing can be performed within 30 seconds and / or oven curing can be performed within 15 minutes. No material capable of maintaining the properties suitable for solder crack resistance has been found. Further, even if the properties were satisfied, the viscosity at room temperature increased so much that only materials suitable for use were available.

Other resins include acrylate resins, but none of them has been found to be practical such as the problem of curing shrinkage and poor adhesion.

Among them, hydroxyalkyl acrylic,
Urethane acrylate obtained by reacting dialkylene glycol and diisocyanate is a resin system that is expected to reduce stress due to flexibility of the main chain skeleton. However, although this resin alone has an excellent stress property, it still has a poor adhesive force and has a problem. Therefore, as a method for solving this problem, a method using phosphoric acid ester is further disclosed
It is proposed in Japanese Patent Publication No. 292048. However, according to the studies by the present inventors, in the field of semiconductors, for bonding a semiconductor chip to a metal lead frame or an organic substrate typified by a glass-epoxy resin, no adhesive strength can be obtained by only those components. Things turned out.
This is 2 in the process of attaching the gold wire etc. to the semiconductor chip and the lead frame (hereinafter referred to as wire bonding).
This is because it is necessary to raise the temperature to 00 ° C. or higher, and the adhesive force at the time of heating cannot be obtained at all by the above-mentioned constituents alone, and the inorganic surface and the organic substance at the high temperature (200 ° C. to 350 ° C.) as in the application of the present invention can be obtained. Adhesion needed further improvement.

[0008]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The present invention has been studied to improve the drawbacks of the above-mentioned acrylate resin, and as a result, a specific acrylate resin, a polymerization initiator, a specific phosphoric acid-based compound as a coupling agent, and an oil. When an alkoxysilane containing a cyclic epoxy group and silver powder were combined, it was found that the semiconductor chip had excellent adhesiveness to the metal frame or the organic substrate. However, in the paste manufacturing process, the pot life of the paste obtained by kneading all the components of the adhesive (time when the viscosity rises by 10%) is remarkably deteriorated, and it is suitable for die attach applications where an accurate coating amount is required for a long time. Turned out to be a problem. As a result of investigating the cause, specific mono (meth) acrylates, phosphoric acid esters, and alicyclic alkoxysilanes were kneaded in advance, and each was allowed to stand at room temperature or in a warmed state for a predetermined time, and then alicyclic epoxy group alkoxy It was found that the paste pot life is sufficiently extended by sufficiently reacting silane with a (meth) acrylate having a phosphoric acid group and a polymerization initiator under diluting conditions, and then mixing and kneading the remaining components. It was
Further, it was found that the obtained paste is a die attach paste that maintains excellent adhesiveness, low stress, solder crack resistance, and can be hardened in a very short time, and completed the present invention. It is a thing.

[0009]

The present invention SUMMARY OF] is the next (A), (B) component and the (C) die attachment paste characterized by containing Ingredient. (A) a phosphoric acid group-containing acrylate and / or a phosphoric acid group-containing methacrylate having the following structure (1), an alkoxysilane containing an alicyclic epoxy group, a monoacrylate having the following structure (2a) or the following structure (2b): What was made to react with the monomethacrylate which has and a polymerization initiator at 0-50 degreeC, (B) Hydroxyalkyl acrylic acid, polyalkylene glycol, Urethane diacrylate obtained by making diisocyanate react, (C) Silver powder.

[0010]

[Chemical 1] (In the formula, R: -H or -CH ₃ , a: 0 or 1, b: 1 or 2, c: 1 or 2, b + c = 3)

[0011]

[Chemical 2] (In the formula, R _{1 is} a substituent having an alicyclic and / or aromatic group and having 10 or more carbon atoms)

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Urethane acrylate used in the present invention is hydroxyalkyl acrylic acid,
It is synthesized by the reaction of polyalkylene glycol and diisocyanate.

Examples of hydroxyalkyl acrylic acid include 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate. Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polybutylene glycol and the like. or,
Examples of diisocyanates include hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate and hydrogenated products thereof.

Further, since urethane diacrylate generally has a high viscosity, it is not suitable for practical use as it is even if it is made into a paste and the coating workability is poor. Therefore, a relatively low-viscosity component obtained by reacting a mono (meth) acrylate having one (meth) acrylic group, a phosphate group-containing ester, and an alicyclic alkoxysilane as a diluent is added. Further, the mono (meth) acrylate used in the present invention has the formula (2a), (2b)
Further, it is essential that the substituent R1 contains an alicyclic group and / or an aromatic group and the total number of carbon atoms in the substituent R1 is 10 or more. By satisfying this condition, not only the effect as a diluent but also the bulky substituent can suppress shrinkage during curing and enhance the adhesion reliability of the interface. When the substituent does not contain an alicyclic group or an aromatic group and has 10 or more carbon atoms, the curing shrinkage can be reduced, but the adhesive property is deteriorated due to the characteristics of the aliphatic hydrocarbon, which is not preferable. Examples of mono (meth) acrylate

[0015]

[Chemical 3]

And the like. The phosphate group-containing ester used in the present invention is not particularly limited as long as it is represented by the formula (1), but examples include Nippon Kayaku.
For example, PM-21 manufactured by Co., Ltd.

The ratio of component (A) to component (B) is 8 by weight.
It is preferably 0/20 to 20/80. Ingredient (A)
If the amount exceeds 80/20, the paste viscosity becomes too high and the coating workability deteriorates. On the other hand, if it is less than 20/80, the adhesive strength cannot be obtained.

Next, examples of the polymerization initiator include organic peroxides and azo compounds. The decomposition temperature of organic peroxide in the rapid heating test (decomposition start temperature when 1 g of sample is placed on an electric heating plate and heated at 4 ° C./minute) is from 40 ° C. to 14 ° C.
It is preferably 0 ° C. This is because if the decomposition temperature is less than 40 ° C, the storage stability at room temperature becomes poor, and if it exceeds 140 ° C, the curing time becomes extremely long.

Examples of organic peroxides include cumyl peroxy neodecaneate, t-butyl peroxy neodecaneate, 1-cyclohexyl-1-methylethylperoxy neodecaneate, 1,1,3,3. -Tetramethylbutylperoxyneodecanate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate,
Bis (4-butylcyclohexyl) peroxydicarbonate, t-butylperoxyisopropyl monocarbonate, 1,1-bis (t-butylperoxy) -3,
3,5-Trimethylcyclohexane, t-butylperoxybenzoate, t-butylperoxy 3,5,5-
Trimethylhexanate, t-butylperoxy-2-
There are ethylhexyl monocarbonate, t-hexylperoxy-2-ethylhexanate and the like, and examples of the azo compound include 2,2′-azobisisobutyronitrile,
1,1′-azobis (1-acetoxy-1-phenylethane) and the like.

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

The amount of these organic peroxides and / or azo compounds added may be 0.1% by weight to 5% by weight based on the total weight of the component (A) + component (B). Preferably, if it is 0.1% or less, the curing rate will be slow, and if it is 5% by weight or more, the adhesive strength will decrease, which is not preferable.

Next, examples of the silver powder include spherical or flake-shaped silver powder. The average particle size is 0.5 μm to 15
μm is preferred. If the average particle size is less than 0.5 μm, the product viscosity will be high, making it impossible to knead rolls, and if the average particle size is more than 15 μm, the nozzle will be clogged when the paste is applied using a dispenser or the adhesive layer. Is difficult to control and is not preferable. As the addition amount,
It is preferably in the range of 60% by weight to 85% by weight based on the total paste. If it is less than 60%, the volume resistivity becomes high, and if it exceeds 85%, the paste viscosity becomes high, which is not preferable in coating workability.

Next, the alkoxysilane containing an alicyclic epoxy group is, for example, KBM-3 manufactured by Shin-Etsu Chemical Co., Ltd.
03 etc. are known.

The total amount of the acrylate or methacrylate represented by the formula (1) and the alkoxysilane containing an alicyclic epoxy group is from 0.1% by weight to 5% by weight with respect to the total weight of the component (A) + the component (B). It is preferably in the weight%. 0.
If it is 1% or less, the adhesiveness is not shown, and if it is more than 5%, the viscosity remarkably increases.

Further, in the present invention, it is essential that each component of the component (A) is previously reacted at a temperature of 0 to 50 ° C. A temperature lower than 0 ° C is not preferable because the reaction does not proceed sufficiently, and a temperature higher than 50 ° C is not preferable because a side reaction occurs. When the paste obtained by reacting the mixture in the range of 0 to 50 ° C. for 1 hour or more is used as the component (A) of the present invention, the paste obtained has excellent storage stability, low stress, adhesiveness and fast curing. Therefore, it is preferable.

If desired, the resin paste in the present invention may contain additives such as the above-mentioned polymerization inhibitor, defoaming agent, surfactant and solvent. Hereinafter, the present invention will be specifically described with reference to Examples.

[0027]

Example 1 Phenoxydiethylene glycol monoacrylate (Shin-Nakamura Chemical Co., Ltd., AMP-20GY) 25 parts by weight (monoacrylate-1), 2-phenylphenol / oxirane adduct monoacrylate (Shin-Nakamura Chemical) Industrial Co., Ltd., A-L4) 25 parts by weight (monoacrylate-2), phosphoric acid group-containing methacrylate (Nippon Kayaku Co., Ltd., KAYA)
MER, PM-21) 1 part by weight alicyclic epoxyalkoxysilane (Shin-Etsu Chemical Co., Ltd.,
KBM-303) 0.5 parts by weight organic peroxide initiator (Nippon Yushi Co., Ltd., Park Mill N)
D) 1.0 part by weight

The above raw materials are kneaded with a three-roll mill to form a transparent uniform viscous solution, which is then allowed to stand for 24 hours in a thermostat at 25 ° C. for reaction. The resulting solution (hereinafter referred to as varnish 1) 2
Urethane diacrylate-1 consisting of hydroxyethyl acrylate, polybutylene glycol, and isophorone diisocyanate to 5 parts by weight (Toagosei Co., Ltd.
Manufactured by M-1600, 25 parts by weight, silver powder (manufactured by Degussa, S
130 parts by weight of F-65) and 20 parts by weight of silver powder (manufactured by Tokuriki Kagaku Kenkyusho Co., Ltd., TCG-1) are mixed and dispersed and kneaded again by a three-roll mill. Subsequently, defoaming treatment was performed under vacuum to obtain a silver paste.

The viscosity of the obtained silver paste was measured using an E-type rotational viscometer immediately after preparation and after 1 week (at 25 ° C.), and the viscosity increase rate was calculated from the value at 2.5 rpm.
As a result, the rate of increase in viscosity remained at about 9%, and it became clear that the product can be stored for a long period of time without being frozen. After applying the obtained silver paste to the 42 alloy frame, 6
Mount a mm-square chip and put it in an oven (150 ℃ 1
It was cured for 5 minutes) or on a heating plate (175 ° C. for 60 seconds).
The adhesive strength was measured at room temperature (25 ° C.) and during heating (250 ° C.) using an automatic shear strength measuring device. As a result, it was confirmed that sufficient adhesive strength could be obtained even at the wire bonding temperature (about 250 ° C.), and chip separation was not observed at all even using an ultrasonic flaw detector (shown in Table 1).

Other Evaluation Methods Peeling after wire bonding: 6 m on lead frame
A m × 15 mm chip was mounted, cured, and wire-bonded at 250 ° C. to observe whether the chip was peeled off.

Warp value: Measured as an evaluation of low stress.
6 mm x 15 mm x 0.
3mm silicon chip with paste 175 ℃ 6
Bonding was performed so that the paste thickness became 20 μm in 0 seconds, the displacement of the chip in the longitudinal direction was measured using a contact type surface roughness meter, and the warp value was measured by the height difference.

Solder crack resistance: Sumicon EME-73
Using 20 (Sumitomo Bakelite Co., Ltd.) sealing material,
The package molded under the following conditions is 85 ℃, relative humidity 8
After water absorption at 5% for 168 hours, IR reflow (24
The number of internal cracks was measured by observing the cross section at 0 ° C. for 10 seconds) and used as an index of solder crack resistance.

Package: 80 pQFP (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., all for 4 hours Number of packages: 12 Overall evaluation: One that can be used as a die attach paste is evaluated as ◯, and one that cannot be used is evaluated as x.

Example 2 Of the varnish components of Example 1, monoacrylate-3 was used instead of monoacrylate-1 and monoacrylate-4 was used instead of monoacrylate-2 (varnish-2), and Table 1 The silver paste was obtained by the same method as in Example 1 except for the composition and conditions shown in Table 2 and its characteristics were evaluated. The results are as shown in Table 1.

Example 3 Among the varnish components of Example 1, monomethacrylate-1 was used instead of monoacrylate-1 to react (varnish-3), except for the composition and conditions shown in Tables 1 and 2. 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 Table 1.

Examples 4 to 8 A silver paste was obtained by the same method as in Example 1 except for the composition and conditions shown in Table 1, and its characteristics were evaluated. The results are as shown in Table 1.

Comparative Example 1 A paste was obtained and evaluated in the same manner as in Example 1 except that the amount of Varnish-1 in Example 1 was changed to 50 parts by weight and no urethane diacrylate was added. The results are as shown in Table 2. Comparative Example 2 The paste was obtained by adding the remaining components without reacting the varnish components of Example 1 and evaluating them. The results are as shown in Table 2.

Comparative Example 3 A paste was obtained and evaluated in the same manner as in Example 1 except that the phosphoric acid group-containing methacrylate was removed from the varnish component of Example 1 (varnish-4). The results are as shown in Table 2. Comparative Example 4 A paste was obtained and evaluated in the same manner as in Example 1 except that the alicyclic alkoxysilane was removed from the varnish component of Example 1 (varnish-5). The results are as shown in Table 2.

Comparative Example 5 Monoacrylate-1,2 from the components of the varnish of Example 1
A paste was obtained and evaluated in the same manner as in Example 1 except that (varnish-6) was removed. The results are as shown in Table 2. Comparative Example 6 A paste was obtained and evaluated in the same manner as in Example 1 except that the varnish component of Example 1 was 0 and urethane diacrylate was used in an amount of 50 parts by weight. The results are as shown in Table 2.

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Chemical 4]

Polymerization initiator 1: manufactured by NOF CORPORATION, cumylperoxyneodecanate (decomposition temperature in rapid heating test: 65 ° C.) Silver powder 1: Degussa, SF-65 Silver powder 2: Co., Ltd. Made by Tokuriki Kagaku Kenkyusho, TCG-1

[0044]

Industrial Applicability According to the present invention, it has become possible to manufacture an industrially useful semiconductor bonding paste having not only low stress and fast curing properties, but also storage properties and adhesive properties, which have been the conventional problems.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI C08L 75:16) (56) Reference JP-A-11-171944 (JP, A) JP-A-11-171943 (JP, A) JP-A-7-292048 (JP, A) JP-A-11-186297 (JP, A) JP-A-11-189763 (JP, A) JP-A-62-54710 (JP, A) JP-A-62-54711 (JP, A) JP 63-235317 (JP, A) JP 11-172205 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08L 63/00-63 / 10 C09J 163/00-163/10 H01L 21/52

Claims (7)

(57) [Claims] 1. The following components (A), (B) and (C):
Die attach paste, characterized in that it contains a Ingredient. (A) a phosphoric acid group-containing acrylate and / or a phosphoric acid group-containing methacrylate having the following structure (1), an alkoxysilane containing an alicyclic epoxy group, a monoacrylate having the following structure (2a) or the following structure (2b): What was made to react with the monomethacrylate which has and a polymerization initiator at 0-50 degreeC, (B) Hydroxyalkyl acrylic acid, polyalkylene glycol, Urethane diacrylate obtained by making diisocyanate react, (C) Silver powder. [Chemical 1] (In the formula, R: -H or -CH ₃ , a: 0 or 1, b: 1 or 2, c: 1 or 2, b + c = 3) (In the formula, R _{1 is} a substituent having an alicyclic and / or aromatic group and having 10 or more carbon atoms) 2. The weight ratio of the component (A) to the component (B) is 8.
The die attach paste according to claim 1, which is 0/20 to 20/80. 3. The polymerization initiator as component (A) is an organic peroxide and / or an azo compound having a decomposition temperature of 40 ° C. to 140 ° C. in a rapid heating test. Die attach paste. 4. The addition amount of the polymerization initiator used in the component (A) is 0.1% by weight to the total weight of the component A + the component B.
The die attach paste according to claim 1, 2 or 3, which is 5% by weight. 5. The average particle size of component (C) is 0.5 to 15 μm.
m is claim 1, claim 2, claim 3, or claim 4
The die attach paste according to item 1. 6. The method of claim 1 the amount added is 60 wt% to 85 wt% of component A~ component C total weight of component (C), claim 2, claim 3, claim 4, or claim 5 The die attach paste according to item 1. 7. The total weight of the alkoxy silane containing a phosphoric acid group-containing acrylate and / or a phosphoric acid group-containing methacrylate and an alicyclic epoxy used in the component (A) is the total of the component (A) + the component (B). The die attach paste according to claim 1, which is 0.1 to 5% by weight based on the weight.