JPH1112551A - Electroconductive resin paste and semiconductor device produced by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject paste, excellent in electroconductivity and further heat radiating properties by including a specific spherical nickel powder, a specified silver powder, specific two kinds of (meth)acrylic resins and an organic peroxide in a specific proportion therein. SOLUTION: This paste is obtained by including (A) 10-90 wt.% of a spherical nickel powder having 5-30 μm average particle diameter, (B) 5-85 wt.% of a silver powder having 0.5-15 μm average particle diameter so as to provide 80-97 wt.% total amount of the components A and B, (C) a resin component composed of (i) an acrylic or a methacrylic resin represented by formula I or II R1 is CH2 , C(CH3 )2 , etc.; R2 is Cn H2n [(n) is >=4]; (X+Y) is >=4}, (ii) 0.1-50 wt.% (based on the total resin) of an acrylic or a methacrylic resin represented by formula III or IV I (a) is 0 or 1; (b) and (c) are each 1 or 2; [(b)+(c)] is 3}, (D) an organic peroxide (e.g. 1,1,3,3-tetramethylbutyl peroxy-2- ethylhexanate) and, as necessary, (E) an adhesion improving component such as another resin or a silane coupling agent, a pigment, a defoaming agent, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin paste for bonding a semiconductor element such as an IC or an LSI to a substrate such as a metal frame.

[0002]

2. Description of the Related Art In the process of assembling a semiconductor device, a bonding method used in a process of bonding a semiconductor element to a metal frame, that is, a so-called die bonding process has been changed from a gold-silicon eutectic to a solder and a resin paste. . At present, conductive resin paste is mainly used for assembling ICs and LSIs, and usually solder is used for discretes such as transistors and diodes.

[0003] In semiconductor devices such as ICs and LSIs, a method of using a resin paste having a lower stress property to solder has been used because the area of the semiconductor element is large. In this resin paste, flake silver powder is dispersed in an epoxy resin. However, in a method using a conductive resin paste, a requirement for conductivity between a semiconductor element and a metal frame in a semiconductor device in recent years has been reduced. This is because a recent semiconductor device does not necessarily require a structure for flowing electricity from the back surface of the semiconductor device to the metal frame in order to ground the semiconductor device along with the progress of the design of the semiconductor device. Even if electricity is passed through the conductive resin paste, the current is a very small current of about 2 to 3 mA in ICs and LSIs. With such a current, a conventional conductive resin paste in which metal powder is dispersed in a resin can sufficiently cope.

[0004] Solder to conductive resin paste has excellent conductivity and adhesiveness, and is inexpensive. In the case of discrete components such as diodes and transistors that mainly use this solder, it is necessary to flow electricity between the semiconductor element and the metal frame due to the structure of the product. However, due to recent environmental problems, each semiconductor maker is moving in a direction that does not use lead that is used for soldering. Furthermore, when solder is used, ICs are reduced in terms of cost reduction by reducing the necessary flux cleaning process. , The conductive resin paste used for LSI has been developed for discrete use, but there are products that have a large current of about 2 to 3 A flowing to the semiconductor device. I couldn't get the sex. In this regard, it is possible to obtain satisfactory conductivity even in a semiconductor product through which a large current flows by blending a filler coated with a metal film (for example, carbon, silica, glass beads, a polymer, and other inorganic fillers). there were.

[0005] However, in a semiconductor product in which a large current flows, a large amount of heat is generated by this current, and this heat is generated, thereby increasing the temperature of the conductive resin paste. In this case, the current becomes difficult to flow due to the thermal resistance, and the reliability of the semiconductor product is reduced. Therefore, when using a conductive resin paste that is excellent in such conductivity but inferior in heat dissipation, it must be a semiconductor product with a sufficient cooling mechanism, but it increases the cost and is not practical. Did not.

[0006]

SUMMARY OF THE INVENTION The present invention provides a conductive resin paste having excellent conductivity and heat dissipation.

[0007]

The present invention provides (A) a spherical nickel powder having an average particle size of 5 to 30 μm, (B) a silver powder having an average particle size of 0.5 to 15 μm, (C) the following (1) or The acrylic resin or methacrylic resin represented by the general formula (2) and the acrylic resin or methacrylic resin represented by (3) or (4), wherein the resin represented by (3) or (4) is 0.1% of the total resin. 1 to 50% by weight of a resin component, and (D) an organic peroxide as essential components, in which spherical nickel powder (A) is 10 to 90% by weight and silver powder (B) is 5 to 85% by weight. Included and (A) +
(B) is 80 to 97% by weight, and relates to a conductive resin paste and a semiconductor device manufactured using the conductive resin paste.

[0008]

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[0009]

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[0010]

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[0011]

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[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the conductive resin paste for semiconductors according to the present invention, silver powder is usually used as a filler for imparting conductivity. In the present invention, not only silver powder but also nickel powder is essential. The reason why nickel powder is used in combination with silver powder is that it is customary to increase the proportion of metal when improving conductivity and heat dissipation. However, when attempting to produce such a highly-filled conductive resin paste using only silver powder, the silver powder is crushed by mechanical force due to the rotation of the three rolls used in the production, and as a result, the silver powder is granulated. Therefore, they are not sufficiently dispersed and the conductivity, heat dissipation, and workability are significantly reduced. Therefore, the addition of nickel powder which is mechanically stronger than silver powder prevents the silver powder from being crushed. However, if the particle size of the silver powder that is easily crushed is larger than the particle size of the nickel powder, the possibility of crushing by the roll is large. Therefore, in the present invention, the particle size of the silver powder is preferably smaller than the particle size of the nickel powder. On the other hand, if an attempt is made to obtain conductivity only with nickel powder, the resistance increases because an insulating film-like insulating layer is formed on the nickel surface due to moisture absorption in a reliability test of a semiconductor product. Therefore, the point of the present invention is to maintain the conductivity by using chemical silver in combination with nickel.

In the present invention, the combined amount of nickel powder and silver powder must be 80 to 97% by weight. If the combined amount of the nickel powder and the silver powder is less than 80% by weight, the conductivity and the heat dissipation are poor. On the other hand, if it is more than 97% by weight, the viscosity becomes too high and the coating workability is remarkably reduced. 10 spherical nickel powder
It is desirable that the silver powder be 5 to 90% by weight and the silver powder be 5 to 85% by weight. If the content of the spherical nickel powder is less than 10% by weight, the silver powder is excessively granulated and the dispersibility is remarkably reduced. If the spherical nickel powder exceeds 90% by weight, the conductivity after absorbing water is undesirably reduced.

The nickel powder used in the present invention is preferably spherical. In the case of high filling as in the present invention, spherical particles are preferable because more particles can be filled because the specific surface area is small and the tap density is small. The average particle size of the nickel powder is preferably 5 to 30 μm. If the particle size is smaller than this, the viscosity increases and it becomes difficult to highly fill the metal powder. On the other hand, if it is larger than this, the thickness of the paste when applied becomes large, resulting in poor conductivity.

The silver powder used in the present invention has an average particle size of 0.5 to 0.5.
15 μm is desirable. Spherical shape allows higher filling, but the addition of spherical nickel powder having a relatively large particle size as in the present invention lowers the viscosity. Is not particularly limited because it is obtained. If the average particle size is smaller than 0.5 μm, roll kneading is impossible even with the addition of spherical nickel powder, or even if kneading is possible, the viscosity is too high and the dispensing becomes too viscous, not to mention coating by screen printing. . Conversely, if the average particle size is larger than 15 μm, the particle size distribution becomes extremely narrow, and the fluidity is reduced, so that the spreadability is remarkably reduced.

The acrylic resin or methacrylic resin represented by the formula (1) or (2) used in the present invention is:
It has the characteristic of low elastic modulus. R1 in the formula is a methylene group / isopropylene group having been industrialized. Also,
R2 in the formula is an ethylene group or an isopropylene group, but an isopropylene group is more preferable. When an ethylene group is introduced, it has high hydrophilicity and causes an increase in water absorption. In addition, as for X + Y, m + n is preferably 4 or more. If m + n is less than 4, the warpage of the chip after bonding will increase sharply, and the characteristic of low stress will be lost.

Formula (3) or (4) contained in all resins
Of acrylic resin or methacrylic resin is 0.1 to 5
0% by weight is preferred. If the amount is less than 0.1% by weight, the adhesive strength is reduced. If the amount is more than 50% by weight, outgas generated at the time of curing is increased, the contamination is reduced, and the solder crack resistance is reduced.

The organic peroxide used in the present invention is not particularly limited. For example, 1,1,3,3-
Tetramethylbutyl peroxy-2-ethyl hexanate, t-butyl peroxy-2-ethyl hexanate,
t-hexylpa-oxy-2-ethorhexanate,
1,1-bis (t-butylperoxy) -3,3,5-
Trimethylcyclohexane, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, bis (4-t-butylcyclohexyl) peroxydicarbonate and the like can be mentioned. These peroxides 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.

Further, the resin composition of the present invention may optionally contain other resins, an adhesion improving component such as a silane coupling agent, and various additives such as a pigment and an antifoaming agent. In the production method of the present invention, for example, a method of pre-kneading each component, kneading using a three-roll mill, obtaining a paste, and defoaming under vacuum is used.

[0020]

The present invention will be specifically described below with reference to examples. Example 1 R ₁ ＣC (CH ₃ ) ₂ , R ₂ ＣＨCH ₂ CH shown in formula (1)
Acrylic resin having (CH ₃ ) O, X + Y = 20 (C1
Component), a methacrylic resin represented by the formula (2) (C2 component), an acrylic resin represented by the formula (3) having a = 1, b = 1, and c = 2 (a C3 component); 3-tetramethylbutylperoxy-2
-Ethylhexanate (C5 component), and a spherical nickel powder having an average particle diameter of 6,28 μm, a spherical silver powder having an average particle diameter of 1,13 μm, and a flaky silver powder having an average particle diameter of 13 μm, in the proportions shown in Tables 1 and 2. Then, the mixture was kneaded with three rolls to obtain a conductive resin paste. After defoaming the conductive resin paste in a vacuum chamber at 2 mmHg for 30 minutes, various performances were evaluated by the following methods. Table 1 shows the evaluation results.

[0021]

[Table 1]

Examples 2 to 8 In Example 1, a methacrylic resin (a component C4) having a = 1, b = 1 and c = 2 shown in the formula (4) was used instead of the acrylic resin shown in the formula (3). Except for using the proportions shown in Table 1, a conductive paste was prepared in the same manner as in Example 1;
Various performances were evaluated. Table 1 shows the evaluation results.

Viscosity: Using an E-type viscometer (3 ° cone),
Measured at 25 ° C. and 2.5 rpm. Volume resistivity: paste 4 mm wide on a glass slide,
The coating was applied to a thickness of 30 μm and cured in an oven at 120 ° C. for 60 minutes, and the volume resistivity of the cured product was measured. Vertical volume resistivity: After applying a paste on a copper frame and curing a 2 × 2 mm copper plate in a 120 ° C. oven for 60 minutes, the voltage between the copper plate surface and the copper frame is determined, and the vertical volume resistance of the cured product is determined therefrom. The rate was calculated. In addition, the vertical volume resistivity after standing in a thermostat at a temperature of 85 ° C. and a humidity of 85% for 168 hours was also measured. 350 ° C. hot adhesive strength: A 2 mm square silicon chip was mounted on a copper frame using a paste and cured in a 180 ° C. oven for 60 minutes. After curing, the die shear strength under heat at 350 ° C. was measured using a push-pull gauge. Spreadability: The paste was applied to a copper frame and left at room temperature for 1 hour to evaluate whether the paste spread to the edge of the chip when the silicon chip was mounted. Overall evaluation: Good for all of the viscosity, volume resistivity, and adhesive strength under heat was rated as Good, and even one that was unsatisfactory was rated as Poor.

Comparative Examples 1 to 9 Conductive resin pastes were prepared in exactly the same manner as in the examples with the mixing ratios shown in Table 2.

[0025]

[Table 2]

As is clear from the results of Tables 1 and 2,
According to the present invention, a resin paste having excellent conductivity can be obtained.

[0027]

The conductive resin paste of the present invention has good conductivity between the semiconductor element and the metal frame, and has good wet spreadability of the paste during die bonding.
It can be used for bonding a semiconductor element such as an IC or an LSI to an organic substrate such as a metal frame of two alloys, a ceramic substrate, or a glass epoxy.

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Claims (2)

[Claims] (A) a spherical nickel powder having an average particle size of 5 to 30 μm, (B) a silver powder having an average particle size of 0.5 to 15 μm,
(C) An acrylic resin or methacrylic resin represented by the following general formula (1) or (2), and an acrylic resin or methacrylic resin represented by (3) or (4),
The resin shown in (3) or (4) is 0.1 to
50% by weight of a resin component and (D) an organic peroxide as essential components, the component containing 10 to 90% by weight of spherical nickel powder (A) and 5 to 85% by weight of silver powder (B). And (A) + (B) is 80 to 97% by weight. Embedded image Embedded image Embedded image Embedded image 2. A semiconductor device manufactured by using the conductive resin paste according to claim 1.