JPH10237409A - Conductive resin paste and semiconductor device manufactured using the same - Google Patents

Abstract

(57) [Problem] To provide a conductive resin paste having excellent conductivity and excellent heat dissipation. SOLUTION: Spherical nickel powder, epoxy resin, silver powder,
As an essential component, in which spherical nickel powder is 10 to
A resin paste for bonding a semiconductor element, comprising 90% by weight, 5 to 85% by weight of silver powder, and 80 to 95% by weight of spherical nickel powder and silver powder in total.

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, and (C) an epoxy liquid which is liquid at room temperature. Resin is an essential component, which contains 10 to 90% by weight of spherical nickel powder (A), 5 to 85% by weight of silver powder (B), and (A) + (B) is 80 to 90% by weight. The present invention relates to a conductive resin paste characterized by being 97% by weight and a semiconductor device manufactured using the conductive resin paste.

[0008]

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
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.

Although the epoxy resin used in the present invention is limited to a liquid at room temperature, if it is not liquid at room temperature, more solvent is required for kneading with silver powder. The solvent is not preferable because it causes bubbles and lowers the adhesive strength of the cured product. Examples of the epoxy resin used in the present invention include bisphenol A, bisphenol F, polyglycidyl ether obtained by the reaction of phenol novolak with epichlorohydrin at room temperature, vinylcyclohexene dioxide, dicyclopentadiene oxide,
Alicyclic epoxy such as alicyclic diepoxy-adipate, furthermore n-butyl glycidyl ether, versidic acid glycidyl ester, styrene oxide phenyl glycidyl ether, butyl phenyl glycidyl ether, creglycidyl ether, dicyclopentadiene diepoxide Some of them are commonly used as diluents for epoxy resins.

In the present invention, a compound having active hydrogen in the molecule is preferably used as a curing agent. Such compounds include phenols (for example, bisphenol A, bisphenol F, bisphenol AP, bisphenol S, bisphenol Z, dimethyl bisphenol A, dimethyl bisphenol F, tetramethyl bisphenol A, tetramethyl bisphenol F, biphenol, tetramethyl biphenol, dihydroxy Diphenyl ether, dihydroxybenzophenone, o-hydroxyphenol, m-hydroxyphenol, p-hydroxyphenol, polyphenols such as phenol novolak and orthocresol novolac, trisphenols such as trihydroxyphenylmethane and trihydroxyphenylmethane), primary amines , Polyamines, imizazole and the like. These may be used alone or as a mixture.

Further, additives such as a curing accelerator, a pigment and an antifoaming agent can be used in the resin composition of the present invention, if necessary. The production method of the present invention includes, for example, preliminarily kneading each component, kneading using a three-roll mill, obtaining a paste, and defoaming under vacuum.

[0015]

The present invention will be specifically described below with reference to examples. Examples 1 to 10 Diglycidyl ether obtained by the reaction of bisphenol A and epichlorohydrin (liquid at room temperature with an epoxy equivalent of 180, hereinafter epoxy resin), cresyl glycidyl ether (CGE) as diluent, and phenol novolak as curing agent (CGE) Hydroxyl equivalent 110), 2-phenyl-4-methylimidazole (2P4MZ), further, spherical nickel powder having an average particle diameter of 6, 28 μm and an average particle diameter of 1,
13 μm spherical silver powder and flake silver powder having an average particle diameter of 13 μm were blended at the ratios shown in Tables 1 and 2, and kneaded with a three-roll mill 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. The evaluation results are shown in Tables 1 and 2.

[0016]

[Table 1]

[0017]

[Table 2]

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 13 Conductive resin pastes were prepared in exactly the same manner as in the examples with the mixing ratios shown in Tables 3 and 4.

[0020]

[Table 3]

[0021]

[Table 4]

Comparative Examples 1 and 2 When the amount of silver powder alone or the amount of nickel powder is less than the claimed range, the silver powder is granulated during kneading and does not form a paste. Comparative Example 3 A paste was prepared using nickel powder and silver powder.
The spreadability of the coating decreased. Comparative Examples 4 and 5 In the case of the nickel powder alone or the silver powder content less than the claimed range, a paste could be produced but the conductivity after moisture absorption was reduced. Comparative Example 6 When the average particle size of the nickel powder was smaller than that of the silver powder, a paste could not be produced due to the granulation of the silver powder. Comparative Example 7 When the average particle size of the nickel powder was smaller than 5 μm, kneading could not be performed because the viscosity was too high. Comparative Example 8 When the average particle size of the nickel powder was larger than 30 μm, kneading was possible but the paste thickness was large due to the large particle size of the nickel powder, so that satisfactory conductivity could not be obtained. Comparative Example 9 Since the average particle size of the silver powder was too small, the viscosity was too high and kneading was difficult. Comparative Example 10 Since the average particle size of the silver powder was large, the paste thickness was large, and satisfactory conductivity could not be obtained. Comparative Examples 11 and 12 When the compounding amount of nickel powder and silver powder was less than 80% by weight, satisfactory conductivity was not obtained. Comparative Example 13 When the blending amount of the nickel powder and the silver powder exceeded 97% by weight, the amount of the resin was too small to obtain a paste.

[0023]

The conductive resin paste of the present invention has good conductivity between the semiconductor element and the metal frame, has good wet spreadability of the paste during die bonding, and further has ionic impurities such as sodium and chlorine. Less copper, 42
It can be used for bonding semiconductor elements such as ICs and LSIs to metal frames such as alloys, ceramic substrates, and organic substrates such as glass epoxy.

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 epoxy resin which is liquid at room temperature is an essential component, which contains 10 to 90% by weight of spherical nickel powder (A) and 5 to 85% by weight of silver powder (B). )
+ (B) is 80 to 97% by weight of the conductive resin paste. 2. A semiconductor device manufactured by using the conductive resin paste according to claim 1.