JPH1192625A - Electroconductive resin paste and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject resin paste excellent in electroconductivity and heat dissipation property, and useful for the adhesion of a semiconductor to a metal frame, a ceramic base plate, etc., by including a silver coated aluminum powder, silver powder, resin component and organic peroxide. SOLUTION: This electroconductive resin paste is obtained by including (A) 10-90 wt.% silver coated aluminum powder having 5-60 μm mean particle diameter, (B) 5-85 wt.% silver powder having 0.5-15 μm mean particle diameter, (C) a resin component, 0.1-50 wt.% of which is an acrylic or a methacrylic resin expressed by formula I (R1 , R2 are each H or CH3 ) or formula II (R3 , R4 are each H or CH3 ) and (D) an organic peroxide (e.g.; 1,1,3,3-tetramethyl butylperoxy-2-ethylhexanoate) as indispensable components. Further, the ratio of the components (A)+(B) is 75-97 wt.%. In the resin paste, an additive such as another resin, various silane coupling agents, a pigment, etc., can be added as necessary.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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, in recent years, a structure in which electricity flows from the back surface of the semiconductor element to the metal frame is not always required for grounding with the progress of semiconductor element and semiconductor device design in recent years. 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 in which lead used in solder is not used, and furthermore, when solder is used, cost reduction is required by reducing a necessary flux cleaning step. IC, L from the meaning
Although the conductive resin paste used for SI has been developed for discrete use, the current flowing through the semiconductor device is 2 to 2.
In some products, a large current of about 3 A flows, and satisfactory conductivity cannot be obtained with the conventional conductive resin paste. 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.

However, in a semiconductor product that flows a large current, a large amount of heat is generated by this current, and the heat generated causes the temperature of the conductive resin paste to increase. 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.

In the case of manufacturing the above-mentioned semiconductor product using a conductive resin paste, some of the batch methods using an oven satisfy the thermal conductivity and conductivity, but the manufacturing method using solder originally requires a batch method. Since the time required for bonding the semiconductor element is about 5 to 15 seconds on a hot plate, the conventional conductive resin paste generates voids during curing, so that thermal conductivity and electrical conductivity are remarkably reduced. Was difficult to achieve.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a conductive resin paste excellent in conductivity and heat dissipation, and a semiconductor device using the same.

[0009]

According to the present invention, there are provided (A) a silver-coated aluminum powder having an average particle size of 5 to 60 μm, (B) a silver powder having an average particle size of 0.5 to 15 μm, and (C) a general formula ( A resin component in which the acrylic resin or methacrylic resin represented by 1) or (2) is 0.1 to 50% by weight of the total resin component; and (D) an organic peroxide as an essential component, and silver in the component. It contains 10 to 90% by weight of coated aluminum powder (A) and 5 to 85% by weight of silver powder (B), and (A) +
(B) 75 to 97% by weight of a conductive resin paste and a semiconductor device manufactured using the conductive resin paste.

[0010]

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[0011]

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[0012]

In the conductive resin paste for semiconductors according to the present invention, silver powder is generally used as a filler for imparting conductivity. In the present invention, not only silver powder but also silver-coated aluminum powder is essential. It is. The reason why silver-coated aluminum powder is used in combination with silver powder is that, in order to further improve conductivity and heat dissipation, it is customary to increase the ratio of metal. Therefore, if a conductive resin paste is prepared using only silver powder, the cost becomes high. Therefore, aluminum powder, which is lower in cost than silver powder, is used. However, the surface of aluminum powder is oxidized even at room temperature to produce aluminum oxide.
Therefore, it is not suitable for improving the conductivity which is the object of the present invention. Therefore, silver having good conductivity is coated on the aluminum powder. By doing so, the conductivity which aluminum powder lacked can be supplemented, and heat dissipation can be improved. The particle size of the silver powder used in the present invention is preferably smaller than the particle size of the silver-coated aluminum powder. The reason for this is that a relatively large silver-coated aluminum powder alone forms a gap between the particles, which reduces heat dissipation and conductivity.

In the present invention, the combined amount of silver-coated aluminum powder and silver powder must be 75 to 97% by weight. If the combined amount of silver-coated aluminum powder and silver powder is less than 75% by weight, conductivity and 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. It is desirable that the silver-coated aluminum powder is 10 to 90% by weight and the silver powder is 5 to 85% by weight. If the silver-coated aluminum powder is less than 10% by weight, the conductivity is reduced. If the silver-coated aluminum powder exceeds 90% by weight, entrapment voids are large during the preparation of the paste, and the cured product becomes brittle.

The silver-coated aluminum powder used in the present invention preferably has a spherical shape. 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 silver-coated aluminum powder is desirably 5 to 60 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.
As a method of silver coating on silver-coated aluminum powder, there is a method of plating silver on the surface of aluminum powder, and a method of putting aluminum powder into a silver ion solution and forming a silver film by utilizing the ionization tendency of metal. There is no particular limitation in the present invention.

The silver powder used in the present invention has an average particle size of 0.5 to 0.5.
15 μm is desirable. Although the shape can be more highly filled with a spherical shape, the viscosity is reduced by adding a spherical silver-coated aluminum powder having a relatively large particle size as in the present invention. There is no particular limitation on the workability. If the average particle size is smaller than 0.5 μm, roll-kneading is impossible even with the addition of spherical silver-coated aluminum powder, or even if kneading is possible, the viscosity is too high to allow dispensing, not to mention coating by screen printing, resulting in a high viscosity. Would. Conversely, if the average particle size is larger than 15 μm, the particle size distribution becomes very narrow,
Since the fluidity is reduced, the spreadability of the coating is significantly reduced, which is not preferable. In the present invention, other metal powders such as copper and gold may be mixed within the above range.

The general formula (1) or (2) used in the present invention
The acrylic resin or methacrylic resin represented by has an acrylic or methacrylic group that undergoes radical polymerization, and one of them has a glycidyl group. As a result, polymerization using only acrylic resin is usually
Although the polymerization rate is high, the curing shrinkage is large, and since the curing reaction like epoxy does not generate a hydroxyl group effective for adhesion to metal or silicon, adhesion is poor, and a conductive resin paste for bonding semiconductor elements as in the present invention. Has been unsuitable for However, when a resin such as (1) or (2) is used, a glycidyl group is contained in the acrylic resin. Thus, a hydroxyl group is generated by a curing reaction of the glycidyl group as in a conventional epoxy, so that the acrylic resin or the methacrylic resin has the largest size. It is possible to obtain a conductive resin paste that can improve the adhesiveness, which has been a drawback, and can be bonded in a short time as compared with a resin system containing only epoxy. In addition, in the case of conductive resin paste that uses ordinary liquid epoxy resin, the liquid epoxy resin or organic solvent with a lower viscosity than used to adjust the viscosity volatilizes during curing, generating voids in the cured product and causing heat. Conductivity, but reduces the conductivity, the conductive resin paste of the present invention, since the reaction mechanism is radical polymerization,
Even when an acrylic resin or a methacrylic resin having a lower viscosity is used, the polymerization reaction is rapid and hardly volatilizes, and as a result, a cured product having extremely few voids can be obtained. When cured with a hot platen, satisfactory thermal conductivity and conductivity can be obtained as compared with the conventional epoxy-based conductive resin paste.

Further, other acrylic resins, methacrylic resins, epoxy resins and the like can be used together within the above range. As acrylic resin, for example,
Monoacrylate or methacrylate such as monoacrylate such as acryloyloxyethyl hydrogen succinate and lauryl acrylate, ethylene glycol acrylate, , 3-butadienglycol acrylate, diacrylates and dimethacrylates such as 2,2-bis {4- (acryloxydiethoxy) phenyl} propane, etc .; Naphthalene and the like.

The organic peroxide used in the present invention is not particularly limited. For example, 1,1,3,3-
Tetramethyl-butylperoxy-2-ethylhexanate, t-butylperoxy-2-ethylhexanate, t-hexylperoxy-2-etholhexanate, 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. These peroxides can be used alone or in combination of two or more. Further, various polymerization inhibitors may be added in advance to improve the storage stability of the resin.

Further, additives such as other resins, various silane coupling agents, pigments and defoamers 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.

Hereinafter, the present invention will be described specifically with reference to Examples. Examples 1 to 14 Bisphenol F-monoacrylate ester (general formula
(1), R ₁ , R ₂ = -H; hereinafter acrylic resin 1) or its methacrylate (general formula (2), R ₁ , R ₂ = -H; methacrylic resin 1), bisphenol A-monoacrylate ester (general Formula (1), R ₁ , R ₂ = —CH ₃ ; acrylic resin 2), lauryl acrylate (hereinafter acrylic resin 3) or its methacrylate (hereinafter methacrylic resin 2), bis (4-t-butylcyclohexyl) as a polymerization initiator ) Peroxydicarbonate (hereinafter referred to as TCP), diglycidyl ether obtained by reacting bisphenol A with epichlorohydrin (liquid at room temperature with an epoxy equivalent of 180, hereinafter referred to as epoxy resin), and 2-phenyl-4- as a curing agent for epoxy resin Methyl imidazole (hereinafter referred to as 2P4MZ), a spherical silver-coated aluminum powder having an average particle size of 6, 28, and 58 μm, and an average particle size of 1, 13 μm The spherical silver powder with an average particle size 13μ
m flake silver powder in the proportions shown in Tables 1 and 2,
The conductive resin paste was obtained by kneading with three rolls. 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.

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 on a hot plate at 150 ° C. for 30 seconds, and the volume resistivity of the cured product was measured. Vertical volume resistivity: Paste is applied on a copper frame, and a 2 × 2 mm copper plate is cured on a hot plate at 150 ° C. for 30 seconds. Then, the voltage between the copper plate surface and the copper frame is determined, and the vertical volume of the cured product is obtained therefrom. The resistivity was calculated. 250 ° C. hot adhesive strength: A 2 mm square silicon chip was mounted on a copper frame using a paste and cured on a 150 ° C. hot plate for 30 seconds. After curing, the die shear strength at 250 ° C. under heat 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.

[0022]

[Table 1]

[0023]

[Table 2]

Comparative Examples 1 to 10 Conductive resin pastes were prepared in exactly the same manner as in the examples with the mixing ratios shown in Tables 3 and 4. In Comparative Example 1, since the acrylic resin 2 exceeded 50% by weight of the total resin components, sufficient adhesive strength could not be obtained in curing. Comparative Example 2
Since acrylic resins 1 and 2 and methacrylic resin 1 were not used, sufficient adhesive strength could not be obtained in curing.
In Comparative Examples 3 and 4, since the acrylic resins 1 and 2 exceeded 50% by weight, spreadability was poor and satisfactory adhesive strength could not be obtained. In Comparative Example 5, when only the silver-coated aluminum powder was used, the volume resistivity was lowered because the silver powder did not assist the contact between the silver-coated aluminum powders. In Comparative Example 6, when only silver powder was used, the silver powder was crushed at the time of roll kneading and the viscosity was increased. In Comparative Example 7, when a flake-shaped silver powder was used instead of a spherical silver powder, the viscosity was increased and the coating workability and spreadability were deteriorated. In Comparative Example 8, since the average particle size of the silver-coated aluminum powder was less than 5 μm, the viscosity was high and the workability was significantly reduced. In Comparative Example 9, since the average particle size of the silver-coated aluminum powder exceeded 60 μm, good workability could be obtained with a low viscosity, but the low viscosity resulted in easy precipitation of the filler and low conductivity. Comparative Example 10
When using only epoxy as the resin, the curing speed was slower than when using an acrylic resin, so that sufficient adhesive strength and electrical conductivity could not be obtained.

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

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.

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[Submission date] March 25, 1998

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Claims (2)

[Claims] (A) silver-coated aluminum powder having an average particle size of 5 to 60 μm, (B) silver powder having an average particle size of 0.5 to 15 μm, (C) represented by the general formula (1) or (2). Acrylic resin or methacrylic resin in the total resin component is 0.1 to 5
A resin component of 0% by weight, and (D) an organic peroxide as essential components, containing 10 to 90% by weight of silver-coated aluminum powder (A) and 5 to 85% by weight of silver powder (B). A conductive resin paste, wherein (A) + (B) is 75 to 97% by weight. 2. A semiconductor device using the conductive resin paste according to claim 1. Embedded image Embedded image