JP3250793B2 - Conductive resin paste and semiconductor device using the same - Google Patents

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 nickel powder having an average particle size of 5 to 60 μm, and (B) an nickel powder having an average particle size of 0.
(C) a resin component in which the acrylic resin or methacrylic resin represented by the general formula (1) or (2) is 0.1 to 50% by weight of the total resin component, and (D) an organic resin. Peroxide is an essential component, and nickel powder (A) is 10 to 90% by weight and silver powder (B) is 5% in the component.
８５85% by weight, and (A) + (B) is 7
A conductive resin paste characterized by being 5 to 97% by weight and a semiconductor device manufactured using the conductive resin paste.

[0010]

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[0011]

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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 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.

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. In the present invention, other metal powders such as copper and gold may be mixed within the above range.

The general formula (1) used in the present invention or
The acrylic resin or methacrylic resin represented by (2) has an acryl or methacryl group that undergoes radical polymerization, and one of them has a glycidyl group. As a result, polymerization with acrylic resin alone has a higher polymerization rate than epoxy, but has a large curing shrinkage, and has poor adhesion because it does not generate a hydroxyl group effective for adhesion to metal or silicon by a curing reaction like epoxy. ,
It has not been suitable for a conductive resin paste for bonding a semiconductor element as in the present invention. However, when a resin such as (1) or (2) is used, since a glycidyl group is contained in the acrylic resin, a hydroxyl group is generated by a curing reaction of the glycidyl group as in a conventional epoxy resin. 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 the case of conductive resin paste using ordinary liquid epoxy resin, the liquid epoxy resin or organic solvent with lower viscosity than used to adjust the viscosity volatilizes during curing, generating voids in the cured product and causing heat. Although the conductivity and the conductivity are reduced, the conductive resin paste of the present invention hardly volatilizes because the reaction mechanism is radical polymerization, and the polymerization reaction is fast even when a lower-viscosity acrylic resin or methacrylic resin is used. 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-butadiene glycol acrylate, and diacrylates or dimethacrylates such as 2,2-bis {4- (acryloxydiethoxy) phenyl} propane, etc., and the epoxy resin is an epibis epoxy, 2,6-diglycidyl. 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.

[0020]

The present invention will be specifically described below 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), and spherical nickel powder having an average particle size of 6, 28, and 58 μm and spheres having an average particle size of 1, 13 μm Flakes silver powder having an average particle size of 13μm in proportions shown in Table 1 and Table 2 and silver powder, to obtain a conductive resin paste by kneading through 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, the acrylic resins 1 and 2 contained 5% of all resin components.
Since it exceeded 0% by weight, spreadability was poor and satisfactory adhesive strength could not be obtained. In Comparative Example 5, when only the nickel powder was used, the silver powder did not assist the contact between the nickel powders, so that the volume resistivity was lowered. 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 high.
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 nickel powder was less than 5 μm, the viscosity was high and the workability was significantly reduced. In Comparative Example 9, the average particle size of the nickel powder was 6
Since the thickness exceeds 0 μm, good workability can be obtained with a low viscosity, but the low viscosity results in easy sedimentation of the filler and low conductivity. In Comparative Example 10, when only epoxy was used as the resin, the curing speed was slower than when acrylic resin was used, 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.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI C09J 9/02 C09J 9/02 133/14 133/14 163/10 163/10 H01L 21/52 H01L 21/52 E (56) References JP-A-11-92626 (JP, A) JP-A-11-92625 (JP, A) JP-A-7-126489 (JP, A) JP-A-61-296077 (JP, A) JP-A-8 JP-A-287724 (JP, A) JP-A-60-170658 (JP, A) JP-A-6-295617 (JP, A) JP-A-58-179643 (JP, A) JP-A-2-272071 (JP, A) JP-A-4-7369 (JP, A) JP-A-6-139818 (JP, A) JP-A-9-35530 (JP, A) JP-A-4-196007 (JP, A) JP-A-10- 338844 (JP, A) JP-A-10-338843 (JP, A) JP-A-10-338841 (JP, A) JP-A-10-168412 (JP, A) Flat 10-8006 (JP, A) JP flat 1-221481 (JP, A) JP-T flat 7-508555 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) H01B 1 / 20-1/24 C08G 59/00-59/72 C08K 3/00-13/08 C08L 33/00-101/10 C09J 9/00-201/10 H01L 21/52

Claims (2)

(57) [Claims] (A) nickel powder having an average particle size of 5 to 60 μm, (B) spherical silver powder having an average particle size of 0.5 to 15 μm,
(C) a resin component in which the acrylic resin or methacrylic resin represented by the general formula (1) or (2) is 0.1 to 50% by weight of all resin components, and (D) an organic peroxide as essential components. , Nickel powder (A) in the component is 10 to 90;
A conductive resin paste containing 5 to 85% by weight of silver powder (B) and 75 to 97% by weight of (A) + (B). 2. A semiconductor device using the conductive resin paste according to claim 1. Embedded image Embedded image