JP3189988B2 - Insulating resin paste - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating resin paste comprising a silica filler, an epoxy resin, a curing agent, and a flexibility-imparting agent for bonding a semiconductor element such as an IC or LSI to a metal frame or the like. It is.

[0002]

2. Description of the Related Art Recent remarkable developments in the electronics industry have evolved into transistors, ICs, LSIs, and VLSIs, and the degree of integration of circuits in these semiconductor devices has rapidly increased and mass production has become possible. ,
With the spread of semiconductor products using these, improvement in workability and cost reduction in mass production have become important issues. Conventionally, it has been common practice to bond a semiconductor element to a conductor such as a metal frame by an Au-Si eutectic method, and then to seal it with a hermetic seal to obtain a semiconductor product. However, in view of workability and cost during mass production, a resin encapsulation method has been developed and is now generally used. Along with this, a method using a solder material or a resin paste, that is, a mounting resin has come to be taken as an improvement of the Au-Si eutectic method in the mounting step.

However, the solder method has low reliability,
The disadvantage is that the electrodes of the element are liable to be contaminated, and the use thereof is limited to power transistors and power IC elements that require high thermal conductivity. On the other hand, the mounting resin is superior in workability and reliability as compared with the soldering method.In particular, the insulating resin paste using silica powder as a filler does not use any precious metal,
There is an increasing demand for applications that are inexpensive and require insulation in particular.

On the other hand, in recent years, a copper frame has been used for the purpose of cost reduction due to the high cost of a 42 alloy frame which is a lead frame conventionally used.
Also, chips are becoming larger due to the increase in the degree of integration of ICs and the like. When the size of a chip becomes larger than about 4 to 5 mm square, the coefficient of thermal expansion of the chip is increased by heating in the assembly process of the IC and the like. Due to the difference between the coefficient of thermal expansion of the copper frame and the coefficient of thermal expansion of the copper frame, defects in characteristics due to cracks and warpage of the chip have become a problem.

That is, the thermal expansion coefficient of silicon or the like, which is the material of the chip, is 3 × 10 ⁻⁶ / ° C., whereas that of the 42 alloy frame is 8 × 10 ⁻⁶ / ° C. This is because it becomes as large as 20 × 10 ⁻⁶ / ° C. On the other hand, the epoxy insulating resin paste used as the mounting method has a large elastic modulus and does not absorb the distortion between the chip and the copper frame. As a countermeasure, there is a method of reducing the amount of silica filler in the insulating resin paste to reduce the modulus of elasticity.However, the degree of fluctuation of the paste is reduced, and the workability is deteriorated due to dripping of the paste and stringing during dispensing. Become. When ultrafine silica powder is used in combination with the silica filler as a workability improvement method, the initial workability can be improved, but the silanol groups on the surface gradually form hydrogen bonds with the resin component, and the viscosity and thixotropic degree decrease. There was a drawback that workability deteriorated over time.

It is already known to add a polybutadiene compound having an epoxy group, which is a flexibility imparting agent, to reduce the elastic modulus of a cured product (JP-A-63-1).
However, the polybutadiene compound having an epoxy group has a high viscosity, and the viscosity of the compound to which the compound is added is high, which lowers the productivity of the compound and has poor adhesion and moisture resistance. However, the amount of the polybutadiene compound used was limited.

[0007]

DISCLOSURE OF THE INVENTION The present invention has a high degree of shaking, is excellent in workability at the time of dispenser application, does not change over time during work, and is capable of cracking chips even when a large chip such as an IC is combined with a copper frame. It is an object of the present invention to provide an insulating resin paste in which characteristic defects such as an IC due to warpage do not occur and the combined effect of the addition of a polybutadiene compound is utilized most effectively.

[0008]

According to the present invention, there is provided (A) a primary particle having an average particle size of 2 to 50 nm and 50% of silanol groups on the surface.
The above is reacted with an organosilicon compound represented by the following formula (1) to obtain a hydrophobic ultrafine silica powder having an average particle diameter of 1 to 20 μm.
m in a silica filler having a maximum particle size of 50 μm or less.
A silica filler containing 50% by weight, (B) bisphenol F and a latent amine compound, (C) an epoxy resin liquid at room temperature and (D) a polybutadiene compound having an epoxy group are essential components. An insulating resin paste containing 10 to 30% by weight of (A) and 3 to 20% by weight of a polybutadiene compound (D) having an epoxy group. Si (R) m (X) n (1) m + n = 4 R: methyl, ethyl, butyl, octyl group _{X: Cl, Br, OCH 3} , OH

The silica filler used in the present invention is a hydrophobic ultrafine silica powder whose primary particles have an average particle diameter of 2 to 50 nm and at least 50% of silanol groups are surface-treated with an organosilicon compound of the formula (1). Maximum particle size 50 with 1-20μm diameter
It is one containing 10 to 50% by weight in all the silica fillers having a size of not more than μm. When the average particle size of the primary particles is less than 2 nm, the bulk density is small, so that it is easy to fly in the air, and it is difficult to prepare such as weighing. Absent. If it exceeds 50 nm, the degree of sloshing does not increase, and improvement in workability such as dripping of the paste and stringing cannot be expected. When the ultrafine silica powder to be used is ordinary silica powder without surface treatment or 50% or more of the silica powder without surface treatment with the organosilicon compound of the formula (1), silanol groups on the surface are contained in the resin paste. The resin component gradually starts to form a hydrogen bond, and the viscosity and the degree of thixotropicity decrease, leading to a reduction in workability. On the other hand, if the amount of the hydrophobic ultrafine silica powder in the total silica filler is less than 10% by weight, the thixotropic degree of the paste is too small, causing dripping of the paste and stringing, resulting in poor workability. If it is more than 50% by weight, the viscosity of the paste becomes too high, which is not practical. The content of the silica filler in the entire composition is 10 to 30% by weight. If it is less than 10% by weight, the adhesive strength after mounting is insufficient, and if it is more than 30% by weight, a low elastic modulus of the cured product cannot be expected.
When the average particle size of the silica filler is 1 μm or less, the viscosity increases, and when the average particle size is 20 μm or more, bleeding occurs because a resin component flows out during coating or curing, which is not preferable. If the maximum particle size is 50 μm or more, the outlet of the needle is blocked when applying the paste with a dispenser, so that long-time continuous use cannot be performed.

[0010] Further, bisphenol F as a curing agent used in the present invention is a so-called bifunctional curing agent having two hydroxyl groups which react with an epoxy group in one molecule, and thus is a multifunctional curing agent such as phenol novolak. As compared with the agent, a cured product having a lower crosslink density and a lower elastic modulus is obtained, and as a result, it is very excellent in stress relaxation. In order to sufficiently exhibit the physical properties of the cured product of the bisphenol F compound, it is necessary to mix a large amount of the compound, and as a result, the viscosity of the compound increases. Therefore, in order to maximize the properties of the low elastic modulus possessed by bisphenol F and make the paste viscosity practically usable, it is preferable to use a latent amine compound having an equivalent weight smaller than that of bisphenol F. As a result, it is possible to obtain a paste which can keep the viscosity of the compound low and is practically excellent in storability due to its potential. As latent amine compounds, adipic hydrazide, dodecanoic dihydrazide, isophthalic hydrazide, P-
Examples include carboxylic acid hydrazide such as oxybenzoic acid dihydrazide and dicyandiamide.

The flexibility-imparting agent used in the present invention is a polybutadiene compound having an epoxy group. In general, polybutadiene compounds have a low elastic modulus and poor adhesion and moisture resistance. In addition, the viscosity is high, the productivity of the compound is poor, and the viscosity of the obtained paste is also high. By adding a polybutadiene compound having an epoxy group to an epoxy resin having excellent adhesiveness and moisture resistance, a paste having a low elasticity of a cured product and having excellent stress relaxation, adhesiveness and moisture resistance can be obtained.
It is important that the polybutadiene compound has an epoxy group, and if it does not react with the epoxy resin curing agent bisphenol F and the latent amine compound, separation of the epoxy resin and the polybutadiene compound occurs during curing, and the cured product becomes Not uniform. The polybutadiene compound having an epoxy group is preferably contained in the entire composition in an amount of 3 to 20% by weight, and if it is less than 3% by weight, stress relaxation cannot be obtained,
If it exceeds 20% by weight, the viscosity of the composition becomes high, the productivity decreases, and the adhesion and the moisture resistance deteriorate. For this reason, there is a limit to the elastic modulus of the cured product obtained by adding only the flexibility-imparting agent, and the viscosity tends to increase.

By limiting the curing agent to the use of bisphenol F and a latent amine compound and combining it with the addition of a polybutadiene compound having an epoxy group, it is possible to lower the elastic modulus of the cured product beyond the conventional limit. Further, since the curing agent of bisphenol F and the latent amine compound has a low viscosity, it is possible to obtain an insulating resin paste without affecting the viscosity of the polybutadiene compound. The epoxy resin used in the present invention is limited to a liquid at room temperature. However, if it is not liquid at room temperature, a solvent is required for kneading with a silica filler, which causes air bubbles to occur and reduces the adhesive strength.

The epoxy resin used in the present invention includes, for example, bisphenol A, bisphenol F, diglycidyl ether obtained by the reaction of phenol novolak with epichlorohydrin, which is liquid at normal temperature, vinylcyclohexene dioxide, dicyclopentadiene dioxide, Alicyclic epoxies, such as alicyclic diepoxy-adipate, and also normal, such as n-butyl glycidyl ether, glycidyl versatate, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, dicyclopentadiene diepoxide Some are used as diluents for epoxy resins. As a production example of the present invention, there is a method in which each component is preliminarily mixed, kneaded using a three-roll mill, a paste is obtained, and degassing is performed under vacuum.

Hereinafter, the present invention will be described in detail with reference to Examples.
The mixing ratio is shown in parts by weight.

Examples 1 to 5 Spherical amorphous silica powder having an average particle diameter of 3 μm (hereinafter referred to as “spherical silica”), primary particles having an average particle diameter of 12 nm, and about 70% of the silanol groups on the surface were treated with dimethyldichlorosilane. Hydrophobic ultrafine silica powder (hereinafter referred to as hydrophobic silica A), diglycidyl ether (liquid at room temperature with an epoxy equivalent of 180) obtained by the reaction of bisphenol A with epichlorohydrin, bisphenol F and isophthalic hydrazide or dicyandiamide and epoxy group Polybutadiene compound having the formula (Poly bd R-45E)
PT: Idemitsu Petrochemical Co., Ltd.) and cresyl glycidyl ether were blended in the ratio shown in Table 1 and kneaded with three rolls to obtain an insulating resin paste. After degassing the insulating resin paste in a vacuum chamber at 2 mmHg for 30 minutes, each characteristic was evaluated by the following methods. Table 1 shows the evaluation results.

Example 6 As the ultrafine silica powder to be used, a hydrophobic ultrafine silica powder having an average primary particle diameter of 12 nm and about 55% of the silanol groups on the surface treated with octyltrimethoxysilane (hereinafter referred to as "hydrophobic silica powder"). Silica (B) was used. Except for this, an insulating resin paste was prepared and evaluated in the same manner as in Examples 1 to 5. Table 1 shows the results.

Comparative Examples 1 to 8 Insulating resin pastes were obtained in the same proportions as in the examples at the compounding ratios shown in Table 1. In Comparative Example 5, the average primary particle size was about 12
In Comparative Examples 6 and 8, phenol novolak (softening point 110 ° C., hydroxyl equivalent 10
5), and in Comparative Example 4, a polybutadiene compound having no epoxy group (product name Poly bd R) was used as a flexibility-imparting agent.
-45HT: manufactured by Idemitsu Petrochemical Co., Ltd.). Table 1 shows the evaluation results.

[Evaluation Method] Chip Strain A silicon chip (size 6 × 12 × 0.3 mm) coated with a silver paste was mounted on a copper frame, and 200
Cured in an oven at 1 ° C for 1 hour. The height from the line connecting the both ends of the chip to the top of the warpage of the chip was measured by a surface roughness meter. Adhesive strength A silver paste is dispensed on a copper frame, a 2 mm square silicon chip is placed, and cured in an oven at 200 ° C. for 1 hour, and then left on a 350 ° C. hot plate for 20 seconds. The broken or peeled strength was measured. E-type viscosity E-type viscometer at a temperature of 25 ± 1 ° C. and a rotation speed of 2.5 rpm.
The measurement was performed using a cone three times. Fluctuation degree According to the following formula, the ratio of the viscosity at 0.5 rpm and 2.5 rpm was defined as the pliability degree. Fluctuation degree = viscosity of 0.5 rpm / viscosity of 2.5 rpm Stringing property A pin having a diameter of 3 mmφ was sunk into a sample to a depth of 5 mm, pulled up at a speed of 300 mm / min, and the height of the paste when it was cut It was measured. Paste 5 Paste 5 into a syringe with a needle with an inner diameter of 1.0 mm.
Fill the tube vertically with the needle down and the needle down.
After 0 minute, the weight of the paste dropped on the tip of the needle was measured.

[0019]

[Table 1]

[0020]

Industrial Applicability The insulating resin paste of the present invention has a high degree of thixotropicity, a good coating workability, no change over time during work, good productivity, excellent adhesion and moisture resistance, and an elastic modulus of a cured product. And can be used for bonding a semiconductor element such as an IC to an organic substrate such as a metal frame such as copper or 42 alloy, a ceramic substrate, glass, or epoxy. In particular, it is suitable for bonding large chips to a copper frame, and can prevent poor characteristics of ICs etc. due to the difference in the coefficient of thermal expansion between the copper frame and the silicon chip. It is a resin paste.

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H01B 3/40 H01B 3/40 Z H01L 21/52 H01L 21/52 E (56) References JP-A-4-356934 (JP, A) JP-A-61-261365 (JP, A) JP-A-4-275325 (JP, A) JP-A-4-185631 (JP, A) JP-A-62-105450 (JP, A) JP-A-5-59158 ( JP, A) JP-A-4-126714 (JP, A) JP-A-4-332754 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 63/00-63/10 C08L 9/00 C08K 3/36 C08K 9/06 C08G 59/56 H01L 21/52 H01B 3/40

Claims (1)

(57) [Claims] (A) The primary particles have an average particle size of 2 to 50 nm.
The ultrafine silica powder obtained by reacting at least 50% of the silanol groups on the surface with an organosilicon compound represented by the following formula (1) in a silica filler having an average particle size of 1 to 20 μm and a maximum particle size of 50 μm or less. A silica filler containing 10 to 50% by weight, (B) bisphenol F and a latent amine compound, (C) an epoxy resin liquid at room temperature and (D) a polybutadiene compound having an epoxy group are essential components, and the total composition is 10 to 30% by weight of silica filler (A), polybutadiene compound having epoxy group (D)
3 to 20% by weight of an insulating resin paste. Si (R) m (X) n (1) m + n = 4 R: methyl, ethyl, butyl, octyl group _{X: Cl, Br, OCH 3} , OH