JPH0515752B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an insulating resin paste used when die bonding a semiconductor element to a lead frame, a ceramic substrate, or the like. For more details, even if it is cured at high temperature and in a short time,
This invention relates to an insulating resin paste used in a resin bonding method that generates extremely few air bubbles. [Prior Art] Conventionally, methods for die-bonding semiconductor elements to lead frames etc. include the gold-silicon eutectic method, which involves bonding by forming a eutectic of gold and silicon;
Furthermore, a solder bonding method using solder paste has been mainly used. The gold-silicon eutectic method has drawbacks such as extremely high costs due to the use of gold, and high working temperatures of 400 to 450 degrees Celsius, which can lead to deterioration of semiconductor devices and parts. On the other hand, although the solder bonding method is relatively low cost, it has drawbacks such as poor heat resistance and deterioration of semiconductor elements due to solder ball scattering. Under these circumstances, resin bonding methods using conductive or insulating pastes in which inorganic powders such as silver powder and silica powder are dispersed in resin have recently come into use. This resin bonding method can significantly reduce costs, and in particular, those using silica powder as the insulating resin paste are inexpensive because they do not use any noble metals, and their properties are also very excellent. However, conventional insulating resin pastes used in these resin bonding methods have the disadvantage that bubbles are easily generated during curing. This requires dispersing inorganic powder such as silica powder into a resin and making it into a paste, so the resin must contain a large amount of solvent or be liquid at room temperature. When the insulating paste hardens, it partially evaporates and generates air bubbles, or when the resin and inorganic powder are kneaded, air is trapped and forms air bubbles. If these bubbles do not come out smoothly during curing, the bubbles may remain in the cured product, significantly reducing the adhesion strength between the semiconductor element and the lead frame, or the force when the bubbles come out may tilt the semiconductor chip.
This creates a serious drawback in that the parts are bonded at an angle, making it impossible for the automatic bonder to recognize the position during metal wire bonding in the post-process. [Object of the Invention] An object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide an insulating resin paste that can be firmly bonded to an external support electrode such as a lead frame without tilting a semiconductor element. The present inventors focused on the fact that small air bubbles generated when the paste hardens collide with each other and become larger by the time they reach the paste surface, and the force when these large air bubbles escape causes the semiconductor element to tilt. As a result of repeated investigations, we found that using amorphous silica powder particles with a large particle size shortens the path for the generated air bubbles to reach the surface, and that dicyandiamide and/or maleonitrile derivatives are latent. They found that when used as a hardening agent, the viscosity of the paste during hardening, combined with the effect of large-diameter silica powder particles, decreases significantly in the initial stage, making it easier for air bubbles to escape, and the objective was achieved. [Structure of the Invention] That is, the present invention comprises (A) an amorphous silica filler containing 15 to 50% by weight of amorphous silica powder having a particle size distribution of 20 to 50 μm, and (B) The present invention relates to an insulating resin paste for resin bonding, characterized in that (C) dicyandiamide and/or maleonitrile derivatives are used as a latent amine curing agent, and (C) an epoxy resin that is liquid at room temperature is an essential component. The amorphous silica powder particles used in the present invention have a particle size of
50μm or less, but this is because if the particle size is larger than this, when applying the paste with a dispenser, silica powder particles will gradually accumulate near the exit of the needle with a thin needle (diameter 0.2mm or less), and eventually This is because it blocks the outlet and makes it impossible to use it continuously for a long time. It is also believed that the bubbles generated in the paste during curing reach the paste surface by repeatedly colliding with the silica powder particles while traveling through the resin binder. In this case, in an insulation paste containing the same weight of silica powder, the number of silica powder particles decreases significantly as the particle size increases, so collisions between air bubbles and silica powder particles decrease, and as a result, air bubbles appear shorter and shorter. Since the bubbles pass through the path to the surface, collisions between bubbles and growth are also reduced. In the present invention, large silica powder, i.e., particle size
It is essential to contain 15% to 50% by weight of particles with a diameter of 20 to 50 μm, but if the amount is less than 15% by weight, the above-mentioned effect will not be sufficient and the bubbles will not come out smoothly. Further, if the content is 50% by weight or more, the thixotropy of the paste becomes small, causing problems such as dripping or bleeding of the paste from the dispenser, resulting in practical problems. Further, the present invention is characterized in that dicyandiamide and/or maleonitrile derivatives are used as latent amine curing agents. These curing agents have a particularly high curing temperature among the so-called latent curing agents, and hardly react at temperatures below 150°C, but the reaction rapidly progresses when the temperature exceeds 150°C. Therefore, if these curing agents are used, the reaction will hardly proceed up to 150°C, and only the temperature of the paste will rise, so the viscosity will drop rapidly and bubbles will come out very easily. The maleonitrile derivatives used in the present invention include, for example, diaminomaleonitrile, N-benzylmaleonitrile, N-
Examples include monoalkyl substituted derivatives such as isobutylmaleonitrile, and dialkyl derivatives such as N-benzyl-N'-benzylmaleonitrile and N-methyl-N'-benzylmaleonitrile. Further, the epoxy resin used in the present invention is limited to one that is liquid at room temperature, but if it is not liquid at room temperature, it will be necessary to use a solvent to knead it with silica powder and make it into a paste. These solvents vaporize during curing and cause bubble generation. In order to form a paste without using a solvent, it must be liquid at room temperature. Examples of the epoxy resin used in the present invention include bisphenol A,
Bisphenol F, a diglydyl ether obtained by the reaction of phenol novolac with epichlorohydrin, which is liquid at room temperature, such as alicyclic diepoxy adipate, alicyclic diepoxy carboxylate, and vinyl cyclohexene dioxide. alicyclic epoxy resin, furthermore n-butyl glycidyl ether, 2
- Monoepoxy resins such as ethylhexyl glycidyl ether, styrene oxide, phenyl glycidyl ether, cresyl glycidyl ether, and vinylcyclohexene monoepoxide. Furthermore, the amount of chlorine contained in the epoxy resin should be as small as possible, preferably 500 PPm or less. This is because if epoxy containing too much chlorine is used, chlorine ions extracted from the insulating resin paste will corrode the aluminum wiring on the surface of the semiconductor element. In the present invention, the content of the amorphous silica filler in the insulating resin paste is not particularly limited;
It is preferably 40 to 60% by weight, and a substance in this range is easiest to use when applying the paste using a dispenser, screen printing, stamping, etc. Furthermore, in the present invention, a curing accelerator,
Pigments, dyes, antifoaming agents, etc. can also be added. [Effects of the Invention] As described above, the insulating resin paste according to the present invention smoothly releases air bubbles during curing.
The tilting or peeling of the semiconductor element, which often occurs when the semiconductor element and the external electrode are bonded, is eliminated, and the reliability of the bond can be greatly improved. [Example] Example 1 Amorphous silica powder (hereinafter referred to as amorphous silica A) with a particle size distribution of 20 to 50 μm and an average particle size of 35 μm adjusted by setting, and amorphous silica with a particle size of 20 μm or less and an average particle size of 5 μm. Diglycidyl ether (epoxy equivalent
180) and dicyandiacid in the proportions shown in Table 1 and kneaded with a three-roll mill to obtain an insulating resin paste. This insulating resin paste is applied 2 times in a vacuum chamber.
After defoaming at mmHg for 30 minutes, it was applied onto a lead frame using a dispenser, and a semiconductor element with a size of 3 x 3 mm square was mounted. Thereafter, the semiconductor element was placed on a heating plate at 300° C. for 60 seconds to cure, and the inclination of the semiconductor element, the number of peelings, and the occurrence of bubbles were examined, and the volume resistivity was also measured. In addition, the paste was applied on the lead frame, left for 30 minutes, and the state of bleed was examined. The results are shown in Table 1. Example 2 Insulating resin pastes having the compositions shown in Table 1 were prepared and tested in exactly the same manner as in Example 1, except that diaminomaleonitrile was used as a curing agent. The results are shown in Table 1. Example 3 An insulating resin paste having the composition shown in Table 1 was prepared and tested in exactly the same manner as in Example 1 except that N-isobutylmaleonitrile was used as a curing agent. The results are shown in Table 1. Example 4 An insulating resin paste having the composition shown in Table 1 was prepared in exactly the same manner as in Example 1, except that glycidyl ether (epoxy equivalent: 170) derived from phenol novolak and epichlorohydrin was used as the liquid epoxy resin. I conducted a test. The results are shown in Table 1. Comparative Example 1 A non-latent curing agent. Insulating resin pastes having the compositions shown in Table 1 were prepared and tested in exactly the same manner as in Example 1, except for using diaminodiphenylmethane. The results are shown in Table 1. Comparative Example 2 An insulating resin paste having the composition shown in Table 1 was prepared and tested in exactly the same manner as in Example 1, except that the proportion of amorphous silica A was very small. The results are shown in Table 1. Comparative Example 3 An insulating resin paste having the composition shown in Table 1 was prepared and tested in exactly the same manner as in Example 1, except that the proportion of amorphous silica B was very small. The results are shown in Table 1. Comparative Example 4 Same as Example 1 except that a solution of solid glycidyl ether (epoxy equivalent: 480) obtained by the reaction of bisphenol A and epichlorohydrin dissolved in methyl isobutyl ketone at a concentration of 60% by weight was used as the epoxy resin. Insulating resin pastes having the compositions shown in Table 1 were made in exactly the same manner and tested. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1 (A) Amorphous silica powder with a particle size of 50 μm or less,
Those with a particle size distribution of 20 to 50 μm are 15 to 50
% by weight of amorphous silica filler. (B) Dicyandiamide and/or maleonitrile derivatives. (C) An insulating resin paste characterized by containing as an essential component an epoxy resin that is liquid at room temperature. 2 Content of amorphous silica filler is 40-60% by weight
The insulating resin paste according to claim 1, characterized in that: 3. The insulating resin paste according to claim 1, characterized in that the epoxy resin contains 500 ppm or less of chlorine in the epoxy resin that is liquid at room temperature.