CS215853B1 - A method of increasing the reliability of a semiconductor component encapsulated or embedded in plastic - Google Patents

Abstract

The invention relates to the encapsulation of semiconductors in plastic materials and solves the problem of increasing the tightness of plastic housings. The essence of the invention is the use of alkylhydrogenpolysiloxane of the general formula R^-Si-O-/RH-Si-Ot(?;—-— —/ Rg-Si-O^- Si R^j where R is methyl or ethyl and m = 10+2000 or n = 0*2000, as an impregnating varnish for vacuum impregnation of semiconductor element housings at a pressure of 0.66 to 13.33 kPa for a minimum of 30 seconds. The varnish is then cured for e.g. 3 hours at 160 °C. The aim of this operation is primarily to seal joints and gaps between the plastic and electrodes or cooling surfaces of components. To reduce the curing temperature and curing time, a catalyst from the group of substances including organometallic salts or organometallic compounds of certain metals can be used, e.g. cobalt naphthenate, iron naphthenate, zinc octoate, tin octoate, etc.

Description

The invention relates to a method of increasing the reliability of encapsulation of a semiconductor component in a tray, particularly in a humid environment.

The main reason for the increasing use of plastics in the field of encapsulation of semiconductor devices is primarily economic. Plastics, which have already dominated the consumer industry in the past, are now beginning to penetrate the industrial and military applications of electrical engineering and electronics. This penetration of plastics is related to the ever-increasing reliability of plastic housings, which has so far been a major disadvantage and a limiting factor for use in power applications or military technology.

Greater reliability was achieved both by improving the purity of the materials used, ie by reducing the content of free ions in the material, which in conjunction with moisture are the cause of electrochemical corrosion and especially alkaline ions and adversely affect the semiconductor transition diodes, thyristors, transistors and the like. Furthermore, the glass transition temperature T of the masonry materials was increased, that is, the temperature at which the linear expansion changes linearly. The sharp increase in linear expansion at temperature T results in the loss of the part and the formation of amyloc

On stresses in joints, solder, etc., which can lead to short or permanent damage to the component. For example, by introducing epoxy novolaks, the temperature T increased from the current 115 and 125 ° C for palm epoxy resins to 145 and 165 ° C, respectively. In addition to improving the cleanliness of the sheaths themselves, the cleanliness and quality of the hole and electron conductivity passivation coatings have also improved. In the past few years, I have been melting special borosilicate glass on a semiconductor transition intended for encapsulation in a wage. The introduction of epoxy novolaks also improved the adhesion of the encapsulating materials and thus the reliability of the components in the tray. The new silicone and epoxy silicone compositions have also made clear progress in this area.

It is a well-known fact that moisture penetrates into the housing by the plastic itself, which is never impermeable to moisture, on the one hand along the outlets themselves. If the adhesion of the mass is not high, or if it is reduced due to temperature cycling during testing or operation, the control of moisture penetration is the vapor permeability along the metal outlets. One process to improve the reliability of the salary component is to additionally impregnate the housing with a low viscosity lacquer that seals the joint along the component outlets. Low viscosity, usually silicone impregnating lacquers specially formulated for this purpose are usually used for this purpose, usually methylsiloxane or methylphenylsiloxane lacquers, the disadvantage of which is the high curing temperature, generally 200 ° C or higher, which in some cases is unsuitable with regard to solders or even housing material used, or modified siloxanes are used, for example modifiers may be. alkyds, acrylates, phenoplasts, epoxides, etc., which cure at lower and therefore more acceptable temperatures *

The above drawbacks, i.e. the high curing temperature of the impregnating lacquers, are eliminated by the method of increasing the reliability of the encapsulated semiconductor component according to the invention, which consists in immersing the semiconductor component in a casting or molded plastic casing in an alkylhydrogenpolysiloxane

215 853

R

R - Si I

R

Si

Si

where R = CH or CH _c 3 2 5 m = 10 * 2000 n = 0, ♦ 2000 at a pressure of 0,66 to 13,33 kPa for a minimum of 30 s and rinsed or wiped with an aliphatic or aromatic solvent after this bath » dried the solvent residues and cured the deposited alkyl hydrogen polysiloxane.

Alkylhydrogenpolysiloxane is curable, for example, at a temperature of 160 DEG C., with the use of catalysts, naphthenates and octoates of zinc, lead, tin, iron, etc., curing can be reduced up to 120 DEG C. or 20 DEG C. can be added with organic titanium compounds.

Example

The potential-free semiconductor module encapsulated in an epoxy resin is immersed in methyl hydrogen polysiloxane at 5 kPa for 30 seconds. After removing the vacuum and removing the part from the bath, the part is immersed in perchlorethylene for 5 seconds. After evaporation of the solvent in air, the coating was cured at 160 ° C for 3 hours. The resulting coating is flexible and, unlike unmodified methylsiloxanes and methylphenylsiloxanes, retains its function even at temperature shocks.

The semiconductor module impregnated as described above is embedded in an acid galvanic tin bath containing 20% by weight of concentrated sulfuric acid < RTI ID = 0.0 > H2SO4 < / RTI > for 10 minutes at 25 ° C. The impregnated modules are always the same without exception, but the unimpregnated components are 100% unstable. Similarly, 100% stable parts are impregnated under the same conditions with methyl hydrogen polysiloxane with the addition of 10 parts by weight of lead naphthenate when the impregnating varnish is first cured for 30 minutes at 120 ° C after application.

Claims (2)

THE FIELD OF THE INVENTION Method for increasing the encapsulation reliability of a plastic molded or embedded semiconductor device, characterized in that a semiconductor device is immersed in an alkyl hydrogen polysiloxane of the general formula wherein R = CH 2 - or ^C 2 ^H 5 - m = 10 + 2000, n · = 0 ♦ 2000 at a pressure of 0.66 to 13.33 kPa for a minimum of 30 seconds and after removal, it is cleaned with an aliphatic or aromatic solvent, dried with solvent residues and then cured 215 853 alkylhydrogen polysiloxane. 2. A method of increasing the encapsulation reliability of a semiconductor device according to claim 1, wherein the catalyst is selected from the group consisting of organometallic salts or organometallic compounds of certain metals such as tin, lead, titanium, chromium, zinc, cobalt, calcium, and the like. magnesium. Printed by Moravian Printing Works, plant 12, Leninova 21, Olomouc