Deformation of Al metallization was observed during thermal shock tests of plastic encapsulated semiconductor devices. The authors made clear quantitatively the relations between the deformation length and Si chip size, distance from deformation center, molding resin, temperature difference in thermal shock etc. and tried to explain the mechanisms and the cause of this phenomenon. ntroduction Because of lower cost, plastic encapsulated semiconductor devices are widely adopted in lieu of hermetic devices, in spite of their shortcomings such as poor moisture resistance, poor resistance to thermal shock and the detrimental influence of impurities in molding resins. There presently exists a good deal of literature on thermal shock problems such as die attachment fatigue, die crack propagation, wire bond breakage and electrical parameter shifts. The only known reference to the thermal shock problem of an Al metallization is an article on a type of electromigration problem.1 There is also an abundance of published material on electromigration and Al corrosion due to water penetration, including the added influence of impurities in molding resins.This paper describes a newly discovered phenomenon resulting in Al metallization deformation in plastic encapsulated devices after thermal shock cycling. For present devices of good design, Al deformation of the type discussed may not cause any serious problems. However, if molding resins are used with the narrow line widths projected for the near future, this deformation problem may become critical.Al deformation was found, at first, in open or short failures after extended cycled thermal shock test. In order to fully understand the cause of this failure and its mechanism, we carried out experiments and succeeded to define the effects of chip sizes, molding resins, temperature differences and cycles of thermal shock, lead frame materials, overcoatings of IC chip, etc. on Al deformation lengths. At the same time, degradation of the adhesion between the silicon and molding resin proved to be the cause of the-Al deformation.An additional result of this study was a vivid illustration of shear stresses inside the IC chip.

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The memory retention life and its repeatability was examined under conditions of high temperature storage, temperature cycling, bias operating, and high humidity, and after write/erase cycles for MNMoOS EAROMs having short memory retention life.It is shown that the high temperature storage and humidity tests are representative of all these tests, retention life during humidity tests for PED's is generally shorter than the unrecoverable failure life, and SiN overcoating extends retention life remarkably.

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