Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Patent
1988-01-21
1989-05-30
McDowell, Robert
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
174 524, 204 40, 204 443, 204 445, 204 446, 204 461, 204 47, 204 475, 204 49, 357 74, 428680, 428926, 428935, B32B 1518
Patent
active
048350672
ABSTRACT:
To simplify manufacture of plated metal parts with high corrosion resistance especially suitable for use as sealing lids or cover elements for semiconductor packages, a substrate of Kovar, or Alloy 42, which are nickel-containing iron alloys, are electroplated with a base layer of a metal having an electromotive potential high with respect to that of the substrate, over which an intermediate layer is electroplated, which intermediate layer (16) has an electromotive potential which is low with respect to the base layer, and over that a cover layer (18) is plated which has an electromotive potential similar to that of the base layer. Suitable metals are gold-nickel-gold combinations, in which the gold layers should be over 10 microinches thick, preferably and in order to meet MIL-STD 883C, about 25 microinches thick. The intermediate layer (16), if of nickel, has an electromotive potential which is at the negative side of the electromotive series. Pin holes through the three layers may cause, under the influence of a corrosive atmosphere, migration of ions up to the base layer but, due to the arrangement of electromotive potentials of the intermediate and the cover layer, will not extend further so that the corroded substrate material will, effectively, form a plug for the pin hole and prevent progression of corrosion.
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patent: 4666796 (1987-05-01), Levine
Electro Alloys Corp.
McDowell Robert
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