Ultra-thin noble metal coatings for electronic packaging

Details Ultra-thin noble metal coatings for electronic packaging Ultra-thin noble metal coatings for electronic packaging

1995-06-26

1997-10-07

Thomas, Tom

Active solid-state devices (e.g., transistors, solid-state diode

Lead frame

257736, 257762, H01L 23495

Patent

active

056751770

ABSTRACT:
A lead frame comprising an ultra-thin composite of noble metal layers on a nickel surface is disclosed. The composite ranges from 2.5 to 11 microinches in thickness and includes in succession from nickel, a 0.5 to 3.5 microinches of palladium or gold strike, a 0.5 to 5 microinches thick palladium-nickel alloy layer having 10 to 90 weight percent nickel by weight of the alloy, a 0.5 to 5 microinches thick palladium layer, and a 0 to 1 microinch thick gold layer. The gold layer is being used whenever it is desirable to achieve high speed of solder wetting, relative to the speed of solder wetting of palladium. Viable ultra-thin coatings are most effectively obtained by deposition of the layers in a reel-to-reel metal deposition process.

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patent: 5178745 (1993-01-01), Abys et al.
patent: 5360991 (1994-11-01), Abys et al.
Frank H. Reed and William Goldie, "Gold Plated Technology", Electrochemical Publications Limited, 8 Barnes Street, Ayr, Scotland, 3rd Printing, 1987, pp. 26 and 46.
"Solderability", MIL-STD-883C, Notice 5, Method 2003.5, May 29, 1987.
"Standard Test Method for Porosity in Gold and Palladium Coatings by Sulfurous Acid/Vapor", ASTM Designation B799-88, Nov. 1988, pp. 463-465.

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