Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – Of specified material other than copper
Reexamination Certificate
2007-05-08
2007-05-08
Malsawma, Lex (Department: 2823)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
Of specified material other than copper
Reexamination Certificate
active
10901844
ABSTRACT:
A packaged integrated circuit includes a die surrounded by an encapsulant in which leads are used to electrically connect the die, which is internal to the encapsulant, externally. The leads have a primary metal that is used for electrical conduction and physical support. The external portion of the lead is coated with another metal, typically tin, that is useful for soldering. This tin layer is formed in a manner that ensures that it is porous. Although porous is generally thought to be a bad characteristic, it turns out to be very effective in absorbing stress and thus retarding whisker growth. Whisker growth, which can short adjacent leads together as well as cause other deleterious effects, has been a major source of failures in packaged integrated circuits. An additional layer of very thin tin that is non-porous can be added before or after the porous tin layer has been deposited.
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Chopin Sheila F.
Su Peng
Vo Nhat D.
Chiu Joanna G.
Clingan, Jr. James L.
Freescale Semiconductor Inc.
Malsawma Lex
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