The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 08, 2007
Filed:
Jul. 29, 2004
Peng Su, Austin, TX (US);
Sheila F. Chopin, Austin, TX (US);
Nhat D. Vo, Austin, TX (US);
Freescale Semiconductor, Inc., Austin, TX (US);
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.