Solderable metal finish for integrated circuit package leads and method for forming
US7215014B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 29, 2004 |
| Grant date | May 8, 2007 |
| Priority date | — |
| Expiry date | Aug 25, 2024 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01L2924/181
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.