Quad flat no-lead chip carrier with stand-off
US7405106B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | May 23, 2006 |
| Grant date | Jul 29, 2008 |
| Priority date | — |
| Expiry date | Oct 26, 2026 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02P70/50
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
A QFN package with improved joint solder thickness for improved second level attachment fatigue life. The copper leadframe of a QFN chip carrier is provided with rounded protrusions in both the chip attach pad region and the surrounding lead regions before second level attachment. The rounded stand-off protrusions are formed from the copper itself of the copper of the leadframe. This may be achieved by punching dimples into one surface of the copper plate of the leadframe before plating to form protrusions on the opposing surface. This method of forming the rounded protrusions simplifies the process of forming stand-offs. The protrusions provide a structure that increases wetting area and allows the use of a larger quantity of solder for increased solder joint thickness and better die paddle solder joint area coverage. As a result of the increased solder joint thickness, second level fatigue life is significantly improved. As a result of the improved die paddle solder joint area coverage, improved thermal performance of the chip carrier is also significantly improved.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.