发明申请
- 专利标题: QUAD FLAT NO-LEAD CHIP CARRIER WITH STAND-OFF
- 专利标题(中): QUAD平面无铅芯片携带器
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申请号: US12115051申请日: 2008-05-05
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公开(公告)号: US20080203546A1公开(公告)日: 2008-08-28
- 发明人: John J. Maloney , Robert M. Smith , Charles H. Wilson
- 申请人: John J. Maloney , Robert M. Smith , Charles H. Wilson
- 申请人地址: US NY Armonk
- 专利权人: International Business Machines Corporation
- 当前专利权人: International Business Machines Corporation
- 当前专利权人地址: US NY Armonk
- 主分类号: H01L23/495
- IPC分类号: H01L23/495 ; H01L21/56
摘要:
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.
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