Split Tie Bar Structure to Prevent Clip Bending Shorts
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Solution Overview
Problem
During the assembly of semiconductor power packages, the bending of tie bars can lead to device terminal shorting and leakage, reducing the test yield of power device packages due to stresses induced by assembly processes.
Innovation Solution
The introduction of 'dummy tie bars' positioned adjacent to conventional tie bars within the saw street region provides additional mechanical support, acting as spacers to prevent downward bending and deformation of the tie bars, thereby eliminating the risk of shorts and leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If tie bars are used to hold clips in precise position during batch assembly, then manufacturing precision is improved, but the tie bars are susceptible to bending and deformation under assembly stresses, reducing reliability
Solution Approach 1:
The tie bar is segmented into two functional parts: a first tie bar that provides mechanical support and positioning, and a second tie bar that reinforces structural stability. This segmentation allows each part to be optimized for its specific function while working together to solve the contradiction between precision positioning and structural stability.
Solution Approach 2:
The second tie bar acts as an intermediary reinforcement element that mediates between the assembly stresses and the first tie bar. It provides additional support that prevents bending and deformation, thereby maintaining the reliability of the tie bar system while preserving the precision positioning capability.
2Reliability
If dummy tie bars are added to provide additional mechanical support, then reliability is improved, but device complexity increases due to additional components
Solution Approach 1:
The second tie bar is made from the same material and has a similar structure to the first tie bar, maintaining homogeneity in the tie bar system. This approach improves reliability through additional support while minimizing the increase in device complexity by using identical or similar components rather than introducing fundamentally different structural elements.
Data Source
AI summary
A gang clip includes a plurality of clips formed from a metal each having a center region oriented along a first plane and an angled clip foot having a foot height, a length and a bend angle sufficient to electrically contact a lead terminal of the leadframe to be used to form a device. Adjacent ones of the plurality of clips are joined to one another by a first tie bar also oriented along the first plane. The first tie bar extends to a saw street region located between adjacent ones of the clips. A second tie bar attached to the first tie bar is positioned in the saw street region.