Wire Bond Continuity Testing During Bond Formation
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Solution Overview
Problem
Existing wire bond formation processes fail to effectively detect improperly or poorly formed electrical interconnections, leading to unwanted electrical resistance and functionality issues in electrical device assemblies.
Innovation Solution
A wire bonding apparatus equipped with a supply of bond wire, a wire bonding head, and an electrical continuity tester, which includes a wire cutter, allows for in-process resistance measurements to determine the success or failure of wire bonds by comparing measured resistance to threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonds are tested after the capillary is released from the bonding head, then the capillary remains available for bonding, but defective bonds cannot be detected until after bonding occurs, leading to potential reliability issues
Solution Approach 1:
The patent implements preliminary testing of the wire bond immediately after formation but before the capillary is released from the bonding head. The testing apparatus is positioned to access the bond site during the bonding cycle, allowing the bond to be tested while still attached to the bonding head. This preliminary action enables defective bonds to be detected and flagged before the capillary becomes unavailable, resolving the contradiction by prioritizing reliability detection without sacrificing bonding availability.
2Reliability
If the testing apparatus is positioned to access bonds during the bonding cycle, then in-process testing can occur, but the bonding head design becomes more complex with additional positioning requirements
Solution Approach 1:
The patent merges the testing apparatus with the bonding head assembly, integrating the testing functionality directly into the existing bonding head structure. The testing apparatus shares the bonding head's positioning and movement mechanisms, eliminating the need for separate complex positioning systems. This integration achieves in-process testing capability while minimizing additional complexity by combining functions rather than adding independent systems.
3Measurement precision
If multiple bonds are tested sequentially one at a time, then each bond can be individually evaluated, but the testing process becomes time-consuming and reduces productivity
Solution Approach 1:
The patent implements partial parallel testing where multiple bonds are tested simultaneously using multiple testing tips or sensors that can evaluate several bonds in a single operation. This approach maintains individual bond measurement precision by providing dedicated sensing elements for each bond while achieving parallel execution to improve productivity. The system performs excessive testing capacity (testing more bonds at once than strictly necessary) to ensure complete coverage while reducing overall testing time.
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~3D
AI summary
In a general aspect, a wire bonding apparatus can include a supply of bond wire (309), a wire bonding head (310), and an electrical continuity tester (320). The wire bonding head (310) includes a wire cutter. (312) The wire cutter is electrically conductive. The electrical continuity tester is coupled between the supply of bond wire and the wire cutter.