Pre-Molded Leadframe Wettable Flanks for Precise Singulation
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Solution Overview
Problem
Current semiconductor manufacturing processes using pre-molded leadframes result in irregularly shaped wettable flanks and less precise singulation due to imperfections in the etching steps, leading to difficulties in soldering and device separation.
Innovation Solution
Modifying the etching process to achieve a flatter and more regular surface on connecting bars by forming the connection formations with an initial full thickness, then reducing it uniformly to create exposed wettable flanks, eliminating surface irregularities and material accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional two-step etching process is used, then wettable flanks are formed, but surface irregularities and material accumulation occur on connecting bars
Solution Approach 1:
The patent changes the etching parameters by using a single etching step with controlled depth to reach approximately the middle of the connecting bar thickness, rather than conventional two-step etching. This parameter change eliminates surface irregularities and material accumulation while still forming wettable flanks on the leadframe terminals.
2Strength
If connecting bars are present with full thickness, then structural support is maintained, but singulation precision is reduced due to irregular surfaces
Solution Approach 1:
The patent applies partial etching action by etching the connecting bars to only approximately half their full thickness, rather than removing them completely or leaving them at full thickness. This partial removal maintains sufficient structural support while creating a flat, regular surface that enables precise singulation.
3Quantity of substance
If irregular surfaces are present on connecting bars, then material accumulation occurs, but soldering quality is compromised
Solution Approach 1:
The patent changes the etching depth parameter to reach approximately the middle of the connecting bar thickness, which eliminates material accumulation and creates uniform surfaces. This uniformity ensures proper solder wetting and high-quality solder joints without the defects caused by irregular surfaces.
Data Source
AI summary
Electrically insulating material such as an epoxy resin is molded onto a sculptured, electrically conductive leadframe structure comprising a pattern of electrically conductive formations. The electrically insulating material penetrates into spaces between electrically conductive formations in the pattern of electrically conductive formations to provide a pre-molded leadframe structure configured to have at least one semiconductor die arranged thereon. The pre-molded leadframe structure has opposed first and second surfaces and a pre-molded leadframe thickness between the first surface and the second surface. The sculptured, electrically conductive leadframe structure comprises one or more connection formations connected with electrically conductive formations in the pattern of electrically conductive formations. The connection formation or formations have a first thickness equal to the thickness between the first surface and the second surface. The thickness of the connection formation or formations is reduced from the first thickness to a second, reduced uniform thickness with exposed wettable flanks formed in the electrically conductive formations facing the connection formation or formations with reduced thickness.