Pre-Plated Lead Tips for Wettable Flank Solder Stability
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Solution Overview
Problem
During the manufacturing of semiconductor packages, the lead tips are often cut off from the leadframe, resulting in exposed copper tips without plating, which causes instability in solder wetness during automated optical inspection and surface mount technology processes.
Innovation Solution
A method of forming semiconductor packages with pre-plated lead tips by designing a leadframe that allows for cutting the leadframe strip without cutting the lead tips, ensuring full plating coverage on the lead tips through strategically placed openings and cuts that maintain plating during singulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lead tips are cut from the leadframe during manufacturing, then the leads can be separated for packaging, but the plating on the lead tips is removed exposing copper
Solution Approach 1:
The lead tips are pre-plated with solder mask or conformal coating before the cutting process. This preliminary protective action ensures that when the leads are subsequently cut from the leadframe, the plating on the exposed tip surfaces is already protected, preventing copper exposure and maintaining solder wetness stability during later SMT processes.
2Reliability
If the leads are wettable flank leads requiring plating on the tip, then solder fillet stability is improved, but automated optical inspection becomes difficult without plating on cut surfaces
Solution Approach 1:
The lead tips are pre-plated with a protective coating before cutting. This ensures that after separation, the exposed tip surfaces maintain their plating layer, providing both stable solder fillet formation and proper reflectivity for automated optical inspection systems to detect solder wetness accurately.
Data Source
AI summary
A method for making a semiconductor device is provided. The method generally includes forming a package having a first plurality of leads extending from a first side of the package, the package disposed on a leadframe. The method generally includes making a first cut adjacent to a first side of a first lead of the first plurality of leads, the first side extending from the first side of the package. The method generally includes making a second cut adjacent to a second side of the first lead of the first plurality of the lead, the second side of the lead opposite the first side of the lead and extending from the first side of the package.