Power Leadframe Package With Fully Solder-Wettable Sidewalls
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Solution Overview
Problem
Existing power leadframe packages do not have fully solder wettable sidewall surfaces, which affects the reliability and performance of solder joints.
Innovation Solution
A manufacturing process involving a leadframe with metal clips and a specific cutting and plating method to ensure that the sidewalls of the lead and die pad regions are fully covered by a conductive layer, enabling full solder wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cutting process is used to separate lead regions, then manufacturing simplicity is maintained, but the sidewalls of the lead and die pad regions remain exposed and non-wettable to solder
Solution Approach 1:
The patent applies preliminary action by performing the first cutting operation to expose the sidewalls of the lead and die pad regions before the plating process. This ensures that the sidewalls are properly exposed and prepared for subsequent plating, allowing the conductive layer to be deposited on all surfaces that will contact solder, thereby achieving full solder wettability.
Solution Approach 2:
The patent segments the cutting process into two distinct operations: a first cutting operation that exposes the sidewalls of the lead and die pad regions, and a second cutting operation that separates the bridge portion. This segmentation allows each cutting operation to serve a specific purpose, ensuring proper sidewall exposure for plating while maintaining manufacturing feasibility.
2Reliability
If the bridge portion of the metal clip is not severed, then electrical connectivity is maintained during plating, but the plating process cannot be completed on all surfaces
Solution Approach 1:
The patent performs the first cutting operation to expose the sidewalls before plating, while the bridge portion remains intact to maintain electrical connectivity during the plating process. After plating is completed on all exposed surfaces, the second cutting operation severs the bridge portion. This sequence ensures both complete plating coverage and maintained electrical connectivity throughout the critical plating phase.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in fully solder wettable sidewalls, enhancing solder joint strength, supporting automated inspection, and reducing plating costs while improving lead anchoring and electrical connectivity.
Implementation Method 1
plating a conductive layer on full sidewalls of the lead region and die pad region exposed by the first operation to cut
Data Source
Figure 1A~1D
Figure 1E~1H
Figure 1I~3B
AI summary
An etched leadframe includes separated frame portions, where each frame portion includes an intermediate region interposed between lead and die pad regions. An integrated circuit die is mounted to each die pad region. A clip is mounted to each integrated circuit die, wherein the clip includes a lead mounting portion mounted to the lead region of an adjacent frame portion and a bridge portion extending over the intermediate region of the adjacent frame portion and mounted to the die pad region of the adjacent frame portion. A first cut made through the frame portion of each etched leadframe at the intermediate region separates the lead and die pad regions without severing the bridge portion of each clip. A conductive layer is plated on full sidewalls of the lead and die pad regions exposed by the first cut. A second cut is then made through the bridge portion of each clip.