Semiconductor Lead Frame Thinned Region Creepage Distance
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Solution Overview
Problem
Packaged semiconductor devices struggle to meet the required creepage distance for high voltage isolation under worst-case dimensional conditions due to standard lead frame and package designs, which often result in inadequate separation between high voltage and low voltage leads.
Innovation Solution
The implementation of a lead frame with thinned regions that extend into the mold cavity, allowing mold extensions to form around the outer edges of leads, increasing the creepage distance by filling the space between leads with resin, thereby enhancing the separation between conductive parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard lead frame and package designs are used, then manufacturing is simpler and device structure is more compact, but creepage distance between high voltage and low voltage leads is insufficient under worst-case dimensional conditions
Solution Approach 1:
The patent applies local quality by creating thinned regions at specific locations on the lead frame where mold extensions are needed to increase creepage distance. Instead of modifying the entire lead frame uniformly, only specific areas are thinned to allow mold resin to extend and provide additional insulation distance between high voltage and low voltage leads, thereby resolving the contradiction between maintaining simple structure and achieving sufficient creepage distance.
2Reliability
If lead frame thickness is reduced to allow mold extensions, then creepage distance increases, but lead frame strength and structural integrity may be compromised
Solution Approach 1:
The lead frame is designed with thinned regions only at specific locations where mold extensions are required to increase creepage distance, while other regions maintain full thickness to preserve structural strength and integrity. This localized thinning approach allows the package to achieve sufficient insulation distance without compromising the overall strength of the lead frame.
Solution Approach 2:
The lead frame is segmented into different thickness regions - thinned regions where mold extensions are needed for creepage enhancement, and full-thickness regions where structural strength is critical. This segmentation allows simultaneous optimization of both creepage distance and mechanical strength by assigning different thickness properties to different functional areas of the lead frame.
Data Source
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AI summary
A packaged semiconductor device includes a die attached to a die flag of a lead frame wherein the die includes a first, second, third, and fourth minor side, wherein the first and second minor sides are opposite each other and the third and fourth minor sides are opposite each other. The device includes an outer-most lead of the lead frame extending outwardly from the first minor side of the die and closest to the third minor side, wherein the outer-most lead includes a thinned region located between the die and a full thickness portion of the outer-most lead. The device includes an electrical connection between the die and the outer-most lead, and an encapsulant surrounding the die, the electrical connection, and surrounding at least a portion of an outer edge of the thinned portion of the outer-most lead such that the full thickness portion of the outer-most lead extends beyond the encapsulant.