Corner Lead Package Carrier for Solder Fatigue Resistance
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Solution Overview
Problem
Existing leadless packages face challenges in thermo-mechanical robustness, particularly during thermal cycling tests, due to solder fatigue failure at corner leads.
Innovation Solution
A carrier for a leadless package is designed with corner leads that have a larger width along the component mounting structure's edge compared to intermediate leads, and these corner leads incorporate a lead tip inspection feature to enhance solder wetting and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If corner leads have larger width compared to intermediate leads, then solder joint reliability is improved, but package area increases
Solution Approach 1:
The patent applies local quality by differentiating the width of corner leads from intermediate leads. Specifically, corner leads are designed with a larger width to enhance solder joint reliability and suppress fatigue failure, while intermediate leads maintain a smaller width to minimize package area. This localized differentiation optimizes the structure where it is most needed without unnecessarily increasing overall package size.
2Reliability
If corner leads are positioned closer to corners of component mounting structure, then thermo-mechanical robustness is improved, but lead layout complexity increases
Solution Approach 1:
The patent employs asymmetry in the lead layout by positioning corner leads closer to the corners of the component mounting structure than intermediate leads. This asymmetric arrangement optimizes thermo-mechanical robustness by providing better support at the corners where stress concentration occurs during thermal cycling, while the systematic placement follows a predictable pattern that manages layout complexity.
3Manufacturing precision
If lead tip inspection feature is added to corner leads, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent implements preliminary action by incorporating a lead tip inspection feature directly into the corner leads during manufacturing. This feature, such as a protrusion or specific geometric configuration at the lead tip, enables inspection of lead tip integrity and solder wetting before final assembly. By building this inspection capability into the lead structure itself during fabrication, the patent achieves manufacturing precision without requiring separate external inspection mechanisms.
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 significantly improves the second-level solder joint thermal cycle on board (TCoB) test performance by suppressing solder fatigue failure at corner leads, while maintaining a small form factor and compliance with package specifications.
Implementation Method 1
these corner leads incorporate a lead tip inspection feature to enhance solder wetting and reliability
Data Source
AI summary
A carrier for a leadless package is disclosed. In one example, the carrier comprises a component mounting structure for mounting an electronic component thereon, and a plurality of leads arranged around at least part of the component mounting structure, wherein corner leads of said leads are located closer to at least one corner of said component mounting structure than intermediate leads of said leads located farther away from said at least one corner than said corner leads, wherein said corner leads have a larger width along a respective edge of the component mounting structure compared with a smaller width of said intermediate leads, and wherein at least said corner leads comprise a lead tip inspection feature.