Leadframe Thin-Section Layout for Resin Crack Resistance
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Solution Overview
Problem
Existing semiconductor devices sealed with resin are prone to cracks under external forces due to inadequate resin fill volume and thermal expansion mismatch between the leadframe and semiconductor element, leading to potential shorts and reduced reliability.
Innovation Solution
A leadframe design with a thin plate portion in the bed portion and a second thin plate portion in the lead portion, combined with a manufacturing method that includes fixing the leadframe components to suppress bending stress and ensure resin coverage, enhances the resin fill volume and reduces the risk of cracks and electrode shorts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the leadframe structure is designed with thick sections to provide strength, then the structural strength is improved, but the resin fill volume is reduced and thermal expansion mismatch increases
Solution Approach 1:
The leadframe employs varying thickness in different sections: thin sections (5-15 μm) in the bed and lead portions to reduce thermal expansion mismatch and allow adequate resin fill, while thick sections (20-50 μm) in support portions to maintain structural strength. This local differentiation resolves the contradiction between strength and reliability.
Solution Approach 2:
The leadframe uses a composite structure combining regions of different thicknesses and potentially different material properties to simultaneously achieve areas requiring high strength (support portions) and areas requiring low thermal expansion mismatch (bed and lead portions), resolving the contradiction between structural strength and crack resistance.
2Reliability
If the resin fill volume is increased to improve reliability, then crack resistance is improved, but the device complexity increases
Solution Approach 1:
By creating thin sections in specific areas of the leadframe, the design enables adequate resin fill volume in those localized regions without requiring complex overall structural changes. The thin sections allow resin to fully penetrate and seal critical areas, improving reliability through a relatively simple geometric modification.
3Reliability
If the leadframe sections are made thin to reduce thermal expansion mismatch, then the thermal stress-induced distortions are reduced, but the structural strength is reduced
Solution Approach 1:
The leadframe design applies thin sections (5-15 μm) specifically in the bed and lead portions where thermal expansion mismatch causes problems, while maintaining thick sections (20-50 μm) in support portions where structural strength is critical. This spatial differentiation allows simultaneous optimization of both thermal stress resistance and structural strength.
Solution Approach 2:
The leadframe is segmented into functional zones with different thickness characteristics: thin-bed portions for thermal compatibility, thick-support portions for mechanical strength, and intermediate lead portions. This segmentation allows each zone to be optimized for its specific function, resolving the contradiction between thermal stress resistance and structural strength.
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 proposed design effectively suppresses resin deformation and crack occurrence under external forces, improving the reliability and breakdown voltage of semiconductor devices by ensuring a larger resin fill volume and reducing thermal stress-induced distortions.
Implementation Method 1
thermal expansion mismatch between the leadframe and semiconductor element
Data Source
AI summary
A leadframe includes a first frame part and a second frame part. The first frame part includes a bed portion including a first section being thin in a first direction, a first support portion, a first lead portion positioned between the bed portion and the first support portion in a second direction, the first lead portion being connected with the bed portion and the first support portion, a first extension portion being connected to the bed portion, and a second extension portion separated from the first extension portion in a third direction and connected to the bed portion. The second frame part includes a second support portion connected to the first and second extension portions, and a second lead portion connected to the second support portion.