Lead Frame Recess Structure for Bonding Material Containment
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Solution Overview
Problem
The existing methods for forming lead frames with a structure that prevents bonding material from flowing out during semiconductor device assembly are complex, increasing the number of steps in the manufacturing process, and may result in reliability issues if the bonding material does not remain contained.
Innovation Solution
A lead frame design featuring a die pad with a recess, protrusions, and a concavity on its bottom surface, formed through etching, which accommodates excess bonding material and improves adhesion, thereby preventing material overflow without complicating the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a groove is formed around the bonding area to prevent bonding material from flowing out, then the bonding material containment is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent combines the bonding prevention function with the existing die pad structure by forming a recess directly on the die pad surface. This integration eliminates the need for separate bonding prevention structures, thereby maintaining reliability while reducing manufacturing process complexity.
Solution Approach 2:
The recess is formed on the die pad before the semiconductor element is mounted. This preliminary formation of the bonding prevention structure ensures that when bonding material is applied, it is already contained within the recess, preventing overflow without requiring additional processing steps after element placement.
2Reliability
If a groove structure is added to prevent bonding material overflow, then the bonding reliability is improved, but the number of manufacturing steps increases
Solution Approach 1:
The recess structure is integrated into the die pad itself, combining the bonding prevention function with the existing mounting structure. This merger allows the bonding reliability to be improved without adding separate manufacturing steps, thereby maintaining productivity.
3Reliability
If bonding material is contained within the bonding area, then wire bonding reliability is improved, but the manufacturing process becomes more complex
Solution Approach 1:
The recess is formed in advance on the die pad before the semiconductor element is mounted and before wire bonding occurs. This preliminary action ensures that bonding material is contained within the recess, preventing it from interfering with wire bonding operations, thereby improving wire bonding reliability without complicating the overall forming process.
Data Source
AI summary
A lead frame includes: a die pad having a mounting surface for a semiconductor element; a recess included on the mounting surface; and a lead disposed around the die pad. The recess includes: a bottom surface positioned at a depth less than a thickness of the die pad from an opening plane of the recess; a plurality of protrusions protruding from the bottom surface; and a concavity recessed from the bottom surface.