Staggered Recessed Lead Frame for Semiconductor Device
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Solution Overview
Problem
Conventional semiconductor package devices face issues with burr formation during the singulation process, which can lead to device failure due to shorting between adjacent leads, especially as the density of input/output (IO) increases and the pitch between leads becomes smaller.
Innovation Solution
A lead frame design with recessed portions on the top and bottom surfaces of selected leads, arranged in a staggered pattern to increase the distance between exposed lead surfaces, thereby positioning them outside the burr formation zone, reducing the risk of burr formation and shorting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pitch between adjacent leads is reduced to increase IO density, then the productivity and integration of the semiconductor device is improved, but the risk of burr formation and shorting between leads increases
Solution Approach 1:
The patent applies local quality by creating recessed portions at specific locations where burr formation is most likely to occur during singulation. Instead of uniformly modifying all leads, the recesses are strategically placed at the ends of leads that will be closest to adjacent leads after cutting, thereby locally addressing the burr problem without affecting overall lead density or electrical performance.
Solution Approach 2:
The recessed portions are formed in advance during lead frame fabrication, before the singulation process. This preliminary action pre-positioned the leads such that when burrs form during cutting, they are contained within the recessed areas and cannot bridge to adjacent leads, thus preventing shorting before it can occur.
2Reliability
If recessed portions are added to leads to prevent burr formation, then the reliability is improved, but the device complexity and manufacturing steps increase
Solution Approach 1:
The patent modifies the geometric parameters of the leads by introducing recessed portions with specific dimensions. The depth and width of these recesses are carefully controlled to be sufficient to contain burrs but not so large as to significantly weaken the leads or complicate the manufacturing process. This parameter-based approach balances reliability improvement with manufacturing simplicity.
3Manufacturing precision
If recessed portions are created on lead surfaces, then the manufacturing precision of lead positioning is improved, but the ease of manufacture decreases due to additional processing steps
Solution Approach 1:
The lead frame manufacturing process is segmented into distinct stages: first forming the basic lead structure, then adding recessed portions through separate machining or etching operations. This segmentation allows each processing step to be optimized independently, with the recesses being added only where needed rather than requiring complete rework of the entire lead frame manufacturing process.
Data Source
AI summary
A lead frame for reducing detrimental effects of burr formation includes a lead frame that has leads where a portion of a top surface is removed from a first lead and a portion of a bottom surface is removed from a second lead adjacent to the first lead to reduce spacing between leads while reducing the detrimental effects of burr formation, such as shorting and the like, caused during singulation of a semiconductor device manufactured with the lead frame.