QFN Lead Etching for Reduced Shorting
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Solution Overview
Problem
The IC packaging industry faces challenges in achieving higher lead density without causing lead-to-lead shorting and electrical cross-talk due to the increasingly finer pitch requirements in quad flat non-leaded (QFN) packaging, which limits the size reduction and efficiency of electronic devices.
Innovation Solution
The solution involves forming leads with a predetermined thickness and interval gap, and employing half-etching or partial half-etching techniques to create etched lead-to-lead gaps that exceed the predetermined interval gap, thereby increasing the distance between leads and reducing the incidence of lead-to-lead shorting by up to 35%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pitch between leads is reduced to increase lead density, then the number of I/O terminals is increased, but lead-to-lead shorting and electrical cross-talk occur
Solution Approach 1:
The patent applies local quality by creating an etched gap specifically at the second terminal ends of alternating leads where they are disposed along the periphery of the package. This localized modification increases the gap distance only at critical locations where leads are closest together, preventing shorting without affecting the overall fine pitch design. The etched gap creates a non-uniform structure with different gap sizes at different locations along the leads.
2Area of stationary object
If the package size is reduced to meet shrinking device demands, then the footprint is minimized, but the pitch between leads becomes increasingly fine causing shorting
Solution Approach 1:
The patent segments the lead structure by creating alternating leads with different configurations. Specifically, the second terminal ends of alternating leads are etched to form gaps, while other leads remain unetched. This segmentation allows the package to maintain a fine overall pitch while introducing localized gap variations that prevent shorting between adjacent leads.
3Quantity of substance
If the lead pitch is reduced to increase I/O terminals, then more power can be provided to electronic devices, but electrical cross-talk increases
Solution Approach 1:
The etched gap creates a local quality modification at specific locations along the leads, particularly at the periphery where leads are disposed. This localized gap increase provides electrical isolation between adjacent leads without requiring a reduction in the overall number of I/O terminals, thereby maintaining high lead density while reducing cross-talk.
Data Source
AI summary
An integrated circuit package system is provided including: forming a plurality of leads with a predetermined thickness and a predetermined interval gap between each of the plurality of leads; configuring each one of the plurality of leads to include first terminal ends disposed adjacent an integrated circuit and second terminal ends disposed along a periphery of a package; and forming the second terminal ends of alternating leads disposed along the periphery of the package to form an etched lead-to-lead gap in excess of the predetermined interval gap.