Publication: Study on effect of surface roughness of no tie bar (ntb) lead frame to mitigate delamination in small outline integrated chip (soic) packaging
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Date
2025-09-01
Authors
Thanigesh, Thiyagu
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Abstract
The widespread application of SOIC as digital isolators in various domains has raised high interest by the industrial key players. Due to constant drive for faster data rates, better performance and high operation rate, SOIC digital isolators are commonly subjected to higher mechanical and thermal stress in long term application which leads to delamination issue. Delamination has resulted in functionality failure of the chip in end user applications. To mitigate delamination, correlation between no tie bar (NTB) lead frame and surface roughness was studied by examining the critical to quality (CTQ) criteria in wire bonding and molding process parameter. The research work investigated two types of samples which were roughened and non – roughened NTB lead frame. Chips were manufactured through packaging assembly process using both frame samples followed by reliability test assessment such as moisture sensitivity level (MSL), unbiased highly accelerated stress test (UHAST), temperature cycle and high temperature storage (HTS). Characterization study of frames was done with scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X – ray (EDX), optical microscopy, scanning acoustic topography (SAT) and X – ray. The ball shear, wire pull, stitch pull output response for roughened frame was higher than in non – roughened frame in wire bonding process. Whereas in molding process output response, roughened frame displayed better control in horizontal mean offset unlike non - roughened frame which had better control in vertical mean offset. Wire sweep and mold void was comparable in both samples meeting requirements. In reliability test, chips using roughened NTB lead frame demonstrated greater reliability with no delamination compared to non – roughened frame chips at post MSL, UHAST, temperature cycle and HTS test.