Perfect molding challenges and the limitations “a case study”

Abstract

Driven by today's market demand, semiconductor is pushing towards the zero-defect direction. The improvement demanded in semiconductor manufacturing is becoming increasingly challenging. In this paper, common molding defects comprise of voids, incomplete fills, and piping holes are studied systematically, focusing on three key areas: 1) Potential mold flow weakness; 2) Molding temperature stability; as well as 3) Defined pressure effects. The in-depth understanding of mold flow in the LF design is achieved via mold flow numerical tool. The numerical model prediction is verified by short shots and end-of-line auto vision data. Advance Process Control (APC) is adopted to measure the stability of key molding parameters like temperature, transfer profile and pressure. The mechanism of transferring the compound in relation to pressure is also analyzed and its effect to molding quality is also assessed. A methodical approach is utilized to understand the process and equipment built-in capabilities from two different equipment manufacturers. The real time transfer profile monitoring is activated for diagnosis of the system issue which leads to the finding of design error of a critical component. The dual temperature controller on one of the systems is analyzed to stabilize temperature for improved compound flow-viscosity control. The process limitations are assessed and transfer profiles are optimized to modify the melt front. By shifting the molding defects to non-critical location, the formation of void at the 500um diameter bonded wire loop peak will be avoided. The verification of potential negative impacts resulted from changes to improve voids, incomplete fills and piping holes are also included in this study. Up-front analysis by adopting numerical tool as a means of understanding the existing design and identifying improvement approach are proven to be useful.