A High Performance Package with Fine-Pitch RDL Quality Management

摘要

In this research, a good solution to achieve high quality fine-pitch Re-Distribution Layer (RDL) has been demonstrated by controlling bottom Radio Frequency (RF) power of plasma treatment on Polyimide (PI). The experimental results shows both overly large RDL undercut and interfacial void defect are caused on a rough PI surface. A lower bottom RF power treatment is able to carry out a smooth PI surface. This process solves fine-pitch RDL delamination issue, and RDL undercut can be mitigated to an acceptable level. Most important of all, interfacial void defect between PI and RDL is eliminated on smooth PI surface. Moreover, a model has been established about a mechanism of surface roughness affecting interfacial void and RDL undercut. The model also verifies the optimal PI surface properties for fine-pitch RDL. Finally, this enhancement solution for fine-pitch RDL has been successfully implemented on high performance package e.g. Fan-Out Chip on Substrate (FOCoS) proposed by ASE group [1]–[3].