Step Coverage Improvement for Electromagnetic Interference (EMI) Shield Film by Forming Bevel-Shaped Packages

Package-level conformal EMI shielding has been adopted for several packages such as memory, wireless, and radio frequency in mobile devices. Both the sidewalls and top surface of these packages must be coated with a conductive thin film as a shielding material. We propose improving metal coverage on package sidewalls for a more cost-effective EMI shielding process. The effects of bevel-shaped sidewalls on sidewall coverage compared to conventional straight sidewalls were demonstrated in this study. A bevel angle of 45° showed nearly 100% coverage while a 60° angle showed 89% coverage. Compared to the current straight sidewall package, coverage was four times higher with the same gap between packages (0.25 mm) using a 75° bevel angle. Two cost-effective conformal shielding processes using bevel-shaped sidewalls were proposed. One is an "All-in-one" process where dicing and sputtering are performed using the same frame. The other is a "Small-gap-array" process that provides higher productivity by mounting more packages with smaller gaps between them.