Reliability Design and Optimization Process on through Mold via using Ultrafast Laser

Abstract

In this study, a through mold via (TMV) process using ultrafast Laser has been developed for the interconnection on 3D package-on-package (PoP) application. Epoxy molding compound (EMC) is a composite material consisted of epoxy resin, filler particles (fused silica) and other constituents. Among these chemical compositions, the size and spatial distribution of fillers on the EMC dominate the sidewall quality on drilled trench. However, random filler leakage on the sidewall leads to an irregular and uneven trench and these drop out fillers become a problem needed to be solved. Faster removal of debris can be achieved by controlling the laser drilling parameters. Parametric studies have been performed to determine the specification of trench and design rule of material. The optimal desmear process on TMV bottom PoP package developed in this study demonstrates the reliability improvement on follow-up sputtering or filling process.

Via Interconnections for Half-Inch Packaging of Electronic Devices Using Minimal Fab Process Tools

“…The underlying fabrication process technology of the FOWLP such as vias, redistribution layers (RDL), and solder joints have been developed to obtain high-reliability interconnections between the electrode pads on Si chips and solder balls mounted to the external terminals on a package [14,15]. A laser-via process, which is able to open the vias by irradiation of a laser beam to an epoxy mold compound (EMC) on the pads, has often been applied to the fabrication technology of the vias [16][17][18][19][20][21]. Typically, in the EMC used for protecting the Si chip, spherical particles of SiO 2 known as silica fillers are contained in the epoxy resin to reduce the mismatch in coefficient of thermal expansion (CTE) between the Si chip and the EMC [22,23].…”

“…During laser ablation process, SiO 2 which has a higher melting point than epoxy resin is difficult to ablate. The non-ablated silica fillers greatly affect the via-interconnections since it redeposits around the vias and remains on the bottom of the vias [20,21]. This is a common issue in the general packaging technology, not only the FOWLP technology.…”