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Enhance Solder Ball Shear Test Value in WLCSP
Keywords: Ball shear force, SIP Embedded, WLCSP
The trend of putting more functions to portable devices has demanded IC packages with more dies, more components into a smaller footprint. To meet this demand, SiP (System in Package) technology has been one of the alternative solutions to system integration. Compare to SoC (System on Chip), SiP has the advantages of integration of dies made from different technology, e.g. GaAs and Silicon. In ACET・s SiP embedded process, the bare dies are embedded in a filler material to form a panel. Later the dielectric and RDL are processed on top of this panel in a wafer-like process. After making the RDL, the UBM process is followed. After that, the solder balls are placed on top of the UBM. The packages are then tested, inspected and ready for shipping. ACET has successfully use this process in mass production of SiP embedded packages. The technology has been demonstrated both on 12; circular and square panels. ACET has developed SiP embedded with fan out capabilities. Currently, ACET uses filler material and a dielectric material with a low Young・s modules. During ball shear test, the solder ball shear force for solder balls on top of the filler is less than that of on top of the die. For some customers, it is desirable to improve the shear force of the solder ball on top of the filler. For the package in this study, the shear force of solder ball on top of the die is averaged 235 gf, however, the same size solder ball on top of the filler materials is averaged only 136 gf. In order to enhance the solder shear force on top of the filler, the method we used in this study is using dielectric materials with a higher Young・s modules. The high Young・s modules material is used only on the very top layer of package. Three types of dielectric materials with different Young・s modules are studied. The ball share forces are increased from an averaged value of 136 gf to 295 gf for solder ball on top of the filler.
Dyi-Chung Hu, Senior Vice President
Advanced Chip Engineering Technology Inc.
Hinchu 303,
Taiwan


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