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|High Performance Package-Level EMI shielding of Ag Epoxy Composites with Spray method for High Frequency FCBGA package Application|
|Keywords: Package-Level EMI shielding, Ag Epoxy Composites, Spray mothod|
|Electronic equipment generates undesirable electromagnetic energy that can interfere with the operation of proximately located electronic equipment due to electromagnetic interference (EMI) transmission by radiation and conduction. The electromagnetic energy can exist over a wide range of wavelengths and frequencies. In order to minimize problems associated with EMI, sources of undesirable electromagnetic energy are needed to be shielded and electrically grounded to reduce emissions into the surrounding environment. Shielding is designed to prevent electromagnetic energy. For the package-level EMI shielding solution, sputtering has been conventionally used to protect the devices. However, in order to be in accordance with ultra-thin thickness of product newly EMI shielding methods has been intensively studied in these days such as Ag epoxy composites with spray method. The key for spray method is to development of highly conductive materials and mature process technology. In this study, a novel properties of Ag epoxy composites were developed as key EMI shielding materials for various applications such as Nand flash, various RF devices, and AP chips, etc. A variety of sized and shaped Ag powder was tested to obtain optimized electrical resistivity and mechanical reliability. We also studied the effect of filler and binder contents on mechanical and electrical properties. The resulting Ag paste containing average size (=D50) 6~8um sized and flake shape Ag particles as highly showed ~ 1x10-5¥Ø¡¤cm electrical conductivity corresponding to the bulk platinum. At the 90% of filler contents, the best electrical conductivity and mechanical reliability was achieved. At the 90% of filler contents, the best electrical conductivity and mechanical reliability was shown. Although various coating technique such as Air spray, electro plating, Ultrasonic Spray, and sputtering has been intensively reported to define conductive, we employed air-spray method (Protec Co., LTD, SPR-100) which can achieve high UPH with low cost, high aspect ratio of top surface coating thickness to side wall coating thickness, and micron-scale thickness tolerance. We have investigated on effects of spray parameters such as Spray robot speed, Syringe pressure, pattern-pitch and side-Air pressure and so on. As a result, optimized condition was obtained, which is as follows ¡°syringe pressure:1~2 psi, side-Air 60:psi, pattern-pitch:5mm and robot speed:200~300mm/s for 10um conductive film¡±. Shield effectiveness (SE) was measured by Agilent E5062A in accordance with ASTM D4935 standard and showed more than 60dB, 65dB, 70dB at 5um, 10um, 20um-thick film, respectively. Additionally, mechanical reliability was carried out according to JEDEC Level 3.|
|Kisu Joo, Senior Research Engineer
Hwaseong si, Gyeonggi do
Republic of Korea