Chip-in packaging technology using aluminum substrate (pocket embedded packaging)

Abstract

Various technologies have been developed to package microwave system to achieve low-cost, high-integration, better RF performance and good thermal dissipation. In this thesis, we propose a new type packaging technology, “Pocket embedding Package (PEP)”, using selectively anodized aluminum substrate. In this technology, chips can be embedded inside aluminum substrate so that ultra thin and compact type of package can be achieved. A MMIC dice with 120㎛ thickness has been successfully embedded inside substrate with a tolerance of less than 5㎛ and, less than 300 ㎛ of total thickness can be achieved with excellent thermal dissipation. More than 120㎛ thick aluminum oxide ( $Al_2 O_3$ ) is selectively anodized on an aluminum substrate with 5% oxalic acid electrolyte. This thick aluminum oxide ( $Al_2 O_3$ ) can be chemically etched with vertical side walls. Rectangular-shape of opening area, which we named “Pocket” is easily formed inside aluminum substrate. After the formation of the pocket, active chips can be embedded inside it with a tolerance of less than 5㎛. Passive components on an aluminum oxide ( $Al_2 O_3$ ) are interconnected with active chips through metallic interconnections. To investigate the performance of passive components integrated on oxalic anodized aluminum substrate, conventional transmission lines and spiral inductors were fabricated. The transmission lines such as microstrip lines, CPW and CPW with ground plane showed lower insertion loss than 0.19 dB/mm up to 20GHz. High-Q inductors were integrated on the 120 ㎛ anodized aluminum ( $Al_2 O_3$ ) and 9㎛ thick copper electroplating process. A 1.78 nH inductor on 120㎛ thick anodized aluminum substrate showed a Q-factor as high as 25 at the application frequency of 2GHz and SRF as high as 16.5GHz. Using the “PEP” technology, we demonstrated power amplifier module (PAM) for PCS band mobile handsets with fully embedded passives on the aluminum substrate and active die inside aluminum substrat...