A miniaturized module for Bluetooth/GPS by embedding capacitors in printed-circuit-board and using interposer

This paper presents a compact module for a Bluetooth and GPS by using both interposer and embedding technology. Interposer technology with fine line/pitch and embedding technology are proposed to implement a compact module. Capacitors are embedded in printed-circuit-board (PCB) as called as System-on-Package (SoP). A Bluetooth IC and a GPS IC are mounted in interposer. In side view, ICs, interposer substrate, and a PCB with capacitors are sequentially located from top and bottom. This module is composed of a Bluetooth IC, a GPS IC, interposer with 30 um line width, and a PCB with 17 shunt capacitors. Capacitors are embedded by using chip-first process so capacitors are located in the middle of PCB substrates. In this process, surface mounting technology (SMT) is employed as part of proposed process. SMT can arrange a lot of components in wanted position. Flux problem can be solved by controlling temperature and speed of conveyer belt. As a result, various capacitors are able to be embedded in this module. Three times lamination and 6 copper layers are proposed in PCB. The dimension of a capacitor is 0.6 mm × 0.3 mm × 0.3 mm. Capacitor values as 2.2 uF, 1 uF, 470 nF, 100 nF, 22 pF, 18 pF, and so on are embedded in PCB. Interposer is made of Ajimoto-bonding films (ABFs) to fabricate fine line/pitch. Most of signal and power lines are synthesized in this substrate by employing fine lines. Interposer has 4 copper layers. In order to check the performance and size for embedded modules, two representative modules for Bluetooth/GPS with SMT and with SoP are designed and compared. The size of module with SMT and SoP are as 15 mm × 10 mm and 12 mm × 7 mm, respectively. Almost 44 % size reduction is obtained by SoP. Measured Tx power and Rx sensitivity in Bluetooth are given as 5.5 dBm and -72 dBm, respectively. The received signal strength of GPS is -162.1 dBm/Hz. Actually, Bluetooth and GPS are well performed. This paper presented that SoP technology was better than SMT technology in a view of size. Implemented module had good performance and slim size.