Advanced integrated passive device (IPD) low pass filter designs on WLCSP

An integrated passive device (IPD) solution is one of the important implementation employing the advanced redistribution layers (RDL) technology to fabricate the design passive components. This paper would demonstrate DCS (GSM-1800) Band low pass filter design by using RDL technology. For the design requirement, the specification of insertion loss (EL) of LPF was required bigger than -0.8 dB, return loss (RL) was less than -20 dB, and the attenuations was smaller than -30 dB at two times and three times harmonic frequencies. For the circuit topology selection, in order to achieve a better electrical performance and gain a smaller pattern size, we consisted of five capacitors and two spiral inductors design to miniaturize and fabricate our prototypes. The measurement results were able to meet our demands and they were shown in below: Insertion Loss (EL): -0.8 dB, Return Loss (RL): -20 dB, Attenuation @ 2F0: < -30 dB, Attenuation @ 3F0: < -40 dB, and Pattern size is 1.6 x 0.5 mm . This paper successfully used RDL technology to demonstrate the IPD low pass filter and achieved miniaturization design for GSM-1800 (DCS) Band applications.