Fabrication of a switch module by embedding chip capacitors and an active IC in organic substrate

Abstract

This paper presents a switch module by embedding both chip capacitors and a single-pole-double-throw (SPDT) IC in organic substrate. A switch IC usually needs capacitors as decoupling capacitor. Input port or output port in a switch has DC voltage so that it is necessary DC block when a switch is connected with another IC or stages. Chip capacitors as DC blocks are employed in input and in output of a switch. Optimized capacitors are demanded as DC block capacitor between a switch and other IC. The value of capacitor is dependent on distance of transmission line and dielectric constant of substrate. An embedded IC is analyzed and modelled in order to design a proposed switch module. Embedded capacitors are compared with various capacitors by using modelling and simulation. A SPDT IC as a switch IC is employed and obtained from M/A Com. Proposed organic substrate is composed of Ajinomoto-bonding-film (ABF) and FR4. The total size of a fabricated module is 1.85 mm × 1.48 mm × 0.65 mm. This size is similar to a normal packaged SPDT IC in spite of embedding capacitors in a presented module. A proposed SPDT module consists of a SPDT die and three capacitors. Pad size of each port is die 50 um × 50 um and minimum pitch of pads is 25 um. The size of an embedded die is given as 320 um × 550 um × 160 um. Chip capacitors, 0.6 mm × 0.3 mm × 0.3 mm, are adopted. The drill sizes of blind-via and thru-via is 40 um and 100 um, respectively. Two compact switch modules which embedding an active IC and chip capacitors were implemented and measured. Implemented samples were measured by Agilent's N5230 network analyser and Cascade's probe station. As a result, insertion loss is better than 0.71 dB from 1 GHz to 3 GHz. Return loss is better than 21.6 dB. Good performance was obtained. Active frequency range can be approximately extended to 3 GHz