High-Q RF passives on organic substrates using a low-cost low-temperature laminate process

This paper reports on a low-cost low-temperature (≤150°C) laminate batch fabrication process for implementation of high-Q RF passive components (inductors and capacitors) in system-on-package (SOP) applications. Using this process, various designs of integrated inductors with Q-factors in the range of 60-180 for Bluetooth/IEEE 802.11b (2.4GHz), GSM1800 (1.SGHz) and GSM900 (900 MHz) communication standards have been implemented on an organic package substrate. For the first time, a maximum Q of 180 was measured for a 4.8nH inductor at 2.0 GHz on an organic substrate with a self-resonance frequency (SRF) of 5.5 GHz within an area of 9mm². High-Q inductors and capacitors integrated on low-loss organic package substrates can find numerous RF and microwave SOP applications (such as VCO, IF/RF bandpass filters, LNA, etc), in which IC chips are flip-chip mounted on the package substrate. Integration of passives in organic substrates eliminates the excess cost of assembly, enables miniaturization by allowing for added functionality at the board level, and provides an attractive alternative to higher temperature processes such as ceramic and deposition technologies for high-Q passive implementation.