Enabling ceramic circuit technologies for wireless microelectronics packaging

Abstract

This paper discusses two extensions of ceramic thick film technology for wireless microelectronics packaging; firstly low temperature cofire ceramics (LTCC); secondly, photomechanical thick film technology. These offer performance enhancements in areas such as microwave components, impedance control, thermal conductivity, and the ability to form very fine, precise geometries. Additionally the end package cost versus traditional thick and thin film technologies has been substantially decreased primarily due to size and process step reduction. Two materials systems, KQ subtractive thick film and Heratape/sup TM/ LTCC, enable the design of complex, high frequency, mixed signal circuitry for wireless devices. KQ technology is particularly relevant at higher microwave frequencies where it offers performance at least equal to thin film technology at greatly reduced cost. It combines a dense, photoengraveable thick gold film, capable of producing precise geometries of 25 microns and excellent edge acuity; with a photoimageable thick film dielectric offering 50 micron vias with a dielectric constant of 3.9 and a loss tangent of better than 10/sup -4/. Heratape LTCC is based on a tape dielectric (K=7) that is capable of reliably producing silver, gold, and mixed metallurgy bearing substrates with a high layer counts. Data substantiating this performance is presented.