Enabling ceramic circuit technologies for wireless microelectronics packaging

The explosion in the use of portable wireless technology operating above the 900MHz frequency range, together with continued integration of functions into discrete IC devices and cost containment are primary drivers for designers to consider alternative packaging technologies to accommodate the functional and cost needs of their end products. Many designers work with either sophisticated polymer circuit technologies, or expensive thin film processes to realize circuit solutions to their needs. This paper discussed two extensions of ceramic thick film technology; firstly low temperature cofire ceramics (LTCC); secondly, photomechanical thick film technology. These offer designers and producers of wireless microelectronics packages several advantages by offering performance enhancements in areas such as microwave components, impedance control, thermal conductivity, and the ability to form very fine, precise geometry's. 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(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 film gold, capable of producing precise geometries of 25 microns and excellent edge acuity; with photoimageable thick film dielectric offering 50 micron vias with a dielectric constant of 3.9 and a loss tangent of better than 10(-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 in a useful manner for the wireless microelectronics designer.