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DuPont Microcircuit Materials

DuPont QG150 Thick Film Au Conductor Replaces Thin Film In Wireless Base Station

Description/Application

Design engineers seeking new materials to accelerate time to market and reduce costs in wireless/RF applications are finding that thick film solutions can replace thin film designs in RF devices. Thick film can answer the demand for substrate materials that have excellent performance at high frequencies and facilitate rapid design changes.

Challenge: Cost-Effective High-Frequency Microcircuits

Thin film technology has been the technology of choice for many RF applications in the military and aerospace market segments. In order to provide high-frequency capabilities, thin film designs are usually implemented using sputtering and etching on 99.5% alumina substrates. However, as the number and volume of commercial RF applications grow, thin film designs become expensive, and less costly alternatives are in demand.

Solution: QG150 for Fine Lines in RF Applications

Micro-Precision Technologies (MPT) of Salem, NH, a manufacturer of hybrid microcircuits for wireless/RF applications, recently developed a single-substrate surface mount attenuator/phase shifter for cellular communication and PCS base stations using thick film materials from DuPont.

MPT chose QG150, DuPont's new high-density etchable gold composition, to pattern 30-micron lines and 40-micron spaces on a 96% alumina substrate. The etchable gold composition is ideal for these circuits because high-resolution lines are required for high frequency in RF and microwave applications.

DuPont 6277 (Ag-Pd) and DuPont 9750 (Ag-Pt) were used for solid through-hole plugs in the substrate, for a back plane, and for surface mount pads. Bare ICs are attached using gold wire bonding. A solid through-hole plug prevents solder, solder flux or cleaning chemicals from flowing from the bottom surface to the top surface and damaging the bare ICs or fine pitch lines. Plated through-holes used in the thin film process are susceptible to solder wicking and contamination from flux and cleaning chemicals.

MPT's thick film design shows significant improvement over an earlier version using thin film, and cost analysis suggests it reduces expense by about 30-40 percent. In addition, design changes to facilitate circuit fine-tuning are faster and less expensive with the thick film design.

MPT's new attenuator/phase shifters are available for 800-1,000 MHz and 1,800-2,000 MHz applications. Currently, a series of low-cost, surface mount RF amplifiers with ultra-low noise and high dynamic range is under development at MPT, using QG150 along with thick film resistors that are screen-printed and laser-trimmed on the same substrate.

For more information, call DuPont at 1-800-284-3382, press 3.