Evaluation of diffusion patterning as an alternative substrate technology for automotive applications

In automotive applications, electronic circuits are becoming move sophisticated in terms of functionality, power, and density. Specifically, the engine control unit (ECU) is being moved to direct engine mounting, minimizing interconnection length, reducing interference, and simplifying assembly and testing. This type of mounting will reduce the overall manufacturing cost. The electronics must therefore survive higher working temperatures, vibration and wider temperature excursions during on/off and temperature cycles. These requirements have been the driving force for robust multilayer substrates. Diffusion patterning/sup TM/ (DP), a multilayer dielectric technology developed by DuPont Electronics, is evaluated for next generation ECUs. This high density thick film technology achieves via formation through a complex chemical reaction using an imaging paste. Moreover, DP technology may incorporate buried resistors and capacitors. Using DP technology, engine controllers with both four-layer and six-layer structures have been built. The six-layer substrate contains several buried resistors and capacitors. This paper discusses the critical parameters in fabrication of these substrates. The processibility and capacitance variations with different process parameters and firing conditions are also presented. DP technology is compatible with surface mount and flip chip technology. Long term reliability testing of flip chips on DP substrates was performed. After 4000 cycles, reliability data were excellent; no failures were identified. Reliability test results are reviewed.