Cicor developed the processes for the assembly and interconnect technologies for the customer. The exhaust sensor is based on thick-film ceramic made of aluminum oxide (Al2O3) that is assembled by Cicor with a number of components. The SMD elements, with SMD 0402 as the smallest component used, and the housed chip are soldered to the substrate. The naked sensor chip, on the other hand, is attached directly to the ceramic in a complex process and protected from external influences by an additional chip protection ring.

The greatest challenge in manufacturing the product is accounting for the high temperatures and environmental conditions prevalent inside the exhaust system. The finished sensor system must maintain pressure of up to 6 bar within a large temperature range of − 40 °C to 130 °C and function properly. Special processes for the assembly and interconnect technologies were used to guarantee reliability and long-term stability.

The sensor chip is attached with silicone adhesive to part of the thick-film ceramic to ensure 100% impermeability. Silicone adhesive is able to absorb the mechanical tensions through the different temperature coefficients of the materials. The material properties of the silicone adhesive, how- ever, are not beneficial for further processing (wire bonding). The sensor chip also has to be attached to be able to ensure the stability of the circuit. Additionally integrated adhesive points made of SMD adhesive under the chip make heatintensive bonding with gold wire possible and give the chip the necessary stability for wire bonding. Gold is a very robust precious metal which shows minor signs of fatigue even when temperatures fluctuate significantly. Monolithic connection systems, in this case gold with gold, produce reliable connections which are stable over the long run. To increase process reliability, bonding is performed with active bond process control. With this non-standard interconnect technology, Cicor ensures the bonding of a chip adhered with silicone meets the highest quality standards.