A New LTCC with Pb-Free Resistor System for ECU Substrate

A new LTCC (Low Temperature Co-fired Ceramics) substrate material has been developed for automotive applications used for harsh environment ECU (Electronic Control Unit). Features of the LTCC include high mechanical strength, high dimensional tolerance (+/- 0.1 %), low conductor resistance (2 mΩ / square), and Pb-free thick film resistor systems on the LTCC. These characteristics of the LTCC substrate are suitable for automotive harsh environment applications. Surface conductors are completely covered with Ni/Au plating, which provide sufficient wire bondability for both Au and Al wires. The resistor system consists of Pb-free RuO₂ resistor and Pb-free over coated glass which provides protection. Low ohm resistor also consists of Pb-free Ag/Pd material. All of the resistors can be trimmed by laser with their resistances controlled within +/- 1 %. The resistors have less than 1% drift after 3,000 temperature cycles at -40 and 150 degree C condition. This resistor system and substrate meet a durability requirements for automotive applications.