Case Study: New-Generation Airbag Sensors use DuPont Hybrid Circuit Technology
TEMIC Mikrosysteme turned to DuPont thick film materials to package two new types of airbag sensors.
Application Description
TEMIC engineers wanted to improve on their older sensors, which were large and had to be fixed to the car’s suspension. To meet market demands for smaller size, they designed a hybrid circuit with a silicon-based sensor element, a chip- and wire-mounted ASIC, and a band-pass filter with functions covering from 1.5 to 315 Hz. By integrating these components into a small, light, hermetically sealed metal housing, the system was considerably smaller.
Materials Selected and Why
The hybrid circuit is connected to the hermetically sealed housing by 50mm aluminum wire and to the ASIC by 32mm gold wire. In both cases the bond pads are screen-printed onto the circuit using DuPont Au 5723 gold conductor composition. Gold wire bonding was chosen for the ASIC to increase wire-bonding productivity over that of aluminum wire bonding.
TEMIC chose DuPont 7484 for the solderable silver-palladium termination and HS 80 as the resistor material. The resistor geometries are as small as 1 x 1mm with a tolerance of +/-1%. TEMIC uses 100 x 120 mm substrates, each with 72 sensor circuits.
The sensors meet the automotive requirements for reliable operation at temperatures from –40°C to +95°C and have a guaranteed life of 15 years.
