Application of the IForce piezoresistive silicon based stress sensor for prognostic and health monitoring methods

Miniaturization and simultaneous increase of complexity and functionality of modern electronic control units (ECU) leads to the situation that the classical reliability methods become less and less sufficient. Reliability prediction in automotive industry is complex, as the load history on the system level (e.g. car) is multi-domain and depends on many different factors such as the climate, the type of the car, user, etc. Currently, the reliability of the ECU´s is assessed on the subsystem level. In order to assess reliability on the system level, prognostic and health monitoring (PHM) is the most promising method. In this paper the IForce, piezoresistive, silicon based stress sensor is implemented to monitor the stress state during passive and active power cycling (APC) of the ECU. Two ECU´s-original and overmolded are subjected to combined active power and passive thermal cycling. The active power is dissipated in the commercially available DPAK IC package. The APC is conducted at different temperatures between -40°C and 70°C. The signals of the IForce sensor are first validated by simultaneous measurements using moiré interferometry. In addition, the FEM simulations are conducted, which can be further used to assess the life time model of two possible failure modes of the DPAK power package: solder joint fatigue and wire bond lift off.