High-current, reflowable thermal protection device for automotive electronics

November 13, 2014 // By Graham Prophet
TE Connectivity's HCRTP device’s high-current capability (90A at 23ºC) offers a robust, simple approach for complying with AECQ standards for engine-compartment applications

TE Connectivity's Circuit Protection business unit (TE Circuit Protection) has introduced a High-Current Reflowable Thermal Protection (HCRTP) device to safely disconnect automotive sub-systems in fault conditions.

Specifically suited to high-power, high-current automotive applications – such as ABS modules, glow plugs and engine cooling fans – the robust HCRTP device (model: RTP200HR010SA) can withstand hold currents of up to 90A at room temperature (23ºC) and 45A at 140ºC. In addition to helping automotive designers comply with stringent AECQ automotive standards (including the AECQ vibration test), the surface-mountable HCRTP device speeds installation.

The device is intended to disconnect systems in the event of a fault such as a failed output power transistor, that would cause the ECU (electronic control unit) to draw fault currents high enough to present a hazard, but not enough to rupture a line fuse. The HCRTP has a low-resistance, in-line heating element that melts an internal link in response to fault current. The link is mechanically held in place during reflow soldering, making the part surface-mountable, and the device is then activated by a current pulse to a separate terminal after installation.

The HCRTP device builds on TE Circuit Protection’s RTP technology. This technology helps protect electronic systems in the event that power FETs, capacitors or other power components fail due to increased resistance, thus causing thermal runaway. It uses a one-time electrical activation process to become thermally sensitive. Prior to activation, the HCRTP device can withstand lead (Pb)-free solder reflow processes up to 260°C without opening. But following installation, the one-time electrical arming process initiates a lower thermal threshold of 210°C. After arming, which is typically done at end of line testing after reflow, the device will open when the critical junction exceeds the 210°C open temperature.

Available in a low-profile (3.7mm max.) package, the HCRTP device can be installed using industry-standard, Pb-free, SMD (surface mount device) assembly and reflow processes. In comparison, radial-leaded thermal fuses must