Power Efficiency Improvement for Low Ohm Current Sense Resistor by Optimum Thermal Management

Abstract

To improve power efficiency, design engineers need to detect current throughout the circuit to minimize power loss. Low ohm current sense resistors are used to detect current to measure and monitor power. These components need to handle higher power to achieve optimal performance. In this work, we extensively studied to improve the power handling capability of low ohm current sense resistors, while maintaining smaller size. We optimized power dissipation by applying innovative thermal management techniques. Employing novel packaging technique, we optimized heat dispersion and minimized the peak surface temperature rise. Using proprietary thermal protection material, we avoided direct heat transfer from component to PC board and minimize the risk of thermal damage against PCB and extreme thermal cycle. We extensively discussed the thermal fatigue of resistor termination structure. Solid metal package construction leads to solder cracks due to thermal fatigue, hence decreases resistor reliability. We improved the packaging footprint and significantly reduced the chance of solder cracking. We optimized the resistor structure for current sensing and shunting purpose. We laid out electrodes and termination in parallel and minimized the contact resistance. Considering these parameters, we manufactured low ohm current sense resistor of 0.5 milli ohm to 100 milli ohm values with up to 5W rated power with tolerance as low as 0.5%.