Ultra-low profile metal plate shunt resistor for automotive and industrial applications

ROHM has developed the industry's thinnest (H:0.03"/0.85mm) 12W-rated metal plate shunt resistor (PSR350). It is optimised for high-power applications in the automotive and industrial equipment markets. It will also expand the PSR lineup to include a 0.2mOhm (PSR100) model and a 15W type in the industry's smallest size (PSR330).

Shunt resistors have been employed in power modules for industrial equipment for some time. Likewise, in the automotive sector, the number of thin double-sided cooled power modules adopted in the main inverters of xEVs – demanding to include power device chips (IGBTs and SiC MOSFETs) and shunt resistors to reduce housing size – is growing.

Conventional metal plate shunt resistors decrease the cooling efficiency of power devices due to their relatively high profile. But lowering height has proven difficult, as it is essential to prototype and assess various welding materials in different configurations. The company can employ its manufacturing and design strengths to produce small-lot prototypes in various welding materials and patterns. This flexible development capability tailored to market demands makes it feasible to develop the thinnest power shunt resistors on the market.

The PSR350 utilises the company's vertically integrated production system with material and process optimisation to attain a thickness of only 0.03" (0.85mm), about half that of conventional products in the 12W class. The same technology is employed to develop the industry's smallest size (0.25" × 0.25"/6.4mm × 6.4mm) 15W-rated shunt resistor (PSR330). This lowers the size by about 65% compared to conventional products in the same class, helping to decrease the mounting area in a wide range of high-power applications. At the same time, the PSR100 will be obtainable in a 0.2mOhm model that extends the lower limit from the current 0.3mOhm to detect even higher currents.

These new products are suited to high-current sensing in applications equipped with motors and/or Li-ion batteries.