ISA-PLAN®-technology:

Thanks to their high accuracy, low costs and easy assembly, current sensing resistors which can be soldered directly to the substrate are being increasingly used to measure the output phase current in power modules.

The bondable precision resistors of the PMx range (PMU, PMB, PMH) are manufactured using Isabellenhütte's patented ISA-PLAN® procedure, in which three sheets of Manganin®, a metal substrate (copper) as well as a heat-conductive adhesive are compressed together. The ultra heat-resistant glue ensures excellent adhesion, insulation, low thermal resistance and optimum heat dissipation from the resistance material into the substrate. In order to optimize the soldering of the resistor onto the IGBT substrate, the copper reverse side is covered with a 0.2 µm layer of gold leaf. This sandwich structure allows ideal thermal conductivity to the heat sink (substrate) and thus excellent load capacity of the component up to 20 Watt/cm². The power loss dissipation is kept extremely low by the very low-ohmic resistance values of <5 mOhm.

With <30 ppm/K at 20 to 60 °C the temperature coefficient (TC) of the resistance material Manganin ® ensures precise current measurement with minimal error tolerances. The PMx resistors remain impressively precise even at higher temperatures, e. g. <0.5 % up to 140 °C and 1 % up to 170 °C. The space-saving construction (e.g. type 2512), combined with the technology used, allows an extremely good power/space ratio.

Four-Wire Resistor
With a simple two-wire measurement, the combined TCs of the strip conductors and bond wires would lead to imprecise measuring results. A four-wire measurement eliminates the influences of the supply line and contacts so that only the voltage drop at the resistance material itself is measured.