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MS11449268-1906
www.vishay.com
© 2019 VISHAY INTERTECHNOLOGY, INC. ALL RIGHTS RESERVED.
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Two Key FeaTures oF wFM resisTors
Designers are continually striving to reduce board space and increase the power handling capability of their equipment,
while simultaneously meeting ever-increasing long term stability requirements. The Power Metal Plate™ series has two key
construction features that extend resistance range while supporting these higher power ratings for current sense applications.
Thermal Efficiency + Resistance Alloy = Life Time Stability
Thermally Efficient Design
Copper has a higher thermal conductivity than most metals. The copper plate of the WFM efficiently transfers the heat
generated in the resistive element to the PCB, which enables a higher rated power for the standard footprint. This design
minimizes hotspot temperature extremes, which leads to superior long term stability at higher rated power.
Resistance Alloy
Power Metal Plate current sense resistors use a nickel chromium alloy for resistance values of 33 mΩ and greater. This alloy
has superior stability at higher operating temperatures (220 °C) than copper manganese alloys (185 °C), which provides
two application benefits. First, WFM devices are able to withstand higher temperatures with less lifetime drift. Second, the
resistors have improved pulse capability due to a greater element mass for the same resistance value.
The WFM extends the resistance range for high power surface-mount current sense applications.
Copper heat spreader
Resistance plate
Heat movement to terminal
10
100
1000
10000
0
0.5
1.0
1.5
2.0
2.5
3.0
0.0001 0.001 0.01 0.1 1
Axis Title
1st line
2nd line
2nd line
Watts
Resistance Value
WFM
Power Metal Plate
™
WSLP2512
Power Metal Strip
®
WSL2512
Power Metal Strip
®