Surface mount foil resistors are commonly produced as two terminal devices with solderable wraparound terminations. They are available in a variety of standard footprints including sizes 0603 up to 2512, like Microhm Electronics MPR series, NMS types.

The typical surface mount foil resistor consists of a flat, rectangular, insulating substrate (e.g., alumina) on top of which the resistor element is bonded using adhesive materials (e.g., resins or polymers). The resistor element is made from proprietary nickel-chromium based alloy ingots that are precision-rolled into foil sheets having thicknesses in the range from ~2μm to ~5μm.


The foil sheets are then developed into serpentine resistor patterns using photolithography and electrochemical etching techniques. A wide assortment of resistor patterns may be produced with individual patterns having resistor lines (also called “gridlines”) having widths ranging from a few microns to many tens of microns depending on the resistance values to be achieved from that pattern.
 

The removal of a shorting tab (process known as trimming) is performed by the manufacturer using laser cutting, mechanical scribing or micro-sandblasting techniques. Removal of a shorting tab connects the associated previously-shorted resistor section in series with the remainder of the pattern thereby increasing the total resistance of the pattern by a fixed amount. By removing various combinations of shorting tabs, the resistor can be trimmed to any desired resistance value within a broad range and also achieve very precise tolerances (e.g., ±0.01%).