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26 The PCB Magazine • June 2017 termined the heater needs to have a resistance of roughly 10 ohms. This can easily be designed using a resistive conductive material with a sheet resistivity of 10 ohms per square. The re- sult would be a single square resistor 12.7 mm x 12.7 mm in size. As a comparison, to achieve the same temperature rise/power using a 0.254 mm (10 mil) wide trace of half-ounce copper would require a length of 2500 mm. Using an equal trace/space width would only allow ap- proximately a quarter of the required length to fit in the target area. Long Term Operation at High Temperature A test was performed to measure the long- term effect of operating a thin film resistor in THIN FILM NiP EMBEDDED RESISTORS IN HEATER APPLICATIONS Figure 6: Long-term high-temperature resistor/ heater operation. Figure 7: Example of a burn-in board.