Using SMT chip resistors beyond their rated thermal specification

Electronic chip resistor used in a PCB come in various sizes, e.g. 0402, 0603, 1210, etc. The bigger the component size, the higher its power handling capability. A downside of using bigger component sizes is the real estate constraint on the PCB. Modern day electronic products are smaller in size thus limiting the PCB size and overall number of components that can be placed. This paper studies the chip resistor temperature dissipation when mounted on a PCB. It then attempts to characterize the resistor for a higher power rating than what is specified by the resistor manufacturer. This is possible because for a resistor which is mounted on a PCB, the dominant heat dissipation path is from the chip resistor into the PCB and then subsequently into the atmosphere. A thermal camera was used to measure the chip resistor temperatures. After power and temperature data was obtained, the thermal resistance (R
_th
) of the resistor was calculated and an average R
_th
assumed for that specific component. With R
_th
data obtained, it can be calculated that chip resistors can be used at powers exceeding their manufacturers rating depending on the mounting conditions.