The 102°C heat rise shown here would indicate there will be additional thermal reduction techniques needed to keep
this part under 105°C total hot spot temperature if this part is to be used at 0.75 watts of power. However, this same
part at the usual power rating for this size would have a heat rise of around 72°C. This additional heat rise may be dealt
with using wider conductor traces, larger solder pads and land patterns under the solder mask, heavier copper in the
conductors, via through PCB, air movement, and heat sinks, among many other techniques. Because of the variety of
methods customers can use to lower the effective heat rise of the circuit, resistor manufacturers simply specify power
ratings with the limitations on ambient air temperature and total hot spot temperatures and leave the details of how to
best accomplish this to the design engineers. Design guidelines for products in various market segments can vary
widely so it would be unnecessarily constraining for a resistor manufacturer to recommend the use of any of these
methods over another.
Note: The final resistance value can be affected by the board layout and assembly process, especially the size of the mounting
pads and the amount of solder used. This is especially notable for resistance values ≤ 50mΩ.
This should be taken into account when designing.
Stackpole Electronics has joined the worldwide effort to reduce the amount of lead in electronic components and to meet the various
regulatory requirements now prevalent, such as the European Union’s directive regarding “Restrictions on Hazardous Substances”
(RoHS 3). As part of this ongoing program, we periodically update this document with the status regarding the availability of our
compliant components. All our standard part numbers are compliant to EU Directive 2011/65/EU of the European Parliament as
amended by Directive (EU) 2015/863/EU as regards the list of restricted substances.