Rated Power and VSWR Improvement of Termination Resistor with ...

levels by making good use of the relatively larger area of the circuit board to dissipate the
heat.
We explored the ways to improve heat transfer through the footprint. We established a low
thermal resistance interface from the resistive element to the circuit board. We maximized
the termination electrode’s size. Therefore heat has more ways to transfer from the surface to
the circuit board. We also used high purity, high thermal conductivity chip carrier to further
lower the thermal resistivity. We also investigated special design consideration, to ensure a
balanced distribution of the generated heat.
Improve heat transfer rate:
We studied to improve the heat transfer rate through the component footprint. We realized
that the faster the heat can transfer from the electrodes, the less time the heat has to keep the
electrodes hot. If the heat cannot move faster through the electrodes and more heat is
generating in the chip resistor, then the electrodes keep getting hotter. As the temperature
rise, at some point the surface temperature could exceed the melting point of the mounting
solder and potentially makes a crack in the solder joint. This phenomenon can potentially
cause irreversible changes in resistance – as well as potential damage to the printed circuit
board. We significantly improved the rate of heat transfer through the termination electrodes.
We showed the result of the heat transfer improvement in Figure 1.
Fig 1 a. Conventional power resistor after 1000 cycle
Fig 1 b. TFT power chip resistor after 1000 cycle