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TAP TIMES -8- OCTOBER 2022
High-power socket design (from 6) or crown tip with a contact surface are
around 30-50mm .
QFN probe increased the thermal time 2
constant to 1910msec and the continuous Insure contact reliability
current almost tripled to 5.73A for 20 °C The small surface area is needed to gener-
rise. ate enough pressure on the device pad to
break through surface oxides and ensure
The limit of the measuring equipment is contact reliability. Devices with matte
20A. At a 1% duty cycle, the curve proj- tin plating on the pads require significant
ects well past 50 Amps to produce the pressure to break the oxide layer and con-
temperature rise. duct properly.
Measured at the center The small contact surface area will have
The temperature is measured at the center a much larger temperature under a con-
of the probe so the temperature at the tips stant current load greater than 250°C at
is unknown in these measurements. 15 Amps. The contact tips may have a
very limited air flow to cool the probe con-
The temperatures at the contact surfaces tact area so the assumption is the probe
of the probe are a function of the con- contacts in a high current application will
tact surface area to device pad surface ablate over constant insertions.
area. Typically, a probe will have a conic next page
