- Always test per the manufacturer’s specifications (temperature, voltages, shorts, etc.).
- The device itself must be free of foreign substances, dirt, dust, and other contaminants.
- Isolate the DUT. The device cannot be properly isolated and tested when soldered into a board with other parts connected. These other parts will alter the test results because they are indeed part of the test. Also, the leakage current attributed solely to contaminants on the board (even solder flux and fingerprints) can be higher than the leakage current through the DUT itself.
- Always use properly calibrated laboratory-grade test equipment.
- Never use a battery operated “multimeter” to test leakage current.
- Extreme care must be taken with regard to the testing environment itself and the procedures employed in performing the tests as well. Each must:
- Comply with all industry Electrostatic Discharge (ESD) requirements.
- Employ proper lab grounding techniques (equipment and technician).
- Ensure that technicians are trained properly for the task.
- Ensure that isolation techniques are employed for the DUT…
- Use a proper, calibrated test fixture and shielded test leads.
- Providing shielding from light (for the DUT) and some filtering/shielding from other noise sources (AC line, RF, etc.) may be necessary to detect low nA currents.
Proper testing methods
There are at least three acceptable methods for testing leakage current in RF power transistors:
- Calibrated lab power supply and calibrated (µA or nA) ammeter. (Good)
- Calibrated programmable semiconductor tester. (Better)
- Calibrated curve tracer. (Best)
Current conditions in “Real World” leakage current testing
Engineers and technicians know that a working transistor with too much leakage current, that is to say a working transistor with “out-of-spec” leakage current, can indeed be a problem in the field. Such a device can cause early field failures, exhibit poor performance, be an unnecessary drain