Measuring leakage current in RF power transistors: Page 5 of 6

October 26, 2011 //By William R. Murphy, Richardson RFPD
Around the globe, engineers and technicians using RF power devices have had many concerns regarding the specifications for leakage current, what the specifications mean in terms of the part's performance in the field, and most importantly, how to properly test/verify that a given part is meeting its printed leakage current specification...
an otherwise good device.

Issue #4
Improper grounding/shielding/isolation methods are employed with the DUT.

Problems caused
Testing with improper shielding, grounding, and isolation will lead to erroneous and invalid measurements; and it may also damage the part.

Issue #5
Uncalibrated test equipment being used.

Problems caused
Using uncalibrated test equipment will produce erroneous and invalid measurements.

Issue #6
Devices not tested at the proper temperature.

Problems caused
If the parts are not tested to all manufacturers’ specifications, then there is no way to prove that a part does not meet its specifications.

Improper leakage current testing lead to these unfortunate consequences:

  1. Both “good” and “bad” devices are being damaged unnecessarily, and this makes further analysis impossible.
  2. Some devices that are actually within specification are being thrown away or being rejected/returned because of erroneous test results. This happens at the “incoming inspection” stage, in some cases.
  3. Root causes of other RF transistor problems are being “masked” (i.e. undetected and undiagnosed) if leakage current is improperly tested and labeled the “cause.”

Final recommendations:

  1. All RF components and subassemblies used in complex and critical designs (i.e. military, avionics, broadcast, etc.) should be parametrically evaluated in order to make sure that they meet published specifications.
  2. Component testing must be performed properly. Carefully review your test set-up and methods to insure that your leakage current (and other testing) is safe, calibrated, reliable, and repeatable.
  3. As a service offering, Richardson RFPD can help customers to perform DC testing (including leakage current) and/or RF testing on components and assemblies that we supply. In our testing facilities, fully automated test systems are employed to test volume production parts, including those parts on tape and reel. All test data is electronically stored and can be supplied per request. Critical component testing can increase field reliability, improve product performance, and save cost. Richardson RFPD uses trained technicians, fully-calibrated test equipment, and adheres to all manufacturer and industry testing specifications.

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