Counterfeit Components

April 2011

This is simply my experience with counterfeit electronic components. All parts are not made equal and some can get you into quite a bit of trouble.

Below is the image of a less than perfect transistor.

I required a small amplifier with a frequency response of Hz to MHz with an output of 50 volts peak to peak. The class A output transistors chosen were BD139's as they run in an emitter follower configuration it was assumed with an transition frequency of 190 MHz they would do the job. A quality Fairchild spice model was obtained.

Back to the story, a design was successfully spiced, a pcb designed, routed then assembled, it failed to perform as intended. After wasting hours thinking all sorts of things that could be wrong my thoughts turned to the bargain priced BD139's purchased on-line.

Drove 20 km to Adelaide City paid 50 cents each for a quantity of brand name name BD139's from a reputable supplier (Aztronics). Drove home through the slow traffic and fitted the new transistors to the circuit board, guess what? Worked as per the simulation!

Question

How cheap were the bargain on line purchased transistors?

Time lost, hours. PCB beaten up from fiddling (actually RCB, Routed Circuit Board). At least the grandchildren came around and cheered me up.

Conclusion

Parts from reputable manufacturers and suppliers are often the best choice.

Something to look for with the TO-126 package:

• Cheap looking with the insulating case material actually over the top of the metal pad meant to make good thermal contact with the heatsink.
• The insulation in the mounting hole defective to the extent a collector to screw short circuit can occur.

Below is a link to another case of counterfeiting. These chips have no chance of working! At least my fake BD139's work at a reduced voltage and frequency.

http://www.sparkfun.com/news/350