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Useful fakes abound, too

China is fraught with fake parts, but that’s not always a completely bad thing that will ruin you. Sometimes it’s something that will save you lots of money because it works well enough for your needs and is readily available.

Two of the components for my product (the DigiTally, a portable electronic scoreboard) are DC/DC voltage converters (one at fixed 3.3V for the microcontroller, and one at 9V for the LEDs). The parts are pretty simple and do the job well. They are made by National Semiconductor and readily available from Mouser at $2.70 for 1 and $1.17 for 2500. This is for the LM2575 3.3V SMT part. In Shenzhen, I asked for an LM2575 SMT component, and they rushed off to find my part, returning shortly with it and charging me only about $0.40 for each.

The component was pin compatible, with the same footprint as the National part. It worked exactly the same. I didn’t need to modify my design, and I had managed an enormous savings off the cost of my product. It was awesome.

But there was some cost. There are no datasheets for this part. I can’t even figure out what company made it. I looked around for datasheets for other variations of this part and found that there are a few, and that they sometimes have slight changes in the recommended values of nearby attached components. This is slightly disturbing because it means I may not be using the right values for components, but I have no way of knowing. It is essentially a small black box that does what it is supposed to as far as I can tell, but I don’t have the information to back it up, meaning there is some risk in my design. I don’t even know if these are legitimate parts or if they are rejected defects or expired. It’s a gamble.

The other challenge is finding these parts in the first place. I got lucky (maybe) to find this component, but what about my other components? There is no way of knowing if there are other parts that can be legitimate cheaper alternatives to the name-brand components I’m using now. There is no Mouser or Digi-Key for Chinese manufacturers.

I’ve found that cheap resistors abound. I can get SMD resistors of any value for essentially free ($0.002 each). But when I ask for name brand parts, the price jumps to comparable to, or sometimes even higher than, Mouser.

There are two lessons in this. First, that China can be a source of extremely cheap parts and significant cost savings on components. But second, that because it is so hard to verify the provenance of these parts and their specifications, there is some risk in using them, and it may be better for critical components to use name-brand parts with clear datasheets and support.

Permanent link to this article: http://engineerinshenzhen.com/useful-fakes-abound-too/

1 comment

  1. Angus

    So does your fake LM2575 have any kind of labelling at all? Any chance it’s a second hand reclaimed/recycled one, maybe with older tolerances?

    I’d be curious whether the “free” SMD resistor values fall within stated tolerances any better/worse than the name brand ones, or whether there’s any discernable difference at all apart from price.

    Great blog by the way, really enjoying your perspective. :)

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