Bitten By PCB Defects

If you’ve ordered PCBs from Seeed Studio, ITead, DirtyPCB, or another board house in China, you’ve probably noticed that neat little 100% e-test option available on the order form. If you select this, the board house will throw your PCBs in a machine that will poke a pin in every pad to make sure all the connections are good. Less work for you, right? As [Andy] found out, not always. He was bitten by a manufacturing defect that sheds some light on what that e-test actually is, and the capabilities of what these Chinese board houses can do.

Most of [Andy]’s project have a lot of surface mount components, and when he receives his boards, he notices a few pin pricks on each and every pad. This is from a flying lead machine; a robotic continuity checker that makes sure all the relevant pads are electrically isolated from each other.

One of [Andy]’s recent projects is an entirely through-hole design. Apparently these robotic meters don’t test through-hole pads; it’s significantly harder to measure the continuity of a hole rather than a pad, apparently. After assembling one of these boards, he noticed a problem where one of the GPIOs was permanently high. The offending trace was found underneath a DIP socket, in precisely the worst possible place it could be.

If [Andy] had inspected the board beforehand, this problem would have been avoided. He says it was a relatively simple board with big traces and wide spaces and he didn’t think a manufacturing defect was possible. He was wrong, and now we have a warning. We thank him for that.

Finding the cheapest board house


The prices for custom made circuit boards has never been cheaper, but surprisingly we’ve never seen a comparison of prices between the major board houses. [Brad] took the time to dig in to the price of 10 boards manufactured by Seeed Studios, OHS Park, and BatchPCB. He made some pretty graphs and also answered the question of where you can get your circuits made cheaply.

[Brad] got the prices for boards up to 20 cm x 20 cm from Seeed Studio’s Fusion PCB service, OSH Park, and BatchPCB. These results were graphed with Octave and showed some rather surprising results.

For boards over 20 cm2, the cheapest option is Seeed Studios. In fact, the price difference between Seeed and the other board houses for the maximum sized board is impressive; a 400 cm2 board from Seeed costs $150, while the same board from OSH Park is close to $1000.

Of course most boards are much smaller, so the bottom line is  for boards less than 20 cm2, your best bet is to go with OHS Park. If you don’t care when your boards arrive, or you need more than 10 or so, Seeed is the way to go. As far as the quality of the boards go, OSH Park is up there at the top as well.