[sdiy] PCB assembly house board failure rates?

[Phil Macphail]

My experience of high-volume assembly (>5M boards/year) was that a failure rate above 1% was a major issue. That was with automated placement and reflow soldering, so failures were mostly due to circuit design not being tolerant of device variation - yield was considered to be a direct indicator of design quality. 
Manufacturers have the advantage of consistency and throughput, both of which increase yield so you can't really compare with hand assembly, but it is fair to say that a good design made with quality parts shouldn't need any debugging to work as intended. Failures should be dominated by such things as solder-bridges and wrong part placement, when they are done by hand.
I did once design a board that had a 96% yield from the pilot run, and the factory was making a big issue of this. Turned-out they had done a 'Les Dawson' - all the right parts in all the wrong places. Fixing this turned the failures into passes and everyone was happy, but there was a big pile of boards to scrap as all the benefits of automated production had been applied to replicating the wrong thing with great precision....

Phil



On 17 Jan 2013, at 16:28, Justin Owen <juzowen at gmail.com> wrote:

> Hello,
> 
> I'd be interested in what people would consider an 'average' or 'fair' failure rate as a percentage for boards assembled by a professional PCB house - based on their own experiences.
> 
> Acknowledging...
> 
> (1) that's a wide open question to interpret, so let's say boards of up to 200 non-exotic, surface mount components and up to a half-dozen bits of through-hole hardware i.e. Pots, Sockets etc. on a reasonably densely populated 2 layer board. Synth stuff basically...
> 
> and...
> 
> (2) I'm not talking about the times when something just goes completely wrong due to some sort of traceable failure.
> 
> Fair wear and tear, average attrition, etc.
> 
> FWIW - I'm asking because I notice that as I start using smaller and smaller parts in my own hand-soldered designs/protos, etc, I feel like my own attrition/failure rate is going up a bit. I was wondering if manufacturers faced the same thresholds and how they would generally deal with that?
> 
> Thanks!
> 
> Justin
> 
> 
> 
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