thanks for all of your comments on bare board testing
i learned a lot and also see better the dark underbelly of this beast
Dennis Saputelli
Jon Elson wrote:
>
> Dennis Saputelli wrote:
>
> > so how does a 'flying probe' test really work?
> > i understand the general idea of a couple of probes walking around the
> > comparing connectivity to a 'netlist' made from the gerbers
> >
> > but it seems to me and i think i read somewhere that this is better at
> > finding opens than shorts
>
> It should ALWAYS find 100% of opens, as it should either test all
> possible combinations of points on a net, or walk down the net, checking
> from one end down to the farthest end.
>
> Checking all possible shorts, especially when opens may be present on the board,
> is not possible, due to combinatorial explosion. So, they have to use some
> sort of algorithm to figure out which nets are most likely to be shorted
> to another. nets which pass close to other nets, or have pads adjacent to
> another net, are the most likely. It is SUPPOSED to be correct practice
> to run the board again after fixing opens, so that the short detection can
> have a better chance of finding a short.
>
--
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