PCB Electrical Testing

the PCBs made in

UK except they do

more expensive than

designs, would I be

tested?

How much would you save on 'going untested' ? What would it cost you if you get, say, 1% faulty boards ?

the PCBs made in

the UK except they do

far more expensive than

designs, would I be

tested?

In the quantities I use it costs and additional 25%.

Presumably 1%.

Cheers

Ian

the PCBs made in

UK except they do

more expensive than

designs, would I be

tested?

Electrical testing itself shouldn't be *that* expensive. It depends on what your fallout rate would be and the cost of the assembly. If your board is of any complexity at all (large number of traces and vias, fine pitch traces, etc.) your fallout rate could be substantial. The added cost could be because they know they'll have to eat a lot of boards, rather than the actual cost of testing. That would certainly bust your cost curve, considering that you'll be throwing away finished product instead of just raw boards (as they would be). Find someone else.

has the PCBs made in

the UK except they do

far more expensive than

designs, would I be

tested?

We get a lot more than 1% "x-outs" on even our small boards and we don't see completely bad panels.

Hi Ian,

I always specify BBT for production boards, since it costs so much (in time and effort) to fix faults. Sometimes you will be lucky and get zero failures in a few hundred boards - but sometimes there will be 10% and that is a lot of boards to scrap/repair. Depends a bit on the design rules and the supplier of course.

It seems there are two types of board testing. One type ("flying probe") costs me ~£60 setup and ~40p per board to test. The other ("bed of nails") is ~£200 setup but zero per board.

For prototypes I don't bother, since I will likely spend so much time on them anyway and the quantities are so low that the BBT setup looks very expensive as a "per board" cost. I can't remember ever having a problem on a "prototype" quantity order (say 1-5 pcs). Perhaps they test these anyway, don't know.

the PCBs made in

the UK except they do

far more expensive than

designs, would I be

tested?

I already have someone else who does do electrical test. My only reason for considering changing was to support a local company during the current bad times.

Cheers

Ian

has the PCBs made in

the UK except they do

far more expensive than

designs, would I be

tested?

considering changing was

Ok, you've fixed the expense of building up from defective boards but you still have no idea what your fallout will be. Unless this is an incredibly simple board with very relaxed groundrules, I'm sure it will be much greater than your 1%. Yeah, if it were only a few dimes it might be good to support the local guy, as long as you can make it and your quality doesn't suffer.

Those costs are *highly* dependant on the complexity of the board. We have one where they laughed at us for suggesting bed-of-nails.

Again, that depends on the complexity. As you note above, troubleshooting and repairing boards is *very* expensive, ten times so on an unknown design.

has the PCBs made in

the UK except they do

far more expensive than

designs, would I be

electrically tested?

because

considering changing was

Indeed, if the total cost difference including fallouts was small it would be worth it. I was hoping to get some idea of what the typical insdustry fall out rate is.

Cheers

Ian

As I mentioned in my origin al post, these boards are really quite simple. All through hole components and minimum track size 25 thou/mil. Does that make a significant diffiernce to the fall out rate?

Cheers

ian

Sure, perhaps I should have said that I was talking about two-layer boards only (Ians' "rather simple tube designs"). My supplier always tests 4+ layer boards anyway as part of their process. Even if they didn't I would get them tested since they would likely be always impractical to repair, what with the hidden internal planes and all.

If it ain't broke, don't fix it.

Cheers! Rich

Those are very "generous" design rules. I normally use 8 thou, my supplier will do down to 5 thou without charging extra. However some of the defects I have seen on untested boards would still create failures even with your rules. For example very occasionally there are things that look like "scratches" cutting several parallel tracks. But usually it is single track cuts or shorts.

But yes I think the difference is significant. I think you could risk it. I stuck with untested boards for quite a long time before I gave up on them and paid the extra, And this was with

Correction: laughed at us for suggesting a "flying probe" test. It would have taken all day.

through hole

diffiernce to the fall

Sure, that's three times the width of a normal trace. You only have a two-sided board, another key advantage. Considering that you will do an electrical test before populating the board your favored supplier might be a good bet.

and

I remember getting lots of those in 'the old days' (30 years ago) and they were mostly due to human hairs introduced in the photographic process. I would have thought with CAD this would no longer occur.

Cheers

Ian

Indeed. My only motivation in these hard times was to try to place more work locally.

Cheers

ian

has the PCBs made in

the UK except they do

far more expensive than

designs, would I be

tested?

That assumes YOU test them before committing any resources to populating them - otherwise the cost of a faulty board can rise significantly.

It only happened a few times, and only on ~one board per batch. I guessed they might be scratches on the boards photo resist (rather than on the master photoplot).

But hairs work too :)

the PCBs made in

the UK except they do

more expensive than

designs, would I be

tested?

Ian,

Are you talking about production or prototype quantities?

All the boards I build are prototypes. I'll always specify electrical test as I want to be debugging my design, not boards or the build (I use a good, not cheap assembly house).

I tend to use Kelan (who have recently been bought over) for these boards. They have beaten chinese build prices for 10 offs on reasonably complex (6/8 layer) boards so it might be worth getting them to quote. They are a 'proper' board house, not a pile em high operation like PCB train.

Hope this helps,

Nial