Various Topics on Electronics - Cad

..ckm..

I had some PCBs made with 22 boards per panel (small boards). I
wanted a single panel for prototypes, but it turned out I could get 6
panels for only $500 more. This would get me through the first round
of production if I didn't need any changes. The day the maker was
supposed to ship them, I got an email saying they had a poor yield and
only got 116 good boards out of 7 panels vs the 132 I ordered.

So now I have a concern about the quality of the boards. I was told
the failed boards had problems with the plating in the 10 mil holes I
used for vias. They claim that the "good" boards have no quality
issues. My concern is that the vias may be marginal and open once
they are temperature cycled a bit.

I am not sure how to handle this with the vendor. I guess I could
just flat out tell them that I am concerned with investing some
$18,000 building up over 100 boards only to have my customer see
failures in the field. I don't feel like they have done 100% on this
since they did not provide the quantity I requested.

They have offered to rebuild the entire set of panels if I am not
happy with the result, but that would be a week delay. I also don't
know if they are willing to let me use one of the current panels and
remake the rest.

Anyone have experience with 10 mil via holes and reliability issues?
If you have a problem with an order like this, is it reasonable to use
one panel and reject the rest?

..nn..

> Anyone have experience with 10 mil via holes and reliability issues?
> If you have a problem with an order like this, is it reasonable to use
> one panel and reject the rest?

As you have figured-out, pushing the process limit could be
expensive. We would not go below 16 mil holes, even if we need bigger
boards. Are you sure you can't use bigger holes?

..ckm..

On Apr 10, 11:26 am, linnix <m...@linnix.info-for.us> wrote:
> > Anyone have experience with 10 mil via holes and reliability issues?
> > If you have a problem with an order like this, is it reasonable to use
> > one panel and reject the rest?
>
> As you have figured-out, pushing the process limit could be
> expensive. We would not go below 16 mil holes, even if we need bigger
> boards. Are you sure you can't use bigger holes?

Sure, I can use bigger holes. But I can't use bigger pads. It was
hard enough to make the layout work with 10 mil holes and 24 mil
pads. This board is very small and defined by the customer's
requirements. It is a daughter card on an existing product so I have
no flexibility in size except for extending one end which I have
already done as much as possible. Even that does not do a lot for the
density issue since the board is over 5 times longer than it is wide.
Extending the length more just means I have longer lines to try to
squeeze through the same bottlenecks around the chips and
connectors.

I guess I am confused about "process limits". I have seen vendors
that claim to have capability for hole sizes down to 6 mil. They just
say that they can't guarantee that the hole will not be plated closed
which is fine with me. So I don't see where 10 mil holes should be a
real issue. Did I pick a poor PCB maker? Am I just not grasping the
realities of PCB manufacturing?

..v..

"rickman" <gnuarm@gmail.com> wrote in message
news:b54bdd8a-f575-4a41-a4f1-888f600fe515@k13g2000hse.googlegroups.com...
> On Apr 10, 11:26 am, linnix <m...@linnix.info-for.us> wrote:
>> > Anyone have experience with 10 mil via holes and reliability issues?
>> > If you have a problem with an order like this, is it reasonable to use
>> > one panel and reject the rest?
>>
>> As you have figured-out, pushing the process limit could be
>> expensive. We would not go below 16 mil holes, even if we need bigger
>> boards. Are you sure you can't use bigger holes?
>
> Sure, I can use bigger holes. But I can't use bigger pads. It was
> hard enough to make the layout work with 10 mil holes and 24 mil
> pads. This board is very small and defined by the customer's
> requirements. It is a daughter card on an existing product so I have
> no flexibility in size except for extending one end which I have
> already done as much as possible. Even that does not do a lot for the
> density issue since the board is over 5 times longer than it is wide.
> Extending the length more just means I have longer lines to try to
> squeeze through the same bottlenecks around the chips and
> connectors.
>
> I guess I am confused about "process limits". I have seen vendors
> that claim to have capability for hole sizes down to 6 mil. They just

Did the vendor you chose give this claim? If not then there's your problem,
choose a different vendor.

> say that they can't guarantee that the hole will not be plated closed
> which is fine with me. So I don't see where 10 mil holes should be a
> real issue. Did I pick a poor PCB maker? Am I just not grasping the
> realities of PCB manufacturing?
>



--
DaveN

..v..

"DaveN" <DaveN@DaveN.COM> wrote in message
news:qDqLj.96922$833.45298@newsfe17.ams2...
> "rickman" <gnuarm@gmail.com> wrote in message
> news:b54bdd8a-f575-4a41-a4f1-888f600fe515@k13g2000hse.googlegroups.com...
>> On Apr 10, 11:26 am, linnix <m...@linnix.info-for.us> wrote:
>>> > Anyone have experience with 10 mil via holes and reliability issues?
>>> > If you have a problem with an order like this, is it reasonable to use
>>> > one panel and reject the rest?
>>>
>>> As you have figured-out, pushing the process limit could be
>>> expensive. We would not go below 16 mil holes, even if we need bigger
>>> boards. Are you sure you can't use bigger holes?
>>
>> Sure, I can use bigger holes. But I can't use bigger pads. It was
>> hard enough to make the layout work with 10 mil holes and 24 mil
>> pads. This board is very small and defined by the customer's
>> requirements. It is a daughter card on an existing product so I have
>> no flexibility in size except for extending one end which I have
>> already done as much as possible. Even that does not do a lot for the
>> density issue since the board is over 5 times longer than it is wide.
>> Extending the length more just means I have longer lines to try to
>> squeeze through the same bottlenecks around the chips and
>> connectors.
>>
>> I guess I am confused about "process limits". I have seen vendors
>> that claim to have capability for hole sizes down to 6 mil. They just
>
> Did the vendor you chose give this claim? If not then there's your
> problem, choose a different vendor.
>

Sorry, I meant did your vendor make the claim on 10mil?

Additionally did you order 132 boards or the yield acheived from the panels?

>> say that they can't guarantee that the hole will not be plated closed
>> which is fine with me. So I don't see where 10 mil holes should be a
>> real issue. Did I pick a poor PCB maker? Am I just not grasping the
>> realities of PCB manufacturing?
>>

The realities with any process is that as you approach its limits, you will
get higher fallout; edges of the bell curve and all that.

If your supplier is telling you that parts have failed then it tends to
suggest that they have a reasonable quality system in place. They know the
process and its limits and are therefore testing for those failures. It's
an old but true saying that you can't test in quality, you can only design
for it.

--
DaveN

..ng..

On Thu, 10 Apr 2008 08:42:33 -0700 (PDT), in sci.electronics.design,
rickman <gnuarm@gmail.com> bloviated:

>On Apr 10, 11:26 am, linnix <m...@linnix.info-for.us> wrote:
>> > Anyone have experience with 10 mil via holes and reliability issues?
>> > If you have a problem with an order like this, is it reasonable to use
>> > one panel and reject the rest?
>>
>> As you have figured-out, pushing the process limit could be
>> expensive. We would not go below 16 mil holes, even if we need bigger
>> boards. Are you sure you can't use bigger holes?
>
>Sure, I can use bigger holes. But I can't use bigger pads. It was
>hard enough to make the layout work with 10 mil holes and 24 mil
>pads. This board is very small and defined by the customer's
>requirements. It is a daughter card on an existing product so I have
>no flexibility in size except for extending one end which I have
>already done as much as possible. Even that does not do a lot for the
>density issue since the board is over 5 times longer than it is wide.
>Extending the length more just means I have longer lines to try to
>squeeze through the same bottlenecks around the chips and
>connectors.
>
>I guess I am confused about "process limits". I have seen vendors
>that claim to have capability for hole sizes down to 6 mil. They just
>say that they can't guarantee that the hole will not be plated closed
>which is fine with me. So I don't see where 10 mil holes should be a
>real issue. Did I pick a poor PCB maker? Am I just not grasping the
>realities of PCB manufacturing?

I am looking at a fab right now that is a mix of 10 and 7 mil drilled
vias. Board has 8 BGA and is 2x7" so your process is not in any way
pushing the envelope. If you are getting bad plating in 10mil vias
then the most likely cause is insufficient agitation during the
plating and air bubbles were trapped in the vias. You will need to
section (slice & dice) the failing fabs to confirm whether the plating
is actually thick enough across the whole of the fab. If it is air
bubbles you are probably okay as that usually is batch related. If it
is a function of the vendor skimping on the plating, you are screwed.

That being said, I have no empirical data but there does seem to have
been an increase in the failure rate of commercial fabs in the last
year or two. Usually in the plating of the vias. This is across
several vendors US & Asian.

..k

On Thu, 10 Apr 2008 08:18:41 -0700 (PDT), rickman <gnuarm@gmail.com>
wrote:

>I had some PCBs made with 22 boards per panel (small boards). I
>wanted a single panel for prototypes, but it turned out I could get 6
>panels for only $500 more. This would get me through the first round
>of production if I didn't need any changes. The day the maker was
>supposed to ship them, I got an email saying they had a poor yield and
>only got 116 good boards out of 7 panels vs the 132 I ordered.
>
>So now I have a concern about the quality of the boards. I was told
>the failed boards had problems with the plating in the 10 mil holes I
>used for vias. They claim that the "good" boards have no quality
>issues. My concern is that the vias may be marginal and open once
>they are temperature cycled a bit.
>
>I am not sure how to handle this with the vendor. I guess I could
>just flat out tell them that I am concerned with investing some
>$18,000 building up over 100 boards only to have my customer see
>failures in the field. I don't feel like they have done 100% on this
>since they did not provide the quantity I requested.
>
>They have offered to rebuild the entire set of panels if I am not
>happy with the result, but that would be a week delay. I also don't
>know if they are willing to let me use one of the current panels and
>remake the rest.
>
>Anyone have experience with 10 mil via holes and reliability issues?
>If you have a problem with an order like this, is it reasonable to use
>one panel and reject the rest?

At least they have a good enough quality control that they can spot
this problem. You can have them do a cross section of a good board to
see if the vias look healthy.

Plating systems have to be top-notch to handle small via sizes. If the
board house hasn't kept up on updating their equipment, they will have
problems with small features.

I routinely use 8mil drill with 15mil pads. The pad size is marginal,
but the four board houses I have used never had problems with that via
size for the past 5 to 8 years.

There is one case back in the early 90s where the plated through holes
would disconnect when moderate current (apx 1 amp) p***ed thru the
plated hole after soldering. Before soldering, the PTH handled 10A,
after soldering it would blow around 1A. Most of the byp*** caps
disconnected at power up.

---
Mark

....

"rickman" <gnuarm@gmail.com> wrote in message news:e635a429-c2c9-409c-a284-73e57abac57d@p25g2000hsf.googlegroups.com...

> Anyone have experience with 10 mil via holes and reliability issues?
> If you have a problem with an order like this, is it reasonable to use
> one panel and reject the rest?

I had problems with a vendor once, it was "weak" vias. They were 20mils
though, done on early ROHS process. And yes, baking boards twice
for smd and through-hole did create new broken vias, some immediately
and some later. If I knew about this, I'd toss entire batch right away.
Caused quite a big of grief. I ask my vendor now to leave them a bit
longer in the metalization "soup" and he had to compensate for part of the
damage (tarnished name can't be restored so easily).

You can try baking boards without components and than p***ing them
through tester again, make sure testing current is set to high"ish" level.

Mark

..r.. ..llama..

"qrk" <SpamTrap@spam.net> wrote in message
news:0kjsv31ir5f1470ho8j8ampu79gie96nae@4ax.com...
> On Thu, 10 Apr 2008 08:18:41 -0700 (PDT), rickman <gnuarm@gmail.com>
> wrote:
>
>>I had some PCBs made with 22 boards per panel (small boards). I
>>wanted a single panel for prototypes, but it turned out I could get 6
>>panels for only $500 more. This would get me through the first round
>>of production if I didn't need any changes. The day the maker was
>>supposed to ship them, I got an email saying they had a poor yield and
>>only got 116 good boards out of 7 panels vs the 132 I ordered.
>>
>>So now I have a concern about the quality of the boards. I was told
>>the failed boards had problems with the plating in the 10 mil holes I
>>used for vias. They claim that the "good" boards have no quality
>>issues. My concern is that the vias may be marginal and open once
>>they are temperature cycled a bit.
>>
>>I am not sure how to handle this with the vendor. I guess I could
>>just flat out tell them that I am concerned with investing some
>>$18,000 building up over 100 boards only to have my customer see
>>failures in the field. I don't feel like they have done 100% on this
>>since they did not provide the quantity I requested.
>>
>>They have offered to rebuild the entire set of panels if I am not
>>happy with the result, but that would be a week delay. I also don't
>>know if they are willing to let me use one of the current panels and
>>remake the rest.
>>
>>Anyone have experience with 10 mil via holes and reliability issues?
>>If you have a problem with an order like this, is it reasonable to use
>>one panel and reject the rest?
>
> At least they have a good enough quality control that they can spot
> this problem. You can have them do a cross section of a good board to
> see if the vias look healthy.
>
> Plating systems have to be top-notch to handle small via sizes. If the
> board house hasn't kept up on updating their equipment, they will have
> problems with small features.
>
> I routinely use 8mil drill with 15mil pads. The pad size is marginal,
> but the four board houses I have used never had problems with that via
> size for the past 5 to 8 years.
>
> There is one case back in the early 90s where the plated through holes
> would disconnect when moderate current (apx 1 amp) p***ed thru the
> plated hole after soldering. Before soldering, the PTH handled 10A,
> after soldering it would blow around 1A. Most of the byp*** caps
> disconnected at power up.
>
> ---
> Mark
Hi Mark,
Have you done any PTH vias (0.012"D) that are in SMT solder pads that are
filled either with a non conductive material before the solder is added? I
have done this on a couple of jobs recently and it simplifies layout and the
vias used for thermal flow, let's say six under a DD Pac work great.
What say you?
Harry

..ckm..

On Apr 10, 1:41 pm, "TheM" <DontNeedS...@test.com> wrote:
> "rickman" <gnu...@gmail.com> wrote in messagenews:e635a429-c2c9-409c-a284-73e57abac57d@p25g2000hsf.googlegroups.com...
> > Anyone have experience with 10 mil via holes and reliability issues?
> > If you have a problem with an order like this, is it reasonable to use
> > one panel and reject the rest?
>
> I had problems with a vendor once, it was "weak" vias. They were 20mils
> though, done on early ROHS process. And yes, baking boards twice
> for smd and through-hole did create new broken vias, some immediately
> and some later. If I knew about this, I'd toss entire batch right away.
> Caused quite a big of grief. I ask my vendor now to leave them a bit
> longer in the metalization "soup" and he had to compensate for part of the
> damage (tarnished name can't be restored so easily).
>
> You can try baking boards without components and than p***ing them
> through tester again, make sure testing current is set to high"ish" level.
>
> Mark

Thanks for your suggestion. I thought of that, but I don't have a way
to test the bare boards. Turns out I have four more weeks to order
the panels, so I have some time to evaluate the boards in the
prototypes.

I'm waiting to hear back from the board vendor. But I expect I will
have to bite the bullet on this one and reorder the production panels
from a better supplier. The whole reason I bought so many was that
they were not much more than just buying prototype quantities. So I
knew it was a bit of a risk. Not a big deal now that I have more time
to deal with it. I was mainly worried about the schedule.