Enjoy steam weather. Repot back board solderability test result after expose to the weather. Full exposure at your trip duration :0
--------------------------
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----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Fri Aug 01 10:47:16 2008
Subject: Re: [TN] Solder Paste with craters.
ROFL
I am off to Singapore tonight so may not be on the link much next
week.......enjoy the break.......8-)
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Friday, August 01, 2008 6:25 AM
To: [log in to unmask]
Subject: Re: [TN] Solder Paste with craters.
But then he found out he was soldering to ENIG in John 11:35, and I
quote: Jesus wept.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Thursday, July 31, 2008 6:23 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Paste with craters.
Not sooooo
All you need is a good laser interferometer, a sense of humor and plenty
of time........
Although you are close Dewey - the first reference I have ever found is
Isaiah 41 vs 7: which says and I quote:
" It is ready for the soldering"
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey
(EHCOE)
Sent: Thursday, July 31, 2008 2:30 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Paste with craters.
Yeah, but those clay tablets and papyrus reeds are hard to scan.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Thursday, July 31, 2008 2:27 PM
To: [log in to unmask]
Subject: Re: [TN] Solder Paste with craters.
Mike is too young, and he is english..............
????????????
You didn't know? Most reports, as far as I remember, were american.
IBM,
ESL, HERAUS, duPONT, Honeywell, etc
Inge
----- Original Message -----
From: "John Burke" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, July 31, 2008 2:14 PM
Subject: Re: [TN] Solder Paste with craters.
> If you want REALLY old papers on Rheology Mike Fenner will
have/remember
> them - sorry Mike!!...........NOT
>
>
>
> John Burke
>
> (408) 515 4992
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
> Sent: Thursday, July 31, 2008 1:52 PM
> To: [log in to unmask]
> Subject: Re: [TN] Solder Paste with craters.
>
> Leif Erik,
>
> seems as the focus is now on the stencil. Good, because this may be
the
> red
> thread. Imagine the squeege has just passed and the extremly small
laser
> cut
>
> holes are filled with your paste. Next, the stencil is ready to
separate
> from the board. What happens? I guess the rather rough metal walls are
> little unwilling to let go the paste, while the paste has already
> established a grip on the ENIG pad through surface wetting and
adhesion
> forces. The later one wins over the adhesion from the stencil walls
> (otherwise, there had been no prints). However, the adhesion from the
> walls
> will expand or elongate the paste body for fractions of a second. But
the
> true volume is constant still, isn't it. Then a compensation must be
done,
> namely, the middle of the paste body must sink. You get a small , what
> shall
>
> I call it, a inward bend instead of a flat paste surface. When the the
> stencil wall adhesion is overcome, the paste glides backward and
leaves
> the
> stencil, but not as a perfect cube or cylinder, but more like a
volcano
> crater. What happens next is all dependent on the rheology of the
paste.
> We
> found that pastes with little lower viscosity never gave any bubbles,
> while
> 'thicker' or 'drier' pastes had a tendency to build a 'depression' in
the
> middle. This was only seen for very small apertures. In our case, we
> could
> ignore the phenomenon, didn't have any negative impact. We learned
this
> all
>
> from our thickfilm printing guy. Wished I had saved all hundreds of
> technical report from the 60s and 70s (it was the time we had people
who
> knew about rheology) but they are gone. Later generations thought this
old
> stuff was useless, a lot not even stored for the IT age... Trike Man
may
> still have something hidden in his drawers,,,
>
> Inge
>
>
>
> ----- Original Message -----
> From: "Inge" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, July 30, 2008 2:21 PM
> Subject: Re: [TN] Solder Paste with craters.
>
>
>> Do you use a thick stencil?
>> Have you tried to slow down the stencil lift speed?
>>
>> Inge
>>
>>
>> ----- Original Message -----
>> From: "Leif Erik Laerum" <[log in to unmask]>
>> To: <[log in to unmask]>
>> Sent: Wednesday, July 30, 2008 1:56 PM
>> Subject: Re: [TN] Solder Paste with craters.
>>
>>
>>> Thank you everyone for contributing. Especially you, Richard.
>>>
>>> First of all these are NOT via in cap boards and we are using FR4.
Been
>>> there done that....
>>>
>>> Most of the items brought up by Richard we do have established
processes
>>> for. These are according to the recommendations of the solder
vendor,
>>> but
>
>>> if others feel differently, please chime in.
>>> We log the solder used for each batch and the Date of Manufacture
for
>>> this. We typically do not accept a batch of solder that is older
than 3
>>> mts. This is so that we do not end up with too much out of date
solder
>>> at
>
>>> the end.
>>>
>>> - Solder is brought out of the fridge minimum 12 hours before use.
>>> - We set a time limit that solder must can be stored out of the
fridge a
>>> maximum of 3 mts. Practically this ends up around 1 month max.
>>> - We do reuse solder that has been on the screen for up to two
weeks.
>>> Then we throw it out.
>>> - We never put solder back in the fridge.
>>> - We are evaluating new suppliers of solder at the moment. We have
not
>>> audited the currents supplier, but that is a good idea. We always
get
>>> the
>
>>> solder couriered locally and in a cool container so I do not
have
>>> any evidence that would lead me to put this on the solder vendor,
>>> but.....
>>> - As our process works boards sit no longer than 1 hour with solder.
>>> Usually much shorter than that.
>>> - We are using Type 5 solder actually.
>>> - All misprints go though the wash before it is reprinted.
>>> - We use a DEK 248 that is not as automatic as I would like and some
of
>>> the issues we see are due to this repeatability problem, but from
the
>>> data I have gathered, this is not the cause of the solder fines and
>>> craters.
>>> - A Solder AOI would be nice. We do not have one of these (yet???)
>>> - There could be an issue with too much solder. We are going to
reduce
>>> apertures some. There is some evidence of excessive solder.
>>> - I am going to experiment with slowing down the print separation
speed.
>>> Good point.
>>>
>>> Thx.
>>>
>>> Leif Erik Laerum
>>> Quality Assurance Manager
>>> Texas Memory Systems
>>> [log in to unmask]
>>> Tel: (713) 266-3200 x468
>>> www.texmemsys.com
>>>
>>>
>>>
>>> Inge wrote:
>>>> Hi Leif, you've just listened to His Master's Voice.
>>>> You should take off your cap, when you speak to Richard Stadem.
>>>> Impressive! I begin to feel that there are two exceptional stars at
TN.
>>>> Steve...we already knew
>>>> Richard...a supernova
>>>>
>>>> Inge
>>>>
>>>> Gah...my example was not very clever...a supernova is bright just
for
>>>> a
>
>>>> short time...hmmm...a red giant then? hmmm...or a white
>>>> dwarf...hm...none of them very striking....hmm....shining like
>>>> Betelgeuse...hmm.....maybe Master Whittaker can give a hand?
>>>>
>>>>
>>>> ----- Original Message ----- From: "Stadem, Richard D."
>>>> <[log in to unmask]>
>>>> To: <[log in to unmask]>
>>>> Sent: Wednesday, July 30, 2008 6:53 AM
>>>> Subject: Re: [TN] Solder Paste with craters.
>>>>
>>>>
>>>> Hi, Leif
>>>> Send your pictures to [log in to unmask]
>>>>
>>>> Can you tell me what solder paste it is you are using? How was it
>>>> qualified for use?
>>>>
>>>> Here are just some of the questions you need to ask yourself in
order
>>>> to
>>>> determine why you have an issue with solder fines:
>>>> Do you have a good documented solder paste handling procedure? How
is
>>>> the paste handled, from vendor or distributor to your factory? When
was
>>>> the last time you stopped in at the distributor to verify their
stock
>>>> is
>>>> being rotated and is kept refrigerated immediately upon receipt
from
>>>> the
>>>> factory? How often do they turn the packages upside down to prevent
>>>> flux
>>>> separation? Are they a certified distributor who will pass on to
you a
>>>> lot recall notice from your solder paste vendor if there is a known
bad
>>>> lot?
>>>> How long is the paste allowed to sit out on the stencil and how
many
>>>> times can a line of paste on the stencil be sheared (printed back
and
>>>> forth) before it is removed and replenished with fresh paste? Are
the
>>>> operators allowed to scrape up the unused paste on the stencil and
>>>> re-deposit it into a jar for re-use later? Is the jar or tube of
solder
>>>> paste, once removed from refrigeration, allowed to set for two to
four
>>>> hours (depending on paste vendor and paste type) to reach room
>>>> temperature prior to printing? Once removed from the refrigerator,
is
>>>> unused solder paste allowed to be put back in the refrigerator? Are
you
>>>> using Type 4 paste or Type 3? How good is the printer setup, ie,
the
>>>> repeatability of the registration of the stencil to the PWB? Are
you
>>>> performing some type of aperture reduction on all pads in general
and
>>>> at
>>>> least a 50% reduction on large belly pads to prevent solder fines
from
>>>> being printed onto the board? If a board is misprinted, does the
>>>> operator know better than to simply wipe off the board (embedding
the
>>>> paste into every space between the edges of the pads and the
>>>> soldermask,
>>>> into every small via, into every through hole, etc.) but is there a
>>>> documented procedure detailing how the misprinted board is to be
>>>> cleaned
>>>> to prevent this? How is the solder paste packaged, jar or tube?
(Tubes
>>>> prevent a much larger volume of paste from being exposed to air and
>>>> humidity, and also help prevent re-use of solder paste that has
been
>>>> out
>>>> for awhile). Do you perform a good solder paste print inspection
using
>>>> a
>>>> 3d AOI or some other type of automated inspection, and do you use
the
>>>> data from this inspection process to detect (real-time) paste
defect
>>>> trends and react to them with corrective actions?
>>>>
>>>> Sorry to ask so many questions, but all of these can contribute to
>>>> fines, and there are many more factors that can cause them.
>>>>
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Leif Erik
Laerum
>>>> Sent: Wednesday, July 30, 2008 8:29 AM
>>>> To: [log in to unmask]
>>>> Subject: [TN] Solder Paste with craters.
>>>>
>>>> Technetters,
>>>>
>>>> We are having an issue with solder fines on our lead free boards.
We
>>>> are
>>>> using SAC305 WS and no nitrogen. I noticed that our boards have
craters
>>>> in the paste on the pads after being printed. Not all pads are
>>>> deposited
>>>> this way, but maybe 25%. These craters have an air bubble in them.
The
>>>> bubbles usually burst before the boards goes into the P&P, but the
>>>> crater stays. The screening process is exactly the same for leaded
and
>>>> unleaded paste. The leaded paste does not behave this way. Could
these
>>>> craters be a symptom of the cause of the solder fines? Anyone have
any
>>>> experience with this?
>>>>
>>>> How do I go about posting pictures to stevezeva.homestead.com?.
>>>>
>>>>
>>>> --
>>>> Leif Erik Laerum
>>>> Quality Assurance Manager
>>>> Texas Memory Systems
>>>> [log in to unmask]
>>>> Tel: (713) 266-3200 x468
>>>> www.texmemsys.com
>>>>
>>>> ---------------------------------------------------
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