-----Original Message-----
From: Stadem, Richard D.
Sent: Thursday, January 04, 2007 10:50 AM
To: 'Peter Swanson'
Subject: RE: [TN] Temporary peelable solder masks
I did not mean to make any cheap shots or imply U.S. manufacturing was
superior. Please do not misunderstand me.
I was simply responding to your comments about why the U.S.
manufacturing tended to have a culture of qualification.
I apologize if it was taken any other way.
Regarding your comment about no-clean not being dirty, it isn't by
itself. But handling and contamination issues are there simply because
circuit boards do come in contact with many surfaces and operator's
hands, lotions, etc. These are typically never removed, as the assembly
is never cleaned. No-clean flux residues do collect moisture and
contaminants over time and it is well-known that this leads to circuit
performance issues with circuitry whose impedance must be tightly
controlled.
Of course, cleaning means cleaning, with verification methods.
-----Original Message-----
From: Peter Swanson [mailto:[log in to unmask]]
Sent: Thursday, January 04, 2007 10:26 AM
To: TechNet E-Mail Forum; Stadem, Richard D.
Subject: RE: [TN] Temporary peelable solder masks
>>> Within the U.S., our industrial, medical, and telecommunications
electronics manufacturing practices were borne primarily from our space
and military electronics applications.
But surely these have diverged widely in the last 20 years.
>>> Therefore it was, is, and (hopefully) will remain a "cover our ass"
culture. Part of this means making sure there are no ionic contaminants
that can react later by themselves or as a result of coming into contact
with other chemicals on the assembly.
No-clean technology does not mean "dirty". In fact, better no-clean than
cleaned poorly.
>>> We prefer to look at it as doing whatever is best to ensure the
long-term reliability of our products using widely accepted standard
methods of qualification and process control.
So does the UK. "Widely accepted" does not just mean the USA.
>>> We strive to do whatever is best for our products, not for our
politicians.
Cheap shot.
I did not start this to get political, nor to imply one approach being
better than another. I was just pointing out some perceived differences.
It would be truly arrogant to imply that quality standards or technical
levels are superior between the USA and UK (and Europe). Ask fellow
TechNetters like Dave Hillman or Doug Pauls, who have visited with us.
By the way, I am an American.
Peter
--------------------------------------------------------
Peter Swanson [log in to unmask]
INTERTRONICS http://www.intertronics.co.uk
Tel: +44 1865 842842 Oxfordshire, England
INTERTRONICS is dedicated to providing quality material, consumable and
equipment solutions to the high technology, high performance assembly
industries, incorporating outstanding levels of technical support and
customer service.
Read our blog! http://www.intertronics.co.uk/blog/blog.htm
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: 04 January 2007 15:44
To: [log in to unmask]
Subject: Re: [TN] Temporary peelable solder masks
Peter,
Within the U.S., our industrial, medical, and telecommunications
electronics manufacturing practices were borne primarily from our space
and military electronics applications. Therefore it was, is, and
(hopefully) will remain a "cover our ass" culture. Part of this means
making sure there are no ionic contaminants that can react later by
themselves or as a result of coming into contact with other chemicals on
the assembly. Examples are no-clean flux residues that react with
conformal coating, epoxies, soldermask (permanent and temporary),
component materials (especially connector bodies) and other materials.
We prefer to look at it as doing whatever is best to ensure the
long-term reliability of our products using widely accepted standard
methods of qualification and process control. We strive to do whatever
is best for our products, not for our politicians. To get an idea of
this, just look at IPC-TM-650 and the IPC Standards. Most of these test
methods and standards were developed within the U.S.
With all of the issues being noted with no-clean flux residues, and with
the ever-increasing use of high-impedance/high frequency circuitry, more
and more post-cleaning of no-clean flux residues is taking place.
Whereas high-volume consumer electronics has migrated out of the U.S.
into third- and fourth-world countries, it stands to reason that
primarily no-clean and no-lead processes are used there. The level of
reliability for cellphones, Ipods, X-box and game systems, sound
systems, and televisions and white goods is less than that typically
boilerplated within the requirements of military, telecomm, medical, and
industrial goods that continue to be built here.
Unfortunately most consumer goods companies do not add any more
reliability requirements than they absolutely have to, and it shows.
This is why we are a "throw-away society".
Regarding the water-soluble maskant, unless there are a lot of holes
that must remain open or free of solder, the maskant is typically
applied after pwb fabrication. Most designs created in the last 5 years
have a very few PTH components at all, perhaps 1 or 2 components that
either cannot withstand the reflow/wave temps or the water wash. So any
temporary masking is done in the DIY mode, and is often done with a
peelable maskant or Kapton tape dot. This is also to prevent
contamination of the wash solutions used to clean the pwbs. Excessive
soluble maskant in the wash has been known to have harmful effects on
the assemblies themselves, especially if they are of the type bearing a
high amount of ammonia.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, January 04, 2007 8:24 AM
To: [log in to unmask]
Subject: Re: [TN] Temporary peelable solder masks
As a yank, at every place I've worked at over the last 19-years has
cleaned everything that's been built (aside from the small amount of
no-clean residues from hand soldered components done at the end of the
main assembly).
Products built range from military hi-rel applications to consumer
electronics (but haven't built any high volume stuff like cell phones,
that's all gone to China). Our customers just wanted things clean...
-Steve Gregory-
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter Swanson
Sent: Thursday, January 04, 2007 4:43 AM
To: [log in to unmask]
Subject: Re: [TN] Temporary peelable solder masks
Cleaning:
My guesstimate is that the UK is 85%+ no-clean after either reflow or
wave solder. In the latter case, the liquid fluxes have very low solids
content these days (~ 2%), therefore low residue.
Cleaning takes place in quite hi-rel applications, or before conformal
coating, although not always in that case either.
No-clean could even be higher than 85% - maybe we'll run a survey here
through the SMART Group to give a better picture.
I suspect that the TechNet and similar forums' membership are not
typical of the assembly industry as a whole. I think it is skewed
towards the hi-rel, more complicated or leading edge end of the
industry, where the issues are more complex and the outcomes more
critical. Therefore people need more help, are prepared and required to
go more in-depth, and cover their behinds with extensive in-house
research and evaluations... and use other resources. Hence, I think that
the percentage of TechNet members who post-solder clean is higher than
the USA market as a whole, or anywhere else. Just an impression.
I also suspect that the profile of electronics assembly in the two
markets are similar, although the US is larger or course - the UK no
longer has any high volume consumer electronics or mobile telephone
manufacture. We have also lost all the major EMS companies like
Celestica, Flextronics, Solectron, Jabil, etc all of whom used to have
big factories here - we have just a few stubs left. We have got a bunch
of medium size EMS companies, automotive electronics, quite a lot of
defence and military, instrumentation, medical, telecom, et al. Maybe
the originator of this thread's company, Dolby, is a good example of
what we have - they make professional digital audio products here. Nigel
is a buddy, by the way.
If you divvy the whole thing up by IPC Class I, II, III - I think the
percentages would be about the same here and there. Cleaning, therefore,
is not necessarily a class issue!
Peter
--------------------------------------------------------
Peter Swanson [log in to unmask]
INTERTRONICS http://www.intertronics.co.uk
Tel: +44 1865 842842 Oxfordshire, England
INTERTRONICS is dedicated to providing quality material, consumable and
equipment solutions to the high technology, high performance assembly
industries, incorporating outstanding levels of technical support and
customer service.
Read our blog! http://www.intertronics.co.uk/blog/blog.htm
-----Original Message-----
From: Dehoyos, Ramon [mailto:[log in to unmask]]
Sent: 03 January 2007 18:26
To: TechNet E-Mail Forum; Peter Swanson
Subject: RE: [TN] Temporary peelable solder masks
There is another option, use of Kapton dots of different sizes.
They peel off rather easily. Peter, are you saying that after fluxing
in the wave solder there is no cleaning either? Or only after reflow?
Regards,
Ramon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter Swanson
Sent: Wednesday, January 03, 2007 11:40 AM
To: [log in to unmask]
Subject: Re: [TN] Temporary peelable solder masks
>>>> If you are washing the board after soldering
I believe that this is quite possibly the bigger distinction between the
UK (& Europe?) and US pcb assembly profiles. We have little or no water
cleaning of fluxes after soldering any more.
I think the ratio of SMT to through hole is certainly on a par between
the two. Maybe even higher here, certainly not lower.
Regards,
Peter
--------------------------------------------------------
Peter Swanson [log in to unmask]
INTERTRONICS http://www.intertronics.co.uk
Tel: +44 1865 842842 Oxfordshire, England
INTERTRONICS is dedicated to providing quality material, consumable and
equipment solutions to the high technology, high performance assembly
industries, incorporating outstanding levels of technical support and
customer service.
Read our blog! http://www.intertronics.co.uk/blog/blog.htm
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Barmuta, Michael
Sent: 03 January 2007 16:26
To: [log in to unmask]
Subject: Re: [TN] Temporary peelable solder masks
Nigel: If you are washing the board after soldering I would recommend
using a water soluble mask. We have used the Lackwerke Peters GmbH
peelable vinyl mask in the past but have moved away from it.
Using water soluble mask eliminates the labor intensity of removing the
peelable style mask. Also depending on how the peelable is used,
configured, applied and cured it doesn't always come off that easily.
This is not aimed at the Peters mask but to peelables in general.
We apply the temporary solder mask at the assembly level. Since we wash
after soldering, water soluble masking materials are used. They are
applied by imaged screen printing, localized liquid dispensing or taping
depending on board design and volume of product. Screen printing is the
most prevalent approach.
I'm not sure why your board fabricator is hesitant to use the peelable
unless they are not set up for doing imaged screening. However it's not
a big leap from doing permanent mask to doing temporary mask. Perhaps
they don't have enough customer requests for this to put in the process.
I can understand why the fabricator may be hesitant to apply the water
soluble mask. If the boards are nor packaged and/or stored correctly it
can start to breakdown and also stick or brick together.
Regards
Michael Barmuta
Staff engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Burtt, Nigel
Sent: Wednesday, January 03, 2007 7:44 AM
To: [log in to unmask]
Subject: Re: [TN] Temporary peelable solder masks
Peter,
I guess in part that is what I am asking. Do US assemblers
more commonly use the in-house/DIY approach rather than have the PCBs
supplied with the masking pre-applied to a supplied (gerber layer?)
pattern. Alternatively I know that some use masking that is removed by a
post-wave-solder cleaning process rather than peelable. Just surprised
that what our suppliers seem to think is not a big problem to provide as
a normal service is apparently not so readily available in USA... Or
maybe it just depends who you ask!
Cheers
Nigel Burtt
Production Engineering Manager
Dolby Laboratories, Inc. - European HQ
Email: mailto:[log in to unmask]
Tel: +44 (0)1793 842132 [direct line with voicemail]
Fax: +44 (0)1793 842101
-----Original Message-----
From: Peter Swanson [mailto:[log in to unmask]]
Sent: 03 January 2007 15:37
To: TechNet E-Mail Forum; Burtt, Nigel
Subject: RE: [TN] Temporary peelable solder masks
Nigel,
You rightly draw the distinction between a) the types of temporary masks
which are pre-applied by screen printing, usually by the pcb fabricator
and b) the temporary masks which are dispensed on by the guys doing the
assembly. They are different.
Whilst it is obviously desirable to have this job done by your fab guy,
as you pointed out, it isn't always straightforward. In particular, I
remember a few years back when the process window on the screenable
materials wasn't very wide, resulting in problems from under/over cure,
removal, etc. Maybe the formulations are more robust today.
It is possible to make the "in-house" dispensable types more appealing.
Dispensing can be by fairly inexpensive robotics. Curing can be quick by
heat or UV. Is this approach an option?
Regards,
Peter
--------------------------------------------------------
Peter Swanson [log in to unmask]
INTERTRONICS http://www.intertronics.co.uk
Tel: +44 1865 842842 Oxfordshire, England
INTERTRONICS is dedicated to providing quality material, consumable and
equipment solutions to the high technology, high performance assembly
industries, incorporating outstanding levels of technical support and
customer service.
Read our blog! http://www.intertronics.co.uk/blog/blog.htm
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of N Burtt
Sent: 03 January 2007 09:27
To: [log in to unmask]
Subject: [TN] Temporary peelable solder masks
I'm being told that these are not widely used in USA, the common types
used here in the UK (Peters and Electramask) not readily available, and
they create packaging and shipping problems... thus US PCB suppliers
reluctant to supply PCBs with peelable masking applied. Is this true?
Now they are by no means a perfect solution to protecting holes on a PCB
during wavesolder, but am not aware of another way of doing so in a
no-clean RoHS process if fixturing can't do it. What do US PCB
assemblers do if pre- applied peelable masking is really not viable?
Other ideas?
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