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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