If you do attempt to remove the solder mask (with some type
of mask stripper) make sure that you monitor your process well.
Most mask strippers will attack the butter coat on the laminate
and give you the appearance of dry weave or weave exposure even on
2 layer product. Just ensure that the stripper is in control and
it should perform and remove your solder mask,

Thanks
Ted Gaines
Ht&D Cam SERVICE
Voice - 775-599-6720
Fax  -  775-924-3966

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jeffrey Bush
Sent: Wednesday, September 15, 2004 8:02 AM
To: [log in to unmask]
Subject: Re: [TN] LPI Solder Mask on Class 3 Product; Can it be removed?


Chemical exist for complete removal of soldermask and inks from PCB.
The chemical will vary if the material (both mask and lettersceen) is an
acrylate or epoxy system.  The acrylates remove easier with little
effect on the laminate surface is controlled well.  The solderable
finish will need to be re-applied also since these chemistries will
effect the final finish and should be removed before stripping the mask.
Electrolytic Ni/Au may survive but ENIG will not and could be a loss due
the inability to recoat these finishes.

Laser is a good (somewhat costly) option when you have mask on the land
areas, but is not effective for the global removal of mask from the
surface.  Rework of mask by recoating or manual touch-up is acceptable
as long as the resulting PCB meet the end product performance
conditions.  Cosmetic issues will be an issues depending on your
customer and you ability to rework.



Jeffrey Bush
Director, Quality Assurance and Technical Support

                          76 Technology Drive - POB 1890
                             Brattleboro, Vermont 05302-1890
                                Tel. 802.257.4571.21 Fax. 802.257.0011
                                    [log in to unmask]
                              http://www.vtcircuits.com



-----Original Message-----
From: - Bogert [mailto:[log in to unmask]]
Sent: Wednesday, September 15, 2004 5:45 AM
To: [log in to unmask]
Subject: [TN] LPI Solder Mask on Class 3 Product; Can it be removed?


September 15, 2004

Does anyone know of a method to remove fully cured LPI solder mask
(IPC-SM-840, Class 3 product) from an FR-4 PWB without damaging the PWB
or otherwise creating possible condition for growing dendrites?

If chemicals can be used, are they non-conductive?

If solder mask needs to be touched up because of missing solder mask,
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how do folks do this?

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