Obviously some water wash pastes clean off more completely than others, but
you can not assume that all wash additives improve cleaning of all fluxes.
Some water wash fluxes will clean worse - not better - if inappropriate wash
additives are used.
= make sure your proposed cleaner supplier has documented trials of his
various solutions with your candidate paste/flux type.
You will need strong procedures to make sure that you don't mix paste types
(and associated flux core solder wire, repair fluxes etc) with types from
adjacent lines. Unwashed water sol flux is not good, but water washed no
clean can also be bad news.
You will have to make sure the design is suited to water washing: no water
traps, capillary opportunities, all components suited etc. or you will see
them back just as quickly as if using the wrong materials!
Regards
Mike Fenner
Indium Corporation
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Peck
Sent: Thursday, November 20, 2008 2:07 AM
To: [log in to unmask]
Subject: Re: [TN] WS solder paste
Ioan:
I'd like to reinforce Doug Pauls' comment on cleaning water
soluble?residues.
From?a rework perspective, please don't even let?water soluble flux into the
rework area unless the the PCBs can be power-washed after rework. Have seen
some awful field returns reworked with water soluble flux that might have
been hand-cleaned, at best.
Good luck.
Doug Peck
-----Original Message-----
From: Douglas O. Pauls <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, 19 Nov 2008 11:21 am
Subject: Re: [TN] WS solder paste
Ioan,
In addition to the other suggestions given so far, do not EVER EVER EVER
believe the salesman when they tell you that water soluble flux can be
cleaned using water alone. It can't. And if they tell you that tap water
cleaning works fine, throw them out the door.
Most of the cleaning chemical vendors, such as Kyzen, Petroferm, Zestron,
can give you good data on what materials work best to ensure cleaning
under low standoff parts.
Doug Pauls
Rockwell Collins
Ioan Tempea <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
11/18/2008 09:44 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Ioan Tempea <[log in to unmask]>
To
[log in to unmask]
cc
Subject
[TN] WS solder paste
Dear Technos,
After having worked for years with no-clean pastes, I need now to
evaluate water soluble. Concerning both SnPb and lead-free, what would
be your short list to start qualifications?
We are a CEM, so the paste needs to be very versatile, so it can give
the best performance (compromise) for inconsistent designs. In this
world we need to print everyday a wide range of designs like 20mil fine
pitch pads with widths from 9 to 15 mils, 0603s with pad gaps between 20
and 35 mils, etc., so I guess most of you understand what I mean by
versatile ;-)
I assume off-line answers would be appropriate, so please do not
hesitate...
Thank you,
Ioan
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