Frank: Without knowing what saponifier and it's chemical composition you are
asking about and the particular "affects" you have an interest in, let me
give you some general information on saponifiers and soldermask.
Most saponifiers have a fairly high pH. Due to their highly basic nature if
left on the mask they can start to react and attack the surface of it. This
can lead to moisture absorption even if the saponifier is completely
removed.
If left behind they can also contribute to electrical leakage.
If not thoroughly rinsed they can result in adhesion problems with conformal
coating to the soldermask.
Saponifiers can cause other problems than just with the soldermask. They can
cause corrosion, removal of part markings, attack of various plating
finishes, etc. Due to their low surface tension they can be hard to rinse
completely, resulting in entrapment under low standoff parts.
How did you get 100% saponifier on the boards, how long was it on and how
did you clean them? Are you trying to determine if the integrity of the
board was compromised or is this just a what if question?
Regards
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett WA
425-446-6076
-----Original Message-----
From: Franklin D Asbell [mailto:[log in to unmask]]
Sent: Wednesday, April 16, 2003 7:29 AM
To: [log in to unmask]
Subject: Re: [TN] Saponifiers and no-residue/no-clean fluxes
The casper effect you refer to is caused by incomplete cure of the mask,
moisture or volatiles become entrapped (typically during wave solder but
often exhibiting itself during the post cleaning process...we've seen this
before as well, these boards were baked at low temperature and the "white"
disappears... Don't see this too often now...
As for solder going under the mask and lifting, well thats a pre-cleaning
issue there...without a good surface to bond to the mask is going to lift
with just the slightest stress (heat, force, chemical) applied...
What I was referring to was what affects saponifier may have on solder mask,
specifically, the application of 100% saponifier
Good thoughts...thanks
Franklin
----- Original Message -----
From: Charlie Pitarys <mailto:[log in to unmask]>
To: [log in to unmask] <mailto:[log in to unmask]>
Sent: Wednesday, April 16, 2003 8:39 AM
Subject: Re: [TN] Saponifiers and no-residue/no-clean fluxes
Hi Frank,
Yes there has been some issues off and on in the past.
Yes certain dry film types cannot stand up to saponifiers (no matter who
makes the juice), semi-aqueous solvents and even high pressure spray have
all been the culprit?
However the I believe the majority of problems can be traced back to how
they are processed at the board level.
On LPI type masks the UV cure has a big impact. (testing has been done to
prove this)
Try to rush this step and you will see issues like the green turning ghostly
white. The wash step basically exposed the defect. I have seen hot water
alone cause this "Casper effect".
I believe Steve G. has seen this come and go in the past. A CM will get 10K
boards made and the problem shows up on less then 1%.
I have also seen on one occasion where the mask was lifted by the reflowed
solder wetting up under the mask following the trace and causing it to lift
or bubble. Then when exposed to spray wash it blew it off.(I have pictures)
This is definitely a problem at the board level. Once again the wash step
exposed the defect.
To see the sporadic nature of this problem, search the [TN] archives.
Frank if you have further questions, do not hesitate to call.
Best regards,
Charlie Pitarys
Director of Application Technologies
603.622.2900 X-115
www.kyzen.com
-----Original Message-----
From: Franklin D Asbell [ mailto:[log in to unmask]
<mailto:[log in to unmask]> ]
Sent: Thursday, April 10, 2003 5:40 PM
To: [log in to unmask]
Subject: [TN] Sapponifiers and no-residue/no-clean fluxes
Any of you had experiences with sapponifiers affecting solder mask
integrity?
Franklin
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