Marie:
It is important to also re- mention the fact that the liquid masking
is more than likely conductive. According to the manufacturer of the masking
we use he adds metals so it does not charge up and create ESD problems. Use
a Ohm meter and check between two close points on the masking and see if it
is conductive. They can be a high resistivity short, in the low mega ohms.
Shorts are really bad in electronics. Water soluble masking is a good
alternative to reduce cycle time.
Regards,
Ramon
> -----Original Message-----
> From: d. terstegge [SMTP:[log in to unmask]]
> Sent: Thursday, September 04, 2003 7:50 AM
> To: [log in to unmask]
> Subject: Re: [TN] Liquid Mask
>
> Hi Marie,
>
> To my opinion Brian is right, but also I believe he may forget about
> the fact that you need to be competitive. When you use a material that's
> designed to leave only harmless residues, you should be relatively safe.
> If your products need to have high reliability, or if they need to
> operate in a humid atmosphere I still wouldn't leave the material on the
> board, but for other products it seems to me it could very well be
> acceptable. I mean why would you strive for a cleanliness level that
> guarantees 30 years lifetime if the product will be thrown away in 3
> years anyway ?
>
> Daan Terstegge
> Thales Communications
> Unclassified mail
> Personal Website: http://www.smtinfo.net
>
> >>> [log in to unmask] 09/04/03 12:54pm >>>
> No way should anything, designed to be temporary, become permanent.
> Even
> residues, after peeling, can be dangerous unless meticulously removed.
> Donkey's years ago, I took a 10 cm x 10 cm board which had been
> meticulously cleaned to near-zero ionic contamination. I then coated
> it
> entirely on one side with a layer of peelable mask (and I tried it
> with
> about 8 different makes). I allowed the mask to dry 24 hours, to be
> sure
> that all volatiles had gone. I then carefully peeled off every visible
> trace of the mask and done ionic contamination tests on each board. In
> EVERY case, the ionic contamination had risen by some degree, mostly
> to
> a quite dangerous level (exact figures lost in the mists of time). If
> the invisible residues will do this, just imagine what visible
> residues
> will do.
>
> My answer is a categorical NO. In fact, I would go farther: peelable
> masks should never be used in a "no-clean" situation (or after
> cleaning)
> where quality and reliability are criteria to be respected (this will,
> no doubt, hurt some, but it is my belief).
>
> Brian
>
> Dobbs, Marie wrote:
> > I am looking for some feedback. We use Techform Liquid solder mask
> > (peel able) to cover PTH on our PCA's.
> > We also use this Mask as a "Tacking" mechanism to hold Loose Loaded
> > (unsecured/not bent) components on the top side of the board. After
> the
> > mask dries, we take it off the board. This is a Non-Value added
> > activity that I would like to eliminate. I want to leave the dried
> > masking on the board.
> > My question is. Can I leave it on the board? Will it affect the
> long
> > term function of the board? Do any of you use this, or do this?
> Any
> > input is appreciated.
> > Thanks
> > Marie
> >
> >
> > Marie A. Dobbs
> > Training and Development Specialist
> > Tyco Safety Products
> > 100 Technology Drive
> > Westminster, MA 01473
> > Phone: 1-978-731-6827
> > Fax: 1-978-731-6950
> > email: [log in to unmask]
> >
> >
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