Question: what is peelable mask designed for? As a mask? Or as adhesive
to tack the components? The thickness would be different as the
application differs. As mask, you would have open access for "dry"
(volatile diffusion to the surface is more readily=shorter diffusion
distance), as adhesives, the access to the surface is minimum
(otherwise, you would not tack it down... If the outside is dry and
block the inside liquid ... Let's just not think about it...zzzzzz).
Use some material outside of its design intend required good
understanding and experimental verification. Otherwise, use at your own
risk.... My 1.39 cents.
jk
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of d. terstegge
>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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