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expedite drying of latex mask

Eric Soderberg

#3249

expedite drying of latex mask | 21 August, 2000

Currently use Hysol TS300 latex mask and need to explore alternative methods of drying the mask. The mask is applied with a Asymtek Century Dispenser and placed on drying shelves. Air dry is dependent on temperature/humidity. Tried all the UV masks on the marked as well as latex masked with amonia which people here refuse to use. UV dries very quickly but is extreemly difficult to remove after waveflow. The TS300 just brushes off within 20 seconds of waveflow. May have to go to a heated chamber but would like other ideas.

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#3250

Re: expedite drying of latex mask | 21 August, 2000

Eric: I�ll pass on the uV and ammonia, also. Thoughts are: 1 You�re correct that the temperature/humidity mix can be a big driver to latex peelable solder mask cure time, but don�t overlook material thickness. Dispensers put material in a very thick layer. Baking a thick layer of the mask seems to make the problem worse, because the mask skins over (cures on the outside) and hinders acceleration of cure times. So, another variable in the process seems to be mask thickness. 2 Mask should be applied in as thin a layer as possible. [We tell people to put-down peelable about as thick as nail polish � it�s getting easier and easier to tell guys that, nowadays] 3 Check your assumption about curing processes as you move through the product evaluation. Humidity (light air), and heat cures could be part of your evaluation matrix. 4 Consider printing your mask, but in doing this, don�t forget to evaluate the ability of the mask to "stand-up" under solder heat cycles. Some peelables get crusty after their first heat cycle. 5 Major types of peelable solder mask types are: * Oven thermal cure peelable - 1 or 2 part PVC (I think), the type screened on by your PCB supplier, who may also use it as a plating or HASL mask. * Ambient air dry peelable - latex (high pH) or synthetic latex (neutral pH and probably preferable). Dispensed. * Ambient air dry soluble - water (warm) or even solvent soluble types. Dispensed or screened/stenciled. * Light cure peelable * Light cure water soluble The light cures may come in long wave UV, or a combination of UV/ visible light cure which is often faster. Both can be dispensed or screened/stenciled. 6 A while ago, Stu Leech posted something on SMTnet about was looking for beta sites for a drying machine.

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