Plasma would be the best, however, you need to know your process window if you do not coat the board right after the plasma clean. It depend upon your cleanroom condition, the process window can be from 1 hr to 48 hr (good 10,000 class cleanroom with a bit on the dry side should be no problem for 6-8 hr... I used to set limit for 4 hour only - safety factor of 2 for me to get a good night sleep). You need to do surface tension test to find out. Joyce Koo Materials Researcher - Materials Interconnect Lab Research In Motion Limited Office: (519) 888-7465 79945 Mobile: (226) 220-4760 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls Sent: Thursday, February 14, 2013 11:05 AM To: [log in to unmask] Subject: Re: [TN] Conformal Coat Adhesion to Gloss Solder Mask Good morning Kevin, A couple of questions to help refine the response. 1. Is the solder mask a dry film or a liquid photoimageable? I suspect the latter since not many dry film masks are glossy. 2. Have you tested the surface energy of the mask on lot to lot to look for variations? It is a simple way to look for lot to lot variations in mask cure. Lots of asian suppliers are unaware that as their UV bulbs for mask imaging age, they drop in output and so they run them far longer than they should. The result is a mask with inconsistent properties from lot to lot. If your boards are being produced in the same facility across multiple fab lines, you might also get line to line variation. 3. What quality IPA are you using? The cheaper brands of IPA often have lots of other schmutz in it. Could be leaving a residue. 4. Are you removing masking after cure, or after tack-free but prior to cure? Can affect how much coating delam you get. I recommend prior to cure so that you can do minor touch up before cure. I partially agree with Wayne that plasma may be a good remedial method for stuff you have in house. Even the briefest of exposures will take surface energies above 60 dynes/cm. But, if you have solder mask that is not completely or adequately cured, then it might have sucked in other process chemicals along the way which then can leach out, especially with solvents that normally go with urethanes, and can interfere with adhesion. Plasma would not really address that absorption problem. Doug Pauls From: "Glidden, Kevin" <[log in to unmask]> To: <[log in to unmask]> Date: 02/14/2013 08:32 AM Subject: [TN] Conformal Coat Adhesion to Gloss Solder Mask Sent by: TechNet <[log in to unmask]> Hi everyone, We have a PCB that is using a gloss soldermask, and we are having extreme difficulty getting urethane conformal coating to adhere. We use this same soldermask on many PCBs, but only this one particular PCB gives us issues. It has occurred for some time, across multiple lots of PCBs. We do pre-clean all PCBs with IPA and DI water just prior to coating. This is just a light surface clean just to remove any fingerprints or whatever contaminants might be introduced between post solder cleaning, through e-test, and then masking. I think much of the issue for this particular PCB is due to geometry. The PCB is small and has large masked areas- a few dots and all around the perimeter. When the masking is removed, all the coating flakes off. Ultimately, converting this PCB to matte finish is my goal, but I have many PCBs in stock to use up. HDBK-830 states no primer is known to be needed for urethanes. Is anyone out there using primers for urethanes, and would you care to recommend one? What about alternate methods to roughen the gloss surface? I am thinking perhaps if the PCB supplier could somehow dull the finish with an acid etch, or possibly light grit-blast internally? Just looking for ideas. Thanks, Kevin Glidden Mfg Engineer Astronics Luminescent Systems Inc. ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. 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