Hi John; I think the questions is... what are you asking the mask to do? I don't think you are asking it to be a "soldermask". Is it an anti-humidity coating, a dielectric coating, an environmental coating, an anti-corrosion coating, etc. Work with your customer to try and clearly define what are the specific requirements and to what level of performance are they needed for the finished product. It may be difficult to nail down, because they may not know, but you will be in a much better position to define which path to take. It may be conformal coating, burying circuitry in additional layers, multiple masks and adhesion promoters, a different final plating finish, encapsulation/potting, etc. Right now you are just trying to be a good supplier offering to help in any way you can but I don't think you have all the information you need to help them with the correct solution. Good luck. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of John Parsons Sent: Wednesday, November 17, 2004 12:55 PM To: [log in to unmask] Subject: Re: [TN] Alternatives to Conformal Coating? Jean-Francois, If it is a bad idea then you are not alone. Another on the list suggested it and it is something we discussed here as well but I forgot to add it to the list. What we need to do is compare the cost of building a multilayer board against the increased cost of doing it right with conformal coating. Thanks John -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Bissonnette, Jean-Francois Sent: Wednesday, November 17, 2004 11:49 AM To: [log in to unmask] Subject: Re: [TN] Alternatives to Conformal Coating? Well not knowing exactly if it was done before or even if this feasable, my answer to that may have a place in the wall of shame or just be interesting. This would not protect the components nor the soldered connection but it would protect all the traces. Would it be possible to keep the connections in the internal layer, leaving both external layers with only the lands to solder the components on? (ready to blush in shame) JF -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of John Parsons Sent: Wednesday, November 17, 2004 2:08 PM To: [log in to unmask] Subject: [TN] Alternatives to Conformal Coating? Greetings all, We are a fab shop and are looking for a solution to a problem being experienced by one of our customers. They have a board which resides in a somewhat hostile environment - steam/salt water vapour - board carries 20Amp current - susceptible to multiple thermal excursions which put further stress on the unit The problem, as one might expect, is that the soldermask is not man enough for the job. Some units have exhibited significant solder mask flaking from the conductors after as little as 4 hours of operation. FYI, board is double sided with 3oz base Cu. The product is currently only in the prototype stage but production volumes are expected to be in the 100,000-250,000 units annually. We have proposed the obvious solution of utilizing a conformal coating post assy but that is an option they would initially prefer to avoid due to the inherent costs involved. They would like us to first exhaust any possibility that the problem can be averted from the pcb fabrication level. I should also mention that the expected lifespan of the unit is a maximum of 1000hrs and likely only several hundred hours. Some options that have been discussed are; (in no particular order of likelihood to succeed of fail!) - multiple coating of soldermask - micro etch of copper prior to mask application (currently pumice scrub) - conductor pacification with oxide alternative. If this does not provide additional bite for the mask it may provide additional protection from corrosion once the mask has pealed off. Any ideas from the lot of you? Are there properties to specialty solder masks which might be beneficial in this application? Any options to conformal coating?? 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