John: If they can't define their requirements, my fear would be the "solution" that is chosen from the various proposals would be based on the lowest cost and not on performance. So the chosen "solution" may not truly be the "correct" solution. Then they have to start all over to find the right one. Major PIA and time consuming. If it's just a case of corrosion of exposed copper circuitry, then you may want to consider an ENIG finish of all the circuitry. It would provide complete encapsulation of the circuits leaving no exposed copper. This may give you sufficient protection if use life is only in the hundreds of hours. However for this product to be successful I think it's probably more than just the copper corrosion issue that needs addressing. Another possibility is if it's a soldermask performance problem you might want to consider an older style two component full epoxy screened thermal mask such as PC401, Taiyo and Tamura products. Based on their polymer structure and type of catalyzing agents, the cured properties of these are very good in electrical and environmental performance. I don't know if the 401 is still around but I'll bet the other two are. If it was my product I would build it as a plain low cost double sided board, populate it then encapsulate or pot it with epoxy. That way I think I'd be confident it would work as designed every time. However in our current atmosphere of zealous desire to build the cheapest product possible, damn the quality, they probably don't want to spend the additional pennies. Regards Michael Barmuta Staff Engineer Fluke Corp. Everett WA 425-446-6076 -----Original Message----- From: John Parsons [mailto:[log in to unmask]] Sent: Wednesday, November 17, 2004 1:44 PM To: [log in to unmask] Subject: Re: [TN] Alternatives to Conformal Coating? Mike, Good advice, thanks. True enough, at this stage I don't have a concrete answer to the question you posed. As you elude, I suspect that neither would the customer. I got the impression from the meeting I had this morning with the subcontract design house that the answer may depend on the cost of the various "solutions" we come up with. The initial concern seems to be that once the solder mask starts to flake of the conductors that the bare copper is now susceptible to corrosion which in time would compromise the performance of the device. The route we may have to follow is just as I started to outline in my original post. I was just hoping that there may be some "magic" answer to the problem that we had not heard of. Regards John -----Original Message----- From: Barmuta, Mike [mailto:[log in to unmask]] Sent: Wednesday, November 17, 2004 1:27 PM To: 'TechNet E-Mail Forum'; 'John Parsons' Cc: Barmuta, Mike Subject: RE: [TN] Alternatives to Conformal Coating? 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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