Techies I thought I would share some info that, I feel, is relevant to this question. Albeit some time ago, my company supplied a dip coating system to a major automotive electronics manufacturer who were using a silicone conformal coating. So what, you might say? Well, we found that, despite an 8 hour bake at around 80DegC, the residual/accumulated moisture "entrapped" into the assembly, was sufficient to kick-over the moisture sensitive coating. So what? Well, this meant that the coating remaining in the dip tank - some 60 litres (15.85 gallons = US Term) - had to be disposed of every 2 weeks (Fortnight = British term!) 3 issues: 1 = Environmental impact in the disposal of 60 litres of product every 2 weeks. 2 = Cost impact of same 3 = How come the bake was not able to eliminate this problem? So - I hope the new document might yield some recommendation as to the minimum baking time to avoid this phenomenon. Thinks - maybe I need to spell that Fenomenon rather than phenomenon....? [thinks - I am somewhere framed on the walls of Mr Pauls....] (Dewey - that rhymes, sorry, rimes? Excuse me, Rymes?) Ah! What the heck. Graham Naisbitt On 28 Aug 2008, at 17:45, Joe Macko wrote: > Denny, > > We have always treated FR4 PCBs as moistures sensitive and baked them > out before reflow to be safe. Everyone has there own idea about bake > out > time and temperature and most CMs do consider the PCB moisture > sensitive. We bake for 5-6 hrs at 110 C. Boards are generally used > within 2-weeks of bake out. > > Best Regards, > -joe > > > > "This e-mail and any attachments are solely for the use of the > addressee and may contain L-3 proprietary information that may also > be defined as U.S. Government export controlled technical data. If > you are an unintended recipient of this e-mail, use, disclosure or > distribution of its content is prohibited. Please notify the sender > by return e-mail and immediately delete this message." > > From: TechNet [mailto:[log in to unmask]] On Behalf Of Dennis Fritz > Sent: Wednesday, August 27, 2008 7:10 AM > To: [log in to unmask] > Subject: Re: [TN] Moisture in PCB Assemblies > > Bill, > > There has been some speculation that with the higher assembly > temperatures of lead-free, that PCBs should have a Moisture > Sensitivity > Level - just like the components being mounted on them.? However, I > don't think JEDEC will step up to the plate to adopt anything to do > with > PCBs.? So, it would be the job of the IPC to do that.? > > With the upcoming IPC meeting in late September, Schaumburg, > Illionois, > now would be a good time to debate the need for circuit board MSL > levels. As pointed out, the group working on Storage and Handling will > go a long way, but moisture absorbsion propensity is also a property > of > the resin/glass composition of the board.? > > How about it TechNetters? > > Denny Fritz > MacDermid, Inc. > > > -----Original Message----- > From: [log in to unmask] > To: [log in to unmask] > Sent: Tue, 26 Aug 2008 7:19 pm > Subject: [TN] Moisture in PCB Assemblies > > > > Fellow TechNetters:? I was asked a question by a valued customer if > there is any > other references made to moisture in raw PCBs and populated assemblies > other > than the J-STD-033 and also the IPC rework standards.? I've looked in > IPC > Standards I have on file however I could not find any > references/guidlelines at > all.? Can anyone out there shed some light on this??? > > I thank you folks in advance for your efforts on my behalf. > > Bill Black > Medco > Q.A. Manager > Tel:? 631-667-9699 > > E-Mail:? 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