January 10, 2008
One lessons learned item to be aware of is if the liquid mask is the peel
off type and you use it to mask electrical socket contacts on connectors or
for electrical socket sockets, sometimes some residue winds up inside the
contact and when folks try to use tools, etc. to remove the residual
material, they can spread the electrical contact causing a potential
intermittent electrical connection when the mating connector is installed or
when a component is installed in the socket.
>From: David Greenman <[log in to unmask]>
>Reply-To: TechNet E-Mail Forum <[log in to unmask]>, David
>Greenman <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: [TN] Coating
>Date: Thu, 10 Jan 2008 11:21:14 -0000
>
>Two other things to watch if using natural latex masking compound with
>conformal coating.
>
>Do not try and cure latex above 50C as you will end up with a sticky mess
>on
>the board, that is hard to remove.
>
>If the conformal coating you are using is a thermal cross linking silicone,
>the masking material could inhibit curing of the coating, no matter how
>much
>heat you put in.
>
>
>
>Best Regards
>
>David Greenman
>
>Managing Director
>
>HumiSeal Europe Ltd
>
>A British Manufacturer : Part of Chase Specialty Coatings
>
>
>
>[log in to unmask]
>
>www.humiseal.eu
>
>www.chasespecialtycoatings.com
>
>
>
>==========================================
>
>
>
>HumiSeal Europe Ltd
>
>Registered in England & Wales No : 1480710
>
>Registered Office : Albany Park, Frimley Road, Camberley, Surrey, GU16 7PH
>
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Thayer, Wayne
>Sent: 09 January 2008 23:24
>To: [log in to unmask]
>Subject: Re: [TN] Coating
>
>We have lots of experience with the peelable masks. They are pretty
>inert and leave no detectable residue provided they peel off cleanly.
>There are two significant problems:
>
>1. In order to peel off cleanly, they need to be put on pretty
>thick--like 0.5mm thick. At this thickness, your resolution is not so
>good, and it interferes with the solder stencil, so you need a stencil
>cutout over that area and need to work at it to get decent
>printing--maybe even hand squeegee the paste in.
>2. If you get them hot for too long, they embrittle. Then you are in
>for some serious problems getting them off cleanly. The thinner you put
>them on, the less temperature/time they need to get this way.
>
>We've also used water soluble. These work pretty good unless you are
>trying to protect gold wirebond pads: The flux chemistry goes through
>them pretty easily, but the solder won't wet the area. I don't have
>data for contamination levels after removal, but we didn't have a
>problem during the time we used them. Of course, these won't survive a
>cleaning process.
>
>Wayne Thayer
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
>Sent: Wednesday, January 09, 2008 5:41 PM
>To: [log in to unmask]
>Subject: Re: [TN] Coating
>
>Yannick,
>We don't do that here, but when I was at Nortel we did quite bit. You
>need to make sure the temporary solder mask is not going to cause
>corrosion, especially if it is hard to remove and will be leaving bits
>and pieces on your boards!
>Bev
>RIM
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Yannick Brisson
>Sent: Wednesday, January 09, 2008 4:57 PM
>To: [log in to unmask]
>Subject: [TN] Coating
>
>Hi,
>
> I'm wondering what you guys do for coating a PCB with area to mask?
>do you use something special, Do you do your jigg yourself, or do you
>send it to some other specialize in it?
>
>Thank you
>
>Yannick
>
>
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