Hi Graham and TechNet

There are five key variables in dipping. Immersion speed, dwell time,
withdrawal speed, viscosity and angle of circuit board being immersed.

The immersion can be critical for entrapping air. If in doubt slower is
better when immersing the board.

Dwell time is to do with penetration under components of coating. Most
boards dont need a dwell time but again consider it especially if you have
a high viscosity material or must get full coverage under components.

The viscosity and withdrawal speed are tied together. The faster you pull
the coating out of the material the more / thicker the coating. Think spoon
in treacle. Pull it out fast and you get a lot. Slow it down and you dont
get a big dollop of coating. Viscosity is also linked to how much coating
is left on the board. The more viscous the coating is the more time you
need to drain the coating off. Ideally you want to avoid a cascade effect
where the coating falls off in big lumps after withdrawal. Typical speeds
are 6-12 inches per minute but is viscosity dependent. Refer to the coating
manufacturer on their recommendations.

Finally angle of immersion can be critical. You can dip horizontally,
vertically or a combination. It's just important to consider draining,
pooling, entrapment and the other factors such as viscosity and speed of
withdrawal.

If you need any further advice specifically on the material you're
proposing to use just contact me off line and we can talk.

Best Regards


Dr Lee Hitchens



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On Fri, 30 Aug 2019, 14:13 Graham Collins, <[log in to unmask]> wrote:

> Hello Technet
>
> So I've got a customer who wants to dip coat their circuit board.  It is
> a small thing, 1/2" x 2", with wires attached at one end.  So for dip
> coating I can actually hang it by the wires for curing, no masking
> required - works out OK.
>
> A couple of questions though.
>
> 1) any gotcha's with dip coating?  I've only done spray (manual and
> automated) thus far.  Is viscosity critical?
>
> 2) does anyone make a black colored coating? They are somewhat concerned
> with IP protection so a color block would be a plus.
>
> Happy labor day weekend to all on this side of the pond!
>
> thanks,
>
> --
> Graham Collins
> Senior Process Engineer
> Sunsel Systems
> (902) 444-7867
>