Hi there Michael, I discovered peelable masks about a year ago & have been
using them since.

After watching someone spend 5 minutes (at 40p a minute) put on hand coating
I investigated peelable masks & found that it only cost 20p-30p (about $0.50
i think) per board & meant that the solderers time could be spent soldering
rather than putting on confomal coating, also that there was less delay in
manufacture.

Over here in the U.K. it comes in blue or green & is usually about 1-2mm
thick, does the job during flow soldering & peels off easily.

I used it today infact, to turn 30 putting on,30 pulling off operations into
10 pulling off operations - saving about 50p a board.

However it is only viable when there is more to cover than the cost of the
time to cover it by hand.

Its not very good for large diameter holes, I have a limit of 3.5mm set by
my board suppliers, unless the peelable is shaped around the edges of the
hole it falls through leaving the plating exposed. but saying this it
sometimes works as there is not a complete land to allow the solder to
bridge.

We also use hand coating for boards that are going to be dipped into
varnish, so as to leave
parts still solderable afterwards. It works for this too, only it can take
longer if on double sided
boards & totally screws things up on SMT reflow boards (needs to be level
for solder paste (or cutouts in the base of the application jig)) and can
only be applied on the bottom then.

It also is very handy for boards that have differing builds, allowing
certain pads to be left free of components depending upon the build.

Anyhow, I hope that get some success with your supplier, & more with
peelable masking.

Matthew Lamkin
Printed Circuit Board Draughtsman
Protec Fire Detection PLC
Nelson, Lancashire, England U.K.
Tel 01282 717393
Email - work [log in to unmask]
Email -home [log in to unmask]



-----Original Message-----
From: Michael Blackburn <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: 28 July 1998 09:41
Subject: [DC] Peelable solder mask


>We have a number of boards that we hand apply a peelable solder mask in
>areas where components are added after wave soldering. Recently, I saw a
>board that had a screened peelable solder mask that had been applied by
>the board vendor. Does anyone have any experience with using this type
>of mask? I've checked with one of our vendors and although he doesn't
>use peelable mask, he has seen such a product and is willing to run some
>samples. Any feedback would be greatly appreciated!
>

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