Hi, Seet Leng,
If you have to achieve a specified coating thickness, neither dipping nor
brushing methods of application are controllable enough to guarantee that.
Added to which, you have to mask and de-mask before and after application,
all of which takes time. How many boards are you dealing with at one time?
How complex a shape is the forbidden zone?
If your volume of boards (or customer relations) is sufficient to justify
it, I recommend you buy a programmable conformal coat spray machine such as
is produced by Asymtek. These machines give a very even thickness of
coating in x, y, z and rotational axes, and spray so accurately that you do
not need to mask - just programme for a narrow spray pattern (0.125 inches
wide) to spray up to the edge of the forbidden zone. Once you've qualified
the flow rates, nozzle pressures and feed speeds for the nozzles that you
need to achieve the coating thickness you require, you just have to load
the board, call up the appropriate programme and press a button - the
machine does the rest - on both sides with the jig to flip the board. I
believe there is also a "step and repeat" facility, depending on board
size, that allows you to coat several boards at once. Follow the link below
for more info.
http://www.asymtek.com/
Good Luck.
Peter
Ong Seet Leng <[log in to unmask]> 24/01/2003 10:51 AM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to Ong Seet Leng
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cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: [TN] ADVISE NEEDED
Morning Technetters,
Advise needed. We used to use dipped in method using a conformal coating
machine but as the latex used to cover the forbidden area need at least a
few hours to cure, we cannot afford the time. Due to the extremely tight
schedule given to us, we have engineers sending in assembled boards in the
morning and expect us to perform miracles and have them ready before lunch.
We are now using the hand brush method but as mentioned, due to the
extremely tight schedule, is there any way to measure the coating thickness
without say, measure assembled board before coat, after that coat one
side-measure again, before coat the other side & measure again in order to
get the individual side coating thickness?
We may have used the wrong approach and I desperately need some advise from
you guys and gals. More over, should we revert back to dip in method, how
are one going to measure the coating thickness of one side and then
protected it before proceed to the un-coated side? Any suggestions is
greatly appriciated.
Regards
S L Ong
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