Lain,
I developed our Conformal Coat process[ type AR(Mil-C-46058c/ IPC-CC-830) ]
first with a dip system , then an in-line spray system and now an"I don't
know" out-sourced system.
Cleaning,cleaning,cleaning and cleanliness verification and oh! did I
mention cleaning are critical to whatever system you choose.
Know you end-use enviroment.If the CC only needs to be a glorified dust
bag,then don't worry,be happy.If thermal cycling and standing condensation
is present then you need to establish a continuous homogeneous film.A spray
system with a minimum of 6 to 8 spray heads can replicate a dip
system.Proper tape selection and standard assembly aids can minimize masking
and touch-up.
Single overhead gun systems with a joy stick or CAM system save a lot of
manual labor,but if you have a skylined topography you will not get coverage
or seals at tall part/pwb interfaces.The following is a standard note I had
to come up with so the systems that were not a multi-head, multi-directional
type could meet our requirements:
* Conformal Coating may or may not be present in non-critical laminate
areas of the printed wiring board or on the top and side of the
non-critical, non-conductive surfaces of large scale packages,unless
otherwise specified.This exception is for the coating coverage requirement
and shall not be used to accept uncoated areas due to bubbles, voids and
other workmanship issues.
We are an Aerospace facility,so before I hear it from the No-Clean
gallery,if we use a No-Clean,it will be a cleanable No-Clean( low residue).
We are required to conformal coat all of our assemblies and residues
left(see paragraph two) from No-Clean processes are a detriment to meeting
our long term reliabilty requirements.
Dewey
> -----Original Message-----
> From: Braddock, Iain [SMTP:[log in to unmask]]
> Sent: Monday, February 16, 2004 2:55 AM
> To: [log in to unmask]
> Subject: [TN] Spray coating!
>
> Gents,
>
> I'm looking to replace an existing dip conformal coating m/c. We're a
> low/medium volume military establishment that spends an awful lot of time
> masking up various boards.
> I once saw a spray coating m/c in operation (several years ago!) and it
> looked pretty slick, the engineer stated that manual masking was redundant
> as the operation was carried out modifying the CAM data. If I remember
> correctly the equipment was supposed to be accurate to ~1mm during the
> spraying operation, is this correct / typical?
> I'm looking for the pro's & con's of these systems, approximate cost of
> one
> of these was bearing in mind through put is not an issue & suppliers,
> ideally in the UK but not tied to this.
>
> CIA,
> Iain.
>
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