Some ECAD systems can give you the data necessary to take component
heights into account. However, it may be that if you use this kind of
equipment, you will need to concurrently engineer with the designer to
ensure that the design permits the head to go where you want it. This
kind of thing is often ignored, but is important, IMHO.
Brian
Carroll, George wrote:
> Iain,
>
> I have to agree with Daan. We have two Nordsons and the Windows based
> software makes programming fairly simple. Whether it can be generated from
> CAD data directly would be another question since component height
> determines the Z-axis movement of the dispensing head and flow and clearance
> allowances almost require the experience and intelligence of a human
> programmer. It sometimes becomes necessary to either mask or use a manual
> application method in cases where a via or other hole is located near a
> connector or other unsealed component on the other side of the board.
> Viscosity contol also becomes important as it relates to the flow. Manual
> examination and touch up is almost always required because most customers
> don't seem to understand the difference between conformal coating and
> potting, and as Dann alluded, coating in places that are shadowed can't
> always be done mechanically. We've generally had good luck with the
> Nordsons but I know Precision Valve and Automation in Halfmoon New York also
> makes good equipment which has positive feed back,lead-screw driven gantry
> robots.
>
> George
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of d. terstegge
> Sent: Monday, February 16, 2004 5:58 AM
> To: [log in to unmask]
> Subject: Re: [TN] Spray coating!
>
>
> Hi Iain,
>
> Wether it's true that you don't have to mask anymore depends very much
> on the design of the product and the quality standards that must be met.
> We have a Nordson/Asymtek slective spray coating machine and still need
> to do manual masking (although it's much less than with dip coating) and
> manual "painting" afterwards to reach the areas that we could not do
> with the machine (while at the same time keeping other areas free of
> coating).
> The problem is not so much the machine's accuracy, but the flowing
> behaviour of the liquid sprayed onto the board. This is quite complex as
> it depends on the topography of the bare board and on how the fluid
> flows from the topsides off the components onto the board surface.
> Only if your boards are designed with this process in mind, and you
> don't require 100% coverage of the top and sides of all the parts, and
> you don't care about a few tracks that are not covered with coating,
> you'll have the maximum savings.
>
> Daan Terstegge
> Thales Communications
> Unclassified mail
> Personal Website: http://www.smtinfo.net
>
>
>>>>[log in to unmask] 02/16/04 10:54am >>>
>
> 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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