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January 2008

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Subject:
From:
Bill Kasprzak <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Bill Kasprzak <[log in to unmask]>
Date:
Thu, 3 Jan 2008 08:49:04 -0500
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Graham and Doug ,

Thanks for your help and pointers.

All I'm looking for at the moment was a resource that indicates better 
coverage for Dipping vs Spraying.

Intuitively I realize that this is the case, but I need a source that 
actually states that this is the case.

If we pursue dipping equipment, I will definitely look for pointers.

Thanks again.




Graham Naisbitt <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
01/03/2008 06:11 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Graham Naisbitt <[log in to unmask]>


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Subject
Re: [TN] Looking for Coating Comparison






Hi Bill

Thanks for the intro Doug and Happy New Year everyone.

There was indeed a comparison study done by IVF in Sweden led by Dr 
Per-Erik Tegehall in the late 80's early 90's. I can pretty much 
summarise:

Dip v Spray - If you can locate all components that shouldn't be 
coated onto one edge of the assembly (to eliminate masking) then logic 
says the best and cheapest way to conformally coat is to dip. Because 
you coat both sides at the same time, and the board edges, you can run 
anything up to around 40 units per dip. This would yield something 
more than 600 assemblies per hour from a basic system.

The tricks - apart from the masking issue are:

Immersion depth must be really accurately controllable.
Speed in should be less than 12 inches (30 cm in new money) per MINUTE 
to ensure that the coating penetrates under all of the components.
Withdrawal speed should be slower then the cascade effect of the 
coating, generally less than 4 inches (10 cm in new money) per MINUTE 
to give you the desired thickness. Material viscosity and solids 
content affect this.
Make the dip stroke as smooth as possible to give best coverage 
without runs and drips and minimise the "wedge effect" at the bottom 
edge.

I can give you a coating film down to 120nm at better than ±5% - you 
simply cannot achieve this sort of coverage/accuracy when spraying.

Reason to spray? Masking is easier - it's a shield not a barrier.
Reason to use a robot? Masking is minimised but never eliminated.
Reason to Dip? Better coverage and save money but get your designer to 
heed the production process.

Hope this helps - if you need more I do have a Conformal Coating Facts 
& Data Book I can send you - ask off-line.

Kindest regards
Graham Naisbitt

[log in to unmask]

www.gen3systems.com

Phone: +44 (0)12 5252 1500
Mobile: +44 (0) 79 6858 2121


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On 2 Jan 2008, at 16:06, Bill Kasprzak wrote:

> Happy New Year to one and all.
>
> It sure was difficult this morning to start the old grind again. 
> Well, I'm
> thinking just 8 more years and I hope I can retire, so the end is in
> sight.
>
> I'm looking into whether there has ever been a comparison study done 
> that
> gives the pros and cons for conformal coating application. I'm sure 
> there
> has been because I remember reading about it. Right now I can't seem 
> to
> find any information on it.
>
> Specifically, I'm looking for something that states that Dip coating
> provides better coverage than Spray coating.
>
> Any suggestions? Thanks in advance for any responses.
>
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