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April 2007

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TechNet E-Mail Forum <[log in to unmask]>, Hfjord <[log in to unmask]>
Date:
Tue, 24 Apr 2007 21:02:42 +0200
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Graham,
Someone mentioned small batch manufacturing. Once, we tried vacuum to
get 100% bubblefree coating. Took just a couple of minutes in a vacuum
chamber. Need not real vacuum, just let the pump work some minutes,
that's all. Initially, we used it for glues with low viscosity, but
worked perfect for coatings as well. If the coating is thick and tacky,
it won't work. Takes too long time.
Guess you have done that yourself too.
Inge

-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Graham Naisbitt
Skickat: den 24 april 2007 19:30
Till: [log in to unmask]
Ämne: Re: [TN] Fw: [TN] Conformal Coating Voids

Joel

Now we know you are using a UV curable, you should check the curing  
set-up with the coating manufacturer. Seems like too much energy...

Kindest regards,

Graham

[log in to unmask]



On 24 Apr 2007, at 15:12, Joel Alexander wrote:

> The application is very tight with many close keep out areas. That  
> is why
> we are using a precision coating machine with a UV cure. The boards  
> area
> cured seconds after that are coated so the coating does not spread out
> onto keep out areas.  This is new equipment and the manufacturer has
> resolved the bubble problem but we now have to determine what to do  
> with
> the product that is already coated.
>
>
>
> Joel Alexander
> Quality Assurance Manager
> TT APSCO, INC.
>
> ----- Forwarded by Joel Alexander/perry/apscoinc on 04/24/2007  
> 10:05 AM
> -----
>
> "Bloomquist, Ken" <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 04/24/2007 09:24 AM
>
> Please respond to
> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
> "Bloomquist, Ken" <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> Re: [TN] Conformal  Coating Voids
>
>
>
>
>
>
> Joel,
>
> We use a moisture cure urethane and if we get the coating on too thick
> and the humidity is high we get foam like bubbles. I believe the  
> coating
> skins over too fast trapping all the volatiles underneath. We resolved
> this by doing a 40% first coat and then a 60% second coat to get the
> required thickness. We only allow about 20 - 30 minutes between coats.
> And like Ramon said, don't put them in an oven too soon after  
> coating if
> you oven dry your boards.
>
> KennyB
>
> -----Original Message-----
> From: BADRI [mailto:[log in to unmask]]
> Sent: Tuesday, April 24, 2007 6:15 AM
> To: [log in to unmask]
> Subject: Re: [TN] Conformal Coating Voids
>
>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Joel Alexander
>> Sent: den 23 april 2007 21:47
>> To: [log in to unmask]
>> Subject: [TN] Conformal Coating Voids
>>
>> We are using Urethane coating on an assembly that uses  63/37 solder.
>> We are using organic water soluble flux. We are Ionic testing after
>> wash and we are well within IPC cleanliness specifications. We
>> installed a selective coating machine and in our initial run of
>> product we had some small bubbles that look like foam. Our customer
>> does not like it but our stand is that it meets IPC-A-610 and
>> J-STD-001 requirements since there in no obvious voids between
>> conductors. They were worried about corrosion if a bubble was against
>> a lead. The bubbles are fully encapsulated. Does anyone think this is
> a valid concern?
>>
>>
>>
>> Joel Alexander
>> Quality Assurance Manager
>> TT APSCO, INC.
>>
>>
>
> ForwardSourceID:NT000B42FA
>
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