Ah ha!
So it would seem that the coating is soaking into the board surface
which might suggest a resist starvation?
If you can, try a brush coat from "pure" material and see if the same
condition recurs.
Aerosols generally speaking have ***all solids in them often less than
5% - and its an expensive packaging medium - which is why I always
recommend hand spraying if spraying is your preferred/required
application method (dipping is bestest!) - Hand spray should allow you
to get up around 20%+ solids from dipping which is at full strength
~35-40% (1B31). Consequently aerosols might exhibit "poor coating"
finishes more readily - because there's ***all there to begin with.
Let me know
Regards
Graham Naisbitt
Email: [log in to unmask]
Phone: +44 (0)12 5252 1500
Web: www.gen3systems.com
On 23 Aug 2009, at 20:06, Inge wrote:
> Yes, variations with same cans.
> OK, will try baking.
> Yes, from same fabricator.
> Mystery.
>
> One of our old foxes, experienced process engineer, you've met him,
> made a try,
> At first, the wet coating was crystal clear, but successively
> throughout room drying, the
> coating changed character, and became matte.
>
> Will let you know.
>
> Inge
>
>
>
> ----- Original Message ----- From: "Graham Naisbitt" <[log in to unmask]
> >
> To: <[log in to unmask]>
> Sent: Sunday, August 23, 2009 6:35 PM
> Subject: Re: [TN] Manual spraying
>
>
>> Inge
>>
>> All from the same can?
>>
>> If no, then I suspect some incomplete curing or "residual board
>> contaminants" might be the problem.
>>
>> Try baking the problem boards for around 8 hours at 80C, leave them
>> to revert to room temp and try again. If problem persists, then
>> there you probably need to run FTIR to figure what is there causing
>> the problem.
>>
>> Also, are they from the same board fabricator? If not, check ROSE
>> to see if there is a difference.
>>
>> If yes, then have the batch checked - it is possible that there
>> has been a labelling issue.
>>
>> Let me know
>>
>> Regards
>>
>> Graham Naisbitt
>>
>> Email: [log in to unmask]
>> Phone: +44 (0)12 5252 1500
>> Web: www.gen3systems.com
>>
>> On 21 Aug 2009, at 12:48, Hernefjord Ingemar wrote:
>>
>>> Nick,
>>> we have done tests today, same operator, same boards, same cans,
>>> same everything. Most boards get a clear, deep and nice look, but
>>> suddenly we get a greyish coating, quite matte!
>>>
>>> Q1: what spray angle do you recommend?
>>> Q2: what spray pattern do you recommend? Zig-zag, up-and-down,
>>> side- to-side or what?
>>> Q3: is the room RH of importance?
>>> Q4: is the process sensitive to laminar flow and if so, what
>>> level is critical?
>>>
>>> Inge
>>>
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Nicholas
>>> Redgrave-Plumb
>>> Sent: fredag 21 augusti 2009 12:31
>>> To: [log in to unmask]
>>> Subject: Re: [TN] Manual spraying
>>>
>>> The only way I can see for the propellant causing this kind of
>>> problem is if the nozzle of the spray can is too close to the
>>> substrate whilst spraying. I note several suggestions in the
>>> posted responses of expensive elevated IR curing ovens etc. for
>>> IB31 but these are really not necessary as this material is dry
>>> to the touch/"tack" dry in only minutes, dry in 24 hours and
>>> cured/fully optimised in 7 days. This would undoubtedly be
>>> accelerated by an elevated cure but it shouldn't really be
>>> necessary. So all you should really need is simple drying cabinet
>>> at ambient temperature just to take the solvent vapours away.
>>>
>>> Otherwise, it could be "champagning" or "solvent-popping" which
>>> are terms to describe a condition where the surface of the
>>> coating material partially cures leaving solvent still trapped
>>> inside the wet- film. The solvent has to go somewhere so it finds
>>> it's way out through the surface and in doing so makes multiple
>>> small holes.
>>>
>>> To avoid this problem should be a matter of going back to basics.
>>> Review the coating procedure, make sure the operators are properly
>>> trained (and not getting the spray nozzle too close to the
>>> substrate).
>>> If the volumes justify the use of a purpose-built spray booth for
>>> conformal coating with intrinsic safety features and laminar air-
>>> flow/ extraction then it might be worth going in that direction.
>>>
>>> But there should be a simple solution to this problem because the
>>> usage of HumiSeal 1B31 globally, in both liquid and aerosol cans
>>> is massive.
>>>
>>> Nick Plumb
>>> Gen3 Systems Limited
>>> Farnborough, United Kingdom
>>>
>>> _________________________________
>>>
>>>
>>> On 20 Aug 2009, at 19:17, Inge wrote:
>>>
>>>> Good Evening,
>>>> we use small cans filled with 1B1 conformal coating for
>>>> handspraying
>>>> boards. The guys are not satisfied with the result, because
>>>> sometimes
>>>> the result is matte. Microscope photos show thousands of
>>>> microscopic
>>>> bubbles in the coating. I suspect that it's included driving gas.
>>>> Or
>>>> wrong handling the spray can.Anyone out there with experience?
>>>> How do
>>>> you avoid this problem?
>>>> /Inge
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