Hi all

Thanks for your responses. As I guessed it is anecdotal and varies 
across industry.

We have the same policy in our services as you Lloyd. Only bake if (a) 
the customer requests it and (b) there is possibly some harsh acceptance 
tests. Otherwise we don't bake and it doesn't seem to make any 
difference to our processing. Who knows for long term reliability?

Best Regards

Dr Lee Hitchens

On 01/03/2017 02:59, lduso - Diamond-MT.com wrote:

> We do not pre-bake as an internal rule and never a complaint. Obvious
> exceptions: We are washing or cleanliness testing the boards. Then we will
> bake them dry before masking and coating. Or the customer specifically
> requires a pre-bake on the drawing. (I always then ask the question; "How
> long after the bake do I have to coat them before they need to be baked
> again?" Strangely, only a few have an answer for that.)
>
> I have visited many facilities that conformal coat and I have witnessed it
> both ways but mostly on the "no pre-bake" side. One customer even pre-baked
> their boards before coating with a water based acrylic.
>
> Lloyd Duso
> Plant Manager
> Diamond-MT
> (814) 535-3505
> www.Diamond-mt.com
>
> On Tue, Feb 28, 2017 at 2:39 PM, Douglas Pauls <
> [log in to unmask]> wrote:
>
>> Lee,
>> It Depends.
>>
>> We have one facility that has never baked prior to coating application.  No
>> evidence of any conformal coating related problems.  We have several
>> facilities that bake religiously prior to coating application, also for
>> acrylic.  No evidence of any conformal coating related problems.
>>
>> I think the biggest factor is how much residual water you have.  I don't
>> think your assemblies have to be bone dry before coating.  We do a lot with
>> in-line aqueous cleaners, which have heated air knifes that remove the bulk
>> of the water.  Now, there might still be some entrapment areas, but if so,
>> we find them and then blow out those entrapment areas with ionized air.
>>
>>
>> Doug Pauls
>> Principal Materials and Process Engineer
>> Rockwell Collins
>>
>> On Tue, Feb 28, 2017 at 10:20 AM, Lee Hitchens <
>> [log in to unmask]
>>> wrote:
>>> Hi all
>>>
>>> I've recently been asked about baking pcbs before conformal coating and
>>> whether there is any quantified data on the effect on coating
>> performance.
>>> Does anyone know of any public studies on this or can shed some light on
>>> its effectiveness beyond anecdotal experience ? I would be very grateful
>> to
>>> you on this.
>>>
>>> Best Regards
>>>
>>> Dr Lee Hitchens
>>>
>>> SCH Technologies is a Division of SCH Services Limited
>>>
>>> www.conformalcoating.co.uk
>>> Skype: leehitchens
>>>
> .
>