You see what I said, twenty wise men will have twenty different answers. I
suppose what we have discussed hitherto is commercial/industrial boards.
Our MIL/SPACE customers pay such a lot for our boards that they mean, quite
frankly, that there shall not be any bubbles at all. Put into practice,
nobody will do 100% Inspection at 200 time magnification, especially not in
a line that assembles hundreds of boards a day.

As said the Cypriot guru : ' use common sense'

Inge

PS.   I forgot to give advice for the situation when common sense does not
exist.  Maybe someone else can help.

On 23 March 2013 08:20, Brian Ellis <[log in to unmask]> wrote:

> IMHO, it depends what you mean by bubbles/voids. If they are a result of
> humidity being absorbed by hygroscopic contaminants through the coating
> (vesication or mealing) then the answer is a resounding 'not acceptable'
> under all conditions.
>
> If they are the result of poor application of a liquid conformal coating
> or solder mask, I would say that they would not be acceptable if any of:
> 1. the substrate is not wetted under any bubble
> 2. a bubble bridges two bare conductors
> 3. a bubble occupies more than 30% of the space between two bare
> conductors with a potential difference of >10 V
> 4. there are more than 2 bubbles per square decimetre on either side, not
> counting the edges of a board where there are no conductors, up to 5 mm
> from the edge
> 5. a void or bubble can be seen by 10 X visual inspection under a component
> 6. a paraxylylene coating displays any void
>
> Some of the numbers in 3., 4. and 5. are arbitrary; common sense should be
> applied, along with the coating.
>
> My 2 eurocents.
>
> Brian
>
>
> On 21.03.2013 17:18, Douglas Pauls wrote:
>
>> OK, Minions, your next question in the quest to improve J-STD-001 and
>> A-610 relates to bubbles in the conformal coating.
>>
>> I think we can all agree that the ideal conformal coating layer contains
>> no bubbles or voids and is "purdy".    BUT:
>>
>> 1.  Are there bubbles in coatings in areas where they will not impact
>> reliability and their presence should be viewed as a "Process Indicator"?
>> If so, where and what limits would you use?
>>
>> 2.  What would you classify as a bubble requiring disposition, i.e.
>> Becomes an actionable defect?  If so, where and why?
>>
>> 3.  Would any of your answers change depending on what KIND of coating it
>> is, i.e. Acrylic vs. silicone vs. Parylene?
>>
>> Well, OK, that is three questions.  I'm on a roll.
>>
>>
>> Doug Pauls
>> Chairman, IPC Cleaning and Coating Committees
>> Galactic Emporer
>>
>>
>>
>> ______________________________**______________________________**
>> __________
>> This email has been scanned by the Symantec Email Security.cloud service.
>> For more information please contact helpdesk at x2960 or [log in to unmask]
>> ______________________________**______________________________**
>> __________
>>
>>
> ______________________________**______________________________**__________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or [log in to unmask]
> **______________________________**__________
>


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________