Ioan,

WHEW! So many questions, so little time.

There are 2 main issues involved with coating over no clean fluxes.

The first is the bonding of the coating to the PCB.
The residues can prevent bonding or reduce the strength of the bonding.

The second is the compatibility of the flux with the coating.

The answer to number 3 is "YES".
There is not enough time or room to cover all the issues!

The main process issue is the cleanliness of the boards and components prior to reflow.
They must be completely clean for this to work.

Automotive warranties are up to 10 years or 100,00 miles.
This is proving to be a difficult challenge the auto electronics people.
There is a serious lack of test capabilities that can determine the reliability of products after 10 years in the
field.
Waiting for field failures won't work because the designs and components will have changed.

It has become a very tight corner!!

David A. Douthit
Manager
LoCan LLC

"Tempea, Ioan" wrote:

> Hi Technos,
>
> badly need your wisdom on this. We have an automotive application, a simple
> assembly (single sided reflow + wave soldering) that needs conformal
> coating. We are on no-clean CP36 paste from Multicore and X33 no-clean flux
> from the same company.
>
> After having browsed last night through the archives, I still have a lot of
> questions:
>
> 1. what reliability concerns should I have with automotive applications
> 2. any special coating material more suited for automotive
> 3. except for the dendritic growth, any other hazard
> 4. the Nortel analysis bulletins for both materials show the residues are
> inert. should I worry about the flux residues or not? Can the assembly
> process make them less inert?
> 5. if the flux residues are inert, what could screw up the ionic tests?
> 6. what cleanliness tests to do and when in the process
> 7. if fails the test, how to clean
> 8. how to spec the thickness of coating, how to check it?
> 9. what to expect from a good coating house
> 10. what is a good test to do for qualification of the sub-contractor. Since
> it's the only one in town, how to make him do better?
> 11. except Concoat and Humiseal, any other major players in the fiels?
>
> Thank you SIRs and any other contributor,
> Ioan
>
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