You might check with Lea Ronal to see what the substrate material was for
the 94 V-0 rating on their solder mask; also the recommended thickness.
I've seen the same material pass or fail, depending only on the thickness of
the cured film..  If they use a nonflammable substrate, i.e. an aluminum
panel or similar, you might have marginal results on composite substrates.
Also, the amount of thinner you are using could be diluting the flame
retardant in the solder mask too much.  Again, check with Lea Roanl.

s. Smith, Tracor Aerospace




At 08:32 PM 1/12/98 +1100, you wrote:
>We sent 2 types of samples to UL Lab for 94V-0 Approval. One type
>of samples passed but the other type failed.
>
>The samples which passed the 94V-0 test were 10 pcs of 10-layer FR4
>multilayer boards without solder mask or copper circuit. The
>total Flaming for applications (Set of 5 specimens) are 15 sec
>(23 +/- 2 deg C and 50 +/- 5% RH for 48 hrs) and 12 sec (168 hrs
>air oven at 70 +/- 1 deg C then cooled in a dessicator for at
>least 4 hrs)
>
>The samples which failed the 94V-0 test were 10 pcs of 10-layer
>FR4 multilayer boards coated with solder mask. The total Flaming
>for applications (Set of 5 specimens) are 32 sec (23 +/- 2 deg C
>and 50 +/- 5% RH for 48 hrs) and 48 sec (168 hrs air oven at 70
>+/- 1 deg C then cooled in a dessicator for at least 4 hrs)
>
>The materials we used are :
> Laminate: Isola E-Cu#104ML
> Prepreg:  Isola E#104ML
> Solder Mask: Lea Ronal OPSR 5600 GDA
>
>All the materials are UL 94V-0 approved. I think there could be
>something wrong on our processing, e.g. solder mask over post bake,
>too much thinner, improper thinner, etc.  We use the thinner:
>Butyl Icinol at 3-5%.
>
>What process settings may affect the 94V-0 test result?
>Is there anybody can help ?
>
>Thank you
>
>
>Chan Chi Man
>
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