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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