Ultra-thin PCBs with HASL finish

A customer asked us to deliver the thinnest possible PCB with a HASL (Hot Air Solder Leveling) finish. This was to prevent the diode effect of the different metals (copper, tin, nickel, gold).

By now I know that this is complex -- if not impossible -- for PCBs thinner than 0.8 mm. This is because you cannot properly 'dip' the PCB into the tin.

To rule out the possibility that there is a PCB supplier who could do this, I'm curious whether there are engineers who have experience with this?

PS Our customer has meanwhile successfully completed the first tests with an ENIG PCB of 0.4 mm thickness.

ProtoPCBALabLearnings