I think that this is a chicken and egg question and needs to be considered
from a PCB fab viewpoint as well. It is expensive for a pcb fab house to
have more than one soldermask, because they have to pay for UL approval,
because they cannot 'leverage' their supply as well (lower volume), because
they either have to have seperate equipment or incur set up costs every
time they change ink, and because they have to change their exposure,
developing and cure cycle settings for different inks. The metal finish
required by the customer - HASL, ENIG, Immersion silver, immersion tin,
entek - also has an effect on the ink that can be used - many inks do not
withstand the chemical attack from these finishes, so I would suggest you
go back to your PCB supplier(s) and ask the question how will this affect
their supply to you (and ask the Operations or Technical Director, not the
sales guy who will say no problem - I speak from experience) and by how it
may affect their supply, I include lead time, UL certification, metal
finish options, SIR and SECC conformity. It may just be green paint to you,
but it has a major impact on the fab process.
Dougal Stewart
email [log in to unmask]
telephone +44 1896 822204
mobile +44 7984 629667
-----Original Message-----
From: Peter Crain [SMTP:[log in to unmask]]
Sent: 22 November 2001 22:14
To: [log in to unmask]
Subject: [TN] best finish for through hole boards
I am not sure why an empty message just got posted. Anyway, here is my
question: We are looking to standardize our board finish for all of our
through-hole boards. We have many types of finishes (mat or flat,gloss,
semi-gloss, dark green, light green)and are looking to change to the mat
finish to cover, um hide, the little bit of flux residue that we find
exceptable. We use a no-clean flux.
Is there any difference in solderability when using different finishes. Do
the profiles change between board finishes? Does the type of finish affect
defect rate? What are other's using and finding best results?
Thanks
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