I am not sure which is most common (I think after HASL), but both ways are
common. Some of the considerations are:

1. If you are using LPI solder masks, you can apply the ident (legend ink)
after exposing and developing the LPI and cure both the LPI and ident at the
same time. This saves a cure process and is less costly.

2. If you apply white ident before HASL, it will discolor (yellow) during the
HASL step and will not look as bright or attractive.

3. If you apply white ident after HASL, it will be both white and bright and
will look better. However, it will require an additional cure step (more
costly).

I suppose, it really depends on your customer. If aesthetics are important to
them, apply the ident after HASL. On the other hand, if it is not an issue
for your customer, apply it before HASL and save a little money.

Hope this helps.

Larry Fisher
Dexter Electronic Materials
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