In a message dated 02/18/2000 1:42:31 PM US Eastern Standard Time,
[log in to unmask] writes:

>
>  Doug makes an excellent point but I would appreciate his / your views on
>  using HASL v Bare copper for our coating tests. Yes, I am sorry we will be
>  running some tests on a new coating material.

Now we get into the "it depends" category.  It depends on whether you are
doing a materials and process investigation or if you are doing a materials
qualification.  If the latter, then bare copper it is.  If the former, then
you have to ask what you want to get out of the test.  If you are trying to
investigate materials interactions, then your test substrate should match the
hardware to be produced, at least as much as possible.  A materials
compatibility study would also fall under this category.

>
>  First, I do appreciate that the spec (IPC-CC-830) calls up B25A bare copper
>  so any results may be questioned. However, if you tested with HASLed
coupons
>  would you expect the results to be better or worse? Our experience has
shown
>  that HASL v NiAu has little appreciable difference.

My experience is different.  I see at least a half decade drop, more
typically a one decade drop comparing HASL to either copper/OSP, bare copper,
or Nickel-gold.  This is why the old Bellcore specifications had a one decade
drop in SIR requirements for HASLed product, compared to bare copper.  If the
HASL process has a very good post-reflow cleaning process, then I see about a
half decade drop.  A typical cleaning process about one decade,and a lousy
cleaning process 2-3 decades drop.

>
>  I would surmise that the results we obtain would be / could be considered
>  "Worst Case".

Depends on your definition.  Of copper, copper/OSP, nickel-gold, palladium,
and HASL, I would consider HASL the worst case due to the exposure to reflow
temperatures.

>
>  As to the Gerber files - I have them here already along with the
fabrication
>  spec. - which calls up bare copper! But our order stated HASL aaarrghhh! -
>  Guess this must go into our ISO 9001 (yeah I know!) "Screw-ups" portfolio -
>  which is VERY THIN I might point out!!!!

Congrats.

Doug

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