Hi Jon - You should take some satisfaction that your search efforts were
accurate - there isn't a shelf life requirement for HASL finishes or any of
the pwb finishes! ANSIJ-STD-003 is the solderability test specification for
printed wiring boards and within the specification there is some guidance
(not requirements) of how robust a pwb finish should be (IPC-6012 would be
the controlling specification for the pwb solderability). The general
industry consensus is that a tin/lead finish (either HASL or Fused ) should
be solderable for 1 year - most pwb fabricators will sign up for this as a
requirement. Many fabricators produce tin/lead finishes that are solderable
for 3-4 years when stored under nominal conditions (75F +\- 10, 30-60%RH).
The problem is that there are a wide variety of storage environments,
handling issues, and soldering process robustness variables that make the
use of a industry wide, specific shelf life value impractical. The
Alternative Final finishes task group and the JSTD-003 task group are
currently working of developing a "system of merit" values for finishes -
the idea being that a specific finish type (e.g. immersion gold, silver,
HASL, OSP's, etc) would have a figure of merit measurable against a
standard smt process or a wave solder process or a set of storage
conditions. The proposal may or may not work but it would be infinitely
more usable for the board fabricator and the assembler if such a system can
be developed. The initial test of a randomly selected set of pwb finishes
is in progress and the data should be available at the IPC Expo committee
meetings. You should also look at the TechNet archives for some information
that has been discussed on HASL thicknesses. Good Luck/Happy Turkey Day.


Dave Hillman
JSTD-003 Chairman
[log in to unmask]




Jon Seubert <[log in to unmask]> on 11/24/98 12:54:08 AM

Please respond to [log in to unmask]

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Subject:  [TN] Shelf life of HASL fabs.




Is there an IPC spec that covers the shelf life of HASL fabs?

We verify solderability after 3 months on all HASL fabs but I have been
unable to find this requirement in an IPC spec.  I would appreciate any
feedback on industry standards and how others are handling HASL fabs.

Thanks
JPS

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