For lot acceptance IPC and Military specifications require microsections to be
performed and evaluated on coupons or portions of boards that have been
subjected to thermal stress testing per IPC-TM-650, method 2.6.8.  This is
a 10 second float on solder at 550F.  This has been the requirement for
approximately 20 years.  (previously the temp was 500F)  There is also a
mininum
prebake of 6 hours at 135C.

The temperature used in the solderability test per IPC-J-STD-003 - 473+9F
is very low and used with water white rosin flux to be the worst case senario
for soldering.

The extremely high prebake prior to thermal stress makes that test "unfair" to
use as an evaluation of solderability.

The low temperatures and exposure time for the solderability test make that
test much less rigorous than the thermal stress test.

Susan Mansilla
Robisan Lab

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