Remember that bakeout can affect solderability.
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Jack Crawford,
IPC Director of Assembly Standards and Technology
2215 Sanders Road,
Northbrook IL 60062-6135
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fax
847-504-2393
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[log in to unmask] 12/11/01 08:10AM
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Good morning Peter,
I'm sure Dave Hillman will provide the
most accurate response (IMHO) but
until he comes around later in the day,
I'll give my $.02.
The first thing is to determine if the components are
solderable upon
receipt (reference J-STD-002) by performing a solderability
test. If the
leads/terminations pass the solderability test and no
additional
conditioning is performed, the components should be used within
120 days
(guidance information developed under MIL-STD-2000 and
predecessors).
Longer storage can occur based on packaging, temperature,
humidity and air
particulates (i.e. dust, sulphur dioxide, chloride,
ammonia). Previous
guidance suggested that storage could be extended if
storage conditions do
not exceed 25°C and 50% RH, and sealed containers/bags
are used. One note
of caution is to ensure the storage containers/bags
do not introduce
contaminates (silicones, sulphur, polysulphides, etc.,) to
the components
that could degrade the solderability.
As you mentioned,
nitrogen storage is a good option, as it will minimize
oxidation formation
dependent on the purity and temp/humidity control, but
this option comes with
a cost.
To summarize:
- impose
a solderability (coating durability) requirement on
suppliers; component
packaging requirements
- verify
solderability upon receipt or obtain certificate
of
compliance
- develop FIFO
material control
- prepare for
storage (repackage if necessary; original supplier
packaging is usually
suitable)
- control
environment
- periodically perform
solderability tests to determine adequacy of
methods employed
above.
Good Luck!
Steve Sauer
Mfg Engineer
Xetron
Corporation
-----Original Message-----
In general, what is the
standard shelf life for the normal PTH and SMD
components like DIP IC's,
SOIC's, PLCC's?
Assuming that they are non-MSD critical, what would be
the proper
storage method to ensure good solderability is being preserved
(such as
nitrogen storage chamber)?
How significant is the impact of
storage conditions (e.g. humidity,
expose to ambient) and shelf life have on
the solderability of
component
leads?
Rgds,
Peter