packing is the process of putting
surface-mount devices in moisture-resistant bags or moisture
barrier bags (see Fig. 1) to prevent them from absorbing moisture from the
atmosphere. Moisture ingress into plastic packages can result in
popcorn cracking during board mounting. Popcorn cracking refers to
package cracking caused by abrupt vaporization of internal package
Examples of moisture barrier bags
packages have different levels of moisture sensitivity.
The amount of time that the units can spend outside the moisture barrier
bag once it is opened is known as the floor life. Thus, units must
be board mounted before the specified floor life is reached. Units
can not stay indefinitely inside the moisture barrier bag too.
is the amount of time that the units can be kept inside the bag from the
date the bag was sealed. The shelf and floor lives of a lot must be
labeled on the dry pack of the lot.
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to dry packing, units must be
to drive any
internal moisture away. JEDEC J-STD-033 gives the
recommended bake conditions and durations prior to dry packing.
The baked units, which should be in tubes, trays, or a reel, are then put inside the moisture barrier bag
along with, if possible, a
(see Fig. 2) for moisture
absorption and a
(see Fig. 3)
which can indicate the highest moisture level that the units have been
exposed to inside the bag. Dry packing is completed by
Examples of desiccant bags
3. Examples of humidity indicator cards
J-STD-033 Bake Tables; IC
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