15
Handling and Storage, continued
Storage Conditions
Packages described in this document must be stored in
sealed moisture barrier, anti-static bags. Shelf life in a
sealed moisture barrier bag is 12 months at <40
o
C and
90% relative humidity (RH) J-STD-033 p.7.
Out-of-Bag Time Duration
After unpacking the device must be soldered to the PCB
within 168 hours as listed in the J-STD-020B p.11 with
factory conditions <30
o
C and 60% RH.
Baking
It is not necessary to re-bake the part if both
conditions (storage conditions and out-of-bag
conditions) have been satised. Baking must be
done if at least one of the conditions above have
not been satised. The baking conditions are 125
o
C for
12 hours J-STD-033 p.8.
CAUTION: Tape and reel materials typically cannot
be baked at the temperature described above.
If out-of-bag exposure time is exceeded, parts must be
baked for a longer time at low temperatures, or the parts
must be de-reeled, de-taped, re-baked and then put
back on tape and reel. (See moisture sensitive warning
label on each shipping bag for information of baking).
Board Rework
Component Removal, Rework and Remount
If a component is to be removed from the board, it is
recommended that localized heating be used and the
maximum body temperatures of any surface mount
component on the board not exceed 200°C. This method
will minimize moisture related component damage. If
any component temperature exceeds 200°C, the board
must be baked dry per “Baking of Populated Boards”
below prior to rework and/or component removal.
Component temperatures shall be measured at the top
center of the package body. Any SMD packages that
have not exceeded their oor life can be exposed to a
maximum body temperature as high as their specied
maximum reow temperature.
Removal for Failure Analysis
Not following the requirements may cause moisture/
reow damage that could hinder or completely prevent
the determination of the original failure mechanism.
Baking of Populated Boards
Some SMD packages and board materials are not able
to withstand long duration bakes at 125°C. Examples of
this are some FR-4 materials, which cannot withstand a
24 hr bake at 125°C. Batteries and electrolytic capacitors
are also temperature sensitive. With component and
board temperature restrictions in mind, choose a bake
temperature from Table 4-1 in J-STD 033; then determine
the appropriate bake duration based on the component
to be removed. For additional considerations see IPC-
7711 and IPC-7721.
Derating due to Factory Environmental Conditions
Factory oor life exposures for SMD packages removed
from the dry bags will be a function of the ambient
environmental conditions. A safe, yet conservative,
handling approach is to expose the SMD packages only up
to the maximum time limits for each moisture sensitivity
level as shown in Table 6. This approach, however, does not
work if the factory humidity or temperature are greater
than the testing conditions of 30°C/60% RH. A solution
for addressing this problem is to derate the exposure
times based on the knowledge of moisture diusion in
the component packaging materials (ref. JESD22-A120).
Recommended equivalent total oor life exposures can
be estimated for a range of humidities and temperatures
based on the nominal plastic thickness for each device.
Table 8 lists equivalent derated oor lives for humidities
ranging from 20-90% RH for three temperatures, 20°C,
25°C, and 30°C. This table is applicable to SMDs molded
with novolac, biphenyl or multifunctional epoxy mold
compounds. The following assumptions were used in
calculating Table 8:
1. Activation Energy for diusion = 0.35eV (smallest
known value).
2. For ≤60% RH, use Diusivity = 0.121exp (- 0.35eV/kT)
mm2/s (this uses smallest known Diusivity @ 30°C).
3. For >60% RH, use Diusivity = 1.320exp (- 0.35eV/kT)
mm2/s (this uses largest known Diusivity @ 30°C).
