13
Storage Condition
Packages described in this document must be stored
in sealed moisture barrier, antistatic bags. Shelf life in a
sealed moisture barrier bag is 12 months at <40°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 fac-
tory conditions <30°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 con-
ditions above have not been satised. The baking condi-
tions are 125°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 com-
ponent 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 4-2 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 above requirements may cause mois-
ture/reow damage that could hinder or completely pre-
vent 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 tempera-
ture from Table 4-1 in J-STD 033; then determine the ap-
propriate 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 envi-
ronmental 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 next table. This approach, however, does not
work if the factory humidity or temperature is 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 package materials ref. JESD22-A120). Recom-
mended equivalent total oor life exposures can be esti-
mated for a range of humidities and temperatures based
on the nominal plastic thickness for each device.
Table on following page lists equivalent derated oor lives
for humidities ranging from 20-90% RH for three tempera-
ture, 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 this
table:
1. Activation Energy for diusion = 0.35eV (smallest
known value).
2. For ≤60% RH, use Diusivity = 0.121exp ( -0.35eV/kT)
mm2/s
(this used smallest known Diusivity @ 30°C).
3. For >60% RH, use Diusivity = 1.320exp ( -0.35eV/kT)
mm2/s
(this used largest known Diusivity @ 30°C).