NSC AN-2029

National Semiconductor
Application Note 2029
Martin Schnepf
June 18, 2010
Introduction
inside the package can create excessive internal pressure
resulting in delamination or even cracked package (popcorn
effect).
NSC’s components that are considered moisture sensitive
are sealed in moisture barrier bags (MBB) together with a
desiccant and a Humidity Indicator Card (HIC). National
Semiconductor generally follows Industry Standards IPC/
JEDEC J-STD-020 and J-STD-033 to determine the moisture
sensitivity level and corresponding floor life time for NSC’s
plastic package types, for details on absolute maximum ratings for soldering see www.national.com/ms/MS/MSSOLDERING.pdf.
The floor life time is the maximum time period from the opening of the MBB to the final reflow soldering process. The MSL
Level and floor life time as per Table 1 is provided on NSC’s
immediate and/or intermediate packing container label. Additionally, the MSL level and the maximum peak package
temperature for National’s devices can be found within the
Product Folder of National’s website.
This Application Note provides recommendations for handling, storing and mounting of National Semiconductor’s surface mount IC packages.
The final manufacturing yield and board level reliability are
influenced by various factors and processes outside the control of the IC manufacturer. This Application Note can therefore only be used as a guideline and reference to support our
customers. Due to the variety of possible board assembly
materials and equipments, National Semiconductor Corporation (NSC) advises the user to consult the individual suppliers
and vendors to achieve the optimum board assembly yield.
Moisture Sensitivity Level
Due to the hygroscopic nature of the plastic encapsulants, the
plastic ICs absorb a certain amount of moisture. When subjecting a SMT device to reflow soldering process (e.g. infrared, convection, vapor phase), the entrapped moisture
Handling & Process Recommendations
Handling & Process
Recommendations
TABLE 1. Moisture Sensitivity Levels (According to IPC-JEDEC J-STD-033B.1 (Note 1)
Floor Life (out of MBB)
MSL Level
Time
≤ 30ºC / 85% RH
≤ 30ºC / 60% RH
4 weeks
≤ 30ºC / 60% RH
168 hours
≤ 30ºC / 60% RH
72 hours
≤ 30ºC / 60% RH
48 hours
≤ 30ºC / 60% RH
24 hours
≤ 30ºC / 60% RH
Mandatory bake before use. After bake, must be reflowed ≤ 30ºC / 60% RH
1
Unlimited (no moisture barrier bag)
2
1 year
2A
3
4
5
5a
6
Conditions
within the time limit specified on the label
Reflow Soldering
Solderability tests were conducted on components after long
term storage in warehouse conditions and after exposure to
accelerated aging environment. Based upon the results,
NSC’s shelf life of dry-packaged moisture sensitive devices
inside the unopened moisture barrier bag is 3 years after
original seal date when stored in an environment not exceeding 40ºC / 90% RH. Component storage outside the MBB
should be done in a dry storage cabinet at < 25°C and < 10%
R.H. to prevent any moisture absorption.
The shelf life with regard to soldering of non dry-packed devices, i.e. MSL1, is 3 years provided the storage environment
is controlled at ≤ 30ºC / 85% RH.
Please be aware that e.g. bare die & wafer products have
different storage conditions and limitations.
The most popular soldering method for surface mount devices is forced convection reflow and therefore the topic of
this chapter. Other possible solder processes for surface
mount devices are, with restrictions, infrared reflow (IR), vapor phase and wave soldering.
It is not possible for an IC manufacturer to provide a general
reflow profile recommendation for the end customer in charge
of the board assembly. Reflow furnace settings depend for
example on the number of heating/cooling zones, type of solder paste/flux used, board and component size as well as
component density.
The actual temperature setting needs to be above the liquidus
temperature (solder melting point) of the solder paste in order
to form a reliable solder joint, while the upper limit is clearly
defined by the maximum peak package body temperature
depending on package thickness and volume as provided by
IPC /JEDEC J-STD-020, see Table 2 and Table 3
Note 1: Copyright IPC/JEDEC. Reproduced with permission.
© 2010 National Semiconductor Corporation
301141
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AN-2029
Storage and Shelf Life
AN-2029
TABLE 2. Maximum Peak Package Body Temperature Tp (according to IPC-JEDEC J-STD-020D) For Pb-Free Process
(Note 1)
Package
Thickness
Volume
< 350mm3
Volume
350-2000mm3
Volume
> 2000mm3
<1.6 mm
260 °C
260 °C
260 °C
1.6 -2.5 mm
260 °C
250 °C
245 °C
>2.5 mm
250 °C
245 °C
245 °C
TABLE 3. For SnPb Eutectic Process (Note 1)
Package
Thickness
Volume
< 350mm3
≥ 350mm3
<2.5 mm
235 °C
220 °C
≥2.5 mm
220 °C
220 °C
It is important to understand that the temperature profile provided within IPC/JEDEC J-STD-020 reflects the profile used
for device (MSL) classification see Figure 1 and Table 4 with
the temperature measured on the top package surface during
the reflow soldering process.
The actual board assembly reflow furnace settings need to be
developed separately depending on furnace characteristics
and board design. The selected temperatures should not exceed the parameters used for MSL classification.
Volume
NOTE: Package volume excludes external terminals (e.g.,
balls, bumps, lands, leads) and/or nonintegral heat sinks.
30114101
FIGURE 1. Classification Reflow Profile (peak package body temperature) for Pb-free reflow soldering
TABLE 4. Classification Reflow Profile Parameters (according to IPC-JEDEC J-STD-020D) (Note 1)
Profile Parameter
Pb-free Assembly
SnPb Assembly
Preheat Temperature range
150°C – 200°C
100°C – 150°C
Duration
60-120sec
60-120sec
Ramp-up rate
Max 3°C/sec
Max 3°C/sec
Liquidus Temperature TL and
217°C
183°C
Time above TL
60-150sec
60-150sec
TP Peak Package Body Temperature
See Table 2
See Table 3
Dwell time within 5°C of at TP
Max 30sec
Max 20sec
Ramp-down rate
Max 6°C/sec
Max 6°C/sec
www.national.com
2
If the Floor Life time is exceeded or the Humidity Indicator
Card indicates excessive moisture after opening the MBB (the
30114102
FIGURE 2. Humidity Indicator Card as per IPC/JEDEC J-STD-033B.1 (Note 1)
Conditions for drying components depend on package thickness, MSL Level and baking temperature. Table 5 provides
an excerpt of IPC/JEDEC J-STD-033B.1 on drying mounted
or unmounted SMD packages. Please note that standard
packing material such as tape, reel and tubes cannot with-
stand higher baking temperatures and the components need
to be taken out of the immediate shipping container. Only high
temperature trays are able to withstand baking process at 125
ºC.
TABLE 5. Reference Conditions for Drying Mounted and Unmounted SMD Packages (as per IPC-JEDEC J-STD-033B.1)
(Note 1)
Bake @ 90°C ≤5% RH
Bake @ 125°C
Package Body Level
Exceeding
Floor Life by
>72 h
Exceeding
Floor Life by
Exceeding
Floor Life by
>72 h
≤72 h
Exceeding
Floor Life by
≤72 h
Bake @ 40°C ≤5% RH
Exceeding
Floor Life by
>72 h
Exceeding
Floor Life by
≤72 h
Thickness
2
5 hours
3 hours
17 hours
11 hours
8 days
5 days
≤1.4 mm
2a
7 hours
5 hours
23 hours
13 hours
9 days
7 days
3
9 hours
7 hours
33 hours
23 hours
13 days
9 days
4
11 hours
7 hours
37 hours
23 hours
15 days
9 days
2
18 hours
15 hours
63 hours
2 days
25 days
20 days
2a
21 hours
16 hours
3 days
2 days
29 days
22 days
3
27 hours
17 hours
4 days
2 days
37 days
23 days
4
34 hours
20 hours
5 days
3 days
47 days
28 days
2
48 hours
48 hours
10 days
7 days
79 days
67 days
2a
48 hours
48 hours
10 days
7 days
79 days
67 days
3
48 hours
48 hours
10 days
8 days
79 days
67 days
4
48 hours
48 hours
10 days
10 days
79 days
67 days
Thickness
>1.4 mm
≤2.0 mm
Thickness
>2.0 mm
≤4.5 mm
Note: For BGA package types >17x17mm, stacked die
packages or packages with thickness > 4.5mm, please
contact your local NSC sales representative
3
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AN-2029
color change is described on the HIC card, see Figure 2 ),
baking is required prior to the reflow process in order to remove any moisture out of the plastic package.
Drying of Components
AN-2029
Repair
Permissions
In case repair or even replacement of a component is needed,
it is important that the temperature used for repairing, desoldering or replacing the component, needs to be selected as
low as possible to avoid any damage to the adjacent components or PC board. The repair profile should be similar to the
actual reflow profile, common rework tools are either hot gun
or available rework machines.
In addition, depending on the MSL level of the component and
if the floor life time from initial reflow soldering process to the
repair process is exceeded, a baking process is required with
parameters provided in IPC/JEDEC J-STD-033B.1. Otherwise, the accumulated moisture can cause damage as described in the previous chapters.
Proper handling practices are required to prevent any ESD
damages during any handling of the components.
Note 1: Copyright IPC/JEDEC. Reproduced with permission.
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AN-2029
5
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Handling & Process Recommendations
Notes
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