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SMTAI MSD Council Meeting Minutes-- Wednesday 10/10/2007-- 9:30 AM - 11:30 AM
Attendees:
Miguel Arroyo Colomer ---Sypris Electronics
Karl Fink---- Sypris Electronics
Carl Schneider -- Inovaxe
Forrest Briggs--- Inovaxe
David Steele---Da-Tech Corp.
Oscar Salazar--Sypris Electronics
Mumtaz Bora - Kyocera _Wireless Corp.-- Co- Chair MSD Concil
Michelle Ogihara --- Seika Machinery---Co -Chair MSD Council
Minutes:
M. Bora reviewed the current status of Industry standards for MSL classification -- J-STD-020D (revision 06/07) and MSL Handling/Storage/Packaging standard -J-STD 033B.1 ( revision 01/07) .
MSL Classification needs to be redefined if packages are used for Lead free reflow as every 10C rise in peak reflow temp, MSL Class is reduced by 1 class level (e.g MSL 2A( 1 month floor life) to MSL 3 ( 7 days floor life).
J-STD -033B.1 is revised for several items.
New Humidity Indicator cards - 5/10/60% RH
HIC Indication
Short Duration Exposure and Oven Bake Cycles
Resetting and Pausing Floor Life at User Site
Shelf Life
Caution Labels
Items Discussed:
When packages are opened for IQC, they should be immediately resealed after inspection and stored in controlled storage conditions.
Passive components ( ceramic chip resistors and capacitors) , normally classified as MSL 1( unlimited floor life) have shown field failures after lead free reflow due to presence of moisture in the package. A new standard is being defined in industry for lead free passives MSL handling.
Paul Krystek at IBM is defining the draft for this standard.
The major impact of lead free reflow for OEMs is handling and storage of PWBs for lead free reflow as the incidence of delamination has increased during lead free reflow.
The following guidelines should be followed for handling PWBs. MSD council will follow up with a webcast to address PWB handling issues.
OEMs to work with PWB suppliers to get guidelines for storage prior to package opening and after package opening .
PWBs should be treated as MSL classification 4, not to be left open on the floor more than 72 hours . This means to open packages , just prior to loading for screen printing as some of the higher Tg laminates ted to have more affinity for moisture absorption.
3 types of laminates are in use for SMT assembly.
Low Tg -- 140 C and below
Mid Tg -- 150C and below
High Tg 170 C and above
Careful understanding of the Tg ( glass transition temperature and Td- Glass decomposition temp.) is important for selection of laminates for lead free reflow.
Most PWB suppliers guarantee shelf life for 6 months for unopened packages. Proper control and monitoring is essential after opening packages
For delamination issues, please work with supplier for bake procedures. Baking at 120- 140C for 6- 8 hours helps in drying the moisture.
This is very dependent on the laminates used and the surface finish on the PWB ( ENIG, OSP, HASL etc.) . Baking is normally not recommended for OSP surface finish.
The following guidelines help in minimizing delamination issues during lead free reflow.
Bake at 120C- 140C for 4 hours prior to packaging at PWB supplier.
Package in Moisture barrier bags with dessicant and HIC card.
OEM storage in controlled conditions per J-STD -033B.1
OEM practice FIFO( first in/ first out) to minimize aging of PWBs
Packages opened for IQC to be immediately resealed after inspection
Packages on the floor to be opened just prior to assembly.
Assemblies waiting for rework/test debug should be properly dessicated.
PWB suppliers may charge a liitle bit more to do this type of packaging, but this cost is offset by the scrap you minimize in production.
MSD Council has conducted 2 webcasts for MSL guidance this year.
June 2007 --Understanding Moisture Reflow Sensitivity of IC Packages by Jack McCulen-- Intel corp.
Jack gave an excellent coverage of MSL guidelines for IC packages and their classification.
August 2007-- Lead Free and JSTD 033B.1/020D . What about Passives. By Steve Martell-- Sonoscan
We plan to have a third webcast on PWB handling for lead free reflow possibly in November or December 2007. Anyone interested in presenting , please contact Mumtaz Bora at 858-882-1967.
Question related to both MSL standards should be submitted to my attention mbora@kyocera-wireless.com. I will work with the industry experts to get these answered.
Minutes will be posted on the MSD council website at www.smta.org.
Thanks to all the attendees for their participation. We look forward to working with you and making MSL controls less confusing.
SMTA
Moisture Sensitive Devices (MSD)
Council
Dedicated to advancing the
understanding and practice of MSD control
Dear MSD Council
Member,
 We are happy to report that
the MSD Council is up and running! Earlier this
fall two volunteers came forward to chair our
council. They are Mumtaz Bora (Kyocera Wireless)
and Michelle Ogihara, Seika Machinery. I have
known both of these ladies for a number of years
and know they are very high energy and will do a
good job for us. In addition to surveys we will
also plan for a Webcast in 2007. We are also
working to develop an “Ask the Experts” panel that
will be willing to respond to your questions.
Please continue to check our Web site for more
information on this.
We will also be planning
one formal meeting each year. This will be planned
in conjunction with SMTA International next
October in Orlando.
A
part of our initial plan is to determine more
clearly what your needs are and how we can best
address them. We would ask you to please respond
to all or part of the survey below. Please e-mail
your response back to me at joann@smta.org.
Using #1-8 below please
tell us what sector of the industry you work in?
1 - Aerospace
2 - Automotive/Harsh Environment
3 - Biomedical
4 - Defense
5 - RF/Microwave
6 - Telecommunications
7 - Cell Phones/Mobile
8 - Optoelectronics/MEMS
9 - Other My industry sector number
is______________
Please respond to the
questions below as they relate to your industry
sector. What impact do they have and what issues
are of concern to you?
Floor life derating for lead-free reflow.
Impact to yields due to MSL issues.
Baking cycle tape vs tray…cycle time impacts,
issues, cost.
J-Std 033A-items that are unclear need to
change, proposed additions.
J-Std 022-items that are unclear need to
change, proposed additions.
Handling MSL parts-challenges.
MSL label issues.
Dry storage issues, cost impact.
Shelf life of packages.
PWB MSL class, storage, and handling issues.
Other topics, issues, or concerns that you
would like addressed.
Thanks for taking time in
your busy day to offer your input. Our success
will be determined by how well we can hear and
respond to your needs.
Cordially,
JoAnn Stromberg
Administrator
Purpose
The MSD Council is a
voluntary group, under the auspices of the SMTA,
dedicated to advancing the understanding and
practice of moisture sensitive devices control
in electronic assembly procedures and practices.
Specifically, the
council will serve industry professionals who
are SMTA members that have an interest in
moisture sensitive devices. |
Charter
The MSD Council will
be chartered to expand awareness through the
member-secure information available on-line here
and through educational programs, tutorials,
symposia, publications, events for extensive
networking, and possibly certification.
With the increasing need
for globalization in the area of industry
standards, and with the understanding and proper
practice of such standards, the MSD Council will
also establish formal and informal relationships
with international organizations that are
responsible for publishing related information.
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The Council represents engineering,
production management, quality assurance and
reliability, research, sales and marketing,
education, purchasing, and other functions.
Companies and institutions represented
include electronic manufacturers and users,
research laboratories, consultants,
universities, component manufacturers, and
manufacturers of related products.
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If
you are interested in serving on the Council,
contact SMTA administrator JoAnn Stromberg and
include your name, company, and contact
information.
While
the information on the page below is accessible
to all visitors, the information on the Self
Assessment and Resources pages is accessible
only to SMTA members.
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Introduction to MSD
Control
MSDs
are electronic devices encapsulated with plastic
compounds and other organic materials. Moisture
from atmospheric humidity will enter permeable
packaging materials by diffusion and
preferentially collect at the dissimilar
material interfaces.
During solder reflow, the
combination of rapid moisture expansion and
materials mismatch can result in package
cracking and/or delamination of critical
interfaces within the package.
These internal defects
are nearly impossible to detect during the PCB
assembly and test process. They lead to a number
of failure modes that have a negative impact on
manufacturing yields and cause early life
failure of the finished electronic products.
The risk of failure
during reflow is directly related to the
concentration of moisture at the critical
interface, which is near the centre of the
package. The maximum acceptable moisture content
and the rate of moisture diffusion vary for each
package.
To provide
suitable guidelines for assembly, the component
manufacturers must categorize each new device
based on how long it takes to absorb a critical
level of moisture in a standard production
environment. |
The proper storage and handling
procedures during PCB assembly are clearly
defined in the joint IPC/JEDEC standard
J-STD-033A Standard for Handling, Packing,
Shipping, and Use of Moisture/Reflow Sensitive
Surface Mount Devices, released in 1999 and
revised in July 2002.
The standard dictates
that moisture sensitive devices must be properly
classified, identified, and packaged in dry bags
until they are needed for PCB assembly. Once the
bags are opened, each moisture sensitive device
must be assembled and reflowed within a
specified timeframe.
Go to information on the status of
the forthcoming J-STD-033B revision, within
which lead-free appears to be the most critical
issue that is being addressed.
Basic proper handling
requires that the total cumulative exposure time
of each single reel or tray of sensitive
components must be tracked through the complete
manufacturing process, until all the components
are placed prior to reflow.
This basic material and
process control becomes very difficult to follow
in a high mix production environment, when
partial trays and reels are often removed and
re-loaded from assembly lines to be stored in
dry cabinets or dry bags.
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 The following issues are commonly found
to cause significant levels of escape with
existing manual procedures:
Clearly identify the trays and reels
containing moisture-sensitive devices.
Maintain a log sheet of cumulative exposure
time associated with each tray and reel.
Maintain the association between the log sheet
and the individual trays and reels.
Maintain an acceptable level of data
integrity/quality during manual logging and
date/time calculations.
Keep track of the remaining floor life and
expiration of MSDs while they are loaded on
placement machines.
Additional opportunities
are provided in the standard to account for dry
storage under certain conditions (Short Duration
Exposure) and to account for the ambient
manufacturing conditions (Derating due to factory
environmental conditions). Although they provide
additional flexibility for the users, these rules
and tables are even more difficult to implement
with a manual procedure.
The table and image above were
extracted from the joint IPC/JEDEC standard
J-STD-033A Standard for Handling, Packing,
Shipping, and Use of Moisture/Reflow Sensitive
Surface Mount Devices, released in 1999 and
revised in July 2002.
Top Ten Issues and
Misconceptions Associated with MSD Control
| Moisture sensitive devices are a serious
assembly issue that requires a high level of
control. A lack of proper control will result in
internal component damage during reflow due to
moisture expansion. This will typically create
insidious latent component defects that can
escape inspection and test. |
The
industry standards provide a set of guidelines
that are notoriously difficult to understand and
challenging to implement. Simplified manual
procedures tend to err on the conservative side
and result in a large number of unnecessary bake
cycles. This has a significant impact on lead
solderability and material flow.
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The
following "Top Ten" list was provided courtesy of
Cogiscan and is intended to dispel certain
misconceptions related to MSD control in
electronics assembly.
1. In general, quality and
process engineers in the PCB assembly industry
have a number of misconceptions about MSD control,
because they have not been formally trained on the
most recent industry standards.
2. Many
internal procedures are based on obsolete industry
standards, such as the IPC-SM-786A and
JESD22-A112. These documents have been superseded by
the joint IPC/JEDEC standard J-STD-033A released
in 1999 and revised in July 2002.
 3. A sealed dry bag with desiccant does
not require high vacuum. A simple heat seal with
the proper quantity of desiccant is sufficient.
High vacuum can actually be detrimental by
increasing the amount of moisture diffusion
through the bag.
4. The bag seal date and the
12 months minimum shelf life is not an expiration
date. The decision to bake components is strictly
based on the status of the humidity indicator card
when the bag is opened.
5. The clock of
exposure time does not always stop when previously
exposed components are returned to dry storage
(dry cabinet or dry bag).
 6. Components that have never been
exposed and get stored in 10% RH dry cabinets may
have a limited storage life and exceed their
critical level without ever being exposed to
ambient conditions.
7. The default bake cycles
have been significantly increased from 24 hours to
48 hours at 125C, and from 8 days to 79 days at
40C. A table is provided in the IPC/JEDEC
standard J-STD-033A to reduce the bake cycle
according to the physical parameters of each
component (MSL and body thickness). To avoid
degrading solderability there is a cumulative
limit of 48 hours at 125C.
8. The floor life
clock is not reset by reflow. Assemblers must
track the remaining floor life of MSDs assembled
on boards for double-side reflow and rework.
9.
When factory ambient conditions exceed 30C / 60%
RH, the floor life indicated on the MS label is no
longer applicable. In this case the floor life
must be de-rated.
10. Boards must be baked
prior to rework to avoid damaging moisture
sensitive components during localized reflow. The
default bake cycle for populated boards is 10 days
at 90C.
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