Hi Ken,

These are very good questions. Based on my research many component vendors
are planning to introduce new part numbers for Pb-free parts. Others are
planning to handle this change with a simple date code transition. Many
top-tier OEMs and EMS companies in North America and Europe are requesting
new part numbers from their vendors but there is no concensus or industry
standard on this subject right now. Changing part numbers is safer from a
process and reliability standpoint but it creates a major inventory issue
during the transition. It is not necessarily a perfect solution either since
many components  are perfectly compatible with both processes. Some vendor
labels even include the information about the two different  Moisture
Sensitivity Levels (MSL) for both Sn/Pb and Pb-Free reflow temperature.
Either way, component and process engineers will probably have to
re-classify a large number of parts by taking into account the alloy and
reflow compatibility issues.

As far as the assembly BOM is concerned it is up to each individual OEM and
EMS to decide how they want to handle this. My guess is that it will depend
on the capabilities of the current MRP/CIM systems that are in place. As you
can imagine the challenges associated with Pb-Free will require the
introduction of new systems to better manage the materials on the production
floor and specifically address the following issues :
1. Being able to identify and segregate Sn/Pb and Pb-Free materials (PCB,
components and chemicals)
2. Validate that the right materials are used at every operation on every
board
3. Provide "as-built" material and process traceability to demonstrate
compliance with the legislation and customer requirements.

If you are interested to understand these issue in more details I invite you
to participate in one of our Web-based seminars on Material Control for
Lead-Free. Please contact me offline if you would like to sign up.

I am not really familiar with any specific issues associated with HASL
boards so I will let someone else respond to this one.

Regards,

Francois Monette
Cogiscan Inc.
Tel : 450-534-2644
[log in to unmask]
www.cogiscan.com


-----Original Message-----
From: Ken Patel [mailto:[log in to unmask]]
Sent: June 8, 2004 4:23 PM
To: TechNet E-Mail Forum.; Francois Monette
Subject: RE: [TN] Mixed assembly of ROHS & Non ROHS components



Hi Francois,
So, do you recommend the following?
   1) new part numbers for lead free components
   2) No problem with HASL processed boards?
   3) separate assy BOM for lead free components

Re,
Ken Patel


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Francois Monette
Sent: Tuesday, June 08, 2004 10:32 AM
To: [log in to unmask]
Subject: Re: [TN] Mixed assembly of ROHS & Non ROHS components

Hi Daan,

I am currently in the process of writing a paper on Material Control for
Lead-Free and here is some relevant information that I found on the subject
of alloy compatibility :

Backward Compatibility (i.e. using Pb-Free components in Sn/Pb process):
BGAs with Pb-Free solder balls are not recommended for Sn/Pb assembly using
temperatures below 220C because the solder joints are poorly formed if the
balls do not melt. As a result 2nd level reliability may be adversely
affected. There is also a potential for increased Sn-whisker growth if the
finish does not melt.

Forward Compatibility (i.e. using Sn/Pb components in Pb-free process): Less
of an issue, some reports of increased voiding in PBGA solder ball joints
due to flux trapping. Another issue that was already pointed out is the
resulting Lead-Contamination that may affect the solder joint structure and
decrease its reliability.

As a result of the above issues, some component vendors, including Intel do
not recommend using their components in forward or backward compatible
assemblies.

References :

- Pb-free IC Component Issues & IPC/JEDEC Specification Update - Rick Shook,
Agere Systems
http://www.turi.org/messages/Rick_Shook-Dec3-03.pdf

- Lead Contamination in Lead-Free Electronics Assembly - Karl Seelig and
David Suraski, AIM
http://www.aimsolder.com/techarticles/Lead%20Contamination%20in%20Lead-Free%
20Electronics%20Assembly.pdf

- Lead-Free Program Overview - Intel Web Site
http://www.intel.com/design/flcomp/packdata/wccp/download/chpt8.pdf

I hope this information is helpful. Feel free to use it for your web site if
you wish.

Francois Monette
Cogiscan Inc.
[log in to unmask]
www.cogiscan.com

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------