We need a little more information to answer that question. Rather than
make you go back and get this information, I am simply posting the
worst-case scenarios for your consideration and analysis with respect to
your product.
1. First, if the assembly has BGAs with leaded solder balls, and the
supplier used lead-free paste, you may have issues with the reliability
of the BGA solder balls. Not likely, but maybe.
2. If the PWB was of a material type that is not able to withstand the
higher temperatures of the lead-free processing, there may be issues
with the z-axis expansion of the vias, which is greater at lead-free
temperatures during processing. Maybe. Delamination is always a
possibility also, but you can usually see that. Resin recession can also
occur, especially around the plated-through holes. You can't inspect for
this, a microsection is required. It is not likely to cause a
reliability issue, but it could, maybe.
3. You could possibly have components on your assemblies that were not
intended to be processed with lead-free temperatures. Their reliability
could have been compromised as a result. Maybe. It might be a good idea
to review the MSD levels at least. If you have components with a
Moisture Sensitivity Level of 3 or higher, I would be much more
concerned, depending also on how well you control the packaging and
handling of these types of components within your factory.
4. Finally, you must realize that your company is on the dirty end of
the liability stick, should things go wrong later.
If you accept the product from your supplier, you must understand that
you are essentially taking them off of the liability hook by accepting
the assemblies with the knowledge of how they were processed. If these
are flight controls, traffic controls, medical devices, whatever, you
describe it only as a harsh-use environment with a greater risk of
reliability issues. There are many papers on the subject of lead-free
for harsh environment. They devote a lot of focus to the use of certain
process steps and process control methods to ensure reliability of
lead-free-processed hardware, yet they do not even include some of the
basic items I have mentioned above. So, as Werner likes to say, caveat
emptor.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of debbie
Sent: Wednesday, February 27, 2008 4:51 PM
To: [log in to unmask]
Subject: [TN] Lead free questions
I have a supplier who used a lead free process for my leaded product.
Besides the possible component issues and PCB delaminatioin what
concerns would/should I have for the solder joint reliability? We are
not under the RoHS directive because the product's end environment is
considered harsh.
The solder joints look fine and it seems to be acceptable but being in a
harsh environment I am inclined to wonder about acceptance. We are
excluded for reasons....
Dang it anyway, please, help.
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