For the final solution. most IC component manufacturers and IC subcontract
assemblers did not simply degrade MSL levels by a few MSL grades to
designate 250-260C reflow performance, because the customers would not
permit this for very long. In most cases the BOM and other aspects of the
packages had to be changed to achieve the same MSL as previously achieved
with the SnPb reflow (235-240C).  This generally included new die attach
adhesives, new mold compounds, possible changes to the design of the
selective silver plating on a leadframe, different solder mask for
BGA/fpBGA, and the increased used of plasma processing.  So while it used to
be common to report the MSL performance of a standard BOM component at the
240 and 260C MSL stress levels, most of us now report the MSL of a standard
BOM at the 235-240 range and the MSL level of the same device with the
"PbFree" BOM.


Best regards,
Leo

Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas     78704

ph     512-383-4593
fx      512-383-1590
[log in to unmask]
www.asat.com


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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Stadem, Richard
Sent: Tuesday, June 21, 2005 7:09 AM
To: [log in to unmask]
Subject: Re: [TN] Moisture sensitivity levels...


So, it begs the question: Has something been added to J-STD-020 that
decrees the MSL level must be incremented by a factor of 2 if the part
is going to be used in a Pb-free reflow process? What study or
documentation tells the part vendors to do this?

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Tuesday, June 21, 2005 6:50 AM
To: [log in to unmask]
Subject: Re: [TN] Moisture sensitivity levels...

Hi Steve!
Had a great Father's day - how my 6.5 month old dragged that bottle of
scotch in I do not understand, but I'll take it.  Whoo-hoo!

As for MSL levels, we are seeing some of the same thing I think you are.
We buy lots of parts through distributors, who repackage them in the
small quantities we need.  The packaging they use sometimes indicates a
MSL level a couple of values higher than it should.  Just a few days ago
our SMT operator had me check one where he had two packages, one
indicating MSL=2, one indicating MSL=3, and when I checked the Ti web
site it showed a MSL=1.  I'm guessing the distributor is being
overcautious and/or marking it up for lead-free processing.  I agree,
it's a pain - as we have to either err on the side of caution and end up
baking parts that don't need to be baked, or we verify each one against
the manufacturer's data.

regards,

Graham Collins
Process Engineer,
L-3 Communications Electronic Systems Inc.
Halifax
(902) 873-2000 ext 6215

>>> [log in to unmask] 06/20/05 12:25PM >>>
Good mornin' all!

I hope all you Dads out there had a wonderful Fathers Day!

As I posted about a week or so ago, we're getting our stockroom
personnel to really focus on component moisture sensitivity levels.

But now I'm starting to get a little confused about how components are
generally classified with their respective MSL ratings.

I've always thought that it had to do with component body size and
thickness, but now I'm finding out that it doesn't necessarily.

My stockroom clerk showed me an IDT SOJ28 that came in sealed with a MSL
3 rating that we now have in our dry box because the package was opened.

We have some Cypress SOJ28's and SOJ24's that are on reels that are not
in original packaging, so I called Cypress and asked what the MSL rating
is for the two part numbers and they are a MSL 1. Cypress gave me a link
to the SRAM Qualification Report that states that.

Now my stockroom clerk brought me some Vishay tantalum caps that have a
MSL 2a rating label on them, and they are TNTC's. This is THE FIRST time
I have ever seen a MSL label on a tantalum capacitor.

Are these ratings based on qualification reports? Or can one look at the
size and thickness of the part to base how you will handle it?

Kind regards,

-Steve Gregory-
Senior Process Engineer
LaBarge Incorporated
Tulsa, Oklahoma
(918) 459-2285
(918) 459-2350 FAX
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