That's what I love about this forum - people who feel comfortable enough to hold up their hand and say "We're having a problem here" - but prepared to share that in the confidence that there are others who will pass on their knowledge and experience to help.
Thanks TechNet.
Have a great Friday and weekend.
Best Regards,
Phil.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: 03 October 2006 17:50
To: [log in to unmask]
Subject: [TN] FW: [TN] #3 laminate Qualification
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-----Original Message-----
From: Stadem, Richard D.
Sent: Tuesday, October 03, 2006 11:49 AM
To: [log in to unmask]
Subject: RE: [TN] #3 laminate Qualification
Both of you could not have said it better, Ahne and Valerie.
We are still learning painful lessons about Pb-free processes, and their effects on reliability of components, solderability, surface finishes, pcb materials, laminates, and laminating processes. We are learning more about issues of resin recession, hole wall pullaway, ENIG characteristics at higher temperatures, x/y sheer stresses, pad peel strength on alternate materials, via erosion from hi-tin bearing solder, and a ton of other reliability issues.
It should have been done properly, and several qualification processes performed before the Complete Idiots in the EU banned lead in solder, as well as all of the other toxic materials that are not toxic to anyone except perhaps a lunatic in an asylum that has a fetish for eating electronic circuit boards.
If anything, this whole exercise of moving to lead-free, non-toxic materials and processes has shown us just how much we do not know. And, unfortunately, I don't think we will stop learning how little we know for years to come.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ahne Oosterhof
Sent: Tuesday, October 03, 2006 9:53 AM
To: [log in to unmask]
Subject: Re: [TN] #3 laminate Qualification
"We know what we know", followed by: "we know what we think we know", then there is: "we know what we don't know" and finaly: "we don't know what we don't know".
Yuk,
Ahne.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of valerie St. Cyr
Sent: Tuesday, 03 October, 2006 7:46
To: [log in to unmask]
Subject: Re: [TN] #3 laminate Qualification
All,
There are materials whose properties' data sheets have the values that would indicate high thermal stability, and so one might conclude they could pass a lead free reflow or reflows. But it is not so simple. As the laminators load up on fillers to restrain the Z-axis CTE to mitigate against the higher temperature at reflow, the interlaminar strength can be compromised. We are seeing an x-y sheer phenomena. The delamination is not prepreg to copper, or adhesive failure, it can be within a core, or prepreg to glass - a cohesive failure.
Also, regardless of the above, your particular design might survive a lead free reflow process while another design on the same material fabricated by the same supplier will not. Some of these materials have design dependencies only now being understood.
OK, if that isn't problematic enough, these materials aren't drop-in replacements in the fabricator's processes despite any claims to the contrary from the laminators. So, for the same design on the same material if you switch fabricators you could then experience delamination or massive hole wall pullaway (which we haven't seen in a very long time).
What else ? Oh yeah, for non-phenolic systems better prebake before assembly ...
What else ? Oh yeah, some (not all, but some) are still being tweaked and what worked last month may not work next month.
We are not done learning yet... all the answers aren't in. In fact, some of the experiments have even been thought of yet.
my 42 cents.
Valerie
Werner Engelmaier <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
10/02/2006 06:29 PM
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Re: [TN] #3 laminate Qualification
Hi Dave,
Well, I spoke too soon. I did come across numbers similar to these: Tg=210 C,
Td=365 C, just not in this combination.
There are:
N4000-13 200°C 365°C 3.5% STII=247
TU-832 210°C 340°C 2.5% STII=250
IS620 ~205°C 353°C 2.8% STII=251
Werner
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