OK, I didn't get any response to my "informal poll",
so I'll ask one more specific question before I start getting grouchy
(grin)
If you attend Lead Free Reliability presentations by people like
Werner Englemaier or Gary Ferrari (highly respected in our industry)
they recommend a material like IPC-4101/126 or /129
If you go to websites like Merix (also highly respected)
http://www.merix.com/RoHS+_+Lead+Free.aspx?id=4
they recommend something different
Does anyone have knowledge that would help clarify the discrepancy?
Is the /126 /129 just SUPER reliable over /99 and /124?
Does anyone have a feel for the cost/benefit ratio?
(ok, that was three questions)
and no, I'm not a materials expert, but I MUST call out SOMETHING.
and SOON!
(I'm trying to wade through the materials info in the new Printed
Circuits Handbook, but its still confusing. But hey, maybe I WILL
be a materials expert by next week, huh?)
onward thru the fog,
Jbro
On 10/29/07, Jack Olson <[log in to unmask]> wrote:
>
> I was asking a question about base materials over on TechNet, and stumbled
> over a thought that I can't answer
>
> Quite often (like EVERY presentation) we are being told to specify better
> materials if we have to do Lead Free soldering, right?
>
> Here is a sample note:
>
> MATERIAL: LAMINATE FLAME RETARDANT EPOXY-GLASS PER IPC-4101
>
> /126, 170 DEGREE C MINIMUM Tg, AS TESTED PER IPC-TM-650,
>
> 2.4.24C (TMA METHOD). DECOMPOSITION TEMPERATURE TO BE 340
>
> DEGREES C MINIMUM, AS TESTED PER IPC-TM-650, 2.4.24.6.
>
> A T288 DELAMINATION TIME OF 35 MINUTES MINIMUM, AS TESTED
>
> PER IPC-TM-650, 2.4.24.1C.
>
> A MAXIMUM THICKNESS EXPANSION OF 3% FROM 50 – 260 DEGREES C.
>
> PREPREG MATERIALS PER /126 SHALL MEET THE SAME REQUIREMENTS.
>
> INNER LAYER FOIL PER IPC-4562, TYPE E, GRADE 3, CLASS 2.
>
> So my question is, if IPC-4101/126 is already rated at Tg170 minimum,
> Td340 minimum, etc.
> then
> Why do we have to repeat it in the note?
> Isn't that redundant?
>
> Just as an informal poll, if you are doing lead free assembly, are you
> USING a note like the one above?
>
> Also, this isn't a base material question, but What is your minimum
> acceptable hole wall thickness?
> I've gotten advice that we should increase it, for better z-axis
> reliability. Anyone doing that?
> (I'm not questioning the wisdom of those numbers, just wondering if
> everyone is USING them)
>
> onward thru the fog,
> Jack
>
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