Good Afternoon Valerie:
Your response and expertise relative to this subject is most appreciated.
As one whose interest lies in those designs incorporating high end flex
rigid and rigid, I will stipulate to the "suggestion" by UL to consider the
pcb "industry" suggestion to go to a 288C test as a starting point relative
to a new coupon strategy to show compliance with LF and RoHAS standards.
I agree with the multiplicity of laminate/component/assembly issues that you
pose below as being broader in their implications as to determining the
temperature capability of bare laminate.
As suggested earlier, the method for success in the new N-L world would be
to meet these high heat exposure challenges through a co-operative
engineering mode..namely, if you know there are high heat parts in the
assembly, the correct material can thusly be anticipated and identified for
use.
The notion that we should continue the bunker mentality of defending our
particular discipline (read: fabricators) while accepting no responsibility
or understanding of the subsequent impact of follow on processing (read:
component choice and assembly process) is a recipe for failure going
forward.
We must breakdown these provincial barriers between disciplines and allow
those in research, design, manufacturing and processes, both vendor and end
user, to work as a team, as one entity. Thusly we will foresee problems of
production and in use that may be encountered with the product.
It is my view that the time is now to put into place such protocols that
will allow such interaction.
The one requirement is that customers, upon choosing vendors of like mind,
must work in a mode of "open kimono communication" to achieve success. The
time for self-righteous protection of so-called manufacturing secrets that
hindered open manufacturing discussions has hurt our industry.
I truly believe that one method of common ground would be a coupon approval
structure that would ensure that materials chosen would perform at the level
the particular assembly would require. The result, in my opinion, is one in
which we all would enjoy higher profitability and long term success along
with job stability for all (of those left!) in the pcb industry in the US.
Charlie McMahon
McMahon Sales Company
P.O. Box 1024
Windham, New Hampshire 03087
Tel: 603-432-3111
Fax: 603-432-6854
Cell: 603-401-4646
e-mail: [log in to unmask]
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Valerie St.Cyr
Sent: Monday, December 19, 2005 5:26 PM
To: [log in to unmask]
Subject: [TN] ] Qualification of the Pb-free capable manufacturers
Charlie,
My *OWN OPINION* is that there is no value for solder float which will be
indicative of a laminate's ability to withstanding LF assembly in any and
all PCBs that it might be fabricated into. Any temperature used would only
be as a reference value. A PCB which is thin, has only single-sided
assembly, and has low additional mass from the added components, does not
need to have a very high solder float withstanding capability because the LF
assembly temperature will be low, relatively speaking.
A PCB which is thick, is double-sided reflow, and wave, and hand-soldered,
and has a high added mass of heat-sucking components, will need to be made
from a material having a very high thermal withstanding capability.
The increase solder-float temperature isn't "per UL" - UL is responding to
the suggestion from "the industry" that the SF temperature be 288C.
All of the laminates can pass some form of SF at 288C - the laminate need
Only pass it as a "raw" laminate; what happens after that is that many raw
laminate cores and raw laminate prepregs get pressed together, sometimes
multiple times
If the board is sequentially laminated, at which point it is a different
animal. Now some portion of the "final" thermal robustness is dependent on
the raw material, and some is dependent on the fabrication, and some is
dependent on the assembly processes ...
In my *OPINION*, in this new environment, solder float is no longer a
reliable or predictive test. It is simply a marker; only one of many; higher
is better, but how high is needed is a function of many variables, and, how
the test is conducted
makes it more or less valuable anyway. By conducted I mean: raw laminate or
fabricated multilayer. The Laminators will only sign up for tests on raw
laminates because that is all they can control - and that would be my
position also.
Oh boy ... we are in for some rollicking times.
Valerie
Charlie McMahon <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
12/19/2005 04:58 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Charlie McMahon <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] SV: [TN] SV: [TN] Qualification of the Pb-free capable
manufacturers
Hello Valerie:
Would it be fair to encourage the laminate suppliers to place within their
respective specifications sheets whether the material in question can with
stand the increased solder-float as per UL?
In addition, should not the maximum exposure temp (Td) be higher than 288
to
allow for vagaries of individual processing?
What is your view?
Charlie McMahon
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Valerie St.Cyr
Sent: Monday, December 19, 2005 4:51 PM
To: [log in to unmask]
Subject: Re: [TN] SV: [TN] SV: [TN] Qualification of the Pb-free capable
manufacturers
Inge,
This appears to be a presentation from UL showing what services they
provide to the electronics industry. Reading between the lines, it
appears that they are saying that they are increasing their solder
float temperature to 288C as a response to "industry suggested" -
they, UL, did not come up with that number.
There is nothing special about 288C other than it is 550F which is 10%
higher than 500F, which was the solder float temperature to establish
PTH reliability in concert with IPC-6012. I don't know the origin of
the setting of 500F value.
So, 288C is 10% higher than 260C, and if you believe that LF assembly
temps will be up to 260C, then you might want to test to 288C to
determine if you have any margin in the design/material/fabrication
produced PCB.
Werner,
Very few, in fact none so far, of the older or new materials that we have
tested can get to T288 => 45 minutes; we haven't even tried T320. But
unless it is polyimide I have a hard time believing it will make =>25
mins. The only caveat is that the test is not as "standardized" as having
a standard would have you believe!
Regards,
Valerie
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