for what it's worth, I have added my thoughts on the subject after Dewey's
(see below)





"Whittaker, Dewey (AZ75)" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]

        To:     [log in to unmask]
        cc:
        Subject:        Re: [TN] board material for high temp
James and others,
You have had some good responses, but as Richard said when he quoted Sir
Doug,"It depends", is still the best answer. It depends on the layer
count, smallest PTH, smallest via, aspect ratio, thermal management of
your design, number of reflow processes prior to ship, max reflow
temperature[eutectic vs. RoHS compliant( Lead-Free)], time above
liquidness, need to support rework, life cycle (1-3 years; 5-7 years;
20+ years) and end use environment.

As it stands right now, going up the scale in a slash sheet sort of way,
you have the following:IPC-4101/21, /24, /26, /121, /124, /101, /99,
and my personnel favorite /126.

The attributes that are key are as follows:
* Tg - I favor minimum 170 C, others agree a minimum 150 C is adequate.
>>> As your layercount and thickness increase you should be
    looking at 170C. This is a "tricky" requirement, in that if
    you do not specify the test method, you will never really
    know what you have ... I favor 170C by TMA; which should be
    about 180C by DSC and 200C or better by DMA.

* Moisture - 0.5% or less
>>> This will be critical at these temperatures!

* Thermal Resistance
  T260 - 30 minutes minimum
  T288 - 5 minutes minimum( some believe 2 minutes is sufficient)
>>> I'm not sure that 2 minutes is sufficient; 5 should be
  achievable; should be the minimum

  T300 - AABUS( as agreed between user and supplier)

* Decomposition Temperature - I would like 350 C ( 5% wt. loss) general
consensus 330 C minimum
>>> Like T288, as your design complexity increases, you need better
    decomp temps.  Also, you should see the plots.  You want to know
    the 2% wt. loss temp and 5% wt. loss.  I don't know what the
    temp should be for 2%, but for 5% I also like 350 (maybe 340, but
    not 330 - unless you have a not too demanding application)


* Z Axis CTE - I want 3% or less, general consensus 3.5% maximum
>>> less is better; they should all be able to be 3% or less

* CAF Resistance - AABUS
>>> this is really hard to specify!

* Curing Agent - Although this is a dicy subject, I'll mention it
anyway. Phenolic cure systems presently outperform traditional FR4
formulations as it pertains to maintaining functionality while being
exposed to a greater number of higher thermal excursions.
>>> This isn't a "functional" specification, but rather an indication
based on current thinking: non-dicy laminates are doing very well for
lead-free assembly conditions; but does that mean that dicy laminates
will never be able to be lead-free? not true - depends on your
application.

>>> Unfortunately, with "lead-free assembly" processing, life just
got a whole lot harder. For awhile, anyway, it will be difficult to
know what is going to be OK, or not, without specific trials on
specific designs manufacturered by specific fabricators and run on
specific assembly lines - we simply have not tested all combinations
and permutations as yet ... and process control at assembly will also
take on even more importance. <<<


The Rev B of IPC-4101 will include additional rhetoric, as well as the
new slash sheets, to help you make an informed choice as it pertains to
laminate selection, but it can not do it alone. IPC-6012, IPC-2221,
IPC-600 and the Via Protection Task Group will also have to be revised
for them to be an effective reference source to deal with all the new
performance requirements of today's Market Place. I will, with others be
working to make that happen.
Chairman of IPC-4101
Wannebee Poet Laureate of Tech-net
Dewey

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of James TerVeen
Sent: Wednesday, November 02, 2005 12:14 PM
To: [log in to unmask]
Subject: [TN] board material for high temp

What does everyone us for board material for High temperature solder
applications.   We have a new product that will require the use of high
temperature solder.   Will the use of conventional FR4 be sufficient.

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