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March 2003

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Tue, 25 Mar 2003 10:02:50 -0800
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Is it the CTE on Z-direction?
The CTEs on X- and Y- directions above Tg are lower for BT substrates.



-----Original Message-----
From: peter blokhuis [mailto:[log in to unmask]]
Sent: Tuesday, March 25, 2003 6:07 AM
To: [log in to unmask]
Subject: Re: [TN] FW: [TN] TCE above Tg for Dupont CB100 silver resin

Methode Electronics http://www.methode.com/mdc/via.pdf
has a similar material (their 1210) with a Tg of
190ppm/C above their Tg of 120C.  Perhaps this will be
close enough for your needs.
Peter Blokhuis


--- joyce <[log in to unmask]> wrote:
> if it is standard epoxy filled with silver, my guess
> is 3x TCE above Tg.
> With absent of data and not going to do any test
> (which I think you
> really should do the test... rather than question it
> endlessly, why not
> just pay few $ run a TMA?), I would design per 3x
> TCE above Tg, provide
> you cure it properly.  On the other hand, why Dupont
> not provide above
> Tg data? very strange...
>
> my 2 cents.
>
>    jk
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of
> Mcmaster, Michael
> Sent: Monday, March 24, 2003 5:41 PM
> To: [log in to unmask]
> Subject: Re: [TN] FW: [TN] TCE above Tg for Dupont
> CB100 silver resin
>
>
>
> I'm going to have to disagree with Guy on this.
> There's nothing that
> says CTE above Tg has to be non-linear.  Nor is
> there anything that says
> it has to be linear, especially when working with
> systems like today's
> high performance epoxy systems.
>
> There are multiple ways to define, measure, and
> determine Tg, but it is
> generally regarded as the temperature below which
> free rotations cease
> because of intramolecular energy barriers.  In other
> words, the material
> acts as a glass.
>
> Above Tg the polymer achieves what is known as
> segmental mobility.  The
> reason for this is that as you heat the material up
> it expands (the
> CTE).  This expansion results in an increase in free
> volume.  Below, Tg,
> the free volume is too small to allow segmental
> mobility, whereas above
> Tg, the free volume is large enough.
>
> The Tg the shows up as a discontinuity in the
> specific volume vs
> temperature curve.   For amorphous polymers,
> especially something like a
> cross-linked epoxy, the transition is not clean.
> Difference in cross
> link density, segment length, initial free volume
> and other factors mean
> that different sections of the material achieve the
> necessary free
> volume for segmental mobility at different
> temperatures.  As a result,
> the glass transition is usually not abrupt (like
> say, the melting of
> water, another transition).  So while the Tg is
> reported as a single
> temperature, that's rarely true.  The temperature is
> usually arrived at
> by extrapolating the specific volume vs temperature
> curves above and
> below Tg.  The reported Tg is the intersection of
> the two lines, even
> though the transition itself started below and
> continued above this
> temperature.
>
> For CTE above Tg to be restricted to "non-linear" or
> "linear" is
> unfounded.  I've seen plenty of TMA scans that
> exhibit linear behavior
> for at least some section above the Tg.  I've also
> seen materials that
> exhibit very non-linear behavior.  Much of this has
> to do with the
> highly variable structures and compositions of
> polymeric materials.  You
> have materials that are difunctional,
> tetrafunctional, mulitifunctional
> and then the co-polymer blends that tend to exhibit
> multiple transitions
> to the point where you can't find two lines from a
> TMA scan to
> extrapolate to an intersection.  In some cases, it's
> nearly impossible
> to get a good Tg determination from TMA alone and
> alternative methods
> such as DSC and DMA must be used.  But these look at
> properties other
> than volume to determine the transition and don't
> necessarily give the
> same result.
>
> And I'm guessing that you don't really care whether
> it's truly linear or
> not as along as it's a reasonable approximation of
> the CTE in the
> temperature range of interest.  In all likelihood
> you want to know how
> the material is going to perform during reflow
> soldering (from below to
> above Tg).  And maybe the properties during the
> operational life (likely
> below Tg).  So you need to know the Tg, preferably
> measured with TMA
> since that is how CTE is measured also.  You need to
> know the
> temperature range for the CTE measurements.  You at
> least want the value
> above and below Tg.  Reporting and using a CTE value
> that is the
> combination of the values above and below Tg is not
> of any practical
> value.  The material exhibits this particular
> behavior only at one very
> specific temperature during the transition phase.
> It's akin to a
> stopped watch being right twice per day.
>
> Like you, I've had no luck determining the CTE of
> CB-100 above Tg.
>
> Mike McMaster
> RF Product Engineer
> Merix Corporation
> 503-992-4263
>
>
>
>         ----------
> From:   Arbour,
> Michel[SMTP:[log in to unmask]]
> Reply To:       TechNet E-Mail Forum.;Arbour, Michel
> Sent:   Monday, March 24, 2003 6:10 AM
> To:     [log in to unmask]
> Subject:        [TN] FW: [TN] TCE above Tg for
> Dupont CB100 silver resin
>
>
>         > OK,
> > So the values for ZTCE > Tg given in the material
> specs or various
> > articles
> > are linear approximation of the behaviour of ZTCE
> >Tg . Right ??
> >
> > And the Zaxis expansion% (50 to 288C) is the
> "real" value ?
> >
> > Ref. : circuitree magazine Feb. 2001:  High
> reliability/Low CTE epoxy
> > technology,
> >
> >
> >
> > > -----Original Message-----
> > > From: Guy Ramsey [SMTP:[log in to unmask]]
> > > Sent: 21 mars, 2003 16:01
> > > To:   'TechNet E-Mail Forum.'; 'Arbour, Michel'
> > > Subject:      RE: [TN] TCE above Tg for Dupont
> CB100 silver resin
> > >
> > > TCE above Tg is non-linear. What you're asking
> for is like asking
> for
> > > the distortion characteristics of a amp is after
> clipping.
> > >
> > > > -----Original Message-----
> > > > From: TechNet [mailto:[log in to unmask]] On
> Behalf Of Arbour, Michel
>
> > > > Sent: Friday, March 21, 2003 2:52 PM
> > > > To: [log in to unmask]
> > > > Subject: [TN] TCE above Tg for Dupont CB100
> silver resin
> > > >
> > > >
> > > >         Hello Techies,
> > > >         By any chance, would you know what is
> the TCE > Tg
> > > > for Dupont CB100 silver resin ??
> > > >
> > > >         Can't get that info from DuPont's
> Micro-Circuit
> > > > Materials group in the U.S. . They have not
> measured that
> > > > characteristic they said...
> >
> >
> ---------------------------------------------------
>
=== message truncated ===


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