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 === __________________________________________________ Do you Yahoo!? Yahoo! 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