Nope, they are excrement from Nanites.
Bob
Sent from my iPad
On Apr 11, 2013, at 9:29 AM, "Whittaker, Dewey (EHCOE)" <[log in to unmask]> wrote:
> I thought nano-particles were left over from the "Mork and Mindy" show.
> Dewey
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Mike Fenner
> Sent: Thursday, April 11, 2013 2:29 AM
> To: [log in to unmask]
> Subject: Re: [TN] copper nanosolder
>
> Well I am more technologist than scientist. I am also a pragmatic scepticist. In other words you can convince me with numbers but not unsupported assertions. Numbers need to be actual units, not relative to something else. Relative numbers is marketing, handy for gaining attention.
>
> So to me nano-particle science is in the same place as very high frequency circuitry. In high frequency Ohm's Law goes out of the window. Same with nanos, the ordinary rules governing physical and chemical behaviour no longer apply.
> So I am prepared to accept very low fusion temperatures for normally high MP metals, if you give me the data and circumstances under which it happens.
> Now there are silver based products on the market with very low processing temperatures. Similarly there are products using nano structures whose chemistry produces rather startling outcomes.
>
> Turning to the claims for the invention, I note 200C is at the extreme low end of claims, but not incredible.
> Doing it in copper would be significant. Not just for joining but in all sorts of areas.
> It's all lab based. Doesn't mean it can be industrialised, but clearly if it can be then its worth a go.
> Somebody somewhere thinks it's worth million dollars punt, so development is being funded.
> OTOH As I said in my earlier post, similar claims have been made in good faith or for funding, for a long time now. In fact we are well in the payoff time zone for some. Of course not all R&D succeeds, but the huge effort going into nano, added layer manufacturing, and other new stuff is unlikely to be completely misplaced.
> I think that one day people will look back at how we do stuff now in large areas of electronics and manufacturing generally, and regard them in the same way as we do tubes and point to point wiring.
> But that's a marketing forecast :)
> Some places it's already starting.
>
> Regards
>
> Mike Fenner
> Bonding Services & Products
> M: +44 [0] 7810 526 317
> T: +44 [0] 1865 522 663
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
> Sent: Wednesday, April 10, 2013 9:07 PM
> To: [log in to unmask]
> Subject: Re: [TN] copper nanosolder
>
> Hi,
>
> How does "Welding" fit into these "Sintering / Melting" processes? I recall that hot plastic iron can be welded by hitting it together with a hammer.
> And there are friction welds and cold welds.
>
> I guess it is all in the resulting grain structures? When I took a short welding class the motto was "A Weld is Stronger than the Base Items". Not sure that is always try but that was how my "Welding" was tested! I recall I at least passed the class. That was stick welding with a Lincoln welder in "Farm Shop".
>
> Bob K.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
> Sent: Wednesday, April 10, 2013 12:20 PM
> To: [log in to unmask]
> Subject: Re: [TN] copper nanosolder
>
> (posting on behalf of Gordon Davy)
>
> Bob, Denny, or Mike, since you're subscribed to TechNet, feel free to post this reaction to Zinn's abstract (and bio). Perhaps if he sees it, he'll be able to respond before his June 12 presentation.
>
> Gordon Davy
> Peoria, AZ
>
> I don't want to deprecate Zinn's work. Learning how to make copper nanoparticles and keep them from oxidizing or agglomerating is difficult.
> But I am concerned with his claim that reducing the copper particle size reduces the melting temperature to 200°C. It is true that surface atoms are not as tightly bonded to their neighbors as bulk atoms, so reducing a substance's particle size, by increasing the surface-to-volume ratio, does reduce the melting temperature somewhat below the bulk value. That is the basis of sintering, which occurs below the bulk melting temperature.
> Presumably, if the particles were small enough, no atom would have the full number of nearest neighbors - it would be all "surface." But the melting temperature for bulk copper is just short of 1100°C. That's a stretch!
>
> The particles of copper in powders sold for sintering are mostly smaller than 44 µm (-325 mesh). The process requires compacting the powder (plus
> lubricant) at 4,000 to 8,000 atmospheres pressure, then and heating at 750-900°C for 5-7 minutes (see copper-powders.com).
>
> Dr. Zinn's copper is in the form of "nano-particles," so they are presumably smaller than 1 µm. One can contemplate whether that roughly 1½ to 2 orders of magnitude size reduction is sufficient to account for the differences between the above conditions necessary for sintering and for conventional reflow soldering. A differential thermal analysis curve would support the claim that, with or without compaction, his nano-copper "solder" melts at 200°C.
>
> Consider this analysis taken from everyday observation. When snowflakes, which may have nano-scale features, fall and land, they sometimes sinter, and sometimes (when temperatures remain below about -15°C) they do not.
> People refer to that latter kind, once it has landed, as "powder" snow.
> Similarly, one cannot skate on very cold ice because the surface lacks the "liquid-like" layer to lubricate the blade. (Pressure melting is a minor
> factor.)
>
> So if dropping the temperature of ice by fifteen degrees below its melting temperature prevents sintering and skating, is it likely that copper sintering will occur at a temperature nearly nine hundred degrees below its melting temperature? As for melting, even if individual particles were to melt at such a low temperature and join to form a liquid, what would prevent the liquid, now with dimensions measuring from micrometers to millimeters, from instantly freezing?
>
> More likely, the copper particles dissolve into the tin or tin-lead plating on the board lands and component terminations (to form bronze, if the reaction goes to completion). Even if the nanoparticles are not melting or sintering, it's a clever idea, but we need to know:
> * How well these bronze connections, presumably far stiffer than those of
> a tin-based solder, survive temperature cycling. * The microstructure,
> so we can understand the attachment mechanism. * The width of the process
> window. * Whether the adequacy of the attachment can be judged by its
> appearance, and if so, by what criteria. * Whether using Zinn's solder
> at 200°C gives benefits large enough to warrant replacing Pb-free reflow
> soldering (peak local temperature up to 260°C by convection, lower by
> condensation). (For those still using SnPb solder, the conditions don't
> seem different enough to warrant consideration.) * Whether Zinn has tried
> his "solder" with non-tin land finishes such as immersion silver, ENIG,
> and ENEPIG, and NiPdAu termination finish. Since I suspect that the
> colloidal copper does not melt or sinter at 200°C, I suspect that
> it is not going to perform with Ag or Pd nearly as nicely as with
> near-molten Sn, and its reaction with Ni would be even worse.
>
> * If it doesn't make reliable bonds with all the finishes likely to
> be present on an assembly, then it is not a "drop-in replacement"
> for solder. (Yes, the designer can specify a compatible finish for the lands of the board he designs, but not the termination finish of the components he chooses. He can specify, say, immersion tin instead of
> ENIG, but must accept NiPdAu on some components.) * Maybe Zinn can add
> enough nanoparticle Sn to the formula to provide the necessary wetting
> to Pd without increasing the reflow temperature and without introducing
> a risk of whiskers from the solder itself. * The risk of short
> circuits due to whiskers growing SAC solder appears to be low, from
> SnPb solder even lower, and with Zinn's solder it may be zero. But
> regardless of the solder used, the overall risk for an assembly remains
> high due to portions of Pb-free Sn termination finish that don't get
> solder-coated.
> Here are two other ways of dealing with the risk of tin whiskers:
>
> 1. Mitigation - speculative For assemblies for which Pb is permitted, if components with a Pb-free Sn tin finish were dipped in SnPb solder paste (or perhaps a paste of colloidal Sn and Pb) and heated (before or during assembly soldering), all of the original finish might be covered with a layer of SnPb, and the assembly would then have a low risk of short circuits due to tin whiskers. The paste also might bridge.
>
> 2. Prevention - reduced to practice After attaching components by conventional SnPb or SAC soldering, a thin layer of a whisker-impenetrable metal such as nickel can be applied to the solder and the remaining
> (uncoated) Pb-free Sn finish by electroless deposition. The process requires immersing the entire assembly in the bath for a minute or two. But because electroless deposition occurs only on conducting surfaces, insulating surfaces remain uncoated, and the performance of the assembly is unaffected. (Full disclosure: Bob, Denny, and I are the named inventors on a patent application for this process - see www.ldfcoatings.com.)
>
> A few additional observations:
> * Note the irony, given the meaning of Zinn in his mother tongue, of
> him developing a tin-free solder. * Note the nine-year gap (between
> 1995 and 2004) in his bio. * The claim of "10-15x electrical and
> thermal conductivity improvements" is irrelevant: what counts is overall
> conductance, and the reduction in a connection's conductance due to use
> of conventional solder (compared to copper) is insignificant. * A
> substance's melting temperature is a thermodynamic property. Some might
> regard the reduction in the melting temperature of colloidal copper as
> "significant" or even "dramatic." But it is not "rapid" (a term that
> implies a kinetic effect).
>
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