Processing Power for Research and University Labs

To make traces for the emerging printed electronics market, in 2005, our customers made dispersions of silver and copper nanoparticles, printing them on low-temp substrates, such as plastic and paper, and sintered them in ovens for 10-30 minutes. We discovered that we could get the same level of conductivity of printed traces with our newly developed flashlamp technology, and what took 10 minutes with ovens, was narrowed to 350 microseconds. We knew how many joules per cm² the flashlamp put out – and we knew the absorptivity of the trace. A quick calculation revealed the peak temperature of the trace was hundreds of degrees C higher than the maximum working temperature of the substrate it was in direct contact with. Since thermal processes generally progress with the exponential of the temperature at which they are maintained, that explained why the curing was so fast – but with traces that hot, why was our technology not burning the substrates?

Because light is absorbed by traces, and not by substrates, and because our powerful light pulses are so short, traces are heated before they can equilibrate with the rest of the substrate. After exposure, which is of order 1 millisecond, traces thermally equilibrate with the bulk of the substrate after 10-50ms, depending on thickness. After a few 10s of milliseconds, the traces have been processed, the entire substrate and trace stack have equilibrated, and are only a few degrees warmer than they were after exposure, with no damage to the substrate.

Even plastics are not damaged because thermal damage, especially to polymers, takes a finite amount of time – our technology operates within that window, which is generally milliseconds. PET, as one example, has a maximum working temperature of about 150C, but PulseForge tools can briefly go up to about 400C. And with our extremely rapid flashlamp, and subsequent rapid cooling, thermal conduction is provided to the bulk of the substrate. We developed a regime allowing for high-temperature processing on low temperature materials without damage!