Silver Solution Ink Makes Faster Flexible Circuits 36
judgecorp writes "Silver-based compounds dissolved in ammonia could make finer and more flexible circuits, according to researchers at the University of Illinois. Existing inkjet based circuit printing systems use particles which are less predictable. The silver-based ink remains dissolved until the ammonia evaporates, and can be delivered through 100nm nozzles. In all senses, it's a better solution."
Re:Every fucking month (Score:5, Informative)
The fact that this new ink reaches the bulk conductivity of pure silver upon annealing is nothing short of amazing. My company has been working on some printed electronics application, and most of the conductive inks (including silver based) have conductivities that are too low to conduct any useful amount of current.
Link to the research group doing this: (Score:5, Informative)
http://colloids.matse.illinois.edu/ [illinois.edu]
Jennifer Lewis' research group here at the University of Illinois did this work.
They've got a link on that page to a youtube video that shows how to make and use this conducting ink, but it goes through Boing Boing and is down at the moment due to the SOPA protest.
Here's a direct link: http://www.youtube.com/watch?v=dfNByi-rrO4 [youtube.com]
Seriously cool work.
Re:Corrosion? (Score:2, Informative)
There's a reason copper or gold is used in circuit boards despite silver being a far better conductor.
Silver isn't a better electrical conductor than copper, it's a better thermal conductor.
Silver is tremendously better at conducting heat than aluminum, and slightly better than copper and gold. In the past, I've melted blobs of silver solder over flat aluminum heatsinks, mostly to absorb temperature spikes (to steady temperatures).
How does this new solution avoid corrosion?
It isn't really necessary to avoid the corrosion of silver in most cases (in breathable air). Unlike copper oxide (a semiconductor/insulator), or aluminum oxide (insulator), silver oxide remains a decent electrical conductor. Conducting electricity despite oxidation is why it's great for electrical connectors, because all bare metal corrodes in the presence of oxygen (except gold; most of them form protective oxide layers on the surface like stainless steel, but most oxides have high electrical resistance).
Regardless of the metal being used, you can protect the circuit traces against abrasion, shorts and corrosion with a protective coating. Tinning the traces would be an obvious choice, if the heat from soldering doesn't melt or burn the PCB material. Smearing silicone sealant across it might work, but any general purpose PCB coatings will just flake off something flexible.
Corrosion isn't always oxidation, though. Another poster mentioned silver sulfide, which is different (aka silver tarnish). Oxides and sulfides of metals have different physical properties, silver oxide conducts but other reactions may or may not. Keep in mind you'd only get silver sulfide from hydrogen sulfide (air pollution or other biological sources). So, unless you're eating off the circuit board, or expose it to smog, oxidation is the primary type of corrosion.