PCB | July 21, 2008
Replacing printed silver with copper
The cost of silver tends to increase over the years and there is concern that it is a biocide. Indeed, it is far less abundant than the indium that printed electronics experts are trying to replace because of its cost escalation. The spot price of silver is up over 50% in the past 12 months and it continues to trend upward because silver supplies are falling fast while demand from China, India, Russia and Eastern Europe is climbing.
Yet silver is printed in a huge number of products today from UHF antennas in approaching billions of RFID tags yearly, membrane keyboards, battery testers on batteries and other printed electronics and electrics. Ironically, silver has replaced the more abundant copper in many of these applications because the copper, while having excellent electrical conductivity, had to be slowly electrodeposited and wastefully etched afterwards. In the past eight years, several organisations have declared that they can print copper. But there are problems including which copper precursor ink to use, poisoning of circuits, oxidation making interconnects troublesome, high temperature needed to anneal copper precursor inks, their toxicity and resulting conductivity being much less than bulk. Read the full article by Raghu Das, at IDTechEx