Syracuse, NY — Circuit boards may get a whole new pedigree and production methodology because of an amazing discovery by PCB veteran Robert Tarzwell working in his laboratory at DMRPCB — literally a cottage industry site. It's the stuff of Silicon Valley garage startups: Tarzwell has made a momentous discovery that can revolutionize the way printed circuits are fabricated. At the same time, this new discovery will advance the cause of a greener planet. He calls his breakthrough "Solution X" and while he's very close-mouthed about what it is exactly, he's shouting from the rooftops about what it does.
|Inventor and PCB expert Bob Tarzwell checks resistance measurements using new ?Solution X?. |
In effect, he has created a room-temperature superconductor, or something close to it, because SX has such incredibly high conductivity that a tiny amount of it added to silver ink will result in a 4X increase in the ink's conductivity. Suddenly, printed circuits can really be printed instead of being etched, a process that for years has resulted in all those toxic waste products that have so bedeviled the PCB industry.
According to Tarzwell, the contents of Solution X are so conductive, a single gram of it can reduce the resistance of 100 grams of silver ink by a factor of 4. Silver has a conductance of 62.5 S/cm.; copper is less conductive at 59.5 S/cm.; the conductivity of individual particles in Solution X is between 200 to 1000 S/cm.
Using this additive, printable silver inks can now compete directly with copper, and the requirement for expensive, polluting, plating chemistry, etchers and electroless lines disappears. Tarzwell has screen printed the dielectric layer, then screen printed the traces and filled the drilled through-holes with silver inks creating 4-layer "green" PC boards. Through holes were created by drilling the initial hole the size of the pad, filling with a thicker silver ink, curing and then drilling the smaller through hole in the silver. A reliable and tough 3-4 mil wall of silver is just as effective as electroless and copper plating.
Interconnections between individual layers are created by leaving an open area in the dielectric and the next silver trace simply drops down through this open area and connects to the exposed layer. Silver conductor printed electronics can replace a reasonable percentage of existing PCB designs at a lower manufacturing cost and most importantly, the process is very green. The silver conductors can be directly soldered with low temperature, lead-free solder, eliminating the final finish chemical baths.
Commercially Ready Soon
The first side-by-side test comparison utilized real world silk screening of identical lines on FR4. The low temperature fusing test silver ink as supplied, measured a resistance of 3.8 ohms. The addition of 1 percent of Solution X decreased the printed resistance to 0.9 ohms. The tests were repeated with two different silver inks with similar results. Further testing will refine Solution X and hopefully further improve its resistance lowering ability. Tarzwell expects the first commercial product to be available in a few months.
To work with the low resistance silver ink Tarzwell has created a ceramic Nano dielectric ink, with very high thermal conductance. The first use of the new ceramic dielectric is in high powered LED thermal boards. A thin layer of the ceramic dielectric ink was screened onto an aluminum heat sink sheet. Silver ink enhanced with Solution X was screened on as the conductor traces and fired at 150°C for 5 minutes to fuse the silver. Low-temperature solder had to be used to connect the components, since lead-free solder's high temperatures will melt and ball up the silver traces.
What was at first a frustrating byproduct of the experiments was the high thermal conductivity of the new material. The thermal conductance of the thin ceramic dielectric layer was so great, it was impossible to solder parts to it. When the soldering iron was touched to the board, the tip temperature dropped so significantly that the solder on the heated tip froze solid. The problem was solved by a simple preheat of the panel, after components were added, to allow proper soldering. The thermally conductive dielectric ink is another product that will soon be available in an R&D kit for beta shop testing.
To enable the printing of finer silver ink lines, Tarzwell has created what he calls "the silver bullet" — a photo-imageable, ceramic, dielectric layer which is imaged and exposed with the trace pattern. The board is developed creating trenches which are filled with the low temperature fusing silver ink. The trenches accurately define the wall of the silver trace. The three surfaces entrapping the silver provide for stronger fine trace adhesion to the board. Silver bullet technology can be utilized for high layer count multilayers, HDI and very fine line circuits while lowering the overall manufacturing cost. Layers are interconnected with silver ink micro vias as well as silver ink through holes. Silver bullet technology will allow a PC board shop to manufacture just about any circuit used today, but in a low cost, green version.
R&D sized test kits will soon be available from authorized distributor for the new products from Caledon Controls Ltd.
Contact: Caledon Controls Ltd., 3200 Ridgeway Drive, Unit 13, Mississauga, ON, Canada L5L 5Y6 905-569-8666 or 905-569-1917 fax: 905-569-0722 or Robert Tarzwell 315-585-6496 E-mail: firstname.lastname@example.org