Conductive inks

[vincentp]

Afternoon all,

Would anyone have any information with regards to conductive inks or any other process that could potentially replace the standard FR4 material ?

Regards,
Vincent.

 

[MacGyverS2000]

Some more info on your application would help. I will ocassionally come across an article in some of the PCB desing mags about conductive inks and such.

 

[vincentp]

What we are trying to do is basically replace the expensive piece of FR4 by "something else". We would then print on a cheap piece of ABS or such and get our circuitry made that way.

We are working in the automotive industry and we are developping inductive sensors that require TX and RX antenna.

I was wondering whether conductive ink is already used in the industry. Also what sort of conductivity do we get out of it. Is it as good as copper ? And what are the techniques to jet conductive ink on material ? I know inkjet industry is getting slowly, but is not quite there yet. (Xaar, Specctra...).

And lastly, who are the "conductive ink" people ? I have one name or two in the UK, but maybe you guys could enlight me..

Cheers,
V.

 

[IRstuff]

??? FR-4 expensive? Compared to what?

I hate to be a pest, but a search on Google for "conductive ink" got over 4000 hits. Dow Corning makes conductive inks. Also, you could use some of the metal systems for hybrids, but I can't imagine either approach being cheaper than standard copper on FR-4.

Conductive inks require either a dispenser system, which is slow, which impacts cost, or silk screen. This has to be followed by a cure, which is slow, which impacts cost.

Most conductive pastes and inks cannot tolerate standard reflow soldering, which means you have to use low-temp solder paste, which is slow, requires a longer cure cycle, which impacts cost.



TTFN

 

[logbook]

FR4 is "expensive" compared to phenolic pcb (FR2). However FR4 is more widespread so you would have to go to a specialist manufacturer to get a cost benefit. FR4 is "expensive" to machine because of the glass content. FR2 can be punched, which makes it cheaper as well. You may well need a far east manufacturer to get the rubbish type of pcb you think you want.

Copper is a metal and therefore conducts well. Carbon loaded inks are not very conductive and would be useless for power tracks. Silver loaded inks are conductive, but more expensive than copper. Bear in mind the ease of soldering to copper which may not occur with any other sort of conductive ink material. The other problem is cracking due to mechanical flexure and temperature cycling.

If the manufacturer you chose (or your own plant) decide to go this route, expect months if not years of process tuning to get the process reliable.

 

[MacGyverS2000]

Some injection molders even offer conductive inks as an extra process, printing the circuit directly to the molded item. Cost, of course, DEFINITELY outweighs FR4. I can't imagine getting much cheaper than FR4 (FR2 not permitting), and conductive inks are not the panacea you think they are.

If you're looking for TX/RX antennas, consider pre-made coils of thin copper wire glued to an FR2 board. It "may" be cheaper than etching the antennas on FR4, and won't be as subject to shrinkage/expansion as if you etched directly to FR2.

 

[Higgler]

Try Chomerics for conductive liquid materials. they make a pen to write on circuit boards with conductive ink. Epotek too. This material is generally expensive thoughy, $25 for 1-3 grams.

There is a spray also, I used it to make a 4" square patch antenna and measured very different results in an ohmic measurement across the diagonals, 0.5 to 4 ohm.

What are your antenna spec's if you don't mind me asking (I understand completely if you can't answer, but being an antenna type, I'm curious if I could come up with a cheap alternative antenna solution)
kch

 

[sreid]

In high volume production in the far east I think the cheapest solution would be etched one side FR2 with gang punched shape and holes. Get a far east quote.

 

[Comcokid]

You got to be careful using unusual process in order to chase lower cost. Screen-printed conductive inks have appeared on vehicular gauge clusters and gauge assemblies several times over the past 20 years. These took the form of ink printed directly on the plastic, or ink printed over CEM-1 / PC-75 "appliance" type board to gain additional trace routing flexibility. These disappeared as long-term problems arose - and these were used in the fairly benign driver environment of the vehicle.

You might luck-out and find a newer ink that will work. However, you indicate you are building an inductive sensor which leads me to thin you are putting the sensor in a more hostile suspension of the susupension or engine.