Conductive Ink Traces June 14, 2006
Conductive ink, for example the Dow Corning PI-2000 series of Silver Polymeric Interconnect Materials, can be used to print conductive circuit traces. Generally, the ink is applied using a screen printing technique, with typical print thicknesses of 25 um to 40 um. Sheet Resistivity is specified in milliohms/square at a 25 um print thickness and varies from 8 to 81 for the currently available inks. For comparison, copper has a Sheet Resistivity of 0.68 milliohms/square at a 25 um thickness.
The Sheet Resistivity can be used to calculate the resistance of the printed traces as follows:
Resistance = Sheet_Resistivity*(Length/Width)*(Ref_Thickness/Thickness)
where "Ref_Thickness" is the thickness at which the "Sheet_Resistivity" is specified in the ink's data sheet and "Thickness" is the actual thickness of the ink you are printing.
Tips:
- Resistance per inch can be calculated by enter a length of 1 inch.
- If cookies are enabled, the form will return to its previous state upon your next visit, so your unit preferences etc. will persist.
Required Inputs:
| Width | ||
| Length | ||
| Thickness | ||
| Reference Thickness | ||
| Sheet Resistivity | milliohms/square |
Results:
| Resistance | Ohms |
- Posted in : Calculators, Electrical Engineering, PCB
- Author : Brad
Comments»
this is good …
If I have seen this site one year before!!!!!!!!!!! I became one the super PCB Designer in India now
Satya,
I wish you all the success! With your enthusiasm, you won’t have any problem.
Brad
Thanx for ur reply/encouragement…
keep sending the stuff regarding PCB Designing
my id is
leo.reddy@gmail.com
Can conductive ink be formulated with a resistance sufficient to generate heat? In other words, print a small heating element on a non-porous substrate such as cardboard or plastic sheet?
Jon,
It sounds feasible, but it could be tricky. Depending on how much heat you want, the ink might start to flake or burn. I don’t have the specifics on what type of inks would be best.
Brad
Thanks for the reply - who does have the answers? I only need 40 C for an hour or two, using 3 3V coin type batteries, so flaking should not be a problem.
Jon,
Yes you can use these inks for heating. 40C is no problem. We use them to heat
I am wondering using inks for heating to 40C, the total resistance of 0.8 ohm in total is good enough with 3.3 V voltage applied? What is the heat capacity of the conductive ink?
Josie,
You need to decide how much temperature rise you need and how much surface area you have. Then you can calculate the power needed. Per reference [1] page 13, in still air, the power needed is approximately:
Power = Temperature_Rise*Surface_Area/1000
Units: (cm, W, degrees C)
Then, find the combination of voltage, current, and resistance to get the power where:
Power = Current*Voltage
Voltage = Current*Resistance
Brad
[1] “Constructing Your Power Supply - Layout Considerations”, by Robert Kollman
http://focus.ti.com/lit/ml/slup230/slup230.pdf
I found a specsheet revised on April 1st, 2005 (http://mfc.engr.arizona.edu/safety/MSDS%20FOLDER/PI%202000%20Highly%20Conductive%20Silver%20Ink.pdf). I would recommend finding a recent specsheet (from Dow Corning) and reading it before use. Assuming it is authentic, the following may be relevant:
Section 3-Hazardous Decomp. Products: “Thermal breakdown of this product during fire or very high heat conditions may evolve the following hazardous decomposition products: Carbon oxides and traces of incompletely burned carbon compounds. Chlorine compounds. Metal oxides. Hexamethylene diisocyanate. Hydrogen Cyanide. Nitrogen oxides. Formaldehyde.”
Section-7 Handling & Storage: “Free isocyanate and MEKO may be released when this product is heated above 130 degrees C (266
degrees F).”
-Regards
Hi All,
I am looking to screenprint a heater with silver ink. Any ideas on resources to design the layout? I am in the screenprint industry and not a PCB designer or engineer.
Thanks,
Fred
can you use these inks to arc like electrodes??
let’s say I have 50KV and I want to arc across 1.3 inch gap
will the inks burn off??
Scott,
That is really a question for the ink vendors, but I am guessing that there will be some burn rate for any electrode under those conditions. Also, be careful not to kill yourself!
Brad
Hi - I’m trying to learn about this stuff. In your formula, please explain the thickness and reference thickness
If my logic is correct, Reference thickness, you’re refering to the thickness spec on the ink supplier’s data sheet. Correct me if I’ m wrong.
lac,
Good question, and you guessed it right. I added the definitions into the text of the post above. Thanks!
Can you tell me where I could find vendors to make 8″x10″ two sided pcb’s (1 each) using this process, must be inexpensive?
Hi Pat,
Conductive ink is not a mainstream PCB manufacturing technology. It has mainly been used in certain niche applications such as automotive glass heating/defogging, smaller-scale hybrid circuits printed and fired onto ceramic substrates, component manufacturing (e.g. resistors), membrane switches, and PCB repair. It usually contains silver and is not cheap. The resulting conductive ink traces are relatively high in resistance, are generally not as durable or solderable as copper clad traces.
That said, I have no specific vendor recommendations, but if anyone does, let us know.
I am wondering using inks for heating to 40C, with a 18V voltage applied and 2000 mA, is it possible to get this temperature? does non-colour inks exists?
please help me, I need an answer as soon as possible.
thanks
Hi John,
That depends. What is the ambient temperature, material, and surface area to be heated? Is there air flow involved, and if so, how fast? Please describe any other details about the application you can.
hi Brad,
I want to use thermochromic paints which change the colour with temperature in a slot car. I want to use the conductive ink to get the temperature needed for this application.
The ambient temperature is 22C and the material is ABS plastic. Is not necessary that air flow has to be involved but imagine that you are playing with the slot car so, there’s air flow involved. the surface that I want to heat is 8×6 cm.
Thank you very much Brad.
Hi John,
It looks feasible. According to [1], the thermal resistance from a surface to ambient in still air is approximately
Theta_SA = 1000 (cm^2*C/W)
In your case, area = 6×8 cm^2 = 48 cm^2, and temperature rise = 40C – 22C = 18C. So, the required power is
P = Area*T_rise/ Theta_SA = (48 cm^2)*(18C)/(1000 cm^2*C/W) = 0.864 W
You have (18 V)*(2 A) = 36 W available, so it looks doable. You just need to design the heater to have a resistance of R = V^2/P = (18 V)^2/(0.864 W) = 375 Ohms. You can use the calculator and/or formulas to be able to get to the desired resistance based on the sheet resistivity of the conductive ink of your choice by adjusting the shape. I think to get 375 Ohms, you will need a fairly high resistivity ink and a long thin serpentine trace.
[1] http://focus.ti.com/lit/ml/slup230/slup230.pdf
Thanks Brad!
You had answered my question perfectly! It helps me a lot! I only have to prove this and verify that it works properly. my last question is:
does transparent conductive ink exist?
thank you very much again.
John,
I don’t know if transparent conductive ink exists. I have only heard of silver or carbon types.
Brad,
thank you again. I have found some information about transparent conductive inks. Do conductive inks in contact with plastic get cold quickly after the application? I mean, if I heat to 40 C, can I get cold again in a short period of time?
John, Cooling without forced air tends to be a slow process. I am guessing ~10 seconds. The cooling time will be a function of the heat capacity of the plastic, the ratio of thickness to surface area, and air flow speed. In your case it might be easier to determine experimentally. For example, you could dip a sample in 40C water and let it heat up, then remove it and observe the cool down.