FAQs - Membrane Touch Switch Materials

Most MTS Problems Can Be Put in One of Two Categories, Printing and Drying

Basically, a Membrane Touch Switch (MTS) is a self contained screen printed very thin keyboard.  It is constructed of several layers.  These consist of a Graphic Layer, a Membrane Layer with Ag print, the Tactile Layer, a Static Layer with Ag print and the mounting Rigid Layer. 

  1. What are resources for screen printing of conductive inks and testing of MTS circuits? 
  2. What affects the thickness of the print?
  3. Why do I have postage stamp edges on my prints?
  4. Should I use polyester or stainless screen mesh?
  5. Why do I have high resistivity? 
  6. How do I know if my MTS prints are fully dry?
  7. Can I solder to polymer Ag?
  8. Are DuPont MTS materials UL certified?
  9. Can I use DuPont inks on polycarbonate film?
  10. How do I measure resistivity?
  11. Does DuPont offer a UV Ag ink?
  12. Can I build switches with a cross-over in the design?
  13. Can I use Carbon as a conductor?
  14. Is there any Ag that is migration resistant?
  15. Does DuPont have a Carbon overprint product to print over the Ag?

  1. What are resources for screen printing of conductive inks and testing of MTS circuits? Please click here for a link to www.sgia.org or www.astm.org
  2. What affects the thickness of the print? Screen mesh, squeegee pressure, snap off, print speed, with screen mesh having the most influence.
  3. Why do I have postage stamp edges on my prints? Screen bias, squeegee pressure, printer set up and emulsion quality are all possible causes.
  4. Should I use polyester or stainless screen mesh? Either one should work well. Use the one you are comfortable with.
  5. Why do I have high resistivity? Thickness too low, drying temperature too low, not enough drying time, poor exhaust in dryer. A thicker print will result in lower resistance but additional drying may be needed due to the increase in material printed.
  6. How do I know if my MTS prints are fully dry? For Ag, measure resistance, place in oven at drying temp for 30 min, measure again, if change is >10% drying was incomplete. Other MTS products should be fully dry when employing the same profile that gives acceptable results for the Ag.
  7. Can I solder to polymer Ag? Soldering to most polymer Ag is not recommended. The high temperature will degrade the polymer.
  8. Are DuPont MTS materials UL certified? No, DuPont cannot certify its materials. However these materials have been used in circuits that were UL certified.
  9. Can I use DuPont inks on polycarbonate film? Contact us for product recommendations.
  10. How do I measure resistivity? Divide the length of your conductive line by its width. This will give you the number of squares. Measure the resistance of that line and divide it by the number of squares. This will give you the ohms per square. Now multiply the ohms per square by the dry print thickness in mils. A conductive printed line 50 mm long and 0.5 mm wide will have 100 squares. If the total resistance of that line is 25 ohms then you have 0.25 ohms per square. Then 0.25 ohms multiplied by the thickness of 0.6 mils gives you 0.15 ohms/square/mil resistivity.
  11. Does DuPont offer a UV Ag ink? No, our assessment of this technology is that building reliable circuits with UV Ag is fraught with difficulty.
  12. Can I build switches with a cross-over in the design? Yes, when the first Ag is thoroughly dry, two prints of DuPont 5018 UV Dielectric can be used to successfully insulate the second cross-over Ag from the first. Two prints with a total thickness =/> 1 mil are necessary.
  13. Can I use Carbon as a conductor? Yes, but Carbon is higher resistance than Ag. Blends of Carbon and Ag are also available. Please click here to see the Selector Guide.
  14. Is there any Ag that is migration resistant? Contact us for product recommendations.
  15. Does DuPont have a Carbon overprint product to print over the Ag? Contact us for product recommendations.

 

Please note: Not all products are available in all regions. Contact us to discuss your specific needs.