Conductive coatings and conductive paints: EDAG for printed electronics and ESD
Conductive coatings, also known as conductive paints, make surfaces electrically conductive. They are used to create printed resistors, foil heaters, keyboards, and protection against electrostatic discharge. The LOCTITE EDAG series covers these applications. This article describes its structure, applications, and selection.
In a nutshell: what conductive coatings can do
A conductive coating creates a conductive path on a non-conductive substrate. This allows circuits, resistors, heating elements, and sensors to be printed directly onto the surface, and enables the targeted dissipation of static electricity. The coating's resistance describes how well it conducts electricity, and this varies considerably depending on the type of coating.
How conductive paint works
A conductive coating consists of a binder and a conductive filler. In the EDAG series, this is usually carbon in the form of graphite or carbon black; for higher conductivity, there are also silver-filled types. The coating is printed and dried, during which time the filler forms a conductive network. The characteristic value is the resistivity per square ohm (Ω/sq); low values indicate good conductivity.
Typical applications
| Application | Example |
|---|---|
| Printed resistors and circuits | Low-voltage circuits on foil |
| heating elements | flat foil heating systems |
| Membrane keyboards and touch switches | Membrane switches, keyboards |
| Flexible circuits | printed conductive traces on polyester or polyimide |
| Sensors | conductive sensor surfaces |
| ESD protection | Dissipation of static charge |
Choose the right type
Three criteria determine the choice. The surface resistance determines the function. Depending on the type, it ranges from around 20 ohms/sq to the megohm range and can be adjusted for some products by mixing, for example, LOCTITE EDAG 6017SS together with EDAG PM-404. The substrate must be suitable; common substrates include polyester, polyimide, polycarbonate, as well as paper and cardboard. The printing process also plays a role: EDAG inks are suitable for screen printing, from hand printing to roll-to-roll application. The datasheet for the respective type is the definitive source.
Processing in screen printing
- Stir the material thoroughly before use, avoiding the incorporation of air.
- Apply using screen printing; select screen and squeegee according to the data sheet.
- Dry according to instructions, typically 90 to 120 °C; higher temperatures shorten the drying time.
- Clean the sieve and device with MEK, MIBK or acetone.
- Do not return removed material to the original container.
Limits and Notes
EDAG inks are thermoplastic, with a typical continuous operating temperature of around 100 °C. They are designed as a printed functional layer, not as a decorative coating. Special coatings are available for EMC shielding of enclosures or for high-performance inks with a high silver content; we offer expert advice on these. Preliminary suitability tests are recommended, as advised by the manufacturer.
Typical mistakes
- Type chosen with unsuitable surface resistance.
- The substrate cannot tolerate the solvent in the paint.
- Dried for too short a time or at too low a temperature, resulting in unstable resistance values.
- Material not stirred, uneven layer.
- Continuous operating temperature above the type limit.
We will gladly clarify which EDAG type is suitable for your surface resistance, substrate and process using the data sheet.
