Conductive inks

Silver conductive ink is a formulation composed of silver flakes or nanoparticles suspended in a polymer binder and solvent. After screen printing and thermal curing, the solvent evaporates and the silver particles partially sinter, forming a continuous conductive network. The resulting sheet resistivity is typically below 10 mΩ/sq, giving conductivity 100 to 1,000 times higher than carbon inks.

Silver accounts for approximately 78% of the global conductive inks market (Mordor Intelligence). This market is valued at USD 3.26 billion in 2025. VFP Ink Technologies manufactures its silver inks in France, with adjustable silver content to match the required resistivity and cost trade-off. Formulations are available CMR-free, compliant with REACH and RoHS 3.

Dielectric ink (also referred to as dielectric varnish in common usage) is an insulating formulation deposited by screen printing between two conductive layers to prevent short circuits. It is essential in the manufacture of multilayer membrane keypads, resistive sensors and crossover circuits. Typical dielectric strength exceeds 50 V/µm at a deposit thickness of 15 to 20 µm.

VFP offers thermally curable dielectric inks (80-130°C), compatible with the same curing cycles as silver and carbon inks. Their low permittivity (εr < 5) limits parasitic losses in high-frequency circuits. Formulations are tested for adhesion, humidity resistance and thermal stability in accordance with IPC-SM-840.

Piezoelectric inks contain PZT (lead zirconate titanate) or PVDF particles dispersed in a polymer binder. Screen-printed then poled, they enable the manufacture of pressure, vibration or impact sensors directly onto flexible substrates, without the assembly constraints of conventional rigid piezoelectric sensors.

Target applications include medical wearables (pulse detection, portable ECG), flexible haptic interfaces and energy harvesting in e-textiles. VFP develops these formulations in partnership with specialist research laboratories. Prototypes are available on request for projects in the R&D phase.

Four technical parameters determine the choice of a conductive ink for a given application. Sheet resistivity (expressed in mΩ/sq or Ω/sq) governs ohmic losses in tracks: the lower the value, the more conductive the ink. Substrate adhesion is measured by the cross-cut test ISO 2409: a poorly formulated ink will delaminate under mechanical stress, compromising circuit reliability.

Dynamic flexibility is critical for FPC and wearable applications: VFP inks are tested under repeated bending (10,000 cycles at a 5 mm bend radius) with a resistivity drift below 20%. Finally, the maximum admissible curing temperature is a limiting factor for heat-sensitive substrates (thin PET, paper, biodegradable films): specific formulations allow complete polymerisation from 80°C, opening access to the most delicate substrates.