Core Formulas

How to Calculate Ink Coverage, Trace Resistance, and Cure Energy in Printed Electronics

Work through the four calculations that govern printed electronics, from silver ink grams per panel to cured trace resistance, with real units and numbers.

Four calculations carry most of a printed electronics job: ink coverage, conductive trace resistance, cure energy, and effective roll-to-roll output. Get these right and the quote, the electrical spec, and the schedule all hold. Ink coverage starts with wet volume. Multiply printed area by wet film thickness set by your screen mesh and emulsion. A 325-mesh screen with 12-micron emulsion over mesh (EOM) lays roughly 15 to 20 microns wet. For 4.0 dm2 of printed area at 18 microns, wet volume is 0.0040 m2 times 18e-6 m, which is 7.2e-8 m3, or 0.072 cm3 per panel.

Convert that wet volume to grams and then to issued ink. Silver flake pastes run about 3.0 to 3.5 g/cm3, so 0.072 cm3 at 3.2 g/cm3 is 0.23 g wet per panel. That is the theoretical deposit. Real screen lines transfer only 80 to 90 percent of dispensed ink, so divide by 0.85 to get issued ink: 0.23 / 0.85 equals 0.27 g per panel, leaving a 0.04 g loss allowance. The Ink Coverage calculator runs this chain directly. At 700 dollars per kg for silver paste, 0.27 g is 0.19 dollars of ink per panel before scrap, which is why a few microns of film thickness swings your material cost.

Conductive trace resistance ties printed geometry to electrical spec. Resistance equals sheet resistance times length divided by width, R = Rs x (L / W). Sheet resistance is cured resistivity divided by thickness. A well-sintered silver ink at 5 micro-ohm-cm cured to 8 microns gives Rs of 5e-6 ohm-cm divided by 8e-4 cm, which is 0.00625 ohm per square, roughly 6.3 milliohm per square. For a trace 40 mm long and 0.5 mm wide, that is 80 squares, so R equals 6.3 mΩ times 80, about 500 milliohms. The Conductive Trace Resistance calculator does this; note printed silver runs 3 to 10 times the resistivity of bulk silver, so widen or thicken traces to hit spec.

Cure energy has two questions: did the ink sinter, and what did it cost. Thermal cure needs time at temperature, typically 130 C for 10 to 30 minutes for silver on PET, staying under the 150 C where PET softens. The cost side is connected load times runtime times tariff, divided by units. A 12 kW oven running 8 hours draws 96 kWh; at 0.12 dollars per kWh that is 11.52 dollars, and across 1000 cured panels it is 0.0115 dollars each. Use measured average draw, not nameplate, since heaters modulate at 40 to 70 percent duty once at temperature. The Cure Energy calculator separates total energy from per-part cost.

Photonic and UV cure change the math entirely. Intense pulsed light sinters silver in 1 to 5 milliseconds per flash rather than minutes, so runtime collapses and the substrate barely heats. If a xenon lamp bank delivers 5 J/cm2 over a 20 cm wide web at 10 m/min, energy per square meter is 5 J/cm2 times 10000 cm2/m2, which is 50 kJ/m2, or about 0.014 kWh/m2. Compare that against thermal cure per part before assuming photonic always wins. It usually wins on throughput and substrate margin, but capital and lamp replacement belong in a separate cost pass, not this energy calculation.

Effective roll-to-roll output strips uptime and yield from nameplate speed. Raw rate is units printed divided by run time. A line printing 1200 devices in 8 hours runs 150 per hour raw. Multiply by line efficiency, which is uptime times yield. At 85 percent uptime and 90 percent first-pass yield, effective efficiency is 0.85 times 0.90, or 0.765, so effective output is 150 times 0.765, about 115 good devices per hour. The Roll-To-Roll Output calculator does this, and the gap between 150 and 115 is the 35 units per hour your splices, threading stops, and scrap are quietly costing.

Registration margin is the go or no-go check before committing a roll. Compute margin as achieved accuracy minus required tolerance, normalized to a reference feature. If your press holds 50 microns layer-to-layer, the design allows 75 microns, and the pad is 300 microns, margin is 25 microns over 300, about 8 percent. That is thin. Web substrates like PET stretch in the machine direction under tension and heat, so a static margin under 10 percent rarely survives a full roll. The Registration Tolerance calculator flags this; evaluate the tightest critical layer pair, not an average, because the worst pair governs the whole run.

Chain the numbers to sanity-check a plan. Take issued ink of 0.27 g per panel, trace resistance of 500 milliohms against a 1 ohm spec, cure at 0.0115 dollars per panel, effective output of 115 panels per hour, and registration margin of 8 percent. The resistance and energy pass, but the 8 percent registration margin is the weak link that will drive most of your scrap. Fix inputs at the source: weigh a printed coupon for real deposit, pull cured resistivity from a four-point probe, and use observed rather than nameplate line speed. Every one of these feeds the cost and benchmark work, so getting the raw math clean pays off downstream.

Published 2026-07-01.