Printing Instead of a PCB – How to Simplify IoT Device Design

When building IoT devices, designers often face the same problem: how to fit more features into less space, while keeping the device light, cheap and fast to assemble. Printed electronics offer a clear solution: skip the traditional PCB when you can print the circuit instead.

What is printed electronics?

Printed electronics is a method of creating electronic layers by printing conductive, insulating, sensing or protective inks on flexible materials. These can include PET films, TPU, paper, fabrics or even biodegradable foils. The key advantage is that you get thin, light and flexible electronic parts that can be built directly into a product’s surface or housing.

There are different printing methods depending on your needs:

Screen printing – best for large-scale production with layer thickness of 10–50 μm. It is used to print conductive, insulating or heating inks.

Inkjet printing – used for thin layers (<1–5 μm) with high precision (lines as small as 50–75 μm). Mostly used in prototyping or for complex shapes.

Pad or transfer printing – good for irregular or 3D shapes like buttons or curved housings.

Sheet-to-sheet (S2S) printing – this is LC Elektronik’s specialty. It prints on single PET, PC, TPU or paper sheets. It gives great accuracy (±20 µm) and is used to make HMI components, sensors, medical strips and touch panels.

Roll-to-roll (R2R) printing – used for very large volumes, like RFID tags or heating films. It’s fast but needs big investments and longer setup times.

Printed electronics can replace traditional PCBs, connectors and wires. It can also be combined with graphics and housing layers, which makes it perfect for IoT, wearables, automotive and medical devices.

Materials used

Conductive inks: silver (e.g. LOCTITE ECI 1011), carbon, copper
Substrates: PET (50–175 µm thick), TPU (for wearables), biodegradable paper
Dielectric and resistive inks: for resistors, heaters, or insulation

Use case: test strips for glucose meters

One of the most precise uses of printed electronics is in blood glucose test strips. These are Class IIa medical products and must be very accurate and repeatable.

A typical test strip includes:

PET film base: 175 µm thick
Silver ink layer: (e.g. Dupont 5025 or LOCTITE ECI 1010)
Graphite sensing layer: (e.g. Acheson Electrodag 423SS)
Lamination: clear PET or PC film
Cutting: laser or mechanical (e.g. 35 mm × 5 mm × 0.3 mm strips)

At LC Elektronik, we make these strips with sheet-to-sheet technology. We print each layer with ±50 µm accuracy, then dry, laminate and cut them automatically. This gives very high quality and repeatability, which is especially important for medical products. It also allows flexible production.

When to use printing instead of a PCB?

Requirement	Printing	PCB
Small size	✔	✔
Flexibility & bending	✔✔	❌
Lightweight	✔✔	❌
Complex logic circuits	❌	✔✔
Prototyping and fast changes	✔	✔
Integrated HMI functions	✔✔	❌

Design tips

Design layers in DXF, CDR or AI formats.
Use DXF for technical design – it works with CAD and CNC systems and is good for screen printing. CDR (CorelDRAW) or AI (Adobe Illustrator) are better for graphic layers like masks or UI panels.

Keep minimum spacing between printed lines: ≥ 0.4 mm for screen printing.
Due to screen mesh limits, lines should be at least 0.4 mm apart to avoid ink bleeding or short circuits. Some setups allow thinner lines, but they need careful tuning. Safe range is 0.4–0.6 mm for repeatable results.

Silver ink conductivity: about 10⁴ S/cm, surface resistance 0.01–0.1 Ω/□.
Silver inks have great conductivity and are perfect for power lines and sensors. Thicker and wider lines have lower resistance. For power use (e.g. heaters), make traces wider (1.5–2 mm) or use two printed layers with drying in between.

Dry printed inks at 120–150°C for 5–10 minutes.
Most silver inks need to be cured in this range. Use tunnel ovens or IR lamps. PET is safe up to 150°C. For softer materials like TPU, use 120°C and longer time. Do not overheat beyond the glass transition temperature of your base material.

Summary

Sheet-to-sheet printed electronics is a real alternative to PCBs for many IoT projects. It’s ideal when you need precision, repeatability, flexibility, and multilayer integration in a small space. At LC Elektronik, we specialize in this technology and help designers from the first sketch to full production.