Increasingly, circuits are being added to 3D surfaces and integrated into objects using a variety of new technologies. Aerosol and material jetting allow conductive interconnects to be applied to surfaces. In-mold electronics and 3D printed electronics allow complete circuits to be integrated into objects.

With 3D electronics, electronic functionality no longer requires integrating rigid PCBs into things, and then wiring up the associated switches, sensors, power supplies, and other external components. What are some alternatives to PCB? Let's talk about them.

Surface electrons

The best way to add electronic functionality to the surface of 3D objects is laser direct structuring (LDS), where additives in injection-molded plastics are selectively activated by laser. This forms pattern that is subsequently metallized using chemical plating. LDS saw huge growth about a decade ago. It is used to manufacture hundreds of millions of devices each year.

However, despite its high patterning speed and widespread adoption, LDS still has some weaknesses that leave room for alternative methods of surface metallization.

First, it is a two-step process that may require sending parts elsewhere for plating, so there is a risk of exposing IP. Its minimum resolution in mass production is about 75 um, so it limits line density, and can only be used on molded plastics. On top of that, LDS only enables single-layer metallization, which avoids crossover phenomena, greatly limiting the complexity of the circuit.

An advantage of the digital deposition method of existing LDS technology is that dielectric materials can also be deposited in the same printing system, allowing cross-connections to be made, and thus more complex circuits to be made. Insulating and conductive adhesives can also be deposited to mount SMD components onto surfaces.

In-mold electronics

In-mold electronics (IME) offers a commercially compelling proposition, integrating electronics into injection molded parts, reducing manufacturing complexity, saving weight. Rigid PCBs are no longer needed. It relies on existing manufacturing technologies such as in-mold decoration and thermoforming, reducing barriers to adoption.

Its basic principle is to print circuit onto a thermoformable substrate and mount the SMD components using conductive adhesive. The substrate is then thermoformed to the desired shape, and filled with injection molded plastic.

IME is particularly suitable for human machine interface (HMI) in automotive interiors and white appliance control panels, as the decorative film can be used on the outer surface above capacitive touch sensor.

Although IME is likely to dominate HMI interfaces in the future due to ease of manufacture and compatibility with established manufacturing technologies. Are there any challenge? We need to develop conductive and dielectric materials that can withstand the temperatures of the thermoforming process and the heat and pressure of injection molding.

Fully 3D printed electronics

Fully 3D printed electronics is used in conjunction with SMD components to form circuits. It embeds complex multi-layer structures into 3D plastic objects. Each object and embedded circuit can be manufactured to a different design without having to make masks and molds each time.

It's hard to ensure reliability. After-the-fact repairs are not possible with embedded electronics. One strategy is to use image analysis to inspect each layer, and make any repairs before depositing the next layer.