BOSTON— A new report from market research firm IDTechEx delves into the manufacturing methodologies of in-mold electronics (IME), evaluating its technical processes, material requirements, and applications.

The report, In-Mold Electronics 2023-2033,” includes 10-year market forecasts by manufacturing methodology and application sector. It also provides a detailed evaluation of competing approaches, such as functional film bonding, and the merits of including components such as LEDs within IME parts, IDTechEx said in a release.

Smooth, functional surfaces that provide touch sensing, often with backlighting, are becoming increasingly common in applications from vehicle interiors and domestic appliances to medical devices and aircraft seating. Rather than relying on a mechanical or membrane switch, these surfaces use capacitive touch sensing—the same principle used in smartphone displays. But capacitive sensing and backlighting require electronics behind the decorative exterior surface, the company said.

Such surfaces can be achieved through in-mold electronics, an emerging manufacturing approach that promises to make functional surfaces cheaper, lighter, and more aesthetically pleasing.

What is in-mold electronics?

IDTechEx describes in-mold electronics as “a manufacturing method in which at least some of the electronics are subjected to a molding process.”

Typically, this starts with screen printing the desired pattern of conductive ink onto a substrate (often polycarbonate). These conductive patterns enable capacitive touch sensing. Next, a decorative layer is applied to the front, and the conductively patterned substrate is thermoformed to produce the required curvature. A subsequent injection molding step is often applied. This approach of integrating electronics into the molded part contrasts with conventional electronics manufacturing techniques, in which decorative user-facing parts would be molded, and a printed circuit board (PCB) mounted onto the back afterward, the company said.

Why risk subjecting the electronics to this molding process when a PCB behind a decorative surface would often suffice? Depending on the approach used, IME reportedly enables a weight and material consumption reduction of up to 70 percent versus conventional mechanical switches. Also, because fewer individual parts are required, assembly and associated supply chains can be simpler.

Given these advantages, along with growing engagement from suppliers and integrators, IDTechEx said it forecasts the in-mold electronics parts market that incorporates surface-mount device (SMD) components to reach approximately $2 billion (USD) by 2033.

What are the competing approaches?

Within the umbrella term of “in-mold electronics” are many subtly different manufacturing approaches. Establishing which approach has been used is often tricky because the resulting functional surfaces look extremely similar. Two key variables are whether and at what point SMD components, such as LEDs, are mounted, and whether injection molding is used, the company said.

Arguably the most comprehensive approach to IME, developed by Tactotek and termed IMSE (in-mold structural electronics), involves mounting SMD components on a flat substrate prior to thermoforming. This is followed by injection molding, embedding the components and conductive traces in plastic. The process results in a robust part with fully enclosed electronics, potentially including an integrated circuit, according to IDTechEx.

A competing strategy, the company said, is to mount the SMD components onto an already thermoformed part and forego the injection molding. This requires a thicker polymeric substrate to provide sufficient rigidity, which generally reduces the degree of distortion and curvature that can be introduced via thermoforming.

Furthermore, SMD components can only be mounted via pick-and-place on regions that remain flat. However, for many applications, only slight curvature around the perimeter or in other specific locations is required. And because mounted components will not be subjected to the heat and pressure associated with molding, the material specifications and design rules may be more forgiving, the company said.

The simplest approach to IME, according to IDTechEx, is to omit the SMD components altogether. Decorative surfaces with integrated capacitive touch can be produced relatively straightforwardly by first screen printing conductive ink, and then thermoforming the substrate. Subsequent injection molding is optional. Although these parts would require conventional electronics for backlighting, they represent an intermediate step between purely decorative and fully functional surfaces that can meet the needs of simpler use cases, the company said.

What does the future hold?

The wide variety of competing manufacturing approaches to in-mold electronics doesn’t imply a Darwinian scenario with only one winner. Each approach offers a different balance of cost, form factor complexity, functionality, robustness, and size/weight reduction that can meet a particular need. Overall, IDTechEx said it envisions a gradual trend towards greater functionality integration because it offers the most scope material and weight reduction, but with greater adoption barriers than simpler manufacturing approaches.

A map of possible IME manufacturing methodologies. (Graphic: IDTechEx)