In-Mold Electronics: Short-Term Pain, Long-Term Gain?
This apparent discrepancy poses an important question: will the capacitive human-machine interface (HMI) components of the future be produced using IME, or will the simpler manufacturing methodologies currently in use persist?
HMI components that provide backlit capacitive touch sensing are increasingly used in multiple applications, including automotive interiors and appliance control panels. Compared to traditional mechanical switches, the reduced number of parts used in backlit capacitive touch sensors make them both lighter and easier to assemble, while the lack of inconspicuous buttons means they can be cleaned.
In contrast, the IME manufacturing process places more stringent demands on the materials. First, a conductive ink is printed on a plastic substrate, usually polycarbonate. Electrically Conductive Adhesives (ECA) are then used to attach electrical components such as LEDs. The substrate with conductive traces and mounted components is then thermoformed to produce the desired curvature, followed by injection molding to produce the complete part.
Due to the less stringent hardware requirements and lower adoption barriers compared to IME, the application of functional foils to gently curved parts to make capacitive touch switches has already reached commercialization in the automotive industry. Since both manufacturing methods result in parts with very similar functionality and therefore customer experience, how can IME compete?
The answer lies in taking into account the parts and assembly processes that the IME makes unnecessary. For example, providing capacitive touch sensing by applying functional foils means that the lighting and therefore the waveguides have to be produced and installed separately, whereas with IME they are an integral part of the component. This greater integration means that the IME will reduce the number of parts / materials and overall reduce assembly processes. The IME parts will therefore be lighter, benefiting both the range and the durability of electric vehicles.
In summary, commercial adoption of IME is currently lagging behind some of the alternative methods for producing capacitive touch surfaces. However, IME offers much greater potential for the integration of additional electronic functionality, allowing components that are smaller, lighter and easier to produce, leading to a lower overall cost (see graph). As such, IDTechEx believes its comparative advantage over methods such as the application of functional sheets will increase over time, leading to widespread adoption.