May 21, 2019

How to Design an IoT Device for 3D Printing

From smart homes to smart cars, smart watches, and smartphones, internet of things (IoT) devices are a fixture in our daily lives and will play a greater role in the future. With the range of applications broadening, additive manufacturing offers some real advantages for prospective IoT designers who are interested in developing unique IoT devices.

Learning how to design an IoT device

IoT devices integrate a number of functions that are normally placed in separate boards.

IoT devices require a number of standard capabilities, and more designers will need to think about these capabilities as they move into the IoT space. Fortunately, learning how to design an IoT device is not significantly different from designing other similar PCBs. IoT devices integrate many functions that were formerly separated into different boards with the goal of providing sensing, human-computer interaction, and communication in a single device.

Sensors and an Interface

Any IoT device requires some type of interface that allows humans to interact with the device. Touch screens or keypads are common examples of interfaces for controlling IoT devices. These components are widely available as commercial off-the-shelf (COTS) components that can easily be added to a PCB for an IoT device.

IoT devices typically contain a number of sensors for interacting with the external environment. Examples include touch sensors, sound or vibration sensors, environmental sensors, and electrical sensors. These sensors are purely analog devices, thus designers will need to convert these analog signals into digital data directly on the board using an MCU, FPGA, CPLD, or another integrated circuit.

Because IoT devices use both analog and digital signals, designers need to follow the standard design practices for mixed-signal devices. This involves separating analog and digital sections of the board while maintaining ground plane connectivity throughout the device. The return to ground should be placed so that digital return signals in the ground plane do not travel beneath analog components.

3D printing provides a number of advantages in sensor design in that conductive elements for sensors can be printed directly on the board without using an etching and plating process. This can be especially useful for capacitive touch sensors, strain sensors, or chem-resistive environmental sensors. Connectors may also be 3D printed directly onto a board, allowing COTS sensors to be easily added to a 3D-printed IoT device.

Wireless Communication Capabilities

Nowadays, it’s difficult to find any IoT device that is hardwired to a modem using an Ethernet cable, so you’ll need to include wireless communication capabilities in your PCB. There are several options available for adding these capabilities to your device, depending on the wireless protocol you need for your device.

One option for incorporating wireless capabilities is to include a COTS antenna and transceiver in your board. Some antennas, such as a rubber ducky or patch antennas, will need to connect to your board with a small coax cable. Alternatively, you can manually design a printed antenna for your board, such as a microstrip, inverted-F, or bow-tie antenna. As 3D printing naturally allows conductive elements to be printed directly on a substrate, it is adaptable to antenna designs for IoT devices.

You will also need to choose between an active or passive GPS antenna. Active antennas come with a low-noise amplifier (LNA) built into the antenna module, in contrast to a passive antenna. These antennas typically sit on their own board and will need to connect to your device with a coax cable. Some bow-tie antennas are quite useful as they can also provide WLAN communication alongside GPS. You’ll also need to include a receiver for your GPS antenna module. Some COTS receivers are functional as they include a 50 Ohms matching network for your antenna, so you won’t need to manually design a matching network.

Whether you want to include a custom antenna for LAN/WLAN communication, GPS, Bluetooth, or some other protocol, a custom-designed printed antenna can be 3D printed directly on your substrate with the right additive manufacturing system. Using an inkjet system that deposits nanoparticle conductive inks provides high-precision printing of an antenna in any geometry, including non-planar options.

Other Advantages of 3D Printing IoT Devices

Additive manufacturing systems are still incapable of printing a rigid substrate with weave like FR4, but the right aerosol or inkjet system can print a polymer dielectric substrate that simulates FR4 electrically and has similar electrical properties. This class of materials provides certain advantages in RF applications. PCBs for RF devices on FR4 require a special laminate on the surface layer to reduce absorptive losses, which is why some high-frequency devices are designed on ceramic alumina or aluminum nitride. A printed polymer substrate may offer lower losses at high frequencies compared to FR4, which are comparable to losses observed in specialized ceramic materials.

Antennas that require a ground plane will need to be printed on multilayer boards, where the ground plane resides in an interior layer. A 3D-printed polymer board only requires a single layer-by-layer deposition process, where conductive elements and the substrate are deposited in a single run. In contrast, rigid multilayer PCBs require dozens of deposition, etching, plating, and pressing steps, which increases fabrication time and costs. This makes rigid boards prohibitive for rapid prototyping unless you order an expensive low-volume production run from a traditional PCB manufacturer.

An IoT device with a 3D printed antenna and transceiver module

A 3D-printed antenna and transceiver

The ability to produce and test a single IoT device in a matter of a day with an additive manufacturing system allows designers to rapidly build a prototype and test its performance. IoT devices can be 3D printed 90% faster than a traditionally manufactured device. Design revisions can be quickly formulated and implemented as necessary. The layer-by-layer deposition process does not limit sensor and antenna designers to working with purely planar designs. Unique architectures can be fabricated with a 3D printer, including non-planar or repeating elements.

Apply 3D Printing Rules to How You Design an IoT Device

Every additive manufacturing system has its own design rules and limits. One important limitation of any additive manufacturing system is the resolution on 3D-printed conductive elements, as this restrains trace width, via sizes, and the pad size that can be placed in any device. Fortunately, inkjet 3D printers offer high-resolution printing that is suitable for high-frequency antenna and sensor design. This technology ensures your design will be printed accurately and will rival products produced with traditional manufacturing processes.

As additive manufacturing technology matures and standards around various deposition processes are developed, IoT designers can expect greater flexibility and consistency from additive manufacturing systems. This will help simplify design for manufacturing of low-volume, high-complexity IoT devices.

If you’re interested in learning how to design an IoT device for 3D printing, the DragonFly Pro system is ideal for developing rapid prototypes of your next IoT device and even finished products. This system allows you to produce novel 3D-printed electronics for a variety of applications. If you’re interested in learning more about the DragonFly Pro system, read a case study or contact us today.

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