Introduction

Printed circuit boards (PCBs) are an essential component of most electronic devices. They provide the physical structure to mount and interconnect electronic components using conductive copper traces etched from copper sheets laminated onto a non-conductive substrate. Traditional PCB fabrication involves complex processes like photolithography to etch the copper layers. This requires extensive equipment, chemicals, and technical expertise, making PCB prototyping expensive and time-consuming.

Recent advances in additive manufacturing technologies like 3D printing have enabled low-cost direct printing of plastic PCB prototypes. Plastic printed circuit boards provide a simplified option to quickly iterate PCB designs during the prototyping phase of product development. This article will explore the benefits of 3D printed plastic PCBs and discuss the technologies enabling fast and affordable desktop PCB printing.

Benefits of 3D Printed Plastic Circuit Boards

Here are some of the major advantages of using 3D printed plastic circuit boards for prototyping:

Rapid Prototyping

The ability to quickly print circuit board prototypes on the desktop is a major advantage of plastic 3D printed PCBs. Designers can upload their PCB layout files and receive 3D printed boards overnight. This enables rapid design iterations without the lengthy fabrication times and costs of traditional PCB manufacturing. Small batches of prototype boards can be printed on-demand when needed.

Lower Costs

By eliminating the need for cleanroom facilities and expensive manufacturing equipment, plastic 3D printed circuit boards provide a low-cost option for PCB prototyping. Desktop 3D printers are relatively inexpensive in comparison to photolithographic PCB fabrication equipment. No harsh chemicals are required during the additive printing process.

Design Flexibility

The ease of modifying 3D CAD models enables greater experimentation with innovative board shapes and layouts. Plastic 3D printed circuit boards are not limited to rigid flat designs required by the PCB fabrication process. Printed boards can have complex 3D geometries that integrate connectors, enclosures, and other mechanical features.

Rapid Design Validation

With quick turnaround times, electrical and functional validation of circuit board designs is possible earlier in the development process. Design flaws can be identified and corrected earlier to avoid costly delays down the line. The ability to make rapid revisions saves overall product development time.

3D Printing Technologies for PCB Prototyping

Several 3D printing technologies can produce plastic printed circuit boards suitable for prototyping simple electronics. Here are some of the most common methods used:

Fused Deposition Modeling (FDM)

FDM 3D printers use a heated nozzle to melt and extrude thermoplastic filament material layer by layer to build up parts. Electrically conductive filaments like conductive polylactic acid (PLA) infused with carbon or copper particles are available for printing conductive traces.

FDM printing has some limitations around minimum trace resolution and consistency of conductive traces printed from conductive composite filaments. But the low cost and wide availability of FDM printers has made this a popular technology for printing simple circuit boards.

Stereolithography (SLA)

SLA uses an ultraviolet laser to selectively cure liquid photopolymer resin layer by layer. SLA 3D printers can achieve higher print resolution than FDM and more consistent results printing traces from conductive resin.

Conductive SLA resins contain metals or carbon fillers to achieve electrical conductivity when cured. Non-conductive resin is used to print the substrate and dielectric layers. SLA provides a higher degree of accuracy but involves higher printer and material costs.

Binder Jetting

In binder jetting, a liquid bonding agent is selectively deposited to bind metal powder particles spread in thin layers. Binder jetting uses pure metal powder, allowing high conductivity traces to be printed. Non-conductive areas are printed with ceramic powder.

Binder jetting can directly print multi-layer circuit boards in metal and ceramic materials without assembly. But the trace resolution is lower than SLA. Industrial binder jetting systems are expensive but new desktop options are emerging.

Aerosol Jet Printing

This method uses an aerosolized stream of conductive nanoparticle inks to print precision traces down to 10 microns. Non-conductive substrates are printed using conventional 3D printing before metallization. Aerosol jet allows printing very fine traces not possible with other methods but the equipment is complex and costly.

Others

Some other methods like micro-dispensing and inkjet printing are emerging for depositing conductive inks. Various metal plating processes can also be used to plate plastic 3D printed boards with copper. Each method provides different tradeoffs between cost, resolution, and performance.

Materials for 3D Printed PCBs

3D printable conductive materials are key enablers of direct PCB 3D printing. Here are some of the main types of materials used:

• Conductive Thermoplastics – FDM printing uses composite filaments like polylactic acid (PLA) or ABS blended with conductive fillers like carbon black, copper, and silver particles or nanotubes. Conductivity depends on filler concentration.
• Conductive Resins – Stereolithography uses photosensitive liquid resins containing conductive fillers that are cured into conductive traces using light.
• Conductive Inks – Nano-particle inks containing silver, copper, or carbon are used in aerosol, inkjet, and micro-dispensing printing. Sintering post-processing is sometimes needed.
• Metal Nanoparticle Filaments – Special FDM filaments use metal nanoparticles to achieve conductivity. Allows printing metal traces from desktop FDM printers.
• Metal & Ceramic Powders – Binder jet printing uses pure copper, aluminum, silver, or gold metal powders along with ceramic powder.

Materials research is advancing on 3D printable conductive composites to improve electrical and mechanical performance. The technology is still emerging but new materials will enable higher resolution traces, improved conductivity, and integration of more SMT components.

Design Considerations and Limitations

While 3D printed plastic PCBs provide an accessible prototyping capability, they have some limitations to consider:

• Lower Conductivity – Printed traces have higher electrical resistance than etched copper traces. This can limit power supply capabilities and high frequency performance.
• Lower Current Handling – Typical maximum current handling capacity around 1-2 Amps per printed conductive trace.
• Lower Trace Resolution – Typical minimum trace/space dimensions above 100 microns. Limits achievable board density vs traditional PCBs.
• Limited Component Mounting – Only SMT components are mountable on printed plastic boards. Not suitable for through-hole components or high pin count chips.
• Weak Mechanical Strength – Traces and layers bonded through 3D printing processes may delaminate under stress. Thermal management is also a consideration.

The capabilities are constantly improving with material advances and new printing methods. But designers should take these factors into account when designing 3D printed circuit boards for reliable prototyping.

Design Software Tools

To design 3D printed circuit boards, traditional PCB layout software can be used to plan circuit routings which are then integrated into a 3D CAD package. Here are some software options:

• KiCad – Open-source schematic capture and PCB layout tool with 3D viewer to export board models for printing.
• Eagle – Popular PCB design software with 3D modeling integration to export 3D board files.
• Altium – High-end PCB tool with built-in 3D PCB modeling capabilities to design boards for 3D printing.
• ** FreeCAD** – Open source 3D CAD package that can import 2D layouts to model 3D printed circuit boards.
• SolidWorks – Leading 3D CAD software that can import PCB designs to model enclosing electronics.

The design process involves creating the 2D circuit layout, modeling any 3D enclosure or mechanical features, and combining the two into a complete 3D printed board assembly ready for printing.

Applications

Some examples of where 3D printed plastic printed circuit boards are well suited:

• Education – Enables electronics and PCB design lessons without the need for board fabrication. Students can rapidly test working printed circuit projects.
• Rapid Concept Prototypes – Quickly test circuit operation, dimensions, and fit with enclosures during early stages of product development.
• Custom Enclosures – Integrate custom 3D printed enclosures, mounts, and interfaces with embedded PCBs.
• Low-volume Products – For niche products that don’t require mass production, printing small batches on-demand can be practical.
• Research – Conduct studies with custom circuit test boards tailored to specific experimental requirements.
• Repair and Maintenence – Print replacement boards for repairing electronics instead of sourcing originals.

In general, 3D printed boards are best suited to simpler, low-frequency analog and digital circuits that do not require high component density or performance. They are convenient for prototypes, custom devices, and university lab experiments.

Future Outlook

Advances in 3D printing technology, printable materials, and design tools will continue expanding the capabilities of directly printed plastic circuit boards. Here are some promising developments on the horizon:

• Higher resolution conductive traces from novel conductive composite materials or nanomaterial inks. This will enable higher complexity boards.
• Multi-material printing combining conductors, dielectrics, semiconductors, and encapsulants in one print process. This will eliminate post-processing steps.
• Hybrid printing with both printed plastic traces and mounted traditional PCBs or ICs. This will allow integrating complex ICs with 3D printed boards and enclosures.
• Development of design tools tailored to 3D printed electronics workflows. This will simplify designing for manufacturability constraints of printed boards.
• Metal platings methods to complement printed plastic traces with higher conductivity metal layers.
• Printing complete functional electronics including conductors, active components, antennas, sensors, and power sources.

While 3D printed circuit boards still have limitations, the technology is actively being used today for prototyping and custom devices. As capabilities expand, direct digital printing may become a practical manufacturing method even for mass-produced commercial electronic products.

Frequently Asked Questions

How are 3D printed circuit boards different from traditional PCBs?

3D printed circuit boards use additive processes to directly print conductive traces onto a non-conductive plastic substrate without photolithographic etching or plating. The printed traces typically have lower conductivity and different design rules than etched copper PCBs.

What kinds of electronics components can be used on 3D printed circuit boards?

Only surface-mount components can be reliably mounted on 3D printed plastic boards. The plastic material cannot support through-hole components or high pin count chips. Discrete passives, LEDs, simple ICs in QFN/QFP packages are common.

What materials are used for printing conductive traces?

Common materials are composite thermoplastics or photopolymers filled with conductive particles, metal nanoparticle inks, and metal particle filaments. Carbon, silver, and copper are typical fillers used to achieve conductivity.

How accurate can circuit traces be printed?

Accuracy depends on the printing process. Typical trace/space dimensions of 100-200 microns are common. Technologies like aerosol jet printing can achieve traces down to around 10 microns. Conductivity depends on print consistency.

Can 3D printed boards be made waterproof?

Additional conformal coatings can be applied to 3D printed circuit boards for environmental protection and insulation. The boards can also be potted into a sealed enclosure or overmolded using multi-material printers.

Conclusion

Additive manufacturing processes are opening up new low-cost prototyping capabilities for printed circuit boards. Designers now have the option to quickly 3D print plastic PCBs with conductive traces and mount simple components. While there are still process limitations, printed circuit boards enable rapid design iteration and customization ideal for prototyping.

3D printing technology will continue advancing to improve the materials, feature resolution, and performance possible with directly printed conductors and functional printed electronics. Combined with decreasing costs of desktop 3D printers, 3D printed circuit boards have the potential to transform electronics design workflows and enable new applications.