From fused deposition to inkjet printing and aerosol deposition, the list of processes for additive manufacturing is already long and can be expected to grow in the future. The various 3D printing processes have their advantages in different applications, and choosing the right process and system is important if you are considering complementing or replacing your current capabilities with additive manufacturing.
If you are familiar with desktop-scale printers, then you may already have an idea of how this technology is adapted to 3D printing. Typical home user systems typically fall into two camps. They either extrude a molten polymer by way of FDM (fused deposition modeling) or selectively polymerize a resin in a vat in an SLA (stereolithography apparatus). Many more enterprise-scale options exist however. Such processes are often more complex, and may require a sheath gas to prevent unwanted chemical reactions during deposition, for example. Particularly when 3D printing metals or ceramics the deposited materials must then be sintered, baked, or cured in some way prior to final assembly of a finished product.
Here’s a closer look at another of the deposition options, inkjet deposition. 3D inkjet printer advantages and disadvantages are important to understand as you consider this additive manufacturing technology. Here, the focus is on this digital manufacturing technology primarily as applied to 3D printing circuitry.
3D printing a unique substrate.
Weighing 3D Inkjet Printer Advantages and Disadvantages
When it comes to choosing a 3D printing process for PCBs, there are some important aspects to consider when selecting an additive manufacturing process and system:
- Resolution: This defines the accuracy of printed insulators and conductors, and becomes very important for designers who want to create PCBs with a unique interconnect architecture or high-density conductor.
- Surface finish: With DC circuits, surface finish is a negligible performance factor. However, with analog circuits operating at RF frequencies, very high-speed circuits, and antennas, rough conductors can lead to issues like frequency mixing at high intensity, signal reflections at rough spots along the surface, and difficulty with impedance control routing throughout a PCB.
- Throughput: This defines the productivity of the process and is really related to the speed with which materials can be deposited. Using a multimaterial inkjet approach reduces the number of manufacturing steps to one printing step. In contrast, traditional PCB manufacturing approaches require many intermediate assembly steps during fabrication.
- Range of useful materials: Not all processes are useful for every material, which also affects the throughput. Some processes require breaking printing into multiple steps, and some processes are simply not useful with all materials.
Choosing the right additive manufacturing process requires finding the right balance among these areas. Like any manufacturing process, inkjet printing is not universally adaptable to any product, and fabricated parts may not have the required strength for use in some very demanding mechanical applications.
However, inkjet printing is an attractive process for electronics for a number of reasons. Regarding 3D printing of PCBs, the multimaterial end-product (conductive and insulating materials) is readily printed by means of multiple printheads, the range of required materials is relatively limited, while the resolution and surface finish requirements are stringent. Inkjet printing can satisfy these requirements for a broad range of electronics applications.
Some Advantages of Inkjet 3D Printing for Electronics
Simultaneous Printing with Multiple Materials
Inkjet printing is very different to fused deposition modeling and aerosol deposition. Inkjet printing deposits ink over an area and not at one given nozzle location. Inkjet printheads can have hundreds and even thousands of minute nozzles per printhead, each one is precisely and individually controlled.. The ability to use multiple printheads in the same inkjet system allows multiple materials to be deposited contemporaneously. The ability to print an insulating substrate alongside conductors makes inkjet printing ideal for additive manufacturing of PCBs.
High Resolution and Smooth Surface Finish
The resolution of 3D inkjet printing is sufficiently high, thus the surface finish of printed conductors and substrates is smooth enough that subsequent finishing steps are not required. The roughness of 3D-printed conductors in PCBs is fine enough that it competes with traditional PCB manufacturing processes. The resolution with 3D inkjet printing is also high enough to allow printing of microstrip and stripline traces that match those in traditionally manufactured PCBs.
Printing Over a Large Area
Deposition during inkjet printing does not need to be confined to a specific area. The layer-by-layer deposition process allows materials to be printed over a large area. When combined with deposition of conductive and insulating materials, inkjet printing becomes an ideal process for 3D printing of PCBs.
Some Disadvantages of 3D Inkjet Printing for Electronics
Limited Material Selection
Although conductive and insulating materials can be 3D printed with an inkjet process, inkjet systems are generally adapted to specific materials that can be deposited at low viscosities. The deposition and subsequent curing and sintering processes limit the range of materials with 3D inkjet printing. The conductive and insulating materials absolutely must have the right viscosity upon extrusion through the printhead.
One option to overcome this drawback is to use conductive materials that can be sintered with an infrared lamp. Conductive nanoparticle inks are a natural choice as they can be quickly sintered using an infrared lamp directly in a 3D inkjet printer. This eliminates the need to use a high-temperature oven for sintering after deposition. A polymer substrate that can be cured with a UV lamp allows for simultaneous sintering and curing of a 3D-printed PCB during deposition.
Low Part Strength Compared to Bulk Materials
Parts that are 3D printed with an inkjet tend to have lower mechanical strength and fracture easier than a traditional board with the same geometry.
SEM image of silver nanoparticles used in conductive inks.
Given the growth in 3D printing across nearly all manufacturing sectors, it is only a matter of time before the range of useful conductive and insulating materials expands to overcome this disadvantage. As the range of available materials expands in the future, one can expect that sinterable composite conductors with higher mechanical strength will become usable with 3D inkjet printing systems.
Inkjet printing proceeds in a layer-by-layer manner, where the material leaves the printhead as a liquid. When printed onto a curved substrate, the material can run and flow away from the printing region, thus the 3D printed product will not match the design intent. This means that each layer must be printed on a flat substrate.
Despite the flat substrate requirements, the final product can still be printed with a non-planar geometry thanks to the layer-by-layer deposition procedure. Each layer can be slightly offset from the previous layer, allowing printing of unique non-planar substrates and conductors on a PCB.
When it comes to 3D printing for PCBs, the advantages of inkjet printing significantly outweigh the disadvantages. There are many proven strategies for overcoming the disadvantages of inkjet printing for PCBs. Using the right additive manufacturing system can help you easily surmount the challenges of inkjet printing for PCBs.
Although there are advantages and disadvantages for many products, inkjet printing is particularly useful for additive manufacturing of 3D-printed electronics with unique interconnect architecture and non-planar geometry. The award-winning DragonFly Pro additive manufacturing system is built specifically for rapid prototyping of new electronics for a variety of applications. Read a case study or contact us today to learn more about DragonFly Pro.