Sep 10, 2019

The Top 4 Design for Additive Manufacturing Guidelines for Electronics Engineers

pcb designThe additive manufacturing space is in the throes of continuous innovation and is producing real gains in a variety of industries. In the electronics industry, PCB designers need to tailor their products to specific 3D printing systems and materials with the right design for additive manufacturing guidelines. These guidelines are about more than signal or power integrity—they are specifically tailored to ensure additively manufactured electronic products meet important quality and manufacturability standards.

3D model for a computer motherboard.

This motherboard will carry specific design for additive manufacturing guidelines.

4 Design for Additive Manufacturing Guidelines

The standard electrical design rules for any circuit board are meant to help ensure signal integrity and power integrity throughout your PCB. These should also be followed when designing a PCB for additive manufacturing. However, some design aspects are more specialized due to the unique nature of 3D printing for electronics.

1. Stay Within the Printing Region

The print head in any 3D printer will only be able to move within a specific area. This means the board shape needs to fit within the available printing space. Because the available printing space is three dimensional, there is a maximum thickness that can be printed with any 3D printer. When combined with your printer’s resolution, this will determine the maximum number of layers you can include in a multilayer PCB. If you are planning to produce multiple boards in parallel, the size of the printing region will also limit your throughput.

2. Design to Your Printer’s Resolution

Any 3D printing system will have a resolution limit that defines the smallest feature size that can be deposited. This applies to any 3D printing process. In PCBs, this limits the trace and via width that can be reliably printed. It also limits the layer and ground/power plane thickness to some minimum value. If your printer has higher resolution (that is, it can print smaller features), you can pack more interconnects, vias, and layers into a single board.

3. Balance Functionality and Standards

The standards landscape for additively manufactured electronics is still evolving, but many of the standards (such as ISO 8887-1 and IPC-CFX) revolve around file exchange formats and connectivity among manufacturing assets. 

The ISO/ASTM 52900:2015 and ISO/ASTM 52921:2013 standards provide definitions, and quality and testing requirements for additively manufactured products in general, but these are not specific to electronic devices. Electrical functionality, as defined by various standards organizations, will still focus on ensuring power integrity, signal integrity, manufacturing yield and quality, and other aspects that depend on the signaling standard used in a given product.

Because the interconnect and board geometry of any 3D-printed PCB is highly customizable, following design for additive manufacturing guidelines requires incorporating signal and power integrity simulations into your design workflow. From a signal integrity perspective, you will need to carefully balance your conductor and board geometry against your trace geometry and impedance requirements to ensure signals do not become corrupted as they propagate throughout your board. This requires working with a simulation program that directly considers your layout and board geometry when designing interconnects.

4. Design for Minimal Mechanical Supports

While this requirement is critical for 3D-printed mechanical products with unique shapes, it also applies to boards with odd geometry. A board that contains an upward-sloping angle may require some support during printing to prevent the board from tipping during printing. If you are designing with a board that includes an odd angle or bend, you may need to deposit a mechanical support as the board is printed.

If you’re using a 3D printer that co-deposits your PCB substrate and conductors, you can over-deposit the substrate below your bend and remove the excess substrate material once fabrication is completed. This creates some material waste, but it leads to a higher quality product. Alternatively, you may need to simply reduce the extent of the bend or change the board’s orientation to prevent the product from tipping during printing.

Despite the unique nature of these design for additive manufacturing guidelines, PCB designers have much greater design freedom because they are not inhibited by traditional subtractive PCB manufacturing processes. This allows designers to create interconnect architecture with any geometry, print conductive components directly on a substrate, create cavities for easily embedding components in a substrate, and implement a non-orthogonal layer and via architecture. The substrate itself can also be tailored to have any geometry.

Adapting Designs to 3D Printing Systems: The Role of CAD Software

Most 3D printing systems must interface with a 3D CAD model to generate printing instructions. SOLIDWORKS for example, is a massively popular program for designing 3D mechanical models that can be used with a variety of 3D printers and processes. You can convert your design to printing instructions by exporting an .STL file of your model.

When it comes to PCB designs, mechanical design software does not include the features required to properly design and assess the electrical functionality of a new electronic device. Most EDA software has not advanced to the point where it can generate 3D printing instructions for different systems directly from a PCB layout. This is ironic, given the fact that many EDA packages can build a 3D model for a PCB, allowing designers to check component and connector clearances against their design standards. Part of this problem originates from a lack of collaboration between EDA and MCAD software companies.

3D model of a PCB with multiple ICs.

This is one of many 3D models that can be created in your EDA software.

However, the most advanced PCB design software packages can interface with the native MCAD tools in SOLIDWORKS or other mechanical design programs. This allows electrical and mechanical designers to design a PCB and its mechanical enclosure simultaneously. With the right add-in for your mechanical modeling program, you can finally take a PCB design directly from your EDA software and generate .STL files for a 3D printer in your MCAD software.

This type of collaboration is important from several perspectives. First, mechanical and electrical designers can no longer remain siloed from each other and need to work together. This collaboration, in person and in their design packages, helps hasten time to market as new products become more electrically and mechanically advanced. This also allows electrical designers to carefully design their boards with unique non-planar geometries, which is simply not possible with conventional EDA software.

With the right design software and printing system, you can follow design for additive manufacturing guidelines and ensure that your design intent is accurately reflected in your finished product. The DragonFly LDM additive manufacturing system from Nano Dimension is ideal for low-volume manufacturing of complex electronic devices with planar or non-planar architecture. 

The DragonFly LDM’s SOLIDWORKS add-in easily interfaces with advanced PCB design programs, allowing you to quickly adapt your designs for 3D printing. The system also offers design freedom, including the ability to design traces at an incline, print side-mounted components, battery sockets, and printed capacitors, and vertically integrate interconnects. Read a case study or contact us today if you’re interested in learning more about the DragonFly LDM system.

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