The Complementary Role of PCB Design and 3D Printing in the Prototype Development Process
3D printing is revolutionizing the prototype development process. By fundamentally changing the mechanisms for creating and fabricating the accessory systems critical to a design project’s success, 3D technology helps design engineers turn their ideas into finished products quickly.
These accessory systems, often referred to as jigs or testers, can be used to program a device or test the functionality of a circuit, making them as critical to a project’s success as the PCB designs themselves.
This paper will examine how PCB design and 3D printing can be utilized together to improve the process of taking an idea through prototyping and into production. Our use case will be the production of a basic Bluetooth® smartwatch.
Proving the Initial Design Concept
Rather than start from scratch, our project team chose an open source watch design 1
using commercial-off-the-shelf (COTS) subsystem components that included:
- Organic light emitting diode (OLED)
- Bluetooth transceiver subsystem demo board
- Arduino processor per-assembled to a breakout board
Once the requisite COTS components arrived, the team started breadboarding the components. At this stage, the priority was testing functionality.
Though it is common for a design team to custom-build a breakout board using simple designs on FR4, we focused on getting the assembly to work as needed. The result wasn’t pretty, but it worked. Once we successfully powered up and programmed the proof-of-concept prototype, it was time to optimize the design for the smartwatch.
Always Be Optimizing
The design team now had to compress all of the functionality onto a single board that would fit inside a suitable watch enclosure. This is where 3D printing technology really helped the PCB design team. Mechanical designers required physical parameters of the board in order to design the watch, but without guidance from the mechanical team on what the outline restrictions might be, it’s difficult to finalize a PCB design. 3D printing could, for example, illustrate where holes in the circuit board should be drilled for mounting to standoffs.
By removing the guesswork for both mechanical and PCB designers, 3D printing helped accelerate the iteration and refinement of the mechanical design process without requiring changes to the board. Quick turn times on the fabrication of prototype enclosures facilitated integration of board and box, making the process much more interactive.
Integrating Mechanical and PCB Designs
While the mechanical team worked on its requirements, PCB design engineers finalized the bill of materials (BOM) for the new single-board version. The two different sets of schematics were then carefully merged into a single design.
Laying Out The Board
With the BOM established, the physical layout team got started. With each step of the workflow, we look for ways to further optimize both our process and PCB function.
Design footprints for components must align connection points perfectly with the parts to be used. Our layout team started with the BOM, auditing parts libraries to verify all landing footprints. Missing footprints were sourced or created from scratch.
Initial Footprint Placement
The layout team then placed components on the board in the most logical and effective way, minimizing the distance and complexity of traces required to correctly connect all the components. This process can take up to half of the time spent on layout. It requires thinking in three dimensions to ensure that components are not too tall or bulky for the space constraints of the enclosure.
Confident that the component placement would work inside the enclosure and that all design considerations were accurate, our layout team got to work finalizing the trace routes in the layout.
Circuit Layout, Verification, and Preparation for Manufacture
With layout under way, the mechanicals team began designing the necessary jigs, fixtures, cradles, and programming fixtures for the board being designed. By 3Dprinting these items, the team was primed to achieve “first light” from their prototype as soon as the boards arrived back from fabrication.
When the layout was completed, the layout team confirmed that all components were connected correctly and made sure that layout matched the original schematic. Now it was time to fabricate the first circuit boards for assembly.