Years ago, I was remapping the functionality of an RC car for a school project. My team and I had to design, shop, build, test, and debug an analog circuit that added cruise control functionality and IR sensing. What became clear, despite prior experience reading datasheets and schematics, was how easy it was to overlook details. Details were often overlooked until the most inopportune moment. We used an H-bridge IC to control the direction of the motor, but mere days before our presentation, we had exhausted our supply of chips. As I had failed to account for the motor’s current draw during moments of high torque, we were sourcing current far in excess of what our H-bridge could handle.
Luckily, a local fabrication shop is not a group of students working in a garage. Still, designers should be confident that their production will go off without a hitch during periods of high time sensitivity. Quick turn PCB fabrication is a crucial period in time-to-market schedules that can make or break a product launch and impact the financial forecasts of a company. Adding a time constraint further complicates production with the massive amount of inputs and considerations already present in PCB design and manufacturing.
Preparations for Quick Turn PCB Fabrication
Quick turn fabrication may seem silly, but it’s a grouping of best practices that help reduce the time spent between different processes. Early design and fabrication teams must cooperate and coordinate to minimize manufacturing time.
Beginning with the design end — realize the limitations of manufacturing when hoping for quick turn results on a submitted job. Cutting-edge builds and complicated fab jobs will likely result in appreciable delays, an outcome antithetical to a rapid turnaround time. Whenever possible, designers should drive down the technical requirements of the board without sacrificing core functionality. Unfortunately, quick turns are suboptimal from a design and manufacturing perspective, as they prioritize market pressures over a longer development cycle.
That is not to say requiring or working with quick turnaround times is doomed to produce poor boards – all industries have to contend with some demands from end users. On the contrary, a strong design and manufacturing team will work to optimize the board’s performance within the time constraints. Below are a few steps that can assist with this process:
- Communication. When outsourcing a job for manufacturing, designers want to be clear on their partner shop’s capabilities and current operating capacity. PCB manufacturing must constantly flex for a shop to remain profitable and in business. Because of this, the earlier a design team can get in touch with the production floor, the more likely the latter can accommodate the needs of the former. Equally important are early discussions that establish what work the fabricator can and cannot perform, providing a frame for the design ruleset.
- Bill of materials. Chip shortages continue to impact procurements. Therefore, the best approach is to settle the BOM as early as possible, allowing for most of the listed parts to be sourced quickly. Furthermore, determining which parts and packages are available at the outset of the design makes compensating for the lack of parts easier. When caught early, minimal (if any) changes need to be made to placement/routing or potentially even the land patterns.
- Pre-design review. Time may be the foremost factor when considering quick turn fabrication, but cost-per-board also enters the calculus with larger lots. Alternate via structures, embedded components, and additional services have the possibility of increasing cost and reducing yield. Features that can be avoided without altering the board’s main purposes should be strongly considered when trying to hit production quotas on a deadline.
Why Box Builds and Other Post-Assembly Processes Matter to Quick Turn
For many PCBs, the design doesn’t end following the assembly. Rather, the enclosure of the board must also be taken into account; this is particularly common with multi-board designs that need to be physically integrated through off-board connectors. The best solution to prepare a board for this stage of development is to work with a shop that has both engineering and manufacturing capabilities to design and fabricate boxes, cable harnesses, and wire assemblies for long-term installations.
From an outside perspective, the significance of the box build may be overlooked. What may deceivingly look like a simple enclosure usually spends several hours through design and simulation to track the effects of heat transfer and dissipation, arguably the number one enemy to the long-term functionality and performance of the board. The box itself may function as part of the board’s heatsink, diverting heat generated from the board to the conductive, external surface area for improved radiation and convection to the surrounding environment.
Cabling is just as essential to board functionality because it acts as an extension of onboard connectivity. Where cables fail, typically arising from an undue strain that was not properly alleviated, board-to-board communication is interrupted. Often, reliability concerns are viewed only from the per-board manufacturing processes in Class 1, 2, or 3 boards. However, failure to account for the forces acting on these connectors can lead to service interruptions.
In either case, PCB quick turn fabrication must consider the engineering capabilities of a shop beyond the board itself. Otherwise, more delays arise from seeking a shop capable of the production ability and quantities required.
Your Contract Manufacturer Maximizes Production Time
Quick turn PCB fabrication involves collaboration between engineering, design, and manufacturing. All parties aim to minimize or eliminate any elements of a board’s design that could contribute to delays during production. When operating on a deadline, every preventable issue that can contribute to loss of time, yield, or quality must be assessed and prevented.
One of the advantages of working with a shop with extensive experience in quick turn fabrication is its ability to analyze and predict where delays could appear. They act as a secondary review process for any submitted design. VSE has the knowledge and experience to bring out the best in your designs. Our team of engineers is committed to building electronics for our customers, extending from initial review to fully-assembled build. Combined with our manufacturing partners, we can offer unparalleled service and expertise.
