In a perfect world, a box and enclosure are designed, and then printed circuit boards or flexible circuits are designed to fit within that box perfectly, meeting all the electrical and mechanical requirements of the project. Sadly, most of us don’t get to work in that perfect world and at times must deal with challenges to that original plan. Things don’t always work as expected. Sometimes that is because something obvious was missed., Often it’s a small detail in the scope of a large project that can derail the schedule and all the previous planning.
I want to share an example of one of those times and share how the project was brought back on schedule by exemplary communication between the PCB designer, fabricator, and assembler. First, a little background. This example was a high visibility design at a prominent OEM. The box and enclosures were designed along with a series of rigid and rigid flex PCBs. With only a few days before the final deadline, the “challenge” presented itself. There were nodes running out to a test connector that were missed. Problem solving began, and with a monetarily driven, critical deadline looming, swift action was taken.
Knowing this was going to take communication well beyond normal discussions, the PCB designer was flown in, caliper and computer in hand, to help solve the problem. The challenge was that there was very little space in the unit, and not enough room to run a wire harness. After brainstorming with the team, the decision was made to proceed with a series of flexible circuits. Out came the caliper and an outline, and a bend and fold configuration was created that would make the connections to the test connector. This very experienced designer followed the adage, measure twice, cut once, and while on-site, they cut out mylar mock-ups of these flexible circuits, clearly marked ‘top’ and ‘bottom’, and notched the flex mockup to be sure that there would be no confusion. Interestingly enough, the mylar mock-ups were cut out of some old x-ray films that one of the engineers happened to have in his desk. I am sure they were being saved for just that day.
Before going further, I should mention that this was the Thursday just before a holiday weekend with the goal of having assembled flexible circuits delivered within one week only exasperating the issue. Once back in the office the PCB designer went to work creating these flexible circuit designs. Knowing there would be just one opportunity to get this right, the designer brought both fabrication and assembly into the discussion as soon as possible. Materials were discussed, ensuring that the flexible materials would be available for quick-turn fabrication. Engineering time at the PCB fabricator was being held to expedite the tooling process, and components were ordered to be delivered overnight. Everyone was on board to get this project completed and meet the aggressive deadline.
Again, drawing on past experience, the designer used many little tricks to be sure this design was correct the first time. The pin-out was verified, and the flex was notched to ensure the connector orientation was more than clear—in fact all four corners of the flex were also labeled to be sure there would be no confusion. The outline was printed and overlaid with the mylar mock-up to be sure everything was in alignment and that bends and folds were not creating any confusion. (Bending and folding a flex can create confusion when determining connector orientation.)
These designs were all completed over the holiday weekend and sent off to the eagerly awaiting PCB fabricator to get started bright and early on Tuesday morning. The PCB fabricator had materials ready and proceeded to build the flexible circuits with a 24-hour turn around. This is exceptional in flex fabrication and required clear lines of communication form start to finish. They were prepared for the order and spoke several times to the flex designer throughout that build.
Next, the flex needed to be assembled—again on a tight 24-hour deadline. Strong communication was again required. The assembler was prepared for the order to arrive, the connectors had been ordered and were in queue, and the assembler successfully completed the requirement the same day the flex were received.
There was no time for the flex to be sent to the designer for final review, so they were drop-shipped to the end customer for installation. The flexes were dropped in and worked perfectly. Success! Essentially, this was completed start to finish in one week over a holiday weekend, allowing the OEM to meet their deadline, which had a large monetary milestone attached. Missing that deadline was not an option.
So why do I share this story? I wanted to share this as a perfect example of what can be accomplished with clear, thoughtful communication. This required all contributors in this effort to be in lockstep from the beginning. Multiple flex designs being completed, fabricated and assembled in 7 days was an aggressive goal and accomplished by both clear lines of communication from the start and the knowledge of what is important to each contributor. This success should be celebrated and used as an example for others facing these same kinds of challenges. Let’s learn from each other’s experiences.
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