Mustaches and Automation in Flexible PCB Fabrication

Estimated reading time: 2 minutes

In any manufactured product, whether a house or a flexible circuit, there is always a raw material component in the overall cost. In the flexible circuit, flexible heater, and rigid-flex industry, sheet materials can account for 20–60% of the overall price. Admittedly, this is a very broad range, but factors, such as how common the materials are in the region where they are made, can cause this to swing one way or the other.

Your actions as an engineer or sourcing agent have an impact on overall cost, which I’ll illustrate through the example of building a house.

Materials such as plywood, OSB (oriented strand board), MDF (medium-density fiberboard), and drywall generally come in 4-foot-by-8-foot sheets. Dimensional lumber comes in 2-foot-long increments, so a 16-foot-long wall will have far less scrap than a 17-foot-long wall since 16 is divisible by 2, 4, and 8. The 17-foot wall will inherently require material to be trimmed off and scrapped. This is much the same in the flexible circuit industry: Manufacturers build their facilities around a few “standard” panel sizes and widths. Sizing your parts to optimize panel density will keep scrap to a minimum. Sometimes, you need that 17-foot wall; just be prepared to pay for it.

Why Standard Panel Sizes?
There have been many automation techniques developed over the past several decades in the circuit board manufacturing industry. In the late 1980s, raw materials were almost exclusively processed manually. An operator would cut panels from their original roll or sheet and manually place them in drill stackups consisting of drill entry and backer boards. They were then pinned individually to the bed of a single-spindle drill. Panels were manually racked and placed in hoist systems on a copper plating line.

Once plated, panels were manually coated with photoresist and printed on bed printers. A bed printer consists of a glass vacuum bed with a hinged mylar frame. Negatives were aligned to the panel and placed on the glass printing bed. The hinged frame was closed, and operators pulled a vacuum. The top surface was sprayed with glass cleaner. They then used a squeegee in a forward-and-back motion while applying as much downward force as they could muster. This was done to ensure a clean surface, as well as a tight mylar seal to the coated panel prior to imaging with high-intensity light. I’m certain that surgeons specializing in carpal tunnel procedures benefited from the archaic, repetitive nature of this process. A walk through the print room generally came with the observation that at least one person would be wearing a wrist brace or two as a form of industrial jewelry.

To read this entire article, which appeared in the June 2024 issue of PCB007 Magazine, click here.