IPC International Community magazine an association member publication
Issue link: https://iconnect007.uberflip.com/i/1542698
JANUARY 2026 I I-CONNECT007 MAGAZINE 117 suit) since the shear operator had to determine the optimal shear strategy to maximize the number of panels per sheet, and the amount of backup and entry required based on the planned drilling stack height. This backup was used on both sides. I must have done a good job, because my next position was fabrication, where I quickly became the supervisor. We had no CNC equipment, and orders were fulfilled in various ways. With a large enough tolerance, some orders were "shear to size," using corner marks imaged on each board in a panel. All other boards were first sheared outside the corner marks (oversized). Most of our PCBs were square, which were routed to size by pinning two to three of the sheared boards onto a one-quarter- inch-thick phenolic template and manually running them through a bar router. It was basically a small table saw with a diamond blade. The template was machined and tooled on a manual milling machine. For irregularly shaped boards, we used a pin router, which used the same type of template but cut on a bottom-mounted tabletop woodworking router with a diamond mill bit. The tolerance of the finished PCBs was determined by the accuracy of the template, the stack height, and the routing speed of the operator. We also had a punch press for single-sided boards, a bevel machine for gold tabs, and a manual slitting machine used to put slots into the gold tabs, or the exterior of the boards. PCB design was very primitive: customer supplied artwork was simply black crepe tape on a transpar- ent sheet to define the circuitry at a 2–4X scale. If the design required circuits on both sides of the board, one side was designed with red cellophane tape, and the other side was designed with blue cello- phane tape. Filters on a camera the size of today's drill machines would separate the sides when they were preparing the phototooling to manufacture the PCBs. Drilling was also manual to semi-automatic. In addition to the single-station bottom drills used, we used a "Quad-Drill," which had four spindles manu- ally controlled by an operator following a "road- map" path in a manually bottom-drilled template. The operator would lower a stylus into a template hole and pull a trigger to initiate the drilling of a single hole in the four stacks of panels. Manual plating meant operators had to move the racks of panels by sheer might. We were not aided by overhead hoists until we moved into our third custom-built PCB facility. Screening was the PCB equivalent of printing T-shirts, making polyes- ter or steel screens and hand pushing solder mask and silkscreen ink onto panels. With no automation involved, these processes were much more art than science. The Excellon Revolution When we purchased our first Excellon Mark IV Driller/Router and Opic Programmer, our plant man- ager tapped me to lead this "revolution" as the first CNC programmer. This required creating a color- coded roadmap on the component side of a mylar film. The programmer assigned a color to each drill size, and manually mapped the path to all the holes for each drill size using the print as a guide. Then the mylar was placed on the Opic glass table, elec- tronically squaring the artwork with targets and set- ting the zero datum. Each tool number and size was coded into the system, and the programmer fol- lowed the roadmap that was magnified and pro- A modern hydraulic shear, much safer and easier to operate! Image source: Wikimedia Commons Excellon Mark IV Driller/router with NC controller. Image source: Bridgtronic. T H E R I G H T A PPROAC H