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80 SMT007 MAGAZINE I JUNE 2021 plate assembly and a board stiffener. Dowel pins are used to align a PCBA, board stiffener, and pogo pin socket plate. e sub- assembly shown is part of a clam shell test fixture used to test a panelized set of PCBAs (commonly referred to as a DUT panel). is alignment is critical because the pogo pins that are inserted in the sockets interface with the panel PCBA for parametric and functional test of the individual devices under test (DUTs). Precise targeting of the pogo pins in the test fixture to test points on the DUTs is critical for repeatable error-free high-volume throughput. Tooling holes are not only round holes in the PCB; they can take on many different shapes to aid in the higher-level assembly process. I have seen slotted tooling holes used to keep a PCBA locked in a single dimension so that two high insertion force connectors can be mated prop- erly. Triangle, hexagon, and semi-circle shaped tooling holes have been used as keying mech- Tooling holes are more than a type of mount- ing hole used in PCBs to aid in the assembly of printed circuit board assemblies (PCBAs). Tooling holes are used for aligning, inserting, and extracting PCBAs in higher level assem- blies because they are precise mechanical ref- erences embedded into the PCB. e differ- ences between mounting holes and tooling holes are subtle but important, nonetheless. Tooling holes deserve their own designation within the PCB design environment. As precise mechanical references, tooling holes are used in a wide range of higher-level assembly processes. When matched appro- priately with dowel pins, tooling holes can be used for precision alignment of PCBAs in elec- tromechanical assemblies. A dowel pin is typ- ically a cylindrical metal rod that has a cham- fered end. However, they do come in many shapes and sizes. Figure 1 shows an example of how a PCBA can be aligned with a pogo pin It's Pronounced 'Tooling Hole' Adventures in Engineering by Chris Young, YOUNG ENGINEERING SERVICES LLC, AND THE GOEBEL COMPANY Figure 1: Example of a tooling hole.

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