The Heartbreak of Units Mismatch

A little extra checking may take a little extra time, but it can save a lot in the end. This sort of thing just bums me out. I’ve done it and similar things a few times myself. I’ve used a library for a connector with the same footprint, but smaller diameter pins than my chosen connector. That was a bummer too.

My best guess is that it’s a 0.1″ (2.54 mm) spaced footprint on the PCB and a 2.5 mm pitch part. It almost works. You might not even notice if it were a three or four pin part. At six, you’d certainly notice and at something from there on, the part simply will not fit.

In a prototype world, you may be able to get away with bending the pins a bit and forcing them a little way in, but maybe not. In a production electronics manufacturing environment, most certainly not.

Duane Benson
In the world according to Google, it’s only 72,000 beard-seconds off.

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About Mike

Mike Buetow is president of the Printed Circuit Engineering Association ( He previously was editor-in-chief of Circuits Assembly magazine, the leading publication for electronics manufacturing, and PCD&F, the leading publication for printed circuit design and fabrication. He spent 21 years as vice president and editorial director of UP Media Group, for which he oversaw all editorial and production aspects. He has more than 30 years' experience in the electronics industry, including six years at IPC, an electronics trade association, at which he was a technical projects manager and communications director. He has also held editorial positions at SMT Magazine, community newspapers and in book publishing. He is a graduate of the University of Illinois. Follow Mike on Twitter: @mikebuetow

3 thoughts on “The Heartbreak of Units Mismatch

  1. Until the US electronic and related technical industries weans themselves of the antique English system of units, e.g., mil, and enforces the use of S.I. units, an international system adopted by 99% of the world will we encounter this unnecessary problem. Some of NASA’s near failures were caused by this stupidity. As a person responsible for the accuracy of EIA standards in passive and display devices, I had to correct many standards that contained errors in calculation or in numerical equations of uncited provenance that were based on mixed units.

    It is about time that today’s technical industries drop this childish chauvinism toward S.I. units. One should note that this phobia extended to Henry Ford (adding to his other sins of bigotry, and antiunionism) adopting an inch system based on ten to avoid joining in the adoption of S.I.

  2. Itis well known fact that the PCB industry in general uses inch/ mils. While the IC industry has nono term
    for its reference unit.
    To avoid the connectors mismatch with the hole in the PCB, it has to be created in the CAD library in mm. And also the mother boards to created in mms.
    All other components and Daughter boards are created using inch/mils.

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