By The Metric Maven

Bulldog Edition

The Metric Maven has read countless articles about the decline of American electronics manufacturing. Pundit after Pundit who almost certainly have no idea which end of a soldering iron to pick-up, feign deep knowlege of what makes us “uncompetitive.” There is always a laundry list of problems which are trotted out by these professional opinion manufacturers. The one item which is never on their list, is the lack of the metric system in the US. This omission is proof by proxy they are armchair commentators who know a thousand ways to make love to a woman, but have never had a girlfriend.

Central to the miniaturization of electronics in the 21st century is the surface mount device (SMD). They are packed into smaller and smaller sized printed circuit boards. This makes “smart” phones, and other devices smaller, and much easier to lose–I mean use. The world standards groups met long ago and defined SMDs in terms of metric. Industry PCB consultant Tom Hasherr sees it this way:

The United States is now the only industrialized country in the world that does not use the metric system as its predominant system of measurement.

All the World Standard Groups involved in the electronics industry (IPC, IEC, NIST, JEDEC, EIA & JEITA) have made the transition to the metric measurement system. They formed an alliance to stop using English units and all the data they publish is in metric units.

Buried within these diplomatic statements is a larger story of America looking down, taking direct aim, and shooting itself in the foot—with inches.

The story goes like this: Once upon a time in the 1980s the world standards organizations banded together and produced worldwide metric standards. The Electronics Industries Alliance (EIA) in the US was given the responsibility to articulate the size of surface mount devices. The world had created all the standards in metric, and the EIA was to publish the new dimensions for all to use. A book was printed with all the component names, dimensions and other pertinent engineering data. It was then released to US manufacturers for implementation.

American component manufacturers refused to make components to metric dimensions. The PCB assembly and etching houses rejected metric dimensioned drawings, and spurned any thought of using them. They repeatedly demanded the EIA publish a version of the standard with Imperial (English) units. The EIA finally did this and unilaterally changed the names of the components.

The metric SMD components were now renamed using inches. Originally, the first two numbers of the chip component names are the SMD length in mm, and the second two are the width in mm. There is an assumed decimal point between each set of paired numbers. For example 3216 is 3.2 mm x 1.6 mm. Here is a short list of the renaming:

Now the 3216 is renamed 1206 which is 0.12″ x 0.06″ with an assumed decimal point at the front, and whatever conversion factor error is introduced. We can see that this US “improvement” introduced the same name designation for different sized electronic SMD components. After this re-naming, should you be interested in an 0402 or 0603 device, one now has the opportunity for a metric/imperial nomenclature mistake, which could precipitate lost time and money.

When the world standards committees discovered what the EIA had done, they released an order for the EIA to cease publication of this non-metric document. The EIA was reminded they were in violation of the international agreement they signed with all the world standards bodies agreeing NEVER to publish ANY standards using Imperial (English) units. In 1991 the EIA stopped publishing the feral document, and it is my understanding, that because of this, there is no longer any official standard followed in the US.

The US component manufacturers and PCB etching houses returned to the days of the perch, furlong, and barleycorn. With no standard to follow, SMD manufacturers began to game the situation. There were no longer standards for capacitors or inductors, or common three leg transistors known as SOT23. So 20 different sizes of these small outline transistors (SOT23) appeared. Chaos ensued. Rather than impose order by standards regulation, or metric adoption, the US industry just tried to figure out a way to name the multitude of these ad hoc non-interchangable “standard” parts.

The rest of the world embraced metric measurements and metric standard electronic parts. If you are in Germany and order parts from Japan, or Korea, or Timbuktu, you know they will fit on your printed circuit board. These are all metric countries. You have no guarantee if you order American electronic surface mount parts, that they will fit. If you were a German, would you take the chance?

The situation is actually far worse than I have explained thus far. In the United States our PCB software puts down grids in mils (a feral unit of the inch) or in inches. The world standard for parts is metric. The standard grid size for which these parts are designed is 0.05mm, so there is no reason to expect the metric parts to fit nicely on an inch based software grid. They are two different measurement units! The software used to connect up parts makes many mistakes in a mixed imperial/metric environment. We often have to fix these “by hand.” There is no guarantee of compliance to layout standards when metric and imperial are mixed. Metaphorically, we are trying to fit square pegs into a set of round holes. Metric parts on a metric grid are interconnected by software to international standards.

Over the last decade, I’ve watched as one small US based printed circuit board house after another have gone out of business. The company where I last had full-time employment, picked up and moved to China. How much of this PCB work might have remained in the US if we had embraced the metric system years ago? It’s hard to say, but it should be clear that metric conversion is of paramount importance—period. Unfortunately, the idea of industrial policy disappeared as a government concept in 1980, along with metric conversion, and has not been contemplated since.

When construction, medical, electronics and other industries are all taken together, one has to wonder just how much it has cost us not to have mandated the metric system in the United States. There were legislative efforts to make metric the official measurement system of the US in 1866, 1902, 1921, and 1975, and they were all either rejected by Congress, or were voluntary and therefore impotent. We may never know how much it has cost the country, because the US may never become metric.

The technically ignorant pundits who populate our media space, will continue to point to reasons that are divorced from any understanding of Engineering, technology, manufacturing, or the metric system as a problem with US manufacturing “competitiveness,” and the rest of the world will continue to reap the benefits of their choice to become metric—decades ago.

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Related essay:

The Cuprous Proxy