When is an 0201 Not an 0201?

Metric vs US resistor packageI'm working on a special project here that involves some 0402 LEDs and 0201 resistors. When doing such a thing, you should always check the footprint you're using against the data sheet. When using extra small parts, like this, I recommend making a custom footprint unless the one you picked is exact, and I mean exact. There just isn't an margin for error at these geometries.

Take a look at the table on the right. The dimensions are in mm. Spot anything a bit off? Counter to most data sheets, the sizes listed in the "Type" column are metric sizes. At DigiKey, the package was listed as "0201 (0603 Metric)." I see that all the time, but for some reason, most data sheets Metric vs US resistor package Conversionshow the package name in US size while listing the dimensions in metric.

The first table was at the front of this data sheet (page 5). The second table was on page 35 - the opposite end of the data sheet.

We do occasionally get boards with metric size pads for a US size part, or vice verse. Sometimes we can make it fit, but not always. Bottom line, is to check and double check. I caught this one because the dimension .54 mm is about 21 mils, which is too small for an 0402. That, and the fact that the table doesn't list an 0201 size.

Duane Benson
Is it Bigfoot or Sasquatch?

 

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