Design Units

There are 4 options (millimeter, micrometer, inch, mil) for units, but millimeter is the most popular today because most package dimensions in manufacturer datasheets are displayed in millimeter units.

Most PCB Library Parts are created in millimeter units to match the current package datasheet, but everyone is in a different environment. The new "Units" allows you to set the Minimum and Maximum rounding values.

By setting the Minimum and Maximum values, you establish the program rounding values.

Example 1: using 2 place Minimum accuracy, entering a 0.8 value, will display as 0.80. The program will automatically add a trailing zero to round the value 2 place minimal accuracy.

Example 2: using 2 place Maximum accuracy, all values will be rounded up to the nearest 0.01. Entering a 0.025 value would display as 0.03.

The program default settings are Minimum 2 and Maximum 3. Because the minimum is 2, the program will automatically remove all training zero’s past 2 places. And the maximum setting of 3 will only round up values less than one micrometer.

Example 3: using a 3 place Maximum accuracy, a value of 0.3255 will be rounded up to 0.326

Example 4: using a 2 place Minimum accuracy, a value of 0.29 will be rounded up to 0.30

The most important thing is that both the minimum and maximum options go up to 6 places. This accuracy is intended to increase the rounding accuracy when converting between Metric and Imperial units. It is not recommended that users select 6/6 as their min/max because this will affect the Physical Description that is auto generated by Footprint Expert in the FPX file. Having every value 6 places to the right of the decimal point would also affect every component family calculator, as every value will be rounded and displayed with 6-point accuracy. A simple value of 0.01 would display as 0.010000 and the Physical Description would be the same.