Arduino Pro Micro (based on the ATmega32U4) is a popular choice for compact PCB designs. Because it is a SparkFun-designed board, the most "canonical" Eagle library is the official SparkFun Eagle Libraries
Ensure the mounting holes (1.2mm in standard libraries) are included to secure the module. 5. Essential Design Considerations (Pro Micro) arduino+pro+micro+eagle+library
All official SparkFun boards are open-source. This means you have full access to the original design files. Arduino Pro Micro (based on the ATmega32U4) is
While tempting, avoid random .lbr files uploaded to unmoderated forums. Many contain footprint errors from the original 2014 Eagle versions (wrong drill hole sizes for the reset button or misaligned USB port). Many contain footprint errors from the original 2014
Before designing, it is important to note the physical "solid features" of the board that the library footprint must match: