I am designing a SMD PCB which includes ATMEGA2560AU OF sparkfun-Digital IC library with the package value of TQFP100 . When i run a DRC check using the sparkfun .dru file it shows clearance error between the SMD IC pads. Why does it show this error ?
Because the pads are too close together according to the settings in the DRU file. According to Sparkfun, the TQFP 's pads are less than 6mil apart. I do know that most board houses will manufacture the board even though this is just below spec. You may also want to research the design specs at your chosen board house.