Mixed Technology PCB Assembly

This article explains how to combine lead-free SMT and through-hole assembly on a single mixed-technology PCB. It covers process flow (lead-free reflow, wave, and selective soldering), design rules for pad and hole layout, thermal and fixturing considerations, and how to avoid common defects when SMT and THT share the same board. It is written for design and manufacturing teams building RoHS-compliant mixed assemblies.