DIP (Dual In-line Package) through-hole assembly is a traditional PCBA manufacturing process that inserts component leads through drilled holes in PCBs, followed by soldering to create mechanical and electrical connections. This method is ideal for components requiring high mechanical stability, high power handling, or manual assembly, such as connectors, transformers, electrolytic capacitors, and high-voltage resistors. It is widely used in industrial control systems, power supplies, and audio equipment.

The DIP assembly process includes five key steps, with a focus on lead alignment and solder quality. First, PCB preparation involves drilling holes in the PCB with precise diameters (typically 0.1–0.5mm larger than component leads) to ensure easy insertion without excessive play. The holes are often plated with copper (electroless nickel immersion gold, ENIG) to improve conductivity and solderability.

Second, component insertion can be manual or automated. Manual insertion is common for small-batch production or large components (e.g., power transformers), where operators use tweezers to guide leads through PCB holes. Automated insertion machines (e.g., Universal Instruments GSM2) handle high-volume production, inserting components like DIP ICs, pin headers, and radial capacitors at speeds up to 1,500 parts per hour. For polarized components (e.g., diodes, electrolytic capacitors), orientation is critical—machines use vision systems to verify lead polarity before insertion.

Third, wave soldering is the primary soldering method for DIP assembly. The PCB is conveyed over a molten solder wave (typically Sn63Pb37 or lead-free Sn99.3Cu0.7 alloy) at 250–260°C. A flux sprayer first cleans the PCB surface and prevents oxidation, then the solder wave wets the exposed leads and PCB pads, forming strong solder joints. The wave height and conveyor speed are adjusted based on component density—higher waves are used for tall components, while slower speeds ensure full solder penetration for dense assemblies.

Fourth, lead trimming cuts excess component leads (typically to 1–2mm above the solder joint) using automated trimmers to prevent short circuits and improve mechanical stability.

Finally, inspection includes visual checks for solder defects (e.g., cold joints, voids, or insufficient wetting) and electrical testing (e.g., continuity testing) to verify connections. For critical applications (e.g., industrial controllers), in-circuit testing (ICT) is used to detect faulty components.

DIP assembly’s main advantages are high mechanical strength (leads are anchored through the PCB, resisting vibration and shock) and compatibility with high-power components. However, it requires larger PCB space (holes and lead protrusions increase size) and is slower than SMT for high-volume production. It is often combined with SMT (mixed-technology assembly) in modern PCBs, where SMDs handle signal processing and DIP components manage power or connectivity.