Through Hole Assembly

1. Drilling Holes: The PCB is fabricated with holes at specific locations as defined by the PCB design. These holes are typically plated with copper to create electrical connections between layers.

2. Component Insertion: Electronic components with wire leads are manually or automatically inserted into the corresponding holes on the PCB. This can be done using automated insertion machines or by hand.

3. Bending Leads: If necessary, the leads are bent or formed to hold the components in place during soldering.

4. Soldering: The PCB is then passed through a wave soldering machine. This machine has a molten solder wave that makes contact with the exposed leads of the components, creating solder joints. The excess solder is removed, leaving clean connections.

5. Inspection: After soldering, the PCB is inspected for any soldering defects or issues with component placement. Automated optical inspection (AOI) and visual inspection are common methods.

6. Cleaning (Optional): If needed, the PCB may be cleaned to remove any flux residue left over from the soldering process.

7. Secondary Operations: Any secondary operations, such as trimming excess leads, may be performed.

Through-hole assembly is often used for components that require mechanical strength or high-reliability connections. It’s also suitable for components that generate a lot of heat, as the leads can act as heat sinks.

While surface mount technology (SMT) has largely replaced through-hole assembly for many applications due to its smaller size and cost-effectiveness, through-hole assembly is still used for specific components and applications where its strengths are preferred.