In through hole PCB assembly, the components are mounted on the PCB board that produced by FPC supplier， by inserting their leads/terminals in holes that are already drilled through the PCB board. These terminals are then soldered manually or through reflow soldering to hold the component in place and connect it to the conductive path. One key thing to note about Thru-hole assembly is that it is not very efficient for multi-layer PCBs as it takes up board space on every layer. As a result this type of assembly is usually found on single layer PCBs.

Advantages of Through-hole PCB Assembly:
• Highly Reliable: Components mounted on a PCB Board that produced by FPC supplier，using Through-hole assembly (THA) can withstand a high level of environmental stress as their terminals go through the drilled holes followed by soldering. This is the primary reason why Thru-Hole PCB boards are widely used in Military & Aerospace products as they tolerate extreme acceleration and collision scenarios.
• Manual adjustments can be performed easily: Defective components on PCB boards can be changed very easily. In other assembly processes like Surface Mount, it is not easy.

Limitation of Through-hole PCB Assembly:
Space Limitation: Through-hole mounting also reduces the available routing space in a multi-layer PCB since drilled holes go through all the layers and take more space in each layer of the board.