For mounting electronic components, two technologies are typically used. These include through-hole technology and surface-mount technology. While both technologies achieve the desired outcome, their processes and advantages are unique.
For this particular mounting method, leads are inserted into drilled holes on a bare printed circuit board (PCB). In addition to being referred to as thru-hole, this method is known as through-hole PCB. After being inserted, the leads are then soldered to pads located on the opposite side using an automated insertion mount machine or by manual assembly. Ultimately, the leads are present on both sides of a printed circuit board.
Since leads run through holes in a component, this technology produces strong components. Especially for high-reliability products that require strength between layers, it can withstand more environmental stress compared to the surface-mount technology. Through-hole is also more beneficial for certain applications, including prototyping and testing whereby replacements and adjustments are made by hand.
Initially, this technology was known as planar mounting. With this method, electronic circuits are produced by mounting leads onto the surface of a printed circuit board. Although surface-mount technology was first developed during the 1960s, it was not until the 1980s that it became extremely popular.
Surface-mount technology is used for manufacturing the majority of today’s electronic hardware. This technology is critical for not only the design of a modern-day printed circuit board but manufacturing, as well. Overall, the technology has enhanced both the performance and the quality of PCBs. Another benefit is the reduction of cost for handling and processing.
When comparing through-hole technology with surface-mount technology, the primary difference is how leads are mounted. As mentioned, with through-hole, the mounting involves leads going into drilled holes whereas with surface-mount, leads are mounted directly to the surface on both sides of a printed circuit board. Because a greater number of small components can be fitted onto a board using SMT, printed circuit boards are smaller, better performing, and denser.
Until the 1980s, through-hole technology was the go-to solution. However, with increasing demand for smaller size, enhanced utility, and better functionality specific to semiconductor packaging, things changed with surface-mount technology. While many experts felt that through-hole would eventually be phased out completely, that did not happen. Because of its many benefits, through-hole technology components are still popular, although this method is typically a secondary choice.