Differences Between SMT and Through-Hole PCB Assembly Methods January 21, 2017

With the growing popularity of surface-mount technology (SMT) on printed circuit boards (PCBs), it has replaced through-hole mounting over the past decades. This article outlines both PCB assembly methods, why SMT is preferable than through-hole, and if through-hole can still be relevant in some applications. You will have a thorough understanding of the distinct qualities of these methods and their key differences.

Through-Hole Technology

PCB AssemblyThrough-hole technology was used for many years in the assembly of almost all PCBs. This mounting method uses leads on electrical parts, which are inserted into holes drilled on the PCB, and then soldered onto pads located on the opposite side. This method is reliable since it provides solid mechanical bonds, but the additional drilling makes the PCBs a lot more expensive. Moreover, the existence of holes in the board creates restrictions when it comes to available transmission area for signal traces on different layers, which are just below the uppermost layer on multi-layer PCB. These are only two of the reasons that SMT became a widely popular method of PCB assembly during the 1980s.

Surface-Mount Technology

Instead of drilling holes, SMT allows electrical parts to be directly placed or mounted into the surface of the board. In general, SMT parts are smaller than through-hole parts because SMT use no leads or only smaller leads. Since the PCBs of surface-mount devices do not need many holes drilled, and the parts are more compact, it possible for smaller boards to have higher circuit densities. This is particularly important because today’s electronic devices are becoming more compact and more complex. Furthermore, SMT is generally less expensive PCB assembly method that through-hole technology.

Main Differences

While there are a lot of distinctions between SMT and through-hole mounting, there are some key differences such as:

•SMT address space issues that commonly affect through-hole technology.

•SMT parts are directly mounted to the board and do not necessarily require leads, while through-hole parts require leads that go through drilled holes.

•The packing density attained through SMT is significantly higher than in through-hole technology because SMT parts are more compact.

•In SMT, the pin count is higher as compared to through-hole mounting.

•SMT parts are less expensive.

•SMT allows itself for PCB assembly automation, which makes it much more suitable for lower costs, high capacity production than through-hole technology production.

•Because of the reduced size of SMT, it makes it easier to have higher circuit speeds.

•Although SMT production costs are generally cheaper, there is higher capital needed for investing in equipment and machinery.

•SMT demands for design, skills, technology, and production are more advanced than through-hole mounting.

•In terms of handling huge and bulky parts, parts that are often put through mechanical stress or for high-voltage, and high-power parts, through-hole mounting is generally more preferred.

PCB Assembly

While there are cases wherein through-hole technology could still be used in modern PCB, in general, SMT is superior.

Choosing a Manufacturer That Offers Surface Mount Technology

Because of the high costs involved in purchasing SMT equipment and machinery, a lot of smaller electronics companies are having difficulty taking advantage of this PCB mounting technology. For such cases, it is in the best interest of these companies to look for a contract manufacturer that can offer these kinds of services. This would allow them to use SMT into the design and production of their boards without being forced to buy or maintain costly machinery. For contracting PCB assembly, make sure to choose a reputable PCB manufacturer that stays up to date with the best and latest technological advancements, and knows all of the best techniques for manufacturing complex electronics devices.

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