Over the past several decades, surface mounted technology (SMT) has grown in popularity and
has widely replaced through-hole technology. But why is SMT so preferable to through-hole mounting, and can through-hole still be relevant in certain applications? By taking a few moment's to learn about both methods, you'll gain a thorough understanding of the unique characteristics of the two, the key differences between them, and what it is that makes SMT the preferred option.
Through-Hole Technology
For years, through-hole technology was utilized in the construction of nearly all printed circuit boards (PCBs). This particular mounting scheme involves the use of leads on electrical components, which are then inserted into holes that were drilled on the PCB and soldered to pads situated on the opposite side. Through-hole mounting is extremely reliable, as it provides strong mechanical bonds, however, the additional drilling makes the production of boards significantly more expensive. Additionally, the presence of holes in the PCB create limitations in terms of the available routing area for signal traces on the layers which are immediately beneath the top layer on multi-layer boards. These issues are just two of the many reasons that surface mounted technology became so popular in the 1980s.
Surface Mounted Technology
In lieu of drilling holes, SMT enables electrical components to be mounted, or directly placed, onto the surface of a PCB. Generally speaking, SMT components are smaller than their through-hole counterparts. This is due to the fact that SMT components either have smaller leads, or no leads at all. Because the PCB of a surface-mount devices (SMDs) does not require as many drilled holes, and the components are more compact, higher circuit densities are possible on smaller boards. This is especially important, as today's electronics are growing more complex and more compact. Additionally, surface mounted technology is typically less expensive than through-hole mounting.
Major Differences
Although there are many differences between through-hole and surface mounted technology, there are some key distinctions such as:
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SMT resolves the space problems that are common to through-hole mounting.
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In SMT, components do not have leeds and are directly mounted to the PCB, whereas through-hole components require lead wires that pass through drilled holes.
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The pin count is higher in SMT than in through-hole technology.
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Because components are more compact, the packing density achieved through SMT is much higher than in through-hole mounting.
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SMT components are typically less expensive than their through-hole counterparts.
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SMT lends itself to assembly automation, making it far more suitable for high volume production at lower costs than through-hole production.
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Although SMT is typically cheaper on the production side, the capital required for investing in machinery is higher than for through-hole technology. -
SMT makes it easier to acquire higher circuit speeds because of its reduced size.
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The design, production, skill, and technology that SMT demands is quite advanced as compared to through-hole technology.
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Through-hole mounting is typically more desirable than SMT in terms of large, bulky components, components that are subject to frequent mechanical stress, or for high-power and high-voltage parts.
Although there are scenarios in which through-hole mounting may still be utilized in modern PCB assembly, for the most part, surface mounted technology is superior.
Selecting a Vendor Who Offers Surface Mounted Technology
Because the costs to purchase the equipment and machinery required for SMT is so high, many smaller electronics companies find it difficult to take advantage of this efficient mounting technology. If this is the case, it is in your best interest to seek out a contract manufacturer who can offer these types of services. This enables you to incorporate SMT into the design and production of your PCBs without being required to purchase or maintain expensive equipment. Be sure to select a reputable vendor who stays on top of the latest and greatest technological developments, and is familiar with all of the best practices for manufacturing complex devices.
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