November 7, 2017
For many years, through-hole technology was the standard method for securing component leads to a PCB. Over time, semiconductor packaging equipment has evolved. Surface mount technology, popularized about three decades ago, provides additional functionality and requires less space. Surface mount technology was expected to replace through-hole, but it continues to be used for a variety of applications.
When should you choose through-hole over surface mount? We’ll examine that question in this article.
The biggest advantage of through-hole mounting is its ability to create strong connections. Surface mounting secures components with merely a solder on the surface, while through-hole mounting runs component leads through the board. Through-hole technology is recommended for products that require high reliability, such as military and aerospace products that will encounter extreme environmental stress.
Through-hole is also used for prototyping, since it allows for manual adjustments, and parts are easily switched out. Another advantage of through-hole is availability — as long as surface mount technology has been around, not all components are available in surface mount. And several through-hole components are cheaper, so it can provide a cost advantage in certain situations.
The disadvantages of through-hole mounting are what drove the invention of surface mounting. Drilling holes takes time, making it more expensive. The routing area is also limited with through-hole mounting.
Perhaps the biggest disadvantage has to do with the soldering requirements associated with through-hole technology. You’ll need to use soldering processes that are less repeatable than the reflow ovens that are used with surface mounting. And you’ll need to solder on both sides of the board (contrasted with surface mounting, which generally needs soldering only on one side). For all of these reasons, through-hole mounting is merely used for a limited number of applications.
Surface mounting is much more popular today, due mainly to its cost-effectiveness. It doesn’t require any holes to be drilled through the PCB, making the process faster and more cheaper. Also, the components are smaller, and they can be mounted to both sides of the board, so you can fit a lot more components on a single PCB.
Surface mounting also did away with the through-hole component leads, replacing them with “vias,” which allow a conductive connection between the different layers of a PCB. Also significant, surface mounting is more stable and performs better in shake and vibration conditions.
The only real disadvantage of surface mounting is the fact that it doesn’t produce products that stand up to significant stress over time. If your product needs to withstand special environmental or mechanical stressors, you’ll want to examine this factor in relation to your requirements.
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