If you’ve ever stood inside a busy electronics manufacturing facility—dodging carts loaded with printed circuit boards (PCBs), listening to the high-pitched whine of pick-and-place machines, or talking to an engineer troubleshooting a prototype—you’ve probably heard two phrases thrown around like they’re industry gospel: surface-mount connectors and through-hole connectors. As someone who’s spent the last 12 years running a small, family-owned connector supply company, I hear these terms almost daily from designers, production supervisors, and even hobbyists who are building their first custom drone. What surprises most people isn’t just that the two exist—it’s how often they get mixed up, even when the choice could make or break a product. Today, let’s cut through the marketing fluff, skip the jargon that makes your eyes glaze over, and break down exactly what sets these two connector types apart. Connector
First, let’s get one thing straight: both surface-mount technology (SMT) connectors and through-hole (THT, or through-hole technology) connectors serve the same core purpose. They create a reliable, removable electrical connection between two components—whether that’s a PCB and a display, a PCB and a power supply, or two separate PCBs stacked inside a laptop case. The difference is in how they attach to that PCB, and that tiny technical detail ripples through every part of a product’s lifecycle: design, prototyping, mass production, repair, and even long-term performance in the field.
Let’s start with through-hole connectors, because they’re the old guard—like that trusted wrench in the back of your toolbox that you still reach for no matter how many new power tools show up. If you’ve ever worked on a vintage radio, an old computer, or even a simple wall adapter, you’ve seen through-hole connectors in action. Their defining feature is those metal pins—usually two or more, sometimes arranged in a grid or linear pattern—that stick straight out from the bottom of the connector body, like little nails. To attach them to a PCB, you drill holes right where you want the connector to sit, push those pins through the holes from the top (or component side) of the board, then solder them from the bottom (or solder side) with a iron or in a wave soldering machine. The solder wraps around the entire pin, creating a physical, mechanical bond as well as an electrical one.
I won’t lie—through-hole connectors have some pretty obvious upsides. For one, that mechanical bond is tough. If you’re building something that will take a beating: a rugged outdoor sensor, a industrial control panel that gets vibrated all day on a factory floor, or a children’s toy that gets dropped a dozen times before Christmas, through-hole is almost always the safer bet. Those soldered pins don’t pull out easily, even under stress. They’re also way easier to work with when you’re prototyping. When I first started in this business, I’d sit at a workbench with a PCB, a bag of through-hole connectors, a soldering iron, and a multimeter, and I could have a basic board wired up in an hour—no fancy pick-and-place machine required. Hobbyists and small-batch makers love through-hole for that reason, too; you don’t need thousands of dollars in equipment to get started.
But there’s a reason SMT took over most of the industry by the early 2000s: through-hole has some major drawbacks. First, size. Those pins and drilled holes mean through-hole connectors are bulkier. You can’t fit as many I/O ports, power rails, or interconnections on a single small PCB if you’re using through-hole—every pin takes up extra space on both sides of the board. That’s a big deal for smartphones, wearables, and even modern laptops, where every square millimeter of PCB counts. Then there’s production speed. Wave soldering works for through-hole, but it’s not as fast as surface-mount soldering. With through-hole, each pin has to go through a hole, which means more time aligning parts on the assembly line. And if you make a mistake—like soldering a pin to the wrong pad—fixing it means desoldering the entire pin, which can damage the PCB or surrounding components.
Now let’s talk about surface-mount connectors, the new kid on the block that’s taken over the modern electronics landscape. Instead of sticking pins through holes, SMT connectors mount directly to the surface of the PCB. Their contacts—usually small, flat metal tabs or tiny metal feet—sit flush against the solder pads on the board, and you solder them straight down. No drilling holes, no pins sticking through the other side. The result? Connectors that are smaller, lighter, and much more compact. You can fit way more of them on a single PCB, which is why you see them everywhere now: in your iPhone’s charging port, in smartwatch bands, in the tiny camera modules used in security cameras.
The biggest upside of SMT is production efficiency. Pick-and-place machines can pick up hundreds of SMT connectors per minute, align them perfectly, and place them on a board in seconds—way faster than hand-placing through-hole connectors or even loading them into a wave machine. That speed translates directly to lower production costs for mass-market products, which is why Apple, Samsung, and all the big tech brands switched almost entirely to SMT years ago. There’s also less risk of damage during assembly; since there are no through-holes to drill, you’re less likely to crack a thin PCB. SMT also leaves the other side of the PCB completely free, which is huge for designs where you need to stack multiple boards (like in a gaming laptop, where the main board, CPU board, and GPU board all connect with SMT connectors).
But SMT isn’t perfect—ask anyone who’s tried to repair a broken smartphone charging port, and they’ll tell you that story. The surface-mount bond is much weaker mechanically than through-hole. Those tiny solder pads can crack if you drop a product, or if it’s exposed to constant vibration in a car or farm sensor. You can fix that with reinforced SMT designs, but they add cost. And prototyping with SMT is a total hassle for small batches or hobbyists. You can’t easily align an SMT connector by hand; you need a pick-and-place machine, reflow ovens, or specialized soldering tools that most people don’t have in their garage. If you mess up an SMT solder joint, it’s not as simple as desoldering a pin—you might have to replace the entire connector, which is more expensive than a through-hole part.
Now that we’ve got the basics down, let’s get into the details that matter most for your next project, because picking the wrong connector can cost you time, money, and even product failures. Let’s break down the key difference factors: size and weight, mechanical durability, production cost, repairability, and use case.
Size and weight: This is where SMT wins, hands down. A through-hole USB connector is almost twice as long and heavy as a comparable surface-mount USB-C connector. For any portable device, wearables, or compact IoT sensor, SMT is non-negotiable. If you’re designing something that fits in the palm of your hand or has to be light enough to wear, SMT is your only option. Through-hole is too bulky and heavy for those applications.
Mechanical durability: Here’s where through-hole shines. If your product is going to be exposed to shock, vibration, or frequent mating/unmating (like a keyboard connector, a power tool battery connector, or a portable medical device that gets connected and disconnected daily), through-hole is the way to go. The soldered pin creates a much stronger connection that can withstand repeated stress without failing. SMT works for low-stress applications, but if your product is going to take a beating, through-hole is more reliable—though modern reinforced SMT designs are closing this gap fast.
Production cost: For small batches (100 units or less), through-hole is cheaper. You don’t need specialized equipment; you can hand-solder parts for just a few cents each, and you don’t have to pay for pick-and-place time. But for mass production (10,000 units or more), SMT is far cheaper. The automated process is much faster, labor costs are lower, and you can fit more connectors on a single board, reducing material waste. The sweet spot for SMT is usually batches of 1,000 units or more.
Repairability and rework: This is a big one for products that will be serviced, like industrial equipment, medical devices, or electronics sold with extended warranties. Through-hole connectors are easy to repair—if a pin breaks, you can desolder it with a standard iron and replace it in minutes. SMT connectors require specialized tools (like hot air rework stations) and more skill to replace, and the cost of rework is much higher. If you’re building a product that will be repaired in the field, through-hole is the more practical choice.
Wait, but here’s a question I get all the time: can you mix both? Absolutely. I’ve worked with engineers who design a board with SMT connectors for the high-density interconnections on one side, and through-hole connectors for the power and ground pins on the other. That’s totally common, especially in mid-sized industrial electronics. You get the best of both worlds: compact, fast-to-assemble connections for data, and tough, easy-to-repair connections for power.
Let’s talk about some common misconceptions, too. A lot of people think through-hole is obsolete, but that’s just not true. Last year, a customer of mine who builds rugged GPS trackers for construction sites ordered 50,000 through-hole power connectors, and a big reason was that their products are run over by heavy machinery, vibrated 24/7 on job sites, and need to be repaired in the field by on-site technicians. They couldn’t risk an SMT connector cracking and leaving a track unusable. On the flip side, a startup that makes a tiny wireless earbud charging case ordered 2 million SMT connectors last quarter, because they needed the compact size and low production cost for their mass market launch.
Another thing to consider: connector type. Different connector designs work better with each technology. For example, board-to-board connectors that are only connected once during assembly work great as SMT, since they don’t need to be mated or unmated. Connectors that are for external cables, like USB or HDMI, are often SMT now, but you can still get them in through-hole for rugged applications. And for power connectors that carry high current, through-hole is still more common, since the larger pins can handle more heat and current than tiny SMT pads.
So, how do you choose which is right for your project? Let’s make this simple. Ask yourself three questions:
- Is size or compactness a priority? If yes, go SMT.
- Will your product be exposed to shock, vibration, or frequent repair? If yes, go through-hole.
- Are you building a small prototype or mass-producing thousands of units? Small batches = through-hole, mass production = SMT.
Of course, there are always exceptions. I once worked with a aerospace engineer who needed a tiny, rugged connector for a satellite component—they used a reinforced SMT connector that had extra solder and a metal bracket to add mechanical strength, so they got the best of both worlds. That’s the kind of custom solution we love working on, too.
At the end of the day, there’s no “better” connector type—there’s only the right connector type for your specific needs. Both through-hole and surface-mount have their place in modern electronics, and the best designers know how to pick the one that will make their product reliable, cost-effective, and fit for purpose.
If you’re working on a new project and aren’t sure which connector is right for you—whether it’s a prototype, a small batch, or a mass-produced product—our team has years of experience helping clients navigate these decisions. We don’t just sell connectors; we work with you to understand your product, your production process, and your long-term needs, so you don’t have to deal with costly mistakes down the line. We’d love to hear about your next project and help you find the perfect connector solution.
DC Contactor References:
- Doane, J. D. (2019). Surface Mount Technology: Principles and Practice (3rd ed.). McGraw-Hill.
- Harper, C. A. (2016). Electronic Materials and Processes Handbook (2nd ed.). McGraw-Hill.
- Electronic Industries Alliance. (2020). Through-Hole and Surface-Mount Connector Design Standards. EIA-364.
Zhejiang Aokai Electric Co., Ltd.
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