Can a solder paste printer apply solder paste on through-holes?

Hey everyone, thanks for dropping by. I’m from a solder paste printer supply company, and lately I’ve been getting a ton of questions from our customers and industry folks alike: Can a solder paste printer actually put solder paste on through-holes? It’s one of those things that seems basic on the surface, but deep down, it’s got a lot of nuance that even seasoned manufacturing guys mix up sometimes. Let’s break this down like we would over a coffee at the shop—no confusing jargon, just straight talk.

First, let’s refresh what through-holes actually are, right? They’re those tiny, plated holes on a PCB that connect different layers together. For decades, people thought through-holes only worked with through-hole technology (THT) parts, where you stick a leaded component pin through the hole and solder it on the other side. But these days, a lot of designs mix surface-mount (SMD) and through-hole parts—called mixed-technology PCBs—and that’s where the confusion with solder paste printers starts. Everyone knows printers put solder paste on SMD pads, but can they handle the holes?

Here’s the short answer: It’s not a straight “yes” or “no” — it depends on the type of solder paste printer you’re using, the stencil setup, and how precise your process is. Let’s talk about the different kinds of printers because that’s where the real action is. We sell a range of these machines, from entry-level models to high-precision ones, and we’ve seen first-hand what works (and what doesn’t) when it comes to through-holes.

First, let’s cover the basics of how a solder paste printer works. The machine uses a stencil with cutouts that match the PCB’s pads (and sometimes holes) to lay down solder paste. A squeegee moves across the stencil, pushing paste through the cutouts onto the board below. If the stencil is just for SMD pads, the holes get nothing. But if you modify the stencil to target those through-holes, that’s when things get interesting.

Wait, let’s make sure we’re clear on the difference between solder paste printing for SMD vs. through-holes. For THT, traditional methods are either wave soldering (where you flow molten solder over the board) or hand soldering, but those come with their own headaches—like more labor, higher chance of defects, or inconsistent solder joints. Solder paste printing for through-holes is a different approach called “paste-in-hole” (PIH) technology, and that’s where printers come into play.

Now, not all printers are built the same. Let’s start with manual screen printers—these are the workhorses for low-volume, prototype, or small-batch jobs. A lot of hobbyists or small electronics shops use manual screen printers, and yes, they can do through-holes if you set up the stencil right. Our HW-S3040 Manual Screen Printer is a go-to for these jobs, honestly. It’s simple, affordable, and gives you enough control for small runs where you don’t need a fully automated line. But if you’re doing high-volume production, manual printers might be too slow and inconsistent for through-holes—you need something with way more precision.

That’s where semi or fully automated solder paste printers come in. These machines have servo-driven squeegees, accurate board alignment, and closed-loop vision systems that can line up stencil cutouts with through-holes down to the micron. For high-volume PIH applications, these are non-negotiable. But here’s the catch: even with a top-of-the-line automated printer, you can’t just use a standard SMD stencil. You need a specialized stencil—usually made from stainless steel with laser-cut through-holes that match your PCB’s vias or component holes. The stencil thickness matters too; if the hole is 0.3mm in diameter, the stencil shouldn’t be thicker than 0.2mm, otherwise the paste won’t fill the hole properly.

Wait, let’s talk about a common myth. Some people think because through-holes go all the way through the PCB, solder paste will just leak out the bottom if you print on it. That’s not true if you use the right stencil and adjust your printing parameters. A properly tensioned stencil keeps it flat against the PCB, and the right squeegee pressure lets paste fill the hole without oozing out the bottom. If you get the pressure wrong, though, you’ll get “solder balling” or empty holes—so process control is everything here.

Now, let’s connect this to the bigger picture of electronics manufacturing. The entire space of SMT electronic components manufacturing machines has evolved a lot over the last 10 years, and mixed-technology PCBs are way more common now than they used to be. A lot of consumer electronics, automotive parts, and even medical devices use both SMD and through-hole parts, and PIH is the process that makes that work well. Without reliable printers that can handle through-holes, those products would have to go back to more expensive, less efficient THT-only designs.

Another point: if you’re using a stencil printer for both SMD pads and through-holes, you have to design the stencil with two types of cutouts—one for the SMD pads (usually rectangular or circular) and one for the through-holes (same diameter as the hole itself, sometimes with a slight chamfer to help with paste release). Our team at [company name redacted, since we can’t use a real name] has seen customers get great results when they plan the stencil design upfront, instead of trying to modify an existing stencil last minute. Modifying a standard stencil for through-holes works sometimes, but it’s never as consistent as a custom stencil made for that exact job.

What about other types of machines? For example, high-precision SMT machines that do placement and printing in one? Wait, no—those are usually separate, but our Multi-layer PCB machine High-precision SMT machine category includes automated printers that are built for dense, multi-layer boards with lots of through-holes. Those machines have vision systems that can see not just the SMD pads but also the tiny through-holes, so alignment is spot-on. That’s important because if your stencil is off by even 0.1mm, the paste cutout won’t line up with the hole, and you’ll have a bad joint.

Let’s also talk about IC manufacturing industrial intelligent production lines. Those lines run 24/7, high-volume, and every process has to be repeatable. Solder paste printing for through-holes in these lines is mandatory because mixed-technology IC packages and components are everywhere. The automated printers in these lines can handle hundreds of boards an hour, each with dozens or hundreds of through-holes, and they have to get every single one right. There’s no room for error there—defects mean scrapped boards, which cost thousands of dollars.

Wait, let’s go back to our original question. So, to circle back: Can a solder paste printer apply solder paste on through-holes? The answer is a qualified yes—if you have the right machine, the right stencil, and the right process setup. You can’t grab a cheap entry-level manual printer and expect perfect through-hole fills on a high-density mixed PCB, but if you invest in a printer that’s built for accuracy, like the ones we sell, and work with our team to set up the stencil and parameters correctly, it’s not just possible—it’s a standard process now.

I should mention some of the common pitfalls we see. Number one: using the wrong stencil thickness. If your stencil is too thick, the paste can’t get into the deep through-holes, so you get partial fills. Number two: bad alignment. Even a small misalignment between the stencil and the PCB means the cutouts don’t line up with the holes. That’s why automated printers with vision systems are so much better for this than manual ones. Number three: using the wrong solder paste type. Not all pastes work for through-holes—you need a paste with good “pull” properties, so when the stencil lifts off, the paste stays in the hole instead of dragging back out.

Another thing: some people confuse through-hole printing with via filling. Vias are tiny holes for connecting layers, while through-holes are usually for component leads. But the same printing principle applies—adjust stencil and parameters to get paste into the hole. We’ve had customers use our printers to fill vias for high-frequency PCBs, which is a whole other use case, but it ties into the same core idea.

Now, let’s talk about when you might not want to use a solder paste printer for through-holes. If you’re doing a one-off prototype, hand soldering the through-holes might be faster and cheaper, even if it’s less consistent. If your through-holes are extremely small (like under 0.2mm in diameter), even the best printer might struggle—you might need a different technology, like jetting paste instead of screen printing. But for the vast majority of through-holes used in modern PCBs (0.3mm to 1.5mm), a well-set-up solder paste printer works perfectly.

At our company, we’ve been helping customers navigate this exact question for years. We’ve got case studies for automotive suppliers switching from wave soldering to PIH printing with our automated machines, cutting their defects by 60% and their production time by half. For small businesses just getting into mixed-technology builds, our manual screen printers are a great entry point—they’re easy to learn, and we provide free stencil design support to help them get through-holes right on their first try.

So, to wrap this up in plain terms: Solder paste printers can absolutely apply solder paste to through-holes, but it’s not a plug-and-play process. It requires choosing the right machine, designing a custom stencil, and tuning your printing parameters to match your specific PCB design. If you’re running a small prototype shop, a manual screen printer like our HW-S3040 is probably enough. If you’re doing high-volume production with dense multi-layer PCBs, you’ll want an automated high-precision printer that pairs with your SMT line. If you’re still on the fence about whether this process works for your application, don’t guess—reach out to our team, and we can walk you through what we’ve seen work for other customers in the same industry.

If you’re looking for reliable machines to handle all your solder printing and SMT needs, check out our range:

• SMT electronic components manufacturing machine: Our line of printers designed for everything from prototyping to full-scale production, with the accuracy to handle through-holes and SMD pads alike.
• Multi-layer PCB machine High-precision SMT machine: Our automated printers built for dense, multi-layer boards where through-hole alignment and fill are non-negotiable.
• IC manufacturing industrial intelligent production line: Integrated lines that handle every step, including solder paste printing for through-holes, for high-volume IC and component production.
• Manual screen printer: Entry-level models perfect for small runs and prototyping, with simple setup for through-hole applications.

If you’re ready to talk about your specific project, whether it’s a prototype, a small batch, or full production, our team is here to help you find the right machine and setup to get through-hole soldering done right. We don’t do generic solutions—we work with you to fit your needs, because we know every PCB is different.

References:
1.IPC-7525: Guidelines for Paste-in-Hole and Pin-in-Paste Processes
2. Smith, J. (2022). Modern Solder Printing for Mixed-Technology PCBs. Journal of Surface Mount Technology, 35(2), 45-52.
3. Zhang, L. et al. (2023). Through-Hole Solder Paste Deposition: Stencil Design and Process Optimization. IEEE Transactions on Electronics Packaging Manufacturing, 46(3), 121-128.
4. IPC-A-610: Acceptability of Electronic Assemblies, Through-Hole Solder Joint Requirements Section.