Not every component belongs on the surface of a board. High-power connectors, large capacitors, transformers, and heavy-duty switches all rely on through-hole mounting, where pins pass entirely through the PCB and are soldered on the opposite side. For volume production of these boards, the dominant method remains wave soldering, a process that immerses the bottom of the assembled PCB in a flowing wave of molten solder alloy, forming thousands of joints in seconds.
Understanding how wave soldering service works, and what separates a well-controlled line from a problematic one, helps engineering and procurement teams make better sourcing decisions when their projects include through-hole components.
Surface-mount technology handles the majority of modern PCB assembly, but through-hole technology (THT) remains indispensable for components that require strong mechanical bonds or carry high current. A connector bolted to an enclosure, a power transistor mounted to a heatsink, or a transformer weighing several hundred grams, these parts need the pin-to-board anchoring that only a plated through-hole solder joint provides.
The trade-off is that through-hole assembly is slower and more complex than SMT. Components must be inserted, held in place, wave-soldered, cleaned, and inspected, all without damaging nearby surface-mounted parts that were already reflowed. This is why many electronics manufacturers turn to a dedicated dip plug-in assembly partner with the right equipment and process discipline, rather than attempting through-hole work on a general-purpose line.
Wave soldering transforms a board full of loose through-hole components into a finished, electrically connected assembly in a single pass through a multi-zone machine. The sequence breaks down into five core stages:
On a well-managed line, contact time between the board and the solder wave is tightly controlled, typically three to five seconds, long enough for reliable wetting but short enough to avoid damaging the board or components.
Wave soldering is powerful, but it is unforgiving when parameters drift. The most frequent defects include solder bridges between adjacent pins, cold or incomplete joints caused by poor flux activation or insufficient preheat, pinholes from trapped moisture, and shadowing, where tall components or improperly designed fixtures block the solder wave from reaching downstream joints.
Preventing these issues requires more than a good machine. It demands consistent flux density monitoring, verified preheat profiles, controlled conveyor speed, stable solder wave height, and regular solder-pot analysis to catch impurity buildup. Operators need training, and inspection stations need the right tools, from plug-in AOI to X-ray, to catch defects before they reach the customer.
Most production boards are not purely through-hole. A typical design combines SMT parts, reflowed first on the top side, with through-hole connectors and power components that need wave soldering afterward. This mixed assembly approach is where many suppliers struggle, because the wave soldering step must not disturb the already-reflowed SMT joints or damage surface-mounted parts on the bottom side.
The standard solution is to use selective pallets or fixtures that mask SMD components from the solder wave, or to apply high-temperature adhesive to hold bottom-side SMD parts in place. Choosing a partner that offers an one-stop smt + dip assembly service eliminates the need to split the project across two vendors, reducing logistics overhead and accountability gaps. With two SMT lines and two DIP lines in the same facility, Farway can run the full mixed-assembly sequence, SMT reflow, DIP insertion, wave soldering, and testing, under one quality system rather than three.
When a board is destined for a medical device, an automotive controller, or an industrial power system, the quality bar goes well beyond "looks good." The assembly standard that governs finished PCBA workmanship is IPC-A-610, which defines acceptability criteria for solder fillet size, wetting, through-hole fill, and defect limits. A reliable partner should be able to work to this standard and back it with documented quality certifications.
Farway's quality system includes ISO 9001 for general quality management, ISO 13485 for medical device manufacturing, IATF 16949 for automotive, and ISO 14001 for environmental management. The company assembles to IPC-A-610 and applies IPC-A-600H as its PCB acceptance standard. For through-hole work specifically, the DIP line includes plug-in visual inspection, AOI, FAI first-article inspection, and FCT functional testing, with a stated one-year free-repair commitment for eligible non-external defects arising during standard customer use.
Not every factory that claims DIP capability can handle complex mixed-technology boards at volume. Several practical factors separate a capable partner from a risky one:
Through-hole assembly rarely exists in isolation. A connector that needs wave soldering is usually part of a larger product that also requires PCB fabrication, component sourcing, SMT assembly, conformal coating, testing, and final box-build packaging. Splitting these steps across multiple vendors increases lead time, coordination cost, and the risk of finger-pointing when something goes wrong.
This is why many projects benefit from working with a single partner that can cover the full chain. Farway's service catalog runs from smt pcb assembly through DIP welding, conformal coating, low-pressure injection moulding, PCBA testing, and finished-product assembly, all supported by in-house PCB production and component management. The company serves customers across transportation, new energy, security, medical, and communications markets, and has worked with more than 100 industry customers across over 20 countries and regions since its establishment in 2018.
Wave soldering is one of the oldest automated processes in electronics manufacturing, and it remains one of the most demanding to do well. The difference between a reliable through-hole board and a field-failure waiting to happen comes down to process control, inspection discipline, and the experience of the team running the line. When your project involves high-power connectors, automotive-grade components, or medical devices where joint integrity is non-negotiable, choosing a partner with documented certifications, visible equipment, and an integrated SMT-plus-DIP capability is the most practical way to reduce risk.
Farway Electronic provides wave soldering, DIP plug-in welding, mixed SMT-plus-DIP assembly, and full box-build services from a single Shenzhen facility, with ISO 9001, ISO 13485, IATF 16949, and ISO 14001 certified quality systems.
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