Through-hole technology (THT) mounts components by inserting their leads through drilled or plated holes in the PCB and soldering them on the opposite side. The resulting joint wraps around the plated barrel of the hole, distributing mechanical stress across a far larger area than a surface-mount pad can offer. This makes through-hole assembly the preferred choice for parts that experience physical strain — connectors that are plugged and unplugged repeatedly, transformers that vibrate, heavy capacitors, heat-dissipating power devices, and wire harnesses anchored to the board.
In mixed-technology boards, surface-mount parts handle the dense logic circuitry while through-hole parts carry the power and interconnect load. A capable manufacturer must therefore run both SMT and DIP lines in sequence, protecting already-soldered surface-mount components from the thermal exposure of the wave soldering step that follows.
Wave soldering is the backbone of volume through-hole production. The board, already populated with inserted components, travels along a conveyor through a carefully controlled sequence of stages.
The contact time between board and wave — typically just a few seconds — must be precisely tuned to the board thickness, component mass, and solder alloy. Too short and the solder fails to fill the hole; too long and the board or components suffer thermal damage. This is where equipment quality and operator experience prove their worth.
Not every factory that offers through-hole assembly service can deliver consistent quality across prototype, medium, and large production volumes. The following capabilities distinguish a production-ready partner from a basic assembly shop.
| Capability | Why It Matters |
|---|---|
| Multiple DIP lines with wave soldering | Parallel lines allow mixed-technology boards to be processed without bottlenecks and provide redundancy for delivery protection. |
| Trained, certified operators | Manual insertion and rear-welding stations require skilled hands for lead forming, touch-up, and rework that machines cannot perform. |
| Process-integrated inspection | Plug-in AOI, IPQC sampling, and QA sampling catch solder defects — bridges, cold joints, insufficient fill — before they reach functional testing. |
| Board washing after soldering | Removing flux residues prevents long-term corrosion and contamination, especially important for medical and automotive boards. |
| Functional testing on the same line | Performing FCT immediately after welding confirms electrical integrity without transferring boards between facilities. |
| Recognised quality standards | IPC-A-610 assembly criteria, together with ISO 9001 and IATF 16949 management systems, provide the audit trail that regulated industries demand. |
Farway Electronic, operating from a 2,000-square-metre workshop in LongGang, Shenzhen, runs a dedicated through-hole line engineered for high-reliability electronics. The DIP cell is built around two plug-in production lines, two Nitto wave-soldering machines, twenty-four rear-welding stations, and a board-washing machine. The published process flow runs from component forming and insertion, through wave soldering, lead cutting, repair welding, and board washing, all the way to functional testing — every stage on the same shop floor.
The DIP line does not operate in isolation. It sits between upstream SMT lines — equipped with Yamaha placement machines and Jintuo reflow ovens — and downstream protection and test stages that include conformal coating, low-pressure injection moulding, and a full inspection suite covering AOI, X-ray, ICT, FCT, and thermal imaging. This layout means a mixed-technology board can move from bare PCB to coated, tested assembly without leaving the facility — a true one-stop smt + dip assembly service.
Wave soldering is efficient, but it is unforgiving. The most frequent defects — solder bridges between adjacent pins, insufficient hole fill, cold or dull joints, solder balls, and lifted pads — each trace back to controllable process variables: flux activity, preheat profile, wave height, conveyor speed, and component orientation. A disciplined production line manages these variables through documented SOPs, periodic IPQC sampling, and automated inspection at the plug-in stage.
Farway reinforces defect prevention with a high quality through-hole soldering workflow that includes plug-in AOI, trained and certified operators, controlled work-in-process areas, and QA sampling before boards are released to the test stage. For eligible non-external defects arising during standard customer use, the company extends a one-year free-repair commitment — a warranty that only makes commercial sense when the underlying soldering process is consistently sound.
The mechanical robustness of through-hole joints makes them indispensable in sectors where boards face vibration, repeated mating cycles, or high current. Farway's through-hole assemblies serve customers across transportation and automotive electronics — including car-window lifter anti-pinch boards and automobile playback function boards — as well as new energy systems, security devices, medical equipment, and communication infrastructure. Each of these markets imposes its own qualification requirements, which is why Farway's combined IATF 16949 (automotive), ISO 13485 (medical), and ISO 9001 coverage is a practical advantage for OEMs that serve multiple regulated industries from a single supply base.
A frequent frustration for hardware startups is the gap between prototype assembly and volume production: the shop that hand-solders the first ten boards often cannot scale to ten thousand. Farway addresses this by accepting orders from a single prototype piece through medium batches to large-volume runs, all on the same DIP equipment set. Component sourcing is handled in-house through authorised channels with incoming inspection, ERP-tracked inventory, FIFO rotation, anti-static storage, and controlled temperature and humidity — so the parts inserted on the through-hole line arrive verified and ready.
For programmes that need more than soldering alone, the same facility offers wave soldering service alongside NPI support, DFX design review, program burning, stencil and fixture production, repair service, and finished box-build assembly. The result is a supply chain that can take a schematic to a shipped product under one roof.
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