Mechanical strength, power handling, and field durability keep through-hole technology at the center of demanding electronics manufacturing.
Surface mount technology (SMT) gets most of the attention in modern PCB assembly, and for good reason — it enables compact, high-density boards at scale. But when a product needs to survive vibration, carry significant current, or stay in service for a decade or more, engineers still turn to through-hole technology (THT). Components with leads that pass completely through the board and are soldered on the opposite side produce joints with mechanical retention that surface mounting alone cannot match.
This article examines where
through-hole soldering service fits in contemporary electronics manufacturing, what the process actually involves, and how a capable manufacturing partner like Farway Electronic in Shenzhen, China brings it together with testing, inspection, and certification to deliver boards that hold up in the field.
Where Through-Hole Assembly Still Wins
Despite the miniaturization trend in consumer electronics, through-hole components remain standard in many product categories. The reason comes down to physics: a lead soldered through a plated hole anchors the component on both sides of the board, distributing mechanical and thermal stress far more effectively than solder pads alone.
This matters most for:
Connectors and terminal blocks that undergo repeated mating cycles and cable pull.
Transformers and inductors where component weight and vibration are concerns.
Large electrolytic capacitors in power circuits that generate heat and mechanical stress.
Relays and switches in industrial and automotive environments.
Heat-dissipating power components that benefit from board-level thermal paths.
In short, any application where a board faces physical shock, sustained vibration, or high current is a candidate for through-hole construction. That is why the technology persists across automotive, industrial control, power electronics, medical devices, and communications infrastructure.
Wave Soldering: The Engine of Through-Hole Production
For volume through-hole assembly, wave soldering is the primary method. The process is straightforward in concept but demanding in execution: a conveyor carries the populated board across a molten solder wave, which fills the plated holes and wets the component leads in a single pass. The challenge lies in controlling solder temperature, conveyor speed, wave height, flux application, and preheat profile so that every joint achieves proper fill without bridges, cold spots, or excess solder.
Farway Electronic operates two plug-in production lines equipped with Nitto wave-soldering machines in its 2,000-square-metre facility in LongGang, Shenzhen. The published DIP process flow runs from component forming and insertion through wave soldering, lead cutting, repair welding, board washing, and finally functional testing — a sequence designed to catch defects at each stage rather than relying on end-of-line inspection alone.
For boards that combine SMT and through-hole components, Farway also supports mixed-technology assembly, routing surface-mount parts through reflow soldering first and then running the board through the wave soldering line for leaded components. This
wave soldering service approach lets customers use a single manufacturing partner for both compact layouts and mechanically demanding parts.
The Through-Hole Assembly Process at Farway
A controlled, repeatable process is what separates reliable through-hole production from inconsistent hand work. Farway's published DIP workflow includes the following steps:
- Component forming: Axial and radial leads are cut and formed to the correct pitch and stand-off height.
- Insertion: Operators ｉｎｓｅｒｔ components into their designated holes with attention to orientation, polarity, and placement accuracy.
- Wave soldering: The board passes over the molten solder wave on Nitto equipment, with preheat and flux parameters set for the board's thermal mass and component mix.
- Lead cutting: Excess leads are trimmed to specification after soldering.
- Repair welding: 24 rear-welding stations handle touch-up and rework for any joints that need correction.
- Board washing: A board-washing machine removes flux residues and contaminants.
- Functional testing: Boards undergo electrical verification to confirm solder joint integrity and circuit functionality.
This structured flow, combined with trained and certified operators and controlled work-in-process areas, is what makes
high quality through-hole soldering achievable at production scale rather than just in prototyping.
Inspection and Quality Control
Soldering is only as good as the inspection behind it. Farway applies IPC-A-610 as its PCBA assembly standard and layers multiple inspection methods throughout the through-hole process:
| Inspection Method | What It Catches |
|---|
| Plug-in AOI | Component presence, orientation, and placement errors before soldering |
| IPQC sampling | In-process quality checks during insertion and soldering |
| QA sampling | Post-soldering workmanship verification per lot |
| Functional testing (FCT) | Electrical performance and solder joint conductivity |
| X-ray inspection | Hidden solder defects under components or inside plated holes |
| Thermal imaging | Heat distribution anomalies that signal poor connections |
The result is
dip plug-in welding with testing built into the process rather than bolted on at the end. Farway also states a one-year free-repair commitment for eligible non-external defects arising during standard customer use, which reflects confidence in the assembly quality.
Certifications That Matter for Through-Hole Work
When selecting a through-hole manufacturing partner, certifications provide an objective measure of process discipline. Farway Electronic holds the following management-system certifications, each relevant to specific through-hole application areas:
| Certification | Relevance to Through-Hole Assembly |
|---|
| ISO 9001 | Baseline quality management across all manufacturing processes |
| IATF 16949 | Automotive-industry quality — critical for vibration-prone through-hole boards |
| ISO 13485 | Medical device quality — supports reliability-critical through-hole assemblies |
| ISO 14001 | Environmental management — covers soldering materials and waste handling |
The company also lists UL, RoHS, SGS, and REACH within its product-certification scope and follows IPC-A-600H for PCB implementation and IPC-A-610 for PCBA assembly. These standards give customers in regulated industries a documented framework to audit against.
Applications Across Industries
Through-hole assembly is not a niche technique — it shows up wherever mechanical durability and electrical reliability converge. Farway's service areas reflect this breadth:
Transportation & Automotive
Control units, lighting modules, and power distribution boards exposed to vibration, temperature swings, and harsh operating cycles.
Industrial Control
PLCs, motor drivers, and factory automation equipment where connectors and power components need robust mechanical retention.
New Energy
Power conversion boards, battery management systems, and charging controllers handling high current and thermal stress.
Medical Devices
Equipment where assembly quality and component stability directly affect patient safety and long service life.
Communications
Networking and telecom hardware relying on durable connectors and dependable solder joints over extended service cycles.
Security Systems
Alarm and surveillance electronics that must operate reliably in varied environmental conditions for years without intervention.
What to Look For in a Through-Hole Soldering Partner
Not every PCB assembly house invests in through-hole capability to the same degree. When evaluating a partner, consider these practical factors:
- Equipment: Dedicated wave-soldering machines and enough rear-welding stations to handle rework without bottlenecks.
- Process documentation: Published workflow from forming through testing, not just a vague promise of quality.
- Inspection coverage: AOI, IPQC sampling, QA sampling, and functional testing as standard, not optional upgrades.
- Certifications: ISO 9001 at minimum, with IATF 16949 or ISO 13485 if your industry demands them.
- Mixed-technology support: The ability to run SMT and through-hole on the same board without shipping between vendors.
- Volume flexibility: Capacity for prototype, pilot, and production runs so you do not switch partners mid-program.
Farway Electronic brings all of these together under one roof in Shenzhen, with two SMT lines, two DIP plug-in lines, two wave-soldering machines, 24 rear-welding stations, and a board-washing machine in a single 2,000-square-metre facility. Since its establishment in 2018, the company has served more than 100 industry customers across more than 20 countries and regions.
Ready to Start Your Through-Hole Assembly Project?
Whether your board needs pure through-hole construction or a mix of SMT and THT on the same PCB, Farway Electronic provides the equipment, process control, and certified quality systems to get it built right. From component forming and wave soldering through functional testing and shipment, the entire workflow runs in one Shenzhen facility.
Contact Farway Electronic today:
Email: sales@farway.hk
Phone: 181 2472 7402
Website:
www.farway.hk
