Soldering a PCB is the process of populating a bare printed circuit board (PCB) with electronic components and all the other required parts. How to solder a PCB board? There are three methods for PCB soldering:
- Surface Mount Technology (SMT),
- Plated Through-Hole (PTH),
- Manual soldering.
At PCBONLINE's turnkey PCB assembly factory, all the above three methods are available to solder PCB boards. However, to ensure high-quality and robust results, we use SMT and PTH most often, and only in cases not suitable for SMT and PTH, do we use a hot air gun for manual soldering without touching the board by hand.
SMT Assembly: Fully Automatic and Precise Soldering
Surface Mount Technology (SMT) is a fully automated process for placing and soldering components directly onto the surface of a PCB. This method is ideal for high-density, complex, flexible, high-performance boards and batch production. Here's how SMT soldering works:
- Solder Paste Application: In a solder paste printing machine, a precise amount of solder paste is pressed through the holes of an SMT stencil to apply to the component pads on the PCB. The paste is a mixture of tiny solder spheres and flux. Following the solder paste application, a solder paste inspection machine checks the solder paste to ensure its solderability.
- Component Placement: Pick-and-place machines accurately position the surface mount components onto the solder paste. On each of the four SMT lines of PCBONLINE, there are two high-speed and one functional pick-and-place machine. Our machines can place up to 376 components per PCB board.
- AOI Before and After Reflow: PCBONLINE's SMT soldering includes a dual automatic optical inspection (AOI) system. Our AOI inspections are three-dimensional. The AOI inspections before and after reflow soldering ensure the PCB soldering quality and prevent economic losses of failed reflow soldering.
- Reflow Soldering: The populated PCB travels through a lead-free and programmable reflow oven. The oven's controlled heating profile melts the solder paste, which then cools and solidifies, creating strong electrical and mechanical connections.
The fully automatic SMT process ensures high precision and consistency of PCB assemblies, making it the backbone of modern electronics manufacturing.
PTH Assembly: Half-Automatic and Robust Soldering
Plated Through-Hole (PTH) technology involves inserting component leads through drilled holes in the PCB and wave soldering. PCBONLINE's PTH assembly is a half-automatic process that guarantees robust connections.
PTH soldering is known for its durability and is often used for larger, heavier components that require a stronger physical connection to the board. Besides SMT, High-power, high-current, and high-voltage applications usually require PTH assembly.
- Component Insertion: Operators or machines insert the leads of through-hole components into the plated holes on the PCB.
- Wave Soldering: The board is placed in a custom fixture and passes over a wave of molten solder. This wave of solder flows up through the holes and around the component leads, creating a reliable joint. This half-automatic approach combines machine efficiency with human oversight, ensuring a strong, dependable bond.
PTH components are more resistant to mechanical stress, making them perfect for connectors, large capacitors, and other parts that may experience physical force.
Manual PCB Soldering: Using a Hot Air Gun
While SMT and PTH handle the majority of components, sometimes, there are specific parts that cannot be soldered using these automated methods. For these cases, manual or hand soldering is performed by our skilled technicians. Besides, if a PCB assembly is found with any soldering issues during PCBA tests, the board will be reworked and manually soldered.
At a professional PCB assembly factory, manual soldering is not using a soldering iron like a DIY at home practice. It uses a hot air gun.
Manual soldering is a meticulous soldering process, optional in the post-assembly. It is used for:
- Rework and Repair: Correcting any defects from the automated processes.
- Specialty Components: Soldering unique, odd-shaped, or sensitive components that are not compatible with reflow or wave soldering.
Note: We don't encourage or use hand soldering for prototypes and low-volume runs. Quality is the most important consideration for us. For small-scale projects, we also solder PCBs using SMT and PTH technologies. At PCBONLINE, manual soldering is the last thing we want to do for PCB assemblies, and those reworked boards will be marked for recognition and separated from the other boards.
Hand soldering provides the flexibility needed to handle the odd-shaped components. We ensure the final product that has been manually soldered is flawless by comprehensive tests and inspections, including the PCBA functional test, burn-in test, in-circuit test, and application simulation test.
Under continuous ventilation, our technicians use a pair of tweezers to carefully place an appropriate amount of tin and flux on the PCB, then pick up the component and carefully place it, and then maintain a hot air gun above the PCB soldering point at an appropriate distance for an appropriate time period. With this manual process without touching the board by hand, the odd-shaped component is firmly soldered to the PCB.
PCB Box Build Assembly
After the soldering and assembly stages are complete, the populated PCB can be integrated into its final enclosure. This process is known as box build assembly. It includes installing sub-assemblies, wiring, and testing the entire system. PCBONLINE's full range of services extends to box build assembly, providing a complete turnkey solution from a bare board to a final, ready-to-ship product.
By combining the precision of SMT, the robustness of PTH, and the flexibility of manual soldering, our factory delivers high-quality, reliable, and complete electronic assemblies.
Partner with PCBONLINE for Turnkey PCB Soldering
With 20 years of expertise, advanced manufacturing facilities, and strict quality control, PCBONLINE provides robust and high-quality turnkey PCB manufacturing and soldering.
Our two advanced PCB manufacturing bases are in Jiangsu and Jiangxi Provinces, and our turnkey PCB assembly factory is in Shenzhen. Besides, we have an R&D team and a global supply network, with our component supply team centered in Hong Kong.
We provide one-on-one free and professional DFM before and during prototyping/sampling, to ensure the manufacturability and project success.
The professionals at PCBONLINE design the PCBA fixtures and manufacturing molds that accurately fit the PCBA manufacturing and test processes.
Complete equipment and capabilities for turnkey PCB soldering, including PCB manufacturing, SMT assembly, PTH assembly, value-added (such as functional test, IC programming, and burn-in test), enclosures, and box-build assembly.
PCBONLINE manufactures, assembles, and tests PCBs and PCBAs to box builds as a source factory manufacturer under one roof, from prototypes to bulky production, saving costs and time for you.
PCBONLINE can design the test points for your PCB and offer improvement suggestions for your design if there needs any optimization.
When your turnkey PCB project enters mass production, we refund the fees for prototypes and offer free PCBA functional testing.
Whether you need prototype assembly, PCB low-volume runs, or high-volume box build production, we have the equipment, experience, and capabilities to deliver superior results. To get a quote for turnkey PCB soldering, email us at info@pcbonline.com.
Conclusion
PCB soldering is a crucial process to turn a bare printed circuit board into a functional PCBA and module. We provide SMT, PTH, and manual soldering methods for PCB soldering under one roof. To ensure the manufacturing success of your project, partner with the turnkey PCB manufacturer PCBONLINE.
PCB assembly at PCBONLINE.pdf
