What Is Wave Soldering?
Wave soldering is a highly efficient method for soldering DIP (Dual In-line Package) components onto PCBs. Unlike manual soldering, this technique ensures consistent solder joints, making it indispensable in modern electronics manufacturing. As PCBs become denser and more compact, wave soldering must balance precision, reliability, and efficiency to meet production demands.
General wave soldering is a soldering technique for pin-type components (DIP). A special motorised pump unit jets the molten liquid solder (at a temperature of approx. 265°C) into a specially shaped wave of solder, into which the soldered surface of the plug-in board is immersed at a specific angle. The solder diffuses over the pads and wets the component pins, cooling down to achieve a reliable solder joint connection.
How Does Wave Soldering Work?
The wave soldering process is powered by specialized machinery consisting of key modules:
- Solder Pot: Maintains molten solder and generates a controlled wave.
- Fluxing System: Evenly applies flux to enhance solder adhesion.
- Preheating Module: Minimizes thermal shock and improves solder quality.
- Cooling System: Rapidly solidifies solder joints for durability.
The dual-wave system (turbulent wave and laminar wave) is a key feature of modern wave soldering.
- Turbulent wave, resembling a fountain, is responsible for the initial soldering process, effectively overcoming the shadow effect caused by component leads.
- Laminar wave, similar to a waterfall, smooths out the solder joints and corrects any defects left by the first wave.
This dual-wave setup enhances soldering quality by ensuring better wetting, minimizing bridging, and reducing solder voids. Additionally, it improves the reliability of fine-pitch components and high-density PCBs, making it a preferred solution for automotive, industrial, and power electronics manufacturing.
[Schematic diagram of wave soldering process illustrating PCB progression through flux spraying, pre-heating, solder wave, and cooling stages]
Step-by-Step Wave Soldering Process
1. Flux Application
Spray fluxes are for the purpose of removing oxides and improving solder wettability. The uniformity of spraying determines the probability of soldering defects.
2. Preheating
Preheating helps reduce thermal shock and prevents PCB warping.
- If the preheating temperature is too low or the duration is insufficient, the solder may not fully wet the pads, increasing the risk of solder voids and poor adhesion.
- If the temperature is too high or the preheating time is too long, the flux may decompose prematurely, leading to issues such as solder bridging or solder icicle formation.
3. Soldering with Dual-Wave System
The coordinated operation of the first and second solder waves ensures full, defect-free solder joints.
- The turbulent wave overcomes the shadow effect caused by component leads, ensuring proper solder coverage.
- The laminar wave further smooths the solder joints, reducing roughness and improving overall solder quality.
4. Cooling Stage
The cooling phase solidifies the solder joints and prevents them from being fragile or affected by thermal stress by rapidly cooling down (4-6°C/sec).
Best Practices for Optimal Wave Soldering
1. PCB Pre-Treatment
Before entering the wave soldering process, baking the PCB is recommended to remove any residual moisture.
- If the PCB is not properly dried, the high temperatures during soldering can cause trapped moisture to evaporate rapidly, forming gas.
- This may lead to solder spattering, where molten solder seeps through board gaps, resulting in solder defects such as voids.
2. Flux Application
Uniform flux application is critical, as both the spraying angle and distribution directly impact solder joint integrity and wettability.
- Ideally, the nozzle should be perpendicular to the PCB surface to prevent shadowing effects and ensure even flux coverage.
- Insufficient flux application can lead to poor wettability, while excessive flux may cause unwanted residues.
3. Preheating Control
The preheating temperature and duration should be adjusted according to the PCB material, thickness, and component characteristics. Typically, the temperature setting is between 90–130°C.
- Insufficient preheating time: Flux may not fully activate, leading to defects such as voids or solder balls.
- Excessive preheating time or high temperature: Flux decomposes prematurely, increasing the risk of bridging or solder icicles.
To minimize thermal shock and enhance stability, a gradual multi-stage preheating approach is recommended.
4. Solder Wave Temperature Control
The solder wave temperature is typically maintained between 255–265°C and should be fine-tuned based on the PCB and component heat dissipation characteristics.
- Low temperature: Increases solder viscosity, reducing wettability, which may cause solder icicles or bridging, and result in rough solder joints.
- High temperature: May damage components and lead to “overcooked” solder joints or internal cracks.
5. Cooling Optimization
The cooling rate significantly affects the mechanical strength and conductivity of the solder joints. An ideal cooling rate of 4–6°C per second ensures rapid solder solidification, preventing defects caused by thermal stress, such as cracks or deformations.
After cooling, immediate inspection for solder joints is to ensure quality and prevent component damage during subsequent handling.
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Enhance Your PCB Assembly with LCSC
Automotive, industrial, and power electronics manufacturers widely use wave soldering. Its benefits include:
- High-speed, mass production capabilities
- Superior solder joint reliability compared to manual soldering
- Seamless integration with complex PCB designs
LCSC offers comprehensive PCBA and SMT services, ensuring high-quality, efficient, and scalable manufacturing solutions. Whether you need component sourcing or full assembly, our platform provides an end-to-end service. Visit PCB Assembly | LCSC Electronics to learn more.
