Soldering is a crucial procedure that involves melting solder to join electronic components to printed circuit boards (PCBs). It forms permanent electromechanical bonds. The most common technologies used for PCB manufacturing and Assembly are wave soldering and reflow soldering. This blog will introduce reflow soldering and wave soldering, discuss their advantages and disadvantages, and discuss their process. It will also show how wave soldering differs from reflow soldering.
Wave soldering is used in THT technology during PCB assembly, while reflow soldering is used in SMT technology during PCB assembly. Regardless of which technology, FC PCBA as China’s excellent PCB manufacturer can provide you with the technology and services!
Wave Soldering
What is Wave Soldering?
Wave soldering is a method for applying solder paste to PCBs using a wave effect that spreads the paste at high pressure and temperature, typically between 200°C and 600°C depending on the metal. This efficient technique connects copper wires and utilizes heat sources like induction coils or torches, requiring special tools such as high-voltage transformers and capacitors.
During the process, components are positioned on the board, and a wave of hot solder flows over them using a wave soldering machine. There are two types of wave solders: vibratory and electromagnetic. Electromagnetic soldering employs a field to generate heat, while vibratory soldering oscillates at high frequency to create joints.
Pros & Cons of Wave Soldering
Wave soldering offers a variety of advantages for electronics manufacturing, especially when it comes to through-hole component assembly. However, it also has some limitations and drawbacks. FC chooses which technique to use based on the characteristics of the product.
Advantages of Wave Soldering | Disadvantages of Wave Soldering |
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Wave Soldering Process
At FC, the different processes of wave soldering consist of four steps. They are spraying flux, pre-heating, wave soldering, and cooling.
Step 1: Fluxing
During this stage, flux is applied to the PCB. The purpose of the flux is to remove the oxidation layer from the board's surface and to prevent the formation of new oxidation layers. There are several types of flux, including:
- Rosin-based Flux
- Water-soluble Flux
- No-clean Flux
Fluxing can be done in two ways: spray fluxing and foam fluxing.
- Spray Fluxing: In this method, flux is sprayed onto the underside of the board. Any excess flux is then removed using a compressed air jet.
- Foam Fluxing: This method involves adding flux to a tank containing a submerged plastic cylinder with holes. A metal chimney on top of the cylinder pumps air, which creates a foam of flux. As the PCB passes over this foam, the flux is applied to its surface.
Step 2: Pre-Heating
Wave soldering technologies involve higher temperatures for PCBs. This high temperature may cause a thermal shock to PCBs and their electronic components, causing the board or individual components to fail.
PCBs go through a preheating process that causes their temperature to rise gradually to prevent failure. Heaters that generate hot air are used to pre-heat PCBs. The PCBs are heated by the heaters and then directed toward the wave soldering equipment. The PCBs are occasionally preheated using infrared heaters. The PCB is heated effectively, avoiding hot or cold areas.
Preheating not only stops thermal shocks but also turns on the flux. The flux subsequently removes the oxidation layer, leaving a clean surface ready for soldering.
Step 3: Wave Soldering
Melted solder is applied to the PCB to form long-lasting connections between the parts. The exposed metal pads are covered by the solder wave, which is usually made of a solder alloy. Solder connections are formed through the processes of wetting and solidification.
Regulating the solder wave’s temperature and contact time is essential to achieving regular and dependable solder junctions. Variables including solder wave height, conveyor speed, and solder alloy composition are also essential to maximize soldering parameters.
Step 4: Cooling
The solder joints are quickly solidified during the cooling cycle, stabilizing the assembly and avoiding faults. Several cooling techniques, including water quenching and forced air cooling, can be used, depending on the particular needs of the assembly and production environment.
Maintaining the strength of the solder junctions and preventing heat stress on components require controlled cooling. In addition to reducing the possibility of faults like solder fractures, proper cooling raises the soldered assembly’s overall reliability.
Reflow Soldering
What is Reflow Soldering?
Reflow soldering is a method of joining two metal pieces by applying pressure and heat. Unlike wave soldering, the result is a strong bond that will not break with regular use.
Smaller-scale reflow soldering is carried out. Heat guns are a cheap way to apply solder paste to your components and the board, but we should use caution while handling them because they may get very hot. Make sure your heat gun is at the right temperature before we begin, as solder can become toxic if overheated. For a Pb-Free (Sn/Ag) solder, the reflow temperature range is 240–250 degrees Celsius.
Pros & Cons of Reflow Soldering
Reflow soldering offers a variety of advantages that make it ideal for soldering surface mount components in the electronics industry. However, reflow soldering has some drawbacks that should be considered when selecting a soldering method.
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Advantages of reflow Soldering |
Disadvantages of reflow Soldering |
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Reflow Soldering Process
FC’s reflow soldering has different processes, including pre-heating, thermal soak, reflow soldering, and cooling.
Step 1: Pre-Heating
The preheating procedure serves two main functions for reflow soldering:
- The PCB assembly can effortlessly attain the required temperature to guarantee thermal profiling.
- Any volatile solvents in the solder are forced out and assisted in their expulsion by preheating.
Step 2: Thermal Soak
The type of solder flux included in the solder paste can affect the soldering process. The solder needs to heat up considerably to activate this flux. Soldering will not be successful if the flux is not activated by the solder.
Step 3: Reflow Soldering
The goal of reaching the maximum temperature is to facilitate the appropriate melting and reflow of the solder paste. A temperature that is too high can destroy a board or even harm its components, while one that is too low might completely prevent this operation. Controlling the temperature is essential to the operation in every way.
BGAs that are not soldered correctly may have unequal ball-to-ball contacts and a greater likelihood of unravelling during reflow soldering. Manufacturers concentrated on creating more effective reflow soldering procedures as a result of this accessibility.
Step 4: Cooling
The temperature curve will begin to decline as soon as the temperature hits the top. The solder paste and components are permanently bonded to their contact pads after it cools.
Difference Between Wave Soldering and Reflow Soldering
From the above introduction, I believe you have a certain understanding of reflow and wave soldering. A summary of wave and reflow soldering is given below:
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Wave Soldering |
Reflow Soldering |
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Involves molten solder forming a solder wave.
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Involves the use of high-temperature hot air to create reflow and melt solder.
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Faster and cheaper.
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More expensive.
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The wave soldering process takes less time.
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This reflow soldering process takes more time.
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Less reliable
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More reliable
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It produces large PCBs.
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It produces less PCB. |
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Mainly used for soldering through-hole components.
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Mainly used for soldering surface-mounted components.
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A complex technique.
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A relatively uncomplicated technique.
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FC PCBA has 22 years of experience in soldering printed circuit boards, and we help you manufacture your products with the best products. We have strong production capabilities for wave soldering and reflow soldering. In addition, we have a large production facility that can perform any soldering technique in bulk. We offer a one-stop shop that can save you time and resources! Therefore, FC is your most trusted partner!
If you need to solder PCB, contact us immediately. We look forward to hearing from you!
Conclusion
Reflow and wave soldering provide complimentary benefits when it comes to PCB assembly. Wave works well for big boards, double-sided soldering, and through-hole insertion, whereas reflow is best for SMT components with precise pitches. It is more complicated in certain aspects. Careful observation is required for board temperature and time spent in the solder wave.
