PCB Assembly

Wave Soldering or Reflow Soldering- Which One is Right for You?


    Soldering plays a significant role in the performance of electronics. Soldering is the process of connecting electronic components to a PCB using solder, a metal alloy that melts and solidifies to create strong electrical and mechanical connections. This process is fundamental to the functionality of the PCB because it establishes the electrical pathways between components.

    When we talk about PCB assembly, there are two primary soldering methods used to solder components on the PCBs. 

    1. Wave Soldering
    2. Reflow Soldering 

    In this blog, we will be talking about both wave soldering and reflow soldering. From the soldering process to the major differences between these soldering techniques.

    Wave Soldering

    In this technique, the components are soldered to the board with a temperature range of 240-260°C. The PCB is then moved over a pool of molten solder, which binds to the exposed metal surfaces of both the components and the PCB to form a strong, long-lasting bond. The pool of solder is typically composed of a tin-lead alloy.

    Wave soldering includes four steps.  

    Flux Spraying 

    The first step in ensuring the performance of the soldering process is the cleanliness of the metal surface. The performance of the soldering process also depends upon the functions of the solder flux. 

    Primary Functions of the Solder Flux 

    a. Ensuring protection from secondary oxidation of circuit boards during the thermal process. 

    b. Proper transmission of the heat. 

    c. To reduce the surface tension of the solder paste 

    d. To ensure the elimination of oxides from the metal surfaces and component pins.

    2. Pre - Heating

    In this step, PCBs travel with chains similar through a heat tunnel for the activation of flux and pre-heating.

    3. Wave Soldering

    The temperature rises continuously, and the solder paste melts to become liquid. This liquid travels throughout the board and this results in the solidifying of the components with the circuit boards. 

    4. Cooling

    When the Soldering profile conforms to the temperature curve, and the temperature has reached its peak in the wave soldering, it is reduced in the cooling zone. When this step is done, all the components are successfully assembled onto the board. 

    Reflow Soldering 

    In this technique, the components are initially temporarily stuck on the circuit board with the help of solder paste, and these components get soldered to the PCB through reflow soldering. This phenomenon takes place due to hot air or thermal radiation conduction. 

    This whole process of reflow soldering takes place in the reflow soldering machine.

    Reflow soldering includes four steps: 

    1. Pre-Heating 

    There are mainly two purposes of pre-heating in reflow soldering.

    a)     This phenomenon allows PCB assembly to easily reach the needed temperature and also achieve the necessary thermal profiling. 

    b)    It also helps in expelling the volatile solvents contained in solder paste. If this step is not performed properly then soldering quality is compromised. 

    2. Thermal Soak

    The reflow soldering process also depends on the flux that is inside the solder paste. During this phenomenon, the temperature needs to reach a certain level due to which flux will be activated, and if it fails to play its role then it might hamper the soldering process. 

    3. Reflow Soldering

    This process takes place when peak temperature is achieved, this allows solder paste to melt and reflow. Temperature plays a very significant role in reflow soldering. If the temperature is too low then it pauses the solder paste from reflowing, and if it is too high then it might cause damage to the surface mount technology components or even to the boards. 

    4. Cooling 

    Once the peak temperature is achieved, the temperature curve starts to go down. This cooling process solidifies the solder paste and then the components are fixed permanently. 

    Reflow Soldering and Wave Soldering are considered to be effective methods for PCB assembly. Wave Soldering is commonly used for the assembly of DIP and THT Components, and on the other hand, Reflow Soldering is used in SMT assembly. These soldering processes are essential for effective circuit board assembly. Get in touch with PCB Power for high-quality PCB Assembly services.

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