PCB Assembly

A Comprehensive Guide to PCB Soldering Techniques


    Every electrical appliance, from your phone to your toaster, relies on printed circuit boards. These most intricate parts cannot be put together without soldering, which is essential for making the connections that give them their functionality. But the soldering process in the circuit board assembly is difficult if you don't know the nitty-gritty.

    This blog will discuss all the essential factors you need to know about PCB soldering so you can confidently take on any project.

    Essential Tools for PCB soldering

    To perform PCB soldering for printed circuit board assembly. There are some essential tools that you need to keep ready.

    Soldering iron: 

    Select the right soldering iron that allows you to regulate the temperature; for most electronic tasks, this should be between 300 and 400°C (572 and 752°F).


    Select a narrow diameter (about 0.7-1 mm) for accurate tasks. Considering safety and environmental concerns, lead-free solder should be used wherever possible.

    Solder wick: 

    With this tool, you can easily remove those small solder errors.

    Safety glasses: 

    Use safety glasses to stay safe from solder splatter that might fly into your eyes.

    Advanced Soldering Techniques for PCB Assembly

    Soft soldering: 

    Soft soldering is the preferred method for attaching small components to a PCB due to its common usage and compatibility with low-liquefying temperature components. To secure these components to the board, a filler metal, typically a tin-lead alloy with a melting temperature exceeding 752 degrees Fahrenheit, is used.

    This alloy acts as a binding agent, facilitating a solid connection between the component and the board. Gas torches are commonly employed to provide the necessary heat for the soldering process, causing the alloy to melt and effectively adhere the component to the board.

    Hard soldering: 

    Hard soldering refers to processes that use molten filler metals to permanently join two metal components together. It consists of two main subprocesses:

    • Silver soldering utilizes cadmium-silver alloys as filler metals and is often used for smaller components and circuit board repairs. Flux is commonly employed to facilitate reliable silver solder joints.

    • Brazing joins base metal components using liquid brass or other filler metals that flow into the joint by capillary action. Once solidified, the filler forms a strong, diffusion-bonded joint between the two components.

    Both silver soldering and brazing produce durable metal assemblies capable of withstanding elevated temperatures and stresses, making these processes essential across various industries.

    Preparations for PCB Soldering:

    Maintaining a clean and well-organized workspace is crucial for successful PCB soldering. The work area should be well-lit, and the printed circuit board should be cleaned with isopropyl alcohol to remove any debris that could impede the soldering process.

    Proper iron tinning is also essential. Before beginning, the soldering iron tip should be coated with a thin layer of solder while it is heating up. This process aids in heat transfer and prevents the solder from adhering to the tip.

    Component preparation is another important step. For through-hole components, bending the leads slightly to form a small hook can help secure the component during soldering.

    PCB Soldering: Step-by-Step Procedure:

    Heat the joint: 

    Apply the soldering iron tip to the junction between the component lead and the PCB pad. Allow a few seconds for the component and pad to receive heat from the joint.

    Apply the solder: 

    Once the joint is heated, touch the solder wire to the opposite side of the iron tip, not the joint itself. The solder will melt and flow onto the hot joint, creating a smooth bond. Avoid using excessive solder.

    Remove the iron and solder: 

    After forming a solid solder joint, simultaneously remove the soldering iron and the solder wire. Allow the solder to cool completely before moving the joint to prevent weakening the connection.

    Inspect and trim: 

    After the solder has cooled, inspect for defects such as solder bridges (unsightly connections made of excess solder) and cold solder joints (dull and gritty joints). Use a solder wick to remove excess solder and trim any protruding component leads.

    Soldering is a critical process in printed circuit board assembly, and mastering PCB soldering requires practice and attention to detail. By following the above tips and procedures, you can achieve error-free circuit board assembly and ensure reliable connections between components and the PCB. To learn more about automated soldering methods, refer to our blog on Wave Soldering or Reflow Soldering- Which One is Right for You?
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