What causes poor solder flow (how to fix, 2023)
For a solid and reliable soldering connection the flow of solder is crucial. Poor solder flow may result in weak and unreliable joints, which will impact the performance of the device or project you are working on as a whole.
Several reasons are involved in poor solder flow such as incorrect temperature setting, contamination and oxidation on surfaces or iron tip, no use of flux, and incorrect soldering technique. By setting the temperature according to the component being soldered, proper cleaning and making use of flux can minimize the solder flow problem.
In this article, we will explore the common causes of poor solder flow and provide detailed solutions to fix them, helping you achieve flawless solder joints and reliable electronic assemblies.
What is meant by solder flow?
Solder flow refers to the process of molten solder flow to the surfaces of components and printed circuit board (PCB) pads during the soldering process.
When solder is heated to its melting point, a phase change occurs from solid to liquid, and it flows to create a bond between component lead and PCB pad.
There are different types of solder used for soldering, leaded solder, and lead-free solder. Both of the solders have a different melting point, lead-free solder has a high melting point as compared to leaded solder. For efficient solder flow temperature, the setting is also crucial.
For creating strong and durable solder joints the successful solder flow is essential. Proper solder flow ensures that the molten solder wets the surfaces it comes into contact with, resulting in a smooth, shiny, and well-formed solder joint.
The poor solder flow can lead to weak joints and can cause issues like cold joints, and solder bridges This can cause unreliable electrical connections, leading to malfunctioning devices or circuits.
Various effects can cause poor flow of solder and affect the overall performance.
Causes of poor solder flow
Let’s discuss the factors that impact the flow of solder and create weak solder joints.
1. Incorrect temperature setting
The first factor that can influence the solder flow is the temperature setting of the soldering iron. The temperature setting has a significant impact on solder flow during soldering.
If the temperature is too low, the solder will not melt completely, or it will take to melt, this will result in poor solder flow and create cold joints. The solder will also not spread evenly.
The too-high temperature of iron causes the solder to melt quickly and leads to damage to the components due to overheating, especially heat-sensitive ones like plastic connectors or sensitive electronic parts.
2. Contamination and oxidation
The contamination and oxidation on the tip of the iron or on the surface to be solder also affect the solder flow. Contamination such as dirt, flux residue, and grease formed a barrier between the solder and the surface to be solder.
The same is with oxidation, if the tip of the iron is not clean proper or the iron is not stored in a dry place its tip will be oxidized or rusted which will reduce the heat transfer property of soldering iron and enough heat will not be provided to solder to melt down. This will result in weak soldering connections.
3. Inadequate Flux
Flux is a chemical compound that is used in the soldering process to remove oxidation and improve the flow of solder to create a strong and reliable soldering connection.
Without sufficient flux, oxidation can build up on the surfaces, creating barriers that inhibit the solder from adhering effectively.
This results in poor wetting, where the solder forms uneven and incomplete connections, leading to weak joints that may compromise both the electrical conductivity and mechanical stability of the soldered components.
4. Incorrect soldering technique
The incorrect soldering technique is also a reason for poor solder flow. If you apply excessive heat it will damage the component and low heat will not melt solder to its melting point and result in poor solder joints.
Applying too much solder due to improving heat application, leads to solder bridging due which causes unintended connections between adjacent components, causing short circuits.
Weak and unreliable joints are created due to the use of little solder because solder is not spread evenly.
How can you fix it?
The incorrect temperature setting and soldering techniques, no use of flux, and contamination and oxidation are the reasons that can affect solder flow.
How can you fix it? Don’t worry we will provide full guidelines to make the solder flow efficient.
1. Proper temperature setting
To have a good flow of solder ensure you have an appropriate soldering iron with temperature control like this one (Amazon link) or a standard soldering station like Weller station (Amazon link). Before soldering components read the datasheet or manufacturer’s guidelines for the recommended temperature range for the soldering.
Make use of a temperature control soldering iron that offers adjustable temperature and will make it easy for you to set the proper temperature for your project solder.
To achieve optimal solder flow and create strong electrical connections set the temperature accordingly.
2. Removing contamination and oxidation
As we already mentioned contamination such as dirt, solder residue, and oxidation make the solder flow poor. Make sure you clean the surface, including the PCB pads and component leads, using isopropyl alcohol or dedicated flux removers.
Having a clean surface is essential for enhancing the flow of solder and ensuring a high-quality solder joint. Use a wet sponge or brass sponge to clean mild oxidation from the tip of the iron.
3. Use of flux
As we know flux is an agent that enhances wetting properties. Flux cleans the contamination and oxidation from the surface being soldered and from the tip of the soldering iron to enhance the solder flow.
Apply the recommended amount of flux to the solder surfaces before soldering. Make sure the flux you are using is suitable for the components you are soldering.
4. Proper soldering technique
To enhance your solder flow and joint quality, it’s important to practice good soldering techniques. Tining the tip of the soldering iron enhances heat transfer.
Use the right amount of solder, not too much or too little. Apply heat to the joint and the solder simultaneously for a short period, achieving a quick and uniform flow.
Conclusion
While doing poor solder flow is sometimes frustrating so for a reliable soldering process the smooth flow of solder is essential. Poor solder flow can result in weak solder joints and unreliable connections.
Poor soldering techniques, contamination, oxidation on the surface being solder or on the soldering iron tip, incorrect solder temperature, and not use of accurate flux during soldering contribute to poor solder flow.
Make sure you use flux that is compatible with components, set the right solder temperature, always clean the surface and iron tip before soldering and apply the right soldering techniques. By taking all these steps you will have good solder flow and strong electrical connections.
At each step of the soldering journey, you will learn new things. Remember, consistent practice and attention to detail are key to mastering the art of soldering.
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