Circuits cold solder joint (How to identify and fix, 2023)
Cold solder joints are a common issue that is experienced by beginners. A cold joint is created when the soldering iron tip and solder wire are not heated up properly. Then, the iron’s tip is incapable of melting the solder wire resulting in a cold solder joint.
Several methods are used to identify cold joints while doing soldering such as visual inspection, the use of a magnifying glass, and multimeter testing. This allows you to identify the cold joints or your mistakes and correct them.
In the article, we’ll explore the various methods to identify cold solder joints and how to repair them. We will also know more about cold joints.
Let’s get started.
Cold Solder Joints
Soldering is a widely used process in various electrical and electronics industries where two or more metal components need to be joined together.
The process involves the melting of filler material called solder, which has a lower melting point than the metals being soldered.
The molten solder is applied to the joints and creates a solid and reliable electrical connection.
Now colder joints occur when there is no proper melting. Either the soldering iron tip wasn’t properly heated up or the soldering wire has not melted enough. In one or both of these cases leads to a lossy connection, called the cold connection or joint.
The cold joint results in poor electrical connection and can lead to signal degradation.
The cold solder joint is also known as cold solder connection or cold joint. It is a state in which solder connections are not properly formed due to improper soldering techniques and insufficient heating during the soldering process. Because of this, the joint may be weak mechanically and electrically, making it unstable and prone to failure.
Above is the proper definition of a cold joint. I hope you understand it. Now, let’s talk about the reasons why we face such connections in our circuit boards.
Cold solder joints causes
There are several causes for cold solder joints:
- One is the use of low-quality solder that may not melt and result in cold joints.
- The other is the use of a faulty soldering iron that is insufficient to provide proper heat to solder wire.
- If the soldering iron is not heated properly, it will not effectively melt the solder, which results in cold joints.
- The oxidation on the surface and at the tip of iron also results in a cold joint as the heat from the is not transferring properly to the components being soldering.
Mostly the cold solder joints are dull and have cracks which means the connection can break anytime.
How to identify cold solder joints
There are different ways to identify soldering cold joints and repair them. Let’s discuss how can you identify a cold joint in your PCB.
1. Visual inspection
The first and most simple way to identify cold joints is visual inspection. The functionality of cold joints can be done by visual inspection.
This requires visual equipment such as a magnifying glass and light. This will help you to check the connectivity between the two ends of the joints. When you light up the connection points of the joint if the light passes through the joint it means the joint is not fully connected.
Another way is by just looking at it, you can also identify cold joints. The cold joints are rough which means that solder wire is not properly heated. Unintentional connections can occasionally happen when the solder is moving towards another joint and connects. It leads to short circuits and failure of overall joints.
You need common sense for visual inspection. Cold joint appeared dull, convex, and deformed. Observe your circuit board and find the cold joints.
2. Multimeter analysis
Another method is analysis through a multimeter. You can also identify cold joints using a multimeter. There are two ways in which cold joints can be recognized.
The first is connectivity testing and setting the multimeter to continuity mode. You can connect the two ends of the multimeter to the cold joint. If you hear a beep sound it means there is no discontinuity and the connection is functional despite having cold joints. If the beep sound is irregular then the joint is discontinued and no sound means you have to rework that cold joint.
Now set the multimeter resistance at 1000 ohms for resistance testing. Connect the terminal of the multimeter to the cold joints. If the resistance is zero it means the joint is fully connected. Now connect the multimeter to another joint and if the joint is defective the resistance value will be other than zero. It means the joint is cold.
How to repair cold joints?
You may be creating your soldering joint carefully, but you can encounter solder-cold joints. Now you have to know how to deal with it and how to repair cold joints. To correct the cold joint first you have to know what type of cold joint is it.
1. Distributed cold joint
One type of cold joint is a distributed joint. It occurs when the molten solder is applied to the joint and moves the soldering iron without letting the solder cool down. It is called a disturbed joint because it is disturbed by the tilted pin and has a convex and crystalline appearance.
You can avoid these types of joints by working in a stable place and trying to not move the board or soldering iron before the solder cold down. This can be achieved using any circuit board holder like these helping hands from Weller (Amazon link).
2. Dry cold joint
A dry cold joint is formed when you apply too less amount of solder. For proper connectivity, the joint needs the right amount of solder, if it lacks that the joint is starving for solder and creates poor connectivity.
If the dry cold joint is, the current passing through it will face high resistance and result in a signal being noisy. To avoid this try to apply the recommended amount of solder to the joint and properly heat the joint.
3. Excessive solder
Applying excessive solder can also lead to cold joints. When you apply excess solder to a joint it will lead to unintentional connection. These connections which are not intended to be created can lead to short circuits and can damage the component or the overall circuit can become nonfunctional.
You can remove the excess solder by heating the soldering iron tip heat the excess solder and remove it. The problem can also be minimized if the right soldering technique is used and the recommended amount of solder is applied.
4. Typical cold solder
If the position of the tool is stable then the cold joint is due to soldering iron. It can be caused by the dust and oxidation on the tip of iron that affect the heat transfer property.
Always clean the soldering iron tip before and after use with a wet or brass sponge. Try to store the soldering iron in a box or a dry place to avoid dust and rusting of the iron.
Properly heat the soldering iron up to its optimal temperature depending upon the soldering material you’re working with. Select the recommended solder wire for your project.
Conclusion
The cold solder joint is something you can face when performing the soldering process. It is important to identify the cold joint before it fails the overall functionality of the project.
Different methods such as visual inspection and using a multimeter can help to identify cold joints. Visual inspection involves magnifying glass and light that determine different cold joints. These two modes in the multimeter are used like in continuity mode and setting the resistance at 1000 ohms.
The cold joint can be repaired after finding what type of cold joint is it. If too much solder is applied you can remove it with the help of a heated soldering iron and if too little solder is applied you can apply more solder and create a reliable solder joint.
Always remember, that a well-executed solder joint is the backbone of any successful electronic endeavor.
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