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Cold Solder Joint – Everything You Need To Know

Here we will Learn what is Cold Solder Joint – Symptoms, Prevent, Repair and Fix Cold Solder Joint. Everything You Should Know About Cold Solder Joints.

Here we will Learn what is Cold Solder Joint – Symptoms, Prevent, Repair and Fix Cold Solder Joint. Everything You Should Know About Cold Solder Joint.

Introduction

Soldering is a crucial part of PCB manufacturing and assembly. Cold solder joint are the most common problems during PCB soldering. These types of solder joints hamper the performance of the printed circuit board to a large extent. Besides, cold joints increase the PCB assembly cost to a certain degree.

Cold Solder Joint

Figure 1- Cold Solder Joints On PCB Surface

Are you familiar with cold solder connections due to improper heating? Do you know how to handle this problem or to identify, prevent, repair and fix it?

Don’t worry. This issue requires sensitivity and calmness during the soldering process. This blog post will inform you the most possible causes of cold solder joint in PCB surfaces and their solutions.

Moreover, you will get a better understanding of different PCB soldering methods to upgrade your device’s efficiency. So, what are you waiting for? Let’s make a move.

What Is Soldering?

PCB soldering refers to a process that forms mechanical and electrical connections on a printed circuit board. Usually, manufacturers use a mixture of Tin (Sn) and Lead (Pb) to bind the electronic components on the PCB surface.

PCB Soldering

Figure 2- PCB Soldering

Do you think soldering is one of the most difficult part of PCB manufacturing?

Most PCB technicians and engineers will agree with you in this case. This is a basic part of PCB engineering. It helps mount the PCB components on circuit board whether you are using SMT (Surface Mount Technology) or THT (Through-hole Technology) assembly process.

But soldering acts as the core of troubleshooting and developing a circuit board. That’s why its importance in PCB assembly service is huge.

PCB manufacturers solder the PCB materials in versatile ways. On that sense, PCB soldering has

All of these processes have particular pros and cons. Manufacturers choose a suitable way of soldering concerning the PCB components, budget, client’s requirement, etc.

Usually, they incorporate a soldering station, solder iron, solder wire, etc to connect different elements on the circuit board. Besides, a solder iron tip, connected to a power source, is used in this process.

Read: Lead-Free Soldering: A Safer Approach to PCB Assembly

Check this video about PCB soldering process:

This iron tip gets heated to a certain temperature through a controlled heating mechanism. Then, it can melt the solder wire so that it can solder connections. Doesn’t it sound very easy?

Off course. But there are some complications that may occur during PCB soldering that resist to make a secure connection between different PCB elements. Then, the circuit board can’t work as you desire in terms of electrical or mechanical performances.

Have you any idea about the soldering issues in PCB manufacturing? Let’s find out.

Different Soldering Problems In PCB Manufacturing

A successful soldering entirely depends on the efficiency and experience of the technical persons who are dealing with this. As it is a performing medium, you can find lacking in many cases. That’s why improper solder joints are very common in the PCB industry.

PCB manufacturers need to face numerous problems regarding bad soldering. The most common complications caused by wrong soldering methods include –

Cold Solder Joint

It occurs when solder wire and soldering iron are not heated up to a certain degree. Then, solder iron tips become incapable of melting the solder wire properly. Cold solder joints are the most common and familiar soldering issue for the PCB manufacturers all over the globe.

Disturbed Joints

Disturbance in the case of solder joints happens mainly before the solidification of molten solders. It causes usually due to mechanical hazards during soldering.

Soldering Problems Of PCB

Figure 3- Soldering Problems Of PCBs

Inadequate Solder Wetting

This issue is related to the circuit board and pins of the PCB components. Insufficient wetting of solders refers to the uneven heating of solder on the pin or circuit board.

In the case of inadequate solder wetting for PCB, the technical staff can heat the circuit board more than the pin.

The scenario is different in the case of inadequate wetting for pin.

Overheated Joints

Overheating is a serious issue in solder joint applications. It happens when the solder iron is unable to melt the wire. Then, you need to increase the temperature that ends in burning of the solder flux of the PCB.

As PCB solder flux is a little bit hassling to handle, your soldering experience can become a nightmare in that case.

Insufficient Wetting For SMD Components

In this case, solder can’t flow to the pad of surface mount components. Usually, insufficient wetting for SMDs occur due to the excessive heating of pin in lieu of pad. You need to heat the pad earlier to avoid this problem.

Solder Starved Joints

Starve solder joints indicate insufficiency of solder in the connecting point. This type of solder may create a moderate electrical connection. But in the long run solder starved joints crack and create serious problems.

Moreover, starved joints are critical to inspect. That’s why you can’t ensure perfection in PCB soldering.

Excessive Solder In Joints

If you apply too much solder in a joint, you can achieve a strong solder connection. But you can’t be sure of getting a reliable electrical connection. That means your principle target of soldering is uncertain. Will you prefer it? I don’t think so.

Solder Bridge

If two successive solder joints create a connection between them, it’s called solder bridge. It causes unwanted signal transmission and damage the PCB components due to irregular flow of heat and current.

Solder Bridge In PCB

Figure 4 – Solder Bridge In PCB

Lifted Pad

This problem occurs when a solder pad gets disconnected from the PCB surface. You can notice this issue mostly in the case of desoldering. Besides, overloading on a solder point hampers the adhesives between PCB and copper.

Except for these, you can face some less complicated issues like spattering of stray solders, untrimmed leads, etc. But you don’t need to panic for these problems. If you can consult with a reliable and experienced PCB manufacturer, it can take care of soldering perfectly.

What is Cold Solder Joint?

When the PCB solder doesn’t get heated properly and fail to melt entirely, it is called Cold solder joint. These types of solder connections create convex shapes on the pins and flexible portions of PCB surface.

Cold Solder Joint

Figure 5 – Cold Solder Joint

In some cases, cold joints have rough and dull appearance. When you fail to heat the solder wire to the required temperature before soldering, this problem arises. Again, unwanted disturbance in the PCB and solder before they become solid, can cause cold solder joint.

Are you panicked at thinking about the consequences of this issue?

The effect of cold joints is not very attractive in terms of electrical features. Cold joints increase the solder resistance that hampers the current flow between PCB components. If the solder connection becomes very cold, the circuit board may fail to conduct electricity. That means you have to replace the board in that case.

Moreover, these joints can’t handle vibration as the metals are not bonded strongly. Even, irregular temperature change can cause serious damage for cold solder connections. Eventually, the solder joint gets broken and fails the circuit board.

You can find cold soldering in substandard PCB applications. Besides, it has become common in comparatively newer technologies like flexible printed circuits.

Different Cold Solder Joints

You can notice various cold solder joints while handling a circuit board. All of these electrically and mechanically vulnerable solder joints have distinctive effects and repair methods.

Here, we are presenting the most usual cold solder joint types for your convenience. Let’s have a look.

Distributed Cold Joints

When the solder alloy is placed on the designated portion of PCB, sometimes solder iron starts moving. This phenomena is known as distributed cold solder joint. It can be distinguished by a concave shape, titled pin, crystalline, etc.

The movement of PCB is the main reason of distributed cold solder joint. If you can stop PCB movement, you can avoid this issue successfully. You can perform the soldering procedure by keeping the circuit board on a properly mounted soldering vice or PCB holder. It helps stabilize the PCB during operations.

Cracked Solder Joint

Some cold solder connections get cracked due to mechanical stresses or inadequate solder. The component pin becomes free in this case and it causes the complete breakage of electrical conduction systems.

Cracked Solder Joint

Figure 6 – Cracked Solder Joint

Usually, cracked solder joints are the result of gravitational forces produced by heavy PCB components. In most cases, vertically mounted components cause high gravity and crack the solder joints. This cracking may expand if the circuit board face vibration or flippering.

So, how do you prevent cracking in solder connections?

Manufacturers usually place a CRT (Cathode Ray Tube) monitor in the solder pad. CRTs can minimize vibration to a great extent that results in reduction of solder cracking.

It is important for you to know that all cracked solder joints are not cold joints. But they can reduce the efficiency of circuit board if ignored.

Dry Solder Joint

This is another kind of cold solder connection that occurs in PCB-based electronic appliances. Insufficiency of solders is the main reason of dry solder joints. These joints contain inadequate amount of metals. That’s why they suffer from open connections in some incidents.

Most importantly, dry connections promote electrical resistance and irregular current flow. So, you can experience noise during the operation of PCBs.

In many cases, you may find a cold solder connection contain the features of both dry and cracked connections. If you can’t identify the pattern of solder joints, consult an experienced assembly service provider to handle the situation. It will save your time and cost in the long run.

Prominent Causes Of Cold Solder Joints In PCB

We have already mentioned the main reason of PCB cold solder joints. But a circuit board can suffer from cold joints because of versatile reasons which may be not directly related to this issue.

Here, a list of prominent reasons of cold joints in PCB soldering is given for you.

  • Contamination in solder mixture of Tin and Lead.
  • Unmatched component placement
  • Dimensional instability
  • Unfinished wetting
  • Too low temperatures
  • Unwanted reflow over the solder joint
  • Untimely break down of solder flux due to high temperatures
  • Selective soldering frame
  • Disturbance between PCB and PCB components

If you take care of these matters, you can hope to prevent cold solder connection in different types of PCB.

Importance Of Solder Joints In PCB

Solder joint is a particular interconnecting point where electronic components get connected to the circuit board. It has a significant role in promoting the PCB performance to the next level.

The shape of solder joints are highly crucial. A perfect solder joint’s shape is concave. It needs to have a smooth and little bit glossy molten solder so that this solder can reach the pin of the PCB component.

Soldering In Prototype PCB

Figure 7- Soldering In Prototype PCB

Improper shape of solder joints can’t establish a perfect connection between PCB components. Besides, it affects electrical properties in a negative way. It results in frequent trouble in PCB materials. Then, you have to suffer from high repair cost.

Do you know how to repair a PCB having bad solder joints?

You need to manage a skilled person who has expertise in different types of PCB soldering. It requires a lot of experience to bring smoothness and perfection in applying the solder wire and iron. That’s why don’t ignore this issue during your circuit board manufacturing.

How to Identify and Test Cold Solder Joint?

From our hands-on experience, we can understand the irritation occurs due to cold solders during PCB assembly process. Especially, if you are dealing with a high-volume PCB production, it will become so much annoying for an electrician to fix this problem.

That’s why it is necessary to identify cold solders in the primary stage. Otherwise, you may encounter some unwanted experiences. For example, the circuit board may stop working or take a huge time to respond. Sometimes , the PCB elements can give unrealistic results which is very time-consuming.

If you continue the PCB operation without fixing the cold solder issue, there is a big chance of developing a faulty electronic application. So, you must conduct reliable tests to identify cold solder connections and repair them quickly.

But how do you know which tests are dependable or not?

Don’t be puzzled. It’s time to explore the most effective inspections to identify cold solder joints.

Visual Inspection

You can check the functionality of cold solder connections through a visual inspection. This is the most easiest and practical way to identify cold joints. It enables you to be sure about the existence of cold joints from different soldering problems.

This test requires some visual equipment like magnifying glass and light. These materials help check the connectivity of solders between two ends.

You need to lighten up the connection point between component and PCB surface. If you find that the light passes through the solder joint easily, you can get assurance of inadequate bonding of solder connections.

Besides, you can notice roughness on cold joints. It indicates that the solder alloys are not heated properly. This problem can result in detaching the solder from the circuit board. Moreover, PCB becomes hot when you place it in an electronic application.

You need to check another thing visually. It is spilling of solder joints over to another one that is connected to them. This scenario is rare in PCB soldering but is not impossible to happen. It leads to short circuit issue that often fails the circuit board.

You need to use your common sense while conducting this visual observation. As you know that cold joints are dull, convex, deformed, etc. You should check very carefully. You can tilt the component soldered on the circuit board to check its detachment.

Checking Through Multimeter

You can check cold solder joints by using a multimeter. There are two effective ways of using multimeter to serve this cause. These are-

  1. Testing the Continuity – You need to connect two terminals of a multimeter to the ends of cold joints. You can hear a beep sound if there is no problem of discontinuity. That means the solder joint is functioning despite having cold joints.Irregular beeping indicates discontinuation and no sound means rework. But you must set the multimeter to the continuity mode in the beginning.
  2. Testing The Resistance – In this testing, set the multimeter resistance at 1000 Ohm. Then, interconnect two terminals of the multimeter. If the resistance is zero, you can be sure that it is working.Then, connect the terminals to different solder joints. In the case of a defective cold joint, the multimeter reading will be anything except zero. That means there a cold solder joint exists.

Watch this video for better understanding:

How To Repair and Fix Cold Solder Joints

Despite your all effort, your circuit board can encounter a cold solder joint. Then, you have to deal with the situation and fix this issue properly. But how?

Cold Solder Joint Repair

Figure 9 – Cold Solder Joint Repair

This question has no direct or one-liner answer. It depends on the types of cold joints and mechanical stability of your PCB. The most suitable way of repair cold solder joints include –

Problem   Solution
Distributed Cold Solder : Use a soldering vice / PCB Holder. It keeps the PCB stable and secured.
Typical Cold Solder :

Heat the soldering iron properly.

Use lead free solder wire having a lower melting point transition time.

Excessive Solder : Use a hot iron tip, solder wick, or solder remover to remove the excess solder.
Starved Solder Joints : Heat the solder joint again and include more solder as required.

How to Avoid Cold Solder Joint

To avoid cold solder joints in PCB assembly, you need to ensure efficiency and perfection in soldering. So, it is important to follow the best possible ways to promote the soldering method.

The best practices that help avoid cold joint issues include –

Using Appropriate Equipment

This is the most vital part of handling cold solder connections. Most of the time, bad soldering occurs due to low-quality soldering tools. If we tell more specifically, don’t compromise in the case of soldering iron. It performs the melting part of solder wire.

That’s why manage an ideal solder iron that is easy to control and supportive of controlled heat supply. You must collect it from a reliable source. Otherwise, all of your further efforts will go in vain.

Temperature Control

Temperature plays a crucial role in PCB soldering, irrespective of its type. You must maintain a moderate thermal state which is not more or less for the solder wire to be melted properly.

Using Sufficient Solder

Over soldering or staved joints are two common causes of cold soldering. So, you need to arrange adequate solder during the operation. Try to apply minimal amount of solder mixture. It reduces the opportunity of creating cold solder situation.

Proper Environment

Soldering is a technical task that requires high-class perfection. That’s why ambience is very important in this matter. You have to set the circuit board on a stable vice during soldering. Besides, eliminate all possible source of vibration from that place.

Clean Soldering Iron

It is necessary to clean the soldering iron on a regular basis. Besides, ensure that soldering tools are stored in dust-free place. Try to keep solder iron and wires away from moisture contamination.

Flawless Power Supply

Ensure a continuous power source that powers the soldering iron or gun while soldering.

Lead-free Soldering

Due to RoHS, Nowadays, manufacturers are trying to follow the rules of green electronics during PCB assembly. You can also support this issue by using lead-free solder wire. It improves the ecological effectiveness and reduces the complications to a higher degree.

Time Management

It is prohibited to be impatient during PCB soldering. You have to give sufficient time to heat the soldering iron and melt the wire perfectly. Otherwise, you don’t get the desired output.

Use Experience

You need to be confident on your expertise and experience while dealing with cold solder joints. New technicians often get panicked and shake soldering iron. Be cool and follow the reflow profile guidelines properly.

You can think about getting this service from a trustworthy manufacturer. Then, make sure that the technical staffs are skilled and professional enough to handle this.

Conclusion

PCB soldering makes the electrical connection improved in electronic devices. As cold solder joints are regular problems of PCB applications, you need to take proper steps to reduce its occurrence.

PCBMay is a well-known PCB manufacturer in China. The company have been providing a trustworthy manufacturing and assembly service including soldering for around 15 years. You can contact the company to get the best service at affordable costs. To know more about different aspects of PCB manufacturing, stay tuned.

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Santosh Das

Santosh, founder of this Electronics Tutorial Website, is an Electronics Geek, Blogger and Young Entrepreneur. He possesses vast experience in the field of electronics, electronic components, PCB, Soldering, SMT, Telecommunication, ESD Safety, and PCB Assembly Tools, Equipment and Consumables. Keep visiting for daily dose of Tips and Tutorials.

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