What is Dendrite Growth on PCBs?

Dendrite Growth on PCBs may sound like a complex chemical phenomenon that seems far-fetched away from Electronics. However, dendrites are something that can have a significant impact on the performance and reliability of electronic devices like PCBs. These tiny dendrites are made up of conductive materials that can spread out on the surface of PCBs. Dendrites eventually bridge two or more conductive elements and hence, cause electrical short-circuits and failure.

In this article, we'll take a closer look at what Dendrite Growth is, how it occurs, and what can be done to prevent it. So, if you’re a PCB manufactures/enthusiast who is currently facing a Dendrite problem, stay tuned while we make things clearer for you.

Definition

So what is Dendrite Growth? The word Dendrite is commonly used to refer to a particular type of crystal that branches out in many directions like the branches of a tree. The word Dendrite similarly comes from the Greek word ‘Dendron’ which means a Tree. 

Coming back to PCBs, Dendrite Growth on PCBs refers to the formation of tiny, conductive filaments that can branch out and grow on the surface of a PCB board. Eventually, these branches of conductive material start bridging two or more adjacent conductive elements. These filaments, also called Dendrites, can form due to an electrochemical process called electrolysis, which can occur when there is an applied voltage and an electrolyte present between two conductive elements on the board.

Types of Dendrite Growth on PCBs

There are different types of Dendrite Growth on PCBs, which can be categorized based on the materials and conditions involved. Some of the common types of Dendrite Growth on PCBs include:

• Tin-Whiskers: These are hair-like protrusions that can form on the surface of tin or tin alloy coatings on PCBs.
• Copper Dendrites: Moisture or humidity can cause copper Dendrites to form on the surface of copper-coated PCBs.
• Silver Dendrites: When exposed to moisture or other contaminants, silver Dendrites can grow on the surface of silver-coated PCBs.
• Nickel Dendrites: When exposed to humidity or other environmental factors, nickel Dendrites can grow on nickel-coated PCBs.
• Zinc Dendrites: Galvanic reactions between the zinc and other materials on the board can cause zinc Dendrites to form on zinc-coated PCBs.

Each type of Dendrite Growth has its characteristics and can pose unique challenges for PCB designers and manufacturers. Understanding the different types of Dendrite Growth and their causes can help to inform strategies for preventing or mitigating this phenomenon on PCBs.

Causes that Lead to Dendrite Growth

Dendrite Growth on PCBs is a complex phenomenon that can be caused by a variety of factors. Here are some of the common causes of Dendrite Growth:

• Environmental Conditions: The presence of moisture on a PCB surface can provide the necessary electrolytes for Dendrites to form and grow. Additionally, high temperatures also add to it as hot surroundings can accelerate the diffusion of metal ions, making it easier for Dendrites to form.
• Electrical Causes: Electric current and electric fields can promote Dendrite Growth on PCBs. Electric current can create local hotspots on the surface of the PCB, which can promote the diffusion of metal ions and the growth of Dendrites. Electric fields on the surface of the PCB can also accelerate the migration of metal ions, leading to the formation of Dendrites when the concentration of metal ions becomes high enough. These factors make it important to consider the effects of electrical conditions when designing PCBs and developing methods for preventing Dendrite Growth.
• Material Selection and Mechanical Stress: Both of these factors can contribute to the growth of Dendrites on a PCB surface. It is widely known that metals such as copper, tin, and nickel are more prone to Dendrite Growth than metals like gold and silver. Adding to that, Mechanical stress on the surface of the PCB can also trigger Dendrite Growth because stress can cause micro-cracks in the metal surface. These crack sites provide nucleation sites for Dendrites to form.
• Contaminants: Contaminants such as oils, dirt, and other foreign particles can provide the necessary nucleation sites for Dendrites to form. These contaminants can also react with the metal surfaces on the PCB, leading to the formation of Dendrites.

Understanding the various causes of Dendrite Growth on PCBs can help electronics manufacturers and designers to take steps to prevent or mitigate its effects.

Consequences of Dendrite Growth

Dendrite Growth on PCBs leads to several consequences that harm the performance and reliability of electronic devices. In most cases, it is seen that adjacent conductive elements get closed due to formations and cause a short circuit. Even if a short circuit is prevented there might be other problems like electrical interference between the two conductive components, mostly resulting in signal degradation, noise, and other issues. Such electrical problems will lead to performance issues in the electronic device. For example, it can cause incorrect readings in sensors, slow down the processing of data, or cause other functional problems.

Apart from affecting the functionality of a PCB, Dendrite formation can damage a PCB and other components connected to it, leading to frequent repairs or replacements and increasing the cost of maintenance. In applications where high voltages or currents are involved, Dendrite Growth can pose safety hazards such as fires, explosions, or other accidents. Additionally, Dendrite Growth can lead to manufacturing defects in electronic devices, resulting in lower yields and higher production costs, which can make it more difficult to produce high-quality electronic products. It is, therefore, crucial to develop methods to prevent Dendrite Growth to ensure the longevity, safety, and quality of electronic devices.

Overall, Dendrite Growth can have a significant impact on the performance, reliability, and safety of electronic devices. Preventing or mitigating Dendrite Growth is therefore critical for the long-term success of electronic products.

How to prevent Dendrite Growth on PCBs?

There are several methods to prevent dendrite growth on PCBs, including:

• Coating and Surface Finish: Coating and surface finish can provide a barrier to prevent the diffusion of metal ions and the formation of dendrites. Some of the commonly used coatings and surface finishes include tin, gold, nickel, and silver.
• Material Selection: Choosing materials that are less prone to dendrite growth can help prevent this problem. For instance, using copper alloys with low oxygen content, such as OFHC copper, can reduce the risk of dendrite growth.
• Controlling Humidity: Controlling humidity can help prevent dendrite growth by reducing the moisture content on the surface of the PCB. This can be achieved by storing PCBs in a dry environment or by using a dehumidifier.
• Electrical Conditioning: Applying a voltage or current to the PCB before use can help condition the surface and reduce the risk of dendrite growth.
• Design Considerations: Proper design considerations can help prevent dendrite growth. For example, designing PCBs with wider spacing between conductive elements can reduce the risk of dendrite growth.

By using these methods, it is possible to prevent dendrite growth on PCBs and ensure the longevity, safety, and reliability of electronic devices.

Conclusion

In summary, Dendrite Growth on PCBs can have several dire consequences on the effectiveness and reliability of electronic devices. If conditions such as moisture, temperature, material selection, mechanical stress, and many other factors are not taken into account it can lead to the complete failure of your product and can even prove hazardous to the manufacturing unit producing it or the buyer using it. Hence, it is vital that precautions should be taken while producing PCBs and considerations like a design template, the material used, and electrical conditioning should be paramount.