PCB Clearance and Creepage Distances – The Ultimate FAQ Guide in 2024

Introduction:

If you’re curious about PCB clearance and creepage distances, you’ve come to the right place. This guide provides a comprehensive overview of these key design elements and explains how to do it. You’ll learn how to incorporate them into your own designs and get the most out of your product.

When designing your own PCB layout, remember to consider PCB clearance and creepage distances. Incorrect measurements can lead to non-compliance issues or even damage valuable equipment. Fortunately, the right PCB design software will assist you in incorporating specific design rules to reduce the likelihood of spacing errors. This way, you can have a complete picture of your design before you design it.

Clearance and creepage distances are key parameters in electronic product design and are specified in many standards. IPC-2221 and IEC60601 certifications are the most widely used. Other standards have different rules that vary by application.

Creepage and Clearance

Creepage and Clearance

Creepage and clearance distances are critical when designing high-voltage circuits. They contain accidental arcing between conductors. They can be calculated in various ways, including the distance between component pads and exposed metal areas.

What Are Creepage and Clearance in PCB Design?

In PCB design, the terms “creepage” and “clearance” refer to the distance between conductive components. Clearance refers to the distance between the conductive component and the insulating material. The required distance is dictated by several criteria. The most common are IPC-2221A and UL60950-1, but there are other standards as well. Each standard has its own set of rules and is based on various environmental factors. Therefore, it is crucial to consult the relevant standards when designing a circuit board.

The two most common safety standards in PCB design are creepage distance and clearance distance. To ensure compliance with these standards, consult a product safety engineer when developing a design. These measurements apply to both the PCB and the components mounted on it. They are affected by factors such as operating voltage, degree of pollution, overvoltage category, and altitude.

The gap distance is the shortest distance between two conductors. Millimeters are used to measure creepage distances. It is the distance from one conductor to another conductor. When the clearance distance exceeds the creepage distance, the clearance distance shall be increased.

To prevent electrical equipment from malfunctioning, clearance distances and creepage distances must be kept at a certain level. These distances are often determined by the working voltage of the insulation. Clearance and creepage distances must be adjusted to meet the specific requirements of the application.

 

What Are the PCB Creepage and Clearance Standards?

When designing a PCB, it is critical to adhere to the clearance and creepage standards of the PCB. This is especially important when designing high-voltage circuit boards. When conductors come into contact with other components, higher voltages can cause them to arc. 3D creepage inspection is a good baseline for compliance.

The working voltage and the material used for the insulation determine the creepage and clearance criteria. The voltage creates a conductive path on the surface of the PCB, degrading the performance of the insulating layer. The CTI (Comparative Tracking Index) value of each material determines its insulating properties and how well it degrades. The higher the CTI value, the less likely the board will leak.

CTI (Comparative Tracking Index) value

CTI (Comparative Tracking Index) value

When designing a PCB, it is critical to use proper spacing between PCB components. Regulatory agencies set standards for clearance and creepage. These regulations reduce the risk of fire and electric shock. By using proper spacing between PCB components, you can design and manufacture safer products.

The outer layer must have sufficient voids to allow conduction. The gap between the layers varies but should be less than the thickness of the outer layer. Also, the outer layers do not have to be perfectly aligned, they can overlap as long as the creepage conditions are met. The main reason for the formation of perspective gaps is aesthetic reasons. Electrical reasons are less obvious but can be achieved by increasing substrate thickness.

How to Calculate PCB Creepage and Clearance?

Creepage and clearance are important considerations when designing high-voltage circuits. Higher voltage conductors can arc to other components if not properly spaced. To avoid this problem, analog and digital circuits must be properly spaced, as they are increasingly fused together.

The creepage distance of a PCB refers to the distance difference between the surface of the PCB and the surface of the component. Two-dimensional gaps are generally smaller than three-dimensional gaps. When using 3D gaps, you will be able to create a denser design.

A spreadsheet program can be used to determine the distance between two conductive elements on a PCB. Using the lookup function, you can recreate the creepage and clearance tables. You can enter the appropriate value and use the calculator to calculate the correct spacing with this. Remember that some standards allow interpolation, so you need to account for this in your calculations.

Calculate PCB Creepage and Clearance

Calculate PCB Creepage and Clearance

Clearance and creepage must be accurately calculated when designing a PCB. Creepage is the distance between a surface and insulating material, while clearance is the distance between two conductive parts on a PCB. When designing high voltage circuits, it is critical to follow clearance and creepage clearance rules.

How to Design for Creepage and Clearance?

When designing a PCB, it is critical to consider how the board is manufactured. There are several standards that specify creepage and clearance requirements. The most common are IPC 2221A and UL60950-1, but there are other standards as well. Each standard has its own set of rules that affect the required clearance. To determine the minimum clearance for a specific design, consult the relevant standards.

The gap distance is defined as the shortest air path on the protrusion. It can also refer to the rib space between two protrusions. When these two distances are the same, the gap distance is smaller. In contrast, creepage distances follow the contours of the grooves.

Creepage distances and clearances are key safety criteria, and design engineers must work with product safety engineers to develop an appropriate design. In addition to calculating minimum clearance distances, design engineers must also consider operating voltage as well as environmental factors such as altitude.

Use the creepage distance calculator to calculate clearance and creepage requirements. There are also some international creepage and clearance standards. Above 2,000 meters, these standards specify minimum clearance distances.

 

What Is the Minimum Electrical Clearance in PCB?

The shortest distance in air between the top and bottom of two conductive lines on a PCB is defined as the minimum electrical clearance. The gap can be increased or decreased depending on the voltage of the circuit. High-voltage components should generally be placed on the top of the board, while low-voltage components should be placed on the bottom of the board.

Some standards, including IPC2221A and UL60950-1, specify clearance requirements. They vary from environment to environment, so it is critical to consult the relevant standards when designing a PCB. In any case, if you’re not sure what you need, the IPC2221 calculator can help you figure out how much clearance your design needs.

The minimum electrical clearance on a PCB is determined by several factors, including the applied voltage, air pollution, and temperature fluctuations. For example, humidity determines the breakdown voltage of air, which is critical to preventing arcing. In addition, the accumulation of particulate matter and moisture can shorten the creepage distance. These factors are critical in determining the spacing of PCB components.

Conductors on Inner Layers

Conductors on Inner Layers

The electrical clearance between the outer and inner layers of a high-voltage PCB must be adequate. The outer layers must overlap, but are not required to be perfectly aligned. If the outer layers are affected by creep, they may overlap. While the electrical clearance between layers is more important than the aesthetics of the outer layers, see-through clearance is a common aesthetic concern. A practical way to reduce this is to increase the thickness of the substrate.

Why Do We Need Creepage Distance?

Creepage distance is a key design rule for electrical products. As more and more products incorporate electromechanical components, creepage distances are becoming more and more important to ensure worker safety. Longer creepage distances reduce the risk of premature insulator failure in high-voltage applications. Creepage distances are divided into two levels. Class I (light) and class II (medium).

The creepage distance on a printed circuit board is the distance between two adjacent conductor traces. This distance should not be less than one millimeter. A parallel-sided groove can be used to further extend the creepage distance, but it is more expensive than a V-groove. Another way to increase the creepage distance is to open a slot wider than 1mm. This method requires sufficient free space for the slot in one direction.

Creepage distance tables provide values ​​for common applications based on available data. These values ​​are suitable for most applications. The creepage distance table includes creepage distance values ​​for working voltage and rated voltage. However, some values ​​may not be suitable for every application. For example, a 15-pin high-density d-Sub micro connector has a contact pitch of 0.090 inches. The three rows of pins are offset by 0.045″, leaving 0.090″ between the diagonal contacts. Calculating the required clearance between conductors becomes easy when creepage distances are taken into account.

Creepage distances are divided into two types: basic and enhanced. The basic creepage distance is 3.5mm, and the enhanced creepage distance is twice that.

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