Get a Quick Online Quote: Register or Login

PCB Line Spacing

PCB Line Spacing: A Comprehensive Breakdown for High Voltage Applications

PCB line spacing is relevant to both safety and function when it comes to traces. Comprised of copper, fuses, and insulation, a trace is a conductive connection between different components on a PCB. Numerous factors determine the effectiveness of tracing, including PCB trace widths.

By connecting various signals, the trace serves as an important connection with its own sets of benefits and avoidable drawbacks.

Line tracing allows the signals to travel between different components. They’re beneficial but also prone to issues, as they’re susceptible to potential errors that could lead to a malfunction. But for products or circuit boards using high voltages, safety standards are extremely relevant. As line spacing between different conductive components increases, so do spacing standards. If the breakdown voltage is exceeded when safety standards aren’t adhered to, arcing could occur along the board, presenting issues between the traces.

Get your PCBs Built-Fast.

Contact us for a PCB quote
or call us at 1-800-SFC-5143

As technology continues to evolve, so do the standards by which it’s created. Designers have more capability and tools than ever, but high-voltage circuitry poses a number of challenges. When mixing any technologies, or creating important PCBs used for medical equipment or similar devices, accurate line spacing is a necessity. Over time, these practices have also been used to reduce product sizes and ultimately create more precise circuitry.

Electrical Conductor Spacing
Voltage
Between
Conductors
(DC or AC
Peaks)
Minimum Spacing
Bare Board Assembly
B1 B2 B3 B4 A5 A6 A7

0-15

0.05 mm
[0.00197 in]

0.1 mm
[0.0039 in]

0.1 mm
[0.0039 in]

0.05 mm
[0.00197 in]

0.13 mm
[0.00512 in]

0.13 mm
[0.00512 in]

0.13 mm
[0.00512 in]

16-30

0.05 mm
[0.00197 in]

0.1 mm
[0.0039 in]

0.1 mm
[0.0039 in]

0.05 mm
[0.00197 in]

0.13 mm
[0.00512 in]

0.25 mm
[0.00984 in]

0.13 mm
[0.00512 in]

31-50

0.1 mm
[0.0039 in]

0.6 mm
[0.024 in]

0.6 mm
[0.024 in]

0.13 mm
[0.00512 in]

0.13 mm
[0.00512 in]

0.4 mm
[0.016 in]

0.13 mm
[0.00512 in]

51-100

0.1 mm
[0.0039 in]

0.6 mm
[0.024 in]

1.5 mm
[0.0591 in]

0.13 mm
[0.00512 in]

0.13 mm
[0.00512 in]

0.5 mm
[0.020 in]

0.13 mm
[0.00512 in]

101-150

0.2 mm
[0.0079 in]

0.6 mm
[0.024 in]

3.2 mm
[0.126 in]

0.4 mm
[0.016 in]

0.4 mm
[0.016 in]

0.8 mm
[0.031 in]

0.4 mm
[0.016 in]

151-170

0.2 mm
[0.0079 in]

1.25 mm
[0.0492 in]

3.2 mm
[0.126 in]

0.4 mm
[0.016 in]

0.4 mm
[0.016 in]

0.8 mm
[0.031 in]

0.4 mm
[0.016 in]

171-250

0.2 mm
[0.0079 in]

1.25 mm
[0.0492 in]

6.4 mm
[0.252 in]

0.4 mm
[0.016 in]

0.4 mm
[0.016 in]

0.8 mm
[0.031 in]

0.4 mm
[0.016 in]

251-300

0.2 mm
[0.0079 in]

1.25 mm
[0.0492 in]

12.5 mm
[0.4921 in]

0.4 mm
[0.016 in]

0.4 mm
[0.016 in]

0.8 mm
[0.031 in]

0.8 mm
[0.031 in]

301-500

0.25 mm
[0.00984 in]

2.5 mm
[0.0984 in]

12.5 mm
[0.4921 in]

0.8 mm
[0.031 in]

0.8 mm
[0.031 in]

1.5 mm
[0.0591 in]

0.8 mm
[0.031 in]

> 500
See para. 6.3
for calc.

0.0025 mm
/volt

0.005 mm
/volt

0.025 mm
/volt

0.00305 mm
/volt

0.00305 mm
/volt

0.00305 mm
/volt

0.00305 mm
/volt

B1 - Internal Conductors
B2 - External Conductors, uncoated, sea level to 3050 m [10,007 feet]
B3 - External Conductors, uncoated, over 3050 m [10,007 feet]
B4 - External Conductors, with permanent polymer coating (any elevation)
A5 - External Conductors, with conformal coating over assembly (any elevation)
A6 - External Component lead/termination, uncoated, sea level to 3050 m [10,007 feet]
A7 - External Component lead termination, with conformal coating (any elevation

Source: IPC-2221B conductor spacing requirements

As PCBs have become even more complex and precisely designed, the minimum trace spacing becomes even more relevant. That is the minimum distance needed for a trace or other components to withstand a specific voltage.

Importance of Both Clearance and Creepage

Clearance and creepage are now more than important safety practices, they’re internationally-required safety standards. Ultimately, both creepage and clearance are used to prevent arcing. Those standards need to be followed regarding high-voltage circuitry, for both safety and functionality, or the PCB and the product it’s in will experience issues.

 

Clearance - Bird’s Eye Distance Between Conductive Parts

The shortest distance in the air between conductive parts is otherwise known as clearance. By measuring the shortest path that doesn’t pass through insulation, parts, or sleeving clearance can then be evaluated. Environmental effects are extremely relevant to clearance, especially when humidity can increase the chance of arcing, as both moisture and humidity could lead to arc flashes. Dust or other small particles can also cause issues between the conductive components.

Creepage - Surface Distance Between Conductive Parts

Similar to clearance, creepage is the same measurement between conductive parts except they must be along the surface of some kind of insulation. They also have similar requirements and concerns with the only difference being the insulation of the creepage instead of the air that clearance passes through

the difference between creepage and clearance

The only difference in these is regarding the surface along which the current travels, with creepage going through an insulated surface while clearance passes through air. When factoring in the individual specifications clearance and creepage distance are typically very similar. The only instance where there would be a difference is concerning high-voltage circuits that may require different clearances and components.

Relevant Safety Standards to Clearance and Creepage

There are several safety regulations that pertain to creepage and clearance. They provide clear direction on how to operate equipment under ideal conditions and temperatures, and detail how to manufacture high-quality equipment and parts in a safe environment.

IPC-2221: Schematic and Material Selection for Thermal Management

The standards laid out in IPC-2221 detail numerous requirements designed to prevent issues related to overheating and thermal management. They ensure that a proper trace width is calculated to keep the relevant temperature below their thresholds. This is a widely accepted standard that not only lays out best practices but also the ideal materials.

IPC-9592: Standardization of Power Conversion Devices (PCDs)

Relevant to power conversion, this dictates the safety standards specifically for PCDs. By creating a standard power for computers and other communication devices this creates a safety net by which PCB creators can analyze their spacing requirements based on voltage and whether it’s an external or internal layer.

UL 61010: Standards for Electrical Requirements and Other Hazards

This safety standard regards the appropriate distances for clearance and creepage for laboratory and industrial equipment. For equipment used for measuring, and controlling processes like pH controllers or temperature, poorly measured distances pose a massive risk. Suggested measurements are laid out in BS EN 61010-1:2010 standards (Safety requirements for electrical equipment for measurement, control, and laboratory use - General requirements), including those found in the table that follows.

Clearances and Creepage Distances for Mains Circuits of
Overvoltage Category II up to 300 V

Voltage
line-to-
neutral
a.c. r.m.s.
or d.c.
Values
for
CLEAR-
ANCE
Values for CREEPAGE DISTANCE
Printed wiring
board material
Other insulating material
Pollution
DEGREE 1
Pollution
DEGREE 2
Pollution
DEGREE 1
Pollution
DEGREE 2
Pollution
DEGREE 3
All material
groups
Material
group I,
II, IIIa
All material
groups
Material
group I
Material
group II
Material
group III
Material
group I
Material
group II
Material
group III

V

mm

mm

mm

mm

mm

mm

mm

mm

mm

mm

≤150

0.5

0.5

0.5

0.5

0.8

1.1

1.6

2.0

2.2

2.5

>150≤300

1.5

1.5

1.5

1.5

1.5

2.1

3.0

3.8

4.1

4.7

EN 61010 safety standard: clearances and creepage distances for mains circuits of overvoltage category II up to 300v

Note:

a) The values in Table 4 are for BASIC INSULATION and SUPPLEMENTARY INSULATION. Values for REINFORCED INSULATION shall be twice the values for BASIC INSULATION.

b) Minimum CLEARANCE for BASIC INSULATION, SUPPLEMENTARY INSULATION and REINFORCED INSULATION for POLLUTION DEGREE 3 is 0.8 mm.

c) If the equipment is RATED to operate at an altitude greater than 2,000 m, the CLEARANCES need to be multiplied by the factors found in Table 3 of the standards document.

Maintaining these standards isn’t just important, it leads to increased functionality and longer use for the components and the PCB itself. However, this doesn’t address or solve every potential issue with creepage or clearance.

Avoiding Clearance and Creepage Concerns

Calculating the necessary clearance and creepage is just the first step in a complicated process. Temperature, air pollution, moisture, humidity, and voltage are all different variables that will affect the PCB. These are a short set of guidelines to help avoid concerns and issues when determining creepage and clearance specifics.

  1. Constantly monitor spacing between any traces and other components.
  2. Maintain the “3W principle,” where the spacing between lines must be no less than 3 times the width of the line itself.
  3. Determine where high voltage will occur and ensure spaces and distances are larger to prevent issues like arcing.
  4. Use insulation when necessary, but especially when there is a connection between high and low-voltage components.
  5. Use curves and not angles to utilize the shortest possible trace lengths.

Optimal Materials and Circuits

For high-voltage PCBs and connections, more will be required of the PCB materials and components. They’ll be more susceptible to voltage fluctuations, exposure to different environments and humidities, and potential overvoltage as the product degrades over time. That’s why it’s incredibly important to use circuits that are specifically recommended and designed for clearance and creepage.

High Voltage

High-voltage circuits that operate at a minimum of 50V will need longer distances for both clearance and creepage to prevent electrical issues and breakdowns. Read more about RF PCBs here on our website.

Medical Devices

Medical devices often have more failsafes than other industrial equipment. Both kinds of distances need to be strictly adhered to and specified because of the importance and significance of the devices. Components, use, and interaction with patients are all factors for clearance and creepage in medical equipment.

Industrial Equipment

OSHA and other governing bodies have put strict specifications on industrial equipment and devices that need to be adhered to, especially those that account for particulates like dust, heat, and vibration/movement.

Power Electronics

The higher the voltage and power of a device the higher the risk is of problems. When dealing with high currents and voltage, longer clearance and creepage distances are typically required to avoid issues with arcing, insulation, and voltage faults.

 
For materials, every component needs to be carefully selected. High operating voltages will be a factor, so not only does there need to be accurate spacing, but 2oz minimum traces or vias of copper and resin and glass levels are known to provide the durability and reliability required for those high-voltage projects and products.

PCB Practices and Standards

Standards and practices are becoming more unique and more specific to the job or project they’re used for, and that’s only going to continue as technology continues to evolve. While hobby PCB creation is fun and fulfilling, many professional PCBs are used from modern industrial tools to life-saving devices. That’s why precise line spacing is such an important and meticulous detail.

Maintain these practices and utilize these materials and you’re one step closer to stable, high-voltage PCBs.

Get your PCBs Built-Fast.

Contact us for a PCB quote
or call us at 1-800-SFC-5143

Via Tenting Principles in PCB Layouts

PCB School

Via Tenting Principles in PCB Layouts

Via tenting is the application of soldermask to encase or seal the via’s opening. A via is essentially a hole drilled into the PCB that facilitates connections between multiple PCB layers. An untented via, on the other hand, remains uncovered by a soldermask layer. The decision to expose or cover these vias carries both advantages and disadvantages contingent upon your specific design and manufacturing requirements.

Read More

PCB Assembly Drawings: Polarities, Pin1 & Anode/Cathode Markings

PCB School

PCB Assembly Drawings: Polarities, Pin1 & Anode/Cathode Markings

The Essential Guide to PCB Assembly Drawings: Understanding Polarities, Pin1 Marking & Anode/Cathode Markings. Learn more about understanding the XY File, component locations, & polarized component orientations.

Read More

PCB Insertion Loss

PCB School

PCB Insertion Loss

This article explores insertion loss: its properties, how loss occurs throughout a signal path in a system, and things we can do to minimize it.

Read More

PCB Dimensional & Thermal Stability

PCB School

PCB Dimensional & Thermal Stability

There are a number of factors to consider with the mechanical aspects of a PCB. In this article, we are going to dive into the various ways a PCB designer can help to deliver a board meeting mechanical and thermal requirements while staying competitive on cost.

Unnecessarily tight constraints on the board will be a cost driver. Meanwhile, an insufficient set of physical parameters leaves the potential for a board that does not meet the necessary requirements in the field.

One's goal is to find the sweet spot between precision and price. Believe it or not, that is possible to do.

Read More

How Do You Manage Copper Pads, Copper Traces, & Planes in High-Load Applications?

PCB School

How Do You Manage Copper Pads, Copper Traces, & Planes in High-Load Applications?

At what point is a load considered high voltage or high current, and what does that mean for the PCB design process? There are several factors that must be considered when specifying components and laying out a PCB for these kinds of conditions. Here's what you need to know to properly manage copper pads, copper traces, an copper planes.

Read More

Serpentine Routing–Function Over Form in PCB Routing

PCB School

Serpentine Routing–Function Over Form in PCB Routing

Is Serpentine Routing a good choice for your next PCB project? Signal integrity is very important in digital and analog systems. The routing of your PCB plays an important role in helping to increase performance by keeping signals in sync. A few minor disasters in your routing can lead to a major disaster. Learn more about why serpentine routing may be the right choice for you.

Read More

San Francisco Circuits, Inc.

1660 S Amphlett Blvd #200
San Mateo,CA 94402
Toll-Free: (800)732-5143
E-mail: sales@sfcircuits.com

 NIST LogoITAR Compliance Seal  IPC International, Inc. Membership Seal SAM

San Francisco Circuits - San Diego

3914 Murphy Canyon Rd., Suite A244
San Diego, CA 92123
Local: (858)576-7202

Follow us

Twitter Logo Facebook Logo LinkedIn Logo

©Copyright 2005 - 2024 - San Francisco Circuits, Inc. - All rights reserved

Latest News

06-10-2024

PCB Line Spacing: A Comprehensive Breakdown for High Voltage Applications. As PCBs become more complicated, more precise measurements and spacing are required. This article explains PCB line spacing, tracing, clearance, and creepage.

Read more

02-21-2024

Via tenting is the application of soldermask to encase or seal the via’s opening. A via is essentially a hole drilled into the PCB that facilitates connections between multiple PCB layers. An untented via, on the other hand, remains uncovered by a soldermask layer. The decision to expose or cover these vias carries both advantages and disadvantages contingent upon your specific design and manufacturing requirements.

Read more

User Login