The Best High Current PCB Design Tips

October 9, 2019 , in Blog, Industrial

I guess it would be safe to call the town where I grew up a factory town. In fact, some of the world’s largest manufacturers were based there and you would be hard-pressed to find anyone who has not worked in an industrial environment at one time or another. I am sure that knowing a lot of people around the country and the world depend on your work was a source of pride for many of us who did work in factories and it is still for those who do so today. Even today, I can still remember the hum of the machines and recall how much safety was stressed.

High current factory equipment

High current PCB applications in industry

The reason safety is so important in many factories is the high power machinery, which can be dangerous. The primary danger is interacting with the high currents that are required to power and control industrial equipment. Many facilities utilize alarms and electronic indicators according to a defined safety integrity level (SIL) to protect against potential electrical hazards. However, the responsibility for electrical system safety rests to a great extent on the electronics and PCBs that convert, regulate, distribute and utilize high currents. To ensure that your boards contribute to a safe industrial environment there are high current PCB design tips that you should follow. Let’s see what these are and why they are important. But first, let’s take a more in-depth look at the high current PCB attributes that make them attractive for industry.

High Current PCBs in Industrial Environments

In 2009, the IPC-2152 Standard for Determining Current-carrying Capacity in Printed Board Design was released. This standard for relating trace width, copper weight and current carrying capacity replaced the long-standing and still often used the IPC-2221A standard. Based upon the guidelines of these standards, attempts to develop a reliable means of determining these parameters for high current PCBs have been made culminating in a number of on-line trace-width calculators, such as DigiKey, to assist developers and board designers. Although these tools are not standardized, they can be quite helpful in designing PCBs that are capable of meeting their current capacity requirements.

Most circuit boards process or transfer low power signals for digital, RF or power circuitry. For these applications, copper weights of 1oz or 2oz carrying currents in the mA to tens of amps range are typically sufficient. For some industries, such as military and aerospace, medical systems, automotive and industrial production, PCBs must have traces that are capable of carrying hundreds or thousands of amps. For these boards, trace widths must be much wider or copper weights must be higher.

The typical approach to high current demands is to widen relatively thin (≤ 2oz) copper traces, which requires additional space on the surface and layers. However, the use of heavy or extreme copper routing has distinct advantages over that approach, including the following:

Advantages of Heavy or Extreme Current PCB Routing

  • Greater trace current carry capacity
  • Greater via current carrying capacity
  • Accommodation of different circuit current levels on the same layer or PDN
  • Does not require increased trace widths
  • High reliability
  • Good mechanical strength at connectors
  • Utilization of high-temperature components without risk

To realize these advantages does require special high current PCB design considerations that will affect your contract manufacturer’s (CM) manufacturing process.

The High Current PCB Design Tips You Should Know

Designing high current PCBs is not the same as for typical low power electronics boards and neither is the manufacturing process. For example, board layers may contain several copper sheets and cycles of plating and etching may be required. These increased cycles can render some board material types unusable, such as FR4 that has shown a 32% failure rate after eight cycles for 0.8 mil - 1.2 mil copper plated boards. However, by following the high current PCB design tips listed below you should realize a board that is reliable and meets your industrial PCB development requirements.

HIGH CURRENT PCB DESIGN TIPS

Tip

Why it is Important

Use a high current trace calculator.Your design should be based on high current rules and not those typical for lower weights.
Include protection circuitry.As your traces are carrying higher currents, the amount of damage to components and the board is greater.
Select the best board materials.Work with your CM to choose the best base copper weight. Lower weights allow for denser designs. Copper and dielectrics should be selected based on the coefficient of thermal expansion (CTE).
Avoid very small drill hole sizes.Small drill holes can lead to debris being left in holes, which can be hazardous when high currents are used and may result in via damage or spark into a fire.
Use larger diameter annular rings and oversized clearances.This provides area for drill landing as drills will be required to penetrate thick copper sheets.
Use multiple PTHs.Mechanical strength can be improved by using multiple PTHs instead of a single very wide via to handle current carrying requirement.
Analyze board for good thermal distribution.Perform a thermal analysis to make sure that your board distributes heat well to assist with PCBA.
Analyze board for good thermal dissipation.Analyze your board to ensure there are no hot spots (concentrations of excessive heat).
Tempo‘s Industry 4.0 Custom PCB Manufacturing Services
  • ISO-9001, IPC-600 and IPC-610 commitment to quality certifications.
  • Agile manufacturing process to support risk management.
  • Accurate quote in less than a day.
  • DFM support from Day 1 of design.
  • Entire turnkey PCB manufacturing in as fast as 3 days.
  • High precision, complex PCB fabrication and assembly capabilities.
  • Sources components from the most reputable suppliers in the industry to reduce procurement time and help with component security.
  • Specialization in fast prototyping and low-volume production.
  • Standard quality testing; including X-ray and inline AOI.
  • Advanced QC testing; including flying probe, time domain reflectometry and ROSE.

Today’s industrial environment is increasingly incorporating new technologies, such as Industry 4.0 strategies and techniques that are changing the development requirements for circuit boards. Many of these advancements require high power PCBs, which expand the process of PCB manufacturing. In order to meet these, your CM must possess the capabilities to build these special boards. At Tempo Automation, we possess the expertise, experience and advanced facilities to build your high power and other industrial PCBs quickly and to the highest quality.

And to help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.

If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on the high current PCB design tips that should be incorporated for your industrial PCBs, contact us.

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