Need for Heavy Copper

The electronics industry is seeing an escalating demand for heavy copper printed circuit boards powered by new technology. in the automotive, computer, industrial control and MilAero market sectors. What is driving this demand: the continuing increase in power requirements in the medical, industrial and automotive market sectors. That’s the good news. The bad news: this increased demand is creating a supply issue as more than 80% of the existing printed circuit board manufacturing companies are not capable of producing reliable heavy copper printed circuit boards in volume.

How Heavy is Heavy Copper?

Most commercially available printed circuit boards are manufactured for low-voltage/low power applications, using copper traces & planes made up of copper weights ranging from 1/4 oz/ft2 to 3 oz/ft2 on both inner layers and the outer layer finished surface. Heavy copper is then generally defined as anything greater than 3 oz, with some power designs routinely calling for 15 – 20 oz of solid copper. Copper weights above 20 oz/ft2 and up to 200 oz/ft2 are also possible and are often referred to as Extreme Copper. Thermal management is more important than ever in today’s new designs as electronics are used in demanding environments and operate at higher currents. Heavy copper PCBs can help conduct heat away from components so failure is greatly reduced. These heavy copper PCBs conduct electricity better and are more capable of withstanding the increased thermal stress while under power.

 

Top 10 Applications of Heavy Copper PCBs

  1. Power Supplies/Converters
  2. Automotive
    1. Electric vehicle charging stations
  3. Power Distribution
  4. Solar Panels
  5. Power line monitors
  6. Weapons & radar control systems
  7. Traction converters for rail applications
  8. Power grid switching systems & backup
  9. Renewable energies and storage pumping plants
  10. Overload & protection relays

Challenges

 

Heavy Copper Requires Unique Processes

The key to successful heavy copper printed designs is choosing the right PCB manufacturer. Fabricating heavy copper printed circuit boards requires a major change in processing for most manufacturers, and, in some cases, also requires specialized equipment. The obvious challenges are plating and etching as the process guidelines for traditional copper weights can be thrown out the window. Manufacturing with normal etching methods do not work for heavy copper, as they tend to produce uneven edge lines and over-etched trace margins. Fabricators have evolved advanced plating and etching techniques to obtain straight edges and optimally etched margins with processes like high-speed/step plating and differential etching.

Fabrication

  • The etching process is difficult & slow
  • Reduced yields and increased throughput time
  • Increased opportunity for delamination & misregistration
  • Huge amounts of copper need to be removed & disposed of during the etching process
  • Lamination process requires the use of prepregs with very high resin content to incapsulate the heavy copper traces
  • Heavy copper traces on the outer layers makes the surface uneven and it is difficult to print solder mask and legend on the uneven surfaces (may require multiple applications)
  • Coexisting heavy copper traces and standard copper finer lines for digital control is difficult to control

Cost

Copper is expensive, and when talking heavy copper, the cost increase becomes a significant portion of the overall price of the PCB. In the case of extreme copper designs, the cost of copper can be 200X the cost of a traditional PCB! The substrate material of the PCB is another factor that must be considered as a laminate with a very high glass transition temperatures (Tg) may be required to support the power and thermal requirements of the design. Along with Tg, the coefficient of thermal expansion (CTE) between copper and the substrate material must also be considered, as thermal stresses generated by high currents through traces may lead to cracks, layer separation and ultimately PCB failure.

Advantages

The primary benefits of using heavy copper PCBs revolve around thermal management and current carrying capability. The list below is not all-inclusive but provides a snapshot of the variety of benefits that using a heavy copper PCB can provide.

  • Increased endurance to thermal stress & cycling
  • Ability to perform in high temperature operating environments
  • Increased current carrying capacity
  • Increased mechanical strength at connector sites and in PTH holes
  • Utilization of high temperature materials to their full potential without circuit failure
  • Reduced product size by incorporating multiple copper weights on the same layer of circuitry
  • Heavy copper plated vias carry higher current through the board and help to transfer heat to an external heatsink
  • On-board heatsinks directly plated onto the board surface using up to 120-oz copper planes
  • On-board high-power-density planar transformers

Aurora Circuits Heavy Copper Capability

I am proud to say that we have positioned ourselves as one of the very few printed circuit fabricators that can build heavy copper PCBs successfully. We have made this technology a priority and have invested in the equipment and processes required to not only process heavy copper PCBs, but to do so efficiently.

For example, our etching capacity and process are quite unique, where we can control ultra-heavy surface copper with remarkable precision. We are situated like a machine shop, able to process heavy metals – from top layer copper to metal substrates. That makes us quite unique in the PCB world. Many shops have pivoted to high layer counts, flex materials and delicate substrates. Our focus remains in thermal conductivity and the products that benefit from insulated metal substrates and ultra-heavy surface copper.

With the ever increasing thermal and power requirements showing no sign of slowing down, the demand for heavy, and extreme, copper printed circuit boards will certainly follow this trend. Selecting a printed circuit fabricator like Aurora Circuits that routinely produces this technology and has invested in the required processes and equipment is critical to success. Over 800 tons of 6oz and up copper has been processed at Aurora circuits on single sided, double sided and multilayer designs, equaling for 5,000,000 pieces and counting. Our 17 years of experience with this type of fabrication have made us the industry experts.