Comprehensive Knowledge of PCB Copper Thickness

The printed circuit board comprises an insulating segment and electrical conductives. Within this structure, the flow of current transpires along the conductive body to activate the functionality of the components, with the copper layer serving as the conductive medium. Nevertheless, in the exhilaration of engineers’ engagement with novel designs, the finer intricacies concerning the copper layer often get overlooked, including the crucial aspect of PCB copper thickness/weight. Such oversight is evidently inappropriate and necessitates a shift in perspective, aligned with the specific design prerequisites of the circuit board. This TechSparks article will delve into this matter, offering insightful guidance for the necessary transformation.

PCB copper foil

What is PCB Copper Thickness and Why It Matters

Copper thickness typically refers to the thickness of the copper foil layer on the PCB. Copper thickness is commonly measured in “ounces” (oz), but here “ounce” isn’t merely a unit of mass; it also represents the weight of copper per square foot. For instance, 1 ounce of copper thickness means that each square foot of copper weighs 1 ounce, equivalent to approximately 34.8 grams. Consequently, when this layer of copper foil covers an area of 1 square foot, the copper’s thickness is about 0.031 mm. So, why is copper layer thickness in PCB so crucial?

First and foremost, as a high-quality conductive material, copper thickness directly impacts the circuit’s current-carrying capacity. Appropriate copper thickness ensures efficient electrical conductivity in signal transmission and power distribution, mitigating signal loss and voltage drop.

Secondly, in certain high-power applications, devices generate substantial heat during operation. Properly designed copper thickness aids in heat dissipation from the board, thereby preventing component failure.

Moreover, as one of the internal structures of the PCB, the copper layer serves as a structural material, enhancing the circuit board’s mechanical strength and stability.

Additionally, during the PCB manufacturing process, an etching step is necessary to eliminate excess copper foil, forming circuit patterns. Appropriate copper thickness facilitates better control over the entire production process.

Nevertheless, thicker isn’t always better. Increased PCB copper layer thickness raises final production costs and might not necessarily benefit boards with finer line widths and spacing.

How to Choose PCB Copper Thickness

As previously discussed, the copper foil thickness is a variable parameter. Depending on the manufacturer’s technical capabilities and the project’s specific requirements, the standard thickness is often exceeded, reaching levels of up to 20 ounces, thereby leading to the production of thick copper PCB. The use of typical PCB copper thickness is explained below:

1 oz/sq. ft. copper foil weight:

  • Help applications reduce power consumption growth time.
  • Using less copper makes the project more cost-effective, which is extremely beneficial for some projects with low profit margins or limited budgets.
  • Capable of supporting currents of up to 3A for line widths of up to 1/2 inch, serving small to medium power demands.
  • Manufacturing process is relatively straightforward, suitable for general applications.

2 oz/sq ft copper foil weight:

  • Suited for high-power applications, with capacity for elevated current levels.
  • Able to accommodate currents of up to 6A for 1/2 inch line widths, particularly well-suited for high-power requirements.
  • Exhibits low impedance, aiding in preserving signal integrity, especially in high-frequency applications.
  • Offers enhanced performance and signal quality, albeit at a higher cost.

Additional copper weight options, such as 0.5 oz/sq ft and 3 oz/sq ft, exist, although these are less prevalent and typically reserved for specialized design needs. Hence, the selection of the appropriate copper foil thickness necessitates a thoughtful balance of factors including current demand, cost considerations, signal integrity, and application-specific requisites.

ozMilsInchesMillimetersµm
0.50.6850.0006850.017417.37
11.370.001370.034734.79
22.740.002740.069569.58
34.110.004110.1041104.37
45.480.005480.1390138.96
56.850.006850.1735173.75
68.220.008220.2088208.54

Why Heavy Copper

Typically, a standard PCB copper thickness is considered to be 1 ounce or less. On the other hand, when it comes to heavy copper, thicknesses of around 3 ounces and above fall into this category. Although increasing copper thickness raises costs, the popularity of heavy copper remains due to its advantageous features.

  • In certain high-power applications, it is necessary to use heavy copper PCB to enhance the circuit’s current-carrying capacity. This is intricately linked with the trace width on the PCB, where copper foil thickness forms a crucial aspect of trace width calculation.
  • Heavy copper was noted to enhance mechanical structural stability. In modern electronics, due to the complexity of circuit environments, a variety of different types of components are required, including small-scale integrated circuits and larger-volume DIP components. In this scenario, heavy copper is evidently more advantageous for supporting larger components.
  • Applications demanding robust current and thermal management, such as planar transformers and power converters, greatly benefit from the use of heavy copper configurations.

To make informed decisions regarding heavy copper integration, the IPC has developed comprehensive guidelines. These criteria are based on factors like current limitations, required temperature rise, and the interplay between copper thickness and width.

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