What are the Features of ¼ oz Copper PCB?

Copper is a common material used in PCB fabrication. The thickness of this material varies in PCB. Most times, the application requirements will determine the thickness of the copper. Ounces (oz) refer to the units of measure for the thickness of copper in a PCB. We can only determine the thickness of a copper when it is measured. PCBs feature various copper thicknesses. In this article, we will discuss the ¼ oz copper thickness.

What is ¼ oz copper PCB?

The ¼ oz copper PCB is a circuit board that features ¼ oz copper thickness. Generally, 1 oz copper thickness is 1.37 mils. Therefore, ¼ oz copper thickness in a board is 0.34 mil. Also, ¼ copper PCB can mean 0.25 oz copper. ¼ copper can be available on internal layers.

Generally, manufacturers should distribute copper evenly throughout the PCB design. This shouldn’t only be about the copper thickness on each layer, but also across the layer. Furthermore, the overall thickness of a circuit board depends on the number of layers it has.

Not all applications require a thick copper PCB. Therefore, the thickness varies. The typical thickness range for both the prepreg and the core is between 0.008-0.240 inches. Copper impacts the overall PCB thickness. The current passing through the circuit board determines the copper thickness.

¼ oz copper is the thickness you get when ¼ ounce of copper is flattened out to one square foot. ¼ ounce copper thickness is 0.34 mils. In microns, it is 8.5 while resistance per square is 2.0 mOhms. The copper weight per sq.f of ¼ oz copper PCB amounts to ¼ ounces.

The standard thickness of copper is roughly between 1.4mm to 2.8mm for the internal layers. The external layers are between 2 and 3 oz. However, the manufacturer can adjust the copper thickness based on your requirements. Also, it is important to understand that increased copper can be a challenging processing.


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How to Specify the Thickness of a PCB

The thickness of a circuit is mostly determined by copper thickness. A thicker PCB is less likely to break. It is advisable to use a ¼ oz copper PCB when an application calls for it. When choosing copper thickness, you should consider the following.


Boards featuring ¼ oz copper thickness are thick copper PCBs. Thin boards are more flexible than thick PCBs.


It is very crucial to match the PCB thickness to the impedance. Furthermore, the thickness of a PCB determines the thickness of the dielectric. The dielectric helps to ensure impedance control. Therefore, ¼ oz copper PCB features a thick dielectric.

Space required

Larger copper PCBs are ideal for devices having larger space. However, if your device is small, it will be ideal you use a thin copper PCB. Therefore, a PCB featuring ¼ oz copper thickness is ideal for large devices.


Thinner boards can easily break. It is advisable you go for them only when an application requires it.

Components and connections

The components and connection used will determine the board’s thickness.

How Thick is ¼ oz Copper PCB?

1 0z is the standard copper thickness. However, how thick can ¼ oz copper PCB be?

In PCB manufacturing, 1 oz of copper is 1.37 mils, ½ oz is 0.685 mils, while ¼ oz is 0.3425 mil. The thicker the copper in a PCB, the more the cost of manufacturing it. Boards featuring ¼ oz copper thickness will cost less to manufacture.

Apart from the increase in the cost of material, it is more difficult to work with larger copper. Also, working with larger amounts of copper can be time-consuming. This process always involves pressing the copper into an even layer over a square foot area of the PCB. As regards the spacing amount between copper structures, more spacing is better.

The minimum copper thickness for inner layers of ¼ oz PCB is 7, 70µm (absolute minimum acc. IPC-4562). The maximum reduction in production is 2, 00 µm. The minimum finished thickness class 1& 2 is 5, 70µm.


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What is the Resistance Per Square of ¼ oz Copper PCB?

The resistance per square refers to the edge-to-edge sheet resistance of a ¼ square area of copper weight. It is ideal for calculating the DC resistance of the trace of a PCB.

For instance, a trace that is 10 mils wide and 10,000 mils long comprise 1000 squares. With each 10 mils x 10 mils. If the trace is ¼ oz copper, the DC resistance would be 500 squares x 0.5 mOhns/square= 2 Ohm.

Benefits of ¼ oz Copper PCB

PCBs that feature ¼ oz copper thickness offer a lot of benefits. They provide a reliable solution to quality performance in complex circuits.


¼ oz copper PCB is compatible with high-end complex electric circuits. This circuit board can function under a wider range of temperatures. Therefore, it offers extreme functionality.

High power density

¼ oz copper boards can deliver high power density in electronic devices. These boards can manage the required power in a circuit board.

High decomposition temperature

¼ oz copper PCB offers a great thermal sensitivity. This is because it has a higher value of decomposition temperature.

High tolerance

This PCB features a high tolerance to thermal issues. It can maintain consistency in different thermal states. Therefore, it offers great dimensional stability while still maintaining great performance.


This is one of the greatest benefits of ¼ oz PCB. The more the thickness of copper in a PCB, the more expensive it is. Boards with thicker copper take more time and effort to produce. ¼ oz copper PCBs don’t cost too much to fabricate. This PCB is the cheapest board to fabricate.

Applications of ¼ oz Copper PCB

This type of copper PCB is ideal for use in some applications like:

  • Wireless technology
  • Medical devices
  • Military projects
  • Telecommunication industry
  • Complex electric circuits
  • Automobile industries


¼ oz copper PCBs are very ideal for use in some applications. Manufacturers will prefer this board since they cost less to fabricate. Also, ¼ oz PCB features several benefits.

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