Editing Printed circuit board (section)

=== Copper thickness ===
{{MOS|section|[[MOS:CONVERSIONS]]|date=May 2024}}
Copper thickness of PCBs can be specified directly or as the weight of copper per area (in ounce per square foot) which is easier to measure. One [[ounce]] per [[square foot]] is 1.344 mils or 34 micrometers thickness (0.001344 inches). ''Heavy copper'' is a layer exceeding three ounces of copper per ft<sup>2</sup>, or approximately 4.2&nbsp;mils (105&nbsp;μm) (0.0042&nbsp;inches) thick.  Heavy copper layers are used for high current or  to help dissipate heat.{{Citation needed|date=January 2025}}

On the common FR-4 substrates, 1 [[ounce|oz]] copper per ft<sup>2</sup> (35&nbsp;μm) is the most common thickness; 2 oz (70&nbsp;μm) and 0.5 oz (17.5&nbsp;μm) thickness is often an option. Less common are 12 and 105&nbsp;μm, 9&nbsp;μm is sometimes available on some substrates. Flexible substrates typically have thinner metalization. Metal-core boards for high power devices commonly use thicker copper; 35&nbsp;μm is usual but also 140 and 400&nbsp;μm can be encountered.

In the US, copper foil thickness is specified in units of [[ounce]]s per square foot (oz/ft<sup>2</sup>), commonly referred to simply as ''ounce''. Common thicknesses are 1/2&nbsp;oz/ft<sup>2</sup> (150&nbsp;g/m{{sup|2}}), 1&nbsp;oz/ft<sup>2</sup> (300&nbsp;g/m{{sup|2}}), 2&nbsp;oz/ft<sup>2</sup> (600&nbsp;g/m{{sup|2}}), and 3&nbsp;oz/ft<sup>2</sup> (900&nbsp;g/m{{sup|2}}). These work out to thicknesses of 17.05&nbsp;μm (0.67 [[thou (length)|thou]]), 34.1&nbsp;μm (1.34 [[thou (length)|thou]]), 68.2&nbsp;μm (2.68 thou), and 102.3&nbsp;μm (4.02 thou), respectively.

{| class="wikitable"
|-
! oz/ft<sup>2</sup>
! g/m{{sup|2}}
! μm
! [[thou (length)|thou]]
|-
| 1/2&nbsp;oz/ft<sup>2</sup>
| 150&nbsp;g/m{{sup|2}}
| 17.05&nbsp;μm
| 0.67 thou
|-
| 1&nbsp;oz/ft<sup>2</sup>
| 300&nbsp;g/m{{sup|2}}
| 34.1&nbsp;μm
| 1.34 thou
|-
| 2&nbsp;oz/ft<sup>2</sup>
| 600&nbsp;g/m{{sup|2}}
| 68.2&nbsp;μm
| 2.68 thou
|-
| 3&nbsp;oz/ft<sup>2</sup>
| 900&nbsp;g/m{{sup|2}}
| 102.3&nbsp;μm
| 4.02 thou
|}

1/2&nbsp;oz/ft<sup>2</sup> foil is not widely used as a finished copper weight, but is used for outer layers when plating for through holes will increase the finished copper weight Some PCB manufacturers refer to 1&nbsp;oz/ft<sup>2</sup> copper foil as having a thickness of 35&nbsp;μm (may also be referred to as 35&nbsp;μ, 35 [[micron]], or 35 mic).
* 1/0 – denotes 1&nbsp;oz/ft<sup>2</sup> copper one side, with no copper on the other side.
* 1/1 – denotes 1&nbsp;oz/ft<sup>2</sup> copper on both sides.
* H/0 or H/H – denotes 0.5&nbsp;oz/ft<sup>2</sup> copper on one or both sides, respectively.
* 2/0 or 2/2 – denotes 2&nbsp;oz/ft<sup>2</sup> copper on one or both sides, respectively.