Standard for PCB Thickness

Choosing the Right Thickness for Your PCB: Insights from Rush PCB UK

Rush PCB UK makes various types of PCBs for the electronics industry. While determining the standard board thickness, the number of layers in a PCB is the key factor in deciding its actual thickness. As the number of layers in a PCB depends on its design and application, the thickness of the PCB will also vary according to its application. For instance, some applications will need a thicker board, while others may require a thinner one. However, the industry’s standard for the thickness of a PCB is 1.57 mm (0.063 inches).

PCB thickness typically refers to the thickness after the board is completed. This includes the thickness of tracks and pads, whether external to or internal to the layers. Primarily, two things directly influence the thickness of a PCB. These are:

Standard for PCB Thickness

Core Thickness

This is usually available in standard thicknesses of 0.5, 0.7, 0.8, 1.0, 1.2, 1.5, 1.6, 2.0, 2.4, 3.2, 6.4 mm.

Copper Cladding Thickness

This is generally available in standard thicknesses of 1 oz (35 µm), 2 oz (70 µm), 3 oz (105 µm)

A vast majority of circuit boards use the 1 oz (35 µm) thick copper foil. However, this mainly depends on the purpose of the PCB, and the current flowing through the traces. For PCBs that must carry higher amounts of current, some tracks may have 2 oz (70 µm) thickness or even 3 oz (105 µm) copper thickness.

Factors Affecting PCB Thickness

Three factors primarily affect multilayer PCB thickness:

PCB Core Thickness

The PCB core, also known as the dielectric or substrate, is the primary insulating material between two conductor layers. The core is copper-clad, and this remains unchanged in thickness during the PCB fabrication process.

Therefore, a two-layer printed circuit board will have a central core or substrate sandwiched between two copper foil layers.

The standard thickness of a substrate is usually 1.6 mm, for 2-, 4-, and 6-layer PCBs. As the number of layers increases, the board becomes thicker, as each layer adds a minimum thickness.

Prepreg Thickness

The layer structure of a printed circuit board may have 2 copper-clad cores separated with 2 to 3 prepregs. These are glass fiber fabric with resin impregnation. The fabrication process presses the prepreg layers with the cores.

While the cores do not change their thickness while undergoing pressing, the prepregs do change their effective thickness. The PCB manufacturer, therefore, decides the final thickness with the setting of their processes.

Internal PCB Layer Thickness

Apart from the sequencing of layers, the manufacturer actually customizes the stack-up with the internal PCB layer thickness. This is the vertical distance between the layers on which the copper tracks lie.

However, PCB manufacturers do not have complete freedom on adjusting the internal thicknesses. In reality, these thicknesses depend on the specific construction sequence the manufacturer decides for the printed circuit board. They may decide to use a certain structure to achieve a certain configuration of thicknesses.

Newest Standard PCB Thickness

Rush PCB UK makes printed circuit boards conforming to JIS, IPC/JPCA, UL, and other standards. The materials and the thickness of the PCB, therefore, vary depending on the standard the PCB must follow.

In actual practice, the PCB thickness, apart from the thickness of the board, also includes the thickness of the copper foils, both in the external and internal layers, the thickness of the plating, the thickness of the solder mask, etc. The overall thickness, therefore, depends on the materials the manufacturer is using for fabricating the printed circuit board.

The newest standard for PCB thickness is: 0.70 mm, 0.80 mm, 0.95 mm, 1.00 mm, 1.27 mm, 1.50 mm, 1.60 mm, 2.00 mm, 2.40 mm, 3.00 mm, 3.20 mm, 3.50 mm, 4.00 mm, 6.40 mm, etc.

Conclusion

Where earlier, the standard PCB thickness was 1.57 mm or 0.062 inches, with modern-day PCBs it has changed to 1.6 mm or 0.0629 inches. However, Rush PCB UK makes PCBs thinner than or thicker than the standard thickness also, depending on the requirement based on the PCB’s application.