PCB Thickness

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May 23, 2018|Technological Advancements and Materials

The thickness of a printed circuit board (PCB) will influence the performance and functionality of the board. Depending on what your requirements are for your PCB, will determine what thickness level best suits you.

But not all PCB’s are the same. Many variables come into play when building a PCB. The thickness of the board is one of those essential variables. When deciding on the level of thickness you need, you must consider not just the function of the PCB, but the profile, weight, assembly components and specifications of the components as well. All of these factors contribute to the overall performance of the PCB as well as the thickness level.

Over the years, printed circuit boards have evolved immensely. As electronic devices shrink in size, so too has the PCBs shrank. That requires the boards to be lightweight and thin to fit inside the device. Because of that, the thickness of a PCB is essential to the board.

Let’s take a look at the different options for thickness, what the standards are and how to determine what level you need.

What are the PCB Thickness Options?

Depending on how many layers your PCB has, that will also determine the thickness level. Sometimes a PCB is better off thicker, while other times a thin PCB is required. So being able to achieve varying amounts of thickness levels is critical to developing the right board for your needs.

Different options are available when combining the core thickness and the prepreg of the board (fibreglass strengthened by an adhesive layer). Typically you will find the range of thickness levels are between 0.008 inches and 0.240 inches.

Standard PCB Thickness

The standard PCB thickness typically falls around 0.063” (1.57 mm). This level goes back to the beginning of PCB in the plywood industry. That was the thickness the sheets of plywood came in that ended up being used as substrates for electronic devices.

PCB Copper Thickness

For standard Copper PCBs, thickness level is roughly 1.4 – 2.8 mils or .035 – .075mm for internal layers. The finished weight would be between 2 oz and 3 oz including the external layers. Depending on your requirements, the thickness can be adjusted.

How to Specify PCB Thickness

By using a trace width calculator, you will be able to specify the thickness of your printed circuit board. By following the steps and imputing all the specifications required on your board, the calculator can help give you an idea as to how thick it should be.

You will need to know factors like the prepreg thickness, the solder mask thickness and what you desire as the final thickness. It can be calculated to hundredths of a millimetre to ensure accurate measurements. Depending on the inner layer thickness, that will affect the overall thickens levels.

How to Choose the Thickness on PCB

When choosing the thickness of your printed circuit board, the thicker you can go typically the better. Thin boards are prone to being brittle and breaking. Unless your device requires a thin board, opt for a thicker finish. Consider the following points when deciding the thickness:

• Weight – the weight of your board is a significant factor. Thinner finishes result in a lighter board.
• Flexibility – a thin board can be flexible. Depending on how flexible the board needs to be, that will determine how thick it should be. Thin, flexible boards are prone to breaking, but too thick of boards can be quite heavy.
• Space – take note of how much space you have to work with. Thin boards take up less space. Typically smaller devices will require smaller boards.
• Connections – the type of connector you need on the board will dictate the level of thickness required.
• Component Compatibility – certain components of the board require a specific thickness level.
• Impedance Matching – the thickness of the board means the thickness of the dielectric. The dielectric is what helps with impedance control. So when the impedance is critical, the thickness of the board is also crucial.