Choosing the right PCB thickness is vital to ensuring its optimal performance, durability, and other characteristics. It determines the reliability of the end-use product, making it an essential design parameter. This comprehensive guide will help you learn about circuit board layer size and what goes into selecting one for your project.
Understanding PCB Thickness
PCB thickness is the overall size when measured from the outermost layers. It comprises all the different layers that make the typical board, including the following:
- Substrate
- Copper layer
- Solder mask layer
- Silkscreen layer
- Pre-preg layer in multilayer boards
The substrate is the most significant part. It can be any size, from a few to several millimeters. We measure circuit board thickness using a micrometer, calipers, or advanced techniques involving lasers and clever optics.
Resource: https://www.researchgate.net
What is Standard PCB Thickness?
The standard PCB board thickness is 1.57 mm. We call the board extra thick if the value is higher and, if it is less, a thin board. Other sizes circuit board manufacturers use include those listed below.
- 0.023″
- 0.031″
- 0.047″
- 0.093″
You now understand what circuit board thickness means and the standard range. The following section delves into the significance of this board size or its impact on its performance.
Resource: https://www.researchgate.net
How PCB Thickness Impacts Design and Performance
Layer size has a profound impact on various aspects of the circuit board. It affects its electrical performance, mechanical strength, and thermal efficiency or performance.
Electrical Performance
Proper size determines how well the board handles current, signals, and other characteristics. Higher-power boards are thicker to increase the current-carrying capacity. On the other hand, lower-power devices or systems can be thin. Electrical performance also includes impedance requirements achieved by varying trace sizes.
Mechanical Strength
Thicker circuit boards are studier and less likely to bend or warp. They also resist vibrations better and allow secure connections, making them more reliable in harsher environments. On the other hand, a PCB will fracture if it is too thin.
Thermal Efficiency
Thicker PCBs dissipate heat more quickly. They are also usually designed with more copper weight. The copper conducts more heat, preventing overheating problems. However, a thicker dielectric can cause heat conduction challenges and reduced board efficiency and performance.
Resource: https://www.researchgate.net
Factors Affecting PCB Thickness
Various factors determine how thick or thin a PCB is. They include the type of material you use, the size of individual layers, the number of layers, the amount of copper used, and application needs or requirements.
Material Type
Different materials allow varying board sizes. For instance, the standard FR4 PCB thickness lies between 0.4 mm and 1.6 mm. Other materials may be thinner than this or thicker, depending on the required thermal, mechanical, and other characteristics. For instance, CEM-1 allows 0.25 mm to 1.0 mm and CEM-3 0.4 mm to 1.0 mm.
Layer Thickness
As discussed earlier, the typical circuit board consists of several layers of different materials. The layers determine the board size, including the pre-preg or dielectric materials between the various stack-up layers.
Number of Layers
As the number of layers increases, so does its thickness. Their number can range from 2 to 32 or higher. As you can see, that gives rise to different sizes, with the single layer type having the standard size of 1.57 mm.
Copper Weight
The amount of copper used on the board also affects its size. The copper layer is usually 0.1 mm to 0.2 mm millimeters, indicated as ounces for every square foot, or simply Oz, ranging from 0.5 to 2.0 Oz. (One ounce = 35 microns).
We typically use thicker copper layers when making high-power boards and vice versa. It improves its thermal performance, given the increased heat conductivity.
Application Requirements
The board’s application dictates its thickness. That’s because operation conditions are different. For instance, you need it thicker to withstand heat or mechanical stress. A thinner PCB may suffice if the application is mild or requires a flexible board. Here are some recommendations by industry and application:
- Thin PCB below 0.6 mm: portable communication gadgets, robotics, wearable devices, and drones.
- Medium PCBs 0.6 mm-1.6 mm: general electronics, including computers and home appliances.
- Thick PCBs above 1.6 mm: extreme applications, such as aerospace, automotive, military, and industrial systems.
Resource: https://www.youtube.com/watch?Ukc_kc5OAhw
Choosing the Right Thickness for Your PCB
Always base your choice on the end-product needs. A thinner size is advisable for portable devices requiring reduced size and weight or high-frequency applications where signal integrity is paramount. You also need it thin if making a flexible circuit board.
A thicker PCB is better for a harsh environment like an automotive or industrial application or if the application involves high currents. These uses subject the board to intense vibrations and higher heat levels.
It’s also crucial to ensure your PCB design doesn’t affect the manufacturing process or budget. For instance, thicker boards have better mechanical and thermal characteristics. However, they are more challenging to etch or drill. They also cost more.
On the other hand, the PCB is fragile if too thin and more likely to break during manufacturing or use. It’s, therefore, advisable to balance between the two extremes and only go for what suits both sides.
PCB Thickness Tolerance
Tolerance is the allowable deviation from the nominal thickness, usually expressed as a percentage of the given value by industry standards. It varies widely, depending on the stack-up layers and material. The following recommendations are IPC guidelines. They outline variation by the number of layers.
- ± 10% for less than six layers
- ± 8% for seven to fourteen layers
- ± 6% for fourteen layers and higher
It’s also good to note that a tight clearance complicates a board’s manufacturing process. It can also lead to increased costs. Clients must, therefore, closely work with their suppliers to understand the implications of thickness and tolerance needs.
Conclusion
PCB thickness plays a crucial role in its performance and durability, making it an essential consideration when designing one. Depending on your project’s requirements, you may choose a thin or thick. For most needs, 1.57 to 1.6 mm is an ideal size. Specialized PCBs can be lower or higher than this value.
