With the growing technology in today’s world, every day we are introduced to the latest electronic gadgets in the consumer market, automotive field, and commercial industrial applications. Every device consists of a functional black box. This black box is called a Printed Circuit Board (PCB) as we know it. Without the circuit board, it is not possible to make even the smallest machine operational. In order to manufacture and fabricate this circuit board we have to look at various parameters that affect the reliability of PCB, which in turn affects the product performance.
In this guide we will walk through one of the crucial parameters when PCBs get fabricated, the standard PCB thickness. We will learn about the importance of common PCB thickness. We will gain knowledge about factors affecting PCB thickness which designers should keep in mind when selecting circuit board thickness for specific projects.
What is The Standard PCB Thickness?
Standard PCB thickness in simpler terms, is the dimension of the printed circuit board which influences the project performance. Usually, it is a common trend in industry that we have adopted 1.57mm (0.062 in) as the standard PCB board thickness, which is a commonly used standard circuit board thickness in a 2-6 layer circuit board.
Please note that a 1.57mm value (common PCB thickness) is not the only option that is available with the fabrication suppliers. We have other thicknesses also available in the market which play an important role as the product to meet different design and usage requirements, such as as 0.8mm, 1mm, 1.57mm, 2mm, and more than 2mm. To satisfy the different requirements, the PCB manufacturers are willing to offer a selection of common PCB thickness alternatives.
Benefits of Standard PCB Thickness
Standard circuit board thickness is a combination of prepreg, copper layers, and solder masks. Based on the technical requirement of the project each thickness impacts directly to quality performance of thermal dissipation, physical stress, impedance control, EMI noise issues, signal integrity, and other characteristics that define the lifecycle of a circuit board.
- A standard PCB board thickness of 1.57 mm is ideal for most applications because it offers acceptable signal transmission and avoids signal loss and distortion.
- There are multiple advantages associated with 1.57mm (typical PCB thickness), such as ease of availability, ease of manufacturability, and affordable cost.
- Standard PCB thickness can ensure the compatibility of circuit board components and systems.
Key Components that Contribute Standard PCB Board Thickness
Standard PCB board thickness consists of three major components: Core, Copper foil, and Prepeg. PCB is fabricated based on the dielectric constant value, copper weight, and masking weight.
Core: It is the substrate of the PCB on which other layers are glued like epoxy. Some of the common core materials are FR4 and polyimide. Based on the type of PCBs rigid or flex we select the substrate core to match the project performance, which affects typical PCB thickness.
Copper foil: It is responsible for the conduction of traces on the layout. The more copper layer weight on the substrate the more PCB can withstand heat dissipation. It directly impacts standard PCB board thickness. Copper thickness has an essential role in achieving the standard circuit board thickness.
Prepreg: It is like an adhesive in between the copper foil and an insulation layer (core).
Other than Copper foil, PCB substrate, and Prepeg. The masking layer and surface finish also add to the overall thickness of the board. All the layers in the PCB structure together are called Layer Stackup. Layer stack-up is different for each PCB. We can define the number of layers choose the value of the dielectric constant, and select the inner and outer layers based on the complexity of the design. Stackup can easily be defined in the CAD tool the designer is using while exporting the schematic to a blank PCB board. It is the first step after the board outline is defined.
Factors That Impact PCB Board Thickness
We can design a multilayer board that can be 2,4,6,8,10, and more layers.1.57mm standard circuit board thickness is not suitable for all types of projects. The number of layers increases due to component density, mixed signals, and space constraints. We should take care of various other factors that support computing PCB thickness. This helps contribute to the complete project performance of mechanical and electrical behavior patterns.
- Heat Management
Making circuit boards with typical PCB thickness can be tricky when it comes to releasing heat. In high-end design where we are dealing with high voltage and high currents either DC or AC. Thermal dissipation should be effectively taken care of otherwise the lifetime of a product gets damaged. Just like we add heat sinks to semi-conductor active components like MOSFET or IGBTs, to manage the heat transfer, similarly if we add thickness to the board by increasing PCB structure core values, we influence and support the heat transfer thereby enhancing the lifetime of a product. It helps to avoid thermal runaway of the board.
- Number of Components
Standard circuit board thickness has to be changed to other available options. The reason is to balance the number of components a board has to be placed with. When we work on the high-frequency boards which are the main control boards of the design. Eventually, we deal with a lot of parts more than 100,200. The thin size of the board will be lightweight and it will not be able to handle the weight of components. If the circuit has SMT parts and Through-hole parts, it is better to increase the size of the board thickness.
- Signal Reflection
It is a major parameter to be considered during the design phase. Select PCB thickness when the project working is complex in nature. For the high-speed boards USB, HDMI, and Processors are a part of the design signal attenuation and noise immunity are the biggest players that get affected by board thickness, We can use a tool to calculate the exact thickness that is required to handle differential pairing other there will be cases of impedance mismatching.
- Surface Finish
During the fabrication steps of the PCB, we enhance the quality of the solder and make it look smooth. We dip the PCB in molten solder and flat it out. There are different types of surface finish available like HASL, ENIG, and Soft Gold. Each type of surface finish contributes a little bit to PCB thickness. if the project has a strict PCB thickness tolerance then there are many manufacturers which provide this service.
- Operational Vicinity
Some of the designs are built for room-temperature environments. While others have to handle the harsh external weather which could be extreme wind, dust, cold, pressure, and humidity. For robust conditions, we should avoid the thin size of boards that can not withstand. To suffice high currents, trace width is also a factor that predicts voltage drop and resistance in the layout.
- Types of Holes
There are various kinds of hole types stacked via, blind via, buried via, plated through holes (PTH, NPTH), and micro vias. When we design a multilayer board, to connect the inner and outer layers we use different types of drilling mechanical and laser drilling.Based on the type of drilling required to manufacture the vias it is important to decide the correct thickness of the PCB.
- Copper Weight
Copper layer plating is done on the PCB. It is measured in ounces. Copper thickness is based on the power requirement of the design. The thicker the copper layer the better advantage the board will have to carry high current and withstand thermal heat. We can use the calculators online to help us decide which thickness on should choose to handle the power budgeting of the product. Commonly 1 to 2oz copper thickness is used.
- Manufacturing Limits
We should effectively communicate with the fabrication house. We should check thoroughly what is the minimum and maximum thickness available beforehand, and if the quality of the board will be good enough or not. Otherwise, if the board tolerances are not strict, the depanelization of the board will be difficult with varying thicknesses. Same for the holes drilling we should check about the machinery.
Conclusion
We have understood the typical PCB thickness and factors impacting thickness from the article. We should use the knowledge and apply it to select the correct typical PCB thickness to avoid any electrical, mechanical, thermal, or manufacturing issues specific to the design.
