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The Ultimate Guide to PCB Thickness
So, what is the standard thickness of a 2-layer PCB? The standard thickness of a 2-layer PCB is 1.6mm. We expect the PCB factory to use some copper-clad core, with the total thickness of copper and FR4 material equaling 1.6mm.
PCB thickness refers to the thickness of the circuit board after completion. The nominal thickness of the copper-clad laminate is 0.5, 0.7, 0.8, 1.0, 1.2, 1.5, 1.6, 2.0, 2.4, 3.2, 6.4mm. The nominal thickness of paper-based copper-clad laminates is 0.7 to 1.5 mm. Not sure about PCB thickness? Don't worry! Let's learn more details.
Part 1: Standard PCB Copper Thickness
When we talk about the thickness of copper in a printed circuit, we are referring to the thickness of the tracks and pads, whether they are located internally or externally on the layers.
PCB copper thickness is generally divided into 1oz (35μm), 2oz (70μm), 3oz (105μm). Of course, the copper thickness depends on the type of board you are making. Switching power supplies use a copper thickness of 2oz for high current, while signal transmission generally only needs 1oz. Details are described below.
Normal double-sided boards are 1oz.
Multilayer boards usually have an inner layer of 1/2oz or 1/3oz and an outer layer of 1oz, 1/2oz, or 1/3oz.
Power boards have a higher copper thickness.
70% of circuit boards use a copper foil thickness of 35μm. This mainly depends on the application of the PCB and the size of the signal voltage and current. In addition, for PCBs that need to pass large currents, some use a copper thickness of 70μm or 105μm.
Part 2: Why is the PCB Copper Thickness Unit in Ounces?
You may still be wondering. PCB copper thickness is usually expressed in oz (ounces). The PCB copper thickness on the PCB is determined by the weight per unit area. Here, a 1oz copper thickness means that 1oz of copper is evenly covered on an area of 1 square foot, which is approximately 1.4mil. The format is as follows: 1 ounce = 28.3495 grams. Commonly used circuit board copper foil thicknesses are usually:
18 μm
35 μm
55 μm
70 μm
Convenient table for PCB copper thickness is as follows:
Half ounce = 0.68 mils = 17.5μm
1 ounce = 1.37 mils = 35μm
2 ounces = 2.74 mils = 70μm
3 ounces = 4.11 mils = 105μm
Generally, the PCB copper thickness of single and double-sided PCBs is around 35μm (1.4mil), other specifications include 50μm, 70μm, and the surface layer thickness of multilayer boards is generally 35μm=1oz (1.4mil), and the inner layer is 17.5μm (0.7mil).
Part 3: More Details on PCB Copper Thickness
Let's go back to the topic of PCB copper thickness. The greater the weight of copper, the better the electrical performance of the circuit board. However, the etching difficulty of the circuit board is also greater.
Part 4: Other Factors Affecting PCB Thickness
PCB core thickness
The substrate, also known as the dielectric or core, is the insulating material that separates the two conductive layers. The core is a copper-clad material, and its thickness hardly changes during the manufacturing process of the circuit board. Therefore, in a double-layer printed circuit, there will be a central substrate between the two copper layers, usually called TOP and BOTTOM. The standard thickness of the substrate is 1.6mm, whether it is a double-layer circuit board or a 4/6-layer multilayer circuit board. However, generally speaking, the more layers, the thicker the printed circuit board, and the fewer layers, the thinner the thickness.
Prepreg thickness
In the layer structure of a printed circuit board, there are usually 2 to 3 prepregs (glass fiber fabric, internally filled with resin) between two copper-clad core boards, and they are pressed together with the core board. Unlike the core board, the prepreg changes its effective thickness during pressing. Therefore, the thickness depends on the PCB manufacturer, its process settings, and the ratio of copper coverage area to open space.
Inner layer PCB thickness
In addition to the order of layers, true customization of the stackup also includes defining the inner PCB thickness. In particular, the vertical distance between the layers where the copper tracks are placed. It must be clarified immediately that the value of the inner thickness does not have complete freedom. Because in practice, these thicknesses are the result of the specific construction sequence of the printed circuit. In a sense, to obtain a specific thickness configuration, a specific structure must be used to construct it.
Part 5: Standard PCB Thickness
Printed circuit boards have standards such as JIS, JPCA, IPC/JPCA, and UL, and the materials and PCB thickness vary depending on the standard. PCB thickness includes not only the thickness of the board itself but also the thickness of the copper foil part, the thickness of the plating part, etc., which varies depending on the material of the printed circuit board.
Standard 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.
So what is the standard thickness of a 2-layer PCB? The standard thickness of a 2-layer PCB is 1.6mm. We expect the PCB factory to have some copper-clad cores, and the total thickness of the copper and FR4 material is equal to 1.6mm.
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