Before answering these questions, we first need to understand what PCB thickness is.
PCB thickness refers to the thickness after the board is completed.
The nominal thickness of copper clad laminate is 0.5, 0.7, 0.8, 1.0, 1.2, 1.5, 1.6, 2.0, 2.4, 3.2, 6.4 mm.
The nominal thickness of paper-based copper-clad laminates is from 0.7 to 1.5 mm.
Not very clear about the PCB thickness still?
Let's get started for more details.
Part 1: The Standard PCB Copper Thickness
When we talk about thickness in copper in the realization of printed circuits, we mean the thickness of the tracks and the pads, whether they are internal or external to the layers.
PCB copper thickness is generally divided into 1oz (35µm), 2oz (70µm), 3oz (105µm). Of course, the copper thickness depends on what kind of board you make. The copper thickness for switching power supply with the high current is 2oz. For the signal transfer, generally, 1oz of thickness is enough. Below are the details.
- The normal double panel is 1oz.
- Multilayer board inner layer is generally 1/2oz 1/3oz outer layer 1oz 1/2oz 1/3oz.
- The power supply board's copper thickness is higher.
70% of the circuit board uses 35µm copper foil thickness, which mainly depends on the purpose of the PCB and the size of the signal voltage and current. In addition, for the PCB that requires excessive current, some parts will use 70µm copper thickness and 105µm copper thickness.
In addition, there are 12µm used for ultra-high-density patterns such as build-up boards for thin ones, and 105µm used for high current patterns for thick ones. Thicker copper foil is also used on boards that carry large currents.
Part 2: Why is the PCB Copper Thickness Unit in Ounces?
You may be still wondering.
The PCB copper thickness is usually expressed in oz (ounces).
The PCB copper thickness on the PCB board is determined by the weight of the unit area.
Here 1oz copper thickness refers to 1oz of copper covering the area of 1 square foot uniformly. It is about 1.4mil.
Here is the format.
1 ounce = 28.3495 grams
The thickness of the commonly used circuit board copper foil is usually:
- 18 μm
- 35 µm
- 55 µm
- 70 µm
A convenient table of PCB copper thickness is as follows:
- half oz = 0.68 mils = 17.5μm
- 1oz = 1.37 mils = 35μm
- 2oz = 2.74 mils = 70μm
- 3oz = 4.11 mils = 105μm
Generally, the PCB copper thickness of single-sided and double-sided PCB copper foil is about 35µm (1.4mil). And the other specifications are 50µm and 70 µm. The thickness of the surface layer of the multilayer board is generally 35µm=1oz (1.4mil), the inner layer is 17.5 µm (0.7mil).
Part 3: More Details about PCB Copper Thickness
Let's get back to the PCB copper thickness.
The greater the weight of copper, the better the electrical properties of the board. But the more difficult it becomes to etch the board.
To enable batch production of boards, make sure the minimum pattern width/pattern spacing meets the following specifications.
PCB copper thickness
Minimum pattern width/pattern interval
at least 4/4mil
at least 10/10mil
at least 15/15mil
PCB copper thickness
Minimum pattern width/pattern interval (for offline estimation)
at least 3.5/3.5mil
at least 6/8mil
at least 7/12mil
Part 4: Other Factors Affecting PCB Thickness
PCB Core Thickness
The substrate, otherwise also called dielectric, or the core is the insulating material that separates two conductor layers. The core is a copper-clad material, which hardly changes its thickness during the manufacturing process of the circuit board.
In a two-layer printed circuit, there will therefore be a central substrate in the middle of two copper layers usually called TOP and BOTTOM.
The standard thickness of the substrate is 1.6 mm, both for two-layer circuits and for 4/6 layer multilayers. However, in general, the greater the number of layers, the thicker the printed circuit board, due to the minimum thickness of the layers.
In the layer structure of a printed circuit board, there are always 2 to 3 prepregs (glass fiber fabric filled with resin) between 2 cores with their copper cladding. They are pressed together with the cores.
Unlike the core, the prepreg changes its effective thickness during pressing. The thickness is therefore dependent on the PCB manufacturer, the setting of its processes, and the ratio of areas covered with copper and open spaces.
Internal Layers PCB Thickness
In addition to the sequence of the layers, the real customization of the stack-up consists of the definition of the internal PCB thicknesses. And in particular of the vertical distance between the floors on which the copper tracks are placed.
It is important to clarify immediately that there is no complete freedom on the values of the internal thicknesses. Because in reality, these thicknesses are the result of a specific construction sequence of the printed circuit. In the sense to obtain a certain configuration of thicknesses, it must be built with a certain structure.
Part 5: Standard PCB Thickness
Printed circuit boards have JIS, JPCA, IPC/JPCA, UL, and other standards, and the materials and PCB thickness vary depending on the standard.
The PCB thickness is not only the thickness of the board itself but also the thickness of the copper foil part, the thickness of the plated part, etc. It varies depending on the material of the printed circuit board.
The standard PCB thickness is:
- 6.40mm, etc.
Then, what is the standard thickness of the 2-layer PCB?
2 layer PCB thickness standard thickness is 1.6mm. Our expectation is that the PCB fab has some copper clad cores, and the total thickness of copper and FR4 material is equal to 1.6mm.
Here comes a question.
Can the PCB copper thickness be controlled on the software?
There is no such operation in a conventional way, the thickness is not increased by software, and it is customized to the manufacturer. The thickness is required to explain it to the manufacturer.
If you want to control the copper thickness of the PCB board, just write the requirements clearly and let the manufacturer make the copper thickness according to your requirements. You just need to talk to the board manufacturer.