There are pretty factors of the PCB manufacturing process. However, the PCB thickness is one of the most important factors of the whole process. The thickness affects its conductivity and resistance, significant considerations that have to match your PCB requirements. Typically, the PCB thickness has a significant role in its functionality.
1、Standard PCB Thickness
When we say Standard, we are talking about the first PCBs that were simple in design with a single sided board that had various layers stacked. It refers to the arrangement of single or multiple cores connected with sheets of cured epoxy.
Generally, with PCB thickness, the application or usage area determines how thick the board will be. It is essential during manufacturing of your board; you communicate your specifications like what thickness you would like with your manufacturer.
The thickness ranges from 0.008 inches to 0.240 inches, there are thin Layer PCBs, but the standard or industrial standard PCB thickness is 0.063inches. There is the historical explanation for that specific size, in the beginning; with the development of Circuit Boards which were made of Bakelite sheets.
In the past, Bakelite was thin insulating material that is a good, sturdy insulator that used to be produced in mass numbers of 0.063 inches thickness then were bought and cut to any other specification based on the electronic device.
The thickness became an essential part of the circuit board when multiple layer Electronic boards started to emerge. With the multiple layers, the need for a mode of connection between layers was evident, and copper was used for that on the plate edges.
The thickness of the connectors between the boards had to match, and that became the standard PCB THICKNESS.
1.1 PCB Board Thickness
The board thickness is always based on both the insulating material and the top layer material; at the beginning of Circuit boards, this would be Bakelite sheet included as the top layer of the plywood at the end the total thickness of the board would lead to 0.065inches.
Apparently, better substrate like epoxy (fiberglass) with a copper foil bonded on each side or Paper reinforced phenolic resin with a bonded copper foil have been found, making Bakelite plywood almost extinct, with the new lighter materials coupled with the fact that edge connectors are not in use anymore, the thickness sometimes is lesser than the standard 0.065inches.
The PCB created is determined by its size and thickness with most electronic components, devices, and platforms being having a standard PCB thickness.
1.2 PCB Copper Thickness
You might think how much of a difference does the copper thickness make and the answer is a lot, as the copper thickness determines the PCBs range of application and functionality.
The Copper thickness plays a vital role on how you select a PCB thickness with the copper thickness measured in ounce per area square foot.
Usually, the Printed Circuit Board is around 1 oz with 1.4 mm to 2.8mm thickness for the internal layer, at the end; the finished weight would be about 2 oz to 3oz which can be adjusted based on your preference.
1.3 PCB Trace Thickness
When you talking about Trace thickness of a PCB board, you are talking about the preferable thickness decided by the designer during the design process, the most used trace thickness ranges from 0.008 inches to 0.240 inches with particular attention paid to 0.2 mm (0.0079 inch), 0.4 mm (0.016 inch), 0.5 mm (0.020 inch), 0.6 mm (0.024 inch), 0.8 mm (0.032 inch), 1.0 mm (0.04 inch), 1.2 mm (0.047 inch), 1.5 mm (0.062 inch), 1.6 mm (0.063 inch), 2.0 mm (0.079 inch), 2.3 mm (0.091 inch), etc. when designing Multiple layer boards of 4 or more layers, the user can choose ½, 1 or 2 ounce inner layer copper foil for his board.
In fact, PCB trace thickness calculators are available to the designers to calculate the thickness of the PCB board immediately. In case of wrongly calculating the PCB trace thickness, this may result in either not gaining the accurate results that the PCB designed for or it may also result in damaging the components attached to the surface of the PCB board.
2、Standard PCB Thickness Fr-4
By now, I am sure you have heard a lot about FR-4 (Flame Retardant 4), FR-4 or FR4 is the first material on the shelf when a rigid circuit Board is needed.
FR4 which also stands for a rating, it is the fiberglass reinforced epoxy-laminated sheets common found in PCB manufacturing. The name also is the base quality rating of the epoxy laminate sheets.
While FR4 has as many as four different materials, the primary material is fiberglass woven into a thin cloth sheet. This gives the low structural stability then it is cover and wrapped with a flame resistant epoxy resin that adds its rigidity (one of its primary quality).
All these qualities make FR4 the first choice for High-Quality, Low-Cost PCBs manufacturing. During manufacturing, the FR4 is joined with one or more layers on both sides of Copper foil using adhesive and heat.
The customer product at the end comes with the copper forming the circuit then they are etched out before the solder mask layer and silkscreen are prepared on the board.
As with every other aspect of a circuit board, the FR4 standard PCB thickness is measured in inches or mm depending on the preference of the designer or manufacturer.
But with the commonness of the FR4 substrate, the thickness of the board tends to go the extremes, you can get from ten thou to three inches.
Sometimes a thin layer is needed and/or best suited for a device, but you are not sure how a small board would take the load, so you go for the standard PCB thickness.
With these extremities, several factors are looked out during the PCBs board design, which includes the following:
• Component Compatibility: we have been talking about how FR4 can be used for any and every PCB. But the fact is The thickness of a board will always affect the components compatibility, this holds true with through-hole components while most components have small board thicknesses.
• Design Requirements: Manufacturers tend to go thicker because there are more downsides to thinner boards on PCBs. With FR4, thinner boards are prone to fractures especially when they are too large and can’t have grooves feature. However, thicker boards do both with flying colors, so you always have to put the weighing options into consideration
• Flexibility: Yes when you have thinner boards, you get a degree of flexibility which is a good thing in some situations or applications like the ECU (Electronic Control Unit) in your Automotive use or in the medical field where you continuously encounter stress and flex to the PCBs.
But at the same time, can be a negative in PCB manufacturing, especially in later processes when the soldering machine wants to solder.
The flexible board might bend during the soldering process causing the components to be soldered at a wrong angle, and also the components and connections can break off the board due to the board’s flexibility.
• Space: you always need to consider space as a factor when designing a PCB especially when you manufacturing small devices like USB connectors and Bluetooth Accessories. Thinner boards are preferred when you need space always.
• Impedance Matching: the thickness of board matters in the case of multilayer boards because the layers are used as capacitors on adjacent layers, and the thickness of the FR4 equals the dielectric thickness and in turn changes the capacitances value.
It is more exact in high-frequency PCBs like your ‘microwave, because without impedance matching. Adequate board functionality is almost zero so there is a crucial need for the capacitance on each layer to be just right.