Different laminates that can be used in the manufacture of your printed circuit board and to make it even easier, here you will see the standard PCB thickness and we gave some tips on when to use each material.
In addition to choosing the material for the board it is very important to pay attention to the difference in the thickness of the laminates. For this, we have recruited our team of experts once again to explain everything you need to know about the thickness of laminates and copper available on the market!
Please see the Parameters of popular cores and prepreg’s:
|Core thickness w/o copper(mm)||Prepreg count and type|
Standard Laminate for Printed Circuit Boards
The thickness of a standard printed circuit board is 0.0629 inches or approximately 1.60 mm. There is a nominal tolerance in this thickness that has a limit of + or – 0.13mm, but in the vast majority of cases the variations verified in practice are much smaller than this nominal tolerance. This thickness, in addition to meeting physical and mechanical needs, in the vast majority of cases also brings great efficiency in terms of insulation and dielectric strength.
Other Laminate Thicknesses
There are several thicknesses of materials available on the market, mainly in fiberglass (FR-4), in the case of Phenolite (FR-1 or FR-2) or Composite (CEM-01) the mechanical factors often make the use impossible of smaller thicknesses.
Impaired by the absorption of moisture and its own composition, phenolite undergoes warping tendencies and greater rupture facility as the thickness is reduced. In addition, other variations due to thermal dissipation and dielectric strength also worsen the performance of thinner plates.
That is why it is not so common to find standard PCB thicknesses below 1.60mm on the market. Even so, there is commercial availability of thicknesses of 1.20mm, 1.00mm and 0.80mm.
Other thicknesses can be achieved with custom manufacturing. However, through minimum batches that generally make the purchase unfeasible, making it more feasible to use fiberglass plates that have a much more varied list of options and are normally available in the retail market .
Due to the wide use of different thicknesses in the manufacture of multilayer printed circuit boards (Multilayer), many FR-4 laminates can be easily found in countless different thicknesses.
In addition to all this diversity, there is still the possibility of manufacturing even more specific thicknesses, through the same pressing processes used in the manufacture of multilayer plates.
There are many situations where slabs of smaller thicknesses can be used in cases where some flexibility of the slab is required.
But only in cases where the card remains static and not in repetitive flexibility movements such as:
- Printer boards
- Flexible keyboards, etc.
In these cases the recommended are polyester or polyamide plates.
Restrictions Imposed by the Printed Circuit Board Design
Despite all this diversity, before opting for the use of alternative thicknesses, it is extremely important to take into account any restrictions imposed by the design of the board.
Limitations such as the proportional reduction of the dielectric constant, in the case of smaller thicknesses, as well as the need for a greater TG (glass transition temperature) in the greater thicknesses, can make seemingly viable options unfeasible.
The Thickness of Copper on Printed Circuit Boards
The thickness of the copper that is pressed to the laminate also varies. When it comes to single-sided printed circuits, it is possible to state that more than 99% of the circuits are manufactured with 1Oz copper (one ounce), which is equivalent to approximately 35 microns.
In specific cases, different thicknesses are used, mainly in circuits with high current points. It is necessary to use 2Oz copper (two ounces) or even more.
Due to the much higher cost of two-ounce copper laminates, it is very common those in generations of the board design. Designers try to thicken the tracks that lead to higher currents as much as possible and often choose not to protect these tracks with the anti-welding mask so that it is possible to reinforce this trail with the application of tin on it during the assembly process.
Although it is not very common to find other variations in the national market with even greater thicknesses of copper, they are part of the manufacturing line of most manufacturers of laminates worldwide, but with purchase on demand with the imposition of minimum lots.
Intermediate Thicknesses of Copper – Dangerous Option
Some laminate manufacturers, in the face of intense competition and looking for lower prices, started to manufacture plates with copper of 0.75Oz (approximately 25 microns) thick, especially in periods when copper had a very high quotation on the international metals exchange.
However, this practice was not well accepted technically by the market, finding adherents only in cases of use in circuits where this layer reduction had no technical impact.
But we do not recommend this option, since during the printed circuit board manufacturing process there will always be some reduction in this thickness, whether in the chemical or mechanical cleaning and pickling processes.
Increased Copper Thickness in Electro Deposition of Layers
The most widely used standard thickness of copper in double-sided laminates is 0.5Oz (approximately 17.5 microns). This copper, which is thinner for this type of printed circuit, has some advantages. It enables a faster and more efficient corrosion process.
Moreover, it provides better definition of the circuit. And whenever a greater copper thickness is required, it can be obtained through the processes electroplating layers that double-sided and multilayer plates are normally subjected to.
Plates with 1Oz copper are also frequently used and nothing prevents them from also having an increased thickness in this same process.
What About Laminates for Printed Circuit Boards?
An ounce is the weight of the copper in 01 square foot.
A foot measures 12 inches, then a square foot measures for example 12 inches x 12 inches, which is approximately 30.5cm x 30.5cm. In order for this copper sheet to weigh an ounce, it must be approximately 35 microns thick, or 0.035 mm.
So when someone says that an ounce equals 35 microns, that information is only true in this case, that is, a square foot of copper that weighs an ounce (28.35 grams) will have a thickness of 35 microns, or if you prefer, a sheet of copper measuring 30.5cm x 30.5cm and 35 microns thick will weigh an ounce.