PC Board Stackups

We put together a collection of Printed Circuit Board Layer Stackups we recommend when designing your circuit board. We find these to be the most cost effective constructions.The models illustrated range from 2 circuit layers up to 18. We can provide up to 30 layer builds as needed.

 

The stackup models show measurement thicknesses post lamination process. Copper Plating thickness is added to the stack measurement to make up the final overall thickness.

The Copper plating step is necessary to metalize the drilled holes after through-hole drilling. This process adds an additional ~0.001″ to each of the outer layer foils, or ~.002″ total to the stack height.

See below the tables to learn a little more about stackups and lamination process.

Standard Material “Core” Thicknesses

ThicknessTolerance ±Type
0.0030″± 0.0007″Thin Core
0.0040″± 0.0007″Thin Core
0.0050″± 0.0010″Thin Core
0.0060”± 0.0010″Thin Core
0.0075”± 0.0015”Thin Core
0.0080”± 0.0015”Thin Core
0.0100”± 0.0015”Thin Core
0.0120”± 0.0015”Thin Core
0.0140”± 0.0020”Thin Core
0.0210”± 0.0020”Rigid Core
0.0280”± 0.0020”Rigid Core
0.0470”± 0.0030”Rigid Core
0.0590”± 0.0030”Rigid Core

Prepreg Glass Styles (single ply)

Prepreg Style% ResinThickness Range
010676%0.0015-0.0020″
108066%0.0025-0.0035″
211359%0.0035-0.0045″
211656%0.0045-0.0055″
165251%0.0055-0.0065″
762845%0.0075-0.0080″

Copper Weights and Thickness

Cu Weight (oz)Thickness (inches)Thickness (mils)
1/4 (0.25)0.00035″0.35
1/8 (0.375)0.00053″0.53
1/2 (0.5)0.0007″0.7
1.00.00140″1.4
2.00.00280″2.8
3.0*0.00420″4.2
4.0*0.00560″5.6
6.0*0.00840″8.4
8.0*0.01120″11.2

* Considered heavy copper and may require a non-standard stackup

Understanding the printed circuit board fabrication process.

Circuit patterns are printed and wet etched into layers of Copper Clad Laminate. The laminate is made up of thin sheets of copper foil pressed to both sides of epoxy glass cured resin called FR4. Think of a sandwich where the 2 slices of bread is the copper foil and the filling inside is the epoxy FR4.

A typical 2-Layer PCB, or Double-Sided PCB, will consist of one single piece of Copper Clad Laminate, where as a Multi-Layer PCB (PCB greater than 2 circuit layers) consists of more than one piece of laminate. The individual piece of cured laminate is typically called a Core.

A double-sided board is made up of one core and multi-layer boards are constructed with as many cores as needed to achieve the desired number circuit layers. A sheet of Copper foil is typically added to top bottom sides of the layer stack to increase the number of circuit layers.

Outer layer foils and inner layer cores are bonded together using semi-cured FR4, called Prepreg. Prepreg is used to bond the rigid cores together and bond the outer layer sheets of foil to the cores. Once contracted the stack is placed in a lamination press where heat and pressure are applied over time to cure the entire lamination stack.

Balancing the lamination stackup.

Equally important to managing layer thicknesses is constructing a well balanced stackup. A good balanced stackup will use equal cores thicknesses and pair up plane and signal circuit layers to help balance weights throughout the stack.

The top half of the stackup should essentially mirror the lower half. If you were to take the middle of the stack and fold in half both sides should match up. Or be close to matching up.

Size matters.

Increasing more circuit layers to the design doesn’t necessarily mean the board thickness will increase in height. In fact, by using thinner cores and less prepreg we can control the overall thickness.

For example, a 4-layer design may use less copper layers but by adding more prepreg with thicker cores we can maintain a nominal thickness. Alternatively, a 10-layer design can be constructed using thinner cores with less prepreg. Both of these examples show how we can control the stackups to help stay within the industry standard of printed circuit board thicknesses:

  • .0625″
  • .0938″