● About material
● Copper thickness
● Overall thickness
Defining stack-up note is one important step of set-up in PCB design, as it helps the designer describe the manufacturing limitations clearly. If a designer wants a detailed and clear description of stack-up, the following values should be specified:
The material should be included in the designer-specified values for PCB stack-up. Firstly, material types can be chosen from copper or dielectric. When specifying dielectric, please make sure what you want is core or Pre-Preg. All though the material is still undecided, the material tolerances need to be specified. The values can be noted clearly by layers to explain the corresponding tolerance for each layer. For example, both the core and Pre-Preg material should be specified about +/-2-5%. If the copper value is in accordance with dielectric, then a simple +/- value in percentage may be used in a note.
Copper thickness is another designer-specified value for PCB stack-up.The thickness values (finished values)refer to the thickness and thickness tolerance of all layers or each layer. In normal conditions, the cooper thickness most that manufacturers consider is +/-001’’[.0254], but copper plating tolerance is much more difficult to control.
Besides, the third designer-specified value for PCB stack-up is the overall thickness. Additionally, as the total of all the material tolerance, the overall tolerance should also be taken into account and specified clearly. Actually, according to many manufacturers, the overall tolerance of +/-10% is always recommended.