Eight Layer PCB - How To Make?
Eight Layer PCB is a stack-up PCB design that has 8 copper layers. One of the major reasons to design an eight Layer PCB is to reduce the electromagnetic interference and improve signal integrity. For this reason, eight-Layer PCB can be approximated to be equivalent to a 6-layer PCB which has better signal integrity. There are different configurations that could be used to make eight-Layer PCB. Whichever configuration used, the PCB Designer should seek to ensure that power and ground planes should be coupled together. The high-speed signals should be sandwiched between the center planes of the eight-Layer PCB. The signal layers should be adjacent to the planes. For better signal integrity, ensure that your eight-Layer PCB has multiple ground planes.
An eight-layer board can be used to add two more routing layers or to improve EMC performance by adding two more planes.
The percentage increase in the cost of an eight-layer board over a six-layer board is less than the percentage increase in going from four to six layers, hence making it easier to justify the cost increase for improved EMC performance. Therefore, most eight-layer boards consist of four wiring layers and four planes.
In general, to make an eight-Layer PCB, you need alternating layers of the copper layer, prepreg, and core. The prepreg acts as a glue that firmly combines the eight-Layer PCB stack-up into a single board. Following the rules to improve the electromagnetic compatibility, a simple eight-Layer PCB configuration would look as shown below. It is important to note that an Eight-Layer PCB is capable of achieving high signal integrity as compared to 6-layer PCB and below.
You can choose the PCB stack-up design method according to the number of signal networks, device density, PIN density, signal frequency, board size, etc. The greater the number of signal networks, the greater the device density, the greater the PIN density, and the higher the signal. Besides, for good EMI performance, it is best to ensure that each signal layer has its own reference layer.