General high-performance 6-layer board design generally the first and sixth layer of cloth for the formation, the third and fourth floor to take power and ground. Since the dual layer of the microstrip signal line is centered between the power supply layer and the ground layer, the EMI suppression capability is excellent. The drawback of this design is that there are only two layers of the wiring layer. As mentioned earlier, if the outer traces are short and copper is routed in the non-traced area, the same stack can also be achieved with a conventional 6-layer board.
Another 6-layer board layout for the signal, ground, signal, power, ground, signal, which can achieve advanced signal integrity design required environment. The signal layer is adjacent to the ground plane, and the power supply layer and the ground plane are paired. Obviously, the downside is that the layers of the stack are unbalanced.
This usually causes trouble in manufacturing. The solution to the problem is to fill all the blank areas of the third layer of copper, fill copper if the third layer of copper density close to the power layer or ground layer, the board can not be strictly counted as a structural balance of the circuit board The The copper-filled area must be connected to the power supply or grounded. The distance between the connecting vias is still 1/20 wavelength, not necessarily connected everywhere, but ideally should be connected.
Since the insulation isolation layer between the multilayer boards is very thin, the impedance between the circuit board layers of the 10 or 12 layers is very low, and excellent signal integrity is expected to be achieved as long as there is no problem with delamination and stacking. According to the thickness of 62mil manufacturing 12-layer board, the more difficult to be able to process 12-layer board manufacturers are not many.
Since there is always an insulating layer between the signal layer and the circuit layer, it is not optimal to allocate the middle 6-layer signal line in the 10-layer board design. In addition, it is important that the signal layer and the circuit layer are adjacent, that is, the board layout is signal, ground, signal, signal, power, ground, signal, signal, ground, signal.