What is an 8-layer PCB good for that a 4-layer PCB can’t do?
Question
Register Now
top10pcb.com is a professional PCB Technical Platform. You can ask questions or post related articles by Registering and Logging In. Please note that if your question or articles are related to ad, they will be deleted.
Answer ( 1 )
Now multi-layer PCBs are used on the motherboard and graphics card, which greatly increases the area that can be wired. Multilayer PCB boards use more single or double-sided wiring boards, and an insulating layer is placed between each board and then laminated. The number of layers of a PCB board represents several independent wiring layers. Usually, the number of layers is even and includes the two outermost layers. Common PCB boards generally have a structure of 4 to 8 layers.
You need to add more layers in the following circumstances:
1.Multiple grounds and power planes (Such as an analog + 15V and -15V) and possible an Analog ground plane different from the digital ground plane to prevent noise coupling.
2.Planes for shielding signals from other signals on adjacent layers.
3.Higher density of traces driven by higher density and lower the size of circuit components, esp ICs with very dense lead packing like QFPs and BGAs. BGAs, in particular, have a very high-density packing of leads and with a given set of design rules, you can only run so many traces between each pin on a layer.
4. A lot of routing has very side busses-32 and 64 bits requiring a lot of areas-can reduce the area by stacking on multiple layers.
5. Random traces crossing back and forth need alternate layers to “jump” over signals going at right angles using vias (feed-throughs).
6. Some traces carrying very high-speed signals require controlled geometry to work well-spacing, width, separation distance from other circuits, length matching, layer distance from a ground plane, etc., so adding layers is sometimes the best way to control these.
How to judge the number of layers of a circuit board by simple observation? Here are a few tips to share with you.
The circuit connection of multi-layer boards is through buried and blind hole technology. Most motherboards and display cards use 4-layer PCB boards, and some use 6, 8 or even 10-layer PCB boards.
–If you want to see how many layers the PCB has, you can identify it by observing the vias, because the 4-layer board used on the motherboard and the graphics card is the first and fourth layers of wiring, and the other layers have other uses (ground) And power). Therefore, like the double-layer board, the guide hole will penetrate the PCB board.
–If some guide holes appear on the front of the PCB but cannot be found on the reverse, then it must be a 6/8 layer board. —If the same guide hole can be found on the front and back of the PCB board, it is naturally a 4-layer board.
Tip: Point the motherboard or graphics card towards the light source. If the position of the guide hole can transmit light, it means a 6 or 8 layer PCB; otherwise, it is a 4 layer PCB.