Please help me with the wiring problem of the power layer of the four-layer board

吃星星的狼

Please help me with the wiring problem of the power layer of the four-layer board [Copy link]

 

One of the four-layer boards is the power layer. I don’t know which power lines should be placed on the power layer, because the components are on the top or bottom layer. If the power is on the third layer, it will have to be drilled. The filter capacitors of some power lines are not on the same layer as the power lines, and the effect may be worse. So I am very confused now and don’t know which power lines should be placed on the power layer. I need your advice!

秦天qintian0303

In my opinion, the so-called power layer does not mean that all power lines are placed in it. It mainly puts some lines that are easily interfered or too long to be wired in it. Just treat it as a signal layer.

qwqwqw2088

All power supply related information can be placed on the power supply layer

Since the decision to design a four-layer board was made, the product performance must have been considered as a requirement.

Therefore, try to avoid routing signal lines on the power layer.

吃星星的狼

Qintianqintian0303 posted on 2023-5-26 11:47 Personally, the so-called power layer does not mean that all power lines are placed in it, but mainly those that are easily disturbed or too long to be wired are placed in it, ...

Thanks sir

吃星星的狼

qwqwqw2088 posted on 2023-5-26 12:56 All the power supply related information can be placed on the power supply layer. Since the decision to design a four-layer board was made, the product performance must have been considered as a requirement. Therefore, try to...

Boss, if they are all placed on the power layer, then every device that needs power supply must have a hole drilled through it. In this way, for some filter capacitors, will the effect be worse than if the power line is on the same layer?

qwqwqw2088

The wolf who eats stars published on 2023-5-26 13:53 Boss, if they are all placed on the power layer, then not every device that needs to pass the power supply needs to be drilled through the hole, which is not good for some filter capacitors...

Even if you use a double-sided board, you will still have such concerns about vias. You dare not put vias when drawing the whole board.

qwqwqw2088

The wolf who eats stars published on 2023-5-26 13:53 Boss, if they are all placed on the power layer, then not every device that needs to pass the power supply needs to be drilled through the hole, which is not good for some filter capacitors...

The power layer and ground layer of the four layers are arranged in the middle, and both have negative wiring.

If the circuit board is more particular, such as a high-frequency RF board, blind holes and buried holes can be used, but such holes are more expensive, and generally through holes are used.

As for whether the effect of some filter capacitors is worse than that of power lines on the same layer, this requires experimental test data.

Improper device layout, routing method, and capacitor parameters will affect the filtering effect to some extent.

吃星星的狼

qwqwqw2088 posted on 2023-5-26 14:34 The four-layer power layer and ground layer are arranged in the middle, and both have negative film routing. If the circuit board is more particular, such as a high-frequency radio frequency board, you can use...

Got it, thanks sir!

chunyang

The power layer and ground layer of the multi-layer board are not used for routing, but the whole power and ground are connected to the signal layer through vias. Do not route on the power layer and the bottom layer unless it is absolutely necessary, as it will destroy the integrity of the power layer and the bottom layer, resulting in degradation of EMC parameters. When the top and bottom layers of multi-pin, high-density, and micro-component boards cannot meet the wiring requirements, six-layer boards should be used instead of using the middle layer of the four-layer board for routing.

吃星星的狼

chunyang posted on 2023-5-26 17:28 The power layer and ground layer of the multilayer board are not used for routing, but the power and ground of the whole block, connected to the signal layer through vias. Unless it is absolutely necessary, do not use vias on the power layer and...

Thanks, does that mean all power supplies need to be laid on the power layer? Or can power lines also be laid on the top and bottom layers?

chunyang

The wolf who eats stars posted on 2023-5-26 18:17 Thanks, does that mean all power supplies need to be laid on the power layer? Or can power cables be laid on the top and bottom layers?

The signal layer can of course carry power and ground, and even if there is enough space, a large area of ground is often used. If you look at a mobile phone PCB, you will see this phenomenon.

led2015

Is it a principle to place all power lines on the power layer as much as possible?

吃星星的狼

chunyang posted on 2023-5-26 18:59 The signal layer can of course carry power and ground, and even if there is enough space, a large area of ground is often used. Take a look at the mobile phone PCB and you will see this phenomenon.

Good boss

吾妻思萌

You can search for a ZTE PCB manual, which introduces everything from top-level design to component wiring. Divide the power plane and ground plane into large planes first and small planes later, and make the structure symmetrical. There are a lot of expected dry goods.

wangerxian

It is definitely not what you understand. If all power supplies go to the power layer, how many vias should be drilled? In fact, it is unreasonable if you think about it.

hjl2832

Why is the EMC of multi-layer boards better than that of two-layer boards? In fact, we usually talk about power loops and loop interference all day long. If you think about it, you will know that large power layers and ground layers indirectly shorten the area of the power loop (power->load->ground). For the RC behavior added by vias, a short loop path has a better effect.

hjl2832

In fact, when we do hardware testing, we often find that the ripples of the oscilloscope ground wire clamp at different PCB grounding points are different. Why? Because the ground plane itself has ripples. The reason for this is that the power loop path is unreasonable and the ground wire cannot be completely decoupled from the 0 potential balance.

chunyang

wangerxian posted on 2023-5-29 09:15 It is definitely not what you understand. If all power supplies go to the power layer, how many vias should be drilled? In fact, it is unreasonable if you think about it.

Then I suggest you take a look at PC motherboards and mobile phone motherboards, and you will see a lot of things that you think are "unreasonable".

wangerxian

chunyang posted on 2023-5-29 15:50 Then I suggest you take a look at PC motherboards and mobile phone motherboards, and you will see a lot of what you think is "unreasonable".

Then maybe I am still too inexperienced.