High Speed PCB Design

Questions relating to designing PCBs

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Williamhawk
Posts: 1
Joined: Thu Oct 26, 2017 6:02 am

High Speed PCB Design

Post by Williamhawk » Wed Nov 01, 2017 2:45 am

Hello Everyone,

I am looking for considerations to keep in mind while designing a pcb(Only double sided available) with high speed signals (upto 100MHz).
What I know up till know:
1)Using small traces to get low inductance and capacitance.
2)Using a complete layer of the two sided pcb as ground plane to act as a decoupling capacitor.
3)Avoid removing any part from the ground layer so that the return current is exactly under the signal current.

Questions:
4) Would using smds be a better option than through hole components and why?
5) If I use smds, I would have to use vias to provide ground is using vias for ground and also other connections a good option?
6)What other techniques can be used to minimize the stray capacitances and inductances at high frequency.
7)What is with the transmission line termination and control impedance?
8)Microstrip:what is it ? In case of double sided pcb with one ground layer and the other etched part is this microstrip?
9)What should I do with the power should it be provided on the etched side?

Please correct me where wrong :) Please try to answer all it would really help me.
Any Idea , Suggestions would be appreciated,

Thanks,

I didn't find the right solution from the internet.

References:https://forum.allaboutcircuits.com/thre ... ign.99571/

installation video

lyndon
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Location: Minnesota, USA

Re: High Speed PCB Design

Post by lyndon » Wed Nov 01, 2017 10:14 am


mattylad
Posts: 230
Joined: Sat Sep 25, 2010 3:49 pm

Re: High Speed PCB Design

Post by mattylad » Sat Nov 11, 2017 3:22 am

4) Would using smds be a better option than through hole components and why?

Less holes through the board so less holes in the groundplane underneath. Smaller components taking up less space.
Cheaper to assemble.
Although connectors are not always as secure as PTH.

5) If I use smds, I would have to use vias to provide ground is using vias for ground and also other connections a good option?
works fine, how else would you connect to the other side of the board :)

9)What should I do with the power should it be provided on the etched side?
It should be provided, which side it goes on depends upon how much of it there is and where it goes to-from.

Omgitskillah
Posts: 9
Joined: Tue Nov 28, 2017 11:33 am

Re: High Speed PCB Design

Post by Omgitskillah » Tue Nov 28, 2017 12:16 pm

Hi Williamhawk ,
I'll try to answer some of your questions.
4. As Mattylad mentioned, SMD parts have very many advantages over through type components. I'd add one more advantage, when you get to high frequencies like you are, using through type components creates tiny pointy stubs on the opposite side of the board, therefore acting as an antenna to emmit or pick up unwanted RF waves.

5. You should use vias to connect the two ground planes on either sides. You should also add random vias all over the board to improve thermal properties of your board.

6. A tip is to avoid having any high speed traces crossing each other on either side of the board. Having more than two planes usually helps by having the plain directly underneath as ground.

7. Impedance matching is very important to avoid losses in the transmission line.

8. Think of microstrips as any trace that transmit microwave frequencies. Your board has only 100MHz tops so you are not within the Microwave range.

9. Make power traces as thick as possible. Preferably 12 to 32 mils wide if you can. Also, avoid having any RF traces passing across the power trace.

All the best!

davidjackson
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Joined: Wed Nov 29, 2017 5:24 am
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Re: High Speed PCB Design

Post by davidjackson » Wed Dec 06, 2017 7:30 am

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markjackson
Posts: 1
Joined: Fri Dec 15, 2017 2:13 am

Re: High Speed PCB Design

Post by markjackson » Fri Dec 15, 2017 2:19 am

Hi,

Ill help you in with so far knowledge I obtained

1. For high-speed boards, plan the stack-up properly, understand your board size, if it's smaller then plan the signal layers and a corresponding number of planes for it. Trace widths, the material used, spacing will help you in having controlled impedance and check for manufacturing feasibility with the vendor.

2. Plan your VIA's that goes to your board, like through holes or blind via's any u need. Note that cost is important so through hole via are cheaper but carefully plan for the stub. What is the frequency of the board. say if it is 1GHz the stub length will affect the performance of the board.

3. Component placement is major part. Understand the thermal flow, air flow of the board for components. Try placing your components so that trace length is maintained minimum and plan for EMI issues at the initial stage itself.

For Any more information related PCB news and update visit - http://xenoa.co.uk/pcb-assembly/

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