Q: Why curvy PCB traces? - diyAudio
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Old 7th December 2010, 08:05 PM   #1
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Question Q: Why curvy PCB traces?

Hello,

I wonder why there are curvy PCB traces found in OPPO BDP-83 Blu-ray Player PCB as attached. The picture is from http://www.oppodigital.com/blu-ray-b...3_Board_hr.jpg. Actually, I can find similar traces in computer motherboard.

Thanks in advance.
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File Type: jpg curvy-pcb-traces.jpg (855.8 KB, 362 views)
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Old 7th December 2010, 08:16 PM   #2
gruni is offline gruni  Germany
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at those speeds the chips in your player are running at, timing becomes so important, that the traces for data lines must be almost equal in length to prevent phase-shifts
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Old 8th December 2010, 01:05 AM   #3
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Now I notice the SATA connector on the board... What is doing there, I was thinking that only 93 has SATA HDD connection?

Last edited by SoNic_real_one; 8th December 2010 at 01:11 AM.
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Old 8th December 2010, 08:38 AM   #4
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gruni, thanks for the info

Sonic_real_one, I don't own one, so I don't know, sorry.
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Old 8th December 2010, 09:34 AM   #5
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At first I thought the width of the trace varied smoothly. This is to prevent signal reflections from changes in impedance.

But what I see here looks like you have high-speed digital signals going down these traces, and they all need to arrive at the same time. So, if some paths would be shorter than others, you curve them around so they all line up in the end.
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Old 10th December 2010, 06:00 PM   #6
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Naim have been using this type of trace on their PCB's for years.
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Old 10th December 2010, 07:08 PM   #7
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Heavyweight PCB CAD packages can do that automatically: Nets can be tagged / paired as requiring equal path lengths and an 'autorouter' will push and shove other traces out of the way to make the space.

This is often seen with high speed pairs into differential line receivers.
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Old 12th December 2010, 11:40 AM   #8
marce is offline marce  United Kingdom
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Skew control, have a look at the requirements for DDR memory, one of the more critical interfaces on a PCB. It requires a router that can handle high speed designs, you have to enter the max skew as either a time or a length. It cannot usually be done manually as quite often you are matching signals within one group to signals within other groups and then to clocks. To make matters worse, when this is on a board the board quite often has to be impedance matched, so each signal layer has to be closely tied to a ground plane for return currents.
Its most noticable on mother boards between the CPU, interface chips and the DDR sockets.
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Old 12th December 2010, 12:04 PM   #9
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got it. Many thanks.
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Old 12th December 2010, 01:19 PM   #10
SigFire is offline SigFire  Germany
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Not being overly familiar with modern PCB-design (to put it mildly), the pic above got me into asking myself , whether the curvy sections of the traces in post #1 would (also ?) be used as on-PCB inductors.
I found a more revealing sample of this there:
http://www.thel-audioworld.de/module/siebung/stvu.jpg
So could this also be the case with the Oppo-PCB ?

Greez & Thanks

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