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Auto Router - Skip part of a net
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albs_br 5 years ago
Hi,     I'm having a problem and can't find a satisfatory solution: I need to put decoupling capacitors as close as possible to the respective IC. I can route it manually and let the Auto Route do the rest, but there is no way to ignore just these tracks, only the whole VCC and GND nets. I would not want to route manually all the VCC and GND nets, just the connections between these capacitors and the VCC/GND pins of the ICs. The issue can be ssen in this project (public): [https://easyeda\.com/editor\#id=e10ed52966554c5d9040af2ad9bc523e\|1fce3159a76f46c9ab0e82f0adebe7c5\|6ff0859f7afd4b4690d09f2a2a8a5092\|28231774315641c088df6f349df1db8e\|5cbb1df4d5cd42d88d282e1706a7b9e1\|21357cff8a51414da2e01ab8b7f39d3c](https://easyeda.com/editor#id=e10ed52966554c5d9040af2ad9bc523e|1fce3159a76f46c9ab0e82f0adebe7c5|6ff0859f7afd4b4690d09f2a2a8a5092|28231774315641c088df6f349df1db8e|5cbb1df4d5cd42d88d282e1706a7b9e1|21357cff8a51414da2e01ab8b7f39d3c) For example the C1 and U1. Any idea?
Comments
UserSupport 5 years ago
Hi You can autoroute them all and then modify the tracks what's you want.
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albs_br 5 years ago
That's not possible, because there will be many tracks in the way. I tried it many times.
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dillon 5 years ago
![image.png](//image.easyeda.com/pullimage/xtQPAIMU009dVFBvP6gVlr5DSwwgxkI5S3exwsP5.png) Can this work?
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albs_br 5 years ago
It doesn't work. It ignores all the VCC/GND nets, not only the tracks previously traced.
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UserSupport 5 years ago
We don't provide ignore only the tracks, it must ignore the nets.
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albs_br 5 years ago
At first sight I think I have found a solution: simply use 4 layers instead of 2, then use layers exclusive for VCC/GND. But... the price then rises from US$ 2 to 32, a bit expensive for a hobby project (the USD/BRL exchange rate doesn't help either). Apparently, by changing VCC/GND track width to 0.4mm instead of 0.8 the layout became far less "crowded". I will do the decoupling tracks routing manually after Auto Route do his job as sugested ealier. Thanks for all help.
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andyfierman 5 years ago
@albs_br, "...by changing VCC/GND track width to 0.4mm instead of 0.8 the layout became far less "crowded". I will do the decoupling tracks routing manually after Auto Route..." Beware reducing VVC/GND track widths at the expense of signal routing track widths. A low impedance VCC/GND supply network with adequate decoupling (capacitors across devices) is vital for the reliable operation of any electronic - especially digital - circuitry. See the notes on Power and Signal Integrity in (2.2) in: [https://easyeda\.com/andyfierman/Welcome\_to\_EasyEDA\-31e1288f882e49e582699b8eb7fe9b1f](https://easyeda.com/andyfierman/Welcome_to_EasyEDA-31e1288f882e49e582699b8eb7fe9b1f) :)
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albs_br 5 years ago
Thanks for info. Very useful information in your profile too. I used [this](https://www.4pcb.com/trace-width-calculator.html) site to calc track width: ![image.png](//image.easyeda.com/pullimage/TobtBY1z0qf3v19IOSmlSniqbRje6bFGz5hW3T11.png) This result doesn't looks right, such this thin track would be possible to handle 1 A?
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andyfierman 5 years ago
@albs_br, The track widths are too narrow because you have set the wrong value for "Thickness". The "Thickness" refers to the copper not the overall PCB substrate.
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andyfierman 5 years ago
You might like to check the copper thickness for different copper weights here: [http://www.daycounter.com/LabBook/PCB-Copper-Thickness.phtml](http://www.daycounter.com/LabBook/PCB-Copper-Thickness.phtml)
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albs_br 5 years ago
@andyfierman OMG! You are right. What a shame! Using the 1.7 mils of thickness results in value of 0.243 mm for Power tracks width able to 1A currents, which looks adequate since i'm using tracks of 0.4mm and my project uses only currently 200mA, and in future 500mA. Thanks for your help
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