Electronics > Beginners
Replace trace impedance with resistor?
FriedMule:
--- Quote from: Illusionist on September 01, 2019, 10:25:37 am ---0.8mm thickness is indeed flimsier. Whether it's a problem depends on how it will be treated. The problem is that much flexing is likely to crack solder joints of course, and possibly crack MLCC capacitors which tends to have very unfortunate results.
If the PCBs are fixed into the enclosure such that flexing cannot occur, as mine are, then there's no problem. If that can't be done then 0.8mm is a poor idea and you'll need 1.6mm. In that case, if you can't make the traces wide enough on 2-layer to get down to 50Ω, then the above solution of using some thin coax is a workable one.
--- End quote ---
I do really like your answer:-) So a thick 2 layer board is the best for stability but useless for impedance of 50 Ohm.
I have made a drawing of what I think I understand, top is how it is now, bottom is your suggestion.
Illusionist:
Well it's ArthurDent's suggestion, but I agree with it. Yes, your diagram has the gist of it.
Whether it's better for your design than a 2.88mm wide trace (which is what you need to get 50Ω on a 1.6mm thick 2-layer board)... only you can tell. I had too much going on close by to put such a wide trace in.
I might end up using the coax method on my next PCB because, other than the impedance requirement on multiple tracks, I have no need to go to four layers. It's too big a board and will have a lot of PCB-mount sockets to risk 0.8mm thickness with. I still need to think about the best way to deal with it.
FriedMule:
--- Quote from: Illusionist on September 01, 2019, 01:07:56 pm ---Well it's ArthurDent's suggestion, but I agree with it. Yes, your diagram has the gist of it.
Whether it's better for your design than a 2.88mm wide trace (which is what you need to get 50Ω on a 1.6mm thick 2-layer board)... only you can tell. I had too much going on close by to put such a wide trace in.
I might end up using the coax method on my next PCB because, other than the impedance requirement on multiple tracks, I have no need to go to four layers. It's too big a board and will have a lot of PCB-mount sockets to risk 0.8mm thickness with. I still need to think about the best way to deal with it.
--- End quote ---
Great, so again I can choose between coax, wider track or flimsy board. Since I am thinking of building some sort of shielding around the board, it may be enough to protect the board?
Is it okay to change the subject in this thread? I mean that I hope to build more boards, each in its own shielding enclosure to shield 0Hz-1Ghz. Each fairly close together. Each board has a BNC female plug and I would like to space the boards such that the BNC plugs has a standard spacing in the front panel.
Questions:
Is there any standard BNC spacing on oscilloscopes?
What material should I use to make the enclosure of?
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