9th September 2006 12:05 PM
PCB design in traxmaker
I am designing a PCB using traxmaker.I am putting tracks manually on my PCB.I am just not sure if I am allowed to use 90 degrees turns for the tracks.
Also do I have to use vias and if so,where ?
Thanks a lot.
9th September 2006 10:41 PM
avoiding 90 degree is a good practice, its not critical to use them, but its not recommended, and you will never see them on proffesional PCBs.
10th September 2006 06:28 PM
The reason that a 90 degree bend is not desired is important to understand. When etching copper from a board, chemicals are sprayed or bubbled over the copper to continually flush the area being etched, so there is continuous movement of liquid. The factories that make PCBs fine tune their process so that when the copper completely etches away down to bare substrate the process is stopped at exactly the right time to avoid etching too much copper in underneath the resist along the sides of the traces. This timing is critical. However, the timing to get the perfect edge of a trace allows a slight extra bit of etching on sharp outside corners of copper so these outside corners get over-etched a tiny bit. This becomes a problem when you do board layouts with thin traces, like many professionals do, where the trace width is .008 inches or less. With traces so thin, losing any extra at a 90 degree bend becomes a problem. So the pros have learned to avoid this problem by keeping bends less sharp, for example by using 45 degree bends instead of 90 degree bends.
I think that if you are making your own board and you are using wide traces, like 0.03 inches and such, one doesn't really need to worry about this problem.
The other reason that one would avoid 90 degree bends is when making a high frequency transmission line like microstrip, and intending to carry RF on this line at frequencies above 1 GHz. The reasons to avoid the 90 degree bend are complex, but in simplified form, such a thing typically has the wrong impedance and so degrades the transmission line.
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