turnaround of metal, poly

[nxing]

Hello everybody,

I have a question regarding turning around the metal and poly in layout. when we change the direction of a line, should we use the 45 degree connection of just 90 degree? Somebody said 45 degree is better, but I don't know why, can anybody tell me?

Thanks

 

[mazelk]

Greetings...

When you design several layers of metal or poly, and you must change the direction, you must use 135 (or 45) degrees. This is better because you must keep soft changes of direction, in order to get a constant impedancie across the line. Applying closest corners (e.g: 90 degrees), the effects of corner difraction get more importance. Also, you must think in construction. Typically, IC factories only can work with this angles.

In order to calculate impedance, sectors above the 145° corner must be multiply its constants by 1/3.

 

[maxwellequ]

Of course that, what mazelk said, is only important at VERY high frequencies. Usually 90º angles are used with no problem.

Usually it is only allowed to have 90 or 45 degree angles (you will get offgrid errors if you use other angles). In some technologies even the 45º connections have more stringent DRC rules (minimum widths for example).

Regards

 

[xinsu]

using 45 degree in wide metal is a guideline in design rule for every process

 

[xinsu]

sorry,I made a mistake in above line.
Using 45 degree should be for all wide wire,not only for metal.

 

[selvaraja]

45 degree turnaround is for high speed signal lines only.

 

[sunny153]

45 degree angles should be there for all wide metals but in high frequency designs, we normally try to use for every wire.

 

[ablue]

round corner may be better, but most processes dont support this. Is that right??