Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


David

#12834

Controlled impedance | 22 January, 1999

Could anyone send me equations to calculate controlled impedance of traces on circuit boards. I am most interested in the buried traces in multi layer boards.

Thanks, David - piengr@verinet.com

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Earl Moon

#12835

Re: Controlled impedance | 23 January, 1999

| Could anyone send me equations to calculate controlled impedance of traces on circuit boards. I am most interested in the buried traces in multi layer boards. | | Thanks, | David - piengr@verinet.com | As one of the first MLB impedance folks on the planet (how 'bout that for tooting one's horn (y going back to 1977, wow!). Anyway, I have so much stuff it would take a little time to get it together and a lot longer to ship it to you.

I'll gladly email some of the stripline (buried) stuff to you tomorrow. If you don't need microstrip or burined microstrip, I will negate it from the package. Also, are you planning on differential impedance requirements or simple single trace conductors between two reference planes? Any material preferences etc.?

Earl Moon

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Kallol Chakraborty

#12836

Re: Controlled impedance | 24 January, 1999

| | Could anyone send me equations to calculate controlled impedance of traces on circuit boards. I am most interested in the buried traces in multi layer boards. | | | | Thanks, | | David - piengr@verinet.com | | | As one of the first MLB impedance folks on the planet (how 'bout that for tooting one's horn (y going back to 1977, wow!). Anyway, I have so much stuff it would take a little time to get it together and a lot longer to ship it to you. | | I'll gladly email some of the stripline (buried) stuff to you tomorrow. If you don't need microstrip or burined microstrip, I will negate it from the package. Also, are you planning on differential impedance requirements or simple single trace conductors between two reference planes? Any material preferences etc.? | | Earl Moon | Hi David,

I am pretty sure that Earl would answer most of your question there.

As I recall, I had a very hard time playing with the variables to come up with 5% within the limits over 1.4 GHz design in a 12 layer MLB.

Equations for Microstrip, burried microstrip or stripline are all different . Also it matters how you measure it. IPC -Tm -650 is a good one to follow, whereas in the design phase IPC-D-275 is very helpfull.

This book is very helpfull too in this regards.

"HIGH SPEED DIGITAL DESIGN - A Handbook of Black Magic" - Authors are H. Johnson & M.Graham. ISBN 0-13-395724-1

Also try this website to play with the variables if you like :

http://www.automata.com/tools/imped/imped-ems.html, http://www.automata.com/tools/imped/imped-ms.html

Hope it helps. Regards Kc.

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