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Design >> RF Design >> inductance of the exposed pad bondwire
https://designers-guide.org/forum/YaBB.pl?num=1165242024

Message started by michael_li on Dec 4^th, 2006, 6:20am

Title: inductance of the exposed pad bondwire
Post by michael_li on Dec 4^th, 2006, 6:20am

In my 2000MHz PA Driver circuit design,I use bondwire inductor emitter negative feedback.
To get higher gain,I bond the emitter to the Exposed Pad of the QFN48 package,so the bondwire inductance is estimated 1nH.Is that right,or it should be 500pH?

:-/

Title: Re: inductance of the exposed pad bondwire
Post by ACWWong on Dec 4^th, 2006, 6:50am

It depends on how long it is (and other dimensions) and what the adjacent bondwires are etc. etc.
So 1nH is ok as an approximation for the self inductance of a 1mm length of bondwire. 0.5nH is ok for something like 0.6mm. Depending on adjacent bondwires, mutal inductance can act to change the effective value you use.
You can find references to bondwire inductance formulae in something like Tom Lee's "Design of CMOS Radio Frequency Integrated Circuits"

Title: Re: inductance of the exposed pad bondwire
Post by loose-electron on Dec 4^th, 2006, 9:21am

In addition to the textbook references, electromagnetic model tools (Sonnett, ASITIC, and others) will allow development of an inductance and magentic coupling model.

Manufacturers of the QFN package (popular in RF circles due to low L) also develop more complete package models for their customers.

Jerry

Title: Re: inductance of the exposed pad bondwire
Post by ACWWong on Dec 4^th, 2006, 9:33am

yes best port of call is are your packaging people... as loose says, they normally can give you some model data:

I just googled and found this:
http://www.ose.com.tw/ic/en/packaging_service.asp
but you could also try amkor or unisem...

Title: Re: inductance of the exposed pad bondwire
Post by loose-electron on Dec 4^th, 2006, 1:26pm

Amkor is pretty good at developing package models for their products. Good results seen from them! :)

Title: Re: inductance of the exposed pad bondwire
Post by michael_li on Dec 5^th, 2006, 1:59am

You are so kind.
Thanks all of you.
So I will check it with the package factory.