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Faisal

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Posts: 90

package modeling?
May 11^th, 2006, 8:48am

Hi,

I have a switched capacitor design, for which I would like to evaluate different packages (comparing electrical characteristics). I looked at different package datasheets and they do not provide information such as bonding wire and/or trace inductance.

So lets say if I arbitarily choose CLDCC (Ceramic Leaded Chip Carrier), how can I obtain such information.. to model the package parsastics in my simulation

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Paul

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Posts: 351
Switzerland

Re: package modeling?
Reply #1 - May 11^th, 2006, 1:48pm

Hi Faisal,

try to get in touch with your packaging subcontractor. The parasitics not only depend on the package itself, but also on the type of bond wire they use (especially for the inductance). If your employer is an important customer you will of course get these informations much more easily Wink

Having a look at the datasheets of commercial products also helps to get an idea of what package is good for this or that application. The frequency of operation of your circuit should also help to find out whether you may be sensitive to package parasitics or not.

Paul

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bernd

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Posts: 229
Munich/Germany

Re: package modeling?
Reply #2 - May 12^th, 2006, 1:19am

Just as a hint!
SpectreRF comes with a standalone package modeling tool called PKG.
It outputs a subcircuit of the modeled package which you can use for
simulation.

Type 'pkg' in your terminal and you will see it, assumed you have
a Spectre RF licenses.

Also documented in:
'Virtuoso SpectreRF Simulation Option User Guide',
Chapter 8 'Modeling RF IC Packages'.

I personally have no experience with this tool!

Bernd

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Just another lonesome cad guy

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sheldon

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Posts: 751

Re: package modeling?
Reply #3 - May 12^th, 2006, 6:19pm

Faisal,

First, it been a while since I have done this so my information
may be out out date. Bond wire inductance varies based on die
size and the bonding diagram so it would be difficult to include
this information in a generic package datasheet. For the same
reasons board trace parastics are specific to your board design
and the package manaufacturer can not know your board's
parasitics, a priori.

1) SpectreRF's packaging tool is useful but it does not support
many package types.

2) The rule of thumb for hand calculating inductance is 1nH per
mil of bond wire length for 1 mil diameter Au bond wire.

3) There are also tools for estimating the effect of board parasitics,
such as, mtline and lmg.

4) Of course, if somebody is actually assembling the parts for you,
then they can probably provide the parasitics[including bond wire and package] based on your pad locations.

Best Regards,

Sheldon

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schehrazi

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Posts: 45
University of CA, LA

Re: package modeling?
Reply #4 - May 25^th, 2006, 2:52pm

For the bond wire, you can assume that the inducatnce is about 1nH/mm lenght of the bond wire. It does not change that much with the diameter of it. This is good for both Aluminum and Gold bond wires.

For the package, the package manufacturers usually don't measure the electrical characteristics of it. You either have to measure it with a probe station or you should simulate it with an electromagnetic field solver. Usually leadless packages work fine up to 1GHz.

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