[SOLVED] Capacitance of PADs. An estimation???

[palmeiras]

Hi guys,

What is the expected capacitance of PADs (Planar pads used for bond wire)? For instance, 60 um x 60 um? This value depends on the process, the number of layers, and so on… But when simulating our circuit, it is needed to have estimation before going to the layout. How much would I consider it?

Thanks in advance,

 

[dick_freebird]

Pad construction varies a lot. Even wirebond and bump pads in the same
process, may have different material stacks.

I think you want to draw a cross-section of the pad you are going to use,
and determine the dielectric thickness between the bottom-most plate and
substrate; from there it's pretty straight calculation, it's the physical detail
that is key.

You may find that the ESD protection dominates the capacitance if the pad
is only upper metal layers.

 

[johnjoe]

Hi,

you can assume approx. 60-80fF for one pad to substrate.

Best regards

 

[enjunear]

For a quick estimation, use the parallel plate capacitor equation.
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/pplate.html
\[C=\frac{{\varepsilon}_{r}*{\varepsilon}_{0}*A}{d}\]
where Er = relative permittivity of dielectric, and Eo = 8.854E-12 F/m, A in m^2, d in meters, and C in Farads

 

[palmeiras]

Thanks guys, for all information.

 

[yuchiukit]

thanks，i learn a lot from here