FreeLists / si-list / [SI-LIST] Re: Input Impedance Changing

[steve weir <weirsi@xxxxxxxxxx>]

Yang, you need to put the specific geometry through a 3D solver.  In 
addition, you need to plan the path from the die pads through the 
package to the PCB launch as well.  It's pretty easy at these 
frequencies to create discontinuities that will ruin your 
sensitivity.  OTOH if you are careful and manage the impedance all 
the way through the entire path, then you can achieve excellent results.

Good luck.

Steve.
At 09:54 PM 4/6/2006, Yang Rui wrote:
>Hi, ALL,
>
>We had one RFIC with two pads (top layer), the IC works at 2.45 GHz, the
>input impedance was 27+180i. The IC was passivated with Si3NI4 layer
>with thickness 0.3um. The input impedance measurement was done with GS
>probe (The IC does not have global GND). Now we are doing
>post-processing of this IC, one more SiO2 layer (thickness 0.3um) was
>created on top of Si3Ni4 layer, and one more Al redistribution layer was
>deposited on SiO2 layer, the connection to those two pads are brought up
>through two vias. My question is that how much will the input impedance
>change after inserting this metal layer, what will happen if I short one
>via to the Al layer which will be treated as the GND?
>
>Thank you and Regards,
>Yang
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