[SI-LIST] Question on Impedance Control
- From: Pat Diao <Pat_Diao@xxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 20 Mar 2003 10:49:18 -0800
I think enough has been discussed about using a 2D solver to determine the
trace W/S and di-e thickness to achieve the desired impedance - single-ended
or differencial.
However, in a real package other than flipchip/CSP, bond wires are needed
for the die to traces connection. As such, no matter how well it is
controlled on the traces, the presence of bond wire will always throw the
impedance off (usually higher).
So here are the questions about how this is handled in practice:
1. Design the traces to the targeted 50 or 100 ohm and ignore the effect of
wires, hoping for the best?
2. Pre-lower the trace impedance in design in anticipating the effect of
wire?
3. Use 3D simulation on the designed wire + trace struction to calculate the
actual impedance?
Feedback appreciated.
Pat
Pat Diao
ASAT
Fremont, CA
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