[SI-LIST] How many bond-wires to make a good PDS?

  • From: "Graham Kus" <nemisonic@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Mon, 3 Dec 2007 14:02:36 -0500

Hi everyone,
So I have a question. When designing a power supply distribution system
(PDS) for an FBGA bond-wire ASIC package, how many bond-wires are "enough?"
I understand that 25um(1 mil) diameter bond-wires can accommodate almost 1
Amp at DC, but I suspect this is completely off base when driving a bus with
one of these.

The background on my situation involves DDR-2 drivers, and having enough
bond-wires to prevent SSO. This IC package is an FBGA, 4 layer substrate
board. The IP vendor supplied pin-based RLC charts for a lead-frame type
package (although I have yet to see DDR-2 in a TSSOP). These translate well
to signal routes, but the physics the PDS are different than lead-frame pin
structures.  Also this vendor's numbers for power are based literally on a
"rule of thumb chart," which to me is code for "open your SI tool and double
check." We wrestled them into giving us Spice versions of the buffer under
NDA, so presumably we can simulate this ourselves. Anyhow if you guys have
advice, I could use it.

Thanks in advance,

-Graham


[gmail search terms: bondwire bond-wire wirebond wire-bond]


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