[SI-LIST] Capacitors arrays? worth it or not?

  • From: "jeanpierrepoulin" <JeanPierrePoulin@xxxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Fri, 19 May 2006 16:21:31 -0000

Hi and thanks for reading!

We're building a pda-like device where PCB space is tight.

In our situation (building a low-cost product), total cost of 
production is an important consideration, hence the effort to find a 
good `middle ground' in our choice of high-frequency ceramic 
decoupling caps balancing total cost of production and PCB real-
So far, I understand that 4-capacitor arrays only require a single 
cycle for the pick & place machine =96 thereby reducing costs and 
slightly reducing PCB area =96 but other engineers have mentioned that 
they are much more expensive=85

So far, we're thinking of decoupling this board as follows:
-       Single ceramic caps for ~ 1uF
-       4-Capacitor arrays between 100nF ~ 470nF
-       X2Ys or AVX LICC for 10nF to 100nF
-       (Not sure what to pick between the three for the very 
important ~100nF area)

Any thoughts?


(Board is probably HDI 1+b6+1 with controlled impedance @ 50ohm, 
interplane capacitance as high as possible for important 1V8 voltage 
rail (i.e. alternating 1V8-Gnd copper fills) fastest rise time 
is .75ns (for 266Mhz 1V8 DDR memory to CPU two centimeter away), 
four voltage rails between 1V2 to 3V3)

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