Friends - On Wed, Feb 01, 2006 at 01:18:32PM -0500, Stuart Brorson wrote: > > The web page you linked to is not really a stackup. Rather, it is > just a drawing showing where they use prepreg vs. core material.
OK. But it does define the dielectric layer thicknesses. > The usual six layer stackup looks like this: > > ---- sig ---- > > ==== gnd ==== > > ---- sig ---- > > ---- sig ---- > > ==== pwr/gnd ==== > > ---- sig ---- > The above stackup also gives each sig layer a > reference plane next to it. The laminate thickness between the two > inner sig layers should be large. Which is pretty much what I had in mind when I started. 5+5+30+5+5, right? And I consider my collection of eight power supplies as signals, which need to have a high-capacitance low-inductance coupling to the nearby ground. > The layers need to be symmetrical in the vertical direction to > prevent board warpage. I haven't ever seen this effect first-hand. I'll certainly ask the fab house before placing the order. I can always add filler (carefully) on the under-used planes to improve symmetry. > If you Google around, you can find lots of discussion about good > stackups. Here's one: http://www.ce-mag.com/ARG/Grasso.html Good picture, kind of minimal on-topic discussion. > Also, the Howard Johnson book ("High speed digital design, a > handbook of black magic") has a chapter about good stackups. I've heard that book recommended before. Maybe I should get a copy for myself. <clicky-clicky> $78 on Amazon, $40 used at half.com. - Larry
