test please delete

[RichardCranium]

... be buried power planes, i.e. Ground and 5V (or 3.3V). It helps keep the EMI down and makes things more compact...

... Gets very expensive though...

... especially if the components are surface mount (which most are now)...

It brings in all the joys of vias, tented vias, buried vias etc.

And the boards are a pig to test.

Thank you.

That makes more sense.

[RichardCranium]

Belated wavey wave.

[RichardCranium]

There must be more to life than this.... If I was younger I'd sell my bod instead

Anything to break the

Oh, no. Where's this going?

monotony....

That's a relief!

[RichardCranium]

I've got a fiver...

Well done.

How many tricks did you have to do to earn that?

[kali]

"lol"?

Do we do "lol" here?

rotfl


( sawwy )

[zeitghost]

"These days"? I'm not convinced circuits have become bigger and more complex. There are more sophisticated single-package devices than there were so fewer discrete components. Is it just because these days circuit designers don't put the time into circuit design?
"diversity"? Why is that obvious. I can see you need a greater number of tracks, but why should more layers be needed? I still don't get it.

I thought layers were to prevent cross-over wires. 16 layers suggests that principle has been replaced by "oh bugger that, it takes too long. use all the cross overs you want, we'll just bung another layer on each time if need be."

16 layers is nothing really... that's the limitation on this yonks old version of CadStar I'm using... some packages have unlimited numbers of layers...

If you consider a ball grid array, where the balls can be 10 thou apart, it becomes difficult to get the connectivity without more than 2 layers.

Plus, as I said, two (or more) layers are used for power planes... using a layer as a power plane reduces the impedance of the power rails & reduces the amount of tulipe that can emmanate from the board... relatively more important these days... it can make a significant difference to the pass/fail EMI check of a design.

I don't think you could successfully design something like a mobile phone with a two layer pcb any more.

You certainly can't design a card to plug into a pc with two layers anymore... just to get the PCI interface working takes at least 3, and probably 4 layers.

In the case of PCI it's the signal timing on the interface that gets interesting... the design guide stresses the need to get the bus tracks all of equal length to reduce timing skew. Which ain't easy with a square surface mount chip. You also need the power planes in the board to define the impedance of the traces... it gets quite complex really.

[kali]

I've got a fiver...

Just a cup of tea and a snog then....

[zeitghost]

I am "so" bored......

There must be more to life than this.... If I was younger I'd sell my bod instead

Anything to break the monotony....

How much do you charge ?

[zeitghost]

Belated wavey wave.

Almost time to bugger off to catch my train...

[zeitghost]

I seem to have sent the congregation to sleep with my PCB design guide

We could have FORTRAN IV programming for beginners next