[SI-LIST] Re: Thick vs. thin diff. pairs

Mark,
One plus point for wide traces is that the etching tolerance, +/- 1 mil 
on a 10 mil trace has less effect than +/- 1 mil on a 4 mil trace, same 
goes for the spacing between the pairs.

Dave Instone
Oxford Semiconductor Ltd
25 Milton Park
Abingdon
Oxon ox14 4sh
UK
www.oxsemi.com
+44 (0)1235 824963



Mark Burford wrote:
> Dear all, 
> I would like to ask opinions, on the merits and disadvantages of using
> wide or narrow microstrip lines.
>
> >From where I am sitting it looks like narrow microstrip diff. pairs have
> it won hands down.
>
>  
>
> Thick lines:
>
> More area...which gives more dielectric loss as dielectric loss over
> takes skin effect losses at higher frequencies.
>
> More S11 because any corner on the line will give a greater area and
> more capacitance.
>
> Thicker substrates to keep the impedance at the right value.
>
> As thicker microstrip lines go round a bend, the inter-pair skew will be
> more than for two narrow lines.
>
> There is also the possibility of increased EMI from thicker substrates
> (been reading antenna design books).
>
>  
>
> So please someone tell me why should we use thicker lines? And also
> please could someone tell me the trip ups of HDI (high density
> interconnect) such as how small can one realistically go with back plane
> and inter-chip routing?
>
>  
>
> Thanks
>
> Mark
>
>  
>
>  
>
>  
>
>
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