[SI-LIST] Re: Skin depth,copper,gold

  • From: Jonathan Riley <jonathan.lloyd.riley@xxxxxxxxx>
  • To: jeff.loyer@xxxxxxxxx
  • Date: Sun, 6 Oct 2013 20:14:40 +0100

Hi all
Could someone clarify a two things regarding platings:
1. Concerning ENIG. The amount of gold used is tiny (certainly compared to
the amount of nickel) and I thought that the effects of diffusion caused by
the soldering process results in the effective layer becoming thinner
still. For the sake of being able to make rough approximations, on an ENIG
board it seems to make sense to just ignore the gold from an SI point of
view. Please can someone advise whether this is really a fair thing to do
and if possible say at what point the effects of the gold will begin to
matter?

2. For boards running at 10Gbps upwards, what plating options are the best
ones to choose? And which are best avoided?

Regards
Jonathan


On Sun, Oct 6, 2013 at 7:26 PM, Loyer, Jeff <jeff.loyer@xxxxxxxxx> wrote:

> On most designs, the ENIG is only applied to pads, etc. exposed by the
> soldermask, so it doesn't matter.  Plating the entire trace with ENIG is
> generally done only by mistake and causes a huge increase in insertion loss.
>
> Jeff Loyer
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of bala
> Sent: Saturday, October 05, 2013 2:47 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Skin depth,copper,gold
>
> Hi all,
> When I model my surface microstrip trace,generally,I am taking properties
> of copper into consideration.and if my copper plated with gold or nickel,I
> am suspecting if we really need to consider the properties of plating
> material as well.One of the document says ,based on your skin depth choose
> your material property.My question is at low freq my signal uses my entire
> cross section(copper+gold) and at high frequency my skin depth shrinks and
> my signal uses outer surface of my conductor(gold on top side ,copper on
> bottom side).In both cases I should take both properties.How skin depth
> plays a role in choosing the material property (copper or both)while
> modeling microstrip?
> Regards
> bala
>
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