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July 2009

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Subject:
From:
Gary Ferrari <[log in to unmask]>
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Date:
Thu, 30 Jul 2009 10:33:05 -0400
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There is some value in placing certain traces on the inner layers. If 
you must use fine lines and spaces, it is better to place them on the 
inner layers where they are only exposed to a print and etch process. 
Traces on outer layers are exposed to additional plating processes which 
tend to reduce the spacing. Depending on the plating requirements, it 
may be difficult to control the space sufficiently to meet minimum 
spacing requirements.

Gary

Graham Collins wrote:
> Ha...  We had a designer at one time who thought that surface traces were bad, very bad.  So every pad for every part had a short trace that immediately went to a via and the signal was routed to an inner layer.  Seriously.  That guy needs your doctor...
> 
> regards,
>  - Graham Collins
> 
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of James Head
> Sent: Thursday, July 30, 2009 10:50 AM
> To: [log in to unmask]
> Subject: Re: [TN] Hashing-Out Hatching
> 
>> Gary brought me back to the days when, just for kicks, I would take other 
>> guy's designs and remove all of their vias, just to prove I could do it.  I've 
>> gotten help, I'm cured, a thousand vias is nothing anymore.
> 
> You should pass me the details of your doctor - I always spend a little time at the end of a project going through and trying to eliminate vias if I can as I see everyone of them as a potential failure point - and it's very satisfying to re-run the drill report and see the hole count drop!
> 
> Mind you I'm not obsessive though.  I worked with one relatively inexperienced PCB designer once who spent a whole week designing a power and deflection PCB for a televison and managed to do it all without any vias or wire jumpers.  Unfortunately his design would never have worked with segregation between the primary and secondary sides of the transformer and 0.3 mm traces carrying high voltages and currents!
> 
> James
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