FreeLists / si-list / [SI-LIST] Re: Cross-Hatched Reference Planes

["Mitch S. Morey" <cadpro2k@xxxxxxxxxx>]

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Date: Wed, 4 Apr 2007 10:43:01 -0700 (PDT)
Subject: Re: [SI-LIST] Re: Cross-hatched reference planes
From: "Mitch S. Morey" <cadpro2k@xxxxxxxxxx>
To: leeritchey@xxxxxxxxxxxxx
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And another response comes to mind when you get back to original question
of "Cross-Hatched" and "Reference Planes"

If you imply reference planes to be impedance associated reference planes,
then: "Cross-Hatched Reference Planes equal disaster." If they are simply
cross hatched power planes, that's a different matter. Still, like Lee
mentions, with PCBs very select (few) cases are warranted.

Good day.
Mitch

>
> Jeff,
>
> I agree that there are a few exotic places where laminate to laminate
> bonding is needed and is accomplished using cross hatching as well as in
> flex circuits to improve flexibility, which I think was the original
> question.
>
> I responded the way I did because there are still those who want to see
> this done to ordinary PCBs made from copper and FR4 class resins, where it
> was needed long ago.  I did several designs this way just to prevent
> delaminataion.  The industry fixed this problem long ago.
>
> I don't think there is much to debate here.  My goal was to make sure that
> this old sock did not creep back into standard multilayer board design.
> And, yes, this is often necessary in multilayer ceramic IC packages.
>
> Lee Ritchey
>
>
>> [Original Message]
>> From: Jeff Seeger <jseeger@xxxxxxxxxxxxxx>
>> To: <leeritchey@xxxxxxxxxxxxx>
>> Cc: <si-list@xxxxxxxxxxxxx>
>> Date: 4/4/2007 8:27:09 AM
>> Subject: Re: [SI-LIST] Re: Cross-hatched reference planes
>>
>> Lee Ritchey wrote:
>>
>> >All of those reasons, except the flex circuit one, went by the wayside
> many
>> >years ago.  Wonder why they still linger around the industry like old
> socks!
>> >
>>     Agreed venting and bonding concerns first appeared in 60s military
>>     specs but I'll wager that if you were to chat up a substrate foundry
>>     there is current call for venting.
>>
>>     On the bonding front we were recently asked to provide some "hatch",
>>     understood to be for laminate to laminate, in an area of a board
>>     lacking vias.  The board involved fussy materials and a challenging
>>     end-use environment.  I don't believe it was an offhanded request.
>>
>>     We'll simply have to agree to disagree on cross hatching as a way
>>     to work with supply- and signal- dense areas to minimize the layer
>>     count *and* bow and twist.
>>
>>     I'd be happy to debate further but suggest IPC's Technet as a more
>>     appropriate forum for the bandwidth on DFM issues.  Old socks can
>>     become new again, it can be useful to recall where we put them.
>>
>>     Respectfully,
>>
>> --
>>
>>       Jeff Seeger                         Applied CAD Knowledge Inc
>>       Chief Technical Officer                  Tyngsboro, MA  01879
>>       jseeger "at" appliedcad "dot" com                978 649 9800
>
>
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>



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