[SI-LIST] Re: Cross-hatched reference planes
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Jeff Seeger" <jseeger@xxxxxxxxxxxxxx>
- Date: Wed, 4 Apr 2007 08:51:53 -0700
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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