Hi, Steve, Sounds like you're having fun with this one, and I would be most interested in being allowed to share your evolving experiences with trying to use Stablcor. I flagged this material up to our designers when I first heard of it (being simple souls, they'd designed our boards with good ol' FR4), but we haven't had the excuse to look into using it yet. The specs are now aging, and you're right about how densely packed the boards have become, with folks trying to pack as much functionality into each as humanly, or inhumanly, possible. I look at it as a cocoon within which, and from which, any number of beautiful butterflies can grow and emerge. (What DID that girl put in my coffee?) We have two boards on the go that are a distillation of the functionality of five slots previously. They've given me a folicular race between going grey or bald (it's neck and neck at the moment). The one thing we had to give serious priority to after the component selection stage was layout to balance thermal mass around the board, placing hotter components closest to the best thermal path through the board, and particularly putting the hottest ones on the component side where there was Max Headroom (remember him? I loved that guy). That way, if the thermal path through the board is still not enough, you have some scope for taking the heat out over the top with nice chunks of metal and thermal pads. Pity there's no room for Pentium 4 style heatsinks here! There's no room at all for overhead heat sinks on the solder side. My sincerest sympathies! Peter Stephen Gregory To: [log in to unmask] <SteveZeva@AO cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST L.COM> Aero/ST Group) Sent by: Subject: Re: [TN] VME stuff again... TechNet <[log in to unmask] ORG> 01/23/02 12:19 PM Please respond to "TechNet E-Mail Forum."; Please respond to SteveZeva Hi Peter! The spec that you quoted, is what is being followed. I'm going to purchase the spec so that we have it here...since it appears that we're getting into the business of "ruggedizing" commercial VME assemblies. From a personal view, I think that VITA established the standards prematurely without considering how the the technology was going to evolove. As you know, VME assemblies are extremely dense, basically single board computers. The assembly that I'm looking at is double-sided SMT, fine pitch on both sides, 0402's, 18+ BGA's on the top side (313 balls, the max I've seen so far from the BOM). Not sure if establishing these restrictions are a good thing, so that everything will fit as established, or if it's better to stay fluid so that you can adjust to adapt to changes in the technology...I suppose there's arguments on both sides... Just know now that we have an assembly that can take advantage of some new substrate technology, that sounds very promising as far as heat dissipation, and CTE issues, but can't use it because of the VME spec...this is one of what came first, "The chicken or the egg?" huh? -Steve Gregory- Hi, Steve, We ran into the same problem (more or less) - thermal management requirements and solutions conflicted with the VME spec (which spec did you go with, by the way?). One solution we considered, but didn't implement owing to expense, is to "step" the PCB so that it's the right thickness at the card guide edges and at the P1/P2 connector areas. Is that possible with Stablcor? - I don't know. Makes routing traces to the connectors a bit circuitous too (pun intended). The board thickness outwith these areas is not important, as long as it, plus the component height, doesn't exceed the envelope max. You'll need some pretty light-weight copper and very thin separation layers to fit 16 layers into the spec'd thickness. Good luck! Peter Stephen Gregory To: [log in to unmask] <SteveZeva@AO cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST L.COM> Aero/ST Group) Sent by: Subject: [TN] VME stuff again... TechNet <[log in to unmask] ORG> 01/23/02 10:41 AM Please respond to "TechNet E-Mail Forum."; Please respond to SteveZeva Hey all ya'll! VME stuff again. Pretty strict standard. Gotta new technology out there called Stablcor from Thermalworks, problem that we're seeing is that board thickness is going to increase, which violates the VME spec's. Not just from the card-guide aspects, but will change the dimension where the P1 and P2 connectors interface with the backplane on a standard VME card cage. Just wondering if anybody has anything out there (connectors, etc.), that will allow you to "shoe-horn" ten-pounds, inna 1-pound bag, that will comply with VME spec's. This board is 16-layers, within .063" without Stablecor, if we use 2-layers Stablcor, it will increase .020-.025", with 3-layers Stablcor (the best, as far as thermal dissapation and CTE solutions), it will increase .030-.035". This Stablcor material sounds like a really good solution for thermal and CTE solutions, but has a hard time staying within the dimensional spec's that are called out in the VME spec's...trying to change these spec's I know is an act of God...it's there, and it's done. Just wondering if anybody else has explored this material, and have come to a dead-end like I have....because of the reasons like I have. -Steve Gregory- [This e-mail is confidential and may also be privileged. If you are not the intended recipient, please delete it and notify us immediately; you should not copy or use it for any purpose, nor disclose its contents to any other person. Thank you.] --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------