One "tough EMC environment" product I was involved with even had a stamped metal shield "ground plane" over the *top* of the QFP package.
Best regards, Spehro Pefhany
Two possibilities.
1) The guy really doesn't know what's going on, and is taking advice from someone who doesn't know either.2) The guy has already selected a competitive product (because he gets a better kickback or his brother works there or whatever) and is looking for a reason to give the work to them instead of you. The blue board was his first attempt, and when you got around that, he's trying this. This could backfire, but you could go to him and say you think you've worked out a way to make the ground plane change in time, and ask if there's anything else. If another goofy reason pops up, politely run the other way.
OTOH, for thirty megadollars, you can get creative. Tell him you are going to paint the bottom of the micro with a metallic paint to serve as a ground plane, and add a contact for it to the board, or run a line of paint over to the ground lead of the micro, or whatever. After the board is stuffed, have somebody in production use a paint pen to draw a silver line on the bottom outside edge of the micro - "overspray" from when the bottom was coated.
Matt Roberds
Are you alone in selling into this app, or is there another firm involved? Have they got in first, with their only selling point being the solid toplayer ground plane, plus a course of educational visits to expensive restaurants and golf clubs?
Paul Burke
Why?
1.) Board layout is extremely dense as it is. I will have to go with a different micro offered in a smaller outline package and 0402 package resistors and caps to make room for a few traces and vias that are currently underneath the processor. The design work, including: selecting new components, retrieving quotations, circuit analysis, schematic capture, PCB layout, and software, will take approximately 3-4 weeks. 2.) Need time to get quick turn boards, build initial prototypes by hand, and bench testing. 2 weeks 3.) EMC test. Must be done at an outside lab. Lab time is extremely hard to get. I always count on 1 month for this but may get through it in 2 weeks if we pay VERY high expedition fees. 4.) Design validation testing. A majority of the testing can be completed in 1 month. However, some will need to linger behind. 5.) Production line change over, test modifications, and production validation testing. Minimum 1 month.That is if nothing goes wrong.
Ge0rge
I read in sci.electronics.design that Joerg wrote (in ) about 'Help: ground plane under microcontroller.', on Tue, 11 Oct 2005:
Or the following week, when she changed her colour.
Nothing changes. She gets the car.
I've had stuff running that fast on Vectobord. ;-) Well, admittedly, it was the type (I forget the number now, 8317 or something) with a ground plane (more of a grid, actually) on one side and pad-per-hole on the other.
Cheers! Rich
You need to present your story to the "trusted colleague" that said this wouldn't work. Using the Dilbertesque manager as a go-between will not work. Could you arrange a meeting between the trusted colleague and you? If you could present your measurements to the prognosticator, perhaps you could change some minds - or at least understand where they are coming from.
You could also dazzle them with pretty EM pictures provided by ATLC and show that the measly ground you have on the top layer probably does nothing because you already have a beautiful ground plane 20 mils away. Also see where Howard Johnson speaks about the uselessness of ground fills when you already have a ground plane.
Hello Keith,
Ah, right. Didn't Barbie get Ken's car, Ken's boat, Ken's house ...?
Regards, Joerg
Hello George,
Could you add a couple layers and via through? Or maybe offer them to place a "custom ground enhancement structure" underneath. Essentially ye olde copper tape but you don't have to say that.
Try labs in more remote locations, preferable smaller ones. It's been a while but I really liked those, worth the travel. Less bureaucracy, quick service, friendly and cooperative people. Oh, and during one of those EMC trips we were able to witness a true to the bones bar fight in Mariposa (just outside Yosemite). Hoss Cartwright would had gotten a kick out of it.
And something usually does...
Regards, Joerg
And then run off with Malibu Stacie? ;-)
Sure. "Divorce Barbie"; comes with all Ken's s*it.
Interesting. Did it have an insulating cover on the inside (towards the chip and leads), or was it just placed "far enough" away (tall enough) to not be a problem?
Matt Roberds
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