Number of Routing Layers: 6 Size of Board (square inches): 58.79 Equivalent IC count (1-IC/14 pins): 325.64 Board Density(boardsize/14pin-components): 0.18
I'm not sure what PADS means by that. It's probably hh:mm, but we have about 3 weeks in it so far, so maybe it restarts the clock every time we do a SAVE AS iteration, or something.
My board is a bit smaller, VME Eurocard at 6.4 x 9.2 inches, but it's interesting that our equivalent component densities are almost identical, 0.18 versus 0.20. We have three TSOPs (uP and two Xilinx's) and jillions of tiny analog things and 0603 parts. It's a 16-channel isolated-output DAC, basicly. 16 relays, too!
I'm luck to have some *really* good people in-house who assemble protos and moderate production runs, and we confer with them during design to make sure they'll be happy building the beasts.
I'd have been tempted to add one relatively pointless unstuffed footprint to the 1,999 one to bring it up to an even 2,000. ;-)
Best regards, Spehro Pefhany
--
"it\'s the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Now imagine this one, true story: We were doing layout in the 80's on a large mainframe. During the 23rd hour a snow storm was beginning to brew. It became spooky outside. Then I could see large 100kV lines in the distance swing back and forth, screamed "backup" and a few minutes later those same lines touched with an impressive arc. Poof, no more power. After 2-3 hours the air inside became unbearable and we all went home. The next afternoon we had power again but the backup files wouldn't read correctly and we were back to square one :-(
I like to plop a bunch of grounded thru-holes around my boards. We insert a few 2-56 screws from below, with nuts on top, as scope ground clip targets.
And right, the test point you really need is seldom there!
That last PCB was laid out twice in a row. It had 1567 smt and 432 thru-hole parts, and from the outset we worked with the mfg to ascertain the necessary clearances for the leaded component stuffer. My tech spent almost a month laying oput the PCB, and after it was completed the contract mfg changed their minds about the required clearances (they doubled), and he had to re-do the *entire* layout. It took 2-and-a-half weeks the 2nd time, and we were not happy. The word "f*ck" featured prominently in our discussions.
After that PCB was laid out, they changed their minds again, and we hit the roof. A site visit showed the problem was a lack of competence on their part - we showed them what to do and they managed to make it work
- the prototype run of 200 units was perfect.
The hilarious part is they then went on to manufactuer 1000 units, of which about 400 had piss-poor reflow soldering - esp. around the TQFP144, the solder paste hadnt reflowed at all. We sent 10 back to be reworked, and they came back looking like a plasma cutter had been used to do the job. So I spent 3 weeks hunched over a binocular microscope, doing it by hand.
needless to say that was the last job they ever did for us, and I take great delight in spreading the story far and wide (NZ is a small country). bastards.
I saw the costed BOM for that PCB yesterday. total parts cost (excl. 121 LEDs) is $8 less than the micro cost in the (non-functioning) design it replaced. Its 120 copies of the same thing.
I've got 45 SOIC14s, a SOIC8, a TQFP44, lots of 0603s and 1206 quadpacks, a few dozen dual transistors, 121 photodiodes and 120 LEDs. Oh, and a crystal and a buzzer too :). The layout was a bit tricky because of the circuit design - 1000x gain on lots of signals that run all over the PCB, so crosstalk was a problem.
I love my job :)
I especially like laying out analogue circuits (they are "ue" better than analog circuits ;) in smt, its a real challenge to make basically single-sided layouts.
thats the smart approach. I like vertical integration, but a good contract manufacturer is the next best thing. The guys I am using for the first PCB are fantastic, they really know their stuff.
my ABSE doesnt always work that well (I blame Telecom). I often cant see posts, this one included. Another problem is the blank post - no content at all.
I'll have a crack at it, although I have never tried to download a pic from my camera (shock, horror).
Regards, Terry
PS if you guys ever make it down this way, look me up.
I installed my camera software, and downloaded all of the saved images. fine. Then I took a photo, and now my PC doesnt recognize the USB device. Aaargh!
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