Future: 0603 versus 0402 parts

Sounds like you must work more in a lab environment than a product environment. Since all parts need to be approved by purchasing and have purchasable part numbers as well as alt parts we don't use generic parts. So a CAD library is 0603_X7R_10V_.01uF not 0603_cap. Also each ties to a PCB library. So the schematic library is mated to an IPC7351 and 782 (if I got those numbers correct) footprint. If I want to change footprints I need to change the schematic and ECO back. If I didn't do it this way I would make an even bigger mess for purchasing. So I need to make a cad library for each part I use and that library ties be to a specific part and package size. Also I could care less about lab stock issues. It is stocking production parts, and pick and place feeders that is the issue. Takes time and money to swap that roll of 0603 10k parts out to 0805 10k on the pick an place machine to build a different board.

Hawker

Joerg ...

It is too bad that Protel killed off Circuitmaker/Traxmaker. The folks up here in Grass Valley that wrote Parts & Vendors had a "give me your circuitmaker.bom file and I'll translate it to your part number in P&V". Now P&V has a dozen or so "User Fields" for each part number, into which you could store, for example, Client1PN, Client2PN, and so on. WItht his you could give your customer their own ready for prime time parts list.

Just a thought, mindya...

Jim

Since I work

I haven't done this with Eagle yet but supposedly you can do it. BOM routine spits out linkable BOM, this links with Access type data base, from there you'd run the Client1PN report or Client2PN report.

PADS has lots of slots for part attributes. We use generic resistors like RES/0805 and then fill in the VALUE and HTI# (highland part number) fields on each part. PADS will then run a script file to make a bom in our format, and also can be persuaded to make a solder stencil and a pick-n-place coordinate file.

John

They were ahead of the pack, as was OrCad which had eight attribute fields even way back in the DOS days. Eagle doesn't yet and it took some convincing but we were promised it'll come. Most of us need at least one more than the usual two because there can be parts that have identical packages and names but, for example, one is screened for avalanche voltage range or manufacturer or something like that. Right now I must give it another name.

For me there is only one gripe left WRT Eagle but that is a major one. It does not allow hierarchical sheet structure. Not a good thing but Cadsoft doesn't seem to think it's important. Anyone who has done med or gvt work knows that it is.

you

In a typical hierarchy in the med industry the top sheet does not contain any parts. Maybe a house-keeping chip, RFID or a regulator but usually not. It contains 5-10 blocks that split the board into functional units. Each block has all the ports it needs and there are actually buses and nets going from one to the other. All of them. Now you can double-click on, say, the phase shifter block and it opens up the page with the circuitry. It has the same port pins. OrCad actually pinged me whenever I forgot one. Oh, do I miss that.

I like hierarchical :-)

Hierarchical schematics make some sense for things like FPGAs. But every part on a board has a reference designator and a physical existance, so how do you handle hierarchy? You can't have 10 R1's, can you? Some other naming convention?

I like flat.

John

I hate flat, except for the smallest of designs, and would never consider using a CAD system which does not support hierarchy. (I am currently using Protel). I typically use 3 digit part numbers, where the first digit identifies what block (sheet) the part is in, and the last two which part in the block. If there are more than 10 blocks I will use 4 digit part numbers for blocks 10 and up. Since the parts are grouped by function both on schematics and board layout, this numbering system makes finding parts on the board easy, and a design that really benefits from hierarchy will usually have enough parts that 3 digit part numbers are required anyhow (at least for passives). Where all or most of the blocks have less than 10 ICs I will use 2 digit IC numbers done the same way. If you screw up and use the same part number twice, DRC will let you know.

This lets you put a design with thousands of parts on paper small enough to print on a cheap laser printer, and small enpugh to easily handle when debugging.

Speaking of ports: Eagle doesn't really have any. Very annoying, not just with the (non-extant) hierarchical sheets but also with simple multi-page ones. Of course you can give net segments on different sheets the same name, and you can also label them, but if you mess around with your schemtic too much you may lose tracks of nets and labels.

I've once written a ULP that automatically labeled all net end lines that ended without being connected to anything, but it doesn't work right (because you never know which way up the label comes out).

I'm looking forward to the additional data field feature. Hopefully it's at the schematic level as well as on the library level, although in the latter case you can kludge around the limitations by putting the requited data into the "description" field and extract it via a ULP.

robert

I would have stayed with OrCad. However, when at companies it crashed on me too often and the price went up more than 3x since SDT just for schematic entry. Eagle hasn't crashed once.

IMHO it wasn't a good decision not to offer hierarchical on the next release but who am I to say.

We do everything B-size, 11x14", which is easy to handle and read, and punches/folds into a loose-leaf binder nicely. The biggest board I've done is something like 25 sheets, 1200 parts maybe, with sheet 1 being the block diagram and table of contents. I wouldn't like to silkscreen things like "R1531" next to every 0603!

We always resequence the ref desigs in physical order, to keep manufacturing happy.

John

We do that. And draw boxes around channels, and number them, and put text directions near switches and stuff, if there's room.

And we always say *what the board is*. I hate to find an interesting flea-market board that doesn't say what it is.

John

On Fri, 16 Mar 2007 09:42:57 -0800, John Larkin Gave us:

B size is 11 x 17, idiot.

Two a size side by side.

In a satellite radio LNA's application I learned a trick for trimming the outside corners of the pads on 0402's that reduced tombstoning from 3/1000 to something that didn't show up in the manufacturing fab report.

The new footprint is rounded on the outside and square on the inside.

I'm not a process guy, but I've changed all my 0402 and 0603 footprints in my designs - seems to work for both.

Frank

Thanks for sharing this, Frank. Those are the tricks of the trade that really help. Nobody might know why but they do.

MassivelyWrong lives up to his name once again. You stupid shit, "legal size" is 8 1/2 x 14.

Can you post the dims somewhere?

John

Give him some credit; he got it half right, which is better than usual.

John

Sure I got it wrong. Big deal. My ego's not so fragile that a typo on a sheet size is going to damage it. It's not like I ordered a thousand reams of 11x14 paper or anything.

You got the legal size thing wrong. So what?

John