Mcad/ecad collaboration, handshake

Assembly and Components SMT and through-hole techniques
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Importing/exporting files back/forth with ecad dept there seems to be miscommunication with where the origin and component coordinate system are
located. Mechanically, I am using lower left corner and typically on a mounting hole for board origin and calling the coordinate system “cs_ecad” and component coordinate systems are called “Ec_def”.

Problem I see with imports from ecad layout:

  1. Different board csys locations.

  2. Centroid coordinate systems for all components (both SMT and thru hole). Where I’ve been using centroid coordinate system’s for only SMT components and thru hole csys components are always located at Pin 1 per spec sheet.

Is there an industry standard for this? My last company this was the process and layout started in mcad and then passed to ecad so origin csys, board outline, mounting, and keep out/ins, etc. was never a problem.

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I would say this is highly dependent on the ECAD tool and the MCAD tool, as well as the handshake method that is being used.

For example, if the ECAD is Altium Designer and the handshake method is IDF to Creo MCAD, everything is referenced to absolute origin of Altium Designer. Other tools might allow using relative origin.

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Hi Tim,
ECAD is using Mentor Xpedition and company is on Creo 8 using both IDF and IDX workflow. Our handshake process is being developed for Creo. Previously they used 2d acad and then SolidWorks with minimal component footprints/libraries. Currently, switching to Creo.

The biggest pitfall is getting on the same page locating board origin coordinate systems and component coordinate system. I am trying to confirm if this is the industry standard for CCA layout, thru hole (pin 1) and SMT (centroid) components?

One of the ecad designers told me they use centroid for both thru hole and SMT. Thru hole spec sheets locate at pin one, correct? So, this is what I’ve used at other companies. Not that you couldn’t calculate to the center for thru hole components.

What’s the best choice starting in Mcad or Ecad? Mechanically, I fit into the assembly with a board layout where I specify the csys for the board origin, then it’s exported to Ecad (Xpedition). Now we just need to be on the same page for component csys’s as we import/export IDX file.

different issue:

A board I just did had castellated holes and Xpedition treated them as a component, I had to manually replace them as cutout in Creo. Again, the best practice would have been to define castellated holes in Creo first and then use IDX for iterative design exchange. I know I am bias mechanically, but it seems to be the best workflow.

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Many companies use the centroid for SMT and pin 1 for thru-hole packages. Using pin 1 for thru-hole dates back to programming axial and radial insertion equipment. Designers from those days tend to stay on that path while younger designers have no idea of that history and might use centroid for everything. As to whether that is industry practice, one would need to review IPC documents to see if they call that out or not. Another place to look would be PcbLibraries.com. They have a forum which might also talk about this for their footprint wizard. Mentor also has a footprint wizard, so what does it use when creating thru-hole footprints?

My current company’s operating procedure uses SMT centroid and pin 1 for thru-hole.

The main downside of not using pin 1 for thru-hole parts is whether they are machine placed and if the machinery has a pin 1 programming expectation. Another item that I have noticed is some thru-components such as connectors can have wide size tolerances between vendors which might make defining centroid more challanging in comparison to pin 1.

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Thinking back to those earlier days of routing thru-hole boards, those were generally 2 or 4 layer boards and the whole board was leaded parts, the designer generally will want to align all of the holes in order to be able to route between them. 100 mil pitch lead bent components was extremely common and I could route 10 or 12 mil wide tracks between most pads (those were the days!). If the th-footprints were centroid, it might be more challanging to align the holes for routing purposes. Now days, most boards have very few th-components and CMs might no longer even have automated TH machines since that is not worth keeping them around for the few times they make sense.

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Mainly connectors on the edge are th-compoents

Tx’s_Ed

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