{"id":363,"date":"2023-01-26T17:16:00","date_gmt":"2023-01-26T22:16:00","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/valor-dfm-solutions\/?p=363"},"modified":"2026-03-27T09:44:36","modified_gmt":"2026-03-27T13:44:36","slug":"the-mysterious-case-of-the-missing-bowties-part-ii","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/2023\/01\/26\/the-mysterious-case-of-the-missing-bowties-part-ii\/","title":{"rendered":"The Mysterious Case of the Missing Bowties Part II"},"content":{"rendered":"\n

Previously\u2026 <\/a><\/p>\n\n\n\n

After receiving our boards and having them pass inspection I breathed a sigh of relief as this project was finally on the home stretch. Procurement sent the bare boards and the design data to our primary contract manufacturer (CM). This CM also has DFM software. For them, the obvious focus is assembly related DFM issues.<\/p>\n\n\n\n

By now I\u2019m sure you have figured out where this is going. Yep. After having our design for a week, the CM found their own list of DFM issues that they wanted us to address before resuming the tooling of our job for assembly.<\/p>\n\n\n\n

This time, there were about forty items being flagged.<\/p>\n\n\n

\n
\"\"<\/figure><\/div>\n\n\n

I sheepishly shuffled into my boss\u2019 office once again, bearing further bad news. \u201cThe project is on hold again,\u201d I said – Might as well just get to the point.<\/p>\n\n\n\n

\u201cWhich one?\u201d he asked. \u201cThe new one?\u201d<\/p>\n\n\n\n

\u201cNo,\u201d I replied. \u201cThe old one.\u201d<\/p>\n\n\n\n

\u201cTHE OLD ONE?!?!? What the hell! I thought you had taken care of all those issues and put them to bed!\u201d<\/p>\n\n\n\n

\u201cI did, kinda. I fixed all the fabrication issues but now our CM has a whole new list of their own assembly DFM issues.\u201d<\/p>\n\n\n\n

\u201cYou gotta be kidding me!\u201d<\/p>\n\n\n\n

\u201cHow many issues are there? Are they legitimate? How critical are they?\u201d<\/p>\n\n\n\n

Oh great. Now the grilling is coming three questions at a time.<\/p>\n\n\n\n

All I could say was, \u201cI\u2019ll get back to you once I investigate.\u201d<\/p>\n\n\n\n

I pull back up the design, use my second screen to display the DFM report from the CM and step through the issues one by one.<\/p>\n\n\n\n

The first issue the CM is complaining about is the footprint for some of the 0201s isn\u2019t adequate to comply with IPC Class 2 standards. How was I supposed to know? My EDA library doesn\u2019t have the pin contact area defined.<\/p>\n\n\n\n

Next on the list was an issue having to do with the height of a connector. Apparently, as the board would go through the AOI machine on the SMT line, the height of the connector would shadow the solder joints on an adjacent component, resulting in an un-inspectable part.<\/p>\n\n\n\n

And then the CM DFM report said one of our alternate parts for a 3-pin SOT 23 didn\u2019t fit the pad properly. Really? I wonder why our component engineer didn\u2019t catch that?<\/p>\n\n\n\n

Once again, my fire-breathing dragon boss stomped over to my desk and lurched over my shoulder. As I continued looking at the issues, he interrogated me about each one. \u201cWhere are the darn bowties?!?!? I don\u2019t see any bowties on any of these issues. Why didn\u2019t our DRC or DFM software catch these?\u201d<\/p>\n\n\n\n

\u201cI don\u2019t know. They\u2019re missing.\u201d<\/p>\n\n\n

\n
\"\"<\/figure><\/div>\n\n\n

\u201cI can see they\u2019re missing! Why are they missing?!?!?\u201d<\/p>\n\n\n\n

He wasn\u2019t the least bit humored when I sarcastically replied under my breath, \u201cIt\u2019s a mystery.\u201d<\/p>\n\n\n\n

I spent the better part of three days revising the design to address the issues raised by the CM. Unfortunately, many of the changes required had to do with footprints and placements, so there was a fair amount of re-routing needed. And of course, that meant a new spin going back to the bareboard fabricator on our dime.<\/p>\n\n\n\n

The boards were finally built without issue and we shipped the product \u2013 six weeks late.<\/p>\n\n\n\n

to be continued…<\/p>\n\n\n\n

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