Issue link: https://iconnect007.uberflip.com/i/1345210
50 SMT007 MAGAZINE I MARCH 2021 About four weeks later, I was at the office when Vino called my cellphone. I answered, expecting to hear some early success of initial testing of the assembly. But I knew something was wrong from the tone of his voice. "Steph, I need your help!" My heartbeat quickened. Vino proceeded to tell me that upon powering up the CCA, it got extremely hot within a few seconds, especially the backplane controller BGA. He had already powered up two of the five CCAs we had built, and each had this similar issue. We scrambled, discussing possible issues that caused the over- heating. It was difficult to assess this issue, since I was at the office and didn't have my personal lap- top that contained the PCB design. (I always use my personal laptop for consulting.) Within a few minutes of our discussion, a bad feel- ing hit me like a ton of bricks. While Vino was describing what he was checking, I ran back to my desk and grabbed my business laptop. I asked him to provide the part number for that backplane controller. I downloaded a PDF of the manufacturer's datasheet and jumped to the page that contained the BGA footprint details. I asked Vino to tell me where Pin 1 was identified on the actual part that was placed on the CCA, knowing that the part was placed on the secondary side of the design. en, I asked him to tell me where the Pin 1 markings were located on the PCB itself. He told me where Pin 1 was located on the PCB and that it also aligned with the part alignment markings on BGA, so I asked him to open the design. at very second, as we compared the foot- print in the design to the footprint in the data- sheet, we realized that our fate was sealed. We both knew the cause of our overheating: the footprint was designed incorrectly. It was designed as if you were looking through the board: basically backward. You can imagine the amount of F-bombs that were dropped by both of us as we combed through the manu- facturer's datasheet while triple-verifying the error, to no avail. We confirmed the worst-case scenario: a catastrophic mistake with no possi- ble chance of salvaging the five CCAs. What happened? e librarian from the third-party resource created the footprint manually and simply missed the one detail in the manufacturer's datasheet located under the image of the footprint that stated in a large, bold font, "Viewed from Bottom Side of Device." is was also missed by the indi- vidual who validated the part for release into the library. is one missed detail caused the footprint to be designed with the entire pin sequence 180° off. Devastating mistake with no potential of recovery? ere was no choice in this case but to make the footprint correction in the library, redesign a major portion of the board and re-spin the board. e ripple effect of such a mistake: Each CCA cost over $5,000 to fabricate and assem- ble. ere were five total assemblies with very little parts remaining due to limited funding and extremely long lead time on some of the ICs and connectors. Figure 1 shows a photo of one of the bad CCAs. e immediate follow-up meeting with the third-party library team was not pretty, to say the least. We had to deal with a missed sched- uled window of marketing opportunity, addi- tional unexpected cost, additional time to rede- sign and re-spin the board, and a very negative hit on our reputations. e rhetorical question is this: What is the true cost of this mistake? And what is the lesson from this experi- ence? Attention to detail is paramount in PCB design, especially when it comes to creating library parts. In my opinion, a good librarian is worth their weight in gold. You can do due dil- igence in circuitry design, design layout, signal analysis, and DFM, but if your library parts are not accurate, your CCA design may have a cat- astrophic ending. Can this type of error be prevented? Abso- lutely. Whether a footprint is created manually or with any of today's third-party automated library creation tools, attention to detail is key. I would even go one step further and suggest