Issue link: https://iconnect007.uberflip.com/i/1337116
30 DESIGN007 MAGAZINE I FEBRUARY 2021 some of the connector manufacturers give you the location of Pin 1 but not Pin 2. I wish all component manufacturers knew what infor- mation to provide in their datasheets to make our job easier. e number one feature that's missing in most component datasheets is the manufac- turer-recommended footprint pattern almost never provides dimensional data from the hole or surface mount pattern to the edge of the connector body. is is a necessary piece of missing information that causes errors. is can be checked when the 3D model is inserted into the footprint pattern to ensure the silk- screen and assembly outline matches the pack- age boundary. Another thing about the connectors: You must use their manufacturer-recommended pattern. ere's no IPC calculator or magic formula for calculating a complex connector pattern. Many of the connectors today are a mixture of plated-through mounting holes and slots, non-plated alignment holes, surface mount pads, and every type of combination. So, you must use the manufacturer pattern. I just did a library part last week, a 15-pin D-Sub miniature connector. We built it per the manufacturer pattern and exactly per their dimensions, but there was a datasheet typo. e only thing that saved us from duplicating the error in the datasheet was the 3D model. e mounting holes lined up with the 3D model, but all the pins were in the wrong loca- tion. I looked at it, measured everything, and everything was correct by the datasheet. And then I found out that the manufacturer had one dimension wrong. ey dimensioned the mounting hole to Pin 1 but the value was to Pin 5. In other words, there was an inherent typographical error in the manufacturer's data- sheet. So that's another thing to be very careful about. Double check with the 3D model. Shaughnessy: Datasheets have errors aer all. Hausherr: Right! Hard to believe. Let me give you an example. I did a design a couple of years ago with a large 200-pin LGA. I sent the design Gerber data to a fabricator. Before they built the boards, they ran a Valor VPL check. And there was nothing wrong with the pad sizes or the land pattern, but they did catch an error in the pin assignment. e component manufac- turer did not indicate "top or bottom" view, so I guessed. e alphanumeric pin assignments were all incorrect. When they ran the Valor VPL check they discovered that all the pin numbers were back- ward. Now, let's say that they didn't run the Valor VPL check. ey would have manufac- tured and assembled the boards, and every- thing would have assembled perfectly. But when the EE engineer turned on power, none of the PCB functions would have worked. In my case, all the terminal leads were fine, but it was the pin assignment that was totally backward. e Valor VPL check caught that mistake. Unfortunately, I had to redesign the board at my expense. But that one little catch saved thousands of dollars in fabrication, assembly, and components. e board would have been declared a door stop. Shaughnessy: What is the cause of that in the first place? Tom Hausherr