Issue link: https://iconnect007.uberflip.com/i/1337116
FEBRUARY 2021 I DESIGN007 MAGAZINE 31 Hausherr: When the manufacturer's datasheet shows the top view and the bottom view, they must clearly define which is the top view and which is the bottom view, and what you are looking at. Oen, they mark the pin assign- ments, and some manufacturers are kind of lax at labeling all this documentation. Also, the LGA package pin assignments are sometimes intentionally mirrored. Nowadays, the component manufacturers are giving acceptable recommended footprint land patterns. ey call them the "Recommended Footprint Pattern," just the "Recommended Pattern," or "Solder Pattern." PCB designers or CAD managers are split in two. I would say that half of the global PCB industry prefers the man- ufacturer pattern, the other half of the industry prefers to use the IPC calculator pattern, and there are some who use a combination of both. But land pattern calculators are soware code that are not flexible enough for non-standard packages. As we move to the future, standard packages are being replaced with complex non- standard packages to intentionally eliminate competitors from producing lower cost alterna- tives. ese new non-standard packages require manufacturer-recommended patterns. We have 100,000 users of our soware pro- gram worldwide and we run into this every day. We add the manufacturer-recommended pattern data in all our CAD library data files, but those can be turned off and revert to the IPC pattern. We have several millions of man- ufacturer part numbers on our cloud database. For instance, Boeing would download a bunch of parts and then say, "Why do you put the manufacturer's pattern in here?" I said, "Well, it's easier for us to do that because all you have to do is uncheck a box and then it defaults to the IPC pattern." And they said, "Yeah, but we downloaded the whole bill of material with the parts and now we've got to go and uncheck all these boxes and resave every part to get the IPC pattern." It's really hard to please everybody. You go aer the manufacturer's pattern, and a lot of times the manufacturer's pattern is superior to the IPC specifications. I've downloaded mil- lions of datasheets and checked everything out, checking against both different mathe- matical models and the manufacturer's recom- mendation. en, it's knowing which pattern is best aer looking at millions of land patterns and millions of footprints. However, we've been creating land pattern calculators for 20 years and no one has ever complained about creating a bad footprint. Alternatively, we've never heard of anyone complaining about using a manufacturer's rec- ommended pattern, as long as the terminal leads are on the pad. I'm sure that there are typos in datasheets, so the PCB designer must ensure that the terminal lead is on the pad and our soware calculators clearly indicate both the terminal lead location in respect to the pad location. And it's difficult. If you have a QFN bot- tom terminal component with a thermal tab, some manufacturers provide recommended stencil data pattern. You have to know stencil data pattern rules. You've got to have a 0.20 mm "minimum" web between these patterns and stay within 0.10 mm from the pad edge. And if the calculator calculates anything less than that, you're going to get a small web in between the stencil apertures. When they go to assemble it, they're going to use that sten- cil a dozen times and shred it because the web between the apertures is so small. But the sten- cil manufacturers should know this. And they should make the stencil a bit more rugged for the paste mask application process. Shaughnessy: Tom, Happy mentioned a few weeks ago that the standards in some countries and some of the manufacturers' own numbers were far superior to IPC's standards. Happy Holden: Yes, JPCA had been using lead- free solders for a lot longer than we had. And because of their focus on miniaturization and the fact that lead-free solder was much stron-