Researchers at IMEC have found that quartz-filled compounds used in place of halogen flame retardants in plastic packages lowered the CTE, and the subsequent mismatch in thermal expansion between the package and board is causing solder joint fatigue cracking, researchers found. The investigators are calling this failure mode “Cu lead fatigue fracture.”
Here’s the link: http://circuitsassembly.com/cms/news/12195-paper-halogen-free-packages-reveal-new-failure-mode
T’was a a dark and stormy night when the news came through. Joe Layout had been both dreading and preparing for years. But it had always been little more than rhumors from a far off land. It was a looming threat, always dancing in the distance, but never quite real.
Until now. 1.27mm, 1.0mm, 0.8mm, 0.5mm, 0.4mm … and now … drum roll please 0.3mm pitch.
I just got an email announcing an Amkor 8 x 8mm 368 ball BGA at 0.3mm pitch. Yikes.
There’s still some controversy over the best way to make a 0.4mm pitch BGA land pattern. Some say says you need to use solder mask defined pads. Some say you still need to use the non-solder mask defined pads. Now we throw something 25% smaller into the mix. The image isn’t to exact actual scale — because I don’t know how big your monitor is — but the parts are in relative scale from 1.27 pitch to 0.3 pitch.
If you can’t see it, you shouldn’t eat it
Here’s another issue we see from time to time involving the old, familiar, 0.1″ pitch headers. When initially laying out the board, the footprint for the break-away header is used. It’s small and easy to use. The headers are cheap and easy and you don’t need to stock a bunch of different pin-counts.
That’s all fine and dandy until the next rev of the prototype when you decide to change to a shrouded header for the additional reliability and pin protection afforded by it. When making that change, don’t forget that the footprint with the shroud may very well be bigger than the break-away footprint.
In this particular case, it wouldn’t have mattered except for the capacitor that ended up under the shrouded header.
Get out of my cap’s space, man