I downloaded the official PSoC 4200 PCB footprint libraries for Allegro, Altium, and Pads and there does not seem to be an official footprint for the WLCSP 35-ball package (the FN package). I have the 4200 family datasheet (001-87197 Rev. *J), and there is a drawing of the package on page 38, but no corresponding footprint specification. I have read JEDEC Design Guide 4.18 per the instructions in the datasheet, but it (as expected) only describes the package, not the recommended PCB footprint. I, of course, have the die WLCSP package size and pad spacing from the datasheet, so that's not an issue. All I need is the recommended pad size to complete the footprint myself. Any suggestions?
Edit: I found an application note from Freescale (now NXP), AN3846: Wafer Level Chip Scale Package (WLCSP), from 2012 that provides guidance for their WLCSP packages for both PCB layout and manufacturing. There is a copy here:
They say their their solder balls are 0.250mm in diameter, but Cypress says theirs are 0.260mm. I am going to guess that if I scaled the pad sizes by 0.260mm/0.250mm = 1.04, that I would get the right pad sizes for the process specified by Freescale/NXP. It's a bit of a bummer that Cypress doesn't seem to have any guidance at all on this even though they provide WLCSP packaged chips.
Solved! Go to Solution.
Well, I managed to find the Cypress equivalent of the Freescale/NXP document on WLCSP requirements! It was not easy though (I had to follow a bread-crumb trail from older documents that hinted that such a thing existed, even though it ended up having a very different name now). Here it is:
"AN69061 - Design, Manufacturing, and Handling Guidelines for Cypress Wafer Level Chip Scale Packages".
It has all the information needed to design the PCB. I also found this note from Mentor-Graphics that has a lot of information:
And apparently there is a tool called "PCB Libraries" that has an "IPC-7351 Calculator" that will generate the industry standard right sized pads based on your input about the package and layout technique you want to use (NSMD vs. SMD). I haven't tried it myself, but they say there are free versions.
Anyway, I think I have my answer sufficient that I can generate my own footprint now and have it agree with industry standards (IPC-7351 apparently... a "pay for play" document unfortunately).