Can ROHS BGA be used with SnPb solder?

[tjdyhdsfeadgstdj]

It's my understanding that it is a bad idea to mix lead-free and leaded solder, and that it can cause cracks.

I'm using a TFBGA100 package on an STM32H7 and have some long-term reliability requirements. In order to avoid tin-whiskers, I was considering using SnPb (leaded) solder.

But then I started wondering, if the TFBGA uses collapsing solder balls, and the device is lead-free, wouldn't this cause issues with the leaded solder? The balls would be lead-free and the solder on the board would be leaded?

Does anyone have experience with this?

[Douglas MILLER]

Hello Adam,

Please check the following link for information on mixing leaded and lead free solder - https://www.eevblog.com/forum/beginners/mixing-lead-solder-with-lead-free-solder/ 

[tjdyhdsfeadgstdj]

Thanks for that link, however, I've already done a bunch of searching and reading; I was hoping to find something more official. Does ST recommend against using leaded solder on their BGA components?