Key fragments

I know i can't get chests on free week champs but can I not get key fragments? My last key fragment i got was on the 25th and I've played 14 games since then. 12 games on SR I've won 9 and 2 games on games howling abyss 1-1. From what I read on the site and people comments keys are supposed to be more common than in my experience. Is there something specific I need to do or avoid doing?