Swiss Covered Bonds (Pfandbrief): Any thoughts?

I kind of got curious about exchange-traded bonds issued by “Pfandbriefzentrale der schweizerischen Kantonalbanken” and “Pfandbriefbank schweizerischer Hypothekarinstitute”. There are many more than issued by the Confederation, nice yields (from 0.8% p.a. according to Bond Explorer of SIX), big choice of maturity dates, many have low, but not zero, coupon.

Looks like a good choice to build a bond ladder or as a replacement for fixed term deposits, as they are liquid.

But first thing first: are they really very safe, as or almost as Confederation bonds?