Bonucci said that it was difficult not to become complacent following the 3-0 first-leg win but that the goals in the second leg helped the team relax.
"It is a great satisfaction not to concede but credit goes to the entire team because we attack with 11 players and defend with 11 - this is our main secret," UEFA.com quotes Bonucci as saying.
"Once again we thank our forwards, because even tonight they did tremendous work in defending and they also scored the goals that allowed us to stay a bit more relaxed.
"It was quite difficult to remain focused [after the 3-0 win in the first leg], but the team proved to be up to the task once again."
Bonucci has made 30 appearances for Juventus this season.