Five-times champion Roger Federer took the sting out of Croatian Ivo Karlovic's venomous serve to win 6-3 7-5 7-6 and book his place in a 21st straight grand slam semi-final at Wimbledon today.

Karlovic's thunderous serve had not been broken at this year's Wimbledon but the Swiss maestro nullified the 2.08m player's key weapon in the fourth game of their quarter-final and the Croat 22nd seed never looked like recovering.

"You expect a tough scoreline all the time, it's not easy to break him we know that so I am happy to have broken him twice and won the match," Federer said in a courtside interview.

"I love the record I have, reaching so many grand slam semis in a row. Twenty one is quite a number and it shows how consistent I have been, how injury-free I have been to keep it up for such a long time."

Karlovic had served 137 aces in the tournament before Wednesday and the signs looked ominous when his first serve of the day went whistling past Federer's ears to take his tally to 138.

But Federer got a sighter in the first game and a blistering blocked backhand return in Karlovic's second service game helped the Swiss to the break which he greeted with huge: "Come on!"

A single break was again enough for Federer to take the second set and though the Croatian took the third to a tiebreak the Swiss clinched it 7-3 with a forehand crosscourt winner after an hour and 42 minutes.

He will play Serbian fourth seed Novak Djokovic or Germany's Tommy Haas, seeded 24, for a place in Sunday's final.