Fly-half Stephen Myler kicked 20 points for Northampton as they secured a home semi-final in the European Challenge Cup with a 42-13 victory over Connacht.

Connacht had three players sin-binned, and Saints, who have won 32 of their last 33 games at Franklin's Gardens, will play the winners of Sunday's quarter-final between Saracens and Newcastle on the first weekend in May.

Stephen Myler landed six penalties from six attempts to punish Connacht's malfunctioning scrum who repeatedly fell foul of French referee Romain Poite.

The visitors, who were watched from the stand by Ireland's Grand Slam-winning coach Declan Kidney, could not handle the strength of the Saints pack at the set-piece but were competitive until caving in after full-back Gavin Duffy received their third yellow card.

Saints cashed in with four tries in the final 11 minutes from Neil Best, Joe Ansbro, skipper Bruce Reihana and Chris Mayor, with Myler and his late replacement Barry Everitt converting one each.

Connacht replied with an excellent try from number eight Ray Ofisa, and kicking points from fly-half Ian Keatley, but they were overwhelmed by the loss of Brian McGovern, Jonny O'Connor and Duffy to the sin bin.

They were penalised three times in the first half for pulling down the scrum and replacement prop McGovern paid the price for the previous misdemeanours of his team-mates when he was despatched only a minute after replacing the injured Ronan Loughney in the 34th minute.

McGovern was unlucky to be the first offender after the referee had, only a few minutes earlier, called out his captain John Muldoon to deliver a final team warning.

The scrum offences undermined the first-half attacking enterprise of Connacht.

Myler kicked a 40-metre penalty the first time Connacht pulled down the scrum in the 15th minute.

Keatley equalised four minutes later but the fly-half restored Northampton's lead in the 23rd minute after Connacht offended at a ruck.

The Irish side levelled again in the 29th minute when Keatley collected a clearance kick from Ben Foden and landed an opportunist drop goal after Northampton got in trouble trying to run the ball along their own line.

Myler made it 9-6 with the penalty which resulted in McGovern's departure to the sin bin and, with the visitors still temporarily reduced to 14 men, the former rugby league player struck again when Connacht were caught offside in front of their own posts.

But the visitors were still dangerous and they went ahead for the only time in the 52nd minute when former Harlequins player Duffy provided the pass for Ofisa to carve his way through the home defence and touch down near the posts.

The lead lasted only three minutes before Myler struck again from 50 metres after Connacht were penalised for obstruction.

Uncontested scrums were introduced for the second time when the unfortunate McGovern left the pitch again in the 62nd minute, this time through injury, to be replaced by back-row forward Colm Rigney.

Connacht contributed to their own downfall once again as O'Connor was sin-binned before they conceded another close-range penalty, with Myler landing his sixth successful kick of the afternoon.

Connacht tried hard to force their way back into the game once more but their hopes suffered an irreversible blow when the loss of Duffy reduced them to 13 men.

Saints capitalised by opting for the scrum rather than a penalty kick against their depleted opponents to drive flanker Best over for their opening try in the 69th minute.

They struck again three minutes later when Foden released Ansbro who raced over in the left corner, but Myler drifted the conversion attempt wide, his first miss from seven attempts.

Northampton, in full flow, scored their third try in the 78th minute, moving the ball along the line for Reihana to race over.

Replacement centre Mayor added their fourth try, charging in following a slick build-up involving substitute scrum-half Alan Dickens.