Socket connector with contact terminal having waveform arrangement adjacent to tail portion perfecting solder joint

An electrical connector for connecting an electronic package and a printed circuit board, comprising:

• an insulative housing defining a plurality of passageways extending therethrough in a vertical direction between opposite upper and lower surfaces thereof;
• a plurality of contacts disposed in the corresponding passageways, respectively, each of the contacts defining a base portion retaining to the housing, an upper contacting section extending upwardly from the base portion and beyond the upper surface for contacting the electronic package, a tail section, with a waveform thereof, extending downwardly from the base portion to hold a solder ball for connecting to the printed circuit board;
• wherein
• in a side view, around a bottom portion of each passageway and for each solder ball, the housing provides a vertical wall and a downward oblique wall above said vertical wall to contact one lateral side of the corresponding solder ball at two respective points, and the waveform compliantly abuts against another lateral side of the corresponding solder ball.