Head gimbal assembly and magnetic disk drive with specific solder ball or slider pad and electrode stud dimensioning to produce reliable solder ball connection using laser energy

22Embodiments of the invention provide a head gimbal assembly (HGA) capable of effecting solder ball connection with use of low energy. In one embodiment, the HGA includes a head/slider. In the head/slider, slider pads and lead wire pads are connected to each other by reflow of solder balls under the radiation of a laser beam. Lead layers are connected to a magnetic head and electrode studs are connected to the lead layers, respectively, and are also connected to the slider pads. The diameter R (m) of a solder ball and a sectional area S (m) of an electrode stud are in a relation of R≧4S.