HighSpeed Oblique CTSystem forSolder BumpInspection

Thehigh-density LSIpackages suchasBGA (ball gridarray) andCSP(chip scale package) arewidely usedinthe electrical products. Solder bumpisusedasanelectrical junction ofthese packages, andtheycannotbeobserved fromoutside. X- rayfluoroscopy isusedasinspection method. Itcannot evaluate theshapeofsolderbump correctly becauseinformation is compressed alongtheray.Theoblique CT isconsidered asa methodforaccurately examining theshapeofthesolder bump. Conventional oblique CT still hasthespeedandmechanical constraint, anditcannotbeintroduced intothesoldering line. In this paper, wepropose thenoveloblique CTsystem thatcannon- destructively obtain the3Dshapeofsolder bumpatahigh-speed. Thissystem obtains theprojection images fromvarious directions using therotational transfer offlat paneldetector andthefixed mountedopen-type X-raygenerator thathasawideradiation angle, andreconstructs 3D imageusingthe3D FBP (Filtered BackProjection) method. Inaddition, we havedeveloped the reconstruction acceleration unitforoblique CT,andthusthe3D imageisobtained intherealtime.Inourexperiments, we evaluated thesolder joints ofBGA mountedsubstrate. Theresult demonstrated thattheproposed system obtained theinformation thatwasabletodetermine thegoodordefective situation in soldering. Thissystem istheworld's first CTsystem, whichcanbe introduced into thesoldering line, anditisoperated bymorethan 20domestic andforeign factories now.