Effect of Thermal Aging on the Microstructure Evolution and Solder Joint Reliability in Hard Disk Drive Under Mechanical Shock

The effect of thermal aging on the microstructure evolution and solder joint reliability in hard disk drive (HDD) under mechanical shock was investigated. Significant coarsening of Ag
₃
Sn particles was found in SnAgCu solder, and AuSn
₄
intermetallic compound (IMC) changed from needle-type to layer-type during aging. For as-soldered SnAgCu solder joints after mechanical shock, the cracks were initiated in AuSn
₄
at the corner of the solder joints, and mainly propagated along the thin Ni
₃
Sn
₄
IMC layer. After aging at 150
^deg
C for 21 days, the cracks were mainly propagated along the solder, Ni
₃
Sn
₄
, Au-Sn-Ni-Cu, and Au-Cu-Sn. The significant coarsening of microstructure was found in SnPb solder joints, and only microcracks were found on the surfaces of as-soldered and aged solder joints after mechanical shock.