Failure mechanism of FBGA solder joints in memory module subjected to harmonic excitation

Effect of solder pads on the fatigue life of FBGA memory modules under harmonic excitation by using a global–local modeling technique

“…x s is the starting frequency, S is the sweep rate in decades per minute (defined as one decade/minute in JEDEC service condition 1), and b represents phase. Forced vibration analysis was performed around the first natural frequency because prior research [16] showed that the first mode is the most destructive mode up to 2 kHz.…”

“…7 are the most failed packages due to the relative displacement as explained in reference [16]; therefore, the local model was analyzed for one of these packages (P13), and its symmetric package (P31) shown in Fig. 2 by substituting displacement variation along its cut boundary in order to detect vulnerable parts of solder joints under vibration.…”

“…Relative displacement between PCB and package under vibration is the main source of deformation which causes stress to increase [16]. Since stress due to relative deformation was concentrated at the interface between the solder ball and pad near the PCB as shown in Fig.…”

“…The total resistance of the memory module daisy chain was measured to be around 35-40 Ohm. A failure of the solder joint is assumed to occur when the total resistance is greater than 100 Ohm [16,25]. The experimental setup shown in Fig.…”

“…Their simulation results showed that solder joints with larger diameter and smaller height have improved reliability. Cinar et al [16] also investigated failure mechanisms of FBGA solder joints of memory modules under harmonic excitation. They showed that failure occurs due to the relative displacement between the PCB and package, and the most vulnerable part of the memory module under vibration was found to be the solder joint near the PCB.…”