The Mechanical Reliability Of Fbga Module Mounted On Fpc

The flexible printed circuit, which is made of polyester film or polyimide, is considered to be high-reliable, and super-bendable and is extensively used in lip/slider cell phones. During their service life, cell phones are often bent or twisted. Moreover, they may fall onto the ground because of negligence of users, such that cause repeated impacts. The solder joints can not absorb all stress caused by the deformation of the FPC because they have much higher rigidity than the FPC, such that shortens the life of a cell phone. In this paper, we investigated the connection performance of a FBGA mounted on an FPC. Drop impact, bending and twisting simulation were conducted. The whole work was carried out as follows:(1) Based on the principle of minimum energy, the geometric shape of the BGA solder joint was built by Surface Evolver, and then was imported into the software code Hypermesh, to establish its 3-D finite element model.(2) By the help of FEA software code ABAQUS, studied the connection performance of solder joints under free-fall drop impact and very large-amplitude bending and twisting deformation respectively. High strain rate dependence of materials is included by conducted the Johnson-Cook constitutive.(3) Conducted orthogonal experiments to study the stress states of the componets under 3 different factors.The results show that, (1) the strain rates of the solder joints under drop impact are almost less than 1000/s; the FPC's drop angle and contact mode have key effects on the performance on the reliability of the solder joints; (2) when the FPC is bent down/up, the reliability of the solder joints can be improved by lengthening the FPC; (3) when the FPC is twist into a certain angle, the FBGA's location have significant effects on the reliability of the solder joints;(4) confirmed that experiment method is the largest influence and the most obvious factor.In this paper, the mechanical reliability of a FBGA mounted on an FPC under drop impact, bending and twisting loads was researched respectively by simulation. The effects of the drop mode, FPC length and solder joints'size were investigated. The research results can be used as guidance during design.