Abstract
In this paper, drop reliability of various PBA (printed board assembly) mounting structures is investigated and compared. Then, we built SAC305 (Sn3.0Ag0.5Cu) interconnects for BGA (ball grid array) package failure model to evaluate the drop impact reliability of handheld devices. In order to simulate actual behavior of the solder joint under the drop impact load of handheld devices, we perform explicit full FEA (finite element analysis) modeling. However, this takes a lot of computing time because of the large aspect ratio of element size between solder joints and other structures such as PCB (printed circuit board) and electronic packages. Therefore, an effective way to represent solder interconnects for FEA is needed which would be relatively simpler yet detailed. Comparable board-level drop tests are conducted after equipping test vehicles with various fixtures considering PBA mounting structures, which make it possible to apply different loading conditions to BGA packages. The results show different drop impact life for solder interconnects depending on the mounting design of the PBA. Particularly, the solder interconnect of the component located at the middle of the PCB exhibits the shortest impact life where the highest tensile stress occurs. Also, the mounting design restraining PBA deflections shows better reliability under the drop impact loading. Sequentially, simulating with a PBA composed of the BGA package and the PCB is considered to assess the feasibility of the solder ball failure modeling when the drop impact load is applied. Especially, for the modeling of the solder balls, detailed solid model and simple beam model are compared regarding computational efficiency and numerical accuracy. We found that the simple beam model significantly shortens computational time from 110 h to less than an hour. Accordingly, the feasibility of the beam model for the solder balls is shown by correlating the stress level and the drop impact life obtained from the experiments.
Highlights
Because of the slim design, handheld devices are becoming more vulnerable in case of the drop
printed board assembly (PBA) experiencing the maximum manufacturers as it relates to the stress causing the failure of the solder joints
Manufacturers it relates to table the stress causing failure of the joints.atItthe is intervals commonly deflection rightas after the shock hits the strike the surface. These datasolder were taken of the thinner the PCB with higher PCB deflection, the shorter is the impact life of the package, meaning assumed, the thinner the PCB with higher PCB deflection, the shorter is the impact life of the package, the higher stress in the solder joints
Summary
Because of the slim design, handheld devices are becoming more vulnerable in case of the drop. As electronic packages are getting thinner, drop and vibration reliability concerns become increasingly more important [1,2,3,4,5]. Interconnection structures of the IC (integrated circuit) packages are sensitive to drop impact conditions when PCB thickness is reduced. Modern design tends to minimize the number of screws used to mount these slim PBA for reasons of cost-effectiveness of the assembly process. IC package lifetime should assessed in theindevelopment stage of Drop the mobile product. IC package lifetime should be assessed in the development stage of the mobile product
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