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Flexible printed circuit (FPC) is extensively used in portable electronic products because of its excellent flexibility and twistability. Compared with rigid boards, FPC usually experiences much larger deformation in its usages. However, most available packaging-components at the moment are rigid, FPC-contained products may cause failures under accidental mechanical conditions, such as drop, bending...
In this paper, the mechanical performance of solder joints of BGA mounted on flexible printed circuit (FPC) was studied using finite element method (FEM). To optimize the electric components layout during the design, it is necessary to predict the bending reliability of components on FPC. Traditionally, 3-point or 4-point bending are common used to study if the substrate is rigid. In order to simulate...
To enhance the ability of lead-free solder joint to resist failures induced by mechanical impact and shock, some researchers have introduced low-Ag lead-free solder. In this study, the formation and evolution of IMC, the fracture morphology and performance of solder joint between SAC 105 solder and Under Bump Metallization (UBM) have been studied after different temperature storage aging and multi-reflow...
This paper first examines the commonly-used thermal-moisture analogy approach in thermal-moisture analogy approach. We conclude that such an analogy using a normalized concentration approach does not exist in the case of soldering reflow, when the solubility of each diffusing material varies with temperature or the saturated moisture concentration is not a constant over an entire range of reflow temperatures...
Underfill is a highly particle filled epoxy polymer used in flip chip to fill the gap between the leadframe and die or between die and die. In order to be able to flow in the thin gap, the silica filler particle must have a diameter below 10 mum. This epoxy underfill material mechanically couples the chip and substrate and decreases the stress in the solder joints, therefore enhancing solder fatigue...
A common failure during the lifetime of most mobile devices is failure through dropping. This is nowadays tested by means of the drop impact test, which has been standardized by JEDEC. This method however takes quite some time and has some problems regarding reproducibility. This paper reports the work done on correlating the drop impact test with the cold bump pull that might be a replacement. The...
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