Please use this identifier to cite or link to this item: http://hdl.handle.net/1783.1/5964

Experimental and numerical study of solder ball joints' reliability at package level & board level

Authors Xu, Zhengjian
Issue Date 2009
Summary The reliability under impact loading is one of the major concerns for portable electronic products. With the development of Surface-mount Technology (SMT), the reliability of solder ball joints is a critical issue since the whole device may be losing functions or failed by disconnection of one single solder ball joint between a chip and a PCB. To mimic the real dropping, drop tests are usually used to study the dynamic response of Printed Circuit Board (PCB) as well as the reliability of the solder ball joints in laboratory. In the present thesis, the dynamic responses of the PCB and solder joints are studied by both experiments and Finite Element Method (FEM) simulations with various impact orientations. Although board level drop test is one of the most useful experiment methods to examine the reliability of solder joints for assembly quality, it is very time consuming. To accelerate the test time for solder joint reliability test, many technologies and tools such as the package level shear/pull tests machines were developed in design and process characterization area. Both the high speed ball shear and pull tests are simulated by ABAQUSTM in the present thesis. Noticed that the strain rates of solder joints in high speed solder ball shear/pull tests are very high, the dynamic properties of the lead free solder alloys (SAC105 & LF35) are tested by the mini Split Hopkinson Tensile Bar (mSHTB) technique. The lead free solder alloys are found highly rate dependent. Some important aspects (e.g. IMC property, strain rate effect) which may influence the failure mode of the solder joint are discussed. By comparing between the board level reliability test technology and the package level reliability test technology, some differences are discussed with evidence on the strain rates, the stress/strain distribution etc. of the solder joints. With the comparison, a new single solder ball peeling test method is proposed. Some conclusions are drawn at the end of the thesis, and several criterions are proposed to the industry.
Note Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2009
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Language English
Format Thesis
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