This paper presents the drop test reliability of 0.5mm pitch lead-free chip scale packages (CSPs). Fifteen 0.5mm pitch CSPs were assembled on a standard JEDEC drop reliability test board with Sn3.0Ag0.5Cu lead-free solder. Eight boards were edge-bonded with a UV-cured acrylic; eight boards were edgebonded with a thermal-cured epoxy; and twelve boards were assembled without edge bonding. Half of the edge-bonded test boards were subjected to drop tests at a peak acceleration of 1500G with a pulse duration of 0.5ms, and the other half subjected to drop tests at a peak acceleration of 2900G with a pulse duration of 0.3ms. Half of the test boards without edge bonding were subjected to drop tests at a peak acceleration of 900G with a pulse duration of 0.7ms, and the other half subjected to drop tests at a peak acceleration of 1500G with a pulse duration of 0.5ms. Two drop test failure detection systems were used in this study to monitor the failure of solder joints: a high-speed resistance measurement system and a post-drop static resistance measurement system. The high-speed resistance measurement system, which has a scan frequency of 50KHz and a 16-bit signal width, is able to detect intermittent failures during the short drop impact duration. Statistics of the number of drops to failure for the 15 component locations on each test board are reported. The effect of component position on drop test reliability is discussed. The test results show that the drop test performance of edge-bonded CSPs is five to eight times better than the CSPs without edge bonding. However, the drop test reliability of edge-bonded CSPs with the thermal-cured epoxy is different from that with edge-bonded CSPs with the UV-cured acrylic. The solder crack location and crack area are characterized with the dye penetrant method. The fracture surfaces are studied using scanning electron microscopy (SEM).
-The curriculum for undergraduate engineering programs is often partitioned into several courses that are taught in isolation followed by a single culminating senior design or capstone project experience. In the senior design class students begin to synthesize the knowledge and skills that they acquired through the engineering curriculum. This paper presents lower and upper division course and curricular changes made to accommodate learning objectives that better prepare students for project-based learning. These learning experiences and skills include: systems level design, experience with state-of-the art Computer Aided Design (CAD) tools, printed circuit board (PBC) design, design for manufacturability, electronics assembly, project management, engineering ethics, and communication skills. Three upper division project based learning courses have been developed and are being offered this year.In addition, the development of laboratory tutorials and learning modules for the lower division engineering curriculum will introduce all engineering majors to current electronic manufacturing technology, and allow them to design electronic systems using PCBs. The courses and tutorial learning modules are currently being classroom tested and assessed.
Undergraduate computer and electrical engineering programs often partition the curriculum into several courses based on related topics taught in isolation. Students are expected to synthesize their knowledge in a senior design project. It is the authors' experience that students often struggle during their senior design project since they have not gained the appropriate knowledge or mastered necessary skills needed to work on a significant or team-based engineering design project. Specifically, students need to be able to define system requirements, partition the design into subcomponents, design, build, test, and verify that the system requirements have been met. The authors have enhanced and implemented three courses to develop system engineering knowledge and skills that better prepare students for their senior design experience. This paper gives an overview and lists the learning outcomes for each of these courses and includes some examples of laboratory projects that are used to meet these learning outcomes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.