Cheng Bo, Wang Li, Zhang Qun, Gao Xia, Xie Xiaoming and Wolfgang Kempe
Flip chip on board (FCOB) solder joint reliability under thermal shock stress was investigated. With underfill materials, the solder joint lifetime was increased from 37 to…
Abstract
Flip chip on board (FCOB) solder joint reliability under thermal shock stress was investigated. With underfill materials, the solder joint lifetime was increased from 37 to 1,300/2,480 cycles depending on the particular underfill material used. Through the use of CSAM, SEM, dye penetration tests and cross sectioning, the reliability of a FCOB assembly under thermal shock stress was evaluated. Both dye penetration and SEM fracture analysis can be used to measure quantitatively the extent of crack propagation for assemblies without underfill. A new failure mechanism, PCB cracking was also observed and discussed.
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Zhang Qun, Xie Xiaoming, Chen Liu, Wang Guozhong, Cheng Zhaonian and Wolfgang Kempe
The lifetime of flip chip solder joints can be greatly increased by applying underfill encapsulation. This paper presents a case study where the thermal cycle lifetime was…
Abstract
The lifetime of flip chip solder joints can be greatly increased by applying underfill encapsulation. This paper presents a case study where the thermal cycle lifetime was increased by more than 20 times, that is from ∼100 cycles to more than 2,000 cycles for a chip size of 5.6mm × 6.3mm. By combining electrical, acoustic and metallographic investigation, the degradation of the solder joints was monitored, some important factors relevant to solder joint reliability were analysed and discussed. Delamination was found not to be the dominant failure mode.
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Cheng Bo, Wang Li, Zhang Qun, Gao Xia, Xie Xiaoming and Wolfgang Kempe
Flip chip solder joint reliability under thermal shock stress was investigated both experimentally and by 2D finite element simulation. The results indicate that solder fatigue is…
Abstract
Flip chip solder joint reliability under thermal shock stress was investigated both experimentally and by 2D finite element simulation. The results indicate that solder fatigue is the dominant failure mode and that delamination has obvious adverse effects on the solder joint lifetime. Different material/process combinations (underfill, flux, reflow atmospheres) were designed in order to understand the role of material/process factors on the solder joint lifetime and the results are discussed.
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The purpose of this paper is to review the variation in methods used to analyse lessons in order to improve teaching and learning.
Abstract
Purpose
The purpose of this paper is to review the variation in methods used to analyse lessons in order to improve teaching and learning.
Design/methodology/approach
It addresses the question of how observations of lessons can be analysed, and what approaches and methods are applicable in the analysis of collected data in lesson and learning studies.
Findings
In lesson studies, the focus of research varies, the content and context of lessons vary and a variety of qualitative methods are applied in the analysis of lessons. Lesson study is proving to be a versatile research approach to the development of the quality of teaching and learning.
Originality/value
This review provides an overview of some qualitative methods of content analysis used as analytic tools in the studies presented in this issue of the journal.
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IT is a very encouraging sign to those interested in the welfare of children that so much attention is being bestowed upon them by library authorities. On every side activity is…
Abstract
IT is a very encouraging sign to those interested in the welfare of children that so much attention is being bestowed upon them by library authorities. On every side activity is apparent: most new buildings have a room set aside for the exclusive use of juveniles, and many old buildings are being adapted and special provision made for the young. In these circumstances a brief summary of practical requirements may not come amiss.
IN 1946 there was in the British Isles a clear image of librarianship in most librarians' minds. The image depended on a librarian's professional environment which was of the…
Abstract
IN 1946 there was in the British Isles a clear image of librarianship in most librarians' minds. The image depended on a librarian's professional environment which was of the widest possible range, not less in variation than the organisations, institutes or types of community which required library services. Generalisations are like cocoanuts but they provide for the quickest precipitation of variant definitions, after the stones have been thrown at them. A generalisation might claim that, in 1946, public librarians had in mind an image of a librarian as organiser plus technical specialist or literary critic or book selector; that university and institute librarians projected themselves as scholars of any subject with a special environmental responsibility; that librarians in industry regarded themselves as something less than but as supplementing the capacity of a subject specialist (normally a scientist). Other minor separable categories existed with as many shades of meaning between the three generalised definitions, while librarians of national libraries were too few to be subject to easy generalisation.