Malik, Asif (2014) OPISA optoelectronics packaging interfaces for sub-micron alignment. PhD thesis, University of Greenwich.

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Abstract

For optoelectronic devices submicron precision is required to optimally couple the laser source with the optical fibre. Laser welding is used because of its inherent attributes of accuracy, strength, cleanliness and minimised heat affected zone and structural changes. Due to the rapid solidification of the welded parts post welding residual stresses occur which can lead to a post weld shift between the aligned components and can significantly reduce the light coupling efficiency. Submicron misalignment induced due to the welding process can result in significant power loss. This is a serious and common issue in the manufacture of optoelectronic components and affects production rates.

The aim of this work is the development of a methodology that can estimate the residual stresses in the weld piece and to optimise the process by locating the optimal site for micro laser welding. The aim establishes the research question which was addressed by nine objectives. The first eight objectives are elements that comprise the Optoelectronic Packaging Interfaces for Sub-Micron Alignment (OPISA) project. The final objective is the dissemination of this work.

Finite element models were developed and used with design of experiments (DoE) statistical technique. This was used to investigate how the key process parameters influence the resultant stress in the optical fibre and to develop a predictive surrogate model. The surrogate model was used with Monte Carlo simulations to determine the fibre stress variation when uncertainty and variation of the design variables are accounted for. The Monte Carlo simulations predicted fibre stress response values which were used to understand how the uncertainties of the input design variables propagate into uncertainty and variation of fibre stress. The surrogate model was used in a sensitivity and risk analysis. The capability analysis of the welding process was also investigated.

The original finding of this work is the development of a methodology that fulfils the aim. The work successfully demonstrated that the current industry weld spot location generate 180MPa of post weld stress in the optical fibre. Using the OPISA methodology the optimal weld locations generate 57.6MPa of post weld stress in the optical fibre.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	optoelectronics; laser welding process; surrogate modelling; thermomechanics;
Subjects:	Q Science > QC Physics T Technology > TK Electrical engineering. Electronics Nuclear engineering
Pre-2014 Departments:	School of Computing & Mathematical Sciences School of Computing & Mathematical Sciences > Department of Mathematical Sciences
Last Modified:	23 Nov 2017 17:22
URI:	http://gala.gre.ac.uk/id/eprint/18142

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