25 October 2016 Picosecond laser bonding of highly dissimilar materials
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We report on recent progress in developing an industrially relevant, robust technique to bond dissimilar materials through ultra-fast microwelding. This technique is based on the use of a 5.9ps, 400kHz Trumpf laser operating at 1030nm. Tight focusing of the laser radiation at, or around, the interface between two materials allows for simultaneous absorption in both. This absorption rapidly, and locally, heats the material forming plasma from both materials. With suitable surface preparation this plasma can be confined to the interface region where it mixes, cools and forms a weld between the two materials.

The use of ps pulses results in a short interaction time. This enables a bond to form whilst limiting the heat affected zone (HAZ) to a region of only a few hundred micrometres across. This small scale allows for the bonding of materials with highly dissimilar thermal properties, and in particular coefficients of thermal expansion e.g. glass-metal bonding.

We report on our results for a range of material combinations including, Al-Bk7, Al-SiO2 and Nd:YAG-AlSi. Emphasis will be laid on the technical requirements for bonding including the required surface preparation of the two materials and on the laser parameters required. The quality of the resultant bonds are characterized through shear force measurements (where strengths equal to and exceeding equivalent adhesives will be presented). The lifetime of the welds is also discussed, paying particular attention to the results of thermal cycling tests.
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Richard M. Carter, Richard M. Carter, Michael Troughton, Michael Troughton, Jianyong Chen, Jianyong Chen, Ian Elder, Ian Elder, Robert R. Thomson, Robert R. Thomson, Robert A. Lamb, Robert A. Lamb, M. J. Daniel Esser, M. J. Daniel Esser, Duncan P. Hand, Duncan P. Hand, } "Picosecond laser bonding of highly dissimilar materials", Proc. SPIE 9992, Emerging Imaging and Sensing Technologies, 999207 (25 October 2016); doi: 10.1117/12.2242039; https://doi.org/10.1117/12.2242039

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