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Proceedings Paper

Low-strain laser-based solder joining of mounted lenses
Author(s): Thomas Burkhardt; Marcel Hornaff; Andreas Kamm; Diana Burkhardt; Erik Schmidt; Erik Beckert; Ramona Eberhardt; Andreas Tünnermann
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Paper Abstract

A novel laser-based soldering technique – Solderjet Bumping – using liquid solder droplets in a flux-free process with only localized heating is presented. We demonstrate an all inorganic, adhesive free bonding of optical components and support structures suitable for optical assemblies and instruments under harsh environmental conditions. Low strain bonding suitable for a following high-precision adjustment turning process is presented, addressing components and subsystems for objectives for high power and short wavelengths. The discussed case study shows large aperture transmissive optics (diameter approx. 74 mm and 50 mm) made of fused silica and LAK9G15, a radiation resistant glass, bonded to thermally matched metallic mounts. The process chain of Solderjet Bumping – cleaning, solderable metallization, handling, bonding and inspection – is discussed. This multi-material approach requires numerical modelling for dimensioning according to thermal and mechanical loads. The findings of numerical modelling, process parametrization and environmental testing (thermal and vibrational loads) are presented. Stress and strain introduced into optical components as well as deformation of optical surfaces can significantly deteriorate the wave front of passing light and therefore reduce system performance significantly. The optical performance with respect to stress/strain and surface deformation during bonding and environmental testing were evaluated using noncontact and nondestructive optical techniques: polarimetry and interferometry, respectively. Stress induced surface deformation of less than 100 nm and changes in optical path difference below 5 nm were achieved. Bond strengths of about 55 MPa are reported using tin-silver-copper soft solder alloy.

Paper Details

Date Published: 2 September 2015
PDF: 14 pages
Proc. SPIE 9574, Material Technologies and Applications to Optics, Structures, Components, and Sub-Systems II, 95740M (2 September 2015); doi: 10.1117/12.2186747
Show Author Affiliations
Thomas Burkhardt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Marcel Hornaff, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Andreas Kamm, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Diana Burkhardt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Numerik Jena GmbH (Germany)
Erik Schmidt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Erik Beckert, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Ramona Eberhardt, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Andreas Tünnermann, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Friedrich-Schiller Univ. Jena (Germany)


Published in SPIE Proceedings Vol. 9574:
Material Technologies and Applications to Optics, Structures, Components, and Sub-Systems II
Matthias Krödel; Joseph L. Robichaud; William A. Goodman, Editor(s)

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