Low-strain laser-based solder joining of mounted lenses

Thomas Burkhardt; Marcel Hornaff; Andreas Kamm; Diana Burkhardt; Erik Schmidt; Erik Beckert; Ramona Eberhardt; Andreas Tünnermann

doi:10.1117/12.2186747

2 September 2015 Low-strain laser-based solder joining of mounted lenses

Thomas Burkhardt, Marcel Hornaff, Andreas Kamm, Diana Burkhardt, Erik Schmidt, Erik Beckert, Ramona Eberhardt, Andreas Tünnermann

Author Affiliations +

Proceedings Volume 9574, Material Technologies and Applications to Optics, Structures, Components, and Sub-Systems II; 95740M (2015) https://doi.org/10.1117/12.2186747
Event: SPIE Optical Engineering + Applications, 2015, San Diego, California, United States

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.

Citation Download Citation

Thomas Burkhardt, Marcel Hornaff, Andreas Kamm, Diana Burkhardt, Erik Schmidt, Erik Beckert, Ramona Eberhardt, and Andreas Tünnermann "Low-strain laser-based solder joining of mounted lenses", Proc. SPIE 9574, Material Technologies and Applications to Optics, Structures, Components, and Sub-Systems II, 95740M (2 September 2015); https://doi.org/10.1117/12.2186747

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