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The value of glass frit bonding to assemble silicon parts was demonstrated by the successful evaluation of cryostability of a small multi-piece silicon mirror. This bonding technique has been extended to the assembly of a 44kg block of silicon, 113 x 400 x 400mm. Such an assembly was considered to be a cost competitive alternative to the purchase of a custom sized silicon boule. Various types of evaluation provided the foundation upon which this accomplishment is based. Included were cryocycling of frit bonded plates, comparison of the strength of bonded silicon bend bars with that of silicon bend bars, and the fabrication and cryotest of a small concave frit bonded silicon mirror. Of the 16 bonded bars in two groups only 2 had failures in the bondline, 11 failed in the silicon, and origins could not be determined for 3 bars. The two groups of bonded silicon bars had average strengths that were 84% and 91% of the average strength of the plain silicon bars. In view of the relatively small number of bars in each group this is not surprising. The cryostability of the concave bonded silicon mirror was demonstrated by a figure error of less than 0.06 wave rms at 633nm, cold to warm, compared to a specification of 0.1 wave rms, and 0.014 wave rms, warm to cold to warm, over an 80% clear aperture. These results are reviewed before interesting features of the large block are discussed. Finally, projections are made regarding possible future applications for this bonding process.

Single Crystal Silicon (SCSi) is proving to be an excellent material for the fabrication of lightweight optical components for use in space. As part of the feasibility studies performed prior to space flight applications, it is important to determine the mechanical properties of complex structures manufactured from individual sections of SCSi. As an additional integral building block for future multi-component SCSi structures, the behavior of the McCarter Machine proprietary frit-bonded metal insert technology was examined. Here we report vibration test results, the objective of which was to measure the structural damping characteristics of a typical silicon structure and verify its structural stability after exposure to random vibration. The tests were designed to better understand SCSi, not only as a mirror substrate, but also as a structural material. The success of this test, combined with the already proven McCarter Machine manufacturing techniques, give us the ability to now manufacture new lightweight and stable opto-mechanical assemblies entirely out of SCSi. But since requirements for larger and more sophisticated SCSi structures are limited by the practical size of available boules, the behavior of these frit-bonded SCSi structures needs to be better understood. This understanding will be obtained from planned testing of larger frit bonded SCSi opto-mechanical structural components and assemblies.

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