{'fraction_non_alphanumeric': 0.02034618888551473, 'fraction_numerical': 0.00850288490737929, 'mean_word_length': 5.088724584103512, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Special features of the technology of low-temperature brazing of optical modules

At present, low-temperature brazing is used extensively in the production of radioelectronic components. This method satisfies most efficiently the technical requirements in this application. In this work, investigations are carried out into the special features of the technology of low-temperature brazing of optical modules, used as optical sensors of different measuring devices and systems. The special feature of brazing the optical module (Fig. 1) is to ensure the required position of the contact sheet and the substrate. The quality of assembling is determined by the accuracy of adjustment of the active element and the fibre optics lens. In the case of unsatisfactory assembly, determined by the mismatch of the input electrical signal, supplied to electrical conductors, and the output signal, taken from the fibre optics lens, the section is repaired by brazing. The contact sheet and the substrate of the optical module are produced from 29NK Kovar alloy (GOST 1099474) with the deposition of a processing gold coating, 2.5 μm thick. In the given technology, the brazed elements are heated using a thermal resistance, brazed in advance to the base. The service conditions of the optical module are characterised by sharp variations of the working temperature at a rate of up to 10 oC/s. Therefore, the brazed section is subject to special requirements on the efficiency (strength lower than 30 MPa) with the variation of the working temperature in the range from –55 to 85 oC. Since, according to the fabrication conditions of the component, the brazing temperature should not exceed 120 oC, brazing is carried out using brazing alloys with a very low melting point represented by eutectic-type alloys based on bismuth ROZE and No. 219. The absence of the solidification range in these alloys results in the minimum deformation of the structure during brazing. The brazing alloys of this type are characterised by active diffusion interaction with the metal of the coating resulting in the dissolution of the coating, formation of intermetallic compounds in the brazing zone, changes in the thermophysical properties of the molten brazing alloy and, consequently, a restriction of the number of times of repairing the brazed joint (no more than 3–4) in the case of unsatisfactory adjustment of the elements of the optical module, and the level of rejects also increases. To solve the problem, investigations were carried out to develop a new multicomponent composition of eutectictype brazing alloys with very low melting points. The development of the compositions of the brazing alloys and examination of special features of the diffusion interaction of the coating and metals, included in the composition of the brazing alloys with very low melting points, were carried out using Au–Bi, Au–Sn, Au–Cd, Au–Pb binary equilibrium diagrams. Analysis of these diagrams shows that the nature of chemical interaction of the metal of the coating with the elements of the composition has a number of identical features. Gold is characterised by rapid dissolution in all these metals forming low-melting eutectics with them. Special features of the technology of low-temperature brazing of optical modules