A kind of preparation of low temperature active solder and brazing method

Abstract

A preparation and brazing method of low-temperature active solder, the steps are as follows: surface treatment of foam metal; preparation of a suspension electroplating solution containing active metal powder; ultrasonic-assisted electroplating of a composite coating on the surface of the foam metal, after ultrasonic cleaning and drying forming an alloy skeleton; sintering at a high temperature to obtain an active alloy foam skeleton; obtaining a composite solder with a low melting point solder filling the skeleton gap by dipping; and alternating cold and heat to obtain a metal solder foil. The invention obtains a composite coating layer with uniform distribution of active elements through ultrasonic-assisted composite deposition, and the content of active elements obtains a wide adjustment range with current density and electroplating time; at the same time, the oxidation of active elements in the subsequent process is suppressed, which is beneficial to negative pressure Interstitial filling of low-temperature solder during infiltration; solves the problem of segregation of active elements in low-temperature solder.

Description

technical field [0001] The invention relates to a preparation method of low-temperature active solder, in particular to a preparation and brazing method of low-temperature active solder. Background technique [0002] Aluminum alloys are widely used in aerospace, waveguide antennas and printed circuits due to their high specific strength, electrical conductivity, heat dissipation, and good corrosion resistance. However, the high temperature softening characteristics of aluminum alloys and the difficult wettability of the dense aluminum oxide film on the surface bring difficulties to the connection of aluminum alloys. Based on the comprehensive consideration of environmental protection and connection strength, the most studied low-temperature joining technologies for aluminum alloys mainly include ultrasonic-assisted brazing and low-temperature active brazing. Among them, ultrasonic-assisted brazing cannot achieve high-precision or large fusion surface aluminum alloy connecti...

AI Technical Summary

Problems solved by technology

Adding active elements directly to the solder has the following problems: when the content of active elements decreases, the improvement of interfacial wetting is not obvious, and the strength of the joint is low; while the content of active elements is too high, a large number of compounds are generated and easy to segregate, resulting in instability of the joint structure, Inhomogeneous active reaction at the upper and lower interfaces

However, due to the chemical characteristics of the active elements, active metals are usually unable to be electroplated in aqueous solution, and can only be formed by molten salt electroplating, sputter deposition or spray coating.

Sputtering deposition and spraying methods often can only obtain deposition layers on the exposed upper and lower surfaces of metal foam, and cannot obtain a uniform coating on the surface of the network structure in the pores

In addition, due to the high oxidizing properties of active elements, the active elements in the resulting coating tend to be rapidly oxidized in subsequent processes, affecting the wetting during soldering.

[0005] Existing electroplating technologies also have their own shortcomings. For example, Chinese patent CN105862092A discloses an electroplating solution for alkaline electroplating copper-titanium alloy and its preparation method. This method has defects such as complex components of the plating solution and cumbersome operation steps, and due to Ti ion The reduction potential is low, a large amount of hydrogen will be evolved on the electrode, and there will be little titanium deposition

Chinese patent CN103320822A discloses a method for electroplating titanium with molten salt. This method has the defect that the electroplating temperature is too high, and the melting point of the foam metal is required to be higher than 600°C, and the active elements are easily oxidized at high temperatures.

Chinese patent CN110983323A discloses an accelerator for mechanochemical deposition of titanium powder, but this patent requires the addition of industrial concentrated sulfuric acid or hydrofluoric acid, which pollutes the environment greatly, and will cause damage to the foamed metal during the mechanochemical deposition process, which will affect the strength of the solder. unfavorable

In summary, the existing electroplating technology has the following defects: 1) The content of active elements in the coating is small, which cannot meet the needs of low-temperature active brazing; 2) The electroplating temperature is high, the active elements are easy to oxidize, and the requirements for equipment conditions are high; 3) It will damage the foamed metal components and be detrimental to the strength of the solder; 4) The phenomenon of particle agglomeration in the composite plating process is unavoidable

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