High creep resistance rareearth contained tin base leadless soldering-flux and preparation method thereof

Abstract

The present invention relates to a high creep resistance rare earth containing tin base leadless brazing filler metal and its preparation method. Said material contains (wt%) 2-5% of Ag, 0.2-1% of Cu, 0.025-1.0% of commercially-available Ce base mixed rare earth and the rest is Sn. Its preparation method includes the following steps: melting mixed salt of potassium chloride and lithium chloride with weight ratio of 1-1.6:0.8-1.2, pouring it on the Sn, after the Sn is melted, adding the weighed Ag and Cu into Sn solution to melt Ag and Cu, then using bell jar whose wall has hole to press the Ce base rare earth into the above-mentioned mixed salt and Sn-Ag-Cu alloy, turning bell jar, heat-insulating for 1-2 hr., stirring, standing still, setting and removing mixed salt from surface so as toobtain the invented brazing fill metal.

Description

technical field [0001] A rare earth-containing tin-based lead-free solder with high creep resistance and a preparation method thereof belong to the technical field of lead-free solder manufacturing for surface assembly in the microelectronics industry. Background technique [0002] With the rise and wider application of surface mount technology, as well as the ultra-fine pitch design of electronic circuit boards, new lead-free solders are required not only to have good process performance, but more importantly, to have higher Mechanical properties to meet the growing reliability requirements of the electronics industry to ensure reliable operation during service. The mechanical properties of brazed joints are largely affected by their creep deformation behavior. For SnAgCu solder, its melting temperature is roughly between 215°C and 218°C. In this way, even at room temperature, the deformation behavior of the brazed joint belongs to high temperature creep. This higher tem...

AI Technical Summary

Problems solved by technology

However, with the acceleration of the lead-free process, some large companies have successively launched lead-free wave soldering machines and lead-free reflow soldering machines, and the peak temperature of soldering can reach about 250°C. Under the current situation, the problem of melting point of lead-free solder is no longer a very prominent problem

In addition, Bi-containing solder is prone to undercutting defects during brazing, and it is easy to form a low-melting eutectic with lead, so it is more sensitive to lead pollution, and the brittleness of Bi is also an unfavorable factor.

In addition, Bi is a by-product of lead, and the use of Bi-containing solder will inevitably increase the mining of lead ore, causing environmental pollution

The abundance of In in the earth's crust is very low, and it is expensive, not suitable for large-scale use

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