Melting-point-changeable lead-free composite soldering material, soldering paste, thire preparation and use

Abstract

The invention discloses a variable melting point lead-free composite solder and solder paste as well as preparation and application methods thereof, belonging to the technical field of composite lead-free solder / paste manufacture. The solder / paste is prepared by mechanical mixing of two general-purpose solder powders and fluxes with different melting points. The composite solder / paste has the advantages of strong anti-collapse ability, high hardness and toughness, long service life, bright solder joint halo, simple and easy preparation process, etc. during welding and use. It is not necessary to change the welding process route and parameters of the original lead-containing solder, and it can realize low-temperature welding of medium / high temperature solder or gradient temperature welding, so as to realize the medium / high temperature application of low-temperature solder and prolong the service life.

Description

technical field [0001] The invention relates to a lead-free composite solder and solder paste and a preparation and application method thereof. The composite solder is a mechanical mixture of two solder powders with good compatibility and wettability in the soldering process, and belongs to the technical field of tin-based lead-free solder / paste manufacture. Background technique [0002] Emphasizing environmental protection and advocating green products are the general trend of economic development in the world today, and lead-free electronic products are one of the major measures. The currently applied patents on lead-free solder can be said to be overwhelming, mainly occupied by countries such as Japan, the United States, and the European Union. However, the research on lead-free technology for electronic products in my country started relatively late, and commercial lead-free electronics with independent intellectual property rights There are very few products. In order t...

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Problems solved by technology

[0004] U.S. Patent 6,360,939B1 discloses a method of manufacturing lead-free solder paste in the electronics industry, the solder paste has a basic solder powder and an added metal powder component that does not melt during soldering, the melting point of the added powder is higher than that of the basic solder The melting point of the powder is much higher, the basic solder powder includes 80-90% Sn and 1-20% Ag, and the added powder metal is selected from metal components including Sn, Ni, Cu, Ag and Bi and other mixtures; Akron University, USA Researchers in Sn-Pb solder have significantly improved the strength of solder joints by adding nanoparticles of copper or titanium oxide; IBM has prepared composite solder by adding nanoparticles of molybdenum and tantalum. Chinese patent CN 1672858A discloses that it contains memory alloy particles tin-silver solder; Chinese patent CN 1672859A discloses tin-silver solder containing nano-sized zirconia particles and its preparation method; the strengthened particles of these published solders are in a completely non-melting state during the soldering process, and the main reason is that the composite solder The gap between the melting points of the two basic raw material powders is too large, and the high melting point components actually exist in the form of independent particles during the welding process. Although the strength performance can be improved to a certain extent, the welding defect rate will increase, thus affecting welding. point of reliability

In the composite solder disclosed in US 2002 / 0040624A1 and CN 1732063A, both components are molten during the soldering process, but the melting point difference between the two components is required to be less than 15°C in the composite solder involved. There is no anti-collapse ability, and it has no obvious effect on reducing bridging and short circuit; the University of Waterloo, Canada also has a research report on the special welding of pure Sn and pure Sb powder mixed powder solder paste, but only pure simple powder is involved, and its welding High temperature increases the difficulty of welding process

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