Aws takes 450℃ as the dividing line and stipulates that brazing when the liquid phase temperature of solder is higher than 450℃ is called hard brazing and brazing when it is lower than 450℃ is called soft brazing.This division is generally accepted by most people in the world, but there are some different views. For example, the us military standard MILSPEC USES 429℃ (8000F) as the dividing line.In addition, some people who are engaged in electronic product brazing believe that brazing below 315℃ (6000F) is called soft brazing.

In fact, in the electronics industry, most brazing is completed below 300℃, while brazing joints above 450℃ are relatively rare in the electronics industry.Soft brazing technology in electronics industry is obviously different from traditional welding.In terms of materials, it is in sharp contrast to the situation that the traditional welding technology involves ferrous metals dominated by iron. The materials connected in the electronics industry are non-ferrous metals with various types, which often involve precious metals, rare metals and multi-alloy multi-layer metal combination system.In addition, the connection problem of non-metallic materials is often involved. Due to the diversity of the connected objects, the materials used to complete the connection (solder, etc.) also show the characteristics of various types and complex composition.From the dimension feature of the connected object, the most striking feature of the connected object is its fineness.For example: many solder joints are much smaller than 1MM2 in size, the object of the link may be less than 0.1mm bump and thickness of only a few microns of metal coating: solder and solder spacing from 1MM2 to a dozen microns.And.With the demand of electronic products miniaturization, lightweight, high precision and high reliability, the size of the connected object is still decreasing.At the same time, with the rapid development of electronic packaging and assembly technology, chip level chip level assembly level system level technology has begun to be used in packaging and assembly level.As a result, soft brazing technology has been applied to all levels of packaging and interconnection from wafer to electronic products.

Modern is will have entered the electronic technology as the core of the information age, with the electronic products into thousands of households, and even everyone will take several, dozens of integrated circuit products, such as watches, mobile phones all kinds of IC card U disk MP3 PDA

Intelligent toys, electronic keys, etc. All these require electronic products to be smaller, lighter, more functional, faster, more safe and reliable, thus promoting the development of microelectronic packaging technology, promoting the development of electronic packaging to high-density multifunction and lead-free, and the trend of the emergence of new electronic packaging technology:Such as solder ball array (BGA) chip size package (GSP) flip chip chip directly paste wafer level packaging system level packaging more three-dimensional stack chips encapsulation multichip module encapsulation and optoelectronic packaging to satisfy the needs of the various special electronics, high voltage and high power device encapsulating rf microwave devices encapsulation, mems packaging, electronic packaging to the development of the high integration density, impels the solder joint is more and more small bearing mechanics, thermal, electrical load more and more high, so in the process of encapsulation reliability caused by the soft soldering research is particularly important.In addition, with the enhancement of environmental protection awareness and the deepening of lead poisoning awareness, the development of lead-free solder and the reliability of solder joints are one of the most prominent problems caused by the change of packaging solder and packaging technology in the process of excessive lead-free welding.