Abstract
Abstract There are large amounts of many kinds of solder joints in electronic products. As electronic products feature light、thin、short、small and multi-functional, the sizes of the joints become smaller and smaller, then the density of the joints become higher and higher. Therefore, the reliabilities of the joints have been paid much more attention. Due to a chemical potential difference, atoms moving result in interfacial reaction at a distinct material of the joint. When using electronic products, there would be some electric current passing through electronic packaging joints. Electric current would bring Joule heating effect; it elevates the temperature of solder joints and accelerates the interfacial reaction rate at the joints. With interfacial reactions, intermetallic compounds (IMC) formed at metallic joints usually have less electrical or mechanical properties, so they would damage the joints easily and affect the qualities of the electronic products directly. Consequently, it is an importance issue to research interfacial reactions of the joints in electronic product. Sn is as solder and Co, a common material in UBM, is as substrate in our research. To research Sn/Co ( solid state/ solid state ) interfacial reactions under different reaction temperature：160℃、180℃、200℃. From the results, we found the thickness of intermetallic compound formed at Sn/Co interface increases, when reaction time or reaction temperature increases. The relation between reaction time and IMC thickness is linear at reaction beginnin：it means a reaction-control. Except joule heating effect, it might also induce electromigration effect when electric current passes through metallic materials. Electromigration could induce atom flux, thus influence interfacial reactions. To research Sn/Co interfacial reactions affected by electric current effects, electric current density using in our research is 500A/cm2. Experimental method is entwining Sn/Co reaction couple with electric lines, then linking with power supply and providing need electric current based on cross-section area of reaction couple. From the results, electric current density 500A/cm2 could not induce enough atom flux, so it would not influence the growth of IMC thickness. Since electric current effects could induce atom flux, furthermore, electric field and magnetic field are coexisted, so magnetic effect might also induce atom flux. However, there are fewer literatures about the magnetic effect upon interfacial reactions. To research Sn/Co interfacial reactions affected by magnetic field, the magnetic field source in our research is produced by permanent magnet. Experimental method is carried out in In-situ way, so replace high-temperature oven with hot plate to control reaction temperatures. Permanent magnet in our research is preferred to Samarium-Cobalt magnet, because it is characterized as high-working temperature and high-performance. As the results show, the magnitude of magnetic field in our research is not enough to induce atom flux, thus it would not influence the growth of IMC thickness. Moreover, the kinds of IMC phase formed at the interfaces and the interface morphology are not influenced by magnetic field.