Production Technique And Technics Study Of Solder Balls Used By The High Integrated Package

Electronic products have been developing to portable type, miniaturization, networking and multimediafication. The high integrated package technology of electronic products is demanded higher and higher. BGA (Ball Grid Array) package is one of the most advancing and mature surface package methods using solder balls to replace the down-lead of the packaging configuration in the IC component. The solder ball is the key material of the bump fabrication in the BGA andμBGA high integrated package. The small solder balls are used to form both the signal transmission path and the mechanical connections between the chip and the printed circuit board (PCB) in BGA package.According to the theory and process of fabricating solder ball by fine wire cutting–remelting method, an equipment manufacturing solder balls, which is made up of automation cutting equipment, preheating system, remelting spheroidization system, cooling system, control system and collecting system was designed. Analyzing the functions and action principles of every components and regulating cutting equipment, all kinds of solder balls can been produced by the equipment.The influence of the nodulizer types, preheating temperatures and spheroidization temperatures on real sphericity and surface appearance of the solder balls are investigated. Results show that the real sphericity of the 63Sn37Pb solder balls is the maximum and the surface quality of the solder balls is the best when the arachis oil is used as the nodulizer. That is to say, the spheroidization effect of arachis oil is the best, followed by silicone oil ,heavy oil, and engine oil. And the real sphericity and surface appearance of BGA solder balls become better and better along with the preheating temperature incrementing. While the temperature hoist from 500℃to 600℃, the quality of solder balls hardly improve. When the spheroidization temperature is 300℃, the quality of solder balls are best. So the optimization technological parameter by the wire cutting–remelting mothod to make solder balls is as follows: when 63Sn37Pb eutectic solder is used as raw material, the arachis oil is chosed as the nodulizer, the preheating temperature and spheroidization temperature is respectively about 500℃and 300℃.According to jet instability theory, solder balls production installation is designed and a prototype is developed. This installation is composed of a melting system, a pressure controlling system, a vibration system and a cooling and collecting system. Vibration system is the important component, which consists of a frequency variable power, a vibratile eccentric and a vibration linkage. The frequency variable power can regulate frequency and electric current. Vibratile eccentric realizes the control of swing of vibration.When the experimental conditions are that 63Sn37Pb solder wire is used as raw material, that arachis oil is used as the nodulizer, that the diameter of nozzle preparatory chosen is 0.2mm, and that spheroidization temperature is 300℃, solder balls are manufactured. The influences of vibration frequencies, jet pressures and melting temperatures of solder on the diameters of the solder balls are studied. Results show that the diameters of the solder balls become smaller and smaller with the vibration frequency hoisting from 400Hz to 1200Hz when the melting temperature of solder and jet pressure are fixed values. In the same way, when the melting temperature of solder and the excitation frequency are fixed, the diameters of the solder balls become larger when the jet pressure increase from 0.3MPa to 0.7MPa. While the jet pressure and excitation frequency are fixed, the jetting liquid rupture length becomes long when the melting temperature of solder increases from 190℃～230℃. So reducing the melting temperatures or jet pressures, and increasing the vibration frequency are propitious to jetting liquid rupture equably. The diameters of the solder balls become smaller and smaller, and the quality of solder balls become better and better. According to the influencing discipline of technological parameter, solder balls of various specifications can be made by selecting optimal melting temperature, jet pressure, vibration frequency and spheroidization circumstances.