Development Of Halogen-free Flux Used For Lead-free Solder Wire

Currently, lead-free electronic products is the inevitable developing trend in the green electronics manufacturing fields, there are still some difficulties in application and promotion of lead-free soldering. Traditional flux can not meet with the requirement of lead-free soldering because lead-free solder alloys have some defects such as lower wetting ability, higher melting point and lower oxidation resistance.In this thesis, the halogen-free type solid flux was investigated and the spreading area was used as the evaluation index. Also the principle of flux formulations and ingredients for corded solder wire were discussed. The activator, carrier and surfactant were obtained. An excellent flux used for cored solder wire was prepared. The method of using different organic matter to compound was brought forward firstly, and then it was used to choose out the activator, carrier and surfactant.The results of the corrosion weight loss experiments, the surface insulation resistance test and the rate of spatter test showed that using adipic acid and sebacic acid as mixture activators, stearic acid, rosin and polyethylene glycol as carriers was a good choice. The mixture of sodium lauryl sulfate, CTAB and OP-10 was chosen as the surfactant.The spreading experiments of activator showed that the spreading area and the wetting ability were the best when the proportion of adipic acid and sebacic acid was 4:1. The result of the Orthogonal Experiment showed that the flux had the best wet ability when the proportion of steatic acid, rosin and PEG was 2:1:2.The result also shows that the CTAB had the greatest impact on the wet ability. The spreading area was bigger when the flux contained more CTAB. The surfactant was considered to be optimized because CTAB contained halogen. The content of CTAB was reduced and the content of OP-10 was increased.The optimal composition of the flux was determined through optimizing the surfactant. The proportion of aipic acid and sebacid acid was 4:1, the proportion of stearic acid, PEG and rosin was 2:1:2. The addition of OP-10 and CTAB were 0.3% and 0.9%. The solder joints were more regular when using the optimal flux. The color of the flux did not change when it was used under 170℃for 30 minutes. The flux can meet with the needs of high-temperature soldering of electronic devices.