Glass Passivated Research Of The Chip

High-voltage high-power bridge rectifiers are widely used in various kinds ofmeasurement instruments, home appliances, communication devices and equipments.This thesis conducts research and optimization of the design and process of the rectifierbridge’s chip manufacturing to improve its yield and reliability, after which the chipyield is improved from90%to over99%. The yield of bridge rectifiers after packing thechip could reach over99.2%. They not only pass all the normal reliability tests, theirdefect rate after storage in normal temperature for one month also decreases from500ppm to34ppm.Bridge rectifier chip is made via mesa technology and protected by fused glass. Interms of structure design, it mainly increases the thickness of four sides throughincreasing the thickness of glass to improve chip’s strength against mechanical stress. Atthe same time, the laser sawing of chip is introduced and the productivity is improvedby times.This thesis makes a theoretical analysis and summary on the conditions of siliconsurface, and conducts experiment and optimization on that basis, and concludes theadvantage and best process conditions in processing the silicon surface with phosphoricacid. Through the classification and analysis of impurity and its cleaning method, thethesis sums up three-step cleaning method through continuous optimization experiment.The method is simple and easy for operation and good at repetition.This thesis starts from the analysis of the composition of glass and conductscomparative experiments on the deposition methods of glass and confirms the bestprocess and method of electrophoresis glass deposition. Experimental research isconducted on temperature, time and protection gas for glass forming in view of itscharacteristics and concludes the best forming condition of glass.Though the analysis and summary of various failure modes and mechanism, thethesis confirms the defect reason of chip and proposes the optimization solution. The first is to improve the structure, as mentioned above. The second is to, in view of theprocess, keep650℃for2hours before the forming of glass, and flow in oxygen withminor hydrogen element. This not only improves the characteristics of glass but alsoforms an oxide film between silicon and glass, which improves the protection of chipjunction from having only glass protection structure to having both silicon oxide andglass for dual protection, and thus substantially improves the protection effect ofjunction.The equipment, tooling and materials used in this experiment are all cheap andavailable in the domestic market. In addition, the process is easy and practicable in massproduction, and also able to ensure the improvement of productivity.