冷速对无铅焊点力学行为的影响

哈尔滨工业大学工学硕士学位论文AbstractThe legislation to ban the use of Pb-based solders will become effective im-mediately,which provide a driving force for enterprises to accelerate Pb-freeprocess.It's found that reflow soldring plays an important role in Surface Mount-ing Technology ,moreover,cooling rate in reflow soldering profile is gettingmore and more attention after the use of high-melting-point solders.The melting point of Pb-free solders is 30C-40C higher than Sn-Pbeutectic solder.The increase of temperature in reflower becomes a challenge ofPrint Circuit Board (PCB)and components.As a result,the Time Above Liquid(TAL)of solder joints becomes longer,therefore,fast cooling in reflow solderingis used for controlling the PCBA temperature,improving the microstructure ofjoints and decreasing the thickness of intermetallic compound,consequently,high quality products can be obtained.How cooling rate affects the quality of soldering joints in lead-free processwas studied in this paper.The experiments were based on practical industrialproduction and it focused on the effect of cooling rate on microstructure andmechanical properties.When cooled at 4~6'C/S,the microstructure of joints were refined,the IMCof Ag3Sn and Cu6Sns phases disperse in eutectic network in joints which presentspherical particles.The fracture of these joints after tensile failure presentsdimple mode.Furthermore,the thickness of IMC was thin and it present gentleincline morphology.ItKeywords Rflow Soldring;Cooling Rate;Pulll;Push;