In this situation, BGA solder joints are melted first and covered on solder paste whose alloy isn't melted, leading to massive collapse and oxidation of lead solder balls. As a result, soldering defects tend to be caused in this transient process.įor example, when lead-free SAC solder paste is used to solder lead BGA (ball grid array) solder joints, forward compatibility will take place, which derives from the fact that component distributors' lead-free schedule is later than that of PCB manufacturers'. That's because different apartments in electronics manufacturing industries fail to keep synchronization on lead-free schedule and technology preparation. A transient process must be available with lead and lead-free elements coexisting. Total transition can never be achieved just by one step from complete SnPb soldering system to totally lead-free soldering system. As a result, all the soldering tools manufactured by industrial manufacturers, soldering equipment and supporting materials used for soldering have to be designed and selected based on heat resistance of 260☌. Peak temperature in lead-free reflow soldering can be as high as 250☌, so the lowest heat resistance of MVCs has to be set to be at least 260☌. Lead and lead-free components differ from each other in terms of their capability to withstand reflow soldering.īecause the peak temperature in lead reflow soldering won't exceed 230☌, heat resistance of MVCs should be set to be at 240☌, including all the soldering tools manufactured by industrial manufacturers, soldering equipment and supporting materials used for soldering all of which are designed and selected based on heat resistance of 240☌. MVCs refer to the most vulnerable components (MVCs) during reflow soldering such as liquid dielectric aluminum electrolytic capacitors, connectors, DIP switches, LEDs, transformers, PCB (Printed Circuit Board) substrate material etc.
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