Now the majority of industrial welding use lead-free solder paste, solder paste must first be able to truly meet the requirements of environmental protection, not because of the removal of lead and add new toxic or harmful substances inside; to ensure the reliability of lead-free welding and after welding, many problems and to take into account customers bear the cost. To ensure the welding effect of lead-free solder paste need what conditions? Below declare lead-free solder paste, want to assure the condition that solder effect:
1, lead-free solder paste solder has a good wettability; general reflow solder stays in the above liquidus time is 30~90 seconds, wave soldering welding pin and circuit board base plate and liquid tin peak contact time is 4 seconds, after using lead-free solder paste, to ensure that in the above the time range of solder can exhibit good wetting properties, in order to ensure the effect of welding quality.
2, to low melting point lead-free solder paste, as close as possible to the 63/37 tin lead alloy eutectic temperature of 183 DEG C, if the new product eutectic temperature higher than 183 DEG C only a few degrees should not be a big problem; there are also low eutectic lead-free solder temperature in the development of the past, should try to melt the temperature interval of lead-free solder down, namely to reduce the temperature interval between the solidus and liquidus temperature and solidus liquidus temperature for a minimum of 1500C, depending on the specific application and soldering tin (with 265 DEG C; tin wire: 375 DEG C; SMT solder paste: 250 DEG C usually require the reflow temperature should be lower than 225~230 DEG C).
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