Basic Requirements for Lead-free Electronic Solder in Electronic Assembly (Part I)
Release time:
2022-09-20
【Summary Description】 The basic processes of lead-free soldering assembly include: a. lead-free PCB manufacturing process; B. 96.5Sn/3.5Ag and 95.5Sn/4.0Ag/0.5Cu eutectic and approximate eutectic alloy systems applied in solder paste; C. 99.3Sn/0.7Cu eutectic alloy system for wave soldering applications; D. 99.3Sn/0.7Cu alloy system for manual soldering. Although these are all feasible processes, there are still several major problems in the specific implementation, such as the raw material cost of electronic solder is still higher than that of standard Sn/Pb process, the restriction on wettability is increased, the inert air state (sufficient nitrogen is required) is required in wave soldering process, and the thermal requirements for various components are increased due to the possibility of raising the reflow temperature to the limit temperature range (between 235 ℃ and 245 ℃). As far as lead-free alternatives to electronic solders are concerned, there is no generally accepted set of specifications. After many discussions with many professionals in this field, we have come to the following technical and application requirements: Many assembly manufacturers require that the price of lead-free alloys cannot be higher than 63Sn/37Pb, but unfortunately all existing lead-free alternatives cost at least 35% more than 63Sn/37Pb. In the choice of lead-free solder and solder wire, the cost of metal is one of the most important factors, and in the production of solder paste, because the technical cost of the overall manufacturing cost is relatively high, so the price of metal is not so sensitive.
The basic processes of lead-free soldering assembly include: a. lead-free PCB manufacturing process; B. 96.5Sn/3.5Ag and 95.5Sn/4.0Ag/0.5Cu eutectic and approximate eutectic alloy systems applied in solder paste; C. 99.3Sn/0.7Cu eutectic alloy system for wave soldering applications; D. 99.3Sn/0.7Cu alloy system for manual soldering.
Although these are all feasible processes, there are still several major problems in the specific implementation, such as the raw material cost of electronic solder is still higher than that of standard Sn/Pb process, the restriction on wettability is increased, the inert air state (sufficient nitrogen is required) is required in wave soldering process, and the thermal requirements for various components are increased due to the possibility of raising the reflow temperature to the limit temperature range (between 235 ℃ and 245 ℃).
As far as lead-free alternatives to electronic solders are concerned, there is no generally accepted set of specifications. After many discussions with many professionals in this field, we have come to the following technical and application requirements:
Many assembly manufacturers require that the price of lead-free alloys cannot be higher than 63Sn/37Pb, but unfortunately all existing lead-free alternatives cost at least 35% more than 63Sn/37Pb. In the choice of lead-free solder and solder wire, the cost of metal is one of the most important factors, and in the production of solder paste, because the technical cost of the overall manufacturing cost is relatively high, so the price of metal is not so sensitive.
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