Electronics lead-free wave soldering

Lead-Free Solder Alloys. Because of the toxicity of lead and the concern that the lead in electronic products may end up in landfills, and ultimately in the water supply, the electronic industry is exploring alternative solder alloys that do not contain lead. These alternative solder alloys are typically composed of tin (Sn), with one, two, or three additives such as copper (Cu), silver (Ag), bismuth (Bi), antimony (Sb), zinc (Zn), or indium (In). Typical tin lead-free candidate solder alloys include Sn-Cu, Sn-Ag, Sn-Ag-Cu, Sn-Ag-Cu-Sb, Sn-In, and Sn-Cu-Bi-Sb. Some of these are more suitable for wave solder... 

In addition to wire harness connectors, printed circuit board-attached connectors, for automotive or electronic applications, also benefit from many of SPS s performance characteristics, including low viscosity, which helps to fill thin walls and heat resistance to maintain dimensional stability through lead-free reflow soldering operations (see Table 15.2). The trend toward miniaturization in automotive electronic control modules has increased the need for compact surface mount connector technology, as opposed to bulkier through-hole and wave-soldered alternatives. 

There has been a significant worldwide effort to identify suitable lead-free solder candidates to replace eutectic Sn Pb utilized for both the reflow and wave solder attachment of components to PWBs utilized in microelectronic assemblies. Because this effort has consumed much of the initial focus in the lead-free movement within the electronics industry, it is not surprising that the introduction of lead-free solders will represent the initial implementation step. It must be recognized, however, that electronic assemblies wiU, for the most part, be hybrids (i.e., while the solder is utilized for assembly, both reflow and wave solder operations will be lead-free). It is possible in some assemblies that nothing else will be lead-free, including the components and board finishes, as illustrated in Fig. 6. 

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