At the contractor level, once a product is required to be soldered with lead-free solders all the processes must be assessed to ensure the same quality a customer has been accustomed to with a 63/37 process is achieved. The reflow, wave soldering and hand assembly processes must all be optimized carefully to ensure good joint formation as per the appropriate class of electronics with new solder alloys and often new fluxes.
The selection of soldering materials and fluxes are key to providing high-quality solder joints with lead-free solders that tend to wet slower than leaded solders, but also the process equipment must be lead-free process compatible. Components must be lead-free and able to meet the thermal requirements of the process, MSL (moisture sensitivity limits) also must be observed. Board finish must be lead-free and the PCB must be able to sustain higher process temperature cycles with no physical damage and good solderability to enable subsequent soldering at the wave or hand assembly.
This paper is a summary of the experience at a medium-sized assembler in achieving the customer-driven mandate to go lead-free and the maintenance of production yields and quality using both tin-silver-copper and tin-copper in the assembly of high end printer boards. More than 120,000 builds were achieved with a 99.6 percent first pass yield for the overall soldering process.
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Founded in 1899, Kester is a world-renowned supplier of solder and related materials and services to the electronics assembly, micro-component, and industrial soldering markets. Kester is known for high quality, advanced technology and superior technical support. With headquarters in Itasca, IL, Kester has additional manufacturing facilities in the United States, Mexico, Canada, Singapore, Germany, Japan, Brazil, Taiwan, Malaysia and China. Its worldwide manufacturing and technical capabilities provide the support required to serve major electronics manufacturing services providers and OEMs.