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SMT-Apr2017

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8 SMT Magazine • April 2017 by Stephen Las Marias I-CONNECT007 What a Tangled (Soldering) Web We Weave! Soldering remains one of the most criti- cal processes in the PCB assembly industry as it "makes or breaks" a finished product—figura- tively and literally (for one, cracked solder joints on a circuit board were said to be the main con- tributor to the fatal crash of Indonesia AirA- sia flight QZ8501 on December 28, 2014). The cost of failure is just too high. Therefore, it is of the utmost importance that the soldering quality should be perfect. But the thing is, soldering is just too complex a process, and further complicating the situation, the pro - cess, materials and technologies vary between our industry's market segments. There are just a lot of factors to consider before you put your boards into the reflow and let them run. Soldering for different end-markets or applications—military/ aerospace electronics, automotive electronics, medical electronics, or consumer electronics— have their own set of requirements. The military/ aerospace sector, for one, still uses leaded solder, while the rest have moved on to lead-free. According to our recent survey on soldering, there are myri - ad factors to con- sider based on the different end markets. There's the increased inspection when it comes to high-reliability applications; thermal considerations; solder paste, bar and flux considerations; coating selection; equipment; and the cleaning process, to name a few. And then there's the issue of solder paste se- lection or qualification. In our soldering survey, respondents highlighted challenges such as rhe- ology of the paste, consistency, type of solder to use, cleanliness—or ensuring their current cleaning processes can remove the fluxes, print- ability, and even the "irrational customer pref- erences." There's a paralysis of choice as there are too many choices and fine differences to ac- count for when selecting a solder paste. When it comes to their greatest challenges, respondents to the sur vey highlighted thermal issues, solder selection, reflow profiles, voiding, component size variations, rework, and inspec - tion, among others. Still, there seems to be a misconception when it comes to no-clean flux, as about 23% of the respondents in our survey believe that using no- clean flux will result in "bright and shiny solder E DITOR'S NOTE

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