Reliability Aspects of Lead-Free Soldering in Industrial Applications

The forthcoming European legislation restriction of hazardous substances (RoHS), in effect at July 1st 2006, has prohibited the use of certain substances for electronic and or electrical equipment. One of these prohibited materials is lead, which has been used for the past decades in the solder used to connect the components to the printed circuit boards (PCBs). Therefore, lead-free solders have been developed to replace the SnPb solders. The military, medical and aerospace industries work exclusively with proven technologies and are consequently exempted from these directives. Consumer electronics already has experience with lead-free technology, although the products have a shorter lifespan, whereby the maintaining of the product is of lower importance. Industrial electronics has almost no experience with lead-free technology yet remains confronted with longevity problems. The main alternatives solder alloys are Sn, Ag and Cu (SAC) near eutectic composition. As these alloys have higher melting points and different physical characteristics in comparison to SnPb, research is needed to discover the eventual problems with the replacement of SnPb. In this work PCBs with Ni/Au finish have been soldered with SAC and SnPb alloys. Reflow and wave soldering have been performed on three type of industrial. The components soldered to the board were: ceramic resistor, ceramic capacitor, coil, diode, jumper, plastic spacer, hybride module, flexible PCB, QFP, LED, electrolytic capacitor, capacitor, oscillator, cable or connector. The component finishes encountered were: pure Sn, SnPb, SnPb40 and AgPd. Environmental and bump tests have been conducted and analyzed by means of metallurgical research. Visual and light microscopy as well as in-circuit tests have been preformed