There´s more to Pb-free production than just a Pb-free product

The electronics industry is facing a well known July 1 deadline in its efforts to meet the requirements of the restrictions of hazardous substances (RoHS). In response to health and environment concerns, the goal of RoHS is to restrict the use of six substances within electrical and electronic equipment. Although RoHS is an initiative of the European Union, it also applies to goods exported to Europe. Comparable legislation is pending in China and other nations are developing similar restrictions. Of the six elements and compounds included in the RoHS directive, lead has probably received the most attention within the electronics industry. With more than a third of its weight contributed by lead, eutectic solder has been a key ingredient in circuitry since the early days of electronics. Although some exemptions exist, PWBs and IC substrates will generally be required to meet the new Pb-free requirements. The use of Pb-free alloys creates different intermetallic compounds within the solder joint, which may directly impact reliability. In addition, however; the change in assembly subjects the PWB and package substrates to more severe processing conditions in comparison to eutectic assembly. These changes are far-reaching, affecting upstream PWB and package substrate fabrication steps. The change to Pb-free solder will result in more demanding requirements for processes such as inner layer bonding, through-hole metallization and copper plating. In particular, the demands of the final finish may be increased dramatically, depending on the assembly requirements. Awareness of the impact of Pb-free requirements must go beyond the product composition. This presentation attempts to summarize some of the major PWB and package substrate concerns associated with the transition to Pb-free electronics. Results of some recent investigations comparing the reliability of eutectic and Pb-free assemblies are presented