Electronics electronic assembly, lead-free materials

THE DEADLINE FOR LEAD-FREE ELECTRONIC ASSEMBLY IS LESS THAN 12 MONTHS AWAY. TIME IS RUNNING OUT TO GET "PRODUCTION-WISE." THIS ARTICLE REVIEWS UNDERSTANDINGS OF SCREEN PRINTING USING LEAD-FREE MATERIALS, AND DISCUSSES THE FINAL PIECES OF THE PUZZLE. 

In order to turn the entire electronics industry around from its more than 40 years of lead-tin solder assembly practices, a close working relationship is required with the supply chain, i.e., the vendors that provide materials, parts, and assembly services. The industry must come to some consensus concerning lead-free materials, particularly solders and component lead finishes. Vendors cannot be expected to provide multiple versions of individual part numbers. In addition, consensus will allow price reductions that result from economies of scale. As always, companies that desire products from vendors that lie outside the de facto standards (i.e., the industry consensus) must be prepared to bear the burden of additional costs, sourcing issues, and, in some cases, long lead times. 

Electronics Assembly and the Impact of Lead-Free Materials... 

Environmental legislation such as the European Union s Restriction of Hazardous Substances (RoHS) directive has a profound impact on all levels of the electronics supply chain, including these components. RoHS restricts the use of lead, which is an element in the solder used for component assembly onto printed circuits. The impact on the base materials and components is primarily the result of higher assembly temperatures that are associated with lead-free assembly. Table 7.1 summarizes the key issues for base material components. RoHS issues will be discussed further in Chap. 10. 

Science (NCMS) estimated that replacing Pb in electronic assemblies will result in a material cost of US 140-900 million dollars in the United States alone, with supply chain costs likely to run in the tens of billions of dollars [66]. Cost issues are related to materials (solders, components, boards, protective atmospheres during processing, additional energy consumption due to the higher process temperatures required for most lead-free solders, and operational costs). 

The manufacturing processes for soldering electronic assemblies were developed over decades as electronics technology advanced. The substitution of lead-free solders for the standard tin-lead alloys has a considerable deleterious effect on manufacturing methods, the entire supply chain of materials and parts, and the environment. The main contributing factor is the higher temperature required to melt and use the lead-free solder alloys. Development and performance testing of... 

Many North American companies are concerned that lead-free components and assemblies will not meet the reliability or functionality requirements necessary for high-end equipment supplied to banks, air traffic control systems, web-based businesses, and other mission-critical applications. Accordingly, manufacturers of aerospace and military electronics have no plans to introduce lead-free solders. There are too many reliability concerns to utilize lead-free solder materials in high-reliability equipment related to the mechanical characteristics of the materials themselves and the effects of high temperatures to process them. The effect of new and modified intermetallic compound phases within solder joints and at the interfaces is yet an additional concern, and there are many more. 

---