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To: long-gone who wrote (2522)	1/27/2000 12:07:00 PM
From: long-gone	Read Replies (1) \| Respond to of 8010

20k tons of solder a year - this may be LOW - outdated! VTE Aufbau- und Verbindungstechnik in der Elektronik Scientific-Technical Journal of the German Welding Society (DVS) Content No. 05/1999 dvs-verlag.de SCIENTIFIC TECHNICAL PAPERS Lead-free solders: and what now? B. Adolphi Leaded petrol is hardly ever used nowadays - and if it is, there will be heavy duties imposed on it. Now toxic lead is about to be removed from all soldering materials, too. The responsible institutions in Brussels are discus sing the second draft "Proposal for a Directive on Waste from Electrical and Electronic Equipment". If this directive were to be enforced, it would become illegal to manufacture solders with lead inside the European Union starting January 2004. The US-regulations concerning the substitution of lead exclude the electronics industry. The global electronics industry alone consumes ca 20,000 tons of lead every year for the manufacture of solders. It seems apparent that a similar amount of lead - leaded components of appliances at the end of their service lives - needs to be discharged, treated or recycled. Regulations, which aim at replacing the leaded components by non-toxic materials, therefore seem sensible and even necessary. Soldering has been using leaded alloys throughout the centuries: they are not expensive and technologically user friendly. The most frequently applied alloy is the eutectoid SnPb40, but alloys with a higher lead content are used in manufacturing areas where higher soldering temperatures are required. The fields of application include the entire electronics industry from telephones over computers to car electronics. The properties of these alloys are well known; we are familiar with their benefits but also their shortcomings when they are exposed to long-term thermal and thermo-mechanic stress. In full knowledge of these shortcomings, the search for viable alternatives to SnPb40 already began a long time before a ban on lead was first suggested. Tin will remain the basis for the solder. Any alternative materials should, as much as possible, have the same properties as the solder that stands to be replaced. This means that the following questions need to be answered: - What alloy materials could be considered if a certain melting point must be reached; how do they compare in terms of toxicity and cost? - Which wetting properties would the solders produced on the basis of these materials have? - What thermal, electric and - most of all - mechanic properties would the solder joints have? - How is their durability to be rated (phase growth, grain coarsening, creeping, fatigue)?