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Reliability and production of solder joints with lead-free alloys

Select alloys for electronics production. Investigate
consistent production/rework/repair processes. Modelling
deformation/degradation behaviour of selected alloys.
reliability testing recommendations.Reliability estimations.

The EU Directive on Waste Electrical and Electronic Equipment will ban the use of lead in solder alloys used in electronic applications in 2004. This will lead to a significant change in production processes since substitute alloys have a higher liquidus temperature than eutectic tin lead solder alloys. The LEADFREE project aims to solve the most crucial problems in the fields of production and reliability in close collaboration with Industry. * A large variety of alloys are recommended currently as a replacement. Considerable confusion exists in Industry about which alloys are to be used in the future. This project will identify a small number of alloys with respect to reliability and optimal production parameters. * New solder profiles for reflow soldering as well as wave soldering have to be worked out. These important production process parameters will be evaluated in actual production plants. The participating industrial partners will gain hands-on experience in handling the new solder alloys. Their experience, together with the expertise of a solder producer, will provide important input for the recommendation of solder alloys. * Some of the production equipment may not be able to withstand the elevated temperatures necessary to process lead-free solder alloys. In collaboration with equipment producers problems will be identified where they occur and solutions will be proposed. * Currently used PCB materials can probably not be processed with the temperatures needed for lead-free solder alloys. Their limits and possible replacements have to be worked out. This will be done by a PCB manufacturer together with raw material suppliers. * Several electronic components will definitely not be able to tolerate the elevated temperatures. However, possible defects in components rated for elevated process temperatures must be investigated. * Currently used flux systems polymerize when they are subject to elevated temperatures. Thus the efficiency of currently used cleaning processes will be evaluated. * Process parameters for repair/rework including repair on/with PCBs/components plated with tin-lead alloys must be worked out. * Visual inspection criteria must be established. * Selective soldering strategies (Repair, Retouching, Production) must be established. * The metallurgy of lead-free solder alloys with various pad surfaces and connector coatings is not yet well enough known for reliability estimations. It is one of the project's goals to clarify relevant parameters. * The deformation and degradation behaviour of selected alloys has to be modelled in order to perform accelerated reliability tests on solder joints and make reliability estimations. The implementation of these models in FEM (Finite Element Method) modelling will help to achieve a deeper understanding of the failure mechanisms in lead-free solder joints. * The deformation model will make it possible to work out guidelines for the design of accelerated reliability tests for electronic equipment soldered with lead-free solder. * The know-know resulting from this project will be distributed by workshops held whenever a milestone is reached. When desired by the members in the team, it is planned to implement the now-how in the companies cooperating in the project through professional training of staff. Swiss contribution to the project: * Suitability of lead-free alloys for simultaneous solder processes for mass production. * Evaluation of process parameters for simultaneous solder processes for mass production (Convection, Vapour Phase, Wave). * Evaluation of efficiency of cleaning processes. * Measurement and modelling of materials behaviour (Deformation/degradation) * Metallurgy. * FE Simulation of strain/fatigue on solder joints. * Reliability estimations on solder joints with accelerated tests. German contribution to the project: * Suitability of lead-free alloys for manual and selective solder processes for repair/retouching as well as production purposes. * Evaluation of process parameters for manual and selective solder processes for repair/retouching as well as production purposes. * Evaluation of visual. * Measurement of wetting behaviour of lead-free alloys on various surface finishes. * Metallurgy. * SIR testing. * Reliability estimations on solder joints with accelerated tests. Keywords: lead-free solder, production, reliability.
Acronym: 
LEADFREE
Project ID: 
2 368
Start date: 
01-03-2001
Project Duration: 
60months
Project costs: 
5 400 000.00€
Technological Area: 
Metals and Alloys
Market Area: 

Raising the productivity and competitiveness of European businesses through technology. Boosting national economies on the international market, and strengthening the basis for sustainable prosperity and employment.