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|Evaluation of Thick Film Conductive Pastes by using Lead Free Solder Alloys|
|Keywords: thickfilm, leadfree, solder|
|After the introduction of the RoHS guideline to 1 July 2006 the use of lead free solder alloys in many new electronic products is growing. SnAg, SnCu(Ni) and SnAgCu - alloys are particularly attractive due to its characteristics, the melting point and the availability of the materials. Also in the industries, which are not subjected to this regulation, the pressure to use these solder alloys is increasing, by which conversion of the component manufacturers to lead free solders. Already today many BGA and CSP containing lead, are only available in smaller quantities and/or at a higher price. This is on the one hand justified in the small market share (, S.16) of the thick film technique . On the other hand the basic element of the glass phase is in established thick-film pastes lead boron silica glass, whereby these pastes do not correspond to the RoHS guideline. The introduction on the market of RoHS conformal thick-film pastes took place only in recent past. In this work first results are presented with the employment of lead free solder alloys on different thick-film conductive pastes. Conventional thick film pastes on silver and silver platinum basis as well as newer, RoHS conformal conductive pastes on Al2O3-substrates were examined. The higher melting points of these solders require a higher soldering temperature, which affect strengthened the diffusion of the silver and palladium particles of the conductive pastes. In the focus of the investigations the processing parameters and the effect on the formation of the intermetallic phases were studied. In addition the temperature-dependent changes were analyzed at 150°C high temperature storage, similarly to the JEDEC JESD22-A103C, by means of shear test as well as cross section.|
|Lars Rebenklau, Dr.-Ing.
Technische Universität Dresden
Dresden, Saxony D-01069,