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|Evaluation of the Performance of RoHS Compliant Thick Film Conductors with Various Lead Free Solder Alloys|
|Keywords: RoHS Compliant , Thick Film, Palladium Silver Conductors|
|With the implementation of the Restriction of Hazardous Substance (RoHS) Directive banning the use of Lead, Cadmium, Mercury and Hexavalent Chromium, hybrid microelectronic manufacturers are globally embracing the lead free movement. These manufacturers must not only understand the implications of their material choice but must be aware of the interaction between lead free solder alloys and their RoHS compliant thick film materials. It is commonly known that lead free solder alloys process at different reflow temperatures, but there are also other concerns. Lead free solders alloys generally require a different organic flux system to promote wetting and reflow. In general the appearance of lead free solders are quite different from traditional tin lead based solders. Many of these situations provide new challenges for the hybrid circuit manufacturer. There is little information available regarding the effects of the lead free solders on RoHS complaint thick film materials. This paper discusses the results of newly developed Pb and Cd free thick film conductor materials. A range of Palladium Silver thick film conductors has been developed and evaluated. Palladium to Silver ratios of 3:1, 4:1, 6:1, 8:1 and 30:1 were included in the investigation. These conductors were evaluated by comparing lead free solder alloys to traditional tin lead silver solder alloys. This study included evaluations based on solderability, leach resistance, and initial and long term adhesion studies. Results are published describing the difference in behavior between the different solder alloys in conjunction with the different Pd/Ag ratios. Key words: Thick film, Lead free solder, Tin Lead Silver solder, Palladium Silver Conductors|
|Samson Shahbazi, Sr. Research Scientist
Heraeus Materials Technology LLC
West Conshohocken, PA