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|The Effect of Solder Selection on High Platinum Palladium Silver Thick Film Conductors|
|Keywords: RoHS Compliant, Thick Film Conductors, Platinum Palladium Silver|
|With the implementation of the Restriction of Hazardous Substance ( RoHS) Directive banning the use of Lead, Cadmium, Mercury and Hexavalent Chrom ium, , 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 altered reflow profiles, but there are other concerns. Lead free solder alloys generally require a modified organic flux system to promote wetting and reflow. The appearance of lead free solder fillets can be dissimilar from traditional tin lead based solders. These situations provide additional challenges for the hybrid circuit manufacturer. There is limited information available regarding the effects of the lead free solders on RoHS compliant thick film materials. During the development of thick film material, in conjunction with Pb free solders, a previously unseen adhesion failure mechanism was identified. This failure occurred primarily in high Pd containing conductors. This paper investigates, in more detail, this unfamiliar adhesion failure mechanism and the results obtained from a customized family of Pb/Cd free thick film conductors. A range of high percentage Palladium Silver and Platinum Palladium Silver thick film conductors were developed and evaluated. These conductors were assessed by comparing lead free solder alloys to traditional tin lead silver solder alloys. Solderability, leach resistance, initial and long term adhesion studies and SEM photos will be presented. Results are available describing the diversity in behavior between the solder alloys in conjunction with the varied Pt/Pd/Ag and Pd/Ag ratios. Key words: Thick film, Lead free solder, Tin Lead Silver solder, Platinum Palladium Silver Conductors|
|Samson Shahbazi, Sr. Research Scientist
Heraeus Incorporated - Thick Film Division
West Conshohocken, PA