Characterisation of silver particles used for the Low Temperature Joining Technology

The Low Temperature Joining Technology (LTJT) is an important alternative to lead containing solders. Therefore the basic material, silver powders have been investigated. The particle morphology, the amount and composition of their organic coating and chemical impurities have been analysed. Scanning Electron Microscopy (SEM) has been used to determine the morphology of the silver particles. Differential Scanning Calorimetry (DSC) in combination with Thermogravimetry (TG) and Mass Spectroscopy (MS) reveals the occurrence of exothermic or endothermic reactions as well as information concerning mass loss and formed molecules. To determine the components of the organic coating Time of Flight - Secondary Ion Mass Spectroscopy (ToF-SIMS) has been applied. Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) has been utilised to analyse chemical impurities. To remain a linkage between the characterised silver particles and the quality of a manufactured sintered joint, a shear test has been executed. One of the investigated powders reaches an averaged shear force of approximately 230 N. The mixture of small flake shaped and more spherical particles generates good adhesive strength.