Size effect, Miniaturization of SnInAg Solder Interconnects

For the development of novel further miniaturized microelectronic devices with applications below 150C (consumer electronics, telecommunication, commercial aviation, computers) the usually proposed replacement of Pb-Sn by Sn-Ag or Sn-Ag-Cu eutectics as solder materials would be disadvantageous due to the solvus temperature increase of about 40C. The project aims to investigate the applicability of Sn-Ag-In for the miniturization of solder joints avoiding this disadvantage. The methods proposed combine an enhancement of the insight of the underlying processes with testing of thermomechanical stability in practice oriented conditions. Especially the formation and development of metastable and stable intermetallic compounds at boundaries to Cu, Au, Ni., Pd should be investigated and thermal and elastic data should be determined. Miniturization reduces all geometrical dimensions of the solder joint. The reduction of the solder gap due to miniaturization decreases the volume ratio of ductile solder region and brittle intermetallic compound zone at the interface and thus changes the mechanical strength of the solder interconnect. The reduction of the typical diameter of the solder area down into the micrometer range will very likely be the cause for an enhanced crack probability as a mechanical size effect. In this project innovative measuring methods are introduced for sample geometries as present in technical applications. They will be used for the assessment of the reliability of miniturized solder interconnects at realistic mechanical and thermal loading.

For the development of novel further miniaturized microelectronic devices with applications below 150C (consumer electronics, telecommunication, commercial aviation, computers) the usually proposed replacement of Pb-Sn by Sn-Ag or Sn-Ag-Cu eutectics as solder materials would be disadvantageous due to the solvus temperature increase of about 40C. The project aims to investigate the applicability of Sn-Ag-In for the miniturization of solder joints avoiding this disadvantage. The methods proposed combine an enhancement of the insight of the underlying processes with testing of thermomechanical stability in practice oriented conditions. Especially the formation and development of metastable and stable intermetallic compounds at boundaries to Cu, Au, Ni., Pd should be investigated and thermal and elastic data should be determined. Miniturization reduces all geometrical dimensions of the solder joint. The reduction of the solder gap due to miniaturization decreases the volume ratio of ductile solder region and brittle intermetallic compound zone at the interface and thus changes the mechanical strength of the solder interconnect. The reduction of the typical diameter of the solder area down into the micrometer range will very likely be the cause for an enhanced crack probability as a mechanical size effect. In this project innovative measuring methods are introduced for sample geometries as present in technical applications. They will be used for the assessment of the reliability of miniturized solder interconnects at realistic mechanical and thermal loading.