The influence of size and composition on the creep of SnAgCu solder joints

The paper presents creep data, that was gained on non eutectic SnAgCu-solder specimens with a variety of compositions. The non eutectic SnAgCu-Alloys were tested in different specimen sizes: bulk specimens, FBGA solder balls, flip chip solder joints. The results of the creep experiments show that both, solder alloy composition and solder joint size have a significant influence of the creep properties of the solder material. Bulk solder specimens have a rectangular cross section of 4mm X 3mm and contained the following alloys: Sn98Ag2, Sn97Ag3, Sn96Ag4, Sn97.5Ag2Cu0.5, Sn97.1Ag2Cu0.9, Sn98.8Ag2Cu1.2, Sn965Ag3Cu0.5, Sn96.1Ag3Cu0.9, Sn95.8Ag3Cu1.2, Sn96.9Ag3Au0.1. FBGA solder balls contained three non eutectic alloys with a content of 0,5% < Ag < 4% and 0,2% < Cu < 0,8%. Flip chip solder joints contained an eutectic Sn96.5Ag3.5 alloy and an non-eutectic SnAg alloy with Ag < 3%. Creep experiments have been carried out in a temperature range between T = 5 degrees C... 150 degrees C. The microstructures of the various solder specimens have been analysed to understand their differences in creep behavior.