Creep of thermally aged SnAgCu-solder joints
ABSTRACT The creep behaviour of Sn96.5Ag3.5- and Sn95.5Ag3.8Cu0.7-solder was studied specifically for its dependence on technological and environmental factors. The technological factors considered were typical cooling rates and pad metallizations for solder joints in electronic packaging. The environmental factors included microstructural changes as a result of thermal aging of solder joints. Creep experiments were conducted on three types of specimens—flip–chip joints, PCB solder joints and bulk specimens. flip–chip specimens were altered through the selection of various under bump metallizations (Cu vs. NiAu), cooling rates (40 K/min vs. 120 K/min), and thermal storage (24 h, 168 h, and 1176 h at 125 °C). PCB solder joints were studied by using a copper pin soldered into a thru-hole connection on a printed circuit board having a NiAu metallization. Bulk specimens contained the pure alloys. The creep behaviour of the SnAg and SnAgCu solders varied in dependence of specimen type, pad metallization and aging condition. Constitutive models for SnAg and SnAgCu solders as they depend on the reviewed factors are provided.
- SourceAvailable from: Oliver Krammer
Soldering and Surface Mount Technology 08/2014; 26(4-4):214-222. DOI:10.1108/SSMT-09-2013-0023 · 0.69 Impact Factor
- "For example the effect of pad geometry on tombstone effect [Huang, 2005], influences of the moisture absorption on PBGA package's warpage during reflow process [Chien, 2003], [Lee, 1998] and the creep behaviour of joints soldered with Vapour Phase reflow were studied [Wiese, 2007]. Besides, the effect of SnAgCu alloy composition on tombstoning during VP soldering was investigated by Huang et al. [Huang, 2005]. "
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ABSTRACT: This study points out the influence of cooling rate and solders composition on the microstructure of bulk SnAgCu. Therefore the alloys SnAg3.8Cu0.7, SnAg3.0Cu0.5 and SnAg3.5Cu0.4 were solidified with different cooling rates from 0.35 K/min to 37.4 K/min. During these experiments the temperature of the solder was measured. Changes in microstructure were investigated after thermal storage at 125degC, for 0.05 h, 0.5 h, 5 h, 50 h and 500 h. In an additional experiment a temperature gradient was generated inside different solder samples during solidification. The cross sections of these bulk samples indicate influence and dependence on phase growth, caused by this directed solidification. The chosen alloys, SnAg3.0Cu0.5, SnAg3.0Cu1.5 and SnAg3.0Cu0.5Au0.14 show effects on microstructure, caused by impurities like Au and Cu, which can solute from the PCB metallization during reflow. Another experiment shows the potential and the advantages of a new developed method for temperature measurements during the reflow process
Conference Paper: Effect of Chemistry on Viscoelastic Properties of Moulding Compounds[Show abstract] [Hide abstract]
ABSTRACT: The present state-of-the-art in simulation of stresses in electronic packages is to model the moudling compound as a viscoelastic material. That means that stresses during packaging and subsequent thermomechanical loading are allowed to relax partially. Such an approach was seen to improve thermomechanical predictions considerably compared to the previously used temperature dependent elastic models. Therefore viscoelastic simulations are now becoming the standard for the modelling of packaging stresses and viscoelastic characterization of new moulding compound materials is now routinely being performed by most of the companies involved with packaging of electronic components. A problem is, however, that the viscoelastic data of moulding compounds turns out to be quite sensitive to variations in the compound chemistry and that this chemistry may vary slightly from batch to batch. Since these variations do not have a large effect on the room temperature properties (like the modulus) they often remain undetected by the standard quality tests. In order to anticipate to these problems it is desirable to develop a fundamental understanding of what parameters influence the viscoelastic properties of thermosets. A quantitative model, such as will be presented in this paper, has the additional advantage that it can be used for the selection of moulding compounds with optimized viscoelastic properties.Thermal, Mechanical and Multiphysics Simulation and Experiments in Micro-Electronics and Micro-Systems, 2006. EuroSime 2006. 7th International Conference on; 05/2006