Microstructural evolution due to aging of solder alloys determines their long-term reliability as electrical, mechanical and thermal interconnects in electronics packages. The ability to accurately determine the reliability of existing electronic components as well as to predict the performance of proposed designs depends upon the development of reliable material models. A kinetic Monte Carlo simulation was used to simulate microstructural evolution in solder-class materials. The grain growth model simulated many of the microstructural features observed experimentally in 63Sn-37Pb, a popular near-eutectic solder alloy. The model was validated by comparing simulation results to new experimental data on coarsening of Sn-Pb solder. The computational and experimental grain growth exponent for two-phase solder was found to be much lower than that for normal, single phase grain growth. The grain size distributions of solders obtained from simulations were narrower than that of normal grain growth. It was found that the phase composition of solder is important in determining grain growth behavior.

Over the past two years extensive experimentation has been carded out to determine the nature of bulk damage in KDP. Automated damage testing with small beams has made it possible to rapidly investigate damage statistics and its connection to growth parameter Variation. Over this time we have built up an encyclopedia of many damage curves but only relatively few samples have been tested with large beams. The scarcity of data makes it difficult to estimate how future crystals will perform on the NIF, and the campaign nature of large beam testing is not suitable for efficient testing of many samples with rapid turn-around, it is therefore desirable to have analytical tools in place that could make reliable predictions of large-beam performance based on small-beam damage probability measurements. To that end, we discuss the application of exponential and power law damage evolution within the framework of Poisson statistics in this memo. We describe the results of fitting these models to various damage probability curves on KDP including the heavily investigated KDP214 samples. We find that both models are capable of fitting the damage probability S-curves quite well but there are multiple parameter sets for each model that produce comparable {chi}{sup 2} …

Automated damage testing of KDP using LLNL's Zeus automated damage test system has allowed the statistics of KDP bulk damage to be investigated. Samples are now characterized by the cumulative damage probability curve, or S-curve, that is generated from hundreds of individual test sites per sample. A HeNe laser/PMT scatter diagnostic is used to determine the onset of damage at each test site. The nature of KDP bulk damage is such that each scatter signal may possess many different indicators of a damage event. Because of this, the determination of the initial onset for each scatter trace is not a straightforward affair and has required considerable manual analysis. The amount of testing required by crystal development for the National Ignition Facility (NIF) has made it impractical to continue analysis by hand. Because of this, we have developed and implemented algorithms for analyzing the scatter traces by computer. We discuss the signal cleaning algorithms and damage determination criteria that have lead to the successful implementation of a LabView based analysis code. For the typical R/1 damage data set, the program can find the correct damage onset in more than 80% of the cases, with the remaining 20% being left to operator …

Laser induced material modifications in the bulk and on the surface of KDP (KH{sub 2}PO{sub 4}) and DKDP (70-80% deuterated KDP) are studied using fluorescence imaging and spectroscopy. Photoluminescence is observed at damaged regions following above threshold exposure with an emission peak centered at 550-nm. In addition, surfaces exposed to >100 high power, 355-nm laser pulses reveal a reduced surface finishing quality as evidenced by an associated emission under UV photoexcitation. The emission spectra from the laser-induced damage sites and the laser degraded surfaces are similar suggesting the generation of similar defect species.