{'fraction_non_alphanumeric': 0.012542759407069556, 'fraction_numerical': 0.010262257696693273, 'mean_word_length': 5.408759124087592, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Effect of reflow conditions on the intermetallic layer in solder joints

The Cu6Sn5 intermetallic formed between Pb-free Sn-based solders and Cu substrates plays a critical role in the reliability of solder joints. Cu6Sn5 can adopt at least two different crystal structures over the temperature range to which electronics circuitry is exposed during assembly and service. Under equilibrium conditions the change from a hexagonal to monoclinic structure occurs on cooling solder joints below 186°C. However, cooling rates associated with common commercial soldering processes are typically faster than the rate that would permit complete transformation. In this paper the authors report a study on the effect of reflow cooling conditions on Cu6Sn5 crystal structure. The findings have important implications for the manufacture of solder joints and their in-service performance.