Leach-resistant solder alloys for silver-based thick-film conductors
A tin-lead solder alloy containing copper and/or nickel and optionally silver, palladium, platinum and/or gold as its alloying constituents. The solder alloy consists essentially of, by weight, about 5% to about 70 % tin, up to about 4% silver palladium, platinum and/or gold, about 0.5 % to about 10...
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Zusammenfassung: | A tin-lead solder alloy containing copper and/or nickel and optionally silver, palladium, platinum and/or gold as its alloying constituents. The solder alloy consists essentially of, by weight, about 5% to about 70 % tin, up to about 4% silver palladium, platinum and/or gold, about 0.5 % to about 10% copper and/or nickel, the balance lead and incidental impurities. The presence of copper and/or nickel in the alloy has the beneficial effect of inhibiting the dissolution and leaching of silver from a silver-containing thick-film, such as a conductor (18) or solder pad (16), into the molten solder alloy during reflow. In addition, solder joints (22) formed of the solder alloy form a diffusion barrier layer (24,26) of intermetallic compounds that inhibit solid-state interdiffusion between silver from a silver-containing thick-film (16,18) and tin from the solder joint (22). |
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