Leaching. Dissolution of a metal coating into liquid solder. Leaching applies to liquid solder and, at times, is applied inaccurately to metallurgical effects, like diffusion, that occur after the solder has solidified.
Please help us understand your situation better. * Base material of your end caps? * Solderability protection of the base material in the end caps? * Solder being used? * etc?
no S**t, I was going into SMTnet to post a question, on :
1) what is the actual "physics" behind "Leaching" defect? what is the accurate desciption to define this defect? how to eliminate the general causes to this defect? If encounter, what work process/how to get concession waiver to IPC-A-610C acceptance spec?
2) what is the actual "physics" behind "Metallization" defect? what is the accurate description to define this defect? how to elinimate the general causes to this defect? If encounter, what work process/how to get concession waiver to IPC-A-610C acceptance spec?
With a nickel barrier and 'tin' plating, reconsider your reflow recipe to reduce the leaching of the termination into the solder during reflow. Points are: * In designing a reflow temperature recipe, it is important that the temperature be raised at least 20*C above the melting or liquidus temperature to ensure complete solder melting, flux activation, joint formation and the avoidance of cold melts. * The total time the parts are held above the melting point must belong enough to alloy the alloy to wet, to become homogenous and to level, but not enough to cause leaching of solder, metallization or flux charring. Reflow guidelines are: ** 270�C / 70 seconds max ** 250�C / 78 seconds max ** 230�C / 92 seconds max
Think about this, try soldering to the end cap plating, rather than trying to get the plating to melt in the solder. You do not need to melt a pure tin coating to get a good joint as pure tin will wet quite well.
[We know, We know. We have been arguing for a long time that you need to think about the alloy formed between the solder and the end cap plating, but we're taking a different tact.]