Solder ball with chemically and mechanically enhanced surface properties

A metal alloy solder ball comprising:

• a first metal and a second metal, the first metal having a sputtering yield greater than the second metal;
• a bulk portion having a bulk ratio of the first metal to the second metal;
• and
• a surface gradient between an outer surface of the solder ball and said bulk portion, the surface gradient having a depth and a gradient ratio of the first metal to the second metal that is less than the bulk ratio, the gradient ratio increasing gradually along with surface gradient depth from a minimum at the outer surface.

A metal alloy solder ball comprising:

• lead and tin, the lead having a sputtering yield greater than the tin;
• a bulk portion having a bulk ratio greater than or equal to about 90:10 lead:tin by weight;
• a rough outer surface as compared to an outer surface of an otherwise identical solder ball that has not undergone a roughening step;
• and
• a surface gradient between the outer surface of the solder ball and the bulk portion, the surface gradient having a depth and a gradient ratio of the lead to the tin that is less than the bulk ratio, the gradient ratio increasing gradually along with surface gradient depth from a minimum at the outer surface.