Rolling ball connector

This invention generally relates to electrical connectors for semiconductor components. More particularly, it relates to a connector between an integrated circuit chip and a substrate. Even more particularly, it relates to a connector that provides a high degree of relief from thermal stress to provide a very reliable joint between an integrated circuit chip or package and a thermal expansion mismatched substrate. An integrated circuit assembly has pads of a chip electrically connected to pads of a substrate with rolling metal balls. A pliable material bonds the balls in movable contact with pads of the chip and substrate. Because the balls are relatively free to move, thermal expansion differences that would ordinarily cause enormous stresses in the attached joints of the prior art, simply cause rolling of the balls of the present invention, avoiding thermal stress altogether. Reliability of the connections is substantially improved as compared with C4 solder bumps, and chips can be safely directly mounted to such substrates as PC boards, despite substantial thermal mismatch.