Au bump is provided on an Al pad of a semiconductor chip. Substrate pads are arranged at predetermined pitches on a circuit board. In each substrate pad, the length (L) of a first side parallel to the array direction is shorter than the length (M) of a second side which is orthogonal to the first side....http://www.google.de/patents/US5889326?utm_source=gb-gplus-sharePatent US5889326 - Structure for bonding semiconductor device to substrate
