3 is substantially 30 of a thickness of the conductive base strip 1 when the grooves 3 are pressed on only one of the widthwise surfaces of the conductive base strip 1 the depth of each groove 3 is 20 to 30 the thickness of the conductive base strip 1 and a sum of a maximum depth of the grooves 3 pressed on an upper widthwise surface and a maximum depth of the grooves 3 pressed on a lower widthwise surface is no more than 50 the thickness of the conductive base strip 1 when the grooves 3 are pressed on both the upper and lower widthwise surfaces of the conductive base strip 1 a solder layer 2 made of tin copper alloy and having a thickness of 10 um is plated or heat coated on the conductive base strip 1 pressed with the grooves 3 to form a photovoltaic interconnect wire for each of the grooves 3 on the conductive base strip 1 a size of the groove 3 decreases gradually from the opening to the bottom of the groove 3 and a plane tangent to a point at a bottom surface of the groove has an inclination angle of 20 9 degrees to 45 degrees with respect to the widthwise surface of the conductive base strip 1 when 60 pieces of 156 156 polycrystalline silicon wafer are used to form a group.