a coil encircling the ferrite core of a magnetic head attached to a slider used in a hard disk drive is formed using two mating chips . a first chip having layered wires and bonding bumps is inserted in the winding window between the ferrite core and the body of the slider . a second chip having layered wires , bonding bumps and a groove straddling the ferrite core is disposed outside the winding window and mates with the first chip . bonding bumps , comprising low - melting solder , are heat bonded to form a continuous coil .