Microelectronic chips are typically flat bodies with oppositely facing, generally planar front and rear surfaces with edges extending between these surfaces. Chips generally have contacts, sometimes also referred to as pads or bond pads, on the front surface which are electrically connected to the circuits within the chip. Chips are typically packaged by enclosing them with a suitable material to form microelectronic packages having terminals that are electrically connected to the chip contacts. The package may then be connected to test equipment to determine whether the packaged device conforms to a desired performance standard. Once tested, the package may be connected to a larger circuit (e.g., a circuit in an electronic product such as a computer or a cell phone) by connecting the package terminals to matching lands on a printed circuit board (PCB) by a suitable connection method such as soldering.
Microelectronic packages may be fabricated at the wafer level; that is, the enclosure, terminations and other features that constitute the package, are fabricated while the chips, or die, are still in a wafer form. After the die have been formed, the wafer is subject to a number of additional process steps to form the package structure on the wafer, and the wafer is then diced to free the individually packaged die. Wafer level processing can be an efficient fabrication method because the footprint of each die package may be made identical, or nearly identical, to the size of the die itself, resulting in very efficient utilization of area on the printed circuit board to which the packaged die is attached.
A common technique for forming electrically conductive connections between a microelectronic chip and one or more other electronic components is through wirebonding. Conventionally, a wirebonding tool attaches the end of a wire to a pad on a microelectronic chip using thermal and/or ultrasonic energy and then loops the wire to a contact on the other electronic component and forms a second bond thereto using thermal and/or ultrasonic forces.