Ultrasonic flipchip, a cost effective alternative in mass production

Citation

(2003), "Ultrasonic flipchip, a cost effective alternative in mass production", Microelectronics International, Vol. 20 No. 3. https://doi.org/10.1108/mi.2003.21820cad.004

Ultrasonic flipchip, a cost effective alternative in mass production

Ultrasonic flipchip, a cost effective alternative in mass production

Keywords: Ultrasonic, Flipchip

The latest model ultrasonic flipchip bonder FJ 510 by Hesse and Knipps Semiconductor Equipment, Germany enables new possibilities for size and weight reduction in micro electronic assembly (Plate 2).

The most obvious advantage of flipchip technology is that with this mounting technology a chip scale of one is achieved. The space requirement on the substrate of the circuit is exactly the chip size. This is of great importance for any electronic applications in which high functionality has to be available in a small space. The shorter connections between chip and substrate lead to lower connection resistance. Equally important for the high frequency industry, the connections have nearly no inductivity, and thus eliminate the need for trimming circuits.

Plate 2 The ultrasonic flipchip bonder FJ 510

This leads to additional savings in space requirement and cost. ultrasonic flip chip technology has outstanding advantages, not only in the micro electronic and high frequency industry, but also in power electronics.

Compared to solder and epoxy flipchip methods, ultrasonic flipchip can achieve smaller gaps and higher connection strength between the bonded components. The thermal resistance of the chip to the environment is reduced significantly, allowing a higher current density. An additional advantage is the possibility to process materials unsuitable for solder flipchip methods.

The Hesse and Knipps ultrasonic flipchip bonder basically consists of a wafer handling system, a four axis bond head and the substrate handling system. Wafers of 4, 6 or 8in. diameter can be processed. The chip is removed from the wafer by ejecting the die from the "blue tape" with a special eject head. The die collet is mounted on a flip arm capable of rotating the die to 180°. The substrate handling consists of automatic product feeding to the preheat station and bond station, temperature control and automatic unloading of bonded substrates. The user interface is a menu type interface very similar to an MS-Windows based environment.

In the ultrasonic flipchip process dies are placed and bonded to the substrate pads by applying force and ultrasonic power. The pads on the die have to be prepared with either gold stud or plated bumps.

The dies recognized by pattern recognition are ejected from the wafer by the die collet, flipped 180° and handed over to the bond tool at a defined position. The position of the die on the bond tool after handover is checked by pattern recognition. Afterwards the die can be accurately placed with the bumps exactly matching the pads on the substrate. During the ultrasonic bonding process a defined power profile is used and the deformation of the bumps is measured and displayed in real time. The positioning accuracy is better than 15 μm. The cycle time is 1.4-1.7 s per chip without the bonding process time, which is about 0.2-0.5 s.

For more information, visit our Web site: www.hesse-knipps.com