TABLE OF CONTENTS Flip chip device assembly entails three basic steps: a die pick-up, an alignment and placement to the package/substrate footprint, and a final attachment or bonding step. For pick-up, die can be presented in various carriers much the same as those used for chip and wire assembly including waffle packs, GelPak , a reel tape or a sawed wafer mounted on a film frame. The die can be either face-up or facedown. If face-up the die must be picked and flipped for alignment and placement.
For attachment, the face-down die must be aligned (bumps to pads) with the corresponding footprint on the package/substrate. The alignment, in a manual mode, is achieved by simultaneously viewing the bumped side of the die and the package footprint . An operator manipulates the die in x, y, and theta to achieve proper alignment. Figure 11-1 graphically illustrates the alignment of a flip chip using a bi-directional mirror to simultaneously view both the die and package footprint.
For fully automated operation optical pattern recognition is added for the alignment to eliminate operator dependence and realize complete machine control insuring precise placement accuracy and repeatability.
Some force may be required for placement of the die. The amount of force will depend upon the bump metallurgy and the attachment process. For example, when there are multiple die involved and there is a batch ...
