Speed and Accuracy Optimization for Fan-Out Die Placement

Abstract

Die placement accuracy requirements for fan-out wafer level packaging vary widely based on the process flow selected. Each process flow has attributes that define the challenges and requirements for die placement accuracy. Different fan-out process flows can require die placement to be done face-up or face-down. Alignment schemes for die placement can include global alignment, local alignment or a combination of both methods. Heat may be required for the carrier or die and placement force must be carefully controlled. Predictable placement of die prior to reconstitution is a key enabling technology for advanced fan-out products requiring fine line and space redistribution layers but it has the potential to improve yield in any of the fan-out processes. Accuracy requirements are driven by the photolithography done after reconstitution. Steppers are used with the assumption die to die spacing is repeatable within a given field area, however die spacing will inevitably be somewhat irregular due normal proces...