Peripheral Dummy Dies Reduce Warpage in Reconstructed Wafer Packages
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Solution Overview
Problem
Large three-dimensional integrated circuits experience warpage due to stress generated by the contraction of molding compounds, which worsens with increasing package size, leading to increased stress and warpage, and conventional dummy dies do not adequately address this issue.
Innovation Solution
Placing dummy dies in peripheral regions of reconstructed wafers with coefficients of thermal expansion closer to functional dies than the encapsulant, surrounding functional dies, to reduce stress and warpage by occupying space that would otherwise be filled by the encapsulant, and distributing these dummy dies uniformly in the peripheral region to improve packaging yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If package size is increased to accommodate larger three-dimensional integrated circuits, then functional requirements are met, but warpage and stress increase due to greater distance for stress accumulation
Solution Approach 1:
The patent applies local quality by placing dummy dies specifically in peripheral regions of the package rather than uniformly distributing them. This localized placement targets the areas where warpage and stress accumulation are most problematic (the edges and corners of large packages), providing structural support precisely where needed to counteract the warpage caused by large package size.
Solution Approach 2:
The patent employs asymmetry by concentrating dummy dies in peripheral regions rather than symmetrically distributing them across the entire package. This asymmetric distribution creates additional structural support at the edges and corners where stress accumulation is most severe in large packages, effectively counteracting warpage without requiring dummy dies throughout the entire package area.
2Reliability
If conventional dummy dies are used to reduce warpage, then some stress compensation is achieved, but packaging yield remains insufficient due to inadequate stress reduction
Solution Approach 1:
The patent improves packaging yield by placing dummy dies specifically in peripheral regions where they most effectively counteract warpage and stress. This localized placement in edge and corner areas provides maximum stress compensation with minimum dummy die usage, thereby improving yield by reducing defects in the most critical regions without requiring excessive dummy dies that would reduce functional die count.
Solution Approach 2:
The patent changes the parameter of dummy die placement from uniform distribution to concentrated peripheral placement. This parameter change optimizes the stress compensation effect by positioning dummy dies where the molding compound contraction causes the most severe warpage (at the periphery), thereby achieving better warpage control and improved packaging yield with fewer dummy dies.
3Strength
If dummy dies are placed side-by-side with functional dies in conventional packages, then some structural support is provided, but stress and warpage are not adequately reduced
Solution Approach 1:
The patent applies local quality by relocating dummy dies from side-by-side placement with functional dies to concentrated placement in peripheral regions. This localized positioning provides structural support precisely where the molding compound contraction generates the most severe stress (at the edges and corners), effectively reducing overall package stress without occupying space that would be used for functional dies.
Solution Approach 2:
The patent employs asymmetry by moving dummy dies from symmetric side-by-side placement to asymmetric peripheral concentration. This asymmetric arrangement provides optimal structural support at the stress-prone peripheral regions, effectively reducing package stress and warpage while maximizing the utilization of dummy dies for stress compensation rather than uniform distribution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The placement of dummy dies in peripheral regions reduces warpage and improves packaging yield by minimizing stress and maintaining focus in lithography processes, especially at the edges of the reconstructed wafers, thereby enhancing the overall performance and reliability of the packages.
Implementation Method 1
dummy dies in peripheral regions of reconstructed wafers with coefficients of thermal expansion closer to functional dies than the encapsulant
Data Source
AI summary
A method includes placing a plurality of functional dies over a carrier, placing a plurality of dummy dies over the carrier, encapsulating the plurality of functional dies and the plurality of dummy dies in an encapsulant, and forming redistribution lines over and interconnecting the plurality of functional dies. The redistribution lines, the plurality of functional dies, the plurality of dummy dies, and the encapsulant in combination form a reconstructed wafer. The plurality of functional dies are in a center region of the reconstructed wafer, and the plurality of dummy dies are in a peripheral region of the reconstructed wafer, with the peripheral region encircling the center region. The reconstructed wafer is de-bonded from the carrier. The reconstructed wafer is bonded to a package component selected from the group consisting essentially of an interposer, a package substrate, a printed circuit board, a thermal module, and combinations thereof.