Zig-Zag Die Stack Interconnect Using Conductive Pillars
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Solution Overview
Problem
Existing methods for increasing the density of active semiconductor circuitry in integrated circuit chip packages while minimizing package size are limited in efficiently connecting stacked die configurations, particularly in achieving a high-density, compact footprint.
Innovation Solution
The development of a tiered offset stacked die assembly in a zig-zag configuration, where interconnect edges of lower and upper tiers face in different directions, with pillars of electrically conductive material formed on bond pads to connect die-to-die and tier-to-support, using curable conductive materials deposited in a flowable form and hardened to form continuous interconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If die are stacked one over another to increase circuitry density, then the package footprint is reduced, but the complexity of electrical interconnection increases
Solution Approach 1:
The patent divides the interconnection system into modular components: offset stacked die units with interconnect pads, and separate conductive epoxy traces for electrical connection. This segmentation allows independent optimization of each module and simplifies the overall assembly process while maintaining high density.
Solution Approach 2:
The patent introduces conductive epoxy material as an intermediary substance between the interconnect pads on stacked die and the package substrate. This intermediary enables flexible electrical connection that accommodates the offset configuration and simplifies the interconnection process compared to direct rigid bonding.
2Reliability
If offset stacked die configurations are used to reveal interconnect pads, then die-to-die electrical connection is enabled, but the manufacturing process becomes more complex
Solution Approach 1:
The patent changes the positional parameter of die in the stack, creating offset configurations where die are deliberately misaligned. This parameter change reveals interconnect pads on lower die while maintaining electrical connection reliability through the use of conductive epoxy that can bridge the offset gaps.
Solution Approach 2:
The patent employs curable conductive epoxy materials that undergo chemical transformation (curing) to establish reliable electrical connections. The curing process accelerates the formation of stable conductive pathways, ensuring reliable die-to-die and die-to-substrate connections despite the offset configuration.
3Reliability
If modular offset stacked die units are assembled in zig-zag configuration, then interconnect integrity is enhanced, but the assembly time increases
Solution Approach 1:
The patent employs asymmetric zig-zag configuration where alternating die units are offset in opposite directions. This asymmetric arrangement enhances interconnect integrity by distributing mechanical stresses and creating redundant connection paths, while the modular nature allows for efficient assembly through standardized interfaces.
Solution Approach 2:
The patent prepares offset stacked die units with pre-configured interconnect pads and preliminary alignment features before final assembly. This preliminary action ensures that when units are stacked in zig-zag configuration, the interconnect alignment is already optimized, reducing assembly time while maintaining high interconnect integrity.
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
This approach enables efficient electrical interconnection of stacked die, allowing for higher density and smaller package size by ensuring reliable die-to-die and tier-to-support connections, enhancing the modular design and interconnect integrity.
Implementation Method 1
pillars of electrically conductive material are formed on a set of bond pads at a mount side of the support, and the elevated die is electrically connected to the support, by traces of an electrically conductive material contacting interconnect pads on the die to the pillars, and through the pillars to the support
Implementation Method 2
using curable conductive materials deposited in a flowable form and hardened to form continuous interconnections
Data Source
AI summary
A die (or of a stack of die) is mounted over and elevated above a support, and is electrically connected to circuitry in the support. Pillars of electrically conductive material are formed on a set of bond pads at a mount side of the support, and the elevated die (or at least one die in the elevated stack of die) is electrically connected to the support, by traces of an electrically conductive material contacting interconnect pads on the die to the pillars, and through the pillars to the support. Also, tiered offset stacked die assemblies in a zig-zag configuration, in which the interconnect edges of a first (lower) tier face in a first direction, and the interconnect edges of a second (upper) tier, stacked over the first tier, face in a second direction, different from the first direction, are electrically connected to a support. Die in the first tier are electrically interconnected die-to-die, and the tier is electrically connected to a support, by traces of an electrically conductive material contacting interconnect pads on the die and a first set of bond pads on the support. Pillars of a electrically conductive material are formed on a second set of bond pads, and die in the second tier are electrically interconnected die-to-die, and the tier is electrically connected to the support, by traces of an electrically conductive material contacting interconnect pads on the die to the pillars, and through the pillars to the substrate.