Package Stacking Interconnects for Warpage Mitigation
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Solution Overview
Problem
Current package-on-package (PoP) stacking techniques face limitations due to limited space between stacked packages, leading to potential damage from thermal expansion and warping, which complicates assembly and reduces reliability.
Innovation Solution
The method involves forming a base package with a substrate and integrated circuit die, surrounded by stacking interconnects, and a stacked package with interconnects that attach to the base package's interconnects, forming a solder column through reflow, enhancing electrical connectivity and reducing warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If package-on-package stacking is implemented to increase packaging density, then packaging density is improved, but the limited space between stacked packages causes thermal expansion and warping that damages die and interconnects
Solution Approach 1:
The patent implements package-on-package stacking where a second package is mounted on top of a first package, creating a nested vertical arrangement. This nesting approach increases packaging density by utilizing the vertical dimension while maintaining electrical interconnects between the stacked packages through controlled formation of solder columns that provide both electrical connection and mechanical tolerance for thermal expansion.
Solution Approach 2:
The patent forms solder columns with controlled height and composition (including copper core and solder alloy layers) that act as cushioning elements between the stacked packages. These pre-formed interconnect structures accommodate thermal expansion and warping movements that occur during operation, preventing damage to die and interconnects while maintaining reliable electrical connections.
2Volume of moving object
If the space between stacked packages is reduced to improve miniaturization, then package size is decreased, but mechanical damage occurs due to warping and thermal expansion
Solution Approach 1:
The patent reduces package footprint by stacking packages vertically in a nested configuration, minimizing the horizontal space occupied while maintaining adequate vertical clearance between packages for thermal management and mechanical tolerance.
Solution Approach 2:
The controlled solder column interconnects are pre-formed with specific height and material composition to provide cushioning that absorbs thermal expansion and warping stresses, preventing mechanical damage even when packages are closely stacked for miniaturization.
Solution Approach 3:
The interconnect structure uses composite materials including copper core for electrical conductivity and thermal management, surrounded by solder alloy layers for mechanical flexibility and thermal expansion accommodation. This composite structure provides both electrical connection and mechanical tolerance for thermal effects.
3Reliability
If conventional solder ball matrix interconnects are used for package stacking, then electrical connectivity is achieved, but the small stand-off height limits available space for base package components
Solution Approach 1:
The patent replaces conventional solder ball matrices with composite interconnect structures featuring copper cores surrounded by solder alloy layers. This composite construction provides enhanced electrical connectivity with controlled impedance while the layered structure allows for optimized height, providing sufficient stand-off for base package components such as heat spreaders and shields.
Solution Approach 2:
The patent changes the physical parameters of the interconnect structure by controlling solder column height, copper core diameter, and solder alloy composition. These parameter adjustments optimize both electrical connectivity and mechanical properties, providing adequate clearance for components while maintaining reliable electrical connections between stacked packages.
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 increases packaging density, reliability, and manufacturing yield by providing high-density electrical connectivity and shielding, while minimizing warpage and mechanical damage, thus improving the assembly process and overall performance.
Implementation Method 1
forming a stacked solder column by reflowing the stacking interconnects
Data Source
AI summary
A method of manufacture of an integrated circuit package system includes: forming a base package including: fabricating a base package substrate having a component side and a system side, coupling a first integrated circuit die to the component side, and coupling stacking interconnects to the component side to surround the first integrated circuit die; forming a stacked integrated circuit package including: fabricating a stacked package substrate having a chip side, coupling a lower stacked integrated circuit die to the chip side, and attaching on a coupling side, of the stacked package substrate, the stacking interconnects; stacking the stacked integrated circuit package on the base package including the stacking interconnects of the stacked integrated circuit package on the stacking interconnects of the base package; and forming a stacked solder column by reflowing the stacked interconnects.