RDL-last Package Thermal Stress Management
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Solution Overview
Problem
The increasing complexity of integrated circuit packages, which include multiple device dies and interconnects, faces challenges in heat dissipation and fine-pitch Redistribution Line (RDL) formation due to thermal mismatch and polymer usage, leading to structural stress and feasibility issues in RDL-last processes.
Innovation Solution
The method involves bonding device dies to a substrate with metal-to-metal direct bonding, using oxide-based gap-filling materials without polymers, forming vias, and creating fine-pitch RDLs through damascene processes, along with heat spreaders for efficient heat dissipation, and micro-channels for coolant flow, to reduce thermal mismatch and enable stress absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymer-based molding compounds are used to encapsulate device dies, then the package structure is simplified and ease of manufacture is improved, but thermal mismatch occurs leading to structural stress and RDL formation feasibility deteriorates
Solution Approach 1:
The patent extracts and removes polymer materials from the package structure entirely. Instead of using polymer-based molding compounds to encapsulate device dies, the invention employs alternative non-polymer materials that eliminate thermal mismatch issues while maintaining package integrity and enabling RDL-last processes.
Solution Approach 2:
The invention changes the material parameter from polymer-based to non-polymer-based encapsulation materials. This parameter change fundamentally alters the thermal properties of the package, eliminating thermal mismatch between different components and enabling reliable fine-pitch RDL formation after device bonding.
2Adaptability or versatility
If fine-pitch RDLs are formed after device bonding (RDL-last process), then device functionality and integration are improved, but the process complexity increases and manufacturing difficulty worsens due to thermal mismatch and stress
Solution Approach 1:
The patent applies preliminary action by preparing the substrate and interposer with pre-formed patterns, alignment marks, and structural features before device bonding. This preliminary preparation enables subsequent RDL formation to proceed more easily despite the complex RDL-last process, as the foundation is already in place to guide and support the fine-pitch RDL fabrication.
Solution Approach 2:
The invention introduces an interposer as an intermediary component between the substrate and device dies. This interposer serves as a mediation layer that facilitates thermal management, mechanical support, and electrical interconnection, thereby enabling the RDL-last process to succeed despite the inherent complexities of forming fine-pitch RDLs after device bonding.
3Temperature
If heat spreaders are added to dissipate heat from device dies, then thermal management is improved, but the package structure becomes more complex and stress management becomes more difficult
Solution Approach 1:
The patent merges the heat spreader functionality with the existing package substrate or interposer structure. Instead of adding heat spreaders as separate, independent components that increase complexity, the invention integrates thermal management functions into already-present structural elements, thereby improving heat dissipation without proportionally increasing package complexity.
Solution Approach 2:
The invention makes the package substrate or interposer multi-functional by enabling it to serve both as a mechanical support structure and as a heat spreader. This universality allows a single component to fulfill multiple roles, improving thermal management while avoiding the need for additional dedicated heat dissipation components that would increase overall package complexity.
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 allows for the formation of thin, high-density fine-pitch RDLs, improved heat dissipation, and stress management, enhancing the feasibility and reliability of RDL-last processes in complex package structures.
Implementation Method 1
A heat spreader may be attached to the top surfaces of the device dies in order to dissipate the heat generated in the device dies
Implementation Method 2
micro-channels for coolant flow, to reduce thermal mismatch and enable stress absorption
Data Source
AI summary
A method includes bonding a first device die and a second device die to a substrate, and filling a gap between the first device die and the second device die with a gap-filling material. A top portion of the gap-filling material covers the first device die and the second device die. Vias are formed to penetrate through the top portion of the gap-filling material. The vias are electrically coupled to the first device die and the second device die. The method further includes forming redistribution lines over the gap-filling material using damascene processes, and forming electrical connectors over and electrically coupling to the redistribution lines.