Package-to-Heat Sink Interface Structure for Warpage-Resistant Adhesion
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Solution Overview
Problem
In Three-Dimensional Integrated Circuits (3DIC), device dies experience warpage due to temperature variation, leading to strain on the adhesion between the devices and the metal lid, which can result in delamination and hinder heat dissipation.
Innovation Solution
Implementing an adhesive layer selectively dispensed over the underfill and molding compound, followed by a thermal interface material (TIM) deposition, and optionally using interface metal layers or convex lids to enhance adhesion and thermal conductivity, thereby preventing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If device dies are bonded to a package substrate with a metal lid to dissipate heat, then heat dissipation is improved, but device warpage due to temperature variation causes strain on adhesion and leads to delamination
Solution Approach 1:
The patent introduces an adhesive layer as an intermediary between the package substrate and the metal lid. This adhesive layer acts as a mediator that accommodates the thermal expansion and contraction differences between the substrate and lid, reducing stress concentration and preventing delamination while maintaining effective heat dissipation pathways.
Solution Approach 2:
The patent employs a composite structure consisting of multiple materials (package substrate, adhesive layer, metal lid) with different thermal and mechanical properties. This composite design allows each layer to contribute its specific characteristics - the substrate provides structural support, the adhesive provides stress relief, and the lid provides heat dissipation - while working together to resolve the contradiction between heat dissipation and adhesion reliability.
2Power
If a metal lid is bonded to the package substrate to engage device dies, then heat dissipation capability is enhanced, but warpage strain causes delamination that hinders heat dissipation
Solution Approach 1:
The adhesive layer is applied beforehand to the package substrate before bonding the metal lid. This pre-applied adhesive layer serves as a cushioning interface that anticipates and absorbs the thermal stress and warpage forces that will occur during thermal cycling, preventing direct stress transmission that would cause delamination and maintain structural integrity throughout operation.
3Temperature
If device dies experience warpage due to temperature variation, then thermal cycling occurs, but this warpage puts strain on adhesion between devices and metal lid
Solution Approach 1:
The patent changes the mechanical parameters of the bonding interface by introducing an adhesive layer with specific viscoelastic properties. This adhesive layer can change its stiffness and damping characteristics in response to temperature variations, allowing it to accommodate warpage-induced stresses while maintaining adequate bond strength, thus resolving the contradiction between thermal cycling and adhesion strength.
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 solution improves adhesion between the package component and the metal lid, maintaining effective heat dissipation and structural integrity by minimizing delamination during thermal cycles.
Implementation Method 1
an adhesive layer selectively dispensed over the underfill and the molding compound
Implementation Method 2
a thermal interface material (TIM) deposited over the adhesive layer, the first die, and the second die
Data Source
AI summary
A package structure is provided. The package structure includes a substrate, a package component bonded to the substrate, a lid disposed over the package component and the substrate, and an interface structure sandwiched between the package component. The package component includes a first die, a second die laterally spaced apart from the first die by an underfill, and a molding compound adjacent the first die and the second die. The interface structure includes an adhesive layer disposed over the underfill and the molding compound, and a thermal interface material (TIM) layer over the adhesive layer, the first die and the second die.