IC Package Thermal Interface Layout for Heat and Stress Balance
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Solution Overview
Problem
Heat dissipation and structural integrity challenges in 3DIC packages due to heat generation and warping, with existing thermal interface materials (TIM) and adhesives failing to balance thermal conductivity and stress absorption effectively.
Innovation Solution
A hybrid arrangement of two types of TIMs and adhesives with different properties are used, where a first TIM with higher thermal conductivity and a second TIM with lower Young's modulus are applied at corners and non-corners respectively, and adhesives with varying structural filler contents are used to attach a lid or ring, enhancing stress absorption and heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single thermal interface material (TIM) is used to bond device dies to the package substrate, then thermal conductivity is improved, but stress absorption capability deteriorates
Solution Approach 1:
The bonding interface is segmented into two distinct TIM layers: a first TIM layer with high thermal conductivity for heat dissipation, and a second TIM layer with high stress absorption capability for mechanical compliance. This segmentation allows each layer to specialize in one function, resolving the contradiction between thermal conductivity and stress absorption that prevents a single material from optimizing both properties simultaneously.
Solution Approach 2:
The patent employs a composite TIM structure consisting of two different materials with complementary properties. The first TIM (e.g., metal-based or ceramic-filled) provides superior thermal conductivity, while the second TIM (e.g., polymer-based or elastomeric) provides superior stress absorption. This composite approach creates a bonded interface that achieves both high heat dissipation and high mechanical compliance, which cannot be accomplished with a single homogeneous material.
2Ease of manufacture
If the package substrate lacks structural reinforcement, then ease of manufacture is improved, but structural integrity deteriorates due to warping
Solution Approach 1:
The lid is selectively positioned to provide structural reinforcement only at critical locations where warping occurs during assembly and operation. Rather than requiring the entire package substrate to be heavily reinforced, the lid locally counteracts thermal expansion stresses and mechanical loads at the device die interfaces, maintaining structural integrity while preserving ease of manufacture for the overall package structure.
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 effectively dissipates heat and maintains structural integrity by balancing thermal conductivity and stress absorption, preventing delamination and warping in 3DIC packages.
Implementation Method 1
a first thermal interface material disposed at corners of a top surface of the package component... A thermal conductivity of the second thermal interface material is greater than a thermal conductivity of the first thermal interface material
Implementation Method 2
an adhesive layer sandwiched between the lower edge of the lid and the substrate
Data Source
AI summary
A package structure is provided. The package structure includes a substrate, a die bonded to the substrate, a lid disposed over the die and the substrate, and an interface structure sandwiched between the die and the lid and including a first thermal interface material disposed at corners of a top surface of the die, and a second thermal interface material disposed a rest of the top surface of the die. A Young's modulus of the first thermal interface material is smaller than a Young's modulus of the second thermal interface material.