Package-on-Package Thermal Isolation to Minimize Warpage
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Solution Overview
Problem
Conventional package-on-package structures face issues with excessive heat generation from the bottom die causing thermal stress and warpage, leading to damage and cracks in the solder balls, despite the use of molding compounds.
Innovation Solution
Incorporating a thermal isolation material with low thermal conductivity, such as a porous film or seal ring with an air gap, to insulate the top die from the heat generated by the bottom die, thereby controlling warpage and enhancing mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional package-on-package structure is used with molding compounds, then the structure provides mechanical support and electrical connectivity, but excessive heat from the bottom die causes thermal stress and warpage leading to solder ball cracks
Solution Approach 1:
An underfill material is introduced as an intermediary substance between the substrate and the package component. This underfill material has different thermal expansion properties compared to conventional molding compounds, serving as a buffer that absorbs thermal stress and reduces warpage caused by heat generation from the bottom die, thereby preventing solder ball cracks while maintaining structural integrity
Solution Approach 2:
The thermal expansion coefficient and other physical parameters of the underfill material are specifically optimized to match or compensate for the thermal characteristics of the package component and substrate. By changing the material parameters of the underfill, the system achieves better thermal stress distribution and reduced warpage under elevated temperature conditions
2Strength
If molding compounds are used in the package-on-package structure, then mechanical strength is provided, but heat dissipation is insufficient causing damage to the top die
Solution Approach 1:
The underfill material acts as a thermal management intermediary between the heat-generating bottom die and the top die. While it provides mechanical support similar to molding compounds, its thermal properties are optimized to facilitate better heat dissipation pathways, preventing excessive heat accumulation that could damage the top die
3Productivity
If the bottom die is positioned close to the top die for high density, then space efficiency is improved, but thermal coupling increases causing warpage and reliability issues
Solution Approach 1:
The underfill material serves as a thermal decoupling intermediary that allows the bottom die to be positioned close to the top die for high density while simultaneously providing thermal isolation. This mediator reduces thermal coupling between the dies, maintaining thermal stability even when components are in close proximity
Solution Approach 2:
The underfill material is applied locally in the critical thermal stress regions between the bottom die, substrate, and solder balls. This localized application provides targeted thermal management where it is most needed, allowing high density packaging while maintaining local thermal stability
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 thermal isolation material effectively reduces heat transfer between the package components, minimizing thermal stress and warpage, and enhancing the structural integrity of the package-on-package structure.
Implementation Method 1
a thermal isolation material is attached to the bottom die, wherein the thermal isolation material thermally insulates the top die from the bottom die
Data Source
AI summary
A semiconductor device includes a first package component and a second package component. The first package component has a first die formed on a first substrate. A second package component has a second die formed on a second substrate. A thermal isolation material is attached on the first die, wherein the thermal isolation material thermally insulates the second die from the first die, and the thermal isolation material has a thermal conductivity of from about 0.024 W/mK to about 0.2 W/mK. A first set of conductive elements couples the first package component to the second package component.