Thin Substrate PoP Structure Thermal Warping
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Solution Overview
Problem
Thin and fine pitch package-on-package (PoP) semiconductor packages face warping issues due to thermal characteristic differences between substrates and encapsulants, particularly in top packages with thin or coreless substrates, leading to mechanical strength deficiencies and potential performance failures.
Innovation Solution
Balancing thermal properties in the top package by applying encapsulant on both sides, including a recess to expose the substrate and terminals, which helps in reducing thermal stresses and warping, while maintaining a thin overall package thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If encapsulant is applied only on one side of the top package, then the package structure is simpler, but thermal stress imbalance causes warping
Solution Approach 1:
The patent applies encapsulant on both sides of the top package substrate, creating a symmetric structure that balances thermal properties. This symmetric encapsulation approach counteracts the asymmetric thermal expansion differences between the substrate and encapsulant material, preventing warping while maintaining structural simplicity.
2Length of stationary object
If thin or coreless substrate is used in the top package, then package thickness is reduced, but mechanical strength decreases leading to increased warping
Solution Approach 1:
The patent changes the thermal parameters of the package by applying encapsulant on both sides of the thin substrate, balancing the thermal expansion forces. This allows the use of thin or coreless substrates without excessive warping, as the symmetric encapsulation compensates for the reduced mechanical strength by creating balanced thermal stress distribution.
3Productivity
If pitch between terminals is reduced, then package density increases, but warping potential increases due to thermal characteristic differences
Solution Approach 1:
The patent uses symmetric encapsulation on both sides of the substrate to balance thermal properties, which counteracts the warping forces that become more significant as terminal pitch is reduced. This allows for higher package density with finer pitch terminals while maintaining warping resistance through balanced thermal stress distribution.
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 effectively reduces warping in top packages, enhances the reliability and performance of PoP packages, and supports fine pitch and thin or coreless substrate integration by balancing thermal stresses and maintaining a reduced package thickness.
Implementation Method 1
Warping may be caused by the difference in thermal characteristics of materials used in the package (e.g., the substrate and an encapsulant applied to the substrate)
Data Source
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AI summary
A PoP (package-on-package) package includes a bottom package with a substrate encapsulated in an encapsulant with a die coupled to the top of the substrate. At least a portion of the die is exposed above the encapsulant on the bottom package substrate. A top package includes a substrate with encapsulant on both the frontside and the backside of the substrate. The backside of the top package substrate is coupled to the topside of the bottom package substrate with at least part of the die being located in a recess in the encapsulant on the backside of the top package substrate.