Fan-Out Package Stress Buffer Structure for Underfill Crack Mitigation
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Solution Overview
Problem
Interfaces between fan-out wafer level packages and underfill material portions experience mechanical stress during assembly and use, leading to potential cracking and damage to semiconductor dies and packaging substrates.
Innovation Solution
Incorporation of a stress buffer structure with a lower Young's modulus and higher coefficient of thermal expansion than the molding compound, which is integrated into the fan-out package to absorb mechanical and thermal stress, reducing deformation and crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If underfill material is used to support the fan-out package, then mechanical strength is improved, but cracking occurs at the interface between the fan-out package and underfill material due to mechanical stress
Solution Approach 1:
A stress buffer structure is introduced as an intermediary component between the fan-out package and the underfill material. This stress buffer structure has a Young's modulus lower than that of the molding compound, allowing it to absorb mechanical stress and prevent stress concentration at the interface, thereby preventing cracking while maintaining overall mechanical strength
Solution Approach 2:
The stress buffer structure utilizes materials with specific parameter characteristics - a Young's modulus lower than the molding compound and a coefficient of thermal expansion higher than the molding compound. These parameter changes enable the stress buffer to deform more easily under mechanical stress and compensate for thermal expansion differences, reducing stress at critical interfaces
2Strength
If molding compound with high Young's modulus is used for structural support, then mechanical rigidity is improved, but thermal stress and mechanical stress concentration occurs at interfaces
Solution Approach 1:
The stress buffer structure uses materials with a Young's modulus lower than the molding compound, creating a gradient in mechanical properties. This parameter change allows the stress buffer to act as a stress-absorbing layer that prevents stress concentration at interfaces while the high-modulus molding compound maintains overall structural rigidity
Solution Approach 2:
The stress buffer structure employs materials with a coefficient of thermal expansion higher than the molding compound. This thermal expansion characteristic allows the stress buffer to compensate for differential thermal expansion between the fan-out package and the molding compound, reducing thermal stress concentration at interfaces during temperature variations
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 stress buffer structure effectively mitigates stress-related deformation and cracking, enhancing the reliability and integrity of the fan-out package by absorbing mechanical and thermal stress more efficiently than the molding compound.
Implementation Method 1
at least one stress buffer structure (907) located on the interposer structure (920) and comprising a stress buffer material having a first Young's modulus
Implementation Method 2
the at least one stress buffer structure (907) may include a stress buffer material having a first coefficient of thermal expansion; and the molding compound material may include a molding compound material having a second coefficient of thermal expansion that may be lower than the first coefficient of thermal expansion
Data Source
AI summary
A fan-out package includes at least one semiconductor die attached to an interposer structure, a molding compound die frame laterally surrounding the at least one semiconductor die and including a molding compound material, and at least one stress buffer structure located on the interposer structure and including a stress buffer material having a first Young's modulus. The molding compound die frame includes a molding compound material having a second Young's modulus that is greater than the first Young's modulus.