Multi-Foot Package Lid Structure for TIM Stress Mitigation
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Solution Overview
Problem
Existing package assemblies face challenges in preventing cracking and delamination of thermal interface material (TIM) films, particularly with larger sizes, due to stress issues.
Innovation Solution
Incorporating a package lid design with an outer foot and embedded inner feet, along with a novel substrate shape and adhesive pattern, to mitigate stress on the TIM film, thereby enhancing the reliability of the assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional package lid design with a single foot is used, then the structure is simple and manufacturing is easy, but stress on the TIM film increases leading to cracking and delamination
Solution Approach 1:
The package lid foot is segmented into multiple distinct feet (first foot, second foot, third foot, fourth foot) positioned at different locations on the substrate. This segmentation distributes the mechanical stress from the TIM film across multiple attachment points, preventing stress concentration that would lead to cracking and delamination.
Solution Approach 2:
Each foot is positioned at a specific location on the substrate with optimized dimensions and spacing. The local structural quality is enhanced by having feet with specific width, length, and thickness parameters that are tailored to the local stress requirements, providing targeted stress mitigation where needed most.
2Area of stationary object
If the package lid size is increased to accommodate larger chip-on-wafer dies, then the packaging capacity is improved, but stress on the TIM film increases causing cracking and delamination
Solution Approach 1:
The package lid is divided into multiple feet that are distributed across the larger substrate area. This segmentation allows the lid to span greater distances while maintaining structural integrity through multiple localized attachment points, enabling larger package sizes without compromising TIM film reliability.
Solution Approach 2:
The stress distribution problem is solved by transitioning from a single-point attachment to a multi-point distributed attachment across the substrate surface. This dimensional distribution of attachment points allows the package lid to accommodate larger chip-on-wafer dies while maintaining TIM film integrity through spatial distribution of mechanical loads.
3Reliability
If additional inner feet are embedded in the substrate, then stress mitigation on the TIM film is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The multiple feet are integrated as a unified structure with the package lid, formed simultaneously as a single component. This merging of multiple feet into one integrated part simplifies manufacturing by eliminating the need for separate assembly steps for each foot, while still providing the stress mitigation benefits of multiple attachment points.
Solution Approach 2:
The package lid structure serves multiple functions: it provides the primary protective cover, acts as a mounting platform for the TIM film and semiconductor devices, and simultaneously functions as a stress distribution mechanism through its multi-foot design. This multi-functionality consolidates several components into one, simplifying manufacturing.
Data Source
AI summary
A package assembly includes a package substrate, a package lid located on the package substrate and including a plate portion, an outer foot extending from the plate portion, and an inner foot having a height greater than or equal to a height of the outer foot, extending from the plate portion and including a first inner foot corner portion located inside a first corner of the outer foot, and an adhesive that adheres the outer foot to the package substrate and adheres the inner foot to the package substrate.