Chip on Film Package Dam Structures for Thermal Stress Relief
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Solution Overview
Problem
Chip-on-film (CoF) packages face challenges in efficiently managing thermal expansion differences between the base film and heat radiator, leading to stress concentration and potential defects in the bump structure, which affects heat radiation and thermal fatigue characteristics.
Innovation Solution
Incorporating dam structures in the adhesive layer between the base film and heat radiator, these structures overlap the bump structure to alleviate stress concentration and enhance thermal conductivity, improving heat radiation and thermal fatigue resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat radiator is directly coupled to the base film, then heat radiation efficiency is improved, but thermal expansion difference causes stress concentration and potential defects in the bump structure
Solution Approach 1:
The adhesive layer is segmented into multiple regions with different thicknesses, creating thin and thick adhesive regions. This segmentation allows differential thermal expansion between the base film and heat radiator to be accommodated in the thick regions while maintaining good thermal contact in the thin regions, thereby resolving the contradiction between heat radiation efficiency and bump structure integrity
Solution Approach 2:
The adhesive layer exhibits non-uniform local quality with varying thickness across different locations. The thin adhesive regions provide efficient thermal conduction paths, while the thick adhesive regions provide stress relief and compliance. This local variation in adhesive layer quality simultaneously achieves both heat radiation efficiency and bump structure protection
2Temperature
If the adhesive layer is made uniformly thin, then heat radiation efficiency is improved, but stress concentration during thermal expansion increases
Solution Approach 1:
The adhesive layer is divided into multiple thickness zones rather than being uniformly thin. This segmentation creates a gradient structure where thermal conduction is optimized in thin regions while stress absorption is enhanced in thick regions, resolving the contradiction between heat radiation efficiency and stress concentration
3Reliability
If thermal expansion difference between base film and heat radiator is accommodated, then bump structure reliability is improved, but heat radiation efficiency may be compromised
Solution Approach 1:
The adhesive layer is designed with spatially varying thickness to perform dual functions: thick regions accommodate thermal expansion differences to protect the bump structure, while thin regions maintain efficient thermal conduction paths. This local differentiation resolves the contradiction between reliability and heat radiation efficiency
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 dam structures effectively reduce thermal fatigue and enhance heat radiation characteristics, thereby improving the reliability of the CoF package and display apparatus by mitigating stress concentration and ensuring efficient heat dissipation.
Implementation Method 1
a heat radiator on the lower surface of the base film and underlying the semiconductor chip
Implementation Method 2
an adhesive layer between the lower surface of the base film and the heat radiator
Data Source
AI summary
A chip-on-film (CoF) package and a display apparatus, the package including a base film having an upper surface and a lower surface facing each other; a conductive line on the upper surface of the base film; a semiconductor chip on the upper surface of the base film and connected to the conductive line through a bump structure; a heat radiator on the lower surface of the base film and underlying the semiconductor chip; an adhesive layer between the lower surface of the base film and the heat radiator; and a plurality of dam structures in the adhesive layer and overlapping the bump structure.