Embedded Chip-on-Film Structure for Thin Stable Bonding
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Solution Overview
Problem
Traditional chip-on-film packaging methods increase the overall thickness of flexible substrates and chips, leading to space constraints and instability due to water vapor interference and chip displacement, especially when rigid chips are bonded on flexible substrates.
Innovation Solution
A chip-on-film packaging structure featuring a flexible substrate with a groove and protrusion matching the chip's shape, where the chip is embedded with a groove on its surface and bonded using an anisotropic conductive film, reducing thickness and enhancing bonding stability through precise etching and sealant filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rigid chip is bonded on a flexible substrate using traditional COF packaging method, then the chip can be mounted on the flexible substrate, but the overall thickness increases and bonding stability decreases due to water vapor interference and chip displacement
Solution Approach 1:
The chip is embedded into a groove formed on the flexible substrate, creating a nested structure where the chip sits within the substrate rather than on top of it. This nesting approach reduces the overall thickness while improving bonding stability by increasing the contact area between the chip and substrate.
Solution Approach 2:
The invention transitions from a planar bonding interface to a three-dimensional groove structure. By forming a groove with specific depth and width dimensions, the bonding interface is extended in the vertical dimension, increasing the bonding area and stability without significantly increasing the overall thickness.
2Reliability
If the chip is bonded on the flexible substrate without a groove structure, then the structure is simpler, but the bonding tightness is insufficient leading to chip displacement
Solution Approach 1:
The groove structure creates a nested configuration where the chip is partially embedded in the substrate. This provides mechanical interlocking that enhances bonding tightness and prevents chip displacement, while the groove can be formed using standard photolithography and etching processes.
Solution Approach 2:
The groove dimensions (depth, width, shape) are optimized to achieve the desired bonding tightness. By adjusting parameters such as groove depth (10-100 microns) and width, the bonding performance is improved without excessive structural complexity.
3Reliability
If the groove depth is increased to improve bonding stability, then the bonding strength increases, but the overall thickness reduction effect decreases
Solution Approach 1:
The groove depth is optimized within a specific range (10-100 microns) to achieve the balance between bonding strength and thickness reduction. This parameter optimization ensures sufficient bonding strength while maintaining the thickness reduction benefit of the embedded structure.
Solution Approach 2:
The groove depth is designed to be sufficient for achieving strong bonding without being excessively deep. The partial embedding approach provides adequate bonding strength while preserving the overall thin profile of the flexible substrate assembly.
Data Source
AI summary
The present invention provides a chip-on-film (COF) packaging structure and a COF packaging method. The COF packaging structure includes a flexible substrate and a chip. The flexible substrate includes a first groove provided on a first surface of the flexible substrate, a protrusion provided in the first groove, and a substrate bonding pad disposed in the first groove. The chip includes a second groove provided on a second surface of the chip, and a chip bonding pad disposed on the second surface and corresponding to the substrate bonding pad. The first groove of the flexible substrate is matched with a peripheral shape of the chip, and the second groove is matched with the protrusion of the first groove to embed the chip in the flexible substrate. The chip bonding pad is electrically connected to the substrate bonding pad.