COF Bump Trench Structure for Fine-Pitch Bonding Reliability
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Solution Overview
Problem
The reliability of electrical connections between the bump structure and leads in chip on film (COF) packages is compromised due to the slip phenomenon during thermal compression bonding, especially when leads are arranged at a fine pitch, leading to reduced connection reliability in miniaturized display devices.
Innovation Solution
The design incorporates a bump structure with a trench that accommodates a portion of the conductive pad, featuring first and second peripheral walls that define the trench, ensuring the conductive pad is spaced apart from these walls, thereby limiting the sliding range during thermal compression bonding and enhancing the connection reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If leads are arranged at a fine pitch to miniaturize the display device, then the device size is reduced, but the reliability of electrical connection between the bump structure and leads deteriorates due to the slip phenomenon during thermal compression bonding
Solution Approach 1:
The conductive pad is segmented into multiple portions by the trench structure, creating distinct regions that prevent continuous sliding. The trench divides the conductive pad into separate segments that can accommodate thermal expansion and compression without causing the bump structure to slip, thereby maintaining electrical connection reliability in miniaturized devices with fine-pitch leads
Solution Approach 2:
The trench structure creates a nested configuration where portions of the conductive pad are positioned within the trench region. This nested arrangement allows the conductive pad to be partially embedded in the trench, providing mechanical constraint that prevents slip during thermal compression bonding while maintaining the compact fine-pitch lead arrangement
2Area of stationary object
If the conductive pad is extended to accommodate fine-pitch leads, then the electrical connection area is increased, but the slip phenomenon during thermal compression bonding becomes more pronounced, reducing connection reliability
Solution Approach 1:
The extended conductive pad is divided into multiple portions by the trench, creating segmented regions that prevent continuous sliding motion. This segmentation allows the conductive pad to maintain its extended area for accommodating fine-pitch leads while preventing the slip phenomenon that would otherwise occur during thermal compression bonding
Solution Approach 2:
The trench acts as an intermediary structure between the bump structure and the conductive pad. It provides a mechanical barrier that prevents direct sliding contact, thereby mediating the interaction between these components during thermal compression bonding and preventing slip while maintaining electrical connection
Data Source
AI summary
A chip on film package is provided. The chip on film package includes a film substrate with a base film, a conductive pad extending in a first direction on the base film, and a conductive line pattern extending from the conductive pad; a semiconductor chip provided on the film substrate; and a bump structure provided between the semiconductor chip and the conductive pad. A first peripheral wall and a second peripheral wall of the bump structure extend in the first direction and define a trench, a portion of the conductive pad is provided in the trench, and the conductive pad is spaced apart from at least one of the first peripheral wall and the second peripheral wall.