Driving Chip Bump Layout for Uniform Stress Distribution
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Solution Overview
Problem
In chip on glass (COG) technology, the use of anisotropic conductive film (ACF) is costly, and non-conductive film (NCF) often results in poor electronic connections and bad indentations in the bumps of the driving chip, leading to unstable display images due to inadequate gap filling between bumps and metal traces.
Innovation Solution
A bump layout for the driving chip with a ratio of total contacting areas of first bumps to second bumps between 0.8 and 1.2, and a ratio of each second contacting area to each first contacting area between 0.25 and 0.5, ensuring even stress distribution and reliable connection, allowing for the use of non-conductive film without anisotropic conductive film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If non-conductive film (NCF) is used to connect the driving chip and glass substrate, then cost is reduced compared to ACF, but bad indentations occur in the bumps leading to poor electronic connection
Solution Approach 1:
The patent applies local quality by creating different bump types with different contacting areas. First bumps have a first contacting area and second bumps have a second contacting area, where the ratio between them is controlled within 0.25-0.5. This local differentiation in bump geometry allows the NCF to properly fill gaps between bumps and metal traces, ensuring good electrical connection while maintaining cost-effectiveness.
Solution Approach 2:
The patent changes the geometric parameters of the bumps by controlling the ratio of contacting areas between different bump types. By specifying that the ratio of each second contacting area to each first contacting area is between 0.25 and 0.5, and the ratio of total second contacting areas to total first contacting areas is between 0.8 and 1.2, the invention optimizes the gap-filling capability of NCF, thereby improving connection reliability without using expensive ACF.
2Reliability
If ACF is used to connect the driving chip and glass substrate, then reliable electrical connection is achieved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces the expensive ACF with the cheaper NCF by designing a specific bump layout. The controlled ratio of contacting areas between different bump types enables the low-cost NCF to achieve the gap-filling function that would otherwise require expensive conductive particles in ACF, thus substituting a costly material with a more economical alternative.
Solution Approach 2:
By creating local variations in bump contacting areas, the patent enables NCF to effectively fill gaps in critical regions. The different bump sizes create varied gap patterns that allow NCF to achieve reliable electrical connection without requiring the expensive conductive properties of ACF throughout the entire connection interface.
3Ease of manufacture
If uniform bump layout is used, then manufacturing is simplified, but stress distribution becomes uneven causing poor contacts
Solution Approach 1:
The patent deliberately introduces asymmetry in the bump layout by creating two types of bumps with different contacting areas. The ratio control between first and second bumps creates an asymmetric pattern that optimizes stress distribution across the connection interface, preventing the uniform stress concentration problems that would occur with identical bumps arranged in a simple uniform pattern.
Data Source
AI summary
A chip having a bump layout suitable for the chip on glass technology and a driving IC includes a plurality of first bumps and a plurality of second bumps for electrically connecting to a glass substrate of a displayer. The first and second bumps are disposed on a surface of the chip and near two opposite long sides of the chip respectively. The ratio of the total contacting area of the first bumps to that of the second bumps is between 0.8 and 1.2. Thus, a pressure applied on the chip and the glass substrate of the displayer for connection can be uniformly exerted all over the chip, and the stability of the connection is therefore improved.