Tape Carrier Package Pad Width Variation for LCD Alignment
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Solution Overview
Problem
The existing tape carrier package (TCP) methods for liquid crystal display (LCD) devices face misalignment issues due to the difference in pad spacing between the output pads on the TCP and the input pads on the lower substrate, leading to electrical shorts and defects in display quality.
Innovation Solution
A TCP design with output pad groups having varying widths and pitches from the center to the edge of the base film, matching the expansion rate of the base film to minimize misalignment, and an LCD device with corresponding input pad groups on the liquid crystal panel, ensuring proper alignment and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output pad portion of the TCP is one-to-one connected to the input pad portion of the lower substrate, then the connection between TCP and lower substrate is established, but misalignment occurs between output pads and input pads from center portion toward edge of the base film, generating defects such as electrical shorts
Solution Approach 1:
The patent applies local quality by dividing the output pad portion into multiple output blocks with different pad widths at different locations. Specifically, the first output block has a first pad width, the second output block has a second pad width, and the third output block has a third pad width, creating spatially varying pad dimensions to compensate for base film expansion differences across the TCP structure.
Solution Approach 2:
The patent changes the pad width parameter across different output blocks to match the expansion characteristics of the base film at different locations. The pad widths are specifically designed as different values (first width, second width, third width) corresponding to different regions, thereby maintaining proper alignment despite base film expansion during bonding.
2Ease of manufacture
If the base film is bonded to the lower substrate using OLB process with temperature and pressure, then the TCP is attached to the lower substrate, but the shape of the film transforms causing spaces of output pads to differ from spaces of input pads
Solution Approach 1:
The patent applies preliminary action by pre-designing the output pad portions with different pad widths in different output blocks before bonding, anticipating the shape transformation that will occur during the OLB bonding process. This preliminary configuration ensures that even after thermal and mechanical stress during bonding, the pads will maintain proper alignment with the lower substrate input pads.
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 design improves image quality uniformity and long-term reliability by accommodating the expansion of the base film during bonding, reducing misalignment and connection defects between the TCP and the liquid crystal panel.
Implementation Method 1
the base film expands more than the lower substrate by heat or pressure
Data Source
AI summary
A tape carrier package (TCP) includes a base film, an integrated circuit (IC) chip and an output pad group. The IC chip is formed on the base film. The output pad group is formed on a first end of the base film. The output pad group includes a plurality of output blocks having a plurality of output pads, wherein the plurality of output pads in an output block have substantially the same width as each other. The widths of the output pads from one output block to another output block are different from each other.