Wiring Substrate Terminal Layout for Thermal Stress Isolation
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Solution Overview
Problem
The existing wiring substrates for liquid crystal panels face issues with electrical defects due to thermal expansion and contraction, leading to potential short-circuits between terminals, especially when lead-out wiring is not present between adjacent external connection terminals, causing stress and peeling, which can result in short-circuits and electrical defects.
Innovation Solution
A wiring substrate design with specific terminal arrangements and wiring configurations, including the placement of dummy terminals and connection wirings, where the interval between certain terminals is longer than the wiring intervals, and potential is not supplied to certain terminals, to mitigate thermal stress and prevent short-circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If external connection terminals are arranged with long intervals without lead-out wiring between them, then the mounting area for scanning signal drive circuit is increased, but thermal expansion and contraction cause large stress leading to peeling and short-circuits
Solution Approach 1:
A dummy terminal is introduced as an intermediary element between the first terminal and the third terminal. This dummy terminal serves as a stress buffer that absorbs thermal expansion and contraction forces, preventing direct stress transmission between the functional terminals. The dummy terminal is electrically isolated (not connected to lead-out wiring) to maintain electrical reliability while providing mechanical compliance during thermal cycling.
Solution Approach 2:
The long interval between external connection terminals is segmented by inserting a dummy terminal in between. This divides the continuous insulating portion into separate segments, each with reduced length. The segmentation reduces the cumulative thermal stress in any single insulating portion, preventing peeling and maintaining electrical isolation between terminals.
2Reliability
If insulating portion is formed on upper layer side of external connection terminals, then terminal isolation is achieved, but stress from thermal expansion causes peeling and short-circuits
Solution Approach 1:
The dummy terminal is positioned beforehand in the interval between external connection terminals to provide cushioning against thermal stress. By pre-positioning this stress-absorbing element, the insulating film is protected from excessive stress during subsequent thermal cycling, preventing peeling and maintaining both terminal isolation and adhesion strength.
3Reliability
If interval between third terminal and first terminal is made longer than wiring intervals, then thermal stress is reduced, but device complexity increases
Solution Approach 1:
The dummy terminal is a simplified copy of the terminal structure that does not require full electrical functionality. It replicates the basic terminal form factor and positioning but omits lead-out wiring connections, providing stress buffering without the complexity of full electrical interconnection. This copying approach reduces short-circuit risk while minimizing added complexity.
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
This design effectively reduces the likelihood of short-circuits and electrical defects by managing thermal stress and ensuring that terminals are not short-circuited, even under temperature fluctuations, thereby enhancing the reliability and durability of the liquid crystal display devices.
Implementation Method 1
an insulating portion disposed on an upper layer side of the first terminal, the second terminal, the third terminal, the first wiring, and the second wiring
Implementation Method 2
When the TFT array substrate is heated during mounting of the scanning signal drive circuit, thermal expansion and thermal contraction occur in the insulating portion
Implementation Method 3
When the TFT array substrate is heated during mounting of the scanning signal drive circuit, thermal expansion and thermal contraction occur in the insulating portion
Data Source
AI summary
A wiring substrate includes a first terminal, a second terminal disposed side by side at intervals from the first terminal in a first direction, a third terminal disposed side by side at intervals from the first terminal in the first direction on a side opposite to the second terminal, a first wiring positioned between the first terminal and the second terminal, a second wiring connected to the first terminal and the third terminal, and an insulating portion disposed on an upper layer side of the first terminal, the second terminal, the third terminal, the first wiring, and the second wiring, in which the third terminal is disposed at a position where an interval between the third terminal and the first terminal is longer than any of an interval between the first wiring and the first terminal, and an interval between the first wiring and the second terminal.