Stepped Pad Structure for Display Circuit Board Alignment
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Solution Overview
Problem
In display apparatuses, ensuring proper alignment between the pads of a printed circuit board (PCB) and a test circuit board is crucial for accurate testing, as insufficient contact margin can lead to false detections due to minor alignment errors.
Innovation Solution
The display apparatus includes a substrate with a display area and a display circuit board outside the display area, featuring first and second pads with an insulating layer in between. The pads are designed such that the first pad overlaps the second pad, and the thickness of at least a portion of the second pad differs from that of the first pad, with the insulating layer providing additional separation and contact margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pads of the PCB and test circuit board are aligned with minimal separation distance, then the contact margin is reduced and testing becomes more sensitive to alignment errors, but the device complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent introduces a vertical dimension by creating a stepped pad structure where the first pad and second pad have different thicknesses. This three-dimensional configuration allows the pads to overlap in the vertical direction while maintaining horizontal separation, effectively adding a Z-axis dimension to the traditionally two-dimensional pad layout. This resolves the contradiction by enabling sufficient contact margin in the horizontal plane while achieving electrical contact through vertical overlap.
Solution Approach 2:
The patent implements a nested structure where the projection of the first pad and second pad overlap in the horizontal plane, with one pad being partially positioned within the horizontal footprint of the other. This nesting arrangement allows the pads to share common horizontal space while maintaining electrical isolation through the insulating layer, effectively reducing the required contact margin and relaxing alignment precision requirements.
2Reliability
If a sufficient contact margin is provided between pads, then false detections are prevented and testing reliability improves, but the device complexity increases due to the insulating layer and varied pad thicknesses
Solution Approach 1:
The patent introduces an insulating layer as an intermediary element positioned between the first pad and second pad. This insulating layer acts as a mediator that provides electrical isolation while allowing the pads to be in close proximity or overlap. The insulating layer enables sufficient contact margin to be maintained without requiring complex mechanical structures, thereby improving testing reliability while keeping the overall device complexity manageable through a simple additive layer.
Solution Approach 2:
The patent applies local quality by varying the thickness of pads in specific locations rather than making all pads uniform. The first pad and second pad have different thicknesses at different positions, creating localized variations that enable the stepped configuration. This local differentiation allows the structure to achieve both electrical contact and insulation requirements without globally increasing device complexity.
3Adaptability or versatility
If the pads are made with different thicknesses to create overlap, then the contact margin is improved and alignment tolerance increases, but the manufacturing precision requirements for pad thickness control increase
Solution Approach 1:
The patent implements preliminary action by pre-forming the insulating layer between the pads before finalizing the pad structures. This sequence ensures that the insulating layer is already in place to provide the necessary electrical isolation and contact margin before the pads are formed with their final thickness variations. This preliminary preparation simplifies subsequent manufacturing steps and reduces the precision requirements for pad thickness control, as the insulating layer already establishes the electrical boundaries.
Data Source
AI summary
A display apparatus includes a substrate including a display area where a plurality of display elements are disposed, and a display circuit board disposed outside the display area. The display circuit board includes a first pad and a second pad, which are disposed on the display circuit board and connected to the substrate, and an insulating layer disposed between the first pad and the second pad, and the first pad overlaps the second pad and a thickness of at least a portion of the second pad is different from a thickness of the first pad.