Circuit Board Test Auxiliary Structure for Accurate Impedance Measurement
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Solution Overview
Problem
The existing methods for testing bonding impedance of flexible circuit boards in display devices are inaccurate due to the risk of probes piercing through both the test pads and the base substrate, causing electrical connection with metal layers and affecting the measurement results.
Innovation Solution
A circuit board design featuring test auxiliary structures on the second surface, insulated from the metal layer, which overlap with test pads to prevent electrical interference during impedance testing, ensuring accurate measurement by isolating the probe contact from the metal structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a probe is used to penetrate the test point for bonding impedance testing, then the test can be performed, but the probe may penetrate through the test point and electrically connect to other charged film layers, affecting measurement accuracy
Solution Approach 1:
An insulating layer is introduced as an intermediary between the metal layer and the test auxiliary structure. This insulating layer prevents direct electrical contact between the probe and the metal layer when the probe penetrates through the test pad, thereby eliminating the harmful electrical interference while allowing the measurement to proceed
Solution Approach 2:
The structure is segmented into distinct functional layers: the metal layer for signal transmission, the insulating layer for electrical isolation, and the test auxiliary structure for measurement. This segmentation allows the probe to interact with the test auxiliary structure without directly contacting the metal layer, preventing electrical interference
2Reliability
If the test auxiliary structure overlaps with the test pads, then probe penetration through the base substrate can be prevented, but the test auxiliary structure must be insulated from the metal structure to avoid interference
Solution Approach 1:
The test auxiliary structure is merged with the existing metal layer structure by forming it on the same base substrate. The test auxiliary structure utilizes the same fabrication processes and materials as the metal layer, integrating seamlessly into the existing circuit board design without adding significant structural complexity
Solution Approach 2:
An insulating layer is positioned between the test auxiliary structure and the metal layer to provide electrical isolation. This insulating layer is integrated into the existing multi-layer structure of the circuit board, maintaining the overlapping configuration while preventing electrical interference
Data Source
AI summary
A circuit board, a display module, and a display device are provided. The circuit board includes: a base substrate including a first surface and a second surface opposite to each other; bonding pads on the first surface; test pads electrically connected to the bonding pads and disposed on the second surface; a test auxiliary structure on the second surface; and a metal layer on the second surface. The test auxiliary structure overlaps with the test pads along a first direction which is a direction perpendicular to the first surface and the second surface of the base substrate; and the metal layer includes a metal structure for transmitting a first signal and the test auxiliary structure is insulated from the metal structure.