Photodiode Detection Layout to Prevent Wiring Cracks Under Bending
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Solution Overview
Problem
Optical sensors with organic semiconductor materials experience stress concentration and wiring cracks at the step between the sensor substrate and the protective layer due to the protective layer having a smaller area than the sensor substrate, leading to potential damage when the housing is bent.
Innovation Solution
A detection device design that includes a first substrate with a smaller area second substrate covering the photodiode, insulating layers, and a sealing film, with a boundary line intersecting the wiring lines to distribute stress and reduce cracks, and a flexible printed circuit board coupled to a coupling area with a protective film covering the second substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a protective layer with smaller area than the sensor substrate is provided, then the device structure is simplified and manufacturing is easier, but stress concentration occurs on wiring at the step when the housing is bent
Solution Approach 1:
The peripheral area is divided into a first portion with the protective layer and a second portion without the protective layer. This segmentation allows the wiring to be routed through the second portion where it avoids the step structure, preventing stress concentration while maintaining the simplified overall device structure.
Solution Approach 2:
The insulating layer acts as an intermediary by providing a dedicated pathway for the wiring in the second portion of the peripheral area. This allows the wiring to be isolated from the step structure and protected from stress concentration while still maintaining the protective layer's coverage in the first portion.
2Reliability
If the protective layer covers the entire sensor substrate, then stress distribution is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The protective layer is selectively provided only in the first portion of the peripheral area rather than covering the entire sensor substrate. This local quality approach maintains stress distribution benefits where needed while avoiding unnecessary complexity in areas where the wiring is routed through the second portion.
3Ease of operation
If wiring lines are routed through the peripheral area with protective layer, then electrical connection is established, but wiring cracks occur due to stress concentration at the step
Solution Approach 1:
The wiring is routed through the second portion of the peripheral area in a different spatial configuration, utilizing the space created by removing the protective layer in that specific area. This dimensional approach allows the wiring to bypass the step structure and avoid stress concentration points.
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 effectively reduces stress concentration on wiring lines, minimizing cracks and ensuring durability of the optical sensors even when the device is bent, thereby enhancing the reliability and longevity of the detection device.
Implementation Method 1
a photodiode including a lower electrode, a lower buffer layer, an active layer, an upper buffer layer, and an upper electrode
Data Source
AI summary
A detection device includes: an active area including an active layer of a photodiode; a coupling area provided with a coupling part at an end of a first substrate; a peripheral area between the active area and the coupling area; a sealing film sealing the active area and the peripheral area; and a first wiring line that couples a lower electrode to the coupling part. The peripheral area includes: a first portion that includes a first insulating layer, the sealing film, a second insulating layer, and a second substrate on the first substrate; and a second portion in which at least one of the sealing film, the second insulating layer, and the second substrate is removed compared with the first portion. A boundary line between the first and second portions extends along a direction from the coupling area toward the active area and intersects the first wiring line.