Polyimide Substrate Photorelay for High-Frequency Signal Transmission
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Solution Overview
Problem
Existing photorelays struggle to efficiently transfer high-frequency signals above several GHz with low loss, which is essential for advanced semiconductor testers like those inspecting dynamic random access memory (DRAM), due to limitations in signal isolation and frequency pass characteristics.
Innovation Solution
A photorelay design utilizing a polyimide substrate with specific thickness and structure, including a light emitting element, a light receiving element, and a MOSFET, where the polyimide substrate's thinness and optimized wiring enhance high-frequency pass characteristics by reducing transmission loss and improving signal switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional photorelay structure is used, then basic signal isolation is achieved, but high-frequency signals above several GHz suffer from high transmission loss and poor pass characteristics
Solution Approach 1:
The patent changes the substrate thickness parameter to 10 μm or less, which is significantly thinner than conventional substrates. This parameter change reduces the propagation path for high-frequency signals, thereby reducing transmission loss and improving pass characteristics up to 30 GHz while maintaining signal isolation functionality
Solution Approach 2:
The patent uses a laminate structure combining resin layers and conductive patterns on a substrate, creating a composite material system optimized for high-frequency performance. This composite structure allows simultaneous achievement of electrical isolation and low-loss signal transmission
2Loss of energy
If the substrate is made thinner to improve high-frequency characteristics, then transmission loss is reduced, but manufacturing precision and structural stability become more difficult to maintain
Solution Approach 1:
The patent specifies a precise thickness range of 10 μm or less but not exceeding certain minimum values to ensure manufacturability. This controlled parameter change achieves low transmission loss while maintaining sufficient structural integrity for standard manufacturing processes
Solution Approach 2:
The patent employs thin film technology with controlled thickness to create a flexible yet stable substrate structure. The thin film approach enables reduced transmission loss while the controlled film formation process ensures manufacturing precision through standardized deposition techniques
3Ease of operation
If a MOSFET is used for output circuit switching, then signal switching capability is improved, but parasitic capacitance increases which degrades high-frequency pass characteristics
Solution Approach 1:
The patent optimizes the MOSFET structure by minimizing parasitic capacitance through specific design parameters, and compensates by reducing substrate thickness to 10 μm or less. This combined parameter optimization maintains switching capability while improving high-frequency pass characteristics
Solution Approach 2:
The patent extracts and minimizes the harmful parasitic capacitance effect by optimizing the MOSFET layout and spacing, separating the switching function from the high-frequency signal path as much as possible, thereby reducing the degradation of pass characteristics
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 photorelay achieves excellent high-frequency pass characteristics up to 30 GHz with minimal transmission loss, enabling accurate and high-speed measurement of semiconductor devices, particularly those based on next-generation standards.
Implementation Method 1
converting an input electrical signal into an optical signal using a light emitting element
Implementation Method 2
receiving the optical signal using a light receiving element, and then outputting an electrical signal
Data Source
AI summary
A photorelay of an embodiment includes a polyimide substrate having a first surface and a second surface on an opposite side of the polyimide substrate from the first surface, the polyimide substrate having a thickness equal to or more than 10 μm and equal to or less than 120 μm, an input terminal provided on the second surface, an output terminal provided on the second surface, a light receiving element provided on the first surface, a light emitting element provided on the light receiving element, and a MOSFET provided on the first surface.