Two Component Photodiode Detector X-Ray Shielding
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Solution Overview
Problem
The complexity and cost associated with manufacturing X-ray detector arrays increase with the number of photodiodes due to the need for numerous electrical connections, which complicates the substrate design and manufacturing process, making it labor-intensive and expensive.
Innovation Solution
A two-component 2-D photodiode detector array configuration where a photodiode array is bonded to one substrate and a processing chip is flip chip bonded to another, with a radiation shield positioned to prevent X-ray radiation from reaching the processing chip, creating a thermally and electrically isolated air space between the shield and the chip, and using BGA bonding to connect the substrates, reducing the number of layers and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding technique is used to connect photodiodes to processing circuitry, then electrical connections can be established, but the substrate complexity and manufacturing cost increase with the number of photodiodes
Solution Approach 1:
The detector array is divided into multiple detector modules, where each module contains a subset of photodiodes connected to processing circuitry. This segmentation reduces the number of electrical connections required per substrate, thereby reducing substrate complexity and manufacturing cost while maintaining reliable electrical connections within each module.
2Productivity
If multiple substrate layers are used to accommodate numerous circuit paths, then electrical signal transmission is enabled, but manufacturing complexity and cost increase
Solution Approach 1:
The detector array is segmented into multiple independent detector modules. Each module requires fewer substrate layers to accommodate its circuit paths, simplifying the manufacturing process. The segmentation allows for standardized module production that can be assembled into larger arrays, improving manufacturing ease while maintaining signal transmission capability.
3Speed
If processing circuitry is placed close to photodiodes, then signal transmission efficiency improves, but radiation shielding becomes more difficult
Solution Approach 1:
Each detector module is designed as a self-contained unit with photodiodes and processing circuitry integrated within the same module. Radiation shielding is implemented at the module level, allowing the circuitry to be positioned close to photodiodes for efficient signal transmission while maintaining effective radiation protection within each isolated module.
4Quantity of substance
If wire bond density is increased to connect more photodiodes, then array capacity increases, but manufacturing labor intensity increases
Solution Approach 1:
The large array is divided into multiple smaller detector modules. Each module has a manageable wire bond density that can be manufactured with standard processes. The modular approach allows parallel manufacturing of multiple modules, reducing overall labor intensity compared to manufacturing a single large-scale integrated array with high wire bond density.
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 configuration simplifies the structure, reduces manufacturing costs, enhances durability and reliability, and minimizes thermal gradient issues, while maintaining effective signal transmission and radiation protection.
Implementation Method 1
Each active photodiode array comprises a series of scintillation crystals arranged on a substrate for converting X-ray radiation into light
Implementation Method 2
Under each scintillator crystal is a back-illuminated photodiode that converts the light emitted from the scintillation crystals into an electrical charge
Implementation Method 3
Interposed between the substrate 150 and the processing circuitry 160 is a radiation shield 145. The shield 145 protects the processing circuitry from stray radiation
Data Source
AI summary
A photodiode detector array is bonded to a first surface of a first substrate and electrically coupled to the second surface of the first substrate. A shield, opaque to X-ray radiation is attached to the second surface of the first substrate. A processing chip is flip chip bonded and electrically coupled to the first surface of the second substrate. A portion of the first surface of the second substrate is physically and electrically joined to a portion of the second surface of the first substrate so as to allow processing of electrical signals from the photodiode array. The shield associated with the first substrate is aligned so as to prevent X-ray radiation from reaching the processing chip associated with second substrate. The shield and the processing chip are separated by an air space providing thermal and electrical isolation.