Four-Side Buttable Radiation Detector Unit for Gapless CT Arrays
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Solution Overview
Problem
Current radiation detector arrays in CT imaging systems face challenges in providing continuous detection without gaps, especially at high photon count rates, due to the design of detector units that may leave areas uncovered or with significant gaps, affecting image reconstruction quality.
Innovation Solution
The development of four-side buttable radiation detector units, detector modules, and arrays, where each unit consists of a radiation sensor bonded to an interposer, an ASIC, a carrier board, and flex cable assemblies, allowing for seamless assembly into a two-dimensional array with minimal gaps, using specific bonding techniques to avoid thermal damage to sensitive semiconductor materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional radiation detector units are used, then the detector array can be assembled, but gaps appear between detector units causing uncovered detection areas
Solution Approach 1:
The detector unit is segmented into modular components (radiation sensor, interposer, ASIC, carrier board, flex cable assembly) that can be precisely manufactured and then assembled into arrays. The radiation sensor itself is divided into multiple pixel elements arranged in a grid pattern, allowing for systematic tiling to achieve complete coverage without gaps.
Solution Approach 2:
An interposer is introduced as an intermediary component between the radiation sensor and the ASIC. This interposer provides a standardized interface that facilitates precise alignment and bonding, ensuring that multiple detector units can be assembled edge-to-edge without gaps while maintaining electrical connections.
2Strength
If high bonding temperature is used to bond ASIC to interposer, then strong bonding is achieved, but thermal damage occurs to radiation sensor
Solution Approach 1:
The bonding process is segmented into separate stages with different temperature requirements. First, the ASIC is bonded to the interposer at high temperature to achieve strong bonding. Then, the radiation sensor is bonded to the interposer at low temperature to avoid thermal damage. This temporal and thermal segmentation allows each component to be bonded under optimal conditions.
Solution Approach 2:
The ASIC is preliminarily bonded to the interposer before the radiation sensor is attached. This preliminary action allows the high-temperature bonding to be completed without the radiation sensor present, preventing thermal damage while still achieving the necessary bonding strength for the ASIC connection.
3Adaptability or versatility
If multiple components are bonded together, then functional integration is achieved, but manufacturing complexity increases
Solution Approach 1:
The detector unit is segmented into distinct functional modules (radiation sensor, interposer, ASIC, carrier board, flex cable assembly) that can be manufactured separately using standardized processes. Each module maintains well-defined interfaces that simplify assembly, reducing the overall manufacturing complexity despite the multiple components involved.
Solution Approach 2:
The interposer serves multiple functions: it provides mechanical support for both the ASIC and radiation sensor, establishes electrical connections between components, enables precise alignment through standardized interfaces, and facilitates thermal management. This multi-functionality reduces the need for additional specialized components, simplifying the overall assembly process.
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 enables continuous radiation detection over a wide area with minimal gaps, enhancing the sensitivity and reliability of X-ray detection, even at high photon count rates, and supports efficient assembly and maintenance of detector arrays.
Implementation Method 1
bonding an ASIC to a backside of an interposer at a first temperature using first bonding structures
Implementation Method 2
bonding a carrier board to the backside of the interposer at a second reflow temperature lower than the first temperature using second solder balls
Implementation Method 3
bonding at least one radiation sensor to a front side of the interposer using electrically conductive epoxy portions at a setting temperature lower than the second reflow temperature
Data Source
AI summary
A radiation detector unit includes an interposer, at least one radiation sensor bonded to a front side of an interposer, an application-specific integrated chip (ASIC) bonded to a backside of the interposer, a carrier board bonded to the backside of the interposer and located on a backside of the ASIC, and at least one flex cable assembly attached to a respective side of the carrier board.