Sensor Substrate Backside Interconnection via Recess Filling
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Solution Overview
Problem
Conventional sensor unit assembly processes are complex and prone to mechanical stress, which can damage the sensor substrate, especially in aggressive and humid environments, and require efficient assembly procedures for high-volume production.
Innovation Solution
The solution involves providing openings in the sensor substrate for applying electrically conductive material from the backside with the circuit carrier as a mechanical support, using metallized vias and capillary effects to facilitate electrical connections between contact pads, and employing reflow soldering for reliable solder connections, allowing for panel-level processing and reduced material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional assembly processes are used to attach the sensor substrate to the circuit carrier, then electrical connections can be established, but the sensor substrate is exposed to mechanical stress that can damage it
Solution Approach 1:
The patent inverts the conventional assembly sequence by first attaching the circuit carrier to the sensor substrate, then filling conductive material into openings from the backside of the sensor substrate. This reversal protects the fragile sensor substrate from mechanical stress during the assembly process, as the circuit carrier serves as a support structure and the conductive material is deposited without direct handling of the sensor substrate.
2Volume of moving object
If the sensor substrate is made thin to reduce size, then the sensor unit becomes more compact, but the substrate becomes more vulnerable to mechanical damage
Solution Approach 1:
The patent provides beforehand cushioning by attaching the circuit carrier to the thin sensor substrate before the assembly process. The circuit carrier acts as a protective support structure that compensates for the reduced mechanical strength of the thin sensor substrate, allowing it to withstand handling and assembly operations without damage.
3Reliability
If complex fabrication processes are used to establish electrical connections, then reliable connections can be achieved, but the manufacturing complexity increases
Solution Approach 1:
The patent extracts the electrical connection process from the frontside of the sensor substrate and relocates it to the backside. By filling conductive material into openings from the backside, the complex metallization and connection processes are separated from the sensitive sensor elements, simplifying the overall fabrication process while maintaining connection reliability.
4Adaptability or versatility
If the sensor substrate is exposed to aggressive and humid environments, then the transducer elements can monitor measurands, but the electronic components are damaged or impaired
Solution Approach 1:
The patent segments the sensor assembly into distinct functional zones: the sensor substrate with transducer elements that are exposed to the aggressive environment for monitoring, and the circuit carrier with electronic components that are protected from direct environmental exposure. This segmentation allows the transducer elements to access measurands while the electronic components remain shielded.
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 method enhances the reliability and efficiency of sensor unit assembly, protects the transducer elements from aggressive media, and simplifies the manufacturing process, reducing the risk of mechanical stress and improving the overall performance of the sensor arrangement.
Implementation Method 1
If the gap filling is effected by capillary effects, and the openings are formed by metallized vias, this electrically conductive glue is not mandatory.
Implementation Method 2
employing reflow soldering for reliable solder connections
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
The present invention relates to a sensor unit and to a corresponding method of assembling such a sensor unit. The sensor unit comprises at least one transducer element (102, 202) for monitoring at least one measurand and generating an electrical output signal correlated with the at least one measurand, and a sensor substrate (104, 204) with a first surface (108, 208) and an opposing second surface (110, 210), said sensor substrate (104, 204) comprising said transducer element (102, 202) and at least one first electrically conductive contact pad (114, 214) arranged on the first surface of the sensor substrate, wherein said first electrically conductive contact pad is electrically connected to the transducer element. A recess (116, 216) is provided in the sensor substrate, the recess extending from the second surface (110, 210) to the first surface (108, 208), wherein said sensor substrate is mounted on a circuit carrier (106, 206) in a way that the first surface faces the circuit carrier. The circuit carrier comprises at least one second electrically conductive pad (118, 218), wherein the first electrically conductive contact pad and the second electrically conductive contact pad are interconnected by an electrically conductive material (124, 224; 126; 226) that is filled in from the second surface towards the first surface of the sensor substrate.