Magnetic Sensor Stress Absorption Grooves Offset Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic sensors face variations in offset voltage due to residual stress in the protective film, which affects the detection accuracy and stability of the magnetic field measurements.
Innovation Solution
The method involves forming stress absorption grooves in the protective film near the magnetic detection elements, followed by annealing the multilayer substrate to reduce residual stress, and then performing laser trimming and packaging to maintain the offset voltage close to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the protective film is formed by CVD to protect the magnetic resistors, then the reliability of the magnetic sensor is improved, but the residual stress in the protective film causes variations in offset voltage
Solution Approach 1:
The protective film is segmented by forming stress absorption grooves that divide the film into separate regions. This segmentation allows the residual stress to be localized and absorbed at the groove interfaces, preventing uniform stress distribution that would otherwise cause offset voltage variations across the magnetic resistors.
Solution Approach 2:
The stress absorption grooves are formed in advance before the magnetic resistors are subjected to subsequent processing steps. This preliminary action ensures that the protective film's stress is pre-managed and absorbed, preventing future stress-induced variations in offset voltage during operation or subsequent manufacturing steps.
2Manufacturing precision
If laser trimming is performed to adjust the resistance of magnetic resistors, then the manufacturing precision of offset voltage is improved, but the heat generated during trimming causes variations in offset voltage
Solution Approach 1:
The stress absorption grooves are formed before the laser trimming process. This preliminary structure is in place to absorb any stress that may develop during the trimming operation, allowing the laser trimming to be performed effectively without causing subsequent offset voltage variations due to stress.
Solution Approach 2:
The stress absorption grooves act as an intermediary structure between the protective film and the magnetic resistors. During laser trimming, the grooves serve as a stress buffer that mediates the thermal and mechanical stress, preventing direct stress transmission to the magnetic resistors that would otherwise cause offset voltage variations.
3Reliability
If packaging is performed with heated resin to solidify and protect the sensor, then the reliability of the magnetic sensor is improved, but the heat applied during packaging causes variations in offset voltage
Solution Approach 1:
The stress absorption grooves are formed in advance of the packaging process. This ensures that when heated resin is applied during packaging, the pre-existing groove structure is already in place to absorb and manage the thermal stress, preventing offset voltage variations that would otherwise result from the packaging heat.
Solution Approach 2:
The stress absorption grooves convert the harmful thermal stress from the packaging process into a beneficial stress distribution pattern. The grooves provide designated stress concentration zones that safely accommodate the thermal expansion and contraction forces, transforming what would be harmful uniform stress into controlled, localized stress that does not affect the magnetic resistors.
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 approach significantly reduces variations in the offset voltage, enhancing the detection accuracy and stability of the magnetic sensor by minimizing the impact of heat on the magnetic resistors during packaging and trimming.
Implementation Method 1
The protective film 87, when formed, may receive strain that remains as residual stress. The residual stress may change the resistances of the magnetic resistors 81 to 84 and cause variations in the offset voltage. The inventor of the present invention has proposed the formation of the stress absorption groove 88 subsequent to the formation of the protective film 87 to absorb the residual stress of the protective film 87 with the groove 88
Implementation Method 2
annealing the multilayer substrate prior to the packaging
Implementation Method 3
performing laser trimming and packaging to maintain the offset voltage close to zero
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A method for manufacturing a magnetic sensor. The method includes forming a plurality of magnetic detection elements (10, 20, 30, 40) on a substrate (2) to form a bridge circuit, forming a protective film (6) that protects the magnetic detection elements on the substrate, forming a plurality of stress absorption grooves (7) near each of the magnetic detection elements by etching the protective film to produce a multilayer substrate (11) including the protective film, the stress absorption grooves, and the magnetic detection elements, packaging the multilayer substrate, and annealing the multilayer substrate prior to the packaging,