Sensor Module Encapsulation for Transmission Oil Resistance
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Solution Overview
Problem
Position sensors in harsh environments, such as automatic transmissions, face challenges with media resistance and thermal stability due to exposure to aggressive media like transmission oil and varying temperatures, leading to potential corrosion and mechanical damage.
Innovation Solution
A method for producing a sensor module with a media-resistant encapsulation using an epoxy resin compound and an adhesion-promoting surface on the stamped grid and circuit carrier, which includes a transfer molding process to ensure thermal and mechanical stability, and minimizes the use of solder resist for improved adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the printed circuit board is cast in a thermoplastic housing and filled with epoxy resin, then the sensor module is protected and mechanically stable, but the high coefficient of expansion of the epoxy resin leads to accelerated disruption of soldering points and delamination with temperature changes
Solution Approach 1:
The patent applies parameter changes by selecting an epoxy resin compound with specific properties: a lower coefficient of thermal expansion and a glass transition temperature of at least 140°C. These parameter modifications resolve the contradiction by reducing thermal expansion stress on soldering points while maintaining mechanical stability through the enhanced thermal properties of the resin compound.
Solution Approach 2:
The patent uses composite materials by combining the printed circuit board, epoxy resin compound, and adhesion-promoting surfaces (such as Ni/Pd/Au layers) into an integrated structure. This composite approach allows the system to benefit from the mechanical stability of the epoxy resin while the adhesion-promoting surfaces and circuit board materials compensate for thermal expansion differences, preventing delamination and soldering point disruption.
2Adaptability or versatility
If the sensor module is exposed to aggressive media like transmission oil, then the sensor can detect positions in transmission controls, but the media can penetrate the housing and cause corrosion of conductor tracks and bonding wires
Solution Approach 1:
The patent applies this principle by using a thermoplastic housing that completely encloses the printed circuit board and sensor elements, creating a flexible yet protective barrier. The housing acts as a first line of defense against aggressive media like transmission oil, preventing direct contact with conductor tracks and bonding wires while allowing the sensor to function in the required environmental conditions.
Solution Approach 2:
The patent employs composite materials by combining the thermoplastic housing with epoxy resin compound filling and adhesion-promoting surface layers. This multi-layer composite structure provides enhanced media resistance: the housing prevents media penetration, the epoxy resin seals gaps and provides additional protection, and the adhesion-promoting surfaces prevent corrosion at critical interfaces, collectively resolving the media resistance issue.
3Object-affected harmful factors
If solder resist is used to protect soldering points, then corrosion protection is provided, but adhesion between the encapsulation and the circuit carrier is reduced
Solution Approach 1:
The patent applies the extraction principle by completely removing or minimizing the use of solder resist from the circuit carrier surface. Instead of relying on solder resist for corrosion protection, the patent uses the epoxy resin compound to encapsulate and protect soldering points, thereby eliminating the adhesion problem caused by solder resist while maintaining corrosion protection through the encapsulation approach.
Solution Approach 2:
The patent uses the epoxy resin compound as an intermediary that performs both protection and adhesion functions. Rather than using solder resist as a protective layer that interferes with adhesion, the epoxy resin acts as a mediator that seals and protects soldering points from corrosion while simultaneously providing strong adhesion to the circuit carrier and other components, resolving the contradiction between protection and adhesion.
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 solution enhances the media resistance and thermal stability of the sensor module, preventing corrosion and mechanical damage, while allowing for a smaller external geometry and improved reliability under temperature changes.
Implementation Method 1
an adhesion-promoting surface on the stamped grid and circuit carrier, which includes a transfer molding process to ensure thermal and mechanical stability
Data Source
Figure 1~2
Figure 3A~3C
Figure 4~5
AI summary
The method involves attaching a sensor element (116) on a circuit carrier (118). A punched grid (120) is electro-conductively connected with the circuit carrier, where the punched grid and/or the circuit carrier has an adhesion supporting surface. The punched grid and the circuit carrier are partially covered with a media-tight insulator casing (144), which consists of epoxy resin compound. A soldered joint i.e. contact pad, is formed on the circuit carrier. A solder mask is attached around the soldered joint as a frame. An independent claim is also included for a switching element of a gearbox controller of a motor vehicle.