Sensor Epoxy Resin Coating for Media Tightness
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Solution Overview
Problem
Conventional speed sensors, particularly those used in motor vehicles, face challenges with media tightness due to thermoplastic overmolding, which is insufficient against aggressive environments like transmission oil, leading to potential corrosion and short circuits under high operational loads and temperature fluctuations.
Innovation Solution
A sensor design featuring a leadframe and holder made of plastic, surrounded by a media-resistant epoxy resin casing produced through transfer molding, with an adhesive coating on the leadframe to enhance adhesion and electrical contact, and filled with thermosetting materials for improved thermomechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermoplastic overmolding is used to encapsulate sensor components, then manufacturing simplicity is improved, but media tightness deteriorates due to insufficient adhesion to leadframe and grid
Solution Approach 1:
The patent employs a composite encapsulation structure combining thermoplastic holder and epoxy resin coating. The thermoplastic provides structural support and basic protection, while the epoxy resin layer adheres to the leadframe and stamped grid to ensure media tightness. This composite approach leverages the strengths of both materials to resolve the contradiction between manufacturing simplicity and media tightness.
Solution Approach 2:
The epoxy resin acts as an intermediary material between the thermoplastic holder and the metal components (leadframe, stamped grid). It provides the necessary adhesion interface that the thermoplastic alone cannot achieve, ensuring media tightness while maintaining the overall manufacturing process efficiency.
2Ease of manufacture
If thermoplastic material is used for sensor housing, then processing ease is improved, but adhesion to metal components deteriorates leading to media penetration
Solution Approach 1:
The patent uses a composite material system where thermoplastic forms the holder structure and epoxy resin provides the adhesion layer. The epoxy resin specifically bonds to metal surfaces (leadframe, stamped grid) with high adhesion strength, compensating for the thermoplastic's insufficient bonding capability while maintaining processing ease.
Solution Approach 2:
Different regions of the sensor housing have different material properties optimized for their specific functions. The thermoplastic holder provides structural support and ease of processing, while the epoxy resin coating applied locally to metal components provides superior adhesion and media tightness where needed.
3Ease of manufacture
If simple thermoplastic encapsulation is used, then production cost is reduced, but media resistance deteriorates under aggressive operating conditions
Solution Approach 1:
The patent implements a cost-effective composite encapsulation using thermoplastic holder combined with epoxy resin coating. This combination provides enhanced media resistance against aggressive conditions (transmission oil, temperature extremes) while maintaining reasonable production costs through the use of standard materials and processes.
Solution Approach 2:
The patent changes the material parameter from pure thermoplastic to a composite system including epoxy resin. This parameter change significantly improves media resistance properties while the process remains compatible with existing manufacturing capabilities, minimizing cost increase.
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 provides a highly media-resistant and thermally stable sensor that prevents media penetration and maintains functionality across extreme temperatures, ensuring reliable operation in harsh automotive environments.
Implementation Method 1
The epoxy resin adheres to the thermoplastic and the stamped grids and thus ensures media tightness
Implementation Method 2
an adhesive coating on the leadframe to enhance adhesion
Data Source
Figure 1
Figure 2A~2D
Figure 3A~3B
AI summary
The invention relates to a method for manufacturing a sensor (110), in particular for speed detection, especially for use in a motor vehicle. In this process, at least one die-cut grid (122) is overmolded with a plastic material, forming at least one holder (116) connected to the die-cut grid (122). Furthermore, at least one sensor element (112), in particular a magnetic sensor, is electrically connected to the die-cut grid (122). The die-cut grid (122), the holder (116), and the sensor element (112) are then at least partially enclosed with a coating (128), in particular with an epoxy resin coating, using a transfer molding process.