PCB Step Barrier for Sensor Hermetic Sealing
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Solution Overview
Problem
Magnetic passive position sensors (MAPPS) in fuel tanks face issues with contamination and corrosion due to undesired wetting of conductor tracks by auxiliary materials used in soldering processes, which can impair the hermetic sealing and contact functionality.
Innovation Solution
A printed circuit board design featuring a substrate with a step-like variation in thickness to act as a barrier against auxiliary materials, preventing unwanted wetting of conductor tracks and ensuring hermetic sealing, achieved through the use of a metal-containing sintering paste that forms a cohesive bond with a cover, either by soldering, adhesive bonding, or welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If auxiliary material (flux) is added to promote cohesive bond during soldering, then wetting of the contact face is improved, but undesired wetting of conductor tracks occurs causing contamination and corrosion
Solution Approach 1:
The substrate surface is segmented into different functional zones: a contact face region that is wettable by auxiliary material for bonding, and a protected region where conductor tracks are located. This segmentation is achieved through geometric features (steps, recesses, or raised structures) that create physical boundaries, allowing the auxiliary material to be confined to the contact face while preventing it from reaching the conductor tracks.
Solution Approach 2:
Different regions of the substrate are given different surface properties: the contact face is designed to be wettable by auxiliary material (through material selection or surface treatment), while the regions containing conductor tracks are designed to be non-wettable or protected. This local differentiation of surface quality allows selective wetting behavior, enabling effective bonding without contaminating sensitive areas.
2Object-affected harmful factors
If the substrate is encapsulated hermetically to protect conductor tracks, then protection from contamination and corrosion is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
Instead of encapsulating the entire substrate structure, the invention extracts and isolates only the critical sensitive elements (conductor tracks) from the harmful environment. This is achieved by creating localized protective features such as recesses that shield conductor tracks from auxiliary material, or by selectively applying protective coatings only where needed, rather than implementing full encapsulation.
Solution Approach 2:
The protection mechanism is shifted from a vertical encapsulation approach to a horizontal/planar approach using surface geometric features. Steps, recesses, and raised structures on the substrate surface create physical barriers that prevent auxiliary material from reaching conductor tracks during the bonding process, eliminating the need for complex three-dimensional encapsulation structures.
3Strength
If the contact face is made wettable by auxiliary material, then cohesive bonding is enhanced, but the auxiliary material spreads to other faces causing unwanted wetting
Solution Approach 1:
The substrate is pre-configured with geometric features (steps, recesses, or raised structures) that create physical boundaries before the bonding process begins. These pre-formed structures act as barriers that confine the auxiliary material to the contact face region, preventing it from spreading to other areas. The preliminary geometric configuration ensures that even when auxiliary material is applied, it cannot reach sensitive regions.
Solution Approach 2:
The geometric features (steps, recesses, raised structures) act as intermediary elements between the contact face and the conductor track regions. These intermediaries physically separate the wettable contact face from the non-wettable protected regions, mediating the wetting behavior by allowing auxiliary material to access the contact face while blocking its path to the conductor tracks.
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 step-like substrate configuration effectively prevents contamination and corrosion, ensuring reliable hermetic sealing and maintaining the integrity of the conductor tracks and contact spring structure, making the sensor suitable for various fuel types without dependence on specific fuel compositions.
Implementation Method 1
the use of such an auxiliary material can lead to undesired wetting of other faces of the printed circuit board side to be encapsulated than said contact or connecting face
Implementation Method 2
achieved through the use of a metal-containing sintering paste that forms a cohesive bond with a cover
Data Source
AI summary
A printed circuit board having conductor tracks formed on one side of a substrate. The substrate is able to be cohesively bonded at a contact face to a cover for protecting the conductor tracks. In this case, the substrate includes a step, which forms a barrier with respect to an auxiliary material for promoting the cohesive bond, in order to prevent any wetting of the conductor tracks with the auxiliary material. A sensor having a printed circuit board for use in a fuel filling level measurement system of a vehicle.