Fluid Sensor Package Sealing Layers Prevent PCB Short Circuits
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Solution Overview
Problem
Integrated circuit (IC) sensors used for fluid sensing face challenges due to fluid contact with the porous surface of printed circuit boards (PCBs), which can alter fluid properties and cause short circuits with metal interconnects, compromising sensing operations and safety.
Innovation Solution
A substrate with a first sealing layer, including a copper, nickel, and gold or silver sub-layers, covers the inner surface of openings to reduce fluid contact with the PCB surface, and a second sealing layer surrounds metal interconnects to prevent short circuits, while ensuring the fluid can still contact the sensor surface for property sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PCB surface is left porous and exposed, then manufacturing is simple and成本低, but fluid contact alters fluid properties and causes short circuits
Solution Approach 1:
The sealing structure is divided into multiple segments: a first sealing layer covering the inner surface of the opening, a second sealing layer between the substrate and sensor, and a third sealing layer around metal interconnects. Each sealing layer performs a specific protective function, collectively preventing fluid contact with the PCB surface while maintaining manufacturing feasibility through modular construction
Solution Approach 2:
Sealing layers act as intermediary barriers between the fluid environment and the PCB substrate. These intermediate structures prevent direct contact between fluid and the porous PCB surface, eliminating the harmful interaction while allowing the sensor to function through controlled openings in the sealing layers
2Reliability
If sealing layers are added to prevent fluid contact, then short circuits are prevented, but manufacturing complexity increases
Solution Approach 1:
The first sealing layer is formed over the inner surface of the opening before the sensor is mounted. This preliminary sealing action prevents fluid from reaching the PCB surface during subsequent assembly steps, ensuring electrical safety is built into the structure before final assembly, thereby managing complexity through staged manufacturing
3Reliability
If the sensor surface is covered to protect from fluid, then PCB surface contact is reduced, but fluid cannot contact the sensor for sensing
Solution Approach 1:
The sealing layers are designed with localized openings that allow fluid contact only at the sensor surface where sensing is required. The first sealing layer covers the PCB opening inner surface to prevent fluid contact with the substrate, while the second sealing layer includes openings that expose the sensor surface to fluid. This creates different local properties: protected areas prevent short circuits, while exposed areas enable sensing functionality
Data Source
AI summary
In examples, an apparatus comprises a substrate having opposite first and second surfaces. The substrate includes a first opening through the substrate. The substrate includes a first sealing layer covering an inner surface of the first opening, with the inner surface extending between the first and second surfaces. The substrate includes contact pads on the second surface. The apparatus also comprises a fluid sensor having a sensor surface facing the second surface and the first opening. The apparatus further includes metal interconnects coupled between the sensor surface and the contact pads. The apparatus also includes a second sealing layer between the second surface and the sensor surface, in which the second sealing layer surrounds the metal interconnects and includes a second opening below the first opening, and at least part of the sensor surface is exposed through the first and second openings.