Micromechanical Sensor Rear-Side Rewiring for Media Resistance
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Solution Overview
Problem
Existing micromechanical sensor systems face challenges in robust and cost-efficient packaging, particularly for absolute and differential pressure sensors, as they require media-resistant designs that isolate electrical contacts from the sensor detection area to prevent medium interference.
Innovation Solution
The method involves forming vias in the molding compound during the molding process, using connector pins that become exposed after carrier removal, allowing for electrical contacting through these vias to the rear side of the sensor, and applying a rewiring device using screen printing or thin film techniques, with an isolation layer and adhesive layer for bonding and stress relief.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrical contacts are positioned on the front side of the sensor chip, then the rewiring process becomes complex and media interference cannot be prevented, but if electrical contacts are positioned on the rear side, then media-resistant design is achieved but the packaging process becomes more complex
Solution Approach 1:
The sensor system is divided into two distinct sides: the front side contains only the diaphragm detection area free from electrical contacts, while the rear side contains all electrical contacts and rewiring structures. This segmentation allows the front side to be fully media-resistant while isolating electrical components to the rear side, resolving the contradiction between media resistance and packaging complexity.
Solution Approach 2:
Electrical contacts and rewiring structures are extracted from the front side (detection area) and relocated to the rear side of the sensor chip. This extraction eliminates media interference from the detection area while consolidating electrical components in a dedicated zone, achieving media-resistant design without excessive packaging complexity.
2Ease of manufacture
If multiple separate packaging technologies are used for different components, then component-specific requirements are met, but manufacturing cost and process complexity increase, but if a single packaging technology is used, then manufacturing is simplified but component-specific requirements may not be met
Solution Approach 1:
The molded housing is designed as a universal packaging structure that can accommodate multiple types of components (sensor chips, ASICs, capacitors) with different requirements. The housing provides simultaneous mechanical protection, electrical isolation, and media resistance for all components, eliminating the need for separate packaging technologies while meeting diverse component-specific requirements.
Solution Approach 2:
Multiple packaging functions (mechanical protection, electrical isolation, media resistance, stress relief) are merged into a single molded housing structure. This consolidation simplifies manufacturing to one packaging process while the housing's integrated design features (such as recesses, adhesive layers, and structural configurations) accommodate different component types, achieving both ease of manufacture and adaptability.
3Reliability
If the diaphragm area and rewiring area are integrated in the same plane, then the chip structure is simplified, but aggressive media can affect the rewiring area and cause corrosion, but if they are separated, then media resistance is improved but the chip design becomes more complex
Solution Approach 1:
The chip is segmented into two functional zones: the diaphragm area for pressure sensing and the rear side for electrical contacts and rewiring. This spatial segmentation physically separates the media-exposed detection area from the electrical components, preventing aggressive media from reaching the rewiring area while maintaining a relatively simple chip design through functional zoning.
Data Source
AI summary
A micromechanical sensor system includes a micromechanical sensor chip surrounded at least laterally by a molded housing which has a front side and a rear side. The micromechanical sensor chip includes a chip area on the rear side, which is omitted from the molded housing, and a rewiring device formed on the rear side, which, starting from the chip area, extends to the surrounding molded housing on the rear side, and from there, past at least one via from the rear side to the front side of the molded housing.