Hybrid Sensor Packaging Aperture for Stress Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensor packaging methods face challenges in minimizing mechanical stress on sensitive sensors, ensuring environmental access, isolating non-active sensor regions, and reducing parasitic interconnections, particularly for capacitive and mechanically sensitive sensors like pressure sensors.
Innovation Solution
A hybrid integration approach with an ASIC package featuring an aperture for chip-to-chip bonding, minimal package contact with the sensor chip, underfill and lateral fill materials to reduce stress and contamination, and a metal guard ring for enhanced protection, allowing for independent design and minimal interconnect length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the package is molded directly to the hybrid assembly, then the gel volume is reduced or eliminated, but excessive mechanical stress is imposed on the sensor chip
Solution Approach 1:
The package structure is segmented into distinct regions: a molded package body surrounding the electronics chip, and an aperture region leaving the sensor chip exposed. This segmentation allows the molded portion to protect the electronics while the aperture prevents mechanical stress on the sensor chip during molding.
Solution Approach 2:
Different regions of the package have different properties: the molded regions provide protection and isolation, while the aperture region provides mechanical relief. The package applies mechanical constraint locally to the electronics chip while leaving the sensor chip region stress-free.
2Device complexity
If separate electronics and sensor chips are placed in a pre-molded package with overfill gel, then the sensor and electronics are in close proximity, but contaminants can be absorbed by the gel and reach the electronics chip
Solution Approach 1:
The harmful overfill gel is extracted from the package cavity, replacing it with air or vacuum. This eliminates the gel's contaminant absorption problem while maintaining the close proximity advantage of hybrid integration through direct chip-to-chip bonding in the aperture region.
Solution Approach 2:
The package interior is filled with an inert atmosphere (air or vacuum) instead of absorbent gel. This creates a non-reactive environment that prevents contaminant absorption and transport to the electronics chip, while still allowing close physical proximity of components.
3Ease of operation
If the sensor chip is exposed to the environment through an aperture, then environmental access is provided, but the rest of the sensor and electronics must be isolated
Solution Approach 1:
The package is segmented into an exposed aperture region for environmental access and a molded sealed region for protection. This segmentation allows the sensor active area to access the environment while the electronics and non-active sensor regions remain isolated within the molded portion.
Solution Approach 2:
The package structure uses vertical dimensionality with the sensor chip positioned at the aperture opening, allowing environmental access from above while the molded package body provides lateral and bottom isolation. This dimensional arrangement simplifies the isolation requirement.
4Adaptability or versatility
If wire bonding is used to connect sensor and electronics, then flexibility is provided, but long interconnections introduce significant parasitic effects
Solution Approach 1:
The sensor chip and electronics chip are merged into a single hybrid assembly with direct chip-to-chip bonding interfaces. This merging eliminates long wire bonds and reduces interconnection length, thereby minimizing parasitic effects while maintaining electrical connectivity.
Solution Approach 2:
Instead of using long external wire bonds, the connection approach is inverted to direct face-to-face chip bonding. This reverses the interconnection topology from external lengthy paths to internal short paths, reducing parasitics.
Data Source
AI summary
Improved sensor packaging is provided with a hybrid integration approach. In one example, an application specific integrated circuit (ASIC) for sensor signal conditioning is packaged. The ASIC package has an aperture in it that exposes a chip to chip bonding interface of the ASIC chip. The rest of the ASIC chip is surrounded by the package, including the connections between the external package leads and the ASIC chip. A sensor chip, also having a chip to chip bonding interface, is disposed in the package aperture and bonded to the ASIC chip such that the two chip to chip bonding interfaces are connected. Flip chip bonding of the sensor chip to the ASIC chip is a preferred approach for chip to chip bonding. The vertical gap between the two chips can be filled in by an underfill process. The lateral gap between the sensor chip and the package can also be filled.