Multi-Die Pressure Sensor Package With Stacked Logic Die
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Solution Overview
Problem
Conventional pressure sensor packages are vulnerable to mechanical stress and corrosive effects, which can lead to unwanted signals and electrochemical degradation, particularly affecting contact pads with Al, AlCu, or Cu surfaces, and they lack a compact design.
Innovation Solution
The pressure sensor package design features a substrate with a pressure sensor and logic die attached on opposite sides, where the logic die is encapsulated in mold compound to protect against corrosion, and an open passage is formed to define a pressure port, with electrical conductors connected to both dies and a silicone gel used to decouple the pressure sensor from mechanical stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pressure sensor die is disposed laterally adjacent to the logic die on different regions of the substrate, then the assembly process is simplified, but the package size increases and mechanical stress vulnerability increases
Solution Approach 1:
The patent combines the pressure sensor die and logic die into a stacked configuration where the logic die is positioned directly above the pressure sensor die on the same substrate region. This vertical integration merges the spatial footprint of both components, significantly reducing the overall package size while maintaining electrical connectivity through wire bonds that pass through the logic die to reach the pressure sensor die below.
Solution Approach 2:
The invention transitions from a lateral (2D) arrangement of components to a vertical (3D) stacked configuration. By moving components from the same-plane lateral adjacency to different planes (one above the other), the design exploits the third dimension to reduce the planar footprint of the package while preserving all necessary functional connections.
2Ease of operation
If the pressure sensor die is mounted in a hole in the die paddle, then the pressure signal can impinge on the active surface, but the sensor becomes vulnerable to mechanical impact from assembly processes and housing
Solution Approach 1:
The patent introduces a stress relief layer (such as silicone gel or epoxy compound) as an intermediary material between the pressure sensor die and the rigid substrate. This intermediate layer acts as a mechanical buffer that decouples the fragile pressure sensor membrane from direct mechanical stress transmitted through the substrate during assembly and operation, while still allowing pressure signals to be transmitted to the sensor's active surface.
Solution Approach 2:
The design incorporates a compliant stress relief layer beneath the pressure sensor die before mounting it to the rigid substrate. This pre-installed cushioning layer is specifically positioned to absorb and distribute mechanical impacts and stresses that may occur during assembly processes or from external forces applied to the package, protecting the sensor membrane from damage before stress can cause failure.
3Ease of manufacture
If contact pads with Al, AlCu or Cu surfaces are exposed to the environment, then electrical connections are established, but corrosive effects accelerate degradation especially under constant voltage
Solution Approach 1:
The patent encapsulates the logic die, pressure sensor die, and wire bonds within a protective housing that creates a controlled, inert environment. This enclosure isolates the metal contact pads and wire bonds from exposure to corrosive environmental substances such as moisture, oxygen, and chemicals, thereby preventing electrochemical degradation and corrosion while maintaining all necessary electrical connections between components.
Solution Approach 2:
The design employs a combination of protective materials including conformal coating layers, encapsulants, and housing materials that form a composite protective barrier system. These multiple material layers work together to provide chemical corrosion resistance, moisture barrier properties, and mechanical protection, creating a multi-functional protective envelope around all vulnerable electrical components and connections.
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
This design enhances the immunity of the pressure sensor to mechanical impacts and corrosive effects, while maintaining a compact size by encapsulating the logic die and conductors in mold compound and using silicone gel for stress relief, thereby reducing signal noise and extending the sensor's operational lifespan.
Implementation Method 1
A mold compound completely encapsulates the second electrical conductors and at least partly encapsulates the logic die and the first electrical conductors
Implementation Method 2
using silicone gel used to decouple the pressure sensor from mechanical stress
Data Source
AI summary
A pressure sensor package includes a pressure sensor having a first side attached to a substrate and a second side opposite the first side, the first side having a pressure inlet aligned with an opening in the substrate, the second side having one or more electrical contacts. A logic die attached to an opposite side of the substrate as the pressure sensor is operable to process signals from the pressure sensor. First electrical conductors connect to the one or more electrical contacts of the pressure sensor. Second electrical conductors connect to one or more electrical contacts of the logic die. A mold compound completely encapsulates the second electrical conductors and at least partly encapsulates the logic die and the first electrical conductors. An open passage in the mold compound is aligned with the opening in the substrate so as to define a pressure port of the pressure sensor package.