Embedded Mass Flow Sensor Die for Laminar Liquid Gas Flow
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Solution Overview
Problem
Existing mass flow sensor packages face issues with turbulence and manufacturing challenges due to spacer alignment and die attach bond line thickness variations, which affect the accuracy and longevity of the sensor.
Innovation Solution
A mass flow sensor module with a semiconductor sensor die embedded in a substrate, eliminating the need for a spacer and maintaining the die surface at the same level as the substrate, ensuring laminar flow and reducing wire bonding complexity, while providing an air-tight seal and thermal enhancement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spacer is used to align the housing with the die surface to prevent turbulence, then flow laminarity is improved, but manufacturing complexity and critical dimension control become worsened
Solution Approach 1:
The invention removes the spacer component entirely from the assembly. Instead of using a separate spacer to maintain the required distance between the housing and die, the housing is designed with an integrated structure that directly interfaces with the die, eliminating the need for spacer alignment and bond line thickness control.
Solution Approach 2:
The housing structure is merged with the die mounting structure, combining what were previously separate components (housing and spacer) into a single integrated housing that performs both protective and positioning functions, thereby eliminating critical dimension control requirements.
2Ease of manufacture
If the die is directly attached to the substrate surface, then manufacturing simplicity is improved, but wire bonding complexity increases due to longer wire lengths and higher loop heights
Solution Approach 1:
The invention transitions from a planar die attachment to a three-dimensional embedded structure. The die is recessed into the substrate, creating a stepped configuration where the die sits in a depression. This dimensional change allows the wire bonds to follow a shorter, more direct path between the die and substrate surface, reducing wire length and loop height while maintaining ease of die attachment.
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 accuracy and reliability of mass flow measurements by minimizing turbulence and eliminating the need for critical bond line thickness control, ensuring consistent performance and protecting the die from contamination.
Implementation Method 1
Mass flow sensing semiconductor devices are known for measuring the flow of gas or liquid across a sensing surface using the thermo-transfer (calorimetric) principle
Implementation Method 2
One type of semiconductor flow sensor uses a thermal process that utilizes a heating element and two differentially arranged thermocouples to measure the temperature gradient as an indicator of the flow rate
Data Source
AI summary
A mass flow sensor module and method of manufacture thereof are provided, wherein a semiconductor sensor die is integrated within an enhanced molded housing structure that maintains an air tight seal and protects the die from abrasive wear, and which also provides laminar flow of the liquid gas to be sensed. Since the die is embedded in the substrate; there is no need for a spacer for reducing die thickness induced flow turbulence. Moreover, the die surface is at the same level as the top surface of the substrate, such that there is no performance impact due to die thickness variation and therefore no die attach bond line thickness control requirement. In one embodiment, a thermal enhancement capability is provided.