Flow-Rate Sensor Resin Thinning to Prevent Diaphragm Deformation
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Solution Overview
Problem
Existing flow-rate sensors experience deterioration in detection accuracy due to diaphragm deformation during resin molding, which is not addressed in existing technologies.
Innovation Solution
A flow-rate sensor design featuring a lead frame with a semiconductor chip and a diaphragm, where a thinned portion in the resin covering the lead frame alleviates bending deformation by allowing differential shrinkage between the lead frame and resin, preventing diaphragm distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resin molding is performed to cover the lead frame and semiconductor chip, then the sensor structure is protected and sealed, but the diaphragm deforms due to compressive forces and shrinkage during molding
Solution Approach 1:
The resin is designed with different thicknesses in different regions: a thinned portion with smaller thickness is formed in the region facing the peripheral edge portion of the diaphragm, while other regions maintain larger thickness. This local variation in resin thickness allows the thinned portion to flexibly accommodate diaphragm deformation during molding, reducing stress concentration and preventing distortion of the flow rate detecting unit.
Solution Approach 2:
The thickness parameter of the resin is changed spatially to resolve the contradiction. By reducing the resin thickness in the thinned portion region, the resin's rigidity is locally reduced, enabling it to better accommodate the diaphragm's deformation during molding while still providing adequate protection in other areas.
2Strength
If the resin thickness is increased to improve sealing and protection, then structural strength is enhanced, but diaphragm deformation increases due to greater compressive forces
Solution Approach 1:
Instead of uniformly increasing resin thickness throughout, the invention applies different thickness values to different regions. The thinned portion has reduced thickness to minimize compressive forces on the diaphragm, while other regions maintain sufficient thickness for adequate sealing and protection, achieving an optimal balance between strength and deformation prevention.
3Ease of manufacture
If uniform resin thickness is used for simplicity of manufacturing, then production process is simplified, but diaphragm deformation occurs due to uneven stress distribution
Solution Approach 1:
The invention introduces a thinned portion with different thickness in a specific region of the resin, creating a localized structural variation that addresses diaphragm deformation. This can be implemented through standard molding techniques with appropriate mold design, balancing manufacturing feasibility with deformation control.
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
The design effectively prevents diaphragm deformation and maintains detection accuracy by ensuring the resin's thinned portion counteracts compressive forces, enhancing the sensor's reliability.
Implementation Method 1
a thinned portion 7 that is thinner than a periphery of the lower side resin portion 13b in a region facing a peripheral edge portion of the diaphragm 1... allowing differential shrinkage between the lead frame and resin... counteracts compressive forces
Data Source
AI summary
A flow-rate sensor is provided with a lead frame, a semiconductor chip that is disposed on one surface of the lead frame, and in which a diaphragm including a void portion on the lead frame side is formed, a flow rate detecting unit that is formed on the one surface including the diaphragm of the semiconductor chip, and resin that includes a flow passage opening portion exposing at least a portion of the flow rate detecting unit formed on the diaphragm, and covers the lead frame and the semiconductor chip. A lower side resin portion of the resin covering another surface side of the lead frame, on an opposite side to the one surface side thereof, has a thinned portion that is thinner than a periphery thereof in a region facing a peripheral edge portion of the diaphragm.