Pressure Sensor Assembly Using Retractable Cavity Pin
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Solution Overview
Problem
Current pressure sensor device packaging is prone to mechanical damage and is costly due to the use of pre-molded lead frames, which are not robust and can result in mold-related defects such as gel bleed, flashing, and voids.
Innovation Solution
A method of assembling pressure sensor devices by attaching the die to a substrate, using a retractable cavity pin to form a cavity after electrical connection, and then dispensing a molding compound and gel material to encapsulate the die, eliminating the need for pre-molded lead frames and reducing packaging costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pre-molded lead frames are used to package pressure sensor dies, then the dies are protected from mechanical damage, but the packaging costs increase and mold-related defects occur
Solution Approach 1:
The patent removes the pre-molded lead frame from the packaging process entirely. Instead, the sensor die is mounted directly to a substrate and encapsulated with molding compound, eliminating the intermediate lead frame component that causes cost and manufacturing complexity issues while still providing mechanical protection.
Solution Approach 2:
The substrate is prepared with mounting structures and electrical connections before the die is attached. This preliminary preparation allows the die to be directly mounted and encapsulated without requiring pre-molded lead frames, simplifying the overall packaging process and reducing costs.
2Reliability
If pre-molded lead frames are used to create cavities for gel coating, then the sensor die is protected, but gel bleed and voids occur during packaging
Solution Approach 1:
The patent eliminates the pre-molded cavity structure from the lead frame and instead forms the cavity directly in the substrate or creates it during the encapsulation process. This removes the interface between pre-molded cavities and gel material that causes gel bleed and void formation.
Solution Approach 2:
Instead of pre-molding the cavity shape in the lead frame and then filling with gel, the patent inverts the approach by either forming the cavity in the substrate itself or creating the cavity space during the encapsulation process, ensuring better gel material distribution and eliminating defects.
3Strength
If pre-molded lead frames are used for packaging, then structural support is provided, but cavity height inconsistency and parametric shifts occur during rapid decompression
Solution Approach 1:
The patent removes the pre-molded lead frame structure and replaces it with a substrate-based mounting approach. The substrate provides the necessary structural support while allowing for more consistent cavity formation and better resistance to parametric shifts during rapid decompression events.
Solution Approach 2:
The patent uses composite structures combining the substrate material with the molding compound encapsulation. This composite approach provides both structural support and consistent cavity formation, improving resistance to mechanical stress and parametric shifts during rapid decompression while maintaining manufacturing precision.
Data Source
AI summary
A method of assembling a pressure sensor device includes providing a substrate having a plurality of substrate connection pads. A pressure sensor die is attached to a first major surface of the substrate and bond pads of the pressure sensor die are electrically connected to the respective substrate connection pads. A retractable cavity pin is placed on the first major surface of the substrate such that the cavity pin covers the pressure sensor die and the electrical connections to the die. A molding compound is then dispensed onto the first major surface of the substrate such that the molding compound surrounds the pressure sensor die and the cavity pin. The cavity pin is retracted such that a cavity is formed around the pressure sensor die and a gel material is dispensed within the cavity such that the gel material fills the cavity and covers the pressure sensor die.