Isolated Leadframe Package Layout for Higher Hall Sensor Gain
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Solution Overview
Problem
Semiconductor device packages with sensors, such as Hall-effect devices, face reduced signal gain due to the thickness of the semiconductor die when mounted in a face-up orientation, which increases the distance between the sensor and the leadframe, while flip chip mounting is costly and not economically viable for all applications.
Innovation Solution
A semiconductor device package design featuring a metal leadframe with isolated portions, where a semiconductor die with a sensor is cantilevered and mounted to an isolation barrier on the leadframe, with bond pads exposed in an opening, allowing for reduced distance between the sensor and the leadframe, and electrical connections are made using wire bonds or ribbon bonds to a second portion of the leadframe, covered with mold compound for protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a wire bonded semiconductor die mount is used with the die mounted facing away from the leadframe, then the package structure is simple and cost-effective, but the sensor gain is reduced due to increased distance between the sensor and the leadframe
Solution Approach 1:
The patent changes the mounting orientation from face-up to face-down, utilizing the vertical dimension to bring the sensor closer to the leadframe. By mounting the die face-down with the sensor on the bottom surface, the distance between the sensor and the leadframe is minimized, thereby increasing sensor gain while maintaining the wire bonding process simplicity
Solution Approach 2:
The patent inverts the conventional mounting orientation by mounting the semiconductor die face-down instead of face-up. This inversion allows the sensor, which is typically on the top surface, to be positioned on the bottom surface closer to the leadframe, resolving the contradiction between manufacturing simplicity and sensor performance
2Measurement precision
If a flip chip semiconductor die mounting is used, then the sensor gain is improved by reducing the distance between the sensor and the leadframe, but the manufacturing cost increases significantly
Solution Approach 1:
The patent extracts the key benefit of flip chip mounting (reduced distance between sensor and leadframe) while eliminating the costly aspects (complex reflow soldering process, under bump metallization, and specialized equipment). By using face-down wire bonding, the patent achieves the distance reduction without requiring the expensive flip chip process
Solution Approach 2:
The patent replaces the expensive flip chip process with a more economical wire bonding approach. By mounting the die face-down and using wire bonds for electrical connections, the patent achieves similar geometric benefits to flip chip but with lower manufacturing costs and simpler processes
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 sensor gain by minimizing the distance between the sensor and the leadframe, maintaining low costs similar to wire bonded packages, and using conventional materials and processes, thus offering a cost-effective solution with improved performance.
Implementation Method 1
In a particular type of sensor, a Hall-effect device is used to sense a magnetic field that occurs when a current is conducted through a conductor
Data Source
AI summary
An example apparatus includes a metal leadframe that includes: first leads in a first portion; second leads in a second portion spaced from the first leads, the second leads isolated from the first leads; an isolation barrier mounted to a board side surface of the first portion of the metal leadframe; a semiconductor die mounted to the isolation barrier, the semiconductor die having a sensor on a device side surface facing the first portion of the leadframe, the semiconductor die cantilevered and having bond pads on the device side surface exposed in the opening in the metal leadframe; electrical connections coupling the bond pads and second leads in the second portion of the metal leadframe; and mold compound covering the semiconductor die, the electrical connections, the isolation barrier and portions of the first leads and the second leads, the mold compound forming a package body.