IC Package Magnet Channel Structure for Low-Cost Field Sensing
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Solution Overview
Problem
Integrated circuit magnetic field sensors face challenges in cost reduction due to the high expense of hard magnetic materials used for back bias magnets, and existing fabrication techniques like molding can introduce performance variations and stress issues.
Innovation Solution
A magnetic field sensor design incorporating a lead frame, semiconductor die, and ferromagnetic mold material with a non-contiguous central region and taper, secured by a non-conductive mold material, which can include a separately formed element, and a molded ferromagnetic suppression device to enhance adhesion and reduce stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hard magnetic materials are used for back bias magnets, then magnetic field sensing performance is improved, but manufacturing cost increases
Solution Approach 1:
The patent changes the material parameter from hard magnetic material to ferromagnetic material, and changes the magnetic field generation method from permanent magnet to electromagnet. This allows achieving the same magnetic field sensing performance while using less expensive materials and enabling post-assembly magnetization to ensure performance.
Solution Approach 2:
The patent replaces expensive hard magnetic materials with cheaper ferromagnetic materials that can be magnetized after assembly. The electromagnet coil can be replaced or re-magnetized if needed, providing a cost-effective solution that maintains performance.
2Productivity
If molding techniques are used to fabricate sensors, then manufacturing efficiency is improved, but performance variations and stress issues occur
Solution Approach 1:
The patent divides the sensor fabrication into separate stages: first forming the sensor chip without the magnet, then separately assembling the electromagnet component. This segmentation allows each component to be optimized independently, avoiding the performance variations caused by molding the entire assembly as one piece.
Solution Approach 2:
The sensor chip is prepared and tested before the magnet assembly is attached. This preliminary action allows quality control and performance verification to occur at an earlier stage, preventing defective assemblies from proceeding to final packaging.
3Ease of manufacture
If ferromagnetic material is tapered, then removal from mold is improved, but structural complexity increases
Solution Approach 1:
The patent applies a taper to the ferromagnetic material, creating a curved or angled surface that facilitates easy removal from the mold. This geometric modification is a simple and effective way to solve the mold removal problem without significantly increasing overall structural complexity.
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 reduces the cost of magnetic field sensors by utilizing less expensive ferromagnetic materials and minimizes performance variations by integrating the sensor components, while the tapered ferromagnetic mold material facilitates easier removal and reduces stress during fabrication.
Implementation Method 1
the ferromagnetic mold material is magnetized
Implementation Method 2
a magnetic field sensing element, or transducer... to detect aspects of movement of a ferromagnetic article
Data Source
AI summary
An integrated circuit package and method of fabrication are described. The integrated circuit package includes a lead frame having a first surface and a second opposing surface and a semiconductor die having a first, active surface in which circuitry is disposed and a second opposing surface attached to the first surface of the lead frame. A magnet attached to the second surface of the lead frame has a non-contiguous central region and at least one channel extending laterally from the central region. An overmold material forms an enclosure surrounding the magnet, semiconductor die, and a portion of the lead frame.