Isolated Heat Slug Leadframe for Hall Sensor Package Alignment
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Solution Overview
Problem
Existing semiconductor device packages with Hall sensors face issues of misalignment and defects due to the displacement of leadframes during transfer molding, leading to increased assembly costs and reliability concerns, particularly when handling high voltage and current signals.
Innovation Solution
The use of a leadframe with isolated high and low voltage sections, coupled with a flexible connect mechanism for the heat slug, ensures proper alignment and reduces defects by allowing the heat slug to move during molding while maintaining leadframe integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid leadframe is used during transfer molding, then structural integrity is maintained, but misalignment and defects occur due to heat slug displacement
Solution Approach 1:
The leadframe is designed with flexible connect portions that allow it to dynamically adapt during transfer molding. These flexible sections enable the leadframe to accommodate heat slug displacement without rigid resistance, preventing misalignment defects while maintaining overall structural integrity through its articulated design
2Manufacturing precision
If the heat slug is fixed rigidly to the leadframe, then alignment is maintained, but molding defects and delamination occur due to displacement forces
Solution Approach 1:
The flexible connect portions act as flexible connections between the heat slug and leadframe. These flexible elements allow the heat slug to move independently during molding while maintaining its electrical and thermal connections, preventing delamination and package cracking that would occur with rigid fixation
3Reliability
If galvanic isolation is implemented with separate high and low voltage sections, then electrical safety is improved, but device complexity increases
Solution Approach 1:
The leadframe is segmented into distinct high voltage and low voltage sections that are electrically isolated from each other. This segmentation provides galvanic isolation for safety while the modular structure allows each section to be optimized independently, managing the complexity through functional separation
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 approach minimizes misalignment and delamination, enhancing the reliability and reducing production defects in semiconductor device packages, while maintaining galvanic isolation and thermal management for high voltage and current applications.
Implementation Method 1
Hall effect sensors with additional circuitry. Magnetic sensing can be used for motor control, position sensing, automation, current sensing and other applications. Hall effect sensors integrated in semiconductor devices can be formed by doping regions to include carriers that are sensitive to a magnetic field. A voltage proportional to a magnetic field is output by the Hall sensor while a current is applied to the Hall sensor in the presence of a magnetic field.
Implementation Method 2
The integral heat slug provides thermal dissipation out of the semiconductor device package and also provides a low resistance current path that routes current from the high voltage signal through the semiconductor device package and proximate to a Hall element on a semiconductor die.
Data Source
AI summary
A described example includes: a leadframe having a high voltage section and a low voltage section spaced from and electrically isolated from the high voltage section, and a heat slug mounted to the high voltage section. The high voltage section includes an input portion connected to the heat slug at an interior end by a mount portion, and further includes an interior lead portion that is connected to the mount portion by a flexible connect portion. An insulating material mounted to the heat slug provides a die mount area for a semiconductor die having a Hall element that is positioned so that the Hall element is proximate to the heat slug. Mold compound covers the semiconductor die, portions of the leadframe, and portions of the heat slug while a board side surface of the heat slug is exposed forming a thermal pad for a semiconductor device package.