Multi-Substrate Transformer Package for Magnetostriction Isolation
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Solution Overview
Problem
Magnetic-coupling isolation barriers in transformers used for galvanic isolation in solid state switches face manufacturing challenges due to the inclusion of a magnetic core, which complicates integrated circuit (IC) packages.
Innovation Solution
A transformer-based IC package is designed with a magnetic core and galvanically separate coils on multiple substrates, utilizing conductive traces and underfill material to manage magnetostriction, eliminating the need for wire bonds and providing galvanic isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic core is used in transformer-based galvanic isolation, then magnetic coupling and flux channeling are achieved, but manufacturing complexity and device complexity increase
Solution Approach 1:
The transformer package is divided into multiple substrates (first substrate, second substrate, third substrate) that are stacked vertically. Each substrate carries specific components and interconnect structures. This segmentation allows the magnetic core to be integrated between substrates without requiring complex planar winding structures, thereby reducing manufacturing complexity while maintaining galvanic isolation functionality.
Solution Approach 2:
The patent transitions from traditional planar transformer layouts to a three-dimensional stacked architecture. The magnetic core is positioned vertically between substrates in the Z-dimension, with primary and secondary windings distributed across different horizontal planes. This dimensional change simplifies the integration process and reduces the manufacturing steps required compared to conventional two-dimensional transformer designs.
2Reliability
If traditional transformer structures are used, then galvanic isolation is provided, but package size and cost increase
Solution Approach 1:
The magnetic core is nested between the first and second substrates, with primary windings on the first substrate and secondary windings on the second substrate. The third substrate is nested below the magnetic core, creating a compact vertical stack. This nested arrangement maximizes the use of vertical space and minimizes the horizontal footprint of the transformer package.
Solution Approach 2:
By stacking substrates and the magnetic core vertically in the Z-dimension, the patent achieves compact packaging with reduced horizontal footprint. The galvanic isolation transformer fits within a smaller planar area compared to traditional lateral winding structures, while the vertical integration maintains the required magnetic coupling and electrical isolation.
3Ease of manufacture
If magnetic core is integrated in IC package, then transformer functionality is achieved, but magnetostriction effects increase
Solution Approach 1:
The magnetic core is extracted from direct contact with the substrate surfaces by positioning it between the first and second substrates with gaps on all sides. This extraction isolates the magnetic core from mechanical constraints, allowing it to expand and contract freely during magnetostriction cycles without generating stress or deformation that would harm nearby components.
Solution Approach 2:
The patent preemptively addresses magnetostriction by designing gaps between the magnetic core and substrates before the harmful effects can manifest. These gaps prevent the transmission of magnetostriction-induced stress to the substrate and surrounding components, thereby eliminating the harmful effects before they can occur.
4Reliability
If galvanic isolation is implemented, then DC current blocking is achieved, but parasitic DC resistance increases
Solution Approach 1:
The conductive traces are segmented into distinct primary and secondary groups on separate substrates, with galvanic isolation achieved through the magnetic coupling structure. This segmentation allows each trace group to be optimized independently for low resistance while maintaining the isolation barrier, reducing overall parasitic resistance compared to monolithic isolation structures.
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 enables smaller, less costly, and more scalable IC packages with reduced magnetostriction, lower parasitic DC resistance, and improved electrical isolation, meeting safety standards for voltage isolation.
Implementation Method 1
Transformers used for magnetic-coupling isolation barriers typically utilize a magnetic core to provide a magnetic path to channel flux created by the currents flowing in the primary and secondary sides of the transformer
Implementation Method 2
Magnetic coupling typically relies on use of a transformer to magnetically couple circuits on the different sides of the transformer, typically referred to as the primary and secondary sides, while also providing galvanic separation of the circuits
Implementation Method 3
A transformer-based integrated circuit (IC) package can include: a magnetic core including a soft ferromagnetic material
Data Source
AI summary
Isolation transformer packages and structures and related methods reduce or minimize deleterious effects arising from magnetostriction during operation of the included transformer. An example transformer based integrated circuit package includes first and second substrates that include a space for receiving a magnetic core and that are joined together. A magnetic core is disposed in the space defined by the substrates, with the magnetic core including a soft ferromagnetic material. The space between surfaces of the substrates and an exterior surface of the magnetic core allows the magnetic core to expand and contract during operation. Pluralities of conductive traces of both substrates, having first and second galvanically separate groups, form first and second transformer coils disposed about the magnetic core. An injection port can be disposed in the first or second substrate to allow injection of underfill into one or more regions between the first substrate and the second substrate.