Planar Transformer Windings in Wafer Level IMD Packaging

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Solution Overview

Problem

Current implantable medical device (IMD) packaging faces challenges in downsizing due to the large size of conventional flyback transformers and other passive components, which occupy significant space within the hermetically sealed canister, hindering further miniaturization for more comfortable implantation.

Innovation Solution

The integration of primary and secondary windings of a transformer within a wafer level package, where a planar magnetic core is embedded within the artificial wafer and bonded to the surface, allowing for a compact configuration of windings across multiple routing layers, reducing the core gap and minimizing the overall size of the transformer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If conventional flyback transformers are used in IMD packaging, then the transformer can provide necessary voltage transformation, but the device size becomes too large for comfortable implantation

Engineering Contradiction:

Improvetransformer sizeVSAvoidvoltage transformation performance

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent transitions from conventional three-dimensional flyback transformers to a planar two-dimensional configuration. The transformer windings are formed on opposite faces of a printed circuit board, with a planar magnetic core embedded between them. This dimensional change allows the transformer to maintain its voltage transformation function while dramatically reducing the volume occupied within the IMD canister, enabling more comfortable implantation.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent integrates the magnetic core and windings into a unified planar structure. The planar magnetic core is embedded between the PCB faces, with windings formed directly on the board surfaces, merging previously separate components (core, windings, PCB) into a compact integrated assembly. This merging eliminates the need for traditional bulky transformer housing and associated components.

Inventive Principle:

Principle #5Merging (Combining)

2Volume of moving object

If planar flyback transformers with embedded windings are used, then the transformer size is reduced, but further downsizing is still needed for optimal implant comfort

Engineering Contradiction:

Improvetransformer sizeVSAvoidcore gap dimension

Core Design Contradiction:

Volume of moving objectVSLength of moving object

Solution Approach 1:

The patent optimizes the core gap parameter by embedding the planar magnetic core directly between the PCB faces containing the windings. This configuration minimizes the air gap distance compared to conventional designs, thereby reducing magnetic flux leakage and improving coupling efficiency. The parameter change in core gap dimension enables further transformer downsizing while maintaining effective voltage transformation.

Inventive Principle:

Principle #35Parameter changes

3Volume of moving object

If conventional separate component assembly is used, then manufacturing is straightforward, but the overall device size becomes too large

Engineering Contradiction:

Improvetransformer sizeVSAvoidassembly complexity

Core Design Contradiction:

Volume of moving objectVSEase of manufacture

Solution Approach 1:

The patent forms the transformer windings directly on the printed circuit board during the PCB manufacturing process, before final assembly. The magnetic core is then embedded into designated recesses in the PCB. This preliminary action of integrating winding formation into PCB fabrication eliminates subsequent complex assembly steps, maintaining ease of manufacture while achieving compact transformer dimensions.

Inventive Principle:

Principle #10Preliminary action

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 enables a significant reduction in the size of the transformer and other passive components, facilitating further downsizing of IMDs while maintaining effective performance, thereby enhancing the comfort and functionality of implantable medical devices.

Implementation Method 1

a planar magnetic core is embedded within the artificial wafer and bonded to the surface

Methodology Applied

Scientific EffectBonding: Adhesive

Implementation Method 2

the primary and secondary windings are formed in a planar spiral configuration, wherein each winding may be formed on more than one routing layer

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS9496241B2Integrated circuit packaging for implantable medical devices

Publication Date: 2016.11.15 MEDTRONIC INC

AI summary

A hybrid integrated circuit in a wafer level package for an implantable medical device includes one or more passive component windings formed, at least in part, along one or more routing layers of the package. The windings may be primary and secondary windings of a transformer, wherein all or part of a magnetic core thereof is embedded in a component layer of the wafer level package. If the core includes a part bonded to a surface of the package, that part of the core may be E-shaped with legs extending into the routing layers, and, in some cases, through the routing layers. Routing layers may be formed on both sides of the component layer to accommodate the transformer windings, in some instances.