Intermetallic Bonded Inductor on Sacrificial Substrate

Solution Overview

Problem

Existing methods for manufacturing electrical inductors on multilayer circuit boards face limitations in reducing spiral spacing for increased inductance while maintaining operational bandwidth, with polymer substrates having minimum spacing constraints and semiconductor approaches suffering from reduced bandwidth and increased loss due to material characteristics.

Innovation Solution

A method involving a sacrificial substrate and intermetallic bonding between conductive layers, using a first metal with a higher melting point and a second metal with a lower melting point, along with a dielectric layer like liquid crystal polymer, to form electrical inductors with enhanced resolution and reduced self-resonance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If polymer substrates are used for spiral inductive elements, then manufacturing is easier, but spiral spacing must be greater than or equal to 50 μm which limits inductance density

Engineering Contradiction:

Improveease of manufactureVSAvoidspiral spacing

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The substrate is divided into two distinct parts: a polymer substrate providing mechanical support and electrical isolation, and a separate semiconductor layer providing high-precision spiral trace fabrication. This segmentation allows each material to fulfill its optimal function without compromise.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from planar spiral traces to three-dimensional vertically stacked spiral traces on the semiconductor layer, enabled by vias connecting multiple levels. This vertical dimensionality multiplication increases inductance density without increasing footprint area.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If semiconductor substrates are used for spiral inductive elements, then manufacturing resolution allows reduced spiral spacing, but operating bandwidth decreases and loss increases due to electrical characteristics

Engineering Contradiction:

Improvespiral spacingVSAvoidenergy loss

Core Design Contradiction:

Manufacturing precisionVSLoss of energy

Solution Approach 1:

The substrate is divided into two distinct parts: a polymer substrate providing mechanical support and electrical isolation, and a separate semiconductor layer providing high-precision spiral trace fabrication. This segmentation allows each material to fulfill its optimal function without compromise.

Inventive Principle:

Principle #1Segmentation

3Manufacturing precision

If semiconductor substrates are used for spiral inductive elements, then manufacturing resolution allows reduced spiral spacing, but self-resonance occurs at low frequencies making the inductor unusable

Engineering Contradiction:

Improvespiral spacingVSAvoidoperational bandwidth

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The substrate is divided into two distinct parts: a polymer substrate providing mechanical support and electrical isolation, and a separate semiconductor layer providing high-precision spiral trace fabrication. This segmentation allows each material to fulfill its optimal function without compromise.

Inventive Principle:

Principle #1Segmentation

4Reliability

If a thick insulating layer is inserted between semiconductor layer and spiral inductive elements to prevent DC shorting, then electrical isolation is improved, but board size and cost increase

Engineering Contradiction:

Improveelectrical isolationVSAvoidboard size

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The substrate is divided into two distinct parts: a polymer substrate providing mechanical support and electrical isolation, and a separate semiconductor layer providing high-precision spiral trace fabrication. This segmentation allows each material to fulfill its optimal function without compromise.

Inventive Principle:

Principle #1Segmentation

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

Enables the formation of electrical inductors with tighter spiral spacing and increased operational bandwidth, achieving 80% size reduction and self-resonant frequency enhancement up to 18 GHz, suitable for both RF and digital circuitry on a single substrate.

Implementation Method 1

heating and pressing the aligned first and second subunits to form an intermetallic compound of the first and second metals bonding adjacent metal portions together

Methodology Applied

Scientific EffectIntermetallic bonding: Welding

Implementation Method 2

removing the sacrificial substrate

Methodology Applied

Scientific EffectSacrificial substrate removal:

Data Source

PatentUS9159485B2Method for making an electrical inductor and related inductor devices

Publication Date: 2015.10.13 HARRIS CORP

AI summary

A method is for making an electrical inductor. The method includes forming a first subunit having a sacrificial substrate, and an electrically conductive layer defining the electrical inductor and including a first metal on the sacrificial substrate. The method includes forming a second subunit having a dielectric layer and an electrically conductive layer thereon defining electrical inductor terminals and having the first metal, and coating a second metal onto the first metal of one of the first and second subunits. The method includes aligning the first and second subunits together, heating and pressing the aligned first and second subunits to form an intermetallic compound of the first and second metals bonding adjacent metal portions together, and removing the sacrificial substrate.