Conductive Strip Bonding for High-Current Electronic Packages

Solution Overview

Problem

High current applications in electronic packages often result in high costs and low yields due to the need for multiple bonding wires, which can break under non-uniform contact resistance, especially in wire bonding processes.

Innovation Solution

The use of conductive strips for bonding die-to-die, die-to-lead, chip carrier-to-lead, or lead-to-lead connections, which can carry greater current than bonding wires and are stronger, replacing multiple wires, and can be bonded using surface mounting technology (SMT) with a bonding material.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If multiple bonding wires are used to carry high current, then the current carrying capacity is improved, but the cost increases and the reliability decreases due to wire breakage

Engineering Contradiction:

Improvecurrent carrying capacityVSAvoidwire breakage risk

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

Multiple bonding wires are merged into a single conductive strip that connects the same two bonding pads. The conductive strip integrates the current carrying function of multiple wires into one robust structure, eliminating the reliability issues associated with individual wire breakage while maintaining high current capacity through the combined cross-sectional area of the strip.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The conductive strip is formed as a composite structure comprising multiple wire-like conductors embedded within an insulating matrix material. This composite construction provides both the current carrying capacity of multiple wires and the mechanical strength and reliability of a unified structure, preventing the breakage issues that plague individual wire bonding.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If multiple bonding wires are used to carry high current, then the current carrying capacity is improved, but the manufacturing cost increases

Engineering Contradiction:

Improvecurrent carrying capacityVSAvoidmanufacturing cost

Core Design Contradiction:

Quantity of substanceVSEase of manufacture

Solution Approach 1:

Multiple bonding wires are merged into a single conductive strip that connects the same two bonding pads. The conductive strip integrates the current carrying function of multiple wires into one robust structure, eliminating the reliability issues associated with individual wire breakage while maintaining high current capacity through the combined cross-sectional area of the strip.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The conductive strip uses standard, inexpensive materials such as epoxy resin as the insulating matrix and conventional conductive materials for the wire-like conductors. This approach replaces expensive specialized high-current wire bonding processes with more economical materials and procedures that achieve the same or better performance.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If a conductive strip is used to replace multiple bonding wires, then the reliability is improved by reducing wire breakage, but the device complexity increases

Engineering Contradiction:

Improvewire breakage riskVSAvoidbonding structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The conductive strip structure is designed to be self-aligning and self-sustaining. The insulating matrix naturally holds the wire-like conductors in position, and the entire assembly bonds as a unified structure to the bonding pads, eliminating the need for complex alignment and bonding procedures that would increase device complexity.

Inventive Principle:

Principle #25Self-service

4Ease of manufacture

If conventional wire bonding is used for high current applications, then the process is simple and familiar, but the yield decreases due to wire breakage and contact resistance issues

Engineering Contradiction:

Improveprocess simplicityVSAvoidmanufacturing yield

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The conductive strip is formed as a composite structure comprising multiple wire-like conductors embedded within an insulating matrix material. This composite construction provides both the current carrying capacity of multiple wires and the mechanical strength and reliability of a unified structure, preventing the breakage issues that plague individual wire bonding.

Inventive Principle:

Principle #40Composite materials

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 reduces the likelihood of wire breakage and lowers costs by allowing conductive strips to efficiently carry higher currents in both single-chip and multi-chip packages, while also being compatible with conventional wire bonding processes for smaller currents.

Implementation Method 1

the conductive strip is applied with a bonding material thereon and then bonded to a bump on a die

Methodology Applied

Scientific EffectAdhesion: Adhesive

Data Source

PatentUS8097952B2Electronic package structure having conductive strip and method

Publication Date: 2012.01.17 RICHTEK TECH

AI summary

An electronic package structure and method use a conductive strip to bond die-to-die, die-to-lead, chip carrier-to-lead, or lead-to-lead. A conductive strip may carry greater current than a bonding wire, and thus may replace several bonding wires. The bonding of the conductive strip may be carried out by an SMT process, and thus requires lower cost than wire bonding processes. A conductive strip may be bonded to more than two dice or leads to save more bonding wires. A conductive strip is stronger than a bonding wire, and thus lowers the possibility of being broken.