Bonding Copper Conductive Elements Using Localized Joule Heating
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Solution Overview
Problem
Conventional bonding techniques using aluminum wires in electronics face limitations due to high ohmic power loss and rigidity issues when transitioning to copper or copper-based materials, which can cause cracks in pressure-sensitive components.
Innovation Solution
A method involving the use of an electric heating current to increase the temperature of a bonding section, combined with ultrasonic vibrations and a pressing force, to create a tight and direct bond between an electrically conductive element and a bonding surface, allowing for the successful bonding of rigid conductive elements without causing cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If copper or copper-based materials are used instead of aluminum wires, then ampacity and ohmic power loss are improved, but rigidity increases causing cracks in pressure-sensitive components
Solution Approach 1:
The patent applies parameter changes by heating the bonding section of the copper wire to an elevated temperature during the bonding process. This temperature increase reduces the mechanical strength and rigidity of the copper wire locally at the bonding section, allowing it to be pressed onto the bonding partner without causing cracks, while the rest of the wire maintains its high ampacity properties.
2Loss of energy
If the diameter of the bonding wire is increased, then ampacity is improved, but rigidity increases requiring higher pressing force and causing cracks
Solution Approach 1:
The patent uses parameter changes by applying heat to the bonding section of the wire during bonding. This allows thicker wires with better ampacity to be bonded at reduced mechanical strength, enabling adequate pressing force without causing cracks in the bonding partner.
Solution Approach 2:
The patent applies preliminary action by heating the bonding section before and during the bonding process. This pre-heating softens the wire material in advance, reducing its rigidity and allowing it to conform to the bonding surface without requiring excessive pressing force that would cause cracks.
3Strength
If pressing force is increased to bond rigid wires, then bonding strength is improved, but cracks occur in the bonding partner
Solution Approach 1:
The patent applies parameter changes by controlling the temperature of the bonding section during pressing. By maintaining an elevated temperature during the bonding process, the wire remains sufficiently soft to bond at lower pressing forces, achieving adequate bonding strength without causing cracks in the bonding partner.
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 method reduces mechanical stability and facilitates bonding of hard, copper-based elements or those with increased diameters to pressure-sensitive partners, minimizing the risk of cracks and achieving a high ampacity with low ohmic power loss.
Implementation Method 1
increasing a temperature of a bonding section of the electrically conductive element from an initial temperature to an increased temperature by passing an electric heating current through the bonding section
Implementation Method 2
introducing an ultrasonic vibration into the bonding section via the sonotrode
Data Source
Figure 1(a)~1(d)
Figure 2(a)~2(d)
Figure 3(a)~3(d)
AI summary
The invention relates to a method that includes bonding an electrically conductive element (1) to a bonding surface (2t) of a bonding partner (2) by: increasing a temperature of a bonding section (Is) of the electrically conductive element (1) from an initial temperature (T0) to an increased temperature (T1) by passing an electric heating current (IH) through the bonding section (Is); pressing the bonding section (Is) with a pressing force (F) against the bonding surface (2t) using a sonotrode (3) and introducing an ultrasonic vibration into the bonding section (Is) via the sonotrode (3) such that the increased temperature (T1) of the bonding section (Is), the ultrasonic signal in the bonding section (Is) and the pressing force (F) are simultaneously present and cause the formation of a tight and direct bond between the bonding section (Is) and the bonding surface (2t).