Bonding Metallic Surfaces with Sacrificial Dielectric Layer
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Solution Overview
Problem
The durability of electrical bonds between metallic surfaces can be compromised by oxidation, especially in high-temperature and oxygen-rich environments, leading to premature failure, particularly when copper is involved, and the use of precious metal protective layers is costly and inefficient.
Innovation Solution
Applying an inorganic, dielectric protective layer to the metallic surface, which is then destroyed during bonding by applying a pressing force, allowing for the formation of an electrically conductive bond between the metallic surface and the contact conductor, thereby preventing oxidation and enhancing bond durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a precious metal protective layer is applied to prevent oxidation, then the metallic surface is protected from oxidation and other chemical changes, but material costs increase significantly
Solution Approach 1:
The patent replaces expensive precious metal protective layers with a cheap, sacrificial organic protective layer that can be easily removed. This layer serves its protective function temporarily during storage and handling, then is deliberately destroyed during the bonding process to expose the fresh metallic surface for bonding, eliminating the need for costly precious metals.
Solution Approach 2:
The patent extracts the protective function from the final bond structure by using a temporary protective layer that is completely removed during bonding. Instead of incorporating a permanent precious metal layer into the final product, the protection is provided only when needed and then discarded, eliminating unnecessary material costs.
2Reliability
If a precious metal protective layer is applied to prevent oxidation, then the metallic surface is protected, but the protective layer acts as a lubricant during bonding, detriming bond quality
Solution Approach 1:
The organic protective layer is designed to be temporarily functional (providing protection) and then sacrificial (removed during bonding). This eliminates the problem of precious metal layers acting as lubricants during bonding, as the organic layer is completely destroyed and removed, leaving no residual material to interfere with bond quality.
Solution Approach 2:
The patent converts the potential harm of having a protective layer present during bonding into a benefit by designing a protective layer that is specifically engineered to be easily destroyed and removed. The destruction of the organic layer during bonding (through heating, mechanical action, or chemical treatment) actually benefits the process by automatically clearing the bonding interface of protective material, ensuring optimal bond quality.
3Reliability
If a precious metal protective layer is applied to prevent oxidation, then the metallic surface is protected, but additional fabrication work is required, increasing expense
Solution Approach 1:
The organic protective layer serves multiple functions: it protects the metallic surface during storage and handling, it can be patterned to define bonding areas, and it is automatically removed during the bonding process itself. This multi-functionality eliminates the need for separate removal steps that would be required with precious metal layers, simplifying the overall fabrication process.
Solution Approach 2:
The protective layer remains in place continuously during storage and handling, providing ongoing protection without interruption. During bonding, its removal is integrated into the bonding process itself rather than requiring a separate step, maintaining continuous productive action throughout the fabrication sequence.
4Duration of action of stationary object
If the metallic surface is exposed to oxygenated atmosphere at high temperatures, then oxidation occurs shortening bond life, but protecting with precious metals increases cost
Solution Approach 1:
The organic protective layer is applied in advance to the metallic surface before any oxidation can occur. This preliminary protection allows the component to be stored and handled in normal atmospheric conditions without risk of oxidation, preserving the metallic surface for when bonding actually occurs, thereby extending bond life without requiring precious metals.
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 creates a durable electrically conductive bond that can withstand higher temperatures and reduces material costs by avoiding the use of precious metals, while maintaining bond quality and reliability.
Implementation Method 1
a portion of the contact conductor is pressed by means of a pressing force applied top-down to the surface zone to the protective layer and bond so that the protective layer topping the surface zone is destroyed
Implementation Method 2
the contact conductor oscillates roughly parallel to the metallic surface, for example due to the effect of an ultrasonic bondhead
Data Source
AI summary
The invention relates to a method for fabricating a bond by providing a body including a metallic surface provided with an inorganic, dielectric protective layer. The protective layer covers at least one surface zone of the metallic surface in which the metallic surface is to be electrically conductive bonded to a contact conductor. To fabricate the bond, a portion of a provided contact conductor above the surface zone is pressed on to the protective layer and the body so that the protective layer is destroyed above the surface zone in achieving an electrically conductive bond between the metallic surface and the contact conductor.