Laser Ablation for Wirebonding on As-Cast Heat Sink Surfaces
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Solution Overview
Problem
Current wire bonding processes on circuit assemblies, particularly between heat sinks and printed circuit boards, face high failure rates due to contamination and surface imperfections, and are costly due to the need for expensive diamond milling processes.
Innovation Solution
A surface treatment process using laser etching to clean and smooth the surface of heat sinks, involving two steps: material removal and polishing, which eliminates contamination and oxidation layers without the need for post-casting treatments, enabling robust wire bonding connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If diamond milling process is used to polish the surface, then surface finish quality is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces the mechanical diamond milling process with a laser-based ablation and polishing process. The laser system uses optical energy to remove material and smooth surfaces, eliminating the need for mechanical contact and expensive diamond tools while achieving comparable or superior surface finish quality for wire bonding applications
Solution Approach 2:
The patent changes the fundamental processing parameter from mechanical force (diamond milling) to thermal energy (laser ablation). By controlling laser power, pulse duration, and scanning speed, the process achieves precise material removal and surface smoothing at lower cost while maintaining high manufacturing precision
2Ease of manufacture
If traditional wire bonding process is used on as-cast surfaces, then manufacturing simplicity is maintained, but bonding reliability deteriorates due to contamination and surface imperfections
Solution Approach 1:
The patent applies preliminary laser ablation and polishing treatments to the as-cast surface before wire bonding. This pre-treatment removes contamination, oxidation layers, and surface imperfections that would otherwise cause bonding failures, thereby improving bonding reliability while maintaining the simplicity of the overall manufacturing process
Solution Approach 2:
The patent replaces traditional mechanical surface preparation methods (which would add complexity) with a laser-based system that can be integrated into existing manufacturing lines. The laser process simultaneously cleans, ablates, and polishes the surface in one setup, improving reliability without significantly complicating the manufacturing process
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 process significantly reduces failure modes and costs by providing a consistent, robust bonding interface, eliminating the need for expensive post-processing treatments like diamond milling, and ensuring a strong, reliable wire bonding connection.
Implementation Method 1
the surface of the heatsink has been etched using a laser... the first step is a laser etch ablation process where material is removed
Implementation Method 2
the second step is a second laser etch to clean and smooth the surface
Data Source
AI summary
A method of removing material from a surface, which includes the steps of providing a base layer, at least one layer attached to the base layer, an intermediate finish surface, and a bonding interface surface. The intermediate finish surface is formed by removing the at least one layer and a portion of the base layer during a material removal process. The bonding interface surface is formed by a polishing process applied to the intermediate finish surface. There is an oxidation layer which is part of the base layer, as well as a mold release layer and a contamination layer, both of which are part of the at least one layer. The material removal process involves laser etching the at least one layer to create the intermediate finish surface, and the polishing process includes applying a second laser etching to the intermediate finish surface, forming the bonding interface surface.