Flex Circuit Traces via Dry Milling and Protective Coating
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Solution Overview
Problem
The manufacturing of flexible circuits faces challenges due to the formation of oxide layers and contaminants on conductive traces, which hinder effective electrical bonding and physical connections, especially with aluminum traces, leading to issues like poor wetting and residual chemical interference.
Innovation Solution
A method involving a laminated substrate with a conductive layer, adhesive layer, and support layer, where conductive traces are formed by dry milling, and a protective coating is applied to prevent oxidation, followed by soldering components using a reflow oven and attaching other components via ultrasonic welding, eliminating the need for flux and reducing chemical contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chemical etching or printing processes are used to form conductive traces, then the manufacturing process is established, but residual chemicals and contaminants remain on the conductive traces
Solution Approach 1:
The patent replaces chemical etching and printing processes with a mechanical dry milling process to form conductive traces. This substitution eliminates the use of chemical solvents and etchants, thereby preventing residual chemicals and contaminants from remaining on the conductive traces while still achieving precise trace formation.
Solution Approach 2:
The patent performs the dry milling process in a vacuum environment rather than in air or chemical baths. This inert environment prevents oxidation of the conductive trace surfaces and eliminates contamination from atmospheric chemicals, ensuring clean conductive traces without residual contaminants.
2Reliability
If flux process is used to clean conductive traces before soldering, then electrical bonding effectiveness is improved, but residual chemicals are left on the surfaces
Solution Approach 1:
The patent applies a protective coating to the conductive traces before any subsequent processing steps. This preliminary protective action prevents oxide formation and contamination throughout the manufacturing process, eliminating the need for flux-based cleaning before soldering while ensuring the surfaces remain ready for optimal electrical bonding.
Solution Approach 2:
The patent replaces the chemical flux cleaning process with mechanical dry milling in a vacuum environment. This mechanical approach removes materials without leaving chemical residues, and the vacuum environment prevents oxide formation, thereby achieving clean surfaces suitable for soldering without introducing flux-related residual chemicals.
3Productivity
If aluminum conductive traces are exposed to air during manufacturing, then the manufacturing process proceeds, but oxide layers form on the trace surfaces
Solution Approach 1:
The patent conducts the dry milling process in a vacuum environment, which serves as an inert atmosphere that prevents aluminum oxidation. This allows the manufacturing process to proceed efficiently while eliminating oxide layer formation on the conductive trace surfaces, maintaining both productivity and trace quality.
Solution Approach 2:
The patent forms the conductive traces mechanically in a vacuum environment before any subsequent air-exposed processes. This preliminary formation in an inert environment prevents oxide layers from forming in the first place, eliminating the need for later flux-based oxide removal and ensuring clean surfaces for bonding.
4Ease of manufacture
If soldering is performed on aluminum traces with oxide layers, then component attachment is achieved, but wetting is poor and solder forms balls
Solution Approach 1:
The patent applies a protective coating to the conductive traces and performs dry milling in a vacuum environment before soldering. These preliminary actions prevent oxide layer formation and maintain clean, oxide-free aluminum surfaces, enabling proper solder wetting and reliable electrical connections without the solder balling issue that occurs with oxidized surfaces.
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 ensures clean and reliable electrical and mechanical connections, reduces contamination, and allows for the use of different materials, enhancing the quality and longevity of flexible circuits by avoiding chemical etching-related issues and residual contaminants.
Implementation Method 1
heating the solder material to remove the protective coating from the first connection point
Implementation Method 2
heating the solder material to... connect the first component to one of the conductive traces
Implementation Method 3
forming conductive traces by removing selected portions of the conductive layer and the adhesive layer by dry milling the laminated substrate
Implementation Method 4
applying a protective coating to the conductive traces
Implementation Method 5
heating the solder material to remove the protective coating... heating may remove oxidation and/or contaminants from portions of the conductive traces
Data Source
AI summary
A method of manufacturing a flexible circuit comprises providing a laminated substrate that includes a conductive layer, an adhesive layer, and a support layer. The method comprises forming conductive traces by removing selected portions of the conductive layer and the adhesive layer by dry milling the laminated substrate. The method comprises applying a protective coating to the conductive traces. The method comprises dispensing a solder material on the protective coating at a first connection point and arranging a first component at the first connection point. The method comprises heating the solder material to remove the protective coating from the first connection point and to connect the first component to one of the conductive traces at the first connection point. The method comprises attaching a second component to the conductive layer at a second connection point that is free of the protective coating by a process other than soldering.