Metal Covered Polyimide Composite for Flexible Laminates
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Solution Overview
Problem
Conventional methods fail to effectively prevent peeling at the interface between copper layers and tin plating in non-adhesive flexible laminates, primarily due to Kirkendall voids generated during the electroplating process, which disrupts the adhesion and leads to defects in electronic components like COF (Chip on Film).
Innovation Solution
A metal covered polyimide composite is developed with a tie-coat layer and a metal seed layer formed on a polyimide film using electroless plating or a drying method, followed by a copper or copper alloy layer formed through electroplating, where the electroplating process is optimized by dividing the plating zone into fewer sections to reduce the number of electroplating baths and minimize Kirkendall voids, using a drum-based electroplating apparatus with adjustable anodes to control current density and flow velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple electroplating baths are used to form copper layers, then the copper layer thickness and conductivity are improved, but the number of Kirkendall voids increases due to multiple plating boundaries
Solution Approach 1:
The patent combines multiple electroplating operations into a single electroplating bath by using a through-hole structure that allows the plating solution to flow through the entire copper layer being formed. This eliminates the need for multiple separate plating baths and their associated boundaries, thereby reducing Kirkendall voids while still achieving the desired copper layer thickness and uniformity.
Solution Approach 2:
The patent introduces a vertical dimension to the electroplating process by creating a through-hole structure that extends through the copper layer. The plating solution flows vertically through this hole, allowing electroplating to occur simultaneously at multiple levels within a single bath, thus eliminating the need for sequential plating operations that create boundaries.
2Strength
If plasma treatment is performed to improve surface roughness and adhesion, then the adhesion strength between metal layer and polyimide film is improved, but the manufacturing process complexity increases
Solution Approach 1:
The patent performs plasma treatment on the polyimide film surface before forming the metal layers. This preliminary surface modification creates a rougher surface that enhances adhesion strength, while the effect persists through subsequent manufacturing steps, reducing the need for additional adhesion-promoting treatments later in the process.
3Reliability
If the number of electroplating baths is reduced to minimize Kirkendall voids, then the adhesion strength is improved, but the manufacturing precision of copper layer thickness may be compromised
Solution Approach 1:
The patent segments the electroplating process spatially by creating a through-hole structure that divides the copper layer into regions accessible to the plating solution. This segmentation allows uniform thickness control throughout the layer even when using a single plating bath, as the solution can reach all areas simultaneously through the hole structure.
Solution Approach 2:
The patent implements a feedback mechanism where the through-hole structure allows the plating solution to flow through the developing copper layer, providing real-time feedback on plating progress and uniformity. This enables precise control of copper layer thickness while using fewer plating baths, maintaining manufacturing precision without compromising adhesion strength.
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 significantly reduces Kirkendall voids and improves adhesion strength by forming a uniform copper layer with fewer boundaries, thereby preventing peeling and enhancing the reliability of non-adhesive flexible laminates used in electronic components.
Implementation Method 1
a tie-coat layer and a metal seed layer are formed on a surface of a polyimide film by electroless plating or a drying method
Implementation Method 2
forming a metal layer film to become the conductor layer of the circuit board by way of electroplating
Data Source
AI summary
A metal covered polyimide composite comprising a tie-coat layer and a metal seed layer formed on a surface of a polyimide film by electroless plating or a drying method is provided. A copper layer or a copper alloy layer is formed thereon by electroplating. The copper plated layer or copper alloy plated layer includes three layers to one layer of the copper layer or copper alloy layer. The metal covered polyimide composite effectively prevents peeling in a non-adhesive flexible laminate (especially a two-layer flexible laminate), and more particularly, effectively inhibits peeling from the interface of a copper layer and tin plating. A method of producing the composite and apparatus for producing the composite are also provided.