Flexible Circuit Microvia Structure Using Conductive Paste
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Solution Overview
Problem
Conventional flexible circuit board via structures are inadequate for modern industries due to limited conductive contact surface area and increased impedance as conductive traces and spacing distances become smaller, and they feature thick electroplated copper layers that are not suitable for modern applications.
Innovation Solution
A microvia structure is created by forming through holes in conductive layers with exposed zones and filling them with a conductive paste layer, which covers and electrically contacts the exposed zones, thereby enlarging the conductive contact surface area and ensuring conduction reliability, without the need for electroplating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electroplating is used to form via structures, then conductive traces can be connected through the board, but the electroplated copper layer becomes too thick and impedance increases
Solution Approach 1:
The patent changes the material parameter from electroplated copper to conductive paste, and changes the deposition method parameter from electroplating to screen printing. This results in a thinner conductive layer (0.003-0.008mm) compared to conventional electroplating, thereby reducing impedance while maintaining conduction reliability
Solution Approach 2:
The patent uses conductive paste as a temporary conductive medium that can be applied and removed more easily than electroplated copper. The conductive paste serves its purpose during the via formation process and can be cleaned away, avoiding the permanent impedance issue of thick electroplated layers
2Productivity
If conductive traces and spacing distances are reduced for modern circuit requirements, then circuit density increases, but the via structure becomes inadequate and conduction reliability decreases
Solution Approach 1:
The patent applies local quality by creating exposed zones with specific properties (clean, oxide-free copper surface) at the via locations where conduction is needed. The conductive paste is selectively applied only to these exposed zones, ensuring reliable conduction in the critical via areas while allowing reduced trace dimensions elsewhere to achieve higher circuit density
Solution Approach 2:
The patent performs preliminary actions by forming the exposed zones and applying protective layers before the conductive paste is applied. The protective layers prevent oxidation of the copper surfaces in advance, ensuring that when the conductive paste is applied, it bonds to a clean, reliable conductive surface, maintaining conduction reliability even with reduced spacing
3Reliability
If conventional via structures are used with thick electroplated copper, then conduction is established, but the manufacturing process becomes complex and time-consuming
Solution Approach 1:
The patent replaces the electrochemical system of electroplating with a mechanical/screen printing system for applying conductive paste. This substitution simplifies the manufacturing process by eliminating the complex electroplating equipment, chemical baths, and control systems required, while still achieving reliable conduction through the via structures
Solution Approach 2:
The patent extracts the essential function of creating a conductive path through the via from the complex electroplating process. By using conductive paste applied through screen printing, it separates the conduction function from the thick copper deposition, achieving reliable conduction with a simpler, more direct manufacturing approach
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 simplifies the manufacturing process, reduces circuit impedance, and enhances conduction reliability by increasing the conductive contact surface area, making it suitable for modern applications.
Implementation Method 1
a conductive paste layer is filled in the second through hole of the second conductive layer, the dielectric layer through hole of the dielectric layer, and the first through hole of the first conductive layer so as to cover and electrically contact the first exposed zone of the first conductive layer and the second exposed zone of the second conductive layer
Data Source
AI summary
Disclosed urea microvia structure of a flexible circuit board and a manufacturing method thereof. A first through hole is formed in a first conductive layer of a flexible circuit board and a first exposed zone is defined. A second conductive layer includes a second through hole formed therein and defines a second exposed zone. A dielectric layer includes a dielectric layer through hole corresponding to the second through hole of the second conductive layer. A conductive paste layer is filled in the second through hole of the second conductive layer, the dielectric layer through hole of the dielectric layer, and the first through hole of the first conductive layer in such a way that the conductive paste layer covers and electrically contacts the first exposed zone of the first conductive layer and the second exposed zone of the second conductive layer.