Tensioned Substrate Coating for Independent Resin Thickness Control
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Solution Overview
Problem
Existing methods for fabricating prepregs for printed circuit boards face challenges in independently controlling the thickness of resin layers on opposite surfaces while maintaining high productivity and effectively removing air bubbles, often resulting in insufficient impregnation and trapped bubbles due to simultaneous coating processes.
Innovation Solution
A process and device that involves feeding a substrate sheet with tension, bending it at specific points to apply resin fluid on one surface, then the other, using separate dispensers with coating heads that press against the substrate to ensure thorough impregnation and bubble removal, allowing for independent control of resin layer thickness and high-speed feeding without bubble entrapment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the opposite surfaces of the substrate sheet are coated simultaneously with resin fluid, then the coating process can be completed efficiently and continuously, but it becomes difficult to independently control the thicknesses of resin layers on the opposite surfaces
Solution Approach 1:
The patent divides the coating process into two separate sequential steps: first coating one surface of the substrate sheet with resin fluid, then coating the opposite surface. This segmentation allows independent control of resin layer thickness on each surface while maintaining continuous production, resolving the contradiction between coating efficiency and thickness control precision.
2Manufacturing precision
If the opposite surfaces of the substrate sheet are coated one by one, then the thicknesses of resin layers can be controlled independently with high accuracy, but insufficient impregnation and remaining air bubbles occur inside the resin fluid
Solution Approach 1:
The patent applies preliminary action by placing a release sheet on the substrate sheet before coating, and by controlling the coating sequence and pressure application. The release sheet prevents resin fluid from penetrating through to the opposite surface during the first coating step, ensuring proper impregnation without air bubbles. This preliminary preparation enables both independent thickness control and high impregnation quality.
3Reliability
If the substrate sheet is heated during the coating process to remove air bubbles, then impregnation of the resin fluid is improved, but the device becomes complicated due to the requirement of a heater
Solution Approach 1:
The patent extracts the heating function from the coating process by using a release sheet that enables effective impregnation and air bubble removal through mechanical means (coating pressure and sequence control) alone. This eliminates the need for additional heating equipment, maintaining high impregnation quality while simplifying the device structure.
4Reliability
If the feeding speed of the substrate sheet is reduced to allow sufficient impregnation, then air bubbles are removed from the resin fluid, but the productivity of the prepreg fabrication is lowered
Solution Approach 1:
The patent uses a release sheet as a preliminary action to enable effective resin fluid impregnation and air bubble removal at high feeding speeds. The release sheet controls resin fluid penetration and facilitates bubble escape during the coating process, eliminating the need to reduce feeding speed and thereby maintaining high productivity while ensuring reliable bubble removal.
Data Source
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Figure 2(a)~2(c)
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AI summary
The present invention has been aimed to propose a process and a device of fabricating a prepreg for a printed circuit board which are capable of controlling respective thicknesses of resin layers on the opposite surfaces of a resultant prepreg, removing air bubbles from the resultant prepreg, and improving productivity. The present invention is a process of resin-coating the opposite surfaces of an elongated substrate sheet 3. The process includes the steps of: feeding the substrate sheet 3 while tensioning the same in a feeding direction along the length of the substrate sheet 3; coating, by the coating head 2 of the first dispenser 1a, one surface of the substrate sheet 3 with the fluid resin 4 while pressing against the one surface to bend the substrate sheet 3; and subsequently coating, by the coating head 2 of the second dispenser 1b, the other surface of the substrate sheet 3 with the fluid resin 4 while pressing against the other surface to bend the substrate sheet 3. A die coater and a roll coater can be used as the first dispenser 1a and the second dispenser 1b.