Epoxy-Silicone Peelable Mask for Rigid-Flex PCBs
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Solution Overview
Problem
Existing methods for manufacturing rigid-flex printed circuit boards (PCBs) face challenges in creating a reliable peelable mask that can withstand harsh conditions and prevent damage to conductive patterns, particularly due to residue and contamination issues during the fabrication process.
Innovation Solution
A method involving the application of an epoxy-silicone hybrid paste as a peelable mask on the flexible circuit substrate, using screen printing and controlled curing conditions to achieve a mask with heat resistance, chemical resistance, and a contact angle greater than 20 degrees, ensuring easy removal and protection of conductive patterns during the buildup of the rigid circuit substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional peelable ink or silicone-based paste is used as a protect layer, then the protect layer can be removed after processing, but residue remains after removal under harsh chemical and physical conditions, causing contamination and increased defect rate
Solution Approach 1:
The patent modifies the chemical composition parameters of the paste by using epoxy-silicone hybrid materials with specific ratios, and controls curing parameters (temperature and time) to achieve a mask that resists harsh chemicals while remaining peelable, thereby eliminating residue and contamination issues
Solution Approach 2:
The patent employs a composite paste formulation combining epoxy and silicone materials, which synergistically provide both the necessary adhesion and chemical resistance during processing, and the peelable property after processing, resolving the contradiction between durability and removability
2Strength
If a protect layer is formed to withstand severe conditions during electroplating or reflow process, then the conductive patterns are protected from damage, but the protect layer becomes difficult to remove cleanly without leaving residue
Solution Approach 1:
The patent optimizes the curing parameters (temperature and time) and paste composition to create a mask with controlled cross-linking density, achieving sufficient heat and chemical resistance during processing while maintaining ease of removal afterward by controlling the degree of curing
3Reliability
If the contact angle of the peelable mask is not optimized, then the mask may not provide adequate protection or may be difficult to remove, but optimizing the contact angle requires precise control of paste composition and curing conditions
Solution Approach 1:
The patent establishes specific ranges for paste composition ratios and curing parameters that directly control the contact angle, simplifying the optimization process by providing predetermined parameter ranges that achieve the desired balance between protection effectiveness and ease of removal
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
The solution provides a reliable and durable peelable mask that effectively protects conductive patterns from damage during extreme temperature and chemical exposure, reducing defect rates and improving the reliability of the rigid-flex PCB manufacturing process.
Implementation Method 1
curing the paste
Implementation Method 2
a peelable mask with heat resistance, chemical resistance and a contact angle greater than 20 degrees
Implementation Method 3
a peelable mask with heat resistance, chemical resistance and a contact angle greater than 20 degrees
Implementation Method 4
printing a paste containing epoxy-silicone hybrid materials onto the conductive pattern via a screen printing method under predetermined conditions
Data Source
AI summary
The invention relates to a method of fabricating a flexible-rigid PCB which includes a flexible circuit substrate and a rigid circuit substrate. The flexible circuit substrate defines a rigid region and an exposed region and has a conductive pattern, such as conductive traces, formed on the exposed region. The method includes the steps of providing the flexible circuit substrate; printing a paste containing epoxy-silicone hybrid materials onto the conductive pattern; curing the paste; and building up the rigid circuit substrate on the rigid region of the flexible circuit substrate. Particularly, the paste having a specific composition is subjected to predetermined conditions of temperature and time in order to transform the paste into a peelable mask with heat resistance, chemical resistance and a contact angle greater than 20 degrees.