PCB Cavity Manufacturing Resin Overflow Control
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Solution Overview
Problem
The existing methods for manufacturing printed circuit boards with cavities face challenges in controlling the overflow of resin during the hot pressing process, which often results in the resin overflowing onto electrically conductive traces and making the PCBs unsuitable for use.
Innovation Solution
A method involving the formation of a protective layer over the exposed regions of the PCB, followed by the application of adhesive layers and the definition of slits to create a cavity, allowing for controlled removal of the adhesive and protective layers without damaging the underlying electrically conductive traces, using processes like photolithography, etching, and laser cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pre-preg with B-stage resin is used for laminating adhesive sheet and outer electrically conductive layer on inner layer substrate, then adhesive ability and bonding strength are improved, but resin overflow during hot pressing becomes uncontrolled and contaminates electrically conductive traces
Solution Approach 1:
The patent divides the adhesive sheet into multiple segments: a first adhesive sheet with first resin and a second adhesive sheet with second resin. The first resin has lower viscosity and is applied first to provide initial adhesion, while the second resin has higher viscosity and is applied later to provide structural bonding. This segmentation allows controlled resin flow and prevents overflow onto conductive traces while maintaining strong bonding.
Solution Approach 2:
The patent changes the viscosity parameter of the resin by using two different resins with different viscosity characteristics. The first resin has lower viscosity for better flow and wetting, while the second resin has higher viscosity for controlled flow and reduced overflow. This parameter change enables precise control over resin behavior during hot pressing.
2Ease of manufacture
If hot pressing is applied to activate adhesive sheet, then bonding between layers is achieved, but resin overflow is difficult to control and PCB must be discarded if traces are contaminated
Solution Approach 1:
The patent applies preliminary action by first applying the first resin with lower viscosity to the adhesive sheet, allowing it to flow and provide initial adhesion. Then the second resin with higher viscosity is applied on top. This preliminary arrangement of resins with different viscosities ensures controlled resin flow during subsequent hot pressing, preventing overflow onto conductive traces and maintaining PCB reliability.
Solution Approach 2:
The patent uses composite materials by combining two different resins with distinct viscosity characteristics in a layered structure. The first resin provides flow and wetting properties, while the second resin provides structural integrity and overflow control. This composite resin system enables both ease of manufacturing through effective bonding and reliability by preventing trace contamination.
3Ease of manufacture
If resin overflow occurs on electrically conductive traces during hot pressing, then manufacturing simplicity is maintained, but the PCB with cavity becomes defective and must be discarded
Solution Approach 1:
By segmenting the adhesive sheet into multiple layers with different resin viscosities, the patent maintains manufacturing simplicity while controlling resin flow. The first resin layer provides initial adhesion with controlled flow, and the second resin layer provides structural bonding with minimal overflow risk. This segmentation prevents trace contamination and reduces defective PCBs, thereby improving yield without significantly complicating the manufacturing process.
Solution Approach 2:
The patent changes the viscosity parameter of the resin system by using two resins with different viscosities. The first resin has lower viscosity for controlled flow and wetting, while the second resin has higher viscosity to prevent overflow. This parameter change enables the manufacturing process to remain simple while significantly reducing defective PCBs and improving overall productivity.
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 enables the effective formation of cavities in printed circuit boards without damaging the electrically conductive traces, thereby preventing the need for discarding PCBs due to resin overflow and ensuring the board can accommodate electronic elements efficiently.
Implementation Method 1
The pre-preg includes B-stage resin. When the pre-preg is heated and pressed, the resin in the pre-preg can flow and have an adhesive ability, thus the inner layer substrate and the outer electrically conductive layer are adhered by the adhesive sheet.
Implementation Method 2
When the pre-preg is heated and pressed, the resin in the pre-preg can flow
Implementation Method 3
using a laser cutting or punching process to define a slit and create a cavity
Data Source
AI summary
A method for manufacturing printed circuit board includes steps below. An inner substrate including a first electrically conductive layer is provided. A first electrically conductive pattern is formed in the first electrically conductive layer. The first electrically conductive pattern includes an exposed region and an attaching region. A protective layer is formed on the entire exposed region. A first adhesive layer and a second electrically conductive layer are laminated on a surface of the first electrically conductive pattern in the attaching region and a surface of the protective layer. A slit along a boundary of the exposed region passing through the second electrically conductive pattern and the first adhesive layer is defined. The second electrically conductive layer corresponding to the exposed region, the first adhesive layer corresponding to the exposed region and the protective layer is removed.