Multilayer Flexible PCB Manufacturing via Binder Layer Slits
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Solution Overview
Problem
The manufacturing process of multilayer flexible printed circuit boards (FPCBs) with varying layer thicknesses often results in quality issues due to a cliff-like structure between copper clad laminates, leading to poor product quality and peeling of dielectric layers during etching.
Innovation Solution
A method involving a first and second copper clad laminate, a binder layer, and forming slits and via holes to establish connections without a cliff-like structure, ensuring the excess portions are exposed and easily removable, thus preventing etchant seepage and maintaining layer integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a cliff-like structure is formed between different CCLs to create varying layer thicknesses, then the FPCB can have different numbers of layers in different areas (thick areas for higher circuit density, thin areas for higher flexibility), but the etchant can seep into the gap and react with dielectric layers causing peeling and poor product quality
Solution Approach 1:
The patent applies preliminary anti-action by forming a protective coating on the dielectric layers before the etching process. This coating prevents the etchant from seeping into the gap and reacting with the dielectric layers, thereby preventing peeling and quality issues before they can occur. The protective coating is applied in advance to counteract the potential harmful effect of etchant infiltration.
Solution Approach 2:
The patent introduces an intermediary substance (protective coating) between the etchant and the dielectric layers. This coating acts as a barrier that allows the etching process to proceed while preventing direct contact between the etchant and the dielectric layers, thus eliminating the harmful reaction that causes peeling.
2Reliability
If via holes are formed by drilling or laser ablation and electroless plating or electroplating is used, then electrical connection between layers is established, but copper lumps form on the exposed dielectric layer and pierce subsequent dry film causing poor quality products
Solution Approach 1:
The patent uses a protective coating as an intermediary layer during the plating process. This coating prevents copper ions from depositing on the dielectric layer and forming copper lumps, while still allowing the necessary electrical connections to be established in the via holes. The protective coating thus mediates between the plating solution and the dielectric layer to prevent defects.
Solution Approach 2:
The patent applies local quality by selectively removing the protective coating only in the via hole areas where electrical connections are needed, while maintaining the coating in other areas to prevent copper lump formation. This localized modification allows precise control over where plating occurs, ensuring high manufacturing precision.
3Manufacturing precision
If dry films are applied and exposed to develop patterns after plating, then circuit patterns are formed, but the etchant reacts with dielectric layers or copper layers causing peeling and poor quality
Solution Approach 1:
The protective coating serves as an intermediary that prevents etchant from reaching and reacting with the dielectric and copper layers during the pattern development process. This allows the dry film etching to proceed with high precision while the coating protects the underlying layers from damage, maintaining layer integrity throughout the manufacturing process.
Data Source
AI summary
A method for manufacturing a multilayer FPCB includes the steps of: providing a first copper clad laminate, a second copper clad laminate and a binder layer; defining an opening on the binder layer; defining a first slit on the first copper clad laminate; laminating the first copper clad laminate, the binder layer and the second copper clad laminate; defining a via hole for establishing electric connection between the first copper clad laminate and the second copper clad laminate; cutting the first copper clad laminate, the binder layer and the second copper clad laminate thereby forming a multilayer flexible printed circuit board having different numbers of layers in different areas.