FPC Prototype in Humanized Way

Quick FPC, Rigid-flex PCB prototype and PCB Assembly

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FPCway: Specialized manufacturer of flexible printed circuit boards and rigid-flexible printed circuits
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Evolution of the Flex Printed Circuit Board
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Flexible PCB vs Rigid PCB
Development of Flexible printed circuit board (FPC) market
Traditional Manufacture Engineering of FPC Substrate
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Flex PCB and the Manufacturing
About Flex PCB design
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How to Select the Appropriate FPC Materials?
The Differences In Rigid PCB, Flex PCB and Rigid-Flex PCB
Flex-Rigid PCB Design Guidelines
Beneficials for Polyimide Flex PCB Boards
About Stiffener on Flex PCB FPC circuit Boards
PCB Surface Finish Comparison
Copper Thickness for FPC Boards
Interconnect Solutions for Flexible Printed Circuits and Etched Foil Heaters
Advantages and Disadvantages of Rigid-Flex PCB
About FPC Plating Process
About EMI shield design for Flex Printed Circuit Board
PCB Assembly Blog
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About PCB Assembly
QFP and BGA and the Development Trend in PCB assembly
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About Flex PCB Assembly
Manual Soldering in SMT Assembly Manufacturing Process
BGA Components and BGA Assembly
Quick Understanding for PCB Assembly Process
About SMT Assembly (Surface Mount Technology)
About THT Assembly (Through-Hole Technology)
About Reflow Soldering
PCB Assembly Inspections and Tests
Panel Requirements for PCB Assembly
About SMT (Surface Mount Technology)
FPC Research Blog
Preparation of FPC based on ultrasonic spraying method_4_Experimental Results
Preparation of FPC based on ultrasonic spraying method_3_Experimental Procedure
Preparation of FPC based on ultrasonic spraying method_2_Experimental Platform and Principle
Preparation of FPC based on ultrasonic spraying method_1_abstract
Research on Layout Design Method of Ultra-thin FPC_4_Analysis of Layout Design Methods
Research on Layout Design Method of Ultra-thin FPC_3_Analysis of Layout Design Methods
Research on Layout Design Method of Ultra-thin FPC_2_Analysis of Layout Design Methods
Research on Layout Design Method of Ultra-thin FPC_1_introduction
Research progress on polyimide FPC_2_the field of FPC
Research progress on polyimide FPC_1_Introduction
Analysis of Vibration Characteristics of FPCBs _4_Summary
Analysis of Vibration Characteristics of FPCBs _3_Finite Element Analysis
Analysis of Vibration Characteristics of FPCBs _2_Theory of Vibration Analysis
Analysis of Vibration Characteristics of FPCBs Under Random Vibration_1_Introduction
Design Methods for FPCBs_5_Practical Application
Design Methods for FPCBs_4_Electrical Circuit Design and Examples
Design Methods for FPCBs_3_Structure Design Method and Examples
Design Methods for FPCBs_2_Component Selection Methodology and Examples.
Research on Design Methods for FPCBs
Application of MPW technique for FPCBs _4_Summary
Application of MPW technique for FPCBs_3_Experimental results
Application of MPW technique for FPCBs_2_Experimental setup
Application of MPW technique for FPCBs_1_Principle of MPW
Application of FPCB in PC motherboards_4_ Results and discussion
Application of FPCB in PC motherboards_3_ Numerical analysis
Application of FPCB in PC_2_ Experimentation
Application of FPCB in PC motherboards
A Bus Planning Algorithm for FPC Design _4_Experimental result
A Bus Planning Algorithm for FPC Design _3_Proposed Algorithm
A Bus Planning Algorithm for FPC Design _2_Preliminaries
A Bus Planning Algorithm for FPC Design _1_Introduction

Two primary options for encapsulating the external circuit layers of a flex circuit: polyimide coverlay and flexible liquid photoimageable (LPI) solder mask. The two materials have very different capabilities and requirements. 


Of the two, polyimide coverlay is the most commonly used and preferred solution throughout the industry. It provides a much more robust and durable solution with very good flexibility and a high dielectric. 


Flexible LPI solder mask is essentially the same formula (with the addition of a flex agent) that has the same capabilities and is applied in the same manner as on rigid circuit boards.


Coverlay Materials & Construction 


Coverlay is a two part sheet form material comprised of a layer of polyimide and a layer of either epoxy or acrylic based flexible adhesive. The function of the adhesive is both to bond the polyimide to the flex circuit and to encapsulate the circuitry. 


Coverlays are then aligned and laminated to the circuit surface under both heat and pressure. 


Coverlay is available in variety of combinations of both film and adhesive thicknesses, the most common being a 0.5 mil film with a 0.75 mil adhesive.  


Common Coverlay Configurations 


The specific film and adhesive combination is typically a function of the following items: 


1. Minimum bend requirements. Thinner coverlay may be required to meet tight bend requirements 

2. Copper weight of the external layers. Min. of 1 mil of adhesive is required per OZ of copper to ensure complete encapsulation E: 1 OZ Copper = 1 mil adhesive 

3. Cost 

4. Dielectric Withstanding Voltage (rare) 


SMT & PTH Feature Openings 


As a sheet form material the plated through hole (PTH) and surface mount technology (SMT) etc. features are machined into the coverlay using one or more of the following methods: drilling, routing, laser cutting, knife cutting, or punch & die sets. The exact method(s) is dependent upon the feature shape, size, complexity, and quantity of parts being manufactured.


This in-turn imposes additional considerations beyond that of Flex LPI: 


Larger min. annular ring to exposed feature requirements. Allows for material and manufacturing tolerances and potential adhesive squeeze out during lamination. 


Larger min. web thickness between adjacent features. Prevents easily damaged thin sections/webs and allows for sufficient adhesive to ensure proper lamination and circuit encapsulation 


Isolated “island” type features not available. Would fall out of layer after machining. 


In flexible PCB designs with higher density SMT & PTH features and if the design allows, it is required to combine multiple feature openings into larger “ganged” openings to accommodate the above items. 


Coverlay/Flex LPI Design Combinations 


Some flex circuit designs due to their density, complexity, and/or component requirements may require the use of both materials. Both are selectively applied to specific areas of the part and provide benefits of both materials within one design. The manufacturing files are created to ensure that the two materials overlap within the rigidized area(s). This results in a complete encapsulation of the circuitry without the creation of mechanical bend stress concentrators in the flexible areas. If this were allowed the reliability of the part may be compromised. While this methodology adds some cost, the design may mandate it and/or the benefits outweigh the added cost. 


Two common solder mask design configurations are to either apply flex LPI in rigidized component areas and polyimide coverlay in the flexible sections or to add selective webs of solder mask in ganged coverlay openings. 


Additional Considerations 


Designs that have one or more of the following may require the use of coverlay throughout in specific areas or layers: 

1. ZIF finger area Polyimide stiffener(s) 

2. FR4 component area rigidizing stiffener(s) 

3. Silver Ink Shield Layer(s) 

4. EMI & RF Shielding film(s) 

5. Pressure Sensitive Adhesives (PSA) or 3M adhesive or Tesa adhesive


The materials above may not sufficiently adhere to LPI and pass IPC quality control requirements.

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  • Based in Shenzhen China, FPCway is professional at Flex PCB,
    Rigid-flex PCB and PCB assembly services
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