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What Are Flexible Printed Circuits (FPC) ?

joey / 2019-07-02

Flexible Printed Circuit Board, also known as "FPC ", it’s mainly composed of CU (Copperfoil), A(Adhesive) and PI (Kapton, Polyimide), which has many advantages that rigid printed circuit boards do not have.  such as space saving, weight reduction, and high flexibility,

  


Copper Foil


Flexibility in the copper comes from multiple factors. Of course the thinner the copper, the more flexible.  In addition to the thickness (or thinness), copper grain also affects flexibility. There are two common types of copper that are used in the PCB and flex circuit markets. Electro Deposited (ED) and Rolled Annealed (RA).

Differences between  Electrolysis Deposition Copper Foil and Roll Anneal Copper Foil


1.Electrolysis Deposition Copper Foil (ED copper):


Formation: Melt copper into dilute sulfuric acid, it becomes bluestone solution.

Through a high electric field, copper attach on the metal drum. With the rolling of a metal drum, thin copper foil finally formed.

Advantage: Low cost, ED copper has better conductivity than RA copper.

Shortage: Unsuitable for small lines; bad bending resistance.


2. Roll Anneal Copper Foil (RA copper):


Formation: Roll copper block many times, and then do the annealing treatment with high temperature. The shape of its crystal is a lamellar structure.

Advantage: Soft, smooth surface, suitable for flexible PCB and small lines.Shortage: high cost

The thickness is divided into 1/3OZ, 1/2 OZ,1OZ and so on. 1/3OZ is usually used

 

A (Adhesive)


Acrylic and epoxy thermosetting adhesive.

PI vs.PET: Which Is Right for you?


Not all anchoring Substrate are created equal, What’s the difference? When should you specify one rather than the other?

PI (Polyimide) is the preferred material for applications requiring a high degree of

dimensional stability after exposure to extreme temperatures (up to 300°C). In

addition, polyimide offers high resistance to chemicals, is lightweight and

flexible making it an ideal substrate for a wide variety of flexible electronics

applications.


PET(Polyester) is a lower cost option that provides similar characteristics

There are two kinds of thickness (1/2 MIL, 1 MIL)

 

What Is A Flexible Circuit overlay?



In the flexible printed circuit board manufacturing process, a flex circuit overlay (aka cover film) is used to encapsulate and protect the external circuitry of a flexible circuit board.

A flexible circuit overlay serves the exact same function as solder mask that is used on a rigid printed circuit board. The difference with a flex overlay is the needed element of flexibility and durability it provides to the flex PCB design.

 

The overlay consists of a solid sheet of polyimide with a layer of flexible adhesive that is then laminated under heat and pressurized to the circuit surfaces. The required component feature openings are mechanically created using drilling, routing, or laser cutting.

Typical overlay thickness is 0.001" polyimide with 0.001" of adhesive. Thicknesses of 0.0005" & 0.002" are available, but only used as needed to meet specific design requirements.

 

FPC production process


Single-sided FPC:



Prepare Base Material -(Drilling material)-Pattern Transfer-Developing Etching Stripping -AOI-Surface Treatment-Cutting -Coverlay Laminate-Hole Punching -Surface Treatment-Plating Sn/PB-Legend Screen Print-ET-Profile Punching-QC-QA-Packing

 

Double-sided FPC:

 


Prepare Base Material -Drilling -PTH-Surface Treatment-Pattern Transfer-Developing Etching Stripping -AOI-Surface Treatment -Coverlay Laminate-Hole Punching -Surface Treatment-Plating Sn/PB(NI/AU) -Legend Screen Print-ET-Profile Punching-QC-QA-Packing

 

 

 

As the premier expert in flexible circuit fabrication, PCBASTORE brings a unique combination of technology and quality that offers a competitive supply of flex circuits and rigid-flex circuits and other flexible circuit products.



To find out more, you can be reached at www.pcbastore.com or email us at: sales07@pcbastore.com