What is flexible circuit board?

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1.Flexible circuit board can arbitrary blending and be assembled in 3D room with slight thickness and weight.

2. Base material

2.1 Copper Clad Laminate

Copper + adhesive + Dielectric Substrate / copper + Dielectric Substrate (price will be more higher and it will not be the first choose except for special requirement)

2.1.1 Copper Foil

According to the difference of material, it can be divided into Rolled Anneal Copper Foil(RA) and Electro Deposited Copper Foil (ED). However, RA will be used more because which’smechanic properties and flexibility better than ED. For copper thickness of RA, it can beseparated into 1/2 oz, 1oz and 2oz etc. But for the ED, it can be divided into 1/3 oz,1/2oz, 1oz and 2oz etc. In general, we will use 1oz.

2.1.2 Substrate

Two films here: PI (Polymide) and PET (Polyster) Film.

Polymide (Kapton, apical and U-BE):

A: Used in CCL without adhesive and coverlay.

B: Used where dimension stability is critical.

C: Used in high temperature application

D: High moisture absorption.

E: Expensive than PET

F: Thickness of 1mil and 2mil can be chosen.


A: Used where the dielectric also polyster

B: Used where no soldering is needed

2.1.3 Adhesive

Two adhesives here: Acrylic and Epoxy.


A: Widely used adhesive system

B: Generally lower cost than acrylic

C: Able to stand wave soldering

D: Good in high temperature for long period of (400 to 450F)

E: Thickness range is from 0.4mil to 1mil. But 1mil was the most popular


A: Used in demanding temperature requirement application

B: Excellent adhesion

2.2 The Cover lay

The thickness range is from 0.5 to 1.4mil.

Flexible PCB/PCBA supplier-Shenzhen Sienta Industry

2.3 Stiffener

Part of area have to laminate a hard material to solder components or convenient to assembly. It is called stiffener. We usually use PI or PET or Epoxy (for example FR4) as stiffened material. And Pressure sensitive adhesive is widely used for PET or Epoxy stiffener while lamination, but for PI stiffener, we have to use thermosetting adhesive instead.

2.4 Ink

Three kinds of ink here: Solder Mask, Legend and Silver ink.

And they can also divided into UV, UV Cure and Thermal post cure.

2.5 Surface finishing

OSP, HASL, Immersion Sn/Pb and Ni/Au /Ag, Plating Ni/Au

2.6 Two sided adhesive

Adhesive with substrate

Adhesive without substrate

3. Unit in common use


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