Dupont FPC 4 Layer Flex Pcb 0.5Oz-20Oz Copper Quick Turn Flex Circuits

Dupont FPC 4 layer flex pcb stackup circuit board

Application field: Handheld terminal products such as mobile phones, three defense devices, etc

Material: DuPont adhesive free rolling material

Plate thickness: 0.15mm

Process capability: impedance, high bending

Basic knowledge of flexible circuit boards

Introduction to FPC

FPC: Full English Pinyin Flexible Printed Circuit, which means flexible printed circuit board in Chinese, abbreviated as flexible board. It is a conductive circuit pattern made by using optical imaging pattern transfer and etching techniques on a flexible substrate surface. The surface and inner layers of double-sided and multi-layer circuit boards are electrically connected through metallized holes, and the surface of the circuit pattern is protected and insulated with PI and adhesive layers.

Mainly divided into single panel, double-sided board, multi-layer board, and soft hard combination board.

Characteristics of flexible circuit boards

1. Short: Short assembly time

All lines have been configured, eliminating the need for redundant cable connections;

2. Small: The volume is smaller than that of a PCB (hard board), which can effectively reduce the product volume and increase the convenience of carrying;

3. Lightweight: Lighter than PCB (hard board), it can reduce the weight of the final product;

4. Thin: Thicker than a PCB (hard board) can improve flexibility and enhance assembly in three dimensions within a limited space.

Advantages of flexible circuit boards

Flexible printed circuit boards are printed circuits made of flexible insulating substrates, which have many advantages that hard printed circuit boards do not have:

1. It can be freely bent, wound, folded, arranged according to spatial layout requirements, and moved and expanded freely in three-dimensional space, thus achieving the integration of component assembly and wire connection;

2. The use of FPC can greatly reduce the volume and weight of electronic products, which is suitable for the development of electronic products towards high-density, miniaturization, and high reliability. Therefore, FPC has been widely used in fields or products such as aerospace, military, mobile communication, laptops, computer peripherals, PDAs, digital cameras, etc;

3. FPC also has advantages such as good heat dissipation and solderability, easy assembly and low overall cost. The design of combining soft and hard also partially compensates for the slight deficiency of flexible substrates in component bearing capacity

FPC Main Raw Materials

Its main raw materials include: 1. substrate, 2. covering film, 3. reinforcement, and 4. other auxiliary materials.

1. Substrate

1.1 Adhesive substrate

1.2 Adhesive substrate mainly consists of three parts: copper foil, adhesive, and PI. There are two types of substrates: single-sided substrate and double-sided substrate. Materials with only one copper foil are single-sided substrates, while materials with two copper foils are double-sided substrates.

1.2 Adhesive free substrate

Non adhesive substrate refers to a substrate without an adhesive layer. Compared to ordinary adhesive substrate, it has fewer intermediate adhesive layers and only consists of copper foil and PI. Compared to adhesive substrate, it has thinner, better dimensional stability, higher heat resistance, higher bending resistance, and better chemical resistance, and is now widely used.

Copper foil: Currently, the commonly used copper foil thicknesses are as follows: 1OZ, 1/2OZ, 1/3OZ. Currently, thinner copper foils with a thickness of 1/4OZ are being introduced, but this material is already being used in China to produce ultra-fine path (line width and line spacing of 0.05mm and below) products. With increasing customer demands, materials of this specification will be widely used in the future.

2. Covering film

It mainly consists of three parts: release paper, adhesive, and PI. Ultimately, only the adhesive and PI parts remain on the product. Release paper will be torn off during the production process and will no longer be used (its function is to protect foreign objects on the adhesive).

3. Reinforcement

Used as a specific material for FPC, in a specific part of the product to increase support strength and compensate for the "soft" nature of FPC.

There are currently several commonly used reinforcement materials:

1) FR4 reinforcement: The main components are glass fiber cloth and epoxy resin adhesive, which are the same as the FR4 material used in PCB;

2) Steel reinforcement: composed of steel, with strong hardness and support strength;

3) PI reinforcement: Same as the covering film, it consists of three parts: PI and adhesive release paper, but its PI layer is thicker and can be produced in a ratio from 2 MIL to 9 MIL.

4. Other auxiliary materials

1) Pure adhesive: This adhesive film is a thermosetting acrylic adhesive film composed of protective paper/release film and a layer of adhesive. It is mainly used for laminated boards, soft and hard bonding boards, and FR-4/steel sheet reinforcement boards to play a bonding role.

2) Electromagnetic protective film: pasted on the board surface to provide shielding effect.

3) Pure copper foil: only composed of copper foil, mainly used for hollow board production.