In recent years, FPC, with its own characteristics, has played an increasingly important role in the design of slide mobile phones and folding mobile phones.

The number of orders for sliding mobile phone board and folding mobile phone multilayer board is increasing, and how to control the quality of FPC manufacturers and do such products well in the process is important.

I. Introduction

With the miniaturization, high-speed and digitalization of electronic products, the rapid development of personal communication terminals, shanzhai mobile phones and 3G communication, and the networking needs of information terminals (computers, TVS, telephones, faxes), the FPC life and impedance requirements of slide-cover mobile phones and foldable mobile phones suitable for the communication terminal mobile phone industry are becoming more and more detailed. In the production of FPC manufacturers, how to control such products in the process is important.

The characteristics of FPC(Flexible Printed Circuit board can be radial printed circuit board, also known as FWPC) mainly have the following aspects:

(1) Good flexibility: arbitrary bending deformation, small winding radius, can move freely along X, Y, Z three directions;

(2) Small occupation space: light and thin, so that the narrow space of the instrument is fully utilized to meet the requirements of electronic products.

(3) Light weight: the soft board is designed according to the carrying capacity rather than the mechanical strength, so the weight is light;

(4) Good sealing: low tension sealing design, can withstand harsh environment;

(5) Stable transmission characteristics: wire spacing can be freely designed according to electrical parameters, and the general layout is finalized;

(6) The assembly process is good: the product free termination and overall termination performance is good, suitable for welding, plugging, as well as three-dimensional wiring and three-dimensional space connection;

(7) Good insulation performance: the substrate PI and PET polymer materials used in the soft board have high insulation strength, and the general line is covered with film protection, so the insulation performance is greatly improved.

In recent years, FPC, with its own characteristics, has played an increasingly important role in the design of slide mobile phones and folding mobile phones. People's requirements for their life expectancy are becoming more and more stringent. Therefore, our company has recently increased the number of orders for sliding mobile phone plate and folding mobile phone multi-layer plate. In order to strengthen the quality and training of personnel, we specially control the design and layout concept, material selection and process maintenance of sliding mobile phone plate and folding mobile phone multi-layer plate in the production process, so as to reduce the occurrence of defects and increase the percentage of a pass rate.

Second, production requirements:

1, design material selection

The first step is important. If the customer does not embody or specify what substrate to use, then calendered copper should be considered because its bending resistance is better than electrolytic copper. However, the substrate with and without rubber has a relatively large impact on the bending performance, and the bending resistance of the non-rubber substrate is generally better than that of the rubber substrate.

Classification of substrates:

1.1 Copper foil:

1.1.1 Calender copper.

Calendered copper is the electrolytic cathode copper deposited into a strip, which is formed by drawing-pressing. Because of the melting, the composition is relatively simple and the crystal distribution is uniform. Because the crystallization direction is parallel to the soft plate, it is suitable for the transmission of high frequency signals. The properties of calendered copper are better than those of electrolytic copper. Its thickness is 1/4OZ, 1/3OZ, 1/2OZ, 1OZ, 2OZ several.

1.1.2 Electrolytic copper:

Electrolytic copper foil is the use of electroplating principle to deposit copper ions on the rotating smooth cathode drum, and then the copper foil is separated from the cathode roller to obtain a smooth and rough copper foil, after surface treatment can be used. The contact surface of electrolytic copper foil and cathode drum is very smooth, but the other side will be rough under the action of high current density due to contact with the plating solution. After surface treatment, the rough surface can increase the surface contact area and improve the adhesion with the protective film. Its thickness is 1/4OZ, 1/3OZ, 1/2OZ, 1OZ, 2OZ several.

Comparison of properties of calendered copper and electrolytic copper:

Copper cost

flexibility

Application product type

Product type

Rolled copper

(RA,Rolled Annealed)

high

better

Flex, dynamic

Communications, NB Hinge

Handset, DVD

Electrolytic copper

(ED,Electro-deposited)

low

poor

Static, combined fold once

The auto industry, game consoles

High ductility electrolytic copper

(High Eensitv)

In the

In the

Static mainly, dynamic depends on the situation

PDP, LCD

1.2 PI:

PI(polytipsy imide), PET(polyethylene) or GE(glass fiber) are often used. PI has the best performance and higher price. Thickness of 1/2mil, 1mil, 2mil several.

1.3 Materials selection and collocation during design

Due to the high performance requirements of the slide phone, the choice of materials, whether the substrate or CVL, should be considered in the direction of "thin".

1.4 Design and Layout

1.4.1 Bend Area Line Requirements:

a) There should be no through hole in the part to be bent;

b) The protection copper wire should be added to the most sides of the line. If there is insufficient space, the protection copper wire should be added to the inner R Angle of the bent part;

c) The connecting part of the line should be designed as an arc.

1.4.2 Bending area (air gap) requirements: the bending area needs to be stratified and the glue removed to facilitate the dispersion of stress. As long as the bending area does not affect the assembly, the larger the better.

2. Production process

When the material is selected, it is more important to control the sliding plate and multi-layer plate from the production process. In order to increase the number of bending, the production process, especially the electrodeposited copper process, must be specially controlled. The general sliding cover plate and the layered plate of the multi-layer board have life requirements, and the minimum bending requirement of the mobile phone industry is generally 80,000 times.

Because the general process used by FPC is the whole plate plating process, unlike the hard plate that will go through a electrogram, the copper thickness is not required to be plated too thick when electroplating copper, and the surface copper is generally 0.1-0.3mil. (The deposition ratio of hole copper and surface copper when electroplating copper is about 1:1) But in order to ensure the quality of hole copper and the non-stratification of hole copper and the substrate when SMT is at high temperature, as well as the electrical conductivity and communication installed on the product, the thickness of copper is required to reach 0.8~1.2mil or above.

In this case, there will be a problem, some people may ask, surface copper requirements only 0.1~0.3mil, and (without substrate copper) hole copper requirements above 0.8~1.2mil how to do it? This requires an additional process: the process flow chart of the general FPC board (if only 0.4~0.9mil plating is required) is: opening → drilling → sinking copper (black hole)→ electric copper (0.4~0.9mil)→ graphics → post-process.

The process flow to make bending resistance requirements is as follows: opening → drilling → copper sinking (black hole)→ first electricity (electricity 0.1~0.3mil)→ through hole production → second electricity (0.4~0.9mil)→ graphics → post process.