PCB Tech - The difference between soft and hard boards, FPC welding

1. The difference between PCB hard board and FPC soft board

Hard board: PCB (Printed Circuit Board); Soft board: FPC or FPCB (Flexible Printed Circuit Board); Rigid-flexible board: RFPC or RFPCB (Rigid-Flex Printed Circuit Board), as the name implies, it has both hard board and soft board Features a new type of wire board. The hard board part is the same as the PCB circuit board, which has a certain thickness and strength, can install electronic components and bear a certain mechanical force, while the soft board part is usually used to achieve three-dimensional installation. The use of the soft board makes the whole piece of soft and hard combined The board can be bent locally.

FPC: FPC, also known as flexible circuit board, can be bent.

Flexible printed circuit board (FlexiblePrinted Circuit, FPC), also known as flexible circuit board, flexible circuit board, it is favored for its light weight, thin thickness, free bending and folding and other excellent characteristics, but the domestic quality inspection of FPC is still mainly Relying on manual visual inspection, the cost is high and the efficiency is low.

With the rapid development of the electronics industry, the design of circuit boards is becoming more and more high-precision and high-density. Traditional manual inspection methods can no longer meet the production needs. FPC defect automatic detection has become an inevitable trend in the development of the industry.

2. FPC manufacturer's soft board welding process

The following FPC manufacturers mainly introduce the related processes of manual soldering: manual drag soldering is to manually use an electric soldering iron and tin wire to solder the solder together. For FPC soldering, it is recommended to use OKi soldering iron and A tin wire.

At present, there are two general welding processes for FPC manufacturers' soft boards, one is tin press welding, and the other is manual drag welding. Generally, it is recommended to use a tin press for pressure welding. The advantages are: smooth welding, less false welding, short circuit and other defects. Disadvantages are: high cost, and the layout of the components needs to be considered in the plate design. Below we mainly introduce the related process of manual soldering: manual drag soldering is to manually use an electric soldering iron and tin wire to solder the solder together. For FPC soldering, it is recommended to use OKi soldering iron and A tin wire.

The main sequence of FPC welding is: FPC paste alignment-tin delivery and drag welding-visual inspection-electrical inspection. FPC paste alignment: Check whether the FPC pad and the corresponding solder surface are flat and oxidized before the alignment. Note that after the paste, the pad must expose a pin of about 1.00mm to facilitate soldering.

The main control time and position of FPC manufacturers' soft boards:

1. Time: Before soldering, the soldering iron must be placed on the pad for 2-3S, so that the FPC and the pad are fully heated, which can effectively prevent false soldering;

2. Position: The tilting direction of the soldering iron and gold finger is about 30 degrees.

There are four main control points for the soldering and drag welding of FPC manufacturers soft boards:

1. Time: Generally, the recommended time is calculated by 3S/the length of the soldering iron tip, which is about 4-10S;

2. Temperature: 290-310 degrees Celsius;

3. The tin delivery position: the position of the tin should be biased towards the soldering pad;

4. Strength: When the soldering iron tip is in contact with the components, a slight pressure should be applied to the principle of not causing damage to the golden fingers.