PCB Technical - Analysis and Improvement of the Reasons for the Expansion and Shrinkage of the Rigid-flex Board

Analysis and Improvement of the Reasons for the Expansion and Shrinkage of the Rigid-flex Board

Rigid-flex board manufacturers:

The source of expansion and withdrawal depends on the nature of the material.

In order to solve the problem of diluting and expansion and removal of the hard adhesive board, the polyimide material of the flexible board should be introduced first.

(1) Polyimide has excellent heat dissipation performance and can withstand the thermal shock of high-temperature lead-free soldering.

(2) For small airplanes that need to pay more attention to signal integrity, most equipment tends to use flexible lines.

(3) Polyimide has the following characteristics: high glass transition temperature and high melting point. Generally speaking, this issue should be dealt with within a range of 350 people or more.

(4) In organic dissolution, polyimide is insoluble in organic solvents. The expansion and removal of the flexible board material is mainly related to Pi and the adhesive material, that is, the higher the degree of immersion in IMIEIP, the greater the ability to control expansion and withdrawal.

According to the normal production method, the flexible map will produce different degrees of expansion and contraction in the process of forming the graphic circuit and the flexible and hard path after opening.

After etching the patterned circuit, the density and direction of the circuit will cause a readjustment of the pressure on the entire surface of the board, resulting in a general change in expansion and contraction on the surface of the board.

In the process of soft bonding and compression, the flexible card will have different degrees of expansion and contraction. Due to the inconsistency between the expansion and contraction coefficients of the surface coating film and the Pi matrix, a certain degree of expansion and contraction will also occur.

Basically, the expansion and contraction of any material is caused by temperature. In the long-term PCB production process, in many hot and humid processes, the material will slightly change, but from the long-term production experience, the change is normal.

How to control and improve? Strictly speaking, the internal stress of each material roll is different, and the control of the process of producing cards in each batch is not exactly the same.

Therefore, the control of the expansion and contraction coefficient of the material is based on a lot of experience, and the control of this process and the statistical analysis of the data are particularly important.

In practice, the expansion and contraction of the elastic plate are divided in stages: First, from the opening to the cooking plate, the expansion and contraction are mainly caused by the influence of temperature.

In order to ensure the stability of the expansion and contraction caused by the cooking plate, the consistency of this process is the first step. According to a uniform material, the heating and cooling of each cooking plate must be uniform, and the cooking plate should not be placed in the air because the research has been carried out indiscriminately.

Only in this way can the expansion and contraction caused by the internal limitation of the material be eliminated to the greatest extent. ipcb is a high-precision, high-quality PCB manufacturer, such as: isola 370hr PCB, high-frequency PCB, high-speed PCB, ic substrate, ic test board, impedance PCB, HDI PCB, Rigid-Flex PCB, buried blind PCB, advanced PCB, microwave PCB, telfon PCB and other ipcb are good at PCB manufacturing.