Hot bending of PC board, also called hot pressing, is a process of heating PC board to a certain temperature according to its thermoplastic characteristics, and plastic deformation occurs after softening.
PC boards can be hot bent or cold bent, but because cold bending can only be carried out for simple processing such as linear bending, there is nothing to do for complex processing needs such as radian. However, blistering and whitening are easy to occur if you do not pay attention during hot bending. How can you avoid them?
The thermal deformation temperature of PC board is about 130 ℃ (1.18 MPa), and the glass transition temperature is about 150 ℃. Above this temperature, the board can be hot formed.
Whether the PC board is processed with electric heating wire or oven, there will be blistering and whitening at the bending part in many cases, which may affect the appearance, or even the entire scrap, resulting in high loss rate.
The blistering of the sheet is usually caused by two reasons
1、 If the heating time of PC board is too long/the temperature is too high, the board will bubble (if the temperature is too high, the interior will start to melt, and the external gas will enter the interior of the board). In general, the post processing is not like the accurate control of temperature and heating time by equipment during plate production, which can only be judged manually, so the bending is generally completed by experienced professional workers.
2、 The PC board itself will absorb moisture (under standard atmospheric pressure, the water absorption rate of 23 ℃ and 50% relative humidity is 0.15%). Therefore, if the finished board is stored for a long time, it will often absorb moisture in the air. If the moisture is not removed before molding, bubbles and mist like micropores will appear after molding, thus affecting the appearance of the products.
In order to avoid abnormal conditions caused by moisture, the plates should be pre dried at a lower temperature for a period of time before heating and forming. Generally, moisture can be removed at a temperature of 110 ℃~120 ℃, and the temperature of water removal should not be higher than 130 ℃ to prevent the plates from softening. The duration of moisture removal depends on the moisture content of the plate, the thickness of the plate and the drying temperature taken. The dehydrated plate can be safely heated to 180~190 ℃, and can be easily deformed.
PC board bending is an indispensable process in PC board processing and production. As a production and processing factory, it should comprehensively consider which process to choose according to the specific requirements of the product, and control the key points that are prone to problems, so as to produce PC board products without bubbles and size standards!
