Discussion on the Common Faults of FPC Caused by Humidity

Discussion on the Common Faults of FPC Caused by Humidity

Circuit board manufacturers, circuit board designers and PCBA manufacturers explain to you the common failures of flexible circuit boards caused by humidity

Flexible Printed Circuit Board (FPC) is referred to as "flexible board", commonly known as FPC in the industry. It is a flexible insulating substrate (mainly polyimide or polyester film) The printed circuit board has many advantages that the hard printed circuit board does not have. For example, it can bend, wind and fold freely. The volume of electronic products can be greatly reduced by using FPC, which is suitable for the development of electronic products in the direction of high density, miniaturization and high reliability. Therefore, FPC has been widely used in aerospace, military, mobile communications, laptops, computer peripherals, PDAs, digital cameras and other fields or products.

When we are making PCB boards, we often have common failures of circuit boards caused by humidity, which lead to changes in circuit parameters in the circuit boards, which lead to circuit board failures. The circuits in flexible circuit boards are in short circuit state, which leads to circuit board failures, signal processing or transmission lines are open circuit, which leads to circuit board failures.

The definition of humidity is that it contains more moisture than under normal conditions. Therefore, the circuit board used in a humid environment contains relatively large moisture in the air. When the moisture is too large, it will turn into water drops and fall onto the circuit board. When the water drops onto the circuit board and spreads on the flexible circuit board, it will attach to each pin or printed line of electronic components.

Since the electronic components used in the current circuit board are SOP or SSOP chip components, the distance between the pins is very small, especially for the SSOP packaged integrated circuit, the distance between the pins is very small. When moisture is converted into water droplets on the SSOP packaged integrated circuit pins, if the circuit board is in operation at this time, An invisible resistance will be added between the pins of the integrated circuit (because the water is conductive), or even a short circuit will be caused, resulting in the failure of the circuit board in operation.

If the water droplets converted from moisture drop between the pins of electronic components on the circuit board, and the circuit board is just not working or powered off at this time, it will not immediately cause harm to the circuit board. However, after the pins of electronic components or printed wires are soaked by water droplets, the lead pins of the components will rust. After a long time, the lead pins of the components will break due to corrosion, causing circuit board failure. After the printed wires are soaked by water droplets, In particular, the signal transmission line is relatively small. After being soaked for a period of time, the printed wire will be broken, which will lead to the failure of the circuit board when it is put into operation.

The causes of circuit board failure caused by humidity fall into three categories:

1. It causes the circuit parameters in the circuit board to change and causes the circuit board fault;

2. This causes the circuit in the FPC to be in a short circuit state, causing the circuit board to fail;

3. The signal processing or transmission lines in the circuit board are broken, causing the circuit board to fail. Friends can formulate relevant measures according to these three items to reduce or avoid the occurrence of circuit board failure caused by moisture in the equipment under your jurisdiction. Circuit board manufacturers, circuit board designers and PCBA manufacturers explain to you the common failures of flexible circuit boards caused by humidity