What are the internal and external failure factors of MLCC?
What is the failure of chip multilayer ceramic capacitors (MLCC)? What are the factors of MLCC? According to the failure, we can divide it into internal factors and external factors. If there are certain defects inside or outside the MLCC, it will directly affect the electrical performance and reliability of MLCC products, and bring hidden dangers to product quality.
We divide internal factors into these three types: void, crack, and delamination.
First of all, let's talk about the voids in the ceramic dielectric. What is the void in the ceramic capacitor dielectric?
1. Dielectric voids in ceramic capacitors
The main reason for the voids in ceramic capacitors is the organic or inorganic pollution in the ceramic powder, improper fire control during the sintering process, the generation of voids will lead to leakage, and the leakage will cause internal heating of the device, further reducing the bonding performance of the ceramic medium. lead to increased leakage. This process occurs cyclically and continues to deteriorate. In severe cases, it will lead to serious consequences such as cracking, explosion, and even burning of multilayer ceramic capacitors.
2. Sintering cracks
Sintering cracks often originate from one end of the electrode and expand along the vertical direction. The main reason is related to the cooling rate during the sintering process. Cracks and hazards are similar to voids.
3. Layering
The sintering of multilayer ceramic capacitors is stacked and co-fired with multilayer materials. The sintering temperature can be as high as 1000°C or more. Inadequate bonding between layers, volatilization of internal pollutants during the sintering process, and improper control of the sintering process may lead to delamination. Delamination is similar to the hazards of space and cracks, and is an important inherent defect of multilayer ceramic capacitors.
Detection method:
The ultrasonic flaw detection method can more accurately detect the internal defects of ceramic capacitors, and can determine the location of the defects. After further grinding analysis, the whole batch of products with internal defects will be scrapped, which shows that the ultrasonic flaw detection method has an important role in ceramic capacitors. The effectiveness and reliability of the detection and determination of internal defects.
External factors: cracks
1. Temperature shock cracks: It is mainly caused by the temperature shock of the device during soldering and wave soldering. Improper repair is also an important reason for the large temperature shock cracks.
2. Mechanical stress cracks
The characteristic of ceramic capacitors is that they can withstand large compressive stress, but their ability to resist bending is relatively poor. Any manipulation that may cause bending during device assembly may lead to cracking of the device.
Detection method:
For external defects, manual visual inspection under a microscope or automatic appearance sorting equipment is usually used.