Failure analysis and detection center: failure forms and causes of electronic parts

Date：2021-12-27 14:10:00 Views：1293

The main failure modes of electronic components include but are not limited to open circuit, short circuit, burning, explosion, electric leakage, function failure, electrical parameter drift, unstable failure, etc. Failure may occur in all stages of the product life cycle, in all links from product development stage, production stage to use stage. By analyzing the failed products of process waste and defective products, early failure, test failure, pilot test failure and on-site failure, the failure mode and failure mechanism are clarified, and finally the failure cause is clarified.

Early failure period is the failure of mechanical parts in the early stage of use. The failure rate is high, but it decreases rapidly. Early failure problems are mostly related to improper design, manufacturing, installation or use.

The failure rate of accidental failure period is low and stable. It is the normal working period of mechanical parts. The failure of parts at this stage is generally caused by accidental factors, so the failure is random. If we want to reduce the failure rate in this period, we must take measures from the aspects of material selection, design, manufacturing process, correct use and maintenance.

After the accidental failure period, due to long-term use, the failure efficiency increases sharply due to wear and fatigue crack propagation of parts, indicating that the service life of mechanical parts has exceeded the service life. This stage is called wear failure period. At this stage, although important equipment or parts have not failed, they shall be replaced or repaired according to corresponding criteria to prevent major accidents.

When mechanical parts lose their working capacity or fail to meet the design requirements for some reasons, it is called failure. The failure of mechanical parts does not simply mean damage, which can be summarized into three cases: completely unable to work; Although it can work, its performance is poor and exceeds the specified index; Serious injury and loss of safe working ability. Overall fracture, plastic deformation, surface wear, excessive elastic deformation, functional failure, etc.

1. Integral fracture

When the parts are subjected to external loads such as compression, tension, shear, bending and torsion, the fracture occurs because the stress on a dangerous section exceeds the strength limit of the parts, or the fatigue fracture occurs on the dangerous section when the parts are subjected to variable stress. For example, the fracture of bolt, the fracture of gear tooth root, etc.

2. Plastic deformation

Plastic deformation is an irrecoverable deformation. Permanent deformation will occur when engineering materials and components are loaded beyond the elastic deformation range, that is, unrecoverable deformation or residual deformation will occur after removing the load, which is plastic deformation. Not all engineering materials have the ability of plastic deformation. Metals and plastics have different degrees of plastic deformation ability, so they can be called plastic materials. Brittle materials such as glass, ceramics and graphite have no plastic deformation ability. Obvious plastic deformation is generally not allowed in the design of engineering components, otherwise the components will not maintain the original shape or even fracture.

3. Surface wear

Wear is a basic type of component failure. Generally speaking, wear refers to the reduction of geometric dimension (volume) of parts. The loss of the function specified in the original design of parts is called failure. Failure includes complete loss of original function; If the function is reduced and there is serious damage or hidden danger, the reliability, safety and safety will be lost if it continues to be used. According to the characteristics of surface failure mechanism, wear can be divided into abrasive wear, adhesive wear, surface fatigue wear, corrosion wear and fretting wear. The first three are the basic types of wear, and the latter two occur only under certain specific conditions.

4. Excessive elastic deformation

Exceeding the elastic limit is called excessive elastic deformation, which usually causes plastic deformation, commonly known as "permanent deformation"

5. Function failure

The constituent materials of the structure can meet the requirements, and the structure has been completed, but it can not meet the needs of the original design. For example, when a bridge is designed and erected, the clearance under the bridge is too low, so that a considerable number of ships cannot pass under the bridge. This is an example of functional failure. The structure cannot meet its functional needs. Here, the constituent materials of the structure can meet the requirements, and the structure has been completed, but it can not meet the needs of the original design. For example, when a bridge is designed and erected, the clearance under the bridge is too low, so that a considerable number of ships cannot pass under the bridge. This is an example of functional failure. This kind of failure is the first consideration in any design.

In short, although there are many possible failure forms of mechanical parts. But to sum up, the main reason is due to the influence of strength, stiffness, wear resistance, temperature on working capacity, vibration stability and reliability. Master and analyze its failure principle, so as to lay a solid foundation for improving output and quality, reducing device cost and improving product competitiveness.