What are the main undesirable phenomena of PCBA fault analysis method?

Date：2022-06-09 17:16:59Views：805

Overview of modern electronic assembly process

It is mainly based on PCBA. Therefore, the research on the reliability of electronic assembly process is mainly based on the fault phenomenon on PCBA.

The fault phenomena of PCBA can be divided into two categories: those occurring in the production process and those occurring during the service of users. (1) Failure phenomena of PCBA (internal or surface) during manufacturing: such as plate explosion, delamination, surface excess, ion migration, chemical corrosion (rust), etc. (2) There are various failure modes and failure behaviors on PCBA during the service period of users, such as false soldering, solder joint brittle fracture, microstructure deterioration and reliability degradation in solder joints, etc.

Purpose of fault analysis

Fault analysis is the process of determining the cause of fault, collecting and analyzing data, and summarizing and eliminating the fault mechanism that causes the failure of specific devices or systems.

The main purposes of fault analysis are:

Find out the cause of the fault;

Trace the adverse factors existing in process design, manufacturing process and user service;

Put forward corrective measures to prevent the recurrence of faults. Through the accumulated results of fault analysis, continuously improve the process design, optimize the product manufacturing process, and improve the usability of products, so as to achieve the purpose of comprehensively improving the reliability of products.

PCBA failure rate curve

1. PCBA product failure rate curve includes the following three levels, namely:

Component failure rate curve: as shown in Figure 1 (a). The forced aging of components before leaving the factory can effectively reduce the failure rate of components during the service life of users.

Component supply life curve: as shown in Figure 1 (b). It describes the service life of components after reaching the user, which has a significant impact on the reliability of the system.

PCBA assembly failure rate curve: as shown in Figure 1 (c). It is affected by three parts: SMD incoming material life, SMD assembly life and solder joint life. At this time, the service life of PCBA basically depends on the service life of solder joint. Therefore, ensuring the welding quality of each solder joint is the key link to ensure the high reliability of the system.

Figure 1 PCBA product failure rate curve

2. Typical instantaneous failure rate curve of PCBA. Typical instantaneous failure rate of PCBA is called typical failure rate of PCBA for short. Instantaneous failure rate is the probability of failure in unit time after PCBA works to time t. The typical instantaneous failure rate curve of PCBA consists of three areas: premature aging area, product service area and aging area, as shown in Figure 2.

Figure 2 typical instantaneous failure rate curve of PCBA

Levels, principles and methods of PCBA failure analysis

1. level of failure analysis in the production and application of electronic products, the control and analysis of PCBA and solder joint failure are basically the same as the reliability control and analysis of other systems, as shown in Figure 3.

2. principle of failure analysis - basis of mechanism reasoning

Site information;

Retest (failure mode confirmation) result analysis;

Failure mechanism of specific process and structure of the object;

Failure mechanism related to specific environment;

The relationship between failure mode and failure mechanism;

Long term accumulation of relevant knowledge and experience.

Figure 3 reliability engineering control

3. failure analysis method the method used in PCBA failure analysis. At present, some experts in the industry have summarized a good analysis model, as shown in Figure 4.

Figure 4 PCBA failure analysis method