1. Background

In the process of daily production and life, many times we hope to achieve the purpose of combining the same substance or dissimilar substances into a whole through the surface, which can play a role in stress transmission and can meet certain physical and chemical performance requirements. We need to use adhesive. However, adhesives are not omnipotent. Sometimes due to insufficient curing, oil stains on the bonding surface, environmental factors, etc., bonding failures may occur. If necessary, adhesive testing is required.

2. Failure analysis of magnetic circuit bonding in an electro-acoustic enterprise

2.1 Description of failure process

An electro-acoustic company conducted a regular product reliability test during the production process-when the product dropped, the bonding failure occurred. The two metal parts will fall off when they fall below the specified number of times, as shown in the figure below (in order not to disclose company information, only partial information of the bonding area is intercepted).

2.2 Failure analysis

The failure analysis of adhesive bonding should be considered from two aspects, one is the failure of the adhesive, and the other is the failure of the material bonded by the adhesive which leads to the failure of the bonding. At the beginning of the incident, the company analyzed the adhesive failure and replaced a variety of adhesives, but the above-mentioned failures were not well improved. After receiving the case, our company analyzed the case based on the materials bonded by the adhesive in combination with the previous work of the company. The analysis found that the bonding area of ​​the component 2 was brighter than the unbonded area after the bonding failure, so it was suspected to be bonding. The surface of the rear part 2 failed.

With the help of scanning electron microscope (SEM) and its built-in energy spectrometer (EDS) to analyze the bonded area and unbonded area of ​​component 2, it is found that the element in the bonded area is only Zn, not the bonded area. The elements are Zn and O, and a small amount of Cr.

The metal part is a galvanized part. The customer requires that the galvanized part provided by the supplier be a product that is passivated with trivalent chromium after galvanization. However, the surface composition analysis found that the chromium content in the unbonded area is low and it is bonded. The presence of chromium cannot be detected in the area.

Through the above data analysis, the failure may be due to the unqualified electroplating of the supplier of Component 2, and the coating on the surface of Component 2 failed after bonding. It is recommended that the customer replace the supplier of Component 2. This problem has been solved and reduced for the customer. Unnecessary economic losses.

3. Conclusion

Through the above cases, we found that in the adhesive bonding process, there are many factors that affect the failure, but the failure of the bonding material is also a factor that cannot be ignored in the failure of the adhesive.