1. Introduction

Surface Mount Technology (SMT) is one of the most representative manufacturing processes in the electronic assembly industry. When using SMT technology for assembly, the impact of stress factors on product stability must be taken into account. Therefore, formulating a complete set of stress testing standards and methods is of great significance for ensuring the quality and reliability of electronic products. This article will provide a detailed introduction to the SMT stress testing standards and methods, helping readers better understand and apply this technology.

2. Formulation of SMT Stress Testing Standards

The purpose of formulating SMT stress testing standards is to ensure that products remain stable when affected by external environments and to prevent performance failure or structural damage due to stress. The formulation of SMT stress testing standards should be based on relevant national and industry standards, and in combination with the actual situation of the enterprise. Currently, the PCB industry refers to the IPC/JEDEC-9704A document, and the industry reference standard is ±500ue.

3. SMT Stress Testing Methods

(1)X-ray diffraction method

X-ray diffraction is a non-destructive testing method. By analyzing the X-ray diffraction patterns of materials under different strain states, the residual stress and deformation within the materials can be determined. The advantage of this method is its high precision and non-destructiveness, but the testing cost is relatively high and the operation is relatively complex.

(2)Photoelastic method

Photoelastic method is a technique for detecting stress through optical principles. During the testing process, the sample to be tested is placed in a polarized light field. By observing the birefringence phenomenon of the sample under different stress states, the residual stress and deformation inside the sample can be determined. The advantage of this method is its high precision and strong intuitiveness, but it requires special treatment of the samples to be tested, which increases the operational difficulty and cost.

(3)Resistance strain method

The resistance strain method is a way to indirectly measure strain by measuring the change in resistance value. During the testing process, the sample to be tested is adhered to a strain gauge with a certain resistance value. When the sample is subjected to stress, the resistance value of the strain gauge will change. By measuring the change in resistance values and using relevant formulas for calculation, the residual stress and deformation inside the sample can be obtained. The advantages of this method are its simplicity of operation, low cost and good practicability. Therefore, it has been widely applied in the electronic assembly industry.

At present, the third type of resistance strain method is the most frequently used in the PCB industry and also the one with the highest precision.

The testing principle of the resistance strain method: strain is tested based on the change in the resistance of the strain gauge. The strain gages signal is balanced through the Wheatton bridge module and can be converted into the corresponding voltage signal. After passing through the analog/digital circuit inside the tester, the voltage signal can be converted into a digital signal, and then these signals are captured and analyzed by dedicated software.

4. Conclusion

This article introduces the SMT stress testing standards and methods, including the factors that formulate the testing standards, the characteristics of various testing methods, and their application scopes. By establishing a complete SMT stress testing standard and method system, the quality and reliability of electronic products can be effectively guaranteed, and the market competitiveness of enterprises can be enhanced. In practical applications, appropriate testing methods and standards should be selected based on specific products and application environments to achieve accurate and reliable detection results.