Identification and control of PCBA process stress and strain risks

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Identification and control of PCBA process stress and strain risks

Because PCBA board components and their solder joints are very sensitive to stress damage, PCBA stress identification under harsh conditions is important. Excessive stress can cause damage to the solder joints of all surface treated package substrates. These obstacles include solder ball cracks, line damage, pad lift, board cracks, and body cracks in ceramic components during PCBA manufacturing, testing, and use.

You can use strain testing to objectively analyze the level of strain and strain rate that occurs during PCBA assembly, testing, and assembly to identify and improve dangerous manufacturing processes. The general method for strain testing is as follows.

1. Electrical measurement methods: resistive, capacitive, inductive

2. Light measurement method: Moire method, holographic interference

3. Optical fiber sensing technology

4. Digital image processing technology: CCD camera is used to process measurement distortion, high-speed camera technology, etc.

5, X-ray technology: welding residual stress test

Among them, the strain electrical measurement technique is most widely used. The basic principle of the strain electrical measurement method is to attach a strain gauge (called a strain gauge) to the surface of the member to be tested. When a member deforms, the strain gauge deforms with the member, and the resistance value of the strain gauge corresponds. A resistance strain gauge measures the change in the resistance value of the strain gauge and converts it to a strain value, or the output is proportional to an analog electrical signal (voltage or current) and recorded by a recorder, or a used computer Perform data processing according to the prescribed requirements and obtain the required strain or stress values.

In addition, the shadow moiré test technique is also a common test method for testing package thermal deformation. By analyzing interference ripples, contour lines that reflect the surface shape of the sample can be obtained accurately, and the degree of deformation of the object can be obtained. This is particularly suitable for objective analysis of package thermal deformation. The degree of coincidence of thermal expansion between different materials to reach the material. We recommend improving the straight rate and reliability of the product.