Quality inspection method for SMT reflow soldering products

To ensure the reflow soldering quality of printed circuit boards, we must always pay attention to whether the reflow soldering process parameters are reasonable. If there is a problem with the parameter setting, the welding quality of the printed circuit board cannot be guaranteed. Therefore, under normal circumstances, the furnace temperature must be tested twice a day and once at low temperature. Only by continuously improving the temperature curve of welding products and setting the temperature curve of welding products can the quality of processed products be guaranteed.

1、 Visual inspection after reflow soldering of circuit board

Simple and low cost. However, the low efficiency and high rate of missed inspection are also related to the experience and seriousness of the personnel.

2、 Automatic optical inspection method (AOI) for PCB quality after reflow soldering

Avoid the interference of human factors. No mold required. Most defects can be inspected, but components that cannot be seen at BGA, DCA and other solder joints cannot be inspected.

3、 Electrical quality test method (ICT) for printed circuit boards after reflow soldering

The correct connection of various electrical components can be checked. However, complex needle bed molds are required, which are expensive and complex to maintain. As for the process performance of welding, with the development of electronic product assembly towards miniaturization, high density, BGA and CSP, the needle measuring method of ICT is more and more limited.

4、 X-ray inspection method for quality of circuit board after reflow soldering

Almost all process defects can be inspected. Through the perspective characteristics of X-ray, check the shape of the solder joint and compare it with the standard shape in the computer library to judge the quality of the solder joint. Especially for the solder joint inspection of BGA and DCA components, it plays an irreplaceable role. There is no need to test the mold. However, it is impossible to distinguish between the right and wrong parts. Disadvantages the price is quite expensive at present.

5、 Ultrasonic testing method for PCB quality after reflow soldering

The reflected signal of ultrasonic wave can be used to detect the defects such as cavities and delaminations in IC chip packages such as QFP and BGA. Its disadvantage is that the ultrasonic inspection method can be used only when the PCB is placed in a liquid medium. It is more suitable for laboratory application.

Reflow soldering inspection is a comprehensive inspection of welding products. Generally, the points to be tested are: check whether the spot welding surface is smooth and clean, whether there are holes, holes, etc; Whether the spot welding is crescent shaped, whether there is more tin and less tin, whether there are monument, bridge, parts movement, missing parts, tin beads and other defects. Whether each component has different levels of defects; Check whether there are short circuit, continuity and other defects during welding, and check the color change on the surface of the printed circuit board.