X-ray inspection of PCBA and how to control solder paste printing in PCBA processing

X-ray inspection of PCBA and how to control solder paste printing in PCBA processing

X-ray testing technology is a nondestructive testing technology. Compared with other testing methods, X-ray testing technology has many advantages. First of all, X-ray testing technology is a non-contact test, which can avoid scratches and electrostatic interference on the surface of the test sample.

Secondly, X-ray detection technology uses imaging systems to distinguish and intuitively detect the real situation of samples, without test errors due to multi-layer operation and conversion.

In addition, compared with other detection technologies, X-ray detection technology is more convenient in working principle and operation design. After one month of training for a typical PCBA production line worker, they can fully operate and use them.

It must be said that the functions of X-ray detection technology and other detection equipment are complementary, such as visible light detection technology, electrical measurement and analysis technology. In a word, it is an ideal detection method in PCBA process.

What can be detected by X-ray detection equipment is to distinguish substances with different densities by using different absorption characteristics based on the relationship between the penetrability of x-ray and the density of substances. Therefore, if the tested object is fractured, the thickness is different, the shape changes, the x-ray absorption will be different, and the image will be different, thus generating different black and white images, so as to achieve the purpose of non-destructive testing.

X-ray is a kind of ray that can not be seen by people but can penetrate objects. With certain permeability, it can accurately detect the internal defects of products and find out the root causes of defects. Transparent product structure can obtain different levels of black and white contrast and x-ray images through the display process, screen or TV display.

How to Control Solder Paste Printing in PCBA Processing

Solder paste printing is very important for PCBA, which directly affects the overall welding effect of PCBA. In the process of PCBA processing, how to do well in solder paste printing has become a problem that production managers must consider. The effect of solder paste printing consists of steel screen, solder paste, printing process and detection method.

1、 Steel mesh

The steel mesh must be properly enlarged or reduced according to the layout of electronic components on the PCBA board to determine the amount of tin on the bonding pad, so as to achieve the best soldering effect and avoid the occurrence of tin bonding, less tin, etc., which requires strict evaluation by the process engineer. In addition, the material of the steel mesh is also critical, which affects the tension of the steel mesh and the service life of the steel mesh.

In addition, the cleaning and storage environment before feeding the steel mesh is particularly critical. Strictly clean the vias before going online each time, and check whether the vias are blocked or have tin slag. Some PCBA manufacturers suggest to purchase steel mesh tensiometer, and conduct tension test of steel mesh before each feeding.

2、 Solder paste

Solder pastes should be of medium and high grade brands, such as Qianzhu, Vitel, etc. It is better to use solder pastes containing active ingredients such as gold or silver. Solder paste must be strictly stored in a refrigerator with a temperature of 2 to 10 degrees. Relevant statistics must be made for each warehousing and outbound. The recovery of solder paste must be strictly controlled within the scope of IPC standards, and the solder paste mixing procedure must be strictly implemented before going online.

3、 Solder paste printing

At present, manufacturers are using full-automatic solder paste printers, whose equipment can well control parameters such as printing strength and speed, and has certain automatic cleaning functions. The operator only needs to set the parameters in strict accordance with the regulations.

In the process of mass production, it is particularly important to detect such phenomena as plugging and offset of the steel mesh. Especially when some defects detected by SPI after printing show an upward trend, the machine must be stopped to check the operation of the steel mesh itself.

4、 SPI printing effect detection

After the solder paste printing machine, it is particularly important to configure SPI solder paste detector, which can effectively detect a lot of defects in the solder paste printing process, such as little tin, continuous tin, notch, wire drawing, offset, etc. To maximize the overall welding PPM value.

It is not a secret to manage the printing effect of solder paste. It requires managers to carefully implement each management method in the PCBA processing process. And design a closed-loop mechanism that can find and detect defects

PCB manufacturers, PCB designers and PCBA manufacturers will explain how to X-ray detect PCBA and how to control solder paste printing in PCBA processing.