PCB Tech - PCB process SPI (Solder Paste Inspection) solder paste inspection machine can do?

PCB process SPI (Solder Paste Inspection) solder paste inspection machine can do?

SPI is the abbreviation of Solder Paste Inspection. It is called solder paste inspection in Chinese. If it is a solder paste inspection machine, add the English word Machine at the end, but in most cases, you only need to talk about SPI with the other party and you will know that you are talking about solder paste. Check the machine.

What is the use of SPI (Solder Paste Inspection)? What kind of inspection can you do for us? Why are there more and more SMT production lines with SPI devices?

80% of the defects in the SMT processing process come from improper solder paste printing

If the working bear tells you that about 80% of the defective rate of SMT comes from improper solder paste printing, then you think that a solder paste inspection (SPI) checkpoint should be set up after solder paste printing and before printing/mounting. Boards with poor solder paste printing should be brushed off before the parts are printed. Can this improve the yield rate of SMT soldering? The answer should be yes, the key point is how to use the solder paste inspection machine to correctly screen out the boards with poor solder paste printing, and then go forward to track why the solder paste printing is defective.

Especially now there are more and more parts below 0201 or bottom soldering parts such as BGA, which are very sensitive to the quality of solder paste printing. If the board with solder paste printing problems can be detected before the furnace, it will It is more effective and cost-effective than detecting after the reflow soldering is completed, because the repair of the board after the furnace usually requires a soldering iron or complicated repair tools, and the board may be damaged.

This kind of solder paste inspection machine is actually similar to the AOI (Auto Optical Inspection) optical identification system device that we usually usually place behind the SMT furnace. It also uses optical images to check the quality. The difference is that the solder paste inspection machine adds solder paste. Thickness measurement laser device, so the problems that SPI may encounter are similar to AOI, that is, first take a piece of jigsaw and visually check that there is no problem, and then let the machine take a picture as a standard sample (Golden Sample). The image and data of the board are used to make judgments. Of course, there will be a lot of misjudgment rate. Therefore, its parameters must be continuously modified until the misjudgment rate is reduced to a certain level. There are engineers who can write programs and maintain them.

In addition, most solder paste inspection machines can eat Gerber and CAD, but there are usually some errors and still need to be adjusted.

What are the capabilities of the solder paste inspection machine? Can you check out those solder paste printing defects?

Okay, let’s see what capabilities the solder paste inspection machine can do for us? Can also help us check out the defects of solder paste printing? Please note that the solder paste inspection machine can only perform image inspection on the surface. If there is an area covered by an object, it cannot be inspected. However, the timing of the use of the solder paste inspection machine should be before the parts are placed, so it should be No solder paste will be covered.

The solder paste inspection machine can measure the following data:

Solder paste printing volume

Height of solder paste printing

Solder paste printing area/volume

Flatness of solder paste printing

Make SPC statistics to measure process capability

In addition, the solder paste inspection machine can detect the following defects:

Whether the solder paste printing is shifted (shift)

Whether the height deviation of solder paste printing (pointing)

Whether solder paste printing is bridged (Bridge)

Whether the solder paste printing is defective or damaged

It’s just that a few devices are machines, and people are the key. SPI is a set of tools that can help improve product quality, thereby increasing production and reducing costs. Will affect the output.

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