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Key factors determining the accuracy of a fully automatic solder paste printer

Time:2019-07-20   |   Source:   |   Compile :9

The factors that determine the printing accuracy of the solder paste printing machine, in addition to the quality of the solder paste printing machine and the operation of the solder paste printing machine, also affect the precision of solder paste printing, such as cleaning of steel mesh, image positioning, steel mesh removal These can affect the printing precision of the solder paste printing machine. The following is a key factor to determine the accuracy of the automatic solder paste printing machine.

Automatic solder paste printing machine

First, the cleaning of automatic solder paste printing machine

All automatic solder paste printing machines are dry cleaning, wet cleaning and vacuum cleaning. The automatic solder paste printing machine is responsible for automatically cleaning the steel mesh to ensure the printing quality. With the development of SMT, the gap is small, the speed is fast, and many pull tips on the PCB, even tin and cleaning have a great relationship! The quality of automatic cleaning is directly related to the quality of the product. The improvement of the cleaning function can achieve the speed and the high efficiency of production. In 2006, the domestic solder paste printing machine made major improvements in cleaning. Independent cleaning mechanism, new cleaning concept, including vacuum suction system of powerful exhaust fan, more uniform alcohol injection system, more efficient cleaning method, can achieve the benign continuity of FinePitch printing.

Second, the automatic solder paste printing machine image positioning part

The image positioning of the automatic solder paste printing machine depends on the positioning algorithm. The positioning algorithm is also one of the core algorithms of the automatic solder paste printing machine. As the production efficiency of PCB boards is getting higher and higher, the electronic components on the board are getting smaller and smaller, and higher requirements are placed on the accuracy and speed of positioning. At present, the positioning algorithms of most automatic solder paste printers on the market are based on image gray scale, which is realized by autocorrelation matching. For copper-clad plates with good surface uniformity, the gray scale algorithm can do a good job of automatic positioning. However, the emergence of more and more tinplates, gold-plated panels, and flexible PCBs poses enormous challenges for grayscale positioning. Due to the tin plating, the surface uniformity of the gold-plated plate is not very good, and the reflectance is high, so that the imaging brightness of the Mark points on the PCB board is greatly different, and the false detection rate and the missed detection rate of the gray-scale positioning are increased. Due to the poor flatness of the surface of the flexible board, the image of the Mark point on the PCB also has a large difference in brightness, and the size and shape of the Mark point are also changed. These problems are difficult to overcome based on the gray level localization algorithm. . The geometry-based positioning algorithm can be well adapted to these problems of appeal.

Third, all solder paste printing machine release (Snap-off) mode

The quality of demoulding directly affects the printing effect. Generally, the automatic solder paste printing machine has two kinds of demoulding methods.

1、“Removal after scraping the knife first” is more common, mainly for simple PCB board.

2、“Scratch the blade after demoulding first”, use a thin PCB board, etc.

Solder paste printing machine specially designed three kinds of demoulding methods for the demolding requirements of different types of PCBs, suitable for PCB boards with different tin requirements:

1)Demoulding off the blade first.

2)First release the mold and then scrape the knife.

3)“The scraper is first detached, the pre-pressure value is maintained, and the mold is released again”.

Specially designed for 0.3BGA and small-distance demoulding to prevent tipping, plugging, and tin. The automatic solder paste printing machine is based on the use point of view: high speed stability is a fundamental requirement. The Mark point recognition of the printing machine is the primary factor of the machine: if the Mark point recognition difference often occurs Mark point recognition, but the manual intervention affects the production, and the corresponding operator needs to be added, which increases the use cost.

For example: 4000pcs/day of work plan output; if the printer recognizes Mark's ability to be 90%, there are 400 PCBs requiring manual intervention for at least 2 hours: 2 hours for OEM patch processing. . Secondly, if the cleaning effect is not good. With the development of SMT, FinePitch will have higher requirements for printing and cleaning. The cleaning is not clean and directly leads to problems such as the connection of tin and tin, which affects production and affects efficiency.