PCBA Tech - SMT patch solder paste printing affects production quality

There are many electronic component pin soldering points on the PCB, which are called pads (PAD). In the SMT patch process, in order to apply the solder paste on a specific pad, a steel plate corresponding to the position of the pad needs to be made and installed on the solder paste printer. By monitoring and fixing the PCB position of the substrate, ensure that the steel plate mesh hole is the same as the pad position on the PCB. After the positioning is completed, the squeegee on the solder paste printer is moved back and forth on the stencil, and the solder paste passes through the mesh on the steel plate and covers the specific pads (PAD) of the PCB to complete the solder paste printing.

Printing solder paste on the PCB circuit board and then connecting the electronic components to the PCB circuit board through a reflow oven is a method commonly used in the electronics manufacturing industry today. The printing of solder paste is a bit like painting on a wall. The difference is that in order to apply the solder paste to a specific location and control the amount of solder paste more accurately, a more precise special steel plate (Stencil) must be used to control it. Printing of solder paste.

SMT patch solder paste printing

The quality of solder paste printing is the basis for the quality of PCB soldering. The position and amount of solder paste are more important. It is often seen that the solder paste is not printed well, causing solder short and empty soldering (Solder Empty). ) And other problems appear. However, if you really want to print the solder paste, you have to consider the following factors:

Squeegee: Solder paste printing should choose the appropriate squeegee according to the characteristics of different solder paste or red glue. At present, the squeegee used for solder paste printing is made of stainless steel.

Scraper angle: The angle at which the squeegee scrapes the solder paste.

Squeegee pressure: The pressure of the squeegee will affect the volume of solder paste. In principle, under other conditions unchanged, the greater the pressure of the squeegee, the less the amount of solder paste will be. Because of the high pressure, it is equivalent to compressing the gap between the steel plate and the PCB circuit board.

Squeegee speed: The speed of the squeegee will directly affect the shape and amount of solder paste printing, as well as the quality of solder. Generally, the speed of the squeegee is set between 40-80mm/s. In principle, the speed of the squeegee must match the viscosity of the solder paste. The better the fluidity of the solder paste, the faster the squeegee speed, otherwise it is easy to seep.

SMT is a new type of electronic assembly technology and one of the key process technologies in the manufacture of electronic products. With the formulation of "Made in China 2025", intelligent manufacturing, as the main direction of attack, is the core technology of the new round of industrial revolution, and has become a national strategy. The integration of SMT and intelligent manufacturing concepts to establish an efficient, agile, flexible and resource-sharing SMT intelligent manufacturing model is the future development direction of the electronic product manufacturing industry and an important way to improve the manufacturing capabilities and levels of SMT products.