Solder paste printing is a complex process in SMT surface mount processing, which can easily lead to some drawbacks and affect the quality of the final product. So to avoid frequent malfunctions during printing,

1、 Pulling the tip, usually the solder paste on the solder pad will form a small hill shape after printing.

Reason for occurrence: It may be caused by gaps in the scraper or excessive viscosity of the solder paste.

Avoidance or solution: For SMT surface mount processing, adjust the gap between the scraper appropriately or select a solder paste with suitable viscosity.

2、 The solder paste is too thin.

The reasons for this are:

1. The template is too thin;

2. The pressure of the scraper is too high;

3. Poor fluidity of solder paste.

Avoidance or solution: Choose a template with appropriate thickness; Select solder paste with appropriate particle size and viscosity; Reduce the pressure of the scraper.

3、 After printing, the thickness of solder paste on the solder pads varies.

Reason for occurrence:

1. The uneven mixing of solder paste results in uneven particle size.

2. The template is not parallel to the printed board;

Avoidance or solution: Mix the solder paste thoroughly before printing; Adjust the relative orientation between the template and the printed circuit board.

4、 The thickness is different, and there are burrs on the edges and surface.

Reason for occurrence: It may be due to the low viscosity of the solder paste and rough walls of the template openings.

Avoidance or solution: Choose solder paste with slightly higher viscosity; Check the etching quality of the template holes before printing.

5、 Fallen. After printing, the solder paste sinks into both ends of the solder pad.

Reason for occurrence:

1. The pressure of the scraper is too high;

2. The positioning of the printed board is not secure;

3. The viscosity or metal content of the solder paste is too low.

Avoidance or solution: Adjust stress; Fix the printed circuit board from the beginning; Select solder paste with appropriate viscosity.

6、 There are some places on the solder pad where solder paste is not printed.

The reasons for this are:

1. Blocked openings or some solder paste sticking to the bottom of the template;

2. The viscosity of solder paste is too low;

3. There are large-sized metal powder particles in the solder paste;

4. Scraper wear.