How to solve the problem of burrs and tarnish after soldering solder paste?

The problem of burrs and tarnish after solder paste soldering can be caused by a variety of factors, here are some specific solutions:

I. For the burr problem

Choose the right solder paste:

The viscosity of solder paste is one of the key factors affecting soldering quality.If the viscosity of solder paste is low, it may lead to burrs on the edges after soldering.Therefore, solder paste with the right viscosity should be selected to ensure soldering quality.

If the solder paste is found to have quality problems, such as uneven particles and the presence of impurities, it may also lead to burrs.In this case, the solder paste supplier should be communicated with to replace the solder paste with better quality.

Optimising stencil quality:

The roughness of the stencil aperture wall has a significant impact on solder quality.If the aperture wall of the stencil is rough, it may result in the solder paste not being evenly distributed during the printing process, thus creating burrs.Therefore, before stencil acceptance, tools such as a magnifying glass should be used to check the degree of polishing of the stencil aperture walls to ensure that they are smooth.

Regular cleaning and maintenance of the stencil to avoid residual solder paste or other impurities on the bottom of the stencil to reduce the generation of burrs.

Improve the PCB fabrication process:

If the plating on the PCB is too thick or the hot air levelling is poor, it may also lead to uneven edges and burrs after soldering.Therefore, you should communicate with the PCB manufacturer and ask it to improve the process, such as using gold plating, OSP and other pad coating processes, in order to improve the soldering quality of the PCB board.

Adjust the printing parameters:

Parameters such as printing speed, squeegee pressure and print gap all affect the quality of solder paste printing.These parameters should be adjusted according to the actual situation to keep them within the appropriate range to ensure that the solder paste can be evenly printed on the PCB, thereby reducing the generation of burrs.

II. Responding to tarnishing problems

Strengthen the cleaning work:

Before welding, the cleanliness of the PCB board, stencil and other components should be ensured.Cleaning agents, ultrasonic cleaning and other methods can be used to clean the PCB board and stencil to remove surface oil, dust and other impurities.

During the printing process, if solder paste or other impurities are found remaining at the bottom of the stencil, it should be cleaned and replaced in time.

Optimise the printing and soldering environment:

The control of workshop temperature and humidity also has a great impact on the quality of welding.Workshop temperature should be maintained in the appropriate range (usually 22-28 degrees Celsius), humidity control in the range of 40% -60% to reduce the possibility of solder paste moisture and oxidation.

At the same time, air circulation and cleanliness in the workshop should be maintained to avoid the influence of dust, oil and other impurities on soldering quality.

Improve the operation skill level:

The skill level of the operator also has a great impact on the quality of soldering.The training and education of operators should be strengthened to improve their operating skill level and quality awareness.At the same time, a detailed process manual should be developed, and the operator training and guidance to ensure that they are familiar with and master the process and operating specifications.

In conclusion, to solve the problem of burrs and tarnish after soldering of solder paste, we need to start from many aspects, including choosing the right solder paste, optimising the quality of the stencil, improving the PCB production process, adjusting the printing parameters, strengthening the cleaning work, optimising the printing and soldering environment, and improving the level of operating skills.Through the combined application of these measures, soldering quality and product reliability can be significantly improved.