How to improve the solder creep of solder paste during the soldering process?

Solder paste creeping tin for printing quality and soldering effect is critical.To improve the solder paste in the soldering process to climb the tin, you can start from the following aspects:

1. the paste selection and processing

Solder paste composition and quality:

Select the solder paste containing high activity flux, which helps to improve the effect of climbing tin.

Ensure that the solder paste has not expired, to avoid the use of expired solder paste caused by the decline in flux activity.

Solder paste viscosity and particles:

The viscosity of the solder paste should be moderate, too viscous or too thin will affect the crawling tin.

The uniformity and size of the paste particles also affect the printing performance, generally recommended that the diameter of the paste particles for the stencil mesh size of 1 / 5, the maximum diameter can not be greater than 0.05mm.

Solder paste warming and mixing:

Solder paste should be sufficiently warmed and stirred before use to ensure its uniformity and fluidity.

2. the printing process optimisation

Stencil design:

The diameter and shape of the openings in the stencil should be reasonably adjusted according to the design of the pad, the general diameter of the openings is less than one-third of the size of the pad to ensure that the solder paste can smoothly seep down and cover the pad.

Aperture diameter minus the foot diameter, in the experiments to 0.3mm ~ 0.5mm is more appropriate.

Printing pressure and speed:

The pressure of the printing machine should be balanced, scraper pressure and scraping speed should be based on the product characteristics of a reasonable setting, generally a piece of PCB back and forth printing control in 5 ~ 10 seconds.

Too little pressure or scraping speed is too slow will lead to too much solder paste printing, affecting the climbing tin.

Printing temperature and humidity control:

Solder paste printing temperature and humidity should be kept stable, the temperature difference between high and low can not exceed 5 degrees, 20-25 ℃, humidity 40-60% RH for easy, in order to avoid the solder paste due to temperature changes in performance.

3. the PCB board and component preparation

PCB board flatness:

The flatness of the PCB board has an important impact on the quality of solder paste printing, should ensure that the PCB board without deformation or warping.

Components and pads:

Components and pads should be kept clean, no oxidation or pollution.

Pad design should be reasonable, the hole above the pad should be small, below the pad should be large, do not have all the pad grounded to ensure that the solder paste can climb smoothly to the edge of the pad.

4. the environmental control and operating specifications

Environmental humidity and temperature:

Printing workshop should maintain a constant temperature and humidity to avoid solder paste moisture or oxidation.

Operation specification:

Operators should be proficient in the printing process, follow the operating specifications to avoid human factors lead to printing quality problems.

5. Follow-up soldering process

soldering temperature and time:

Soldering temperature should reach the melting point of the paste above, to ensure that the paste can fully melt and wet the pad.

Soldering time should be long enough, generally recommended soldering time to be more than 3.5 seconds to ensure that the solder paste can fully climb to the edge of the pad and the formation of a solid welded joint.

Soldering atmosphere:

The soldering process should maintain a good atmosphere to avoid the influence of oxygen and other harmful gases on the soldering quality.

Summary

To improve the solder paste in the printing process to climb tin need to be from the solder paste selection and processing, printing process optimisation, PCB boards and components preparation, environmental control and operational specifications, as well as subsequent welding process with a number of aspects.Through comprehensive consideration of these factors and take corresponding measures, can significantly improve the solder paste climbing tin and improve the printing quality and soldering effect.