Solder pasteThe printing quality has a significant impact on the quality of surface mount products, and then other links will be affected. So why do we receive these situations? They mainly include: solder paste printing, precise surface mount technology, and reflow soldering. In solder paste printing, there are three important parts: solder paste, steel mesh template and printing equipment. How can we solve these problems Now, let's take a look at what the solder paste manufacturer's editor has to say

Factors affecting solder paste viscosity:

1The influence of alloy powder content in solder paste on viscosity - The increase of alloy powder in solder paste leads to an increase in viscosity. 

2The influence of the particle size of solder paste alloy powder on viscosity - Viscosity decreases as the particle size increases; 

3Fine particle solder paste has better printability, especially for high-density and narrow-spacing products. Due to the small opening size of the steel mesh, small particle alloy powder must be used; otherwise, it will affect the printing demolding. 

4The advantages of small-particle alloy powder: good printability and high clarity of printed graphics. 

5The disadvantages of small-particle alloy powder: It is prone to edge collapse and those with a large surface area are easily oxidized.

The expiration date of solder paste and its storage and usage environment:

1,  Generally, when the solder paste is unopened,0-10℃It can be saved under certain conditions6After opening, it should be used up as soon as possible.

2,  The application environment of solder paste is: requiredSMTThe temperature of the room is20-26℃Humidity is40-60%;

3,  The storage time of unopened solder paste under environmental temperature and humidity conditions≤48Hours;

4,  The storage time of solder paste under environmental temperature and humidity conditions after opening the lid≤18Hours;

5,  The usage time on the steel mesh≤12Hours;

6,  The time that solder paste stays on the line after printing≤2Hours;

7,  The time from opening the can to reflow soldering≤18Hours.

Defects caused by solder paste:

1Not dipped soldered

1.1  The flux activity is not good;

1.2  The metal particles were oxidized very severely.

2.    There is no rolling in the printing

2.1  The flow is not appropriate, for example: the viscosity and thixotropic index are not suitable;

2.2 The viscosity is not appropriate;

3Bridge

3.1 Solder paste collapse

3.2 Insufficient solder

3.3 Due to the large size of the alloy powder particles, incorrect shape or non-printability, the solder paste blocks the holes of the template.

4Tin ball

4.1 Solder paste collapse

4.2 Solvent splashes out during reflow soldering;

4.3 Oxidation of metal particles.

The main factors affecting the quality of solder paste printing

1Firstly, the quality of the steel mesh: The thickness of the steel mesh and the opening size determine the printing quality of the solder paste. Excessive solder paste can cause bridging, while insufficient solder paste can result in insufficient solder paste or false soldering. The shape of the openings in the steel mesh and whether the walls of the openings are smooth also affect the demolding quality.

2Secondly, the quality of solder paste: the viscosity of solder paste, the rolling property of printing, and the service life at room temperature will all affect the printing quality.

3Printing process parameters: There is a certain restrictive relationship among the speed and pressure of the squeegee, the Angle between the squeegee and the screen plate, and the viscosity of the solder paste. Therefore, only by correctly controlling these parameters can the printing quality of solder paste be guaranteed.

4In terms of equipment accuracy: When printing high-density narrow-pitch products, the printing accuracy and repeat printing accuracy of the printing machine will also have a certain impact.

5Environmental temperature, humidity, and environmental hygiene: Excessively high environmental temperature will reduce the viscosity of solder paste. When the humidity is too high, the solder paste will absorb moisture from the air. When the humidity is too low, it will accelerate the evaporation of solvents in the solder paste. Dust in the environment mixed into the solder paste can cause defects such as pinholes in the solder joints.

From the above introduction, we can see that there are many factors affecting the printing quality, and solder paste printing is a dynamic process. Therefore, we need to understand some of the main problems and factors in the implementation process, so as to solve them and print better products. To master the relevant solder paste,Lead-free solder pasteWe warmly welcome all friends to consult Shenzhen JJY Industrial Technology Co., Ltd. for problems related to solder paste and other soldering methods. Let's learn and grow together!