PCB News - pcb manufacturer: solder paste

PCB manufacturer: solder paste

Solder paste is also called solder paste, the English name is solder paste, which is gray paste. Solder paste is a new type of soldering material that emerges with SMT. It is a paste mixture formed by mixing solder powder, flux, and other surfactants and thixotropic agents. Mainly used for the soldering of electronic components such as PCB surface resistance, capacitors, and ICs in the SMT industry.

Composition of solder paste
Generally speaking, the composition of solder paste can be divided into two major parts, namely flux and solder powder (FLUX & SOLDER POWDER).

The role of solder paste
1. Activating agent (ACTIVATION): This component mainly plays the role of removing oxidized substances on the surface of the PCB copper film pad and the soldering part of the part, and has the effect of reducing the surface tension of tin and lead;

2. Thixotropic agent (THIXOTROPIC): This ingredient mainly adjusts the viscosity of solder paste and printing performance, and plays a role in preventing tailing and sticking during printing;

3. Resin (RESINS): This component mainly plays a role in increasing the adhesion of the solder paste, and it also protects and prevents the PCB from re-oxidation after soldering; this component plays an important role in fixing the parts;

4. Solvent (SOLVENT): This component is the solvent of the flux component, which plays a uniform role in the stirring process of the solder paste, and has a certain impact on the life of the solder paste.

How to use solder paste
When the solder paste is taken out from the solder paste refrigerator, it should be opened in its sealed state and waited for it to return to room temperature, about 3-4 hours; if it is opened just after being taken out of the refrigerator, the existing temperature difference will cause the solder paste to form Dew and condensate into water, which will cause solder beads during reflow soldering; however, heating cannot be used to bring the solder paste back to room temperature. The rapid temperature rise will deteriorate the performance of the flux in the solder paste, thereby affecting the soldering effect. . This is also a problem that solder paste manufacturers should pay attention to during use. It may cause the separation of the components in the solder paste during refrigerated storage. Stir the solder paste for 1-2 minutes before use to fully mix it evenly. Do not mix leftover solder paste with new solder paste in the same package. The solder paste should be re-sealed when it is not needed. When the bottle cap cannot be sealed and stored well, please replace the inner lining of the bottle cap to ensure the seal as much as possible.

Precautions for the use of solder paste
1. Squeegee pressure: to ensure that the edges of the printed solder joints are clear, the surface is flat, and the thickness is appropriate;

2. Scraper speed: to ensure that the solder paste is rolling rather than sliding relative to the squeegee, under normal circumstances, 10-20mm/s is appropriate;

3. Printing method: contact printing is appropriate;

In addition, the solder paste should be fully stirred during use, and then added to the printing screen according to the set amount of printing. If the spotting process is adopted, the amount of spotting must be adjusted.

In the case of long-term printing, the volatilization of the flux in the solder paste will affect the release performance of the solder paste during printing. Therefore, the container for storing the solder paste cannot be reused (only for one-time use). The remaining solder paste on the board should be stored in other clean containers. When using it next time, check whether there is agglomeration or solidification in the remaining solder paste. If it is too dry, add the solder paste provided by the supplier to dilute Use after diluting the agent.

Operators should pay attention to avoid direct contact between the solder paste and the skin when working. In addition, the printed board should be soldered within a few days. Remember, the best conditions for solder paste workplaces are: temperature 20-25°C, relative humidity 50-70%, clean, dust-free, and anti-static.

How to preserve solder paste
Solder paste should be stored in a sealed form in a constant temperature and humidity freezer (note that refrigeration is not a rapid freezing). There are special freezers for solder paste on the market. 6 can be stored under the condition of 2 degree Celsius～8 degree Celsius Months, if the temperature is too high, after the alloy powder in the solder paste has not chemically reacted with the flux, the viscosity and activity will be reduced, which will affect its performance; if the temperature is too low, the resin in the flux will crystallize, which will deteriorate the shape of the solder paste. . In the storage process, it is more important to pay attention to the problem of maintaining a "constant temperature". If the solder paste continuously undergoes different temperature changes from various environments in a relatively short period of time, it will also cause the solder paste The performance of the medium flux changes, which affects the soldering quality of the solder paste.

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