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What is solder paste? Its composition and precautions for use
2025-11-24
Solder paste is an indispensable material in the process of soldering SMD components and parts onto printed circuit boards. How is this material used? Let's find out more about the concept with Hapoin. What is tin solder paste? The proper way to store opened solder paste is described in the following article.
What is tin solder paste?
What is solder paste, or cream-type solder? It is a mixture consisting of fluxes and alloy particles in a specific ratio tailored to the user's needs, and it is manufactured in the form of a smooth cream. Among these components, the solder alloy powder makes up as much as 80% of the product's weight.
Compared to lead rods, lead-tin solder in coil form is more favored by manufacturers. This is because solder paste does not need to be melted, making the component soldering process faster and simpler.
In particular, the solder paste exhibits outstanding low-wetting capability, which helps components adhere much better to the surface of the printed circuit board. As a result, the finished products will meet the desired standards.
Welding paste classification
Factors for classification What is tin solder paste? Based on their composition, soldering pastes can be divided into two main types: lead-free soldering paste and lead-containing soldering paste.
Lead-containing soldering paste
This is a soldering alloy whose main components are Tin (Sn) and Lead (Pb) mixed in specific percentages. These percentages could be 37% Lead and 63% Tin, or 40% Lead and 60% Tin.
Today, this type of soldering paste has been restricted in use because its composition contains no lead elements. During soldering, it produces toxic fumes that pose a health hazard to humans.
Lead-free soldering paste
This is a common type of soldering paste, widely used. As the name suggests, this soldering paste does not contain lead in its composition. This ensures the safety of the user's health.
The main component of lead-free solder paste is tin. In this case, lead is replaced by copper and silver metals mixed in a standard ratio of 0.5% copper, 3% silver, and 96.5% tin.
In addition, soldering paste can also be classified according to the flux used as follows:
- Rosin solder paste: This is a soldering flux made from rosin, a natural extract from pine trees. If necessary, this type can be used to remove flux residues after soldering by employing solvents such as chlorofluorocarbons.
- Water-soluble solder paste: This is a flux made from glycol-based substances and organic materials. Many substances can be used to clean it when this type of flux is employed.
- Solder paste does not need to be cleaned: It contains plastic components and varying degrees of residue. When using it, no cleaning agents are required, but the installation environment must be kept clean.
What are the precautions when using soldering paste?
When using solder paste, please pay attention to the following points to ensure that the solder paste can achieve maximum effectiveness:
- The soldering paste should be stored in a cool place, at a temperature between 2 and 10 degrees Celsius.
- After opening the lid, if the interval between uses exceeds one hour, the watch must be closed again; when using it, open the lid.
- When taking the solder paste out of the freezer, it is necessary to let the solder paste sit at room temperature for 2 hours before stirring it thoroughly. It is sufficient to stir the solder paste for only 2 to 3 minutes to restore its original properties; avoid stirring for too long.
- Before stirring the solder paste, if you notice small clumps forming on the surface of the solder paste, remove those clumps before stirring.
How to choose the right welding material
To select welding materials that are suitable in terms of both price and quality, engineers usually go through the following three stages of consideration:
- First: Examine the composition of solder paste. When selecting solder alloys, the key factors to consider are the lead content, the adhesion capability of the paste, the melting temperature, and the diameter of the alloy particles.
- Monday: The stage of selecting fluxes in soldering paste is crucial, as these components help reduce surface tension and produce smooth, shiny solder joints. Conventionally named fluxes allow users to easily identify their composition and specifications. Each type of flux has its own unique effectiveness and limitations. Therefore, to avoid compromising the quality of the solder joint, it's essential to carefully select the appropriate components of the soldering paste. There are five main types of fluxes classified according to industrial standards: R, RA, RMA, and WS.
- Finally: Choose products with special fluxes that are tailored to meet specific application needs. These include the ability to minimize flux excess, reduce solder paste overflow, enhance surface adhesion, provide vertical filling capability, be halide-free, offer reverse welding speed, and emit light upon exposure to UV rays...
Where can I buy reliable and high-quality soldering paste?
After having studied What is tin solder paste? Customers who are looking to buy welding flux but haven't yet found a reliable and reputable supplier can come to Hapoin Vietnam. We specialize in providing genuine welding flux at competitive prices. The welding flux products are directly imported and distributed by Hapoin from overseas, and come with full certification documents, ensuring customers can shop with peace of mind.
Conclusion
Above, Hapoin has explored the answer to the question with readers. What is tin solder paste? as well as their usage. We hope that through this article, we have provided you with useful information about welding flux materials. If you still have any questions, please contact us for quick consultation.
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