Solder paste is an indispensable material in the process of soldering components and SMDs components to printed circuit boards. How is this material used? Join Hapoin to better understand the concept of welding cream? How to properly preserve solder paste after opening is in the following article.

What is solder paste?

Solder paste or solder paste, what is solder paste? This is a mixture of fluxes and alloy particles in a certain ratio depending on the user’s needs and is made in a smooth cream form. In particular, the welding alloy powder component accounts for 80% of the product volume.

Compared to lead bars and lead tin rolls, solder paste is more popular with factories. Because solder paste does not need to be melted, the process of welding components is faster and simpler.

In particular, solder paste has outstanding low wetting ability, which helps components adhere to the printed circuit board surface much better. From there, the finished product will meet the desired standards.

Kem hàn là gì

Tìm hiểu về kem hàn solder paste (Ảnh: Internet)

Classification of solder paste

What are the factors to classify solder paste? Based on the composition, solder paste can be divided into two main types: lead-free solder paste and lead-containing solder paste.

Solder paste contains lead

This type of solder paste is mainly composed of Tin (Sn) and Lead (Pb) mixed in a certain percentage. That ratio could be 37% Lead, 63% Tin or 40% Lead, 60% Tin.

Today, this type of solder paste has been limited in use because its ingredients contain lead. When welding, toxic fumes will be produced that are dangerous to human health.

Lead-free solder paste

This is a common type of solder paste, very commonly used. As the name suggests, this type of solder paste does not contain lead. This will ensure safety for users’ health.

The main ingredient of lead-free solder paste is tin. At that time, lead will be replaced by copper and silver metals mixed in a standard ratio of 0.5% Copper, 3% Silver and 96.5% Tin.

In addition, solder paste can also be classified according to the flux used as follows:

  • Rosin solder paste: This is a type of solder paste made from resin, naturally extracted from pine trees. This type can clean the flux after soldering if necessary using a solvent such as chlorofluorocarbon.
  • Solder paste water-soluble flux: This is a type of flux made of glycol-based substances and organic materials. Many cleaning agents can be used when using this type of flux.
  • Solder paste does not require cleaning: Contains plastic ingredients and varying levels of residue. When used, there will be no need to use cleaning agents, but the assembly environment must be clean..


Classification of lead-free solder paste TAMURA TLF-204-93IVT(SH) distributed by Hapoin

What are the precautions when using solder paste?

When using solder paste, you should pay attention to the following things so that the solder paste can maximize its effectiveness:

  • Solder paste should be stored in a cold place, at a temperature between 2 and 10 degrees Celsius
  • After opening the lid, if the usage interval is more than 1 hour, you need to close the lid again. When using, open the lid.
  • When taking the solder paste out of the freezer, you need to leave the solder paste at room temperature for 2 hours before stirring the solder paste well. Only stirring the solder paste for 2 to 3 minutes is enough for the solder paste to return to its original properties, but do not stir for too long.
  • Before stirring the solder paste, if you see the surface of the solder paste forming small lumps, you need to remove those lumps before stirring.

How to choose suitable welding materials

To choose suitable welding materials in terms of both price and quality, engineers will usually go through the following three consideration stages:

  • First: Consider the composition of solder paste. When choosing a solder alloy, the main factors to note are the lead composition, the adhesion ability of the paste, the melting temperature and the diameter of the alloy particles.
  • Second: The stage of selecting solder flux in solder paste, because this is the ingredient that reduces surface tension and makes the solder joint beautiful. Conventional names for welding fluxes will help users easily identify their ingredients and specifications. Each type of welding aid will have different effectiveness and limitations. Therefore, in order not to affect the quality of the weld, it is necessary to choose the correct composition of the solder paste. There are 5 main types of flux based on industrial grade: R, RA, RMA and WS.
  • Finally: Choose a product with special solder flux suitable for each use need. These are the ability to limit the excess of solder flux, reduce solder paste overflow, surface adhesion ability, vertical filling ability, Halide-free, reverse welding speed, glow when exposed to UV rays,…

Kem hàn TAMURA TLF-204-NH(20-36)

Halogen-free solder paste is increasingly preferred by factories

Where to buy reputable and quality soldering cream?

After learning what solder cream is, customers who want to buy solder cream but have not yet found a quality, reputable place to buy it can come to Hapoin Vietnam. We are a unit specializing in providing genuine solder paste at good prices. Soldering paste products are imported and distributed directly from abroad by Hapoin, with full inspection documents to help customers feel secure when buying.

>>> You may be interested in: What is SMT


Above, Hapoin joined readers to find the answer to the question of what soldering cream is and how to use it. Hopefully, through this article we have provided useful information about solder paste materials. If you have any questions, please contact us for quick advice.

Jasmine Wu – Hapoin

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