What is the difference between solder paste, solder wire and solder bar?

Solder paste, solder wire and solder bars each play an important role in the soldering process.

The differences between them are mainly in the following areas:

Shape and packaging:

① Solder Paste: is a paste material carefully made from solder alloy powder, usually exhibiting a fine grey or off-white texture. It is commonly packaged in 500g sealed tins for easy storage and use. In addition, customised packaging options are available to meet specific needs, such as small and convenient syringe packs in sizes ranging from 10g, 30g, 100g and even 1kg, providing users with even more flexibility and variety.

② Tin wire: It is coiled into a spiral shape similar to that of iron wire, which is compact and easy to use. This wire material is easy to store, carry and handle, and is one of the most important materials commonly used in electronic soldering.

③ Strips: These are in the form of strips and are usually packaged in boxes with a weight of approximately 20kg per box. The regular shape of the bars and the sturdy box design make the bars more stable and safer during storage and transport, and meet the needs of large-volume use.

The biggest difference between them is the different solder profiles and applications:

① Solder Paste: mainly composed of flux and tin alloy powder, it is a key material directly applied in the soldering process. Depending on its composition, solder paste can be subdivided into two types: leaded solder paste and lead-free solder paste. It has excellent wetting properties and contains a flux component that effectively isolates air and prevents metal oxidation. In the field of electronics manufacturing, solder paste is widely used in the SMT (surface mount technology) process, and is also suitable for a variety of soldering methods such as hot air soldering, hotbar soldering and laser soldering.

② Solder wire: In early applications, it did not contain a flux component, however, with advances in technology and refinement of the process, modern wire has incorporated flux, which allows for the ease of direct soldering. In manual soldering, it needs to be heated to soften it before it is applied to the soldered part by means of an electrode. It is also widely used for soldering on production lines and in the manufacture of organic solar cells, printed circuit boards, and so on.

③ Tin Stick: It is made of pure tin or tin alloy material and does not contain flux components. Therefore, in the wave soldering process, it is necessary to add additional flux before soldering to ensure the smooth progress of the soldering process. It can be clearly classified into two categories, leaded and lead-free solder bars, and is widely used in a variety of soldering processes such as dip soldering, DIP (dual in-line package) and wave soldering. This material is known for its excellent wettability, fluidity, ease of tinning, solder joints show a bright and full appearance, and has a strong oxidation resistance.

To sum up, solder paste, tin wire and solder bar in the soldering process each has its own unique shape, composition and use, they play an irreplaceable role in their respective fields, with the development trend of electronic devices thin, light, short, refined, the application of solder paste is becoming more and more widespread.

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