Solder Paste and Its Application in SMT

Solder Paste and Its Application in SMT

Publish Date:2016-09-29 15:20:50 Clicks: 40

Solder Paste and Its Application in SMT

Solder paste or solder cream is simply a suspension of fine solder particles in a flux vehicle. In electronics industry, solder paste is used in surface mount technology (SMT) to solder SMDs on to the printed circuit board. The composition of the particles can be tailored to produce a paste of the desired melting range. Additional metals can be added to change paste compositions for specialized applications. Particle size and shape, metal content and flux type can be varied to produce pastes to varying viscosity.

Solder Paste Screen Printer

Some of the major features to consider when selecting screen printer for solder paste are the maximum size of the circuit board that can be handled, controls of accurate screen alignment and repeatability of print, and the board hold-down mechanism. Considerable progress has been solder paste dispenser, screening and stenciling for pastes on substrates. Each method of dispensing solder paste has its own pros and cons but the most widely used method is stenciling for both rework and large scale production. Vastex is a well known manufacturer and supplier of screen printing equipment.

Solder Paste

Stencils for Solder Paste Application

There are three main ways of making stencils for solder paste:

Chemical etching

Laser cutting


Chemical etching is the oldest, most widely used, and least expensive option. Laser cutting and electroforming, especially the latter, find appeal in applications where precision is paramount. In addition to the type of stencil, the type of squeegee blade is very important. Metal blade squeegees are widely used because they require less maintenance than rubber squeegees.

Availability of Solder Paste

Solder Paste

Solder Paste

Solder paste is available in both leaded (with lead) and lead-free (with no lead) forms. It can be no-clean or water soluble. With no-clean solder paste, there is not need to clean the board after soldering. Water soluble solder paste is easily soluble in water with no harm.

How to Get the Best Solder Joints from Solder Paste Application

In order to achieve good solder paste printing results, a combination of the right solder paste material, the right tools and the right process are necessary. Kester is a trusted brand in manufacturing solder paste and other soldering material including solder wire, solder bar, solder flux etc. Although the supplier is essentially responsible for providing the desired solder paste and screens or stencils and the squeegee blades, the user must control process and equipment variables to achieve good print quality. Even the best solder paste, equipment, and application methods are not sufficient by themselves to ensure acceptable results.

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