Solder Paste and Its Application in SMT
Solder Paste and Application in SMT – Learn What is Solder Paste & How to Use it to Solder SMD Electronic Components to PCB.
Here we will learn about Solder Paste and its Application in SMT. What is Solder Paste & How to Use?
What is Solder Paste?
Solder paste is simply a suspension of fine solder particles in a flux vehicle. In electronic industry, solder paste is used in Surface Mount Technology (SMT) to solder SMD Electronic Components 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.
Lead-Free Solder Paste
With the implementation of RoHS (Restriction of Hazardous Substances) in the Electronics Industry by the European Union and Many other countries, most electronic companies are shifting to Lead Free. Lead Free Solder Wire and Solder Paste are manufactured using different composition and ratio. But the most popular and widely used composition and ratio is SAC (Tin Silver Copper) in the Ratio 96.5% Tin + 3.0% Silver and 0.5% Copper.
Lead-free solder has higher melting point than the conventional 63/37 or 60/40 Tin-Lead Solder. Also the solder joints are not as shiny as tin-lead solder.
Screen Printer Machine
Some of the major features to consider when selecting screen printer for solder cream are the maximum size of the SMT Printed 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 made for paste dispenser, screening and stenciling for pastes on substrates. Each method of dispensing solder cream 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.
Stencils for Solder Paste Application
There are three main ways of making stencils:
- 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 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 pastes, there is not need to clean the board after soldering. Water soluble solder pastes are easily soluble in water with no harm.
Alpha Cookson is a Leading Manufacturer and Supplier of all Types of Soldering Material including, Solder Wire, Paste and Bar.
How to Get the Best Solder Joints
In order to achieve good printing results, a combination of the right soldering material, the right tools and the right process are necessary.
Although suppliers like PCBA Tools are 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, SMT Equipment, and application methods are not sufficient by themselves to ensure acceptable results.
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