The Introduction of Dispensing Solder Paste
Dispensing solder paste is filled in the syringes. The solder paste releases through the dispensing needle and contacts the pads. Due to the different process methods, the dispensing solder paste cannot place in a jar like the printing solder paste. Instead, it stores in a syringe. Hence, some people call it a syringe solder paste. However, the solder paste stored in a syringe is not necessarily a dispensing solder paste. The coating of solder paste patterns of dots, lines, and figures can be realized by adjusting the dispensing process.
Dispensing solder paste classification
1. By alloy: SAC305 series, SnBiAg series, AuSn series, BiX series, etc.;
2. By particle size: T2-T10;
3. By melting point (or reflow temperature): high-temperature dispensing solder paste, medium-temperature dispensing solder paste, and low-temperature dispensing solder paste;
4. By flux: zero-halogen, halogen-free, halogen-containing dispensing solder paste;
5. By post-soldering cleanability: water-soluble no-clean, solvent-soluble dispensing solder paste;
6. By viscosity: high-viscosity, medium-viscosity, and low-viscosity dispensing solder paste;
7. By carrier: rosin-based and epoxy-based dispensing solder paste;
8. By other criteria.
Dispensing solder paste selection
The solder paste has excellent sphericity, a smooth surface, and outstanding rheology. Since the dispensing solder paste needs to be added on the pad through the dispensing needle, the dispensing solder paste should maintain superior rheology during the long-term dispensing process. The dispensing needle cannot be blocked. In addition, the dispensing solder paste needs to maintain its shape.
Reflow profile of dispensing solder paste
The reflow profile of dispensing solder paste is similar to that of printing solder paste. A typical reflow profile is shown in the figure below:
SAC305 Dispensing Solder Paste Reflow Profile
SnBiAg0.4 Dispensing Solder Paste Reflow Profile
With the alloy particle size and flux composition changes, the reflow curve settings of different solder pastes will be adjusted accordingly to achieve the best soldering effect.