How to Identify Solder Paste Models

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Solder-mask color itself does not directly change paste soldering performance, but different mask colors differ in formulation, surface roughness, and heat resistance. Dark masks absorb heat faster, so board temperature runs higher during reflow, flux evaporates faster, and solder balls and voids are more likely. A rough mask surface increases paste adhesion and can induce bridging. Before running a new mask color, run an oven-profile test to verify paste definition and soldering quality.

The identification of Solder Paste models requires comprehensive judgment from multiple dimensions. First, look at the alloy composition of the solder paste, such as Sn63Pb37, Sn96.5Ag3.0Cu0.5 and other models. Different alloy ratios affect the melting point and fluidity. At the same time, pay attention to the activity level of the Flux in the solder paste. Low activity is suitable for precision components, while high activity is suitable for thick boards or PCBs with severe oxidation.

The packaging label of the solder paste model usually includes the manufacturer code, batch number and applicable temperature range. This information must be checked before production to avoid welding defects caused by model errors. For example, high-temperature solder paste may melt prematurely when used in Reflow Soldering, while low-temperature solder paste may not fully wet the pads.

In actual operation, the selection of solder paste models should also be combined with printing parameters, such as squeegee angle, pressure and stencil opening size. Different models of solder paste have differences in viscosity and slump resistance. If the process conditions are not matched, bridging or open soldering problems are likely to occur. At this time, it is necessary to verify and adjust the parameters through trial printing.

During the procurement process, special attention should be paid to the validity period and storage conditions of the solder paste. Some models are sensitive to humidity. If the shelf life is exceeded or the storage is improper, the flux will fail and affect the welding reliability. Therefore, the factory date and transportation records must be checked before warehousing.

When encountering a situation where the solder paste model is unclear, you can observe the solder joint state through a microscope or perform a thermogravimetric analysis test to confirm whether its composition meets the standard. At the same time, refer to the technical data provided by the manufacturer to ensure that the model is consistent with the equipment requirements, and avoid batch quality problems caused by model misjudgment.