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Paste yield point
Not to be confused with the stress-strain curve of metals, the term is applicable particularly to solder paste. As the graph shows, the yield point is located on the shoulder of the flow curve of solder paste, i.e. the curve of shearing stress (Γ) versus the shear rate (γ). Results are more reliable when operating at a low shear rate of about 50 mm/sec. It should be noted that high yield strength is not always correlated with the viscosity of the paste. A body can have high yield strength and high viscosity in the same time, but the opposite may happen as well.