Abstract: According to the present disclosure, a measuring method of liquid mixture purity includes steps as follows. A storage tank is provided, wherein the storage tank is configured for storing a liquid mixture including formic acid and water. A calculating unit is provided, wherein a plurality of formic acid purity values are saved in the calculating unit. A pressure-decreasing and heating step is performed by reducing a pressure of the storage tank and heating the storage tank. A measuring step is performed by measuring in the inner space of the storage tank to obtain a pressure value, and measuring the liquid mixture simultaneously to obtain a temperature value. A calculating step is performed by inputting the pressure value and the temperature value into the calculating unit, wherein the calculating unit outputs one of the formic acid purity values corresponding thereto.

Abstract: A processing method of formic acid soldering includes providing a solder, performing a formic acid providing step, performing a soldering step and performing a cooling step. The solder is disposed at a soldering object. In the formic acid providing step, a water-containing formic acid vapor extracted from a formic acid source is introduced to a soldering object so as to form a water-containing formic acid atmosphere surrounding the soldering object. In the soldering step, the solder and the soldering object are soldered in the water-containing formic acid atmosphere at a soldering temperature so as to form a soldered object with high temperature. In the cooling step, the soldered object with high temperature is cooled by a cooling method so as to form a soldered object. A range of a moisture content of the formic acid source is greater than or equal to 0.1 wt % and less than 15 wt %.