JPH0468359B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a cleaning solvent suitable for removing flux and dirt from printed circuit boards, degreasing, and the like. [Prior art] Conventionally, as a cleaning solvent for printed circuit boards, 1,
Azeotropic mixed solvent consisting of 1,2-trichloro-1,2,2-trifluoroethane (Freon 113), ethanol and nitromethane (Japanese Patent Application Laid-open No. 50-80983
), or an azeotropic mixed solvent consisting of Freon 113, methanol and nitromethane (JP-A-51-
No. 44575) has been widely used. However, the above-mentioned three-component mixed solvent does not necessarily exhibit a satisfactory cleaning effect, and often produces a white residue or an ionic residue, which may cause trouble. Furthermore, in recent years, cleaning solvents that can replace Freon 113 have been desired. [Problem to be solved by the invention] The purpose of the present invention is to solve the problem without using Freon 113.
To provide a cleaning solvent that can be used as is in a cleaning device for Freon 113, has high cleaning power, and does not produce white residue or ionic residue on objects to be cleaned. [Means for Solving the Problems] The present invention is a cleaning solvent characterized by comprising 1,1-dichloro-2,2,2-trifluoroethane and dimethoxymethane. The mixing ratio of 1,1-dichloro-2,2,2-trifluoroethane (hereinafter referred to as Freon 123) and dimethoxymethane to be mixed in the cleaning solvent of the present invention is preferably 5:95 to 70:30 by weight. teeth
40:60 to 60:40. If the proportion of Freon 123 is less than 5 parts by weight, the cleaning effect will be small, while if it exceeds 70 parts by weight, the difference in composition between the liquid phase and the gas phase will become large, resulting in the problem that the cleaning solvent cannot be used repeatedly. The cleaning solvent of the present invention can be produced by mixing Freon 123 and dimethoxymethane at the above-mentioned mixing ratio, but other solvents, additives, etc. can be added if necessary. The cleaning solvent thus obtained can be used for general cleaning purposes, but is particularly suitable for removing flux and dirt from printed circuit boards, degreasing, and the like. Since the cleaning solvent of the present invention has a maximum azeotropic point of 43.9°C, which is close to the boiling point of Freon 113 (47.6°C), conventional cleaning equipment for Freon 113 can be used as is. Therefore, the cleaning method using the cleaning solvent of the present invention includes not only the immersion method and the spray method, but also the steam cleaning method,
Alternatively, methods conventionally employed as cleaning methods using this type of cleaning solvent, such as a combination of these, can be employed, and in this case, heating, ultrasonic irradiation, etc. can also be performed. [Effects of the Invention] According to the present invention, the following cleaning solvent can be obtained. There is no need to use Freon 113. The cleaning equipment for Freon 113 can be used as is. It has high cleaning power and does not leave white residue or ionic residue on the items being cleaned. [Example] Next, an example of the present invention will be described. Example 1 200 grams of a mixture of Freon 123 and dimethoxymethane at a ratio of 50:50 (weight ratio) was placed in a flask equipped with a reflux device and heated with a heater. After about 30 minutes, when the temperature of the liquid phase in the flask stabilized, the compositions of the gas phase and liquid phase were analyzed. Furthermore, the above operation was repeated by changing the mixing ratio of Freon 123 and dimethoxymethane to the ratio of the points plotted on the boiling point curve A in Figure 1, and the compositions of the gas phase and liquid phase were analyzed. The vapor-liquid equilibrium diagram shown in Figure 1 was created. In Figure 1, A is the boiling point curve;
B shows the dew point curve. From Figure 1, it can be seen that the cleaning solvent of the present invention is Freon 123/
It shows an azeotropic point when the mixing ratio with dimethoxymethane is around 50/50% by weight, which has the favorable effect of eliminating the compositional deviation between the gas and liquid phases.Furthermore, since it becomes the highest azeotropic composition, the boiling point is around room temperature. The boiling point is approximately 15°C higher than that of Freon 123, which is also available, making it easier to handle. Furthermore, it can be seen that even when the percentage of Freon 123 is in the range of 5 to 70% by weight, the compositional deviation between the gas and liquid phases is small and a pseudo-azeotropic composition is exhibited. Example 2 60 μ of the flux shown in Table 1 was evenly applied to a square printed circuit board with sides of 65 mm, and after preheating to 100°C, 2 feet/2 feet were coated in a soldering bath at 260°C.
I soldered it in minutes. After soldering, the printed circuit board was left at room temperature for 1 hour, and then washed under the following conditions. Cleaning liquid: Freon 123 (50 parts by weight)/Dimethoxymethane (50 parts by weight) mixed solvent Cleaning process: Boiling immersion (30 seconds) → Ultrasonic cleaning (60 seconds)
(seconds) → Steam cleaning (30 seconds) Visually check the white residue on the printed circuit board after cleaning.
Also, check the ionic residue using an omega meter (manufactured by Kenko).
It was measured with The results are shown in Table 1. Comparative Example 1 A cleaning test similar to that in Example 2 was conducted using an azeotropic solvent mixture of Freon 113 (95.7 parts by weight)/ethanol (3.8 parts by weight)/nitromethane (0.5 parts by weight). The results are shown in Table 1.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a vapor-liquid equilibrium diagram of the Freon 123-dimethoxymethane system of Example 1, where A is the boiling point curve and B is the boiling point curve.
shows the dew point curve.

Claims (1)

[Claims] 1. A cleaning solvent comprising 1,1-dichloro-2,2,2-trifluoroethane and dimethoxymethane. 2. The cleaning solvent according to claim 1, wherein the mixing ratio of 1,1-dichloro-2,2,2-trifluoroethane and dimethoxymethane is 5:95 to 70:30 by weight.