JPH0470360B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a cleaning solvent made of a fluorine-based mixed solvent with excellent cleaning power and good stability, and particularly to a cleaning solvent suitable for removing flux and dust from printed circuit boards and degreasing. be. [Prior art] Fluorinated solvents have advantages such as nonflammability, low toxicity, and low corrosivity, so they are used as cleaning solvents in fields such as degreasing, etc.
It is especially widely used in fields such as removing flux and dust from printed circuit boards, and degreasing. For example 1,
1,2-trichloro-1,2,2-trifluoroethane (hereinafter sometimes abbreviated as Freon 113)
An azeotropic mixture in which ethanol, nitromethane, or methanol is added to increase the cleaning power is used as a cleaning solvent for removing flux from printed circuit boards (JP-A-50-80983, JP-A-51-44575). issue). However, in recent years, a cleaning solvent that can replace Freon 113 has been desired. However, since there is no comparable substitute for Freon 113, mixtures based on Freon 113 have started to attract attention. As such a mixture, a cleaning solvent consisting of Freon 113 and dimethoxymethane (hereinafter sometimes abbreviated as DMM) has been proposed (British Patent No. 1307631, German Patent No. 2133853). However, this cleaning solvent has the advantage that the difference in boiling point between Freon 113 and DMM is small, so even if they are mixed in any ratio, the composition difference between the liquid phase and the gas phase is small. When they coexist, they have the disadvantage of being extremely unstable, easily decomposed, and likely to generate corrosive gases. [Problems to be Solved by the Invention] The purpose of the present invention is to solve the above problems,
To provide a cleaning solvent that can reduce the amount of Freon 113 and has excellent cleaning power and stability. [Means for Solving the Problems] The present invention provides 1,1,2-trichloro-1,2,
This cleaning solvent is characterized by adding one or more stabilizers selected from nitroalkane, 2-methylfuran, propylene oxide, and epoxybutane to a mixed solvent consisting of 2-trifluoroethane and dimethoxymethane. 1,1,2- which is the main component of the cleaning solvent of the present invention
The mixing ratio of trichloro-1,2,2-trifluoroethane ( _CC2F - _CCF2 : Freon 113) and dimethoxymethane ( _CH3O - _CH2 - _OCH3 :DMM) is 10:90 by weight. or 90:10 range,
Preferably it is in the range of 30:70 to 70:30. If the proportion of Freon 113 is less than 10 parts by weight, the swelling of the elastomer tends to become too large, which is not preferable. In addition, if the proportion of Freon 113 exceeds 90 parts by weight, it tends not to meet the original purpose of reducing the amount of Freon 113 used. The stabilizers used in the present invention include nitroalkanes,
One or more selected from 2-methylfuran, propylene oxide and epoxybutane. Among these, nitroalkanes, 2-methylfuran and propylene oxide are preferred. Examples of nitroalkanes include nitromethane, nitroethane, and 1-nitropropane. The amount of the stabilizer added is 0.01 to 5% by weight, preferably 0.01 to 5% by weight based on the mixed solvent of Freon 113 and DMM.
It is 0.1 to 1% by weight. When the amount of stabilizer added is less than 0.01% by weight, the effect of the stabilizer is small, and the stability of the cleaning solvent is not sufficient. Moreover, if it exceeds 5% by weight, there is a risk that the stabilizer will remain on the object to be cleaned after cleaning. The cleaning solvent of the present invention can be produced by mixing Freon 113 and DMM at the above-mentioned mixing ratio, and adding the above-mentioned stabilizer at the above-mentioned addition ratio. The cleaning solvent of the present invention may contain other solvents, additives, etc., if necessary. The cleaning solvent thus obtained can be used for general cleaning purposes, but is particularly suitable for removing flux, dirt, and degreasing from printed circuit boards. The cleaning method using the cleaning solvent of the present invention includes a dipping method,
In addition to the spray method, methods conventionally employed as cleaning methods for this type of cleaning solvent, such as a steam cleaning method or a combination thereof, can be employed, and in this case, heating, ultrasonic irradiation, etc. can also be performed. [Effect of the invention] According to the present invention, 1,1,2-trichloro-
Since a specific stabilizer was added to the mixed solvent of 1,2,2-trifluoroethane and dimethoxymethane, the amount of 1,1,2-trichloro-1,2,2-trifluoroethane could be reduced. Moreover, it is possible to obtain a cleaning solvent that has excellent cleaning power and stability, does not decompose even when metals are present, and does not generate corrosive gas. [Example] Next, an example of the present invention will be described. Example 1 A test solution was obtained by adding 0.5% by weight of each of the stabilizers shown in Table 1 to 99.5% by weight of a mixed solvent containing Freon 113 and DMM at a mixing ratio of 90/10 (weight ratio). The water content in this test solution was measured and found to be 50 ppm. 4 g of this test solution was put into a glass tube with an inner diameter of 11 mm, and an iron piece, an aluminum piece, and a zinc piece measuring 8 mmw x 60 mm x 1 mmt were immersed in the tube and the tube was sealed. this
After storage at 100 °C for 4 days, the tip of the glass tube was cut off, the test solution was mixed with deionized water and bubbled, and the aqueous phase after bubbling was passed through a filter paper into a 50 ml volumetric flask, and also into the above glass tube. Wash several times with 3-5 ml of deionized water, collect this washing water in the volumetric flask, and add water to bring the total volume to 50 ml.
And so. The chloride ion concentration in this solution was measured by ion chromatography. The results are shown in Table 1.

[Table] As can be seen from Table 1, all stabilizers except diethylamine have a high stabilizing effect when the water content is low. Example 2 An example was carried out by adding water to a test solution consisting of 99.5% by weight of a mixed solvent of Freon 113 and DMM in a 90/10 (weight ratio) and 0.5% by weight of the stabilizer shown in Table 1. A test similar to 1 was conducted. Note that the water content in the test solution was 580 ppm. The results are shown in Table 2.

[Table] As can be seen from Table 2, nitromethane, 2-methylfuran, propylene oxide, and epoxybutane are highly effective as stabilizers even when the water content is high. Example 3 Each of the various fluxes shown in Table 3 was uniformly coated to a thickness of 60 μm on a printed circuit board with a side of 45 mm. After preheating this board to 100℃, it was heated to 260℃.
Soldering was carried out at a speed of 2 ft/min in a molten solder bath. After leaving it at room temperature for one hour, Freon 113/
DMM/nitromethane = 89.5/10/0.5 (weight%)
Cleaned with a cleaning solvent consisting of: The cleaning process included boiling immersion for 30 seconds, ultrasonic cleaning for 60 seconds, and steam cleaning for 30 seconds. After cleaning, the ionic residue remaining on the printed circuit board was measured using an Omegameter (manufactured by Kenko Co., Ltd., trademark) (Example). In addition, ionic residue was measured in the same manner as above using a cleaning solvent consisting of Freon 113/ethanol/nitromethane = 95.7/3.8/0.5 (wt%) (comparative example). The results are shown in Table 3. In addition, the values in the table are MIL
Expressed as a percentage of the standard value.

[Table] Example 4 Freon 113/DMM/Nitromethane = 89.35/
A cleaning solvent consisting of 10.17/0.48 (wt%) was charged into a two-tank washer, and changes in composition in the boiling tank and the second tank over time were measured using gas chromatography. The results are shown in Table 4.

【table】

[Table] As can be seen from Table 4, compositional changes in all tanks were extremely small.

Claims (1)

[Claims] 1. Nitroalkane, 2-methylfuran,
A cleaning solvent characterized by adding one or more stabilizers selected from propylene oxide and epoxybutane. 2. The cleaning solvent according to claim 1, wherein the mixing ratio of 1,1,2-trichloro-1,2,2-trifluoroethane and dimethoxymethane is 10:90 to 90:10 by weight. 3. The cleaning solvent according to claim 1, wherein the amount of the stabilizer added is 0.01 to 5% by weight based on the mixed solvent.