JP2735631B2 - Cleaning method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method suitable for cleaning printed circuit boards and the like, and a cleaning apparatus used therefor.

(Prior art)

2. Description of the Related Art A printed circuit board used for various electronic devices has a soldering step in a manufacturing process. In the soldering step, a flux such as rosin is usually used to improve the solder adhesion. The flux is removed by washing after the soldering process because it causes circuit corrosion and malfunction of the IC. Conventionally, as a method, first, a printed circuit board is immersed in pure water to remove the flux adhered to the printed circuit board, and then, in a water-compatible organic solvent such as isopropyl alcohol for draining and drying the printed circuit board. A method of immersing a printed circuit board in a substrate has been adopted.

[Problems to be solved by the invention]

However, according to the above-described method, there is a problem that the flux cannot be completely removed because the details of the printed circuit board cannot be sufficiently cleaned.

[Means for solving the problem]

In view of the above problems, the present inventors have studied a method capable of sufficiently cleaning the details of a printed circuit board and removing a flux attached to the details, and as a result, have found a cleaning method that can achieve the above object. Thus, the present invention has been completed.

That is, the present invention provides a first step of immersing an object to be cleaned in water, a water-compatible organic solvent 40 to 100% by weight of water and an arbitrary ratio of water that is completely compatible with water at an arbitrary ratio. A second step of dipping in a mixed solvent with 200 parts by weight,
And a third step of immersing the object to be cleaned pulled up from the mixed solvent in a water-compatible organic solvent which is completely compatible with water at an arbitrary ratio.

The first step in the cleaning method of the present invention is a step of immersing the object to be cleaned in water. When the object to be cleaned does not adhere various ions like a printed circuit board, pure water or ultrapure water is used as water. The immersion time of the object to be cleaned in water is not always limited, but is generally preferably 60 seconds or more for removing the flux of the printed circuit board.

Next, in the second step of the cleaning method of the present invention, a water-compatible organic solvent (hereinafter simply referred to as “water-compatible organic solvent”) that completely dissolves the object to be cleaned pulled up in the first step in 100 parts by weight of water and water at an arbitrary ratio. This is a step of immersing in a mixed solvent of 40 to 200 parts by weight (referred to as a water-compatible organic solvent). The water used here is preferably the pure water or the ultrapure water described in the first step.

In addition, as the water-compatible organic solvent, any known solvent may be used without any limitation as long as it is completely compatible with water at an arbitrary ratio. For example, methanol, ethanol,
Alcohols such as isopropanol; ketones such as acetone and methyl ethyl ketone;

The mixing ratio of water and the water-miscible organic solvent, the former must be in the range of 40 to 200 parts by weight with respect to 100 parts by weight, and the latter is preferably in the range of 50 to 150 parts by weight. . When the mixing amount of the water-miscible organic solvent is less than the above range, the detergency of the mixed solvent is insufficient, while when it is more than the above range, the detergency of the mixed solvent is sufficient. Cleaning of the details of the object to be cleaned cannot be performed sufficiently.

The immersion time of the object to be cleaned in the mixed solvent in the second step is slightly longer than the immersion time in the first step in order to sufficiently spread the mixed solvent to the details of the object to be cleaned.
It is preferably 120 seconds or more.

Next, the third step in the cleaning method of the present invention is a step of immersing the object to be cleaned raised in the second step in a water-compatible organic solvent. As the water-compatible organic solvent used in this step, the same one as described in the second step can be employed. This third step plays a role of draining the object to be cleaned lifted from the second step.

The third step is preferably as follows in order to sufficiently drain the object to be washed and to prevent generation of stains after drying. This is a method in which an object to be cleaned is immersed in a water-compatible organic solvent maintained at a temperature lower by 10 to 50 ° C. than the boiling point of the water-compatible organic solvent, and then the object to be cleaned is pulled up at a speed of 50 cm / mm or less.

The water-compatible organic solvent used here has a boiling point of 10 to
The temperature is kept lower by 50 ° C., and the object to be cleaned is immersed therein. Therefore, when the object to be cleaned loses heat, it is preferable to employ a water-compatible organic solvent having a boiling point not so high. Usually, a water-compatible organic solvent having a boiling point in the range of 50 to 90 ° C. is suitably used.

In a water-compatible organic solvent maintained in the above temperature range,
An object to be cleaned is immersed. Although the time of immersion is not particularly limited, it is usually 120 to sufficiently drain the object to be cleaned.
It is preferable to soak for at least two seconds.

Thereafter, the object to be cleaned is pulled up from the water-compatible organic solvent. The lifting speed of the object to be cleaned is preferably reduced when the temperature of the organic solvent is low, and can be increased when the temperature of the organic solvent is high. If the pulling speed is too slow, the processing capacity per unit time will be low, so in consideration of sufficient drying and processing capacity, the temperature condition of the organic solvent is generally in the range of 5 to 30 cm / mm. It is preferable to determine the pulling speed in relation to the following.

Note that the object to be cleaned in the present invention is usually pulled up in the vertical direction. However, the lifting may be performed in a direction forming an angle in the vertical direction, and the lifting speed in that case is represented by a vertical speed component.

In the above-mentioned cleaning method, the following apparatus is suitably employed. A first washing tank 1 for containing water, a second washing tank 2 for containing a mixed solvent of 100 parts by weight of water and 40 to 200 parts by weight of a water-compatible organic solvent, and a third washing tank for containing a water-compatible organic solvent. The third washing tank 3 and the second washing tank 2 are connected by a supply pipe 4 for supplying the water-compatible organic solvent in the third washing tank 3 to the second washing tank 2. This is a cleaning device in which a discharge pipe 5 for discharging the mixed solvent is provided in the second cleaning tank.

The mixed solvent gradually contaminated by the cleaning of the object to be cleaned in the second cleaning tank is discharged out of the system through the discharge pipe 5.
Then, the water-miscible organic solvent in the third cleaning tank is supplied to the second cleaning tank via the supply pipe 4 for preparing the mixed solvent which is insufficient in the second cleaning tank, and is separately supplied to the second cleaning tank. 6 to form a mixed solvent. further,
A new water-compatible organic solvent is supplied from the supply pipe 7 to the third cleaning tank in order to compensate for the shortage of the water-compatible organic solvent supplied to the second cleaning tank.

By using such an apparatus, since the water-compatible organic solvent can be used in both the third washing tank and the second washing tank, the water-compatible organic solvent can be effectively used.

Further, in the present invention, after the third cleaning tank, a step of drying and drying the object to be cleaned by spraying nitrogen gas can be added as necessary.

(Effect)

According to the cleaning method of the present invention, most of the object to be cleaned can be cleaned by the first cleaning tank, and details of the object to be cleaned can be cleaned by the second cleaning tank.
The cleaning object is sufficiently cleaned by the two cleaning tanks. Further, draining can be sufficiently performed by the third cleaning tank. In particular, when the above-described specific values are used as the temperature of the water-compatible organic solvent and the temperature at which the object to be cleaned is raised in the third cleaning tank, draining and drying can be performed simultaneously in the third cleaning tank. Because you can
There is no need to separately perform steam cleaning for drying.

The present invention can be applied to cleaning of a silicon wafer, a ceramic substrate, a glass substrate, and the like, in addition to the above-described cleaning of the printed circuit board.

〔Example〕

Examples and Comparative Examples will be given in order to explain the present invention in further detail, but the present invention is not limited to these Examples.

Example 1 Ultra-pure water, a mixed solvent of isopropyl alcohol and ultra-pure water having the composition shown in Table 1, respectively, in the first cleaning tank, the second cleaning tank, and the third cleaning tank of the cleaning apparatus shown in FIG. And isopropyl alcohol, and the printed circuit board on which the flux was adhered was sequentially immersed in each tank for 3 minutes to perform washing and drying. The flux amounts before and after washing and drying were determined, and the removal rates are shown in Table 1. In addition, the surface of the printed circuit board after washing and drying was observed with an optical microscope for the presence or absence of stains, and the results are shown in Table 1.

The liquid temperature of each tank was 60 ° C., and the printed circuit board was pulled up from the third washing tank at the speed shown in Table 1.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cleaning apparatus used in the present invention.

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C11D 7/50 C11D 7/50 C23G 5/04 C23G 5/04 H05K 3/26 H05K 3/26 (56) References JP-A-49-13034 (JP, A) JP-A-62-183804 (JP, A) JP-A-51-226071 (JP, A) JP-A-57-198278 (JP, A) JP-A-1-111338 (JP, A) Sho-55-115338 (JP, U) JP-B 47-11970 (JP, U) JP-B 45-3014 (JP, B1) JP-B 50-18484 (JP, B1) JP-B 48-14145 (JP-B) JP, B1) JP-B 35-1373 (JP, B1) JP-B 45-29595 (JP, B1) JP-B 52-30635 (JP, B2) JP-B 64-9620 (JP, B2) 58-20677 (JP, B2) JP-B 52-30634 (JP, B2) JP-B 60-26063 (JP, B2) JP-B 57-54079 (JP, B2) Jiko 42-6781 (JP , Y1)

Claims (2)

(57) [Claims] A first step of immersing the object to be washed in water; a water-miscible organic solvent which completely dissolves the object to be washed taken up from the water in 100 parts by weight of water and water at an arbitrary ratio;
A second step of immersing in a mixed solvent with 0 parts by weight, and a third step of immersing the object to be cleaned pulled up from the mixed solvent in a water-compatible organic solvent which is completely compatible with water at an arbitrary ratio. A cleaning method characterized by comprising: 2. A water-miscible organic solvent which is completely compatible with water in an optional ratio with a first washing tank containing water, and 100 parts by weight of water.
A second washing tank containing a mixed solvent of 40 to 200 parts by weight, and a third washing tank containing a water-miscible organic solvent which is completely compatible with water at an arbitrary ratio. A third supply pipe supplies the soluble organic solvent to the second washing tank.
A cleaning apparatus in which a cleaning tank and a second cleaning tank are connected, and a discharge pipe for discharging a mixed solvent in the second cleaning tank is provided in the second cleaning tank.