JPH1060488A - Cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method using a cleaning liquid containing a hydrocarbon-based solvent and an organic compound capable of coordinating with metal ions, and also capable of prolonging the life of the cleaning liquid and the period of maintaining the cleaning effect, and reducing the cost of cleaning by solving the problem of reattachment of a soil in a rinsing process. SOLUTION: This method for cleaning consists of a cleaning process, a preliminary rinsing process and a final rinsing process. In this case, a cleaning agent containing a hydrocarbon-based solvent and an organic compound capable of coordinating with metal ions is used in the cleaning process, the same cleaning agent is used in the preliminary rinsing process and a hydrocarbon-based solvent or a fluorine-based incombustible solvent is used in the final rinsing process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cleaning method. More specifically, the present invention uses an organic solvent-based cleaning solution that does not contain a halogen compound and has an excellent cleaning effect, and does not cause re-adhesion of the dirt in a rinsing bath. The present invention relates to a cleaning method suitable for:

[0002]

2. Description of the Related Art When soldering an electronic component to a printed circuit board, a flux is used for the purpose of removing an oxide film on the surface of the solder or preventing reoxidation of the solder. The residue in which the flux has been modified after soldering contains an ionic substance, which causes corrosion of substrate wiring and deterioration of electrical insulation. For this reason, it is necessary to sufficiently wash the printed circuit board after soldering to remove the residue. Conventionally, to remove such residues, 1,1,1
Organic chlorinated solvents such as trichloroethane and CFCs
Cleaning using a so-called chlorofluorocarbon solvent such as -113 has been widely performed. However, these solvents have been shown to destroy the stratospheric ozone layer, and it has been determined that their use will be completely abolished by the end of 1995. Therefore, there is an urgent need to develop a new detergent that can replace these solvents, that is, a so-called CFC substitute detergent. Cleaning using a CFC substitute cleaning agent is becoming widespread, mainly in aqueous or hydrocarbon solvents, but the former requires a wastewater treatment and drying step, and therefore has a large burden in terms of cost. In addition, the latter has low toxicity among solvent-based cleaning agents, has a small effect on printed circuit board resin materials, and is advantageous in that it is relatively inexpensive.However, since the solubility of ionic substances is low,
Detergent power of flux residue is small and it has not been used so far. Further, a method has been proposed in which an organic compound having a polar group such as an alcohol, ether, ester, carboxylic acid, or ketone is added to an aliphatic hydrocarbon having an average carbon number of 8 to 20 to enhance the detergency (Japanese Patent Laid-Open Publication No. HEI 9-258572). 3-146
597), the detergency was not always sufficient.
The present inventor has found that a method using a cleaning solution containing a hydrocarbon solvent and an organic compound capable of coordinating with metal ions for cleaning dirt containing ionic residues such as cleaning of printed circuit boards is a very excellent cleaning method. It was found earlier that it worked. When the cleaning is performed using this cleaning liquid, rinsing is finally performed in order to remove the contaminated cleaning liquid adhered to the surface of the object to be cleaned after cleaning and the volatile organic compounds that can coordinate to metal ions. As a drug used in the rinsing step, it is desirable to have properties such as being easily volatilized, not containing a non-volatile component, and being reusable,
Considering these points, hydrocarbon solvents and fluorine-based nonflammable solvents are suitable. However, since these solvents have almost no dissolving power for ionic residues, if the concentration of dirt in the contaminated cleaning liquid adhering to the printed circuit board increases, the dirt is re-adhered in the rinsing step, and the cleaning effect is obtained. Has become a problem. In addition, since the soil concentration at this time is lower than the saturated soil dissolution concentration of the cleaning solution, the cleaning solution must be replaced without making full use of its capacity, which increases the amount of chemicals used and increases the cleaning cost. Will also be. For this reason, re-adhesion of dirt hardly occurs in the rinsing step,
There has been a demand for a cleaning method capable of completely cleaning a printed circuit board, reducing the frequency of replacement of the cleaning liquid, and fully utilizing the capacity of the cleaning liquid.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning solution using a cleaning solution containing a hydrocarbon solvent and an organic compound capable of coordinating to metal ions by eliminating the reattachment of dirt in a rinsing step. It is an object of the present invention to provide a cleaning method capable of extending the life of the device, extending the period during which the cleaning effect can be maintained, and reducing the cleaning cost.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that an organic solvent capable of coordinating with a hydrocarbon solvent and a metal ion between a washing step and a rinsing step. By providing a preliminary rinsing step of rinsing with a cleaning solution containing a compound, it was found that the amount of dirt carried into the final rinsing step was reduced, and the period during which the cleaning effect could be maintained was greatly extended. Thus, the present invention has been completed. That is, the present invention
(1) A cleaning method comprising a cleaning step, a preliminary rinsing step, and a final rinsing step, wherein a cleaning liquid containing a hydrocarbon solvent and an organic compound capable of coordinating to metal ions is used in the cleaning step. In, using a cleaning solution containing an organic compound capable of coordinating a hydrocarbon solvent and metal ions, in the final rinsing step, a cleaning method characterized by using a hydrocarbon solvent or a fluorine-based nonflammable solvent, Is provided. Further, as a preferred embodiment of the present invention, (2) the cleaning method according to (1), wherein the hydrocarbon solvent is an aliphatic hydrocarbon having 5 to 20 carbon atoms, and (3) metal ions can be coordinated. The washing method according to the above (1) or (2), wherein the organic compound is a coordinating compound having an oxygen atom as a coordinating atom, and (4) the coordinating compound having an oxygen atom as a coordinating atom. The washing method according to item (3), which is one or more compounds selected from the group consisting of, 1-alkyl-2-pyrrolidone, trialkylphosphine oxide and dialkylsulfoxide; (5) 1-alkyl-2 The washing method according to (4), wherein the alkyl group of pyrrolidone, trialkylphosphine oxide and dialkylsulfoxide is a linear alkyl group having 3 to 18 carbon atoms, (6) an organic compound capable of coordinating with a metal ion; If the amount of compound added is 10 to 300 per liter of hydrocarbon solvent
g, the cleaning method according to the above (1), (2), (3), (4) or (5), and (7) the solvent used in the final rinsing step has a boiling point of Item (1), which is 40 to 300 ° C.,
(2), the cleaning method according to (3), (4), (5) or (6), (8) in the preliminary rinsing step, two or three preliminary rinsing tanks Items (1) and (2) used in series
Clause, (3), (4), (5), (6) or
(7) The cleaning method according to (7), and (9) the cleaning method according to (1), wherein the object to be cleaned is a printed circuit board to which a flux residue is attached.
(2), (3), (4), (5), (6),
The washing method described in the item (7) or (8) can be mentioned.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The cleaning method of the present invention comprises a cleaning step,
It consists of a preliminary rinsing step and a final rinsing step. In the cleaning step, cleaning is performed using a cleaning liquid containing a hydrocarbon solvent and an organic compound capable of coordinating with metal ions. In the preliminary rinsing step, rinsing is performed with a cleaning solution containing a hydrocarbon solvent and an organic compound capable of coordinating with metal ions. In the final rinsing step, rinsing is performed using a hydrocarbon-based solvent or a fluorine-based nonflammable solvent. The hydrocarbon solvent used in the cleaning solution of the present invention is not particularly limited as long as it dissolves the flux residue. For example, n-pentane, n-hexane, isohexane, n-
Paraffinic hydrocarbons such as heptane, isoheptane, isooctane, decane, dodecane, hexadecane and icosane; olefinic hydrocarbons such as 1-decene and 1-dodecene; naphthenic hydrocarbons such as cyclohexane and decalin; terpenes such as limonene and pinene Series hydrocarbons,
In addition to aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and tetralin, petroleum ether, petroleum benzine, ligroin, and solvent naphtha can be given. In the method of the present invention, one of these hydrocarbon solvents can be used alone,
Two or more kinds can be used as a mixture. Among these hydrocarbon solvents, aliphatic hydrocarbons having 5 to 20 carbon atoms can be suitably used because they have particularly excellent cleaning effects. When safety is emphasized, it is preferable to use a solvent having a flash point of 70 ° C. or more (Fire Class 4 Class 3 petroleums).

The organic compound capable of coordinating with metal ions used in the method of the present invention is not particularly limited as long as it is soluble in a hydrocarbon solvent.
Examples thereof include compounds having an oxygen atom as a coordinating atom, such as pyrrolidone, trialkylphosphine oxide, and dialkylsulfoxide. In these compounds,
The alkyl group is preferably a straight-chain alkyl group having 3 to 18 carbon atoms, but a compound in which the alkyl group has a short side chain can also be used. Examples of such a coordinating compound include 1-n-octyl-2-pyrrolidone (NOP), 1-n-dodecyl-2-pyrrolidone (NDP), tri-n-octylphosphine oxide (TOPO), -N-butylsulfoxide (DBS
O), tri-n-butylphosphine oxide (TBP
O) and the like. As the organic compound capable of coordinating with these metal ions, only one kind can be added to the hydrocarbon solvent, or two or more kinds can be added. The organic compound capable of coordinating to these metal ions is 10 to 300 per liter of the hydrocarbon solvent.
g, more preferably 30 to 250 g. The amount of the organic compound that can coordinate to the metal ion is 10 g per liter of the hydrocarbon solvent.
If it is less than the above value, a sufficient cleaning effect may not be obtained in the cleaning step, and a sufficient rinsing effect may not be obtained in the preliminary rinsing step. Even if the addition amount of the organic compound capable of coordinating to the metal ion exceeds 300 g per liter of the hydrocarbon-based solvent, the cleaning effect and the rinsing effect are not improved in proportion to the increase in the amount of the coordinating compound. The cleaning effect or the rinsing effect may be reduced, which may adversely affect the printed circuit board resin, and the required amount of the rinsing liquid in the final rinsing step is increased.

[0007] The cleaning liquid used in the method of the present invention may further contain other components as necessary. As other components to be contained, for example, a surfactant and a corrosion inhibitor can be exemplified. As the surfactant, a lipophilic nonionic surfactant having a low HLB can be suitably used. Examples of such a surfactant include polyoxyethylene alkyl ether, alkylamine oxide, and the like. And silicone-based surfactants such as polyether-modified silicone. Examples of the corrosion inhibitor include mercaptobenzothiazole and benzotriazole. In the method of the present invention, in the cleaning step, an object to be cleaned is first brought into contact with a hydrocarbon-based solvent and a cleaning solution containing an organic compound capable of coordinating to metal ions. The method of the present invention is particularly effective when the object to be cleaned is a printed circuit board to which a flux is applied and soldered, and the flux residue adhering to the printed board can be effectively removed. There is no particular limitation on the method of contacting the object to be cleaned with the cleaning liquid, for example, immersing the object to be cleaned in the cleaning liquid,
Alternatively, a cleaning liquid can be sprayed on the object to be cleaned. When the object to be cleaned is immersed in the cleaning liquid, cleaning can be promoted by agitation, rocking, the action of ultrasonic waves, or the like, if necessary. When the object to be cleaned is a printed circuit board to which a flux residue has adhered, the metal component in the flux residue forms a metal complex with an organic compound capable of coordinating to metal ions, dissolves, and is removed from the printed circuit board surface. You.

In the method of the present invention, the object to be cleaned from which dirt has been removed in the cleaning step is then transferred to a preliminary rinsing step, and is brought into contact with a cleaning liquid containing a hydrocarbon solvent and an organic compound capable of coordinating with metal ions. Thus, dirt adhering to the object to be cleaned and brought in from the cleaning tank is dissolved and removed. The cleaning liquid used in the preliminary rinsing step can be the same as the cleaning liquid used in the cleaning step, or one in which only one of the hydrocarbon compound or the organic compound that can coordinate to the metal ion is the same and the other is different Alternatively, both the hydrocarbon solvent and the organic compound that can coordinate to the metal ion can be different. However, it is usually preferable to use the same cleaning liquid in the cleaning step and the preliminary rinsing step. The use of the same cleaning liquid not only facilitates the control of the cleaning liquid and the process, but also replenishes the preliminary rinsing tank with a new cleaning liquid and overflows the cleaning liquid from the preliminary rinsing tank to the cleaning tank, thereby enabling the preliminary rinsing step to be performed. The used cleaning liquid is reused in the cleaning step, and the stain concentration of the cleaning liquid in the cleaning step and the preliminary rinsing step can be kept in a steady state. Since the cleaning liquid used in the method of the present invention has a large dissolving power for ionic dirt, a sufficient rinsing effect can usually be obtained with only one preparatory rinsing tank. Depending on the situation, a plurality of preliminary rinsing tanks may be provided in series, and the preliminary rinsing may be performed a plurality of times.

In the method of the present invention, the object to be cleaned, from which dirt adhered in the preliminary rinsing step has been sufficiently removed, is finally transferred to the final rinsing step, and is brought into contact with a hydrocarbon-based solvent or a fluorine-based nonflammable solvent. A cleaning solution containing an organic compound capable of coordinating to metal ions adhering to an object to be cleaned is removed. In the method of the present invention, the hydrocarbon-based solvent used in the final rinsing step is not particularly limited as long as it dissolves an organic compound capable of coordinating with metal ions contained in the cleaning solution. For example, n-pentane, n- Hexane, isohexane, n-heptane, isoheptane, isooctane, decane, dodecane, hexadecane, paraffinic hydrocarbons such as icosane, olefinic hydrocarbons such as 1-decene, 1-dodecene, cyclohexane, naphthenic hydrocarbons such as decalin, In addition to terpene hydrocarbons such as limonene and pinene, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene and tetralin, and the like, petroleum ether, petroleum benzine, ligroin, solvent naphtha, and the like can be given. In the method of the present invention, one of these hydrocarbon solvents may be used alone, or two or more thereof may be used in combination. Among these hydrocarbon solvents, aliphatic hydrocarbons having 5 to 20 carbon atoms can be suitably used because they have particularly excellent cleaning effects. When safety is emphasized, it is preferable to use a solvent having a flash point of 70 ° C. or more (Fire Class 4 Class 3 petroleums).

In the method of the present invention, the fluorine-based nonflammable solvent used in the final rinsing step is not particularly limited as long as it dissolves an organic compound which can coordinate to metal ions contained in the cleaning solution. C _n F _{2n + 2} such as perfluorocarbon (PFC) represented by the chemical formula C _n H _m F _{2n +} hydrofluorocarbons represented by _2-m (HFC), chemical formula _{C n H m F 2n + 1} -m OC p H _q F _{2p + 1-q} hydrofluoroether represented by (HFE), and the like. In the method of the present invention, the hydrocarbon-based solvent or the fluorine-based nonflammable solvent used in the final rinsing step can be appropriately selected depending on safety equipment of the factory used and restrictions on the drying time. Considering the properties, the boiling point is preferably 40 to 300 ° C. According to the method of the present invention, by providing a preliminary rinsing step and rinsing with a cleaning solution containing a hydrocarbon solvent and an organic compound capable of coordinating to metal ions, the dirt on the final rinsing step with low dissolving power of dirt is removed. The carry-in amount can be minimized, and re-adhesion of dirt in the final rinsing step can be prevented. As a result, it can be used for a long time until the cleaning solution in the cleaning step reaches the saturated soil dissolving concentration. Further, the cleaning liquid in the preliminary rinsing step can be reused in the cleaning step, so that the cleaning liquid can be used efficiently, the amount of liquid used in the entire system can be reduced, and the cleaning cost can be significantly reduced. .

[0011]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 Cleaning was performed by a cleaning method including a cleaning step, a preliminary rinsing step, and a final rinsing step shown in FIG. Small printed circuit board [manufactured by Sun Hayato Co., Ltd., ICB-86G, size 36
× 46 mm], 0.2 ml of a flux [Lapics RA, manufactured by Nippon Solder Co., Ltd.] was applied twice and air-dried.
This was soldered in a 260 ° C. molten solder tank to obtain an object to be cleaned. TECLEAN N-20 [Nippon Oil Co., Ltd.
, Naphthenic solvent] was added to 1,000 ml, 1-n-dodecyl-2-pyrrolidone (138 ml) was added, stirred and uniformly dissolved to prepare a washing solution. Add 200 ml of this washing solution to 2
Each was placed in a stainless steel container, and one was used as a washing tank and the other was used as a preliminary rinsing tank. Also, 50 ml of n-hexane was placed in a stainless steel container to form a final rinse tank.
Cleaning tank, pre-rinse tank and final rinse tank are all 25
C. The object to be cleaned was immersed for 2 minutes for cleaning while stirring the cleaning liquid in the cleaning tank with a magnetic stirrer.
Next, the object to be cleaned was transferred to a preliminary rinsing bath, immersed, and rinsed for 30 seconds while rocking. Further, the object to be cleaned was transferred to a final rinsing bath, immersed, rinsed for 30 seconds while rocking, and then dried with a drier. The washed and dried object is washed with a 75% by volume aqueous solution of isopropyl alcohol 3
The residue was immersed in 0 ml and subjected to ultrasonic waves to extract the residue for 5 minutes. When the electric conductivity of this extract was measured,
It was 0.63 μS / cm. Since the electric conductivity of the extract has a larger value as the amount of residue on the object to be cleaned increases,
It can be used as an indicator of the amount of residue. That is, the smaller the electric conductivity of the extract, the better the residue of the object to be cleaned has been washed. In the same manner, the object to be washed was repeatedly washed, and the residue attached to the dried object to be washed was extracted with an aqueous isopropyl alcohol solution, and the electric conductivity of the extract was measured. The electric conductivity was 0.66 μS / cm for the fourth sheet to be cleaned, 0.64 μS / cm for the seventh sheet, and
0.65 μS / cm for the 20th sheet, 0.69 μS for the 20th sheet
S / cm, 0.61 μS / cm for the 40th sheet, 0.61 μS / cm for the 60th sheet, 0.61 μS / c for the 80th sheet
m, 0.65 μS / cm for the 100th sheet, 0.63 μS / cm for the 150th sheet, 0.73 μS / c for the 199th sheet
m, it was 0.68 μS / cm at the 250th sheet. Washing of the object to be washed was continued up to 250 sheets, but no remarkable increase in electric conductivity was observed in the extract. Washing was still possible, but was interrupted once on the 250th sheet. Comparative Example 1 Cleaning was performed by a cleaning method including only the cleaning step and the rinsing step shown in FIG. 2 without providing a preliminary rinsing tank. That is, the same operation as in Example 1 was repeated, except that only two of the cleaning tank containing 200 ml of the cleaning liquid prepared in Example 1 and the rinsing tank containing 50 ml of n-hexane were used. The electric conductivity of the extract was 0.63 μS / cm for the first sheet to be washed, 0.65 μS / cm for the fourth sheet, 0.67 μS / cm for the seventh sheet, and 0 for the tenth sheet. .68μS
/ Cm, 0.68 μS / cm for the 20th sheet, 0.55 μS / cm for the 30th sheet, 0.64 μS / cm for the 40th sheet,
0.62 μS / cm for the 50th sheet, 0.5 for the 60th sheet
8 μS / cm, 0.65 μS / cm for the 70th sheet, 0.74 μS / cm for the 75th sheet, 0.87 μS for the 80th sheet
/ Cm, and at the 85th sheet, 1.02 μS / cm. When the number of articles to be washed reached 80, the electric conductivity of the extract began to increase remarkably, and washing could not be continued. The 85th washing was stopped. The results of Example 1 and Comparative Example 1 are shown in Table 1 and FIG. 3, including the values of the electric conductivity measured in addition to the above.

[0012]

[Table 1]

From the results shown in Table 1 and FIG. 3, in the cleaning method of Comparative Example 1 having no preliminary rinsing step, re-adhesion of dirt in the rinsing liquid occurs after about 80 cleanings, and the cleaning effect is reduced. The number of sheets to be cleaned is limited to about 75 sheets. On the other hand, Example 1 having a preliminary rinsing step
In the cleaning method of the present invention, no decrease in the cleaning effect is observed even after 250 sheets have been cleaned, and it can be seen that the provision of the preliminary rinsing step extends the life of the cleaning liquid at least three times or more. That is, the amount of highly polar dirt brought into the final rinsing tank by passing through the preliminary rinsing step can be reduced, and the life of the cleaning liquid can be extended.

[0014]

According to the method of the present invention, the cleaning effect can be maintained for a long period of time in the cleaning using a cleaning solution containing a hydrocarbon solvent and an organic compound capable of coordinating with metal ions, and the use of the cleaning solution. The volume can be reduced and cleaning costs can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a process flow diagram of a cleaning method of the present invention.

FIG. 2 is a process flow diagram of a conventional cleaning method.

FIG. 3 is a graph showing the relationship between the number of cleanings and electric conductivity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H05K 3/26 7511-4E H05K 3/26 A

Claims (1)

[Claims] 1. A cleaning method comprising a cleaning step, a preliminary rinsing step, and a final rinsing step, wherein a cleaning liquid containing a hydrocarbon solvent and an organic compound capable of coordinating to metal ions is used in the cleaning step. In the rinsing step, a cleaning liquid containing a hydrocarbon solvent and an organic compound capable of coordinating to metal ions is used, and in the final rinsing step, a hydrocarbon solvent or a fluorine-based nonflammable solvent is used. Method.