JPS5820677B2 - Osenbutsupinnoseijiyoukahou Oyobi Sonoseijiyoukayounosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cleaning contaminated articles such as printed circuit boards.

It is well known that halogenated hydrocarbons can be used as cleaning fluids to remove various contaminants from a wide variety of articles.

Thus, 1,1,2-trichloro-2,2-trifluoroethane can be used as a cleaning fluid to remove unwanted contaminants from the surfaces of organic synthetic polymers and plastics.

This is because the fluid does not attack polymeric or plastic substrates to any significant extent.

However, generally a plastic substrate (on which various articles, namely polymeric insulation and markings (m
With a printed circuit carried on a component containing a resin base bonded to the component (on which a component with a flux can be placed), e.g. Even if the material was not eroded, the problem that the flux was not effectively removed continued to occur.

Accordingly, there is a need in the art for solvents or solvent compositions and cleaning methods that remove fluxes and flux residues that can be extremely sticky without attacking plastic substrates or such components.

In this connection, it has been proposed to use an alcohol mixed with the main solvent, such as the aforementioned trichlorotrifluoroethane.

This is because alcohols are more effective than primary solvents at removing fluxes and flux residues.

Azeotropy between the main solvent and alcohol
c) Mixture (often boiled)
is often used, but such azeotropes may not contain a sufficient amount of alcohol to effectively remove the fluxing agent.

Therefore, the use of such azeotropes does not provide a complete answer to the cleaning problem mentioned above.

Efforts have also been made to simply solve the problem by immersing the contaminated article in a mixture of alcohol and primary solvent at a concentration significantly higher than the alcohol concentration in the azeotrope.

In this case, the mixture of concentrated alcohol and principal solvent is maintained at a relatively low temperature, ie close to ambient temperature, for example 20 DEG C. or below.

If desired, following such a soaking process, the soaked article may be contacted with a cold, clean liquid mixture of the primary solvent and alcohol in a separate tank, or alternatively, evaporated from the liquid mixture and then It is also possible to contact the cold liquid produced by condensation while in the vapor zone and then drain the working liquid from the article.

However, with such methods, the loss of solvent may be very significant due to the deposition of a cold solvent layer on the articles being removed from the cleaning device and/or the method In some applications, it may not yet be possible to achieve a sufficiently high degree of flux removal from contaminated articles.

Conventional cleaning devices for treating contaminated articles may consist of a cleaning liquid tank in which the articles are immersed, the liquid tank having an overflow pipe to a sump tank. It is something.

This sump tank contains a relatively small amount of liquid that is maintained at a boiling state, and the purpose of this sump tank is not to allow the process articles to come into contact with the liquid, but rather to allow contaminants to collect in the sump tank. It collects the solvent.

The vapor above the liquid level is condensed and returned to the liquid tank, thereby ensuring that clean solvent is present in the liquid tank, while impure solvent spills into the sump tank.

The articles to be treated are removed from the liquid tank, then passed through a vapor zone and finally removed out of the cleaning device.

It is not effective to use hot or boiling solvent mixtures containing high concentrations of alcohol in the tanks of such cleaning equipment.

This is because the alcohol evaporates from the liquid tank and is depleted, while the amount of alcohol in the liquid storage tank increases.

Therefore, such cleaning device systems are not stable and do not perform the cleaning task required of the device system.

The inventors therefore now provide a method for cleaning contaminated articles, which is completely different from the methods previously used, which method is stable and avoids the disadvantages of the conventional methods, and which cleans contaminated articles at elevated temperatures. can be effectively cleaned.

According to the invention, therefore, in a method for cleaning contaminated articles, a solution comprising a fluorochlorocarbon solvent and an auxiliary organic solvent with which it can form an azeotrope (both heated to 30° C.) is provided. 1, in which the concentration of said auxiliary organic solvent is higher than the organic solvent concentration of the azeotrope itself, followed by contacting said fluorocarbon a second single-phase liquid mixture containing a chlorocarbon solvent and a proportion of said co-solvent that is lower than that contained in the first liquid mixture but at least equal to the co-solvent concentration of the azeotrope; rinsing the article, cooling and condensing the evaporated vapor mixture from the first and second liquid mixtures; supplying the resulting liquid mixture to the second liquid mixture; The present invention provides a method for cleaning a contaminated article, the method comprising supplying a liquid mixture from a second liquid mixture that is commensurate with the reduction by the second liquid mixture.

Substantially azeotropic (5nbsta) of a fluorochlorocarbon solvent and an auxiliary organic solvent (hereinafter simply referred to as auxiliary solvent)
azeotropic) mixture, or feeds of both said solvents sent separately in suitable proportions corresponding to a substantially azeotropic mixture;
Preferably, it is introduced into the system from an external source, either continuously or intermittently.

According to one preferred embodiment of the method, the article to be treated is immersed in said heated first liquid mixture contained in one sump compartment of the cleaning device system; passing the article to be treated through a second liquid mixture in one rinsing zone of the rinsing chamber, wherein said first liquid mixture and said second liquid mixture have a common vapor zone. It provides a method for cleaning articles.

It is also preferred to heat this second liquid mixture.

This second liquid mixture is in equilibrium with the vapor in the vapor zone above the sump and rinse compartments and in equilibrium with the first liquid mixture in the sump compartment (in other words: (meaning that the composition of the second liquid mixture is substantially constant with respect to the vapor in the vapor zone and the first liquid mixture).

Multiple rinse compartments can be used if desired.

Appropriate amounts of a substantially azeotropic mixture or a fluorochlorocarbon solvent and a cosolvent corresponding to a substantially azeotropic mixture are continuously or intermittently added to the sump and/or rinse section of the cleaning system. It is appropriate to introduce it into the room.

In a preferred embodiment of the method described above, at least a portion, in particular all, of the liquid obtained by condensing the vapors of the common vapor zone forces is returned to the rinsing compartment.

It is also most appropriate to ensure that the liquid mixture overflowing from the rinse compartment is passed to the sump compartment in an amount commensurate with the loss due to evaporation.

having the ability to form an azeotrope in the liquid reservoir (azeo);
Trope-forming) The first liquid mixture has a concentration of at least 5 parts by weight (more preferably at least 10 parts by weight) more per 100 parts by weight of the total mixture than the concentration corresponding to the azeotrope itself. Preferably, a co-solvent is included.

Among the fluorochlorocarbons that can be used illegally, especially 2
Mention may be made of fluorochlorocarbons having 1 or 3 carbon atoms, for example 1,1,2,2-tetrachloro-1,2-difluoroethane.

Particularly good results are obtained with 1,1,2-trichloro-2,2-trifluoroethane.

Examples of auxiliary organic solvents that can be used with fluorochlorocarbon solvents to obtain azeotrope-forming mixtures include methyl acetate, nitroparaffins (e.g. nitromethane), and alcohols, which also contain the aforementioned trichlorocarbons. Forms an azeotrope with trifluoroethane.

Thus alcohols having 1 to 4 carbon atoms can be used, including methyl alcohol, ethyl alcohol, tertiary butanol and isopropyl.

There's alcohol.

Isopropyl alcohol is particularly useful.

The concentration of alcohol in the fluorochlorocarbon solvent used in the reservoir and rinse compartments can be varied depending on the particular fluorochlorocarbon and the particular alcohol used.

For example, when using 1,1,2-trichloro-2,2-trifluoroethane and isopropanol, the concentration of isopropanol in the reservoir is preferably less than 70% by weight.

The liquid in the rinse tank has a different composition than the liquid in the sump compartment.

In practice, once stable conditions have been established, the solvent mixture in the rinse compartment generally ranges from a value corresponding to the azeotrope second solvent concentration to 11% by weight below the azeotrope second solvent concentration. The second solvent or co-solvent is present at a concentration ranging from up to 5% by weight or less (preferably up to 5% by weight or less).

The method of the present invention includes a single immersion of the contaminated article in said heated liquid mixture in the sump compartment, or a concomitant subsequent immersion in said heated solvent mixture in the rinsing compartment. The method is particularly one technical feature that is illegal and unpredictable over conventional cleaning methods.

When a concentration range of 10-70% Improper Tool is used in the reservoir compartment, concentrations of up to 14% by weight Improper Tool may be used in the rinse compartment.

It is common to use isopropanol in concentrations of 10 to 40% by weight in the reservoir compartment, with a concentration range of 22 to 27% by weight giving particularly useful results.

When using the lower of these ranges of alcohol in the sump compartment, use a concentration of alcohol in the rinse compartment that is 4% or less greater than the alcohol concentration of the azeotrope. is preferred.

As a specific example, the solvent mixture in the rinse tank containing 5.5% isopropanol is substantially constant with respect to the vapor in the vapor zone above the rinse compartment and the sump compartment; Moreover, the solvent mixture in the liquid reservoir chamber is 25%.
It has been found that it remains essentially constant even for solvent mixtures containing isopropanol.

However, the solvent mixture in both the rinse compartment and the sump compartment is assumed to be in a boiling state.

1,1,2-trichloro-1,2,2 as the main solvent
- When using trifluoroethane, the concentration of ethyl alcohol is between 25 and 3
It is preferred to use 0% by weight, whereas for methyl alcohol it is preferred to use a concentration of 17-22% by weight.

If the solvent mixture in the reservoir compartment is used at these concentrations, the rinse compartment preferably contains ethyl alcohol at a concentration of 6 to 8% by weight, preferably methyl alcohol at a concentration of 8 to 10% by weight. preferable.

The substantially azeotropic mixture introduced into the apparatus system may contain a second solvent or co-solvent at a concentration as high as the second solvent concentration in the rinse tank.

Good results can be obtained with a mixture of primary and co-solvent that boils within 1 or 2°C of the boiling point of the azeotrope.

The azeotrope itself e.g. 97.1% by weight of 1.1.2
-trichloro-1,2,2-trifluoroethane and 2.
An azeotrope consisting of 9% by weight of isopropanol,
Very good results have been obtained when used as an additional mixture fed to the equipment system during the main cleaning operation.

It is most appropriate to introduce the substantially azeotropic mixture as such into the system.

However, if desired, the main solvent and co-solvent corresponding to a substantially azeotropic mixture may be prepared separately in suitable proportions, e.g. can also be introduced separately into the reservoir compartment and/or the rinsing compartment in appropriate proportions.

Preferably, the amount of substantially azeotropic mixture introduced into the apparatus system is that amount required to maintain a constant mixture concentration in the sump and rinse compartments.

The solvent mixture in the reservoir and rinse compartments was heated to ambient temperature (
The temperature is maintained at a temperature higher than 20° C. in some cases.

It is common to maintain the solvent mixture at a temperature of at least 30°C, and preferably at a temperature of at least 40°C.

More preferably, the solvent mixture is maintained at its boiling point, 1
- In the case of mixtures of 1,2-trichloro-1,2,2-trifluoroethane, this boiling point is often in the range 45-50°C.

Other solvents or additives can be added to the solvent compositions if it is desired to improve the cleaning power or solvent power of the solvent compositions used herein.

Suitable additives include cationic, anionic and nonionic detergents.

In some cases, especially solvents. Water can also be added when the composition includes a detergent, but this is not necessary.

The use of stabilizers in the solvent mixture is usually unnecessary.

However, the use of stabilizers may be desirable under corrosive conditions, for example under conditions where the solvent mixture comes into contact with light metals such as zinc and aluminum.

One of the advantageous technical features of this nature is that the system is extremely stable, i.e. the concentration of co-solvent, e.g. can be maintained.

Contaminant removal is also always carried out to a high degree.

For example, if the nature is operated on a 24 hour per day basis, 2
After intermittent cleaning of the contaminated articles over a period of 20 hours, the weight percent of isopropanol in the reservoir compartment was found to be substantially the same as at the beginning of the operation. It was done.

That is, when the isopropanol content is initially 23.6%,
During operation, it remained within the range of 23.3% to 23.9%.

The solvent composition in the rinse compartment also remained substantially constant, with an initial isopropanol content of 5.4% remaining within the range of 5.3% to 5.6% during operation.

This property also has the advantage of avoiding flammable situations of solvents.

Its properties are useful in a wide variety of applications, including removing difficult-to-remove solder fluxes from electrical devices.

In particular, the present invention is useful for removing flux from devices carried on plastic or resin substrates without damaging the plywood or components on the substrate.

Another implementation of the nature is one compartment (liquid compartment)
contacting the contaminated article with said heated first liquid mixture in a cleaning apparatus system having said article and removing said article into a vapor zone above said sump compartment; and rinsing the article with said second liquid mixture initially obtained by condensing vapor from said vapor zone.

A method of remediation of this nature includes, after being immersed in said heated first liquid mixture, the contaminated article is passed through said vapor zone, removed, allowed to cool, and then returned to said vapor zone. and then rinsing the article in the vapor zone with the second liquid mixture produced by condensing the vapor from the vapor zone directly onto the cooled article.

Another variation of the nature is that the first liquid mixture and the second liquid mixture do not have a common vapor zone and are in separate compartments from each other, and the heated first liquid mixture The condensate from the vapor above the liquid mixture is returned to the heated second liquid mixture.

One suitable type of apparatus that may be used in the present method is shown in the accompanying drawing (Figure 1), which is an illustrative vertical cross-sectional view of said apparatus and does not represent the relative exact dimensions of the various parts. .

In FIG. 1, a cleaning container 1 is divided into a reservoir compartment 2 and a rinsing compartment 4 separated by a partition 3.

The sump compartment 2 contains the mixture having said tenth azeotrope-forming ability at a depth sufficient to immerse the contaminated article in this compartment and is equipped with a heater 5. .

A rinsing compartment 4 located adjacent to the sump compartment 2 is also provided with a heater 6 and comprises said second liquid of a different composition than the liquid mixture in said sump compartment 2. It is accommodated by volume.

The steam zone 7 communicates with both the sump compartment 2 and the rinse compartment 4.

A cooling coil 8 together with a gutter 9 is installed in the steam zone 7 to condense the steam.

This gutter 9 is for collecting condensate, and the pipe 10
This is for returning the condensate to the rinse chamber 4.

A cooler 11 can be mounted on the outside of the vessel and a cooling medium can be passed through this cooling passage to provide additional cooling.

an inlet 12 for supplying said substantially azeotropic mixture;
will be established.

Although this inlet is shown in the drawings as leading into the reservoir compartment 2, it could be located to supply the mixture to the system from any convenient point of collapse.

Means (not shown) are also provided for transporting contaminated articles through the device, the passage trajectory of the articles ending at the inlet point 13.
It is represented by a straight line starting from , which is guided through the sump compartment 2 , the steam zone 7 and the rinsing compartment 4 and ends at the withdrawal point 14 .

In operating the process, the solvent mixture in both compartments 2 and 4 is heated and the vapors produced from both compartments are mixed in the vapor zone, condensed on the cooling coil 8, and as a liquid in the rinse zone. Return it to Room 4.

Excess liquid from this rinsing compartment 4 flows over the partition 3 into the sump compartment 2.

This continuous flow of liquid and vapor maintains the rinse fluid in the rinse compartment 4 and ensures that contaminants do not collect in the sump compartment 2.

This reservoir compartment may also be cleaned of contaminants in any convenient manner, such as by periodically removing all or part of the soiled liquid.

If necessary, by adding fresh solvent mixture, the level of the liquid level is maintained constant to eliminate losses in the solvent mixture, i.e., the amount thus removed, the amount reduced by evaporation, and the amount deposited on the articles being cleaned. Compensate for the amount taken out.

The invention will be illustrated by the following examples, but the invention is not limited thereto.

EXAMPLE 1 The material to be cleaned consists of a printed circuit board made of resin-bonded paperboard with deposits of flux attached.

The flux coating layer was formed by applying one coat of flux to the circuit board, followed by drying at 70°C for 2 minutes, dip soldering at 250°C for 5 seconds, and then waiting for 15 minutes. It is something.

Fluxing agent: Zeva C4, Frys
R8, Fry's S64, Multicore
e) PC25, Alpha' 711
, an activated rosin-based flux commercially available under the trademarks Alpha 809 and Alpha 862.

The cleaning method is as described above and consists of immersing the contaminated article in the sump compartment of the cleaning chamber for 1 minute followed by 10 seconds in the adjacent rinsing compartment.

The solvent mixture in the reservoir compartment consists of 1.1.2-) IJ chloro 2.2-trifluoroethane containing 23-24.5% by weight of isopropanol.

The solvent mixture in the rinse tank consisted of 94.6 wt% trichlorotrifluoroethane and 5.4 wt% isopropanol.

Both liquid mixtures are maintained at a boil.

The vapor above the liquid level is condensed by a cooling coil, and the condensate is returned to the rinse tank.

An azeotrope of the trichlorotrifluoroethane and the alcohol is additionally fed into the sump compartment at a rate to maintain the liquid level in the sump compartment.

Through this cleaning process, all fluxing agent residues are removed.
It was removed without damaging the circuit board.

Example 2 The materials to be cleaned and the cleaning method are as described in Example 1, but differ from Example 1 in the following respects: (1) The solvent mixture in the reservoir compartment is 1 containing 25.5% by weight of industrial methanol-denatured spirits (96% by weight of ethyl alcohol and 4% by weight of methyl alcohol)
- Consists of 1,2-trichloro-1,2,2-trifluoroethane.

(11) The solvent mixture in the rinse tank is 94.6% by weight.
1,1,2-trichloro-1,2,2-trifluoroethane and 5.4% by weight of industrial methanol-denatured spirit.

(lil) The additional azeotrope supplied to the reservoir chamber is 9
6.2% by weight of 1,1,2-trichloro-1,2,2-
Contains trifluoroethane and 3.8% by weight of industrial methanol denatured spirit.

This cleaning process removed all traces of flux residue without damaging the circuit board.

Example 3 The materials to be cleaned and the cleaning method are as described in Example 1, but differ from Example 1 in the following respects: (i) The solvent mixture in the sump compartment is 22.5 ml. ~23
1,1,2-trichloro-1,2,2-) IJ fluoroethane containing % by weight of isopropanol.

(1;) Two rinse tanks were used, the tank adjacent to the sump compartment containing 5.4% by weight of isopropanol and the other tank away from the sump compartment containing 4.7% by weight.
Contains % by weight of isopropanol.

This cleaning process removed all traces of flux residue without damaging the circuit board.

Examples of embodiments of the method of the present invention are listed as follows: (1) Feed of a substantially azeotropic mixture of a fluorochlorocarbon solvent and a co-solvent, or a substantially azeotropic mixture; Introducing continuously or intermittently into the system from an external source, feeds of both solvents, delivered separately in appropriate proportions corresponding to .

(2) immersing the contaminated article in said heated first liquid mixture contained in one sump compartment of said cleaning system, followed by one rinsing compartment of said system; passing the article to be treated into a second liquid mixture in the chamber, said first liquid mixture and said second liquid mixture having a common vapor zone.

(3) also heating the second liquid mixture;

(4) The fluorochlorocarbon solvent and the co-solvent are continuously or intermittently delivered to the purifier system in a substantially azeotropic mixture or in suitable proportions corresponding to a substantially azeotropic mixture. Introduce it into the reservoir and/or rinse room.

(5) Returning at least a portion of the liquid obtained by condensing the vapor from the common vapor zone to the rinse compartment.

(6) The liquid mixture overflows from said rinse compartment into said sump compartment.

(7) The first liquid mixture capable of forming an azeotrope contains a co-solvent in an amount greater than the co-solvent concentration corresponding to the azeotrope itself by at least 5 parts by weight per 100 parts by weight of the total mixture. Contain.

(8) The first liquid mixture capable of forming an azeotrope contains a co-solvent in an amount greater than the co-solvent concentration corresponding to the azeotrope itself by at least 10 parts by weight per 100 parts by weight of the total mixture. Contain.

(9) The article to be cleaned is a printed circuit or a component thereof contaminated with flux residue.

(10) The fluorochlorocarbon must contain 2 or 3 carbon atoms.

συ Fluorochlorocarbon shall be 1,1,2-trichloro-1,2,2-trifluoroethane.

(12) The co-solvent is an alcohol having 1 to 4 carbon atoms.

(13) Alcohol must be ethyl alcohol.

(14) Alcohol must be methyl alcohol.

(15) Alcohol must be tertiary butanol.

(116) Alcohol is inpropyl alcohol.

(17) The concentration of isopropyl alcohol in the first mixture capable of forming an azeotrope is lower than 70% by weight of the mixture.

08) The concentration of isopropyl alcohol in the mixture capable of forming an azeotrope is 10 to 40% by weight of the mixture.

σ9) The concentration of isopropyl alcohol in the mixture capable of forming an azeotrope is 22 to 27% by weight of the mixture.

(20) The second liquid mixture in the rinse compartment has a concentration ranging from a value corresponding to the cosolvent concentration of the azeotrope to a value that is no more than 11% by weight greater than the cosolvent concentration of the azeotrope. Must have an auxiliary solvent.

(2υ The second liquid mixture in the rinse chamber is supplemented with a concentration ranging from a value corresponding to the co-solvent concentration of the azeotrope to a value not more than 5% by weight greater than the co-solvent concentration of the azeotrope. Contains a solvent.

(22) The concentration of Impropatool in the first liquid mixture in the sump compartment is 10-70% by weight, and the concentration of Impropatool in the second liquid mixture in the rinse compartment is an azeotrope. Concentrations ranging from isopropatool to 14% by weight of inpropatool.

(23) the concentration of Improper Tool in the first liquid mixture in the reservoir compartment is 22-27% by weight of said liquid mixture; and the concentration of Improper Tool in the second liquid mixture in the rinse compartment; ranges from the azeotrope isopropanol concentration up to 7% by weight isopropanol concentration.

(24) The concentration of ethyl alcohol in the first liquid mixture in the liquid reservoir compartment is 25-30% by weight.

The concentration of ethyl alcohol in the second liquid mixture in the rinsing compartment should be between 5 and 8% by weight.

(26) The concentration of methyl alcohol in the first liquid mixture in the reservoir compartment is 17-22% by weight.

(27) The concentration of methyl alcohol in the second liquid mixture in the rinse compartment is 8-10% by weight.

(28) The substantially azeotropic mixture introduced into the device system is
Contain the co-solvent at a concentration ranging from the azeotrope concentration to that in the rinse tank.

(29) Introducing the azeotrope itself into the device system.

(30) The azeotrope introduced into the apparatus system consists of 97.1% by weight of 1,1,2-trichloro-2,2-trifluoroethane and 2.9% by weight of isopropanol.

(3υ Use multiple rinse rooms.

(32) The temperature of the liquid mixture in the reservoir compartment and the rinsing compartment should be at least 30°C, up to the boiling point of the mixture.

(33) The temperature of the mixture is at least 40°C, up to the boiling point of the mixture.

(34) The liquid mixture is 1.1.2-trichloro2.
It consists of 2-trifluoroethane and Impropatool, and the temperature of this mixture is within the range of 45 to 50°C.

(35) contacting a contaminated article with said heated first liquid mixture in a cleaning apparatus system having one compartment (a sump compartment), and removing said article from said sump compartment; rinsing said article in said vapor zone with said second liquid mixture initially obtained by withdrawing to an upper vapor zone and condensing vapor from said vapor zone;

(36) After immersion in said heated first liquid mixture, the contaminated article is passed through said vapor zone and removed, allowed to cool and then returned to said vapor zone, and then rinsing said article with said second liquid mixture produced in said vapor zone by condensing vapor from said vapor zone directly onto said cooled article;

(37) The first liquid mixture and the second liquid mixture do not have a common vapor zone and exist in separate compartments, and the heated first liquid Returning condensate from the vapor above the mixture to the heated second liquid mixture.

[Brief explanation of the drawing]

The drawing is an illustrative cross-sectional view of a device suitable for use with water droplets.
2 is a liquid storage compartment, 4 is a rinse compartment, 7 is a steam zone, and 8 is a
represent cooling coils, respectively.

Claims (1)

[Claims] 1. In a method for cleaning contaminated articles, a first single-phase liquid mixture heated to at least 30° C. ( (provided that the concentration of said auxiliary organic solvent in said mixture is higher than the organic solvent concentration of said azeotrope itself), followed by contacting said fluorochlorocarbon solvent with a first rinsing said article with a second single-phase liquid mixture containing said co-solvent in a proportion at least equal to the co-solvent concentration of the azeotrope, but in a proportion lower than that contained in said liquid mixture; The vapor mixture evaporated from the second liquid mixture is cooled and condensed, the liquid mixture obtained by the condensation is supplied to the second liquid mixture, and the liquid mixture is added to the first liquid mixture in proportion to the reduction due to evaporation. A method of cleaning a contaminated article, characterized in that it is supplied from a second liquid mixture.