WO1991006690A1

WO1991006690A1 - Mixture for cleaning printed circuit boards

Info

Publication number: WO1991006690A1
Application number: PCT/EP1990/001925
Authority: WO
Inventors: Tooru Amada; Tadahiko Morihana
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1989-11-01
Filing date: 1990-10-29
Publication date: 1991-05-16
Also published as: JPH03146597A

Abstract

The invention relates to a mixture for cleaning printed circuit boards containing both one or more aliphatic hydrocarbons with an average number of carbon atoms of 8 to 20 and one or more organic compounds with one or more polar groups.

Description

Mixture for cleaning; of printed circuit boards

The present invention relates to a mixture for cleaning printed circuit boards (printed circuit boards).

Hitherto, chlorofluorohydrocarbons have been used to remove remaining soldering fluxes which adhere to printed circuit boards after soldering. In view of the problem of the destruction of the ozone layers by the chlorofluorohydrocarbons, efforts have been made to develop alternative cleaners.

Examples of alternative solvents are those which use surfactants, those which use organic solvents, etc. are known. Examples of cleaners of the organic solvent type are those which use chlorine-containing solvents, such as are described, for example, in Japan Tokkyo Kokai Koho Sho64-152200, and those which use terpene solvents, as are used, for example, in Japan Kokai Kokkyo Koho Sho64-501908, etc. are known. The former are problematic with regard to contamination of the groundwater by chlorine-containing solvents, while in the latter there is a difficulty in maintaining the supply of a constant quality product since it is a natural product; there are also problems with the characteristic smell and the high price. On the other hand, commercially available high-boiling hydrocarbon-type solvents such as gas oils, heavy oils, etc. alone have little effect on the removal of the rosin-type soldering flux, as are generally used. The present invention aims to provide a mixture for cleaning printed circuit boards (printed circuit boards) which is suitable for the removal of rosin type soldering fluxes without using halogen-containing solvents such as chlorofluorocarbon solvents or chlorine-containing solvents .

The present invention relates to a mixture for cleaning printed circuit boards (printed circuit boards) containing one or more aliphatic hydrocarbons with an average number of carbon atoms from 8 to 20 and one or more organic compounds with one or more polar groups.

The aliphatic hydrocarbons which can be used for the present invention can be either straight-chain or branched, either saturated or unsaturated and also those with one or more alicyclic hydrocarbon group (s), but those with one or more straight-chain or saturated hydrocarbon groups Group (s) preferred as the main component. They can natur¬ according to ^~ part of less than 20 wt .-%, especially 10 wt .-%, containing aromatic hydrocarbons such as toluene, xylene and other alkyl benzenes, etc ..

With regard to the carbon number of the aliphatic hydrocarbons, an average carbon number of 8 to 20, in particular 8 to 15, is preferred; such a liquid is desired which is preferably low viscosity and less volatile at the cleaning temperature, while it can be easily removed at the drying temperature.

In the case of a solvent mixture, the average carbon number means the value of the sum of the products from the carbon number each (hydrocarbon) component and the corresponding weight proportion in the mixture. Generally a value in the range of 8 to 22 is recommended.

The excessive presence of hydrocarbons with a carbon number smaller than 8 would cause an increase in evaporation during cleaning; conversely, the excessive presence of hydrocarbons with a carbon number greater than 23 would not only lead to a need to increase the temperature of the drying, but also to a decrease in the cleaning power of the cleaner for fluxes of the rosin type as well also to reduce the cleaning effect on details of the printed circuit boards due to the increase in viscosity.

Aliphatic hydrocarbons with a boiling point from 100 ° C. to 300 ° C., preferably from 100 ° C. to 250 ° C., are suitable.

Specific examples of preferred aliphatic hydrocarbons are embodied by straight-chain hydrocarbons such as n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane etc. or their branched (isomers ) Forms of the type of iso-, sec-, tert- etc. hydrocarbons.

As organic compounds with one or more polar groups, either solid or liquid organic compounds with oxygen and / or nitrogen atom (s) within the molecule are preferred. Liquids are preferred (over solid substances); suitable are those having a boiling point of about 100 ^β C to 300 ° C, more preferably from about 100 ° C to 250 ° C. Specific examples of particularly preferred organic compounds with one or more polar groups are those with an alcohol group and with a boiling point below 300 ° C., ie straight-chain alcohols such as butanol, hexyl alcohol, decanol etc. and their branched isomers, those with an alicyclic alcohol group, exemplified by cyclohexanol, those with multiple alcohol groups, exemplified by hexylene glycol, those with an ether group, exemplified by ethylene glycol monobutyl ether, ethylene glycol dibutyl ether, etc., and those with an ester group , exemplified by ethyl acetate etc.

Organic compounds with one or more polar groups, when combined with the aliphatic hydrocarbons mentioned above, show a synergistic effect in the removal of fluxes of the rosin type.

The mixing ratio of the organic compounds with polar groups to the aliphatic hydrocarbons is set so that the former make up less than 80% by weight, preferably less than 65% by weight, of both. If the percentage by weight of the organic compounds exceeds 80%, the resin film part of the printed circuit boards with the printed circuits may swell or flake off.

Among the circuit board cleaners covered by the present invention, preferred are those whose viscosity is as low as possible at the application temperature, which have a low surface tension and which are excellent in both penetration and wetting power. In this way, an effective removal of dirt on the individual parts of the plates with the printed circuits can be achieved. The value of the viscosity is preferably below approx. 50 mPa.s (50 cP), and more advantageously below 30 mPa.s (30 cP) at 25 ° C.

Detergent mixtures of the present invention may further contain other additives. For example, surfactants can be added to lower the surface tension. Surfactants which can be used for this purpose are, for example, hydrocarbon surfactants such as dioctylsulfosuccinate, surfactants of the silicone type such as modified polydimethylsiloxane, fluorine-containing surfactants such as perfluoroalkylcarbonic acid derivatives and others. The content of these surfactants to be used for the stated purpose is 0.001 to 10% by weight, more preferably 0.005 to 5% by weight, of the total composition. Excessive use of surfactants is not recommended as these remain in the residues.

As another type of additives, anti-corrosion agents can be used to inhibit corrosion on the metallic surface of the object to be cleaned, for example copper corrosion inhibitors such as benzotriazole; Tolyltriazole etc. A suitable concentration range for these corrosion inhibitor additives comprises 0.01 to 5% by weight, more preferably 0.01 to 1% by weight.

In the practice of cleaning boards with the printed circuits using a cleaner of the present invention, the printed circuit boards are immersed in the cleaner mixture, which is between room temperature and about 100 ° C., preferably between 30 ° C. and 70 ° C. if desired, additional ultrasound, stirring, vibration, air blowing, liquid circulation can be carried out at the same time, or cleaning can be carried out by spraying, wiping, etc. After cleaning, as in the preceding, the circuit boards can either be removed (from the cleaner bath) and simply dried, or they can be cleaned again using the same cleaner (bath) or conventional halogen-containing solvents such as chlorofluorocarbons or chlorine-containing cleaners or cleaners alcohol-type. In this case, a cleaner of the present invention containing no surfactant is preferable because otherwise undesirable substances may remain on the circuit boards. In addition, the amount of halogen-containing solvents used for the second cleaning is extremely small compared to that in the conventional method; In addition, it is also possible to reuse the solvents recycled in the circuit.

Water can also be used for this rinsing. The use of water is particularly advantageous if either a considerable amount of water-soluble substances remain on the printed circuit boards or if fine dust-like residues are present there in large quantities. A cleaner mixture for printed circuit boards which is adapted to this procedure can itself contain surfactants for emulsification with water. Surfactants that can be used for this purpose are, for example, surfactants of the non-ionic type with added ethylene oxide, non-ionic surfactants of the ester type with polyhydric alcohols / higher alcohols, non-ionic surfactants of the alkanolamide type, anionic surfactants such as alkylbenzenesulfonates, alkyl succinates, etc. (and where possible their mixtures). The content of such a surfactant of, for example, 0.1 to 50% by weight, more preferably 3 to 20% by weight, gives a good result and actually corresponds to the amount that the detergent mixture needs for automatic emulsification Water enabled. Furthermore, the printed circuit boards, after having been subjected to the above treatment, can be steam cleaned, if necessary, using a solvent that hardly azeotropically distils with the detergent mixture, for example ethanol, isopropanol, chlorofluorocarbons, chlorine-containing solvents, etc. In this case the amount of halogen-containing solvents used for this cleaning is extremely small compared to that in the conventional method in which the solvents are used from the beginning; Furthermore, it is also possible to reuse the solvents recycled in the circuit.

The present invention is explained below on the basis of practical examples.

PRACTICAL EXAMPLES 1 to 6:

TABLE 1 shows the formulations of cleaner mixtures for printed circuit boards. The cleaning power of these cleaner mixtures was determined using the following cleaning test:

Cleaning test:

As a specimen plates were used which had been made of a epoxy resin impregnated with glass fabric and stretched copper foil laminated and having the two comb-shaped electrodes and uniformly coated with solder flux and solder (240 ^C C; 5 sec) were. The cleaning test was carried min either by immersion or by Ultra¬ supersonic treatment at a bath temperature of 40 C for a period of ^β. 5 The test specimens were then placed in a climatic chamber, which was kept at a temperature of 40 + 2 ° C and a relative humidity of 90 to 95%. After 96 h, the value of the insulation resistance was measured 1 min after applying a DC voltage load of 100 V. In addition, ionic residues were measured, and possible discoloration and corrosion of the plates were checked with the naked eye.

PRACTICAL EXAMPLE 7, COMPARATIVE EXAMPLES 1 and 2:

TABLE 2 shows the formulations of detergent mixtures for printed circuit boards. The cleaning power of these cleaner mixtures was determined using the following cleaning test. In the same way, according to COMPARATIVE EXAMPLE 1, a commercially available gas oil as solvent, which contained relatively large amounts of high-boiling hydrocarbons, and according to COMPARATIVE EXAMPLE 2, a chlorofluorocarbon solvent were tested.

Cleaning test:

This was carried out using the same method as in practical examples 1 to 6.

Effect of the present invention

Colophonium-type soldering fluxes on printed circuit boards can be removed effectively by the cleaner mixtures of the present invention without the need for halogen-containing solvents.

TABLE 1

P R A K T I S C H E B E I S P I E L E 1 2 3 4 5 6

C ₈ to C _u * 1 100 90 87 80 10

C to C * 2 50 40 8 15

Cyclohexanol 10 10 15 50 ethyl carbitol 50

P0E (7) nonylphenol P0E (7) coconut oil alcohol

Test result:

Surface insulation

13 13 13 13 13 13 resistance [O]>10> 10 ⁱ > 10 ^1J >10>10> 10

Ionic residues [/ «/ cm] 0.4 <0.4 <0.4 <0.4 <0.4 <0.4

Discoloration (copper) none none none none none none

Corrosion none none none none none none

* 1 Aliphatic hydrocarbons with n-alkanes with the carbon number 8 to 11 as the main component

* 2 Aliphatic hydrocarbons with n-alkanes with the carbon number 8 to 15 as the main component

POE: The value in () is the amount of substance (mol number) of the added polyoxyethylene residues TABLE 2

PRACTICAL COMPARATIVE EXAMPLE EXAMPLES 7 1 2

Chlorofluorocarbon 1 1 3 90

C to C, * 1 89.9 8 11

Gas oil No. 2 * 3 100

Isopropyl alcohol methyl acetate

Octylamine 5

Octyl carboxylic acid 5

Benzotriazole 0.1

Test result: surface insulation

13 resistance [Ωj> 10 ionic residues

Discoloration (copper) none none none corrosion none none none

* 1 Aliphatic hydrocarbons with n-alkanes with the carbon number 8 to 11 as the main component * 3 No. 2 gas oil according to Japanese industrial standard JIS K 2204

Claims

Patent claims

1. Mixture for cleaning printed circuit boards (printed circuit boards) containing both one or more aliphatic hydrocarbons with an average number of carbon atoms from 8 to 20 and one or more organic compounds with one or more polar groups.

2. A mixture for cleaning printed circuit boards according to claim 1, wherein the hydrocarbon (s) has 8 to 15 carbon atoms.

3. Mixture for cleaning printed circuit boards according to claim 1, wherein the hydrocarbon (s) has a boiling temperature of 100 ° C to 300 ^β C / have.

4. Mixture for cleaning printed circuit boards according to claim 1, wherein the hydrocarbon (s) is / are one or more straight-chain hydrocarbons.

5. A mixture for cleaning printed circuit boards according to claim 1, wherein the organic compound (s) with one or more polar groups contains either one or more oxygen atoms or one or more nitrogen atoms.

6. Mixture for cleaning printed circuit boards according to claim 1, wherein the organic compound (s) with one or more polar groups of alcohols, polyhydric alcohols, ethers, esters, carboxylic acids or ketones with boiling temperatures of 100 "C at 1.0135 bar (760 mm Hg) up to 200 ° C at 13.3 mbar (10 mm Hg) is / are selected.

7. Mixture for cleaning printed circuit boards according to claim 1, wherein the organic compound (s) with one or more polar groups of aliphatic or alicyclic alcohols / polyhydric alcohols with a carbon number of 4 to 20, aliphatic or ali ¬ cyclic ethers with a carbon number of 4 to 20, aliphatic or alicyclic esters with a carbon number of 4 to 20 or aliphatic or alicyclic ketones with a carbon number of 4 to 20 is / are selected.

8. Mixture for cleaning printed circuit boards according to claim 1, wherein the polar group (s) of the organic compound (s) are linked to a / mehre¬ ren inorganic hydrocarbon (s) and the content of the organic compound (s) 0 is up to 80%.

9. A mixture for cleaning printed circuit boards according to claim 1, wherein the viscosity of the mixture is less than 200 mPa.s (200 cP) at 25 ° C.

10. Mixture for cleaning printed circuit boards according to claim 1, wherein one or more surfactants are additionally contained.