GB2298430A

GB2298430A - Cleaning composition and method

Info

Publication number: GB2298430A
Application number: GB9503463A
Authority: GB
Inventors: Shinichi Wako; Thomas Wee Sun Lee; Eiichi Mochizuki
Original assignee: Exxon Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 1995-02-22
Filing date: 1995-02-22
Publication date: 1996-09-04
Also published as: GB9503463D0

Abstract

A cleaning composition for electronic components comprises (i) from 70 to 85 parts by volume of a hydrocarbon-containing fluid containing not less than 99% by weight, based on the total weight of the fluid, of hydrocarbons selected from C8 to C15 paraffinic and naphthenic hydrocarbons with 0.5 to 2 parts by volume of normal and iso-paraffins per part by volume of naphthenes; and (ii) from 15 to 30 parts by volume of a substituted alcohol having an alcohol moiety with from 4 to 6 carbon atoms and additionally having as substituents a methyl or ethyl group, and a methoxy or ethoxy group in the C-3 position relative to the hydroxy group; ```the composition being substantially free of any halogen-containing compound. The alcohol may be 3-methyl-3-methoxybutanol. The composition may be used for the removal of residual soldering flux from electronic components.

Description

Cleansing composition and method The present invention relates to fluid cleaning compositions and their use. In particular, the invention is concerned with cleaning compositions for use, for example, in cleaning residual flux from electronic components.

As cleaning solvents for removal of residual flux from electronic components, for example, printed circuit boards (referred to herein as "PCBs"), there have previously been used halogenated solvents, especially the chlorofluorocarbon CFC-113. Irrespective of the soldering process employed, flux residues comprising organic resin and decomposed inorganic contaminants remain on the PCBs after soldering and must be removed to ensure proper functioning of the boards. Previously, the contaminated boards have been subjected to immersion cleaning followed by vapour cleaning in CFC-113, which is effective in cleaning both organic resin residues and inorganic contaminants. CFC-113 is, however, known to be harmful to the ozone layer, and it is likely that its use will be phased out in many countries in the near future.

There is a need for a cleaning composition that, whilst being effective in cleaning both organic and inorganic residues, does not have the detrimental effect on the ozone layer that is associated with CFC-113.

W093/13246 (Exxon) describes a cleaning composition comprising a mixture of a hydrocarbon fraction and an alcohol.

WO91/06690 (Henkel) describes a cleaning composition comprising a mixture of one or more aliphatic hydrocarbons with one or more organic compounds having one or more polar groups. The organic compound with the polar group may be an alcohol.

Japanese Patent Specification No. 05-140593 (Nippon Petrochemicals) describes a cleaning composition for precision parts, for example, for cleaning machine, electronic or electrical parts, containing a hydrogenated olefin oligomer and, optionally, a compound selected from alcohols, esters and ethers having 3 to 18 carbon atoms, compounds of the general formula R-OCnH2n OH (in which n may be an integer of 1 to 4), surfactants and aprotic solvents. The olefin oligomer is obtained by polymerisation of an olefin having up to ten carbon atoms and hydrogenation of the polymerisation product so obtained.

Japanese Patent Specification 61-293274 (Ricoh) describes a cleaning composition for cleaning printing machines comprising a kerosene fraction and one or more compounds selected from dipropylene glycol monomethyl ether, 3-methoxybutanol and 3-methyl-3-methoxybutanol.

The composition is used in remcval of ink and etching solution used in offset printing.

WO93/02173 (Henkel) describes a water miscible cleaning composition including diacetone alcohol.

The present invention provides a cleaning composition for cleaning electronic components, comprising (i) from 70 to 85 parts by volume of a hydrocarboncontaining fluid containing not less than 99% by weight, based on the total weight of the fluid, of hydrocarbons selected from C8 to C15 paraffinic and naphthenic hydrocarbons with 0.5 to 2 parts by volume of normal and iso-paraffins per part by volume of naphthenes; and (ii) from 15 to 30 parts by volume of a substituted alcohol having an alcohol moiety with from 4 to 6 carbon atoms and additionally having as substituent a methyl or ethyl group, and a methoxy or ethoxy group in the C-3 position relative to the hydroxy group; the composition being substantially free of any halogen-containing compound.

Advantageously, the composition comprises from 70 to 80 parts of component (i) and from 20 to 30 parts of component (ii).

The composition of the invention has improved solvency and cleaning properties, as compared with known cleaning compositions. Further, the composition has low odour.

The hydrocarbon-containing fluid advantageously has a distillation boiling range at atmospheric pressure of which the lower limit is preferably not less than 150"C and the upper limit is preferably not more than 250"C.

For example, the hydrocarbon component may have a distillation boiling range of 160 to 240 C. The fluid may be a petroleum distillation fraction, which may be used without further treatment. The lower limit of the distillation boiling range of the mixture of the hydrocarbon component and substituted alcohol is advantageously not less than 130"C at atmospheric pressure. The upper limit of said boiling range is advantageously not more than 300"C at atmospheric pressure. The distillation boiling range of the mixture may be, for example, 135"C to 250"C. The kauri-butanol value of the mixture is advantageously at least 60. The viscosity of the mixture at 25"C is advantageously not more than 1.65cSt.

The hydrocarbon-containing fluid is preferably a mixture of paraffinic and naphthenic hydrocarbons having 20 to 35% by volume of normal paraffins, 20 to 35% by volume iso-paraffins and 35 to 55% by volume of naphthenes. That combination of hydrocarbons provides particularly good solvation of the resinous flux residue that, typically, is adhered to the electronic components, for example, PCBs. The hydrocarbon-containing fluid may have an aromatics content of not exceeding 1%, by weight, based on the combined aromatics and hydrocarbon content.

Advantageously, the cleaning composition comprises not more than 5 ppm of halogen, in terms of weight.

As already mentioned, the cleaning composition comprises from 20 to 30 parts by volume of a substituted alcohol. As alcohol there may be used an aliphatic alcohol having a straight chain alcohol moiety with from 4 to 6 carbon atoms. Advantageously, the aliphatic radical is saturated. The alcohol is substituted in the C-3 position relative to the hydroxy group by a methoxy or ethoxy group. A methyl or ethyl substituent may also be present, advantageously also at the C-3 position relative to the hydroxy group. The substituted alcohol is advantageously a 3-alkyl-3-alkoxybutanol, in which the alkyl group is methyl or ethyl and the alkoxy group is methoxy or ethoxy. Preferably, the alcohol is 3 -methyl-3 -methoxybutanol.

The alkoxy alcohols increase the polarity of the cleaning composition and thus help to reduce or eliminate the inorganic contaminants normally present on soldered electronic components such as PCBs.

The invention further provides a method of removing soldering flux residues from an electronic component comprising treating the article with a cleaning composition comprising (i) from 70 to 85 parts by volume of a hydrocarboncontaining fluid containing not less than 99% by weight, based on the total weight of the fluid, of hydrocarbons selected from C8 to C15 paraffinic and naphthenic hydrocarbons; and (ii) from 15 to 30 parts by volume of a substituted alcohol having an alcohol moiety with from 4 to 6 carbon atoms and additionally having as substituent a methyl or ethyl group, and a methoxy or ethoxy group in the C-3 position relative to the hydroxy group; the composition being substantially free of any halogen-containing compound.

In the method of the invention, electronic components, for example, PCBs, can be cleaned, with effective removal of flux residues, by immersion of the boards, with or without agitation of the solvent by, for example, mechanical or ultrasonic means. The combination of non-polar hydrocarbons with the polar alcohol derivative gives excellent cleaning in relation to residual resin flux and inorganic contaminants. The temperature of the cleaning composition may be in the range of from 20"C to 75"C, advantageously at ambient temperature (25"C). The article is advantageously kept immersed in the composition for from 5 to 10 minutes.

The cleaning composition may be applied to the articles by solvent spraying. After said immersion step or after said spraying, the PCBs may be washed with fresh cleaning composition.

Following application of the solvent to the article, the cleaning composition may be permitted to drain from the article and the article may be dried, for example, under vacuum or by subjecting it to a stream of warm air.

The invention further provides the use, to remove soldering flux residues from an article, of a cleaning composition comprising (i) from 70 to 85 parts by volume of a hydrocarboncontaining fluid containing not less than 99% by weight, based on the total weight of the fluid, of hydrocarbons selected from C8 to C15 paraffinic and naphthenic hydrocarbons; and (ii) from 15 to 30 parts by volume of a substituted alcohol having an alcohol moiety with from 4 to 6 carbon atoms and additionally having as substituent a methyl or ethyl group, and a methoxy or ethoxy group in the C-3 position relative to the hydroxy group; the composition being substantially free of any halogen-containing compound.

The solvent mixture used in accordance with the invention enables use of halogen-substituted organic compounds to be avoided whilst nevertheless obtaining high quality cleaning.

The following Example illustrates the invention.

Example A cleaning composition was prepared by mixing 80 volume % of a hydrocarbon fluid consisting essentially of C8 to C15 hydrocarbons (20 to 30% of which were normal paraffins, 20 to 35% of which were iso-paraffins and 35 to 55% of which were naphthenic compounds) with 20 volume % of 3-methyl-3-methoxybutanol. PCBs were soldered using liquid flux and heated at 240"C for 2 minutes. The boards, which were contaminated with residual flux, were immersed in a first bath of the cleaning composition, the temperature of the cleaning composition being 25"C, and the composition being subjected to ultrasonic agitation during immersion.

After 5 minutes, the boards were removed from the first bath and immersed in a second bath of fresh cleaning composition at 25"C and under ultrasonic agitation. The boards were removed from the second bath after 5 minutes and dried by subjecting them to a stream of air at 35"C for 60 seconds.

To determine the cleaning efficiency of the composition, the flux residue remaining on the boards after cleaning was compared with the flux residue present on boards before cleaning. That was done by repeated extraction of the flux residue using a spectro-grade alcohol and comparing the UV absorbance of the liquid extracts taken from boards which had been cleaned with those from boards which had not been cleaned. The UV absorbance quantifies the resin content of the flux.

Results indicated the average cleaning efficiency using the composition of the invention was 97%. That represents improved cleaning as compared to other known cleaning compositions or fluids. Thus, by way of example, the cleaning composition described in WO93/13246 gave an average cleaning efficiency (resin removal) of 87%, and the conventionally used CFC fluid gave an average cleaning efficiency (resin removal) of 61%.

Claims

1. A cleaning composition for cleaning electronic components comprising (i) from 70 to 85 parts by volume of a hydrocarboncontaining fluid containing not less than 99% by weight, based on the total weight of the fluid, of hydrocarbons selected from C8 to C15 paraffinic and naphthenic hydrocarbons with 0.5 to 2 parts by volume of normal and iso-paraffins per part by volume of naphthenes; and (ii) from 15 to 30 parts by volume of a substituted alcohol having an alcohol moiety with from 4 to 6 carbon atoms and additionally having as substituents a methyl or ethyl group, and a methoxy or ethoxy group in the Cposition relative to the hydroxy group; the composition being substantially free of any halogen-containing compound.

2. A composition as claimed in claim 1, in which the hydrocarbon-containing fluid has a distillation boiling range of which the lower limit is not less than 150 C.

3. A composition as claimed in claim 1 or claim 2, in which the hydrocarbon-containing fluid has a distillation boiling range of which the upper limit is not greater than 250or.

4. A composition as claimed in any one of claims 1 to 3, which has a distillation boiling range of which the lower limit is not less than 130"C at atmospheric pressure.

5. A composition as claimed in any one of claims 1 to 4, which has a distillation boiling range of which the upper limit is not more than 300"C at atmospheric pressure.

6. A composition as claimed in any one of claims 1 to 5, which has a kauri-butanol value of at least 60.

7. A composition as claimed in any one of claims 1 to 6, in which the substituted alcohol is 3-methoxy3-methylbutanol.

8. A composition as claimed in any one of claims 1 to 7, which comprises from 70 to 80 parts of component (i) and from 20 to 30 parts of component (iij.

9. A cleaning composition substantially as described in the Example herein.

10. A method of removing soldering flux residues from an electronic component comprising treating the article with a cleaning composition comprising (i) from 70 to 85 parts by volume of a hydrocarboncontaining fluid containing not less than 99% by weight, based on the total weight of the fluid, of hydrocarbons selected from C8 to C15 paraffinic and naphthenic hydrocarbons; and (ii) from 15 to 30 parts by volume of a substituted alcohol having an alcohol moiety with from 4 to 6 carbon atoms and additionally having as substituent a methyl or ethyl group, and a methoxy or ethoxy group in the C-3 position relative to the hydroxy group; the composition being substantially free of any halogen-containing compound.

11. A method as claimed in claim 10, in which the component is immersed in said cleaning composition.

12. A method as claimed in claim 11, in which the component is kept immersed in said cleaning composition for from 5 to 10 minutes.

13. A method as claimed in any one of claims 10 to 12, in which the temperature of said cleaning composition is from 20"C to 75"C.

14. A method as claimed in claim 13, in which the electronics component is a PCB.

15. A method as claimed in any one of claims 10 to 14, in which a cleaning composition according to any one of claims 2 to 9 is used.

16. A method of cleaning PCBs substantially as described in the Example herein.

17. The use, to remove soldering flux residues from an article, of a cleaning composition comprising (i) from 70 to 85 parts by volume of a hydrocarboncontaining fluid containing not less than 99% by weight, based on the total weight of the fluid, of hydrocarbons selected from C8 to C15 paraffinic and naphthenic hydrocarbons; and (ii) from 15 to 30 parts by volume of a substituted alcohol having an alcohol moiety with from 4 to 6 carbon atoms and additionally having as substituent a methyl or ethyl group, and a methoxy or ethoxy group in the C-3 position relative to the hydroxy group; the composition being substantially free of any halogen-containing compound.

18. The use as claimed in claim 17 employing a cleaning composition according to any one of claims 2 to 9.