JPH03146597A - Composition for cleaning printed circuit boards - Google Patents

Abstract

PURPOSE:To obtain the title composition containing an aliphatic hydrocarbon and organic compound having a polar group and suitable for eliminating a rosin-based flux without using a halogen-based solvent such as fluorocarbon- based or chlorocarbon-based solvent. CONSTITUTION:The objective composition containing (A) average 8-20C (preferably 8-15C) aliphatic hydrocarbon and (B) polar group-containing organic compound (preferable example; alcohols having <=300 deg.C boiling point such as butanol, polyhydric alcohols such as hexylene glycol, ethers such as ethylene glycol monobutyl ether or esters such as ethyl acetate), preferably containing O or N.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a composition for cleaning printed circuit boards.

2. Description of the Related Art Conventionally, after soldering a printed circuit board, a fluorocarbon-based solvent has been used to remove residual solder substances. However, due to the problem of ozone layer depletion caused by fluorocarbon solvents, efforts are being made to develop cleaning agents that can replace these solvents.

Examples of the above-mentioned alternative cleaning agents include those using surfactants and those using organic solvents. Examples of cleaning agents for printed circuit boards using '11 solvents include JP-A No. 6
There are those that use chlorinated solvents as described in Japanese Patent Publication No. 4-152200, and those that use terpene solvents as in JP-A No. 63-501908, but the former has the problem of groundwater contamination due to chlorinated solvents. The latter is a natural product and it is difficult to stably supply it with a certain quality.
Moreover, it has a characteristic odor and is expensive.

Furthermore, there is a problem in that the removal effect of rosin-based flux, which is commonly used as solder flux, is low if only a commercially available high-boiling hydrocarbon solvent such as light oil or heavy oil is used.

Problems to be Solved by the Invention An object of the present invention is to provide a cleaning composition for printed circuit boards suitable for removing rosin-based flux without using fluorocarbon-based or chlorinated solvents. shall be.

Means for Solving the Problems The present invention provides a method for cleaning printed circuit boards containing an aliphatic hydrocarbon having 8 to 15 hydrocarbons or an aliphatic hydrocarbon having an average hydrocarbon number of 8 to 20 and an organic compound having a polar group. Regarding the composition.

The aliphatic hydrocarbons used in the present invention may be linear or branched, saturated or unsaturated, and may have a cyclic hydrocarbon group; Preferably, the main component is a saturated hydrocarbon group in the chain. Of course, the partial weight should be less than 20% by weight of the total weight, especially 10% by weight.
It may contain up to % by weight of aromatic hydrocarbons, such as toluene, xylene, and other alkylbenzenes.

The aliphatic hydrocarbon has an average carbon number of 8 to 20, preferably 8 to 15, and is a liquid at the cleaning temperature, especially a low viscosity liquid, and is difficult to volatilize at that temperature, but at the drying temperature. Preferably something that can be easily removed.

In the case of a mixed solvent, the average carbon number means the value represented by the sum of the carbon numbers of each component multiplied by its weight composition. Generally, it is preferable to have a mode in the range of 8 to 22.

If there are too many hydrocarbons with a carbon number below the average carbon number, diffusion during cleaning will increase, and conversely, if there are too many hydrocarbons with a carbon number above the average carbon number, it will not only be necessary to increase the drying temperature. The cleaning power of the cleaning agent against rosin-based 7lux decreases, the viscosity increases, and the cleaning effect on the details of the printed circuit board becomes insufficient.

As an aliphatic hydrocarbon, the boiling point is about 100℃~3oo'c
, more preferably about 100°C to 250'C.

Specific examples of preferred aliphatic hydrocarbons include n-octane, n
~ Straight chain hydrocarbons such as nonane, n-decane, n-undecane, n-dodecane, n-tridecane, n-tetradecane, and lopentadecane, or 1so-1sec of these
Hydrocarbons having branches such as -1tert- are exemplified.

As the polar organic compound, a solid or liquid organic compound having an oxygen atom and/or a nitrogen atom in the molecule is preferable. Preferably a liquid with a boiling point of about 100
C. to 300.degree. C., more preferably about 100.degree. C. to 250.degree. C. is suitable.

Examples of preferred organic compounds having polar groups are saturated or unsaturated aliphatic (which may be cyclic) which may have branches, alcohols (which may be polyhydric alcohols), ethers, esters, and ketones. , carboxylic acids, amines, amides, etc., but especially alcohols and esters.

Particularly preferred examples of organic compounds having polar groups include linear or branched alcohols with a boiling point of 300°C or less such as butanol, hexyl alcohol, and decanol, alicyclic alcohols such as cyclohexanol, hexylene glycol, etc. These include polyhydric alcohols, ethers such as ethylene glycol monobutyl ether and ethylene glycol dibutyl ether, and esters such as ethyl acetate.

The organic compound having a polar group interacts with the above-mentioned aliphatic hydrocarbon to effectively remove the rosin-based flux.

The blending ratio of the aliphatic hydrocarbon and the organic compound having a polar group is such that the weight ratio of the latter is 80% by weight or less, more preferably 65% by weight or less. If the blending ratio of the organic compound having a polar group is more than 80%, the resin film portion of the printed circuit board may swell or peel.

The cleaning agent for printed circuit boards of the present invention preferably has a viscosity as low as possible at the operating temperature, a low surface tension, and excellent spreadability and wettability. This effectively removes contaminants from the printed circuit board details. The preferred viscosity is about 50 cp or less, especially 30 cp or less at 25°C.

The cleaning composition of the present invention may further contain other additives.

For example, surfactants may be added to reduce surface tension. Examples of surfactants used for this purpose include hydrocarbon surfactants such as dioctyl sulfosuccinate, silicone surfactants such as modified polydimethylsiloxane, and fluorine surfactants such as perfluoroalkylcarboxylic acid derivatives. is exemplified. The amount of surfactant used for these purposes is 0% of the total composition.
．． 001-10% by weight, more preferably 0°005-5
Weight%. Use of a large amount is not preferable because the surfactant remains as a residue.

Furthermore, as another additive, a corrosion inhibitor such as a copper corrosion inhibitor such as benzotriazole or tolyltriazole may be added as a corrosion inhibitor for the metal surface of the object to be cleaned. The appropriate amount of these corrosion inhibitors added is 0.01 to 5% by weight, more preferably 0.01 to 1% by weight.

To clean a printed circuit board using the cleaning agent of the present invention, the printed circuit board is immersed in the composition heated from room temperature to about 100°C, preferably 30 to 70°C, and depending on the findings, ultrasonic waves,
Cleaning may be performed by using a combination of stirring, shaking, air stirring, and liquid flow, or by spraying, wiping, or the like.

After cleaning, pull up the printed circuit board and leave it to dry.
Alternatively, cleaning may be performed again using the cleaning agent of the present invention or a conventional halogen-based solvent such as a fluorocarbon-based or chlorine-based cleaning agent, or an alcohol-based cleaning agent. In this case, it is preferable not to add a surfactant to the cleaning agent of the present invention because unnecessary substances will not remain on the printed circuit board. Further, the amount of halogen solvent used in the post-cleaning is extremely small compared to the conventional method which uses this from the beginning, and it can be recycled.

Water may be used for subsequent washing. The use of water is particularly useful when there is a large amount of water-soluble material remaining on the printed circuit board or when there is a large amount of fine dust-like residue. The printed circuit board cleaning composition used in such a method may itself contain a surfactant that is emulsifiable in water. Surfactants used for this purpose include ethylene oxide addition type nonionic surfactants, ester type nonionic surfactants of polyhydric alcohols and higher alcohols, alkanolamide type nonionic surfactants, alkylbenzene sulfonates, etc. Examples include anionic surfactants such as alkyl succinates (which may be used in combination). The amount of surfactant to be used is preferably such that the cleaning composition can self-emulsify in water, and is, for example, about 0.1 to 50% by weight, more preferably about 3 to 20% by weight.

Furthermore, if necessary, the printed circuit board that has been subjected to the cleaning treatment may be washed with a solvent that does not easily azeotrope with the cleaning composition, such as ethanol-4.
Steam cleaning may be performed using impropat tool, fluorocarbon solvent, chlorine solvent, etc. In this case, the amount of halogen solvent used in cleaning is extremely small compared to the conventional method that uses this from the beginning, and it is possible to reuse it.

The present invention will be explained below with reference to Examples.

Examples 1 to 6 Compositions for cleaning printed circuit boards were obtained using the formulations shown in Table 1. This cleaning composition was subjected to the following cleaning test to evaluate its cleaning power.

Cleaning test Flux was uniformly applied to the comb-shaped electrode type 2 of the glass cloth base epoxy resin copper-clad laminate and soldered (240℃, 5
sec) Use the second thing as a test history.

The cleaning conditions were immersion or ultrasonic waves, the liquid temperature was 40° C., and the time was 5 minutes. Next, the test piece was heated to a temperature of 40±2℃1
After 96 hours had passed in a constant temperature and humidity chamber with a relative humidity of 90 to 95%, the insulation resistance was measured after 1 minute at 100 V DC.

Other ion residues, visual discoloration and corrosion of the substrate were visually confirmed.

(The following is a blank space) Table XI: Aliphatic hydrocarbon whose main component is n-alkane having 8 to 11 carbon atoms χ2: Aliphatic hydrocarbon whose main component is n-alkane having 8 to 15 carbon atoms POE: Polyoxy The value of 0 ethylene residues indicates the number of moles added. Example 7, Comparative Examples 1 and 2 Compositions for cleaning printed circuit boards were obtained using the formulations shown in Table 2.

This cleaning composition was subjected to the following cleaning test to evaluate its cleaning power. In Comparative Example 1, commercially available light oil was used as a solvent containing a relatively large amount of high-boiling hydrocarbons, and in Comparative Example 2, a fluorocarbon solvent was used, and the tests were conducted in the same manner.

cleaning test It was carried out in the same manner as in Examples 1 to 6 above.

(Hereinafter, blank spaces) Table 1: Aliphatic hydrocarbons mainly composed of n-alkanes having 8 to 11 carbon atoms Effects of No. 2 diesel oil invention as defined by JIS K2204i: Fi When the cleaning agent of the present invention is used, halogen Rosin-based 7 lux on printed circuit boards can be effectively removed without using any solvent.

Claims (10)

[Claims] 1. A cleaning composition for printed circuit boards containing an aliphatic hydrocarbon having an average carbon number of 8 to 20 and an organic compound having a polar group. 2. The composition for cleaning printed circuit boards according to claim 1, wherein the aliphatic hydrocarbon has 8 to 15 carbon atoms. 3. The composition for cleaning printed circuit boards according to claim 1, wherein the aliphatic hydrocarbon has a boiling point of 100°C to 300°C. 4. The composition for cleaning printed circuit boards according to claim 1, wherein the aliphatic hydrocarbon is a linear aliphatic hydrocarbon. 5. The composition for cleaning printed circuit boards according to claim 1, wherein the organic compound having a polar group contains an oxygen atom or a nitrogen atom. 6. An organic compound with a polar group has a boiling point of 100℃/760℃
2. The cleaning composition for printed circuit boards according to claim 1, which is selected from alcohol, polyhydric alcohol, ether, ester, carboxylic acid, or ketone having a temperature of 200 DEG C./10 mm. 7. The organic compound having a polar group is an aliphatic or alicyclic alcohol having 4 to 20 carbon atoms, a polyhydric alcohol, or a carbon number 4
~20 aliphatic or cycloaliphatic ethers or 4 carbon atoms ~
The cleaning composition for printed circuit boards according to claim 1, which is selected from 20 aliphatic, aliphatic or alicyclic esters having 4 to 20 carbon atoms, or aliphatic or cycloaliphatic ketones having 4 to 20 carbon atoms. 8. 0 to 0 organic compounds with polar groups on aliphatic hydrocarbons
The printed circuit board cleaning composition according to claim 1, containing 80% by weight. 9. The cleaning composition for printed circuit boards according to claim 1, which has a viscosity of 200 cp or less (25°C). 10. A cleaning composition for printed circuit boards, which further contains a surfactant in the composition according to claim 1.