CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Provisional Application Ser. No. 61/423,647 filed Dec. 16, 2010.

FIELD OF THE INVENTION

This invention related to a composition and method for removing solder flux.

BACKGROUND

Solder is used in the manufacture of electronic parts, electronic assemblies, and equipment used in the manufacturing of electronic assemblies. This, inevitably, results in the deposition of solder flux, regardless of the type of solder used. Any and all of these components, assemblies, and equipment used in the manufacture of assemblies must be pristine clean in order to avoid malfunction at a later date.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, a composition is provided which is effective for removing solder flux either as a concentrated material or diluted with water. The composition is effective to remove, in a single step, all types of solder fluxes including, rosin type, resin type, no-clean, low residue, lead-free, organic acid and water soluble soldering fluxes. The composition exhibits excellent cleaning and rinsing properties with polar rinse agents such as water and alcohols. The composition comprises tripropylene glycol butyl ether (TPGBE) and an alkali and has a pH of at least about 7.5 and, preferably, greater than 7.5. Optionally the concentrated composition may have a secondary solvent system that is added with the TPGBE to make the total amount of solvent in the concentrated composition range from 0.01 to 99.99 weight percent, and preferably from 30 to 99.99% weight percent. Conversely the alkali may range from 0.01% to 70 weight percent. Optionally up to 10 percent, preferably up to 3 percent, of a non-ionic surfactant may be added to the concentrated composition to assist in cleaning efficacy. Optionally corrosion inhibitors, buffering agents, chelating agents and/ or sequestrants my be added as would be known by one skilled in the art. The concentrated composition may be used neat (at 100%) or diluted with water to result in a concentration of the composition from 99.1 weight percent to 0.1 weight percent concentration of the concentrate composition. The dilution of the concentrate will allow use in multiple styles of cleaning machines. The concentration of the composition is an amount effective to dissolve, remove and clean soldering flux.

The present invention also contemplates a method of removing solder flux by contacting a substrate containing the solder flux in a single step with the composition of the invention. In this context, Asubstrate@ is defined as any electronic part, electronic assembly, or equipment used in the manufacturing of electronic assemblies.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the invention, novel cleaning compositions have been formulated comprising TPGBE and one or more alkaline agents that render the pH of the concentrated cleaning composition greater than 7.5. Optionally, the composition contains one or more additional solvents, non-ionic surface active agents, corrosion inhibitors, chelation or sequestering agents, pH buffering agents, or agents that modify the foaming characteristics, as known by those skilled in the art. Each of these additives may comprise one agent or a mixture of agents in order to impart the desired characteristic to the final cleaning composition. The concentrated composition may be used neat (at 100%) or diluted with water to result in a concentration of the composition from 99.9 weight percent to 0.1 weight percent of the concentrate composition. The dilution of the concentrate will allow use in multiple styles of cleaning machines. The concentration of the composition is an amount effective to dissolve, remove, and clean soldering flux.

It is another important aspect of the present invention that the TPGBE forms an azeotrope with water at 1.0%. This results in a minimal loss of solvent due to evaporation during the cleaning process, even where ventilation creates a pressure differential over the liquid surface which ordinarily causes solvent evaporation.

The invention contemplates a concentrated liquid cleaning composition which comprises TPGBE and a sufficient amount of an alkali to result in a pH at least about 7.5. The composition may be diluted with water to a concentration of 0.1 to 99.1 wt %. In a preferred embodiment, the composition can be diluted with water to a concentration of about 30 to about 99.99%.

In another embodiment, the composition may contain at least one additional secondary solvent that imparts different solubility parameters for different flux types. The secondary solvent or solvents may be in the composition in a total amount of up to90%, preferably up to 70%. The secondary solvent or solvents can be one or more of the following:

a glycol ether of the formula R₁â€”Oâ€”(C_xH_2xO)_nâ€”H, wherein:

- R₁is an alkyl group having 1 to 6 carbon atoms,
- n is integer from 1 to 4, and
- x is integer from 1 to 4 an alcohol of the formula R₂â€”OH, wherein:
- R2 is an alkyl group having 1 to 8 carbon atoms, a tetrahydrofurfuryl group, a
- benzyl group or hydrogen

an N-alkyl pyrollidone of the formula R₃Npyrr, wherein:

- Npyrr represents a pyrollidone ring
- R₃is an alkyl group having 1 to 8 carbon atoms

dibasic esters of the formula R₄â€”Oâ€”OCâ€”(CH₂)_kâ€”COâ€”Oâ€”R₄, wherein:

- R4 is Methyl, ethyl, or isobutyl
- k is an integer from 2 to 4

The secondary solvent is selected from the group consisting of dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, tripropylene glycol methyl ether, diethylene glycol butyl ether, methoxy methyl butanol, tetrahydrofurfuryl alcohol, benzyl alcohol, N-methyl pyrollidone, N-ethyl pyrollidone, N-propyl pyrollidone, N-octyl pyrollidone, dimethyl adipate, dimethyl succinate, dimethyl glutarate, diisobutyl adipate, diisobutyl succinate and diisobutyl glutarate.

The alkali is one or more of an amine, imide, inorganic hydroxide, silicate, or phosphate and is present in an amount of 0.01 to 70 wt %.

The preferred amine is an alkanolamine. The alkanolamine is selected from the group consisting of monoethanolamines, diethanolamines, triethanolamines, aminomethylpropanol, methylethanolamine, methyldiethanolamine, dimethylethanolamine, diglycolamine, methylethanolamine, monomethylethylethanolamine, dimethylaminopropylamine, aminopropyldiethanolamine, isopropylhydroxylamine, dimethylamino methyl propanol and combinations thereof

The inorganic salts are selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium silicate, sodium metasilicate, potassium silicate, sodium phosphate, potassium phosphate and combinations thereof

In an embodiment, one or more surface active agents are added to improve cleaning, or processing. It is preferred that the surface active agent is a nonionic surfactant. A typical nonionic surfactant is Tritoâ„¢ X-100 which is produced from octylphenol polymerized with ethylene oxide. The nonionic surfactant is added in an amount less than 10% and preferably less than 3% of the weight of the composition.

One or more corrosion inhibitors may be added to the composition to improve compatibility. Preferred corrosion inhibitors are selected from the group consisting of benzotriazoles, derivatives of benzotriazoles, water soluble silicates, and inorganic salts of phosphoric acid. The preferred corrosion inhibitor is an alkali salt of a metasilicate.

One or more buffering agents may be added to provide pH control. Preferred buffering agents are selected from the group consisting of mono, di and tri-carboxylic acids. The preferred buffering agent is one or more of 2-hydroxypropane-1,2,3-tricarboxylic acid, C₃to C₂₀mono carboxylic acids, hydrogen alkali salts of phosphoric acid, and boric acid. The buffering agent is added an a concentration effective to keep the pH at at least 7.5 and, preferably, above 7.5.

At least one chelating or sequestering agent may be added to the composition. Preferred chelation or sequestering agents are ethylenediaminetetraacetic acid (EDTA) or its salts and ethylenediamine-N,N=-disuccinic acid or its salts.

In another aspect of the invention, a method is provided which comprises a single stage wash with the composition in a manner known to those skilled in the art of cleaning. The wash is followed by a rinse stage to remove the composition from the part followed by a dry stage. Wash and rinse can be accomplished by means of spraying, spray under immersion, agitation, ultrasonics, dipping, tumbling, wiping or immersion. The wash may be conducted at ambient temperature or as low as 2 degrees C. below the flash point of the composition

Some embodiments are summarized in the following table:

TABLEIn 100% Required Concentrated% Composition RequiredCompositionin WaterA) Solvent system content inâ€ƒâ€‰30-99.99%concentrated liquid wt %Tripropylene Glycol Butyl â€ƒâ€‚â€‰9-100%Ether (TPGBE) as wt % of total solvent systemB) Alkaline Agent content inâ€ƒ.01-70%concentrated liquid wt %(A + B) Solvent System plus30.01-100.00%0.1 to 100%Alkaline agent in (neat)Concentrate wt %Optional Items in â€‚0.00-69.99%Concentrate wt %Optional Solvent as wt % ofâ€‚0.00-91%solvent systemOptional Surface Active AgentEffective Amt.Optional Non Ionic Surfactants<3%<3%Optional Corrosion InhibitorsEffective Amt.Optional Buffering AgentsEffective Amt.Optional Chelators SequestrantsEffective Amt.Required pH>7.5>7.5

Preferred embodiments of the composition and method of the present invention are described in detail in the following examples which should not be construed to limit the scope of the present invention. Unless stated otherwise, all parts and percentages are given by weight.

EXAMPLE 1

Solutions of TPGBE in water were made at 0.5%, 1.0%, and 3.0% TPGBE by weight. These solutions were distilled using a Snyder column and a condenser capable of returning the distillate to the boiling flask, through the Snyder column, or to a sampling port. The following samples of the distillate were taken: first distillate to condense, distillate after 15 minutes of reflux, and distillate after 30 minutes of reflux. The concentration of TPGBE was monitored at each point in time with two independent methods. The concentration of TPGBE in the distillate for all initial TPGBE concentrations at all points in time was 1.0% âˆ€0.2% (95% confidence interval) by weight. This indicates that TPGBE forms an azeotrope at 1.0%.

EXAMPLE 2

A concentrated cleaning agent was formulated with a composition of 82.0% TPGBE, 15.90% 2-aminoethanol, 0.1% citric acid, 2.2% Triton X-100, 0.2% disodium EDTA, 2.4% buffering agent consisting of C₃to C₂₀mono carboxylic acids and/or their alkali metal salts, with water comprising the balance. The pH of the neat cleaning agent was 11.5.

EXAMPLE 3

The concentrated cleaning agent described in Example 2 was diluted with water creating a solution that consisted of 5.0% of the concentrated cleaning agent by weight, and 95.0% water, by weight. This diluted composition was placed in an inline spray in air cleaning machine. Electronic assemblies were constructed with solder fluxes of the water soluble (WS), rosin mildly activated (RMA), rosin activated (RA) fluxes, and no clean (NC) types. These electronic assemblies were then cleaned in the diluted cleaning agent using a spray in air process for approximately four minutes at about 65.6 E C (150 E F). After cleaning, the electronic assemblies were evaluated for percentage of flux removed using visual inspection. Most electronic assemblies had complete (100%) flux removal.

EXAMPLE 4

The concentrated cleaning agent described in Example 2 was diluted to 8% by weight with water. Circuit assemblies of the same types described in Example 3 were cleaned in the exact same manner as in Example 3 but at temperatures of about 49 E C (120 E F), about 54.4E C (130 E F), 60E C. (140 E F), and about 65.6 E C (150 E F). The cleaning performance of the diluted cleaning agent was excellent at all temperatures.

EXAMPLE 5

A concentrated cleaning agent was formulated with a composition of 38.1% TPGBE, 37.9% dipropylene glycol n-propyl ether (DPnP), 14.6% 2-aminoethanol, 0.1% citric acid, 1.8% Triton X-100, 0.4% disodium EDTA, 2.0% buffering agent consisting of C₃to C₂₀mono carboxylic acids and/or their alkali metal salts, with water comprising the balance. The pH of the neat cleaning agent was 11.4.

EXAMPLE 6

The concentrated cleaning agent described in Example 5 was diluted to 8% by weight with water. Circuit assemblies of the same types described in Example 4 were cleaned in the exact same manner as in Example 4. The cleaning performance of the diluted cleaning agent was excellent at all temperatures.

EXAMPLE 7

A concentrated cleaning agent was formulated with a composition of 9.0% TPGBE, 64.5% dipropylene glycol n-propyl ether (DPnP), 15.9% 2-aminoethanol, 0.2% citric acid, 2.2% Triton 100, 0.4% disodium EDTA, 2.5% buffering agent consisting of C₃to C₂₀mono carboxylic acids and/or their alkali metal salts, with water comprising the balance. The pH of the neat cleaning agent was 11.3.

EXAMPLE 8

The concentrated cleaning agent described in Example 7 was diluted to 8% by weight with water. Circuit assemblies of the same types described in Example 4 were cleaned in the exact same manner as in Example 4. The cleaning performance of the diluted cleaning agent was excellent at all temperatures. The cleaning performance of the diluted cleaning agent was excellent at all temperatures.

EXAMPLE 9

A concentrated cleaning agent was formulated with a composition of 64.8% TPGBE, 9.0% dipropylene glycol n-propyl ether (DPnP), 16.0% 2-aminoethanol, 0.1% citric acid, 2.1% Triton X-100, 0.2% disodium EDTA, 2.4% buffering agent consisting of C₃to C₂₀mono carboxylic acids and/or their alkali metal salts, with water comprising the balance. The pH of the neat cleaning agent was 11.4.

EXAMPLE 10

The concentrated cleaning agent described in Example 9 was diluted to 8% by weight with water. Circuit assemblies of the same types described in Example 4 were cleaned in the exact same manner as in Example 4. The cleaning performance of the diluted cleaning agent was excellent at all temperatures. The cleaning performance of the diluted cleaning agent was excellent at all temperatures.

Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of this invention. Unless stated otherwise, all parts and percentages in the following claims are given by weight.