KR20050019087A - Solder paste flux system - Google Patents

Abstract

The present invention relates to a solder solvent and a solder paste comprising methyl succinic acid as an activating component and an imidazole compound as an accelerating component. The imidazole compound is selected from 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole and mixtures thereof. The present invention also relates to a method for producing the solder solvent described above and a soldering method using the solder solvent paste. Moreover, this invention relates to the electronic component assembly joined using the solder solvent paste.

Description

Solder Paste Solvent System {SOLDER PASTE FLUX SYSTEM}

The present invention relates to a solvent processing method of a flux system and an integrated circuit (IC) device for activation. More specifically, the present invention relates to a method comprising using methylsuccinic acid as activator and imidazole compound as accelerator for solvent treatment during the soldering process.

Solder paste is a mixture of a solvent composition and a powdered solder metal alloy widely used in the electronics industry. At room temperature, the solder paste exhibits sufficient flexibility to make it suitable for all practical forms. At the same time, it exhibits sufficient "viscosity" to exhibit a tendency to adhere to all surfaces in contact. This property makes the solder paste useful for both side mount soldering and solder bump formation in electronic components such as ball grid device packages or BGA's mounting plates.

In general, surface mount soldering processes involve placing electrical contacts, electronic solders, small amounts of solder paste, and solder wettable pads in close proximity on a printed circuit board. They are then heated until the solder reflows, thereby forming an electrical connection between the solder wettable pad and the electrical contacts of the electronic component. Once the solder reflows, it creates electrical and magnetic connections between the electronic component and the printed circuit board. This process has a number of advantages over other interconnect methods. First, multiple components can be interconnected simultaneously. Second, these processes are highly repeatable, relatively inexpensive, and easily applicable to mass production.

Surface mount soldering processes are typically initiated by screening or screen printing solder paste onto the solder wettable pads of a printed circuit board. Once the solder paste is placed on the solder wettable pad, the electronic component to be soldered is aligned on the printed circuit board by the electrical contacts of the electronic component in contact with the solder paste and fixed in a specific position. Solder paste keeps the electronic components in place during the refluidization process.

During the refluidization process, the solder paste allows 1) the solvent to remove oxides from all surfaces associated with the soldering process (eg, substrate, solder pads, solder bumps and solder alloy powders), and 2) the solder powder is sufficiently melted Heat to a temperature that allows it to coalesce into a single liquid. The reflowed solder is contacted with the solder pads and / or substrate and then cooled once solidified to form a complete and electrically conductive solder joint.

To form a fully fused, strong solder joint, the solder must appropriately “wet” the solder pads and / or substrate. Wetting is highly dependent on the metallurgical reaction between the solder and the surface to be soldered and the effectiveness of the solder paste solvent. Wetting is more efficient when the molten solder is brought into contact with a clean, oxide free surface. In other words, the temperature at which the solder powder melts, and the duration that the solder paste is maintained at temperatures higher than the temperature at which the solvent reaction occurs are important factors to ensure good wetting and strong solder joints. However, if the solvent fails to adequately remove the oxide from the metal to be joined during the refluidization process, the "solder bowling" and incomplete fusion occur as the oxide delays or interferes with the solder bonding. The term "solder bowling" refers to the undesirable tendency of solder paste to form small spheres of solder when heated during refluidization, instead of forming a single solder fillet. In addition, the junction will be incompletely fused, fragile and "voiding". While not wishing to be bound by any particular theory, it is believed that the mechanism behind current pore formation is the influx of excess solder solvent or its vapors into the solder alloy. The composition or reflow profile of the solvent prevents the solvent and / or its vapors from draining during the refluidization cycle, which causes internal voids in the solder joint upon cooling.

In summary, the solvent composition provides some of the features required for this soldering process. For example, solder paste solvents have suitable viscosity, rheology, adhesion, and slump to suspend, print, and secure electronic components prior to curing (ie, before and during refluidization). Should have a degree. Solvents must also remove oxides from the metal surface at appropriate temperatures and be capable of preventing oxidation for a sufficient duration during and after the refluidization process. In addition, the solvent and / or its residues preferably do not corrode the solder metal before, during, or after the soldering process.

Existing solder paste solvent compositions (eg, those suitable for Sn-Pb solder) are effective under standard refluidization conditions (eg, from about 200 ° C. to about 220 ° C. for about 30 to about 90 seconds), but It is not appropriate if oxidation is promoted or prolonged during fluidization. These harsh conditions typically include high peak temperatures (eg, above about 230 ° C.), slow rate of temperature increase (eg, from about 1 ° C./second to about 2 ° C./second), prolonged soaking (eg, about Results in reflowing the solder paste in an oxidizing atmosphere using < 160 > These harsh refluidization conditions may occur when soldering with any solder composition, but typically lead-free solder alloys or high Pb / Sn ratios (eg Pb> 37 wt%) of solder content Is essential when reflowing, both of which exhibit a significantly higher liquefaction temperature than the liquefaction temperature of the ubiquitous Sn ₆₃ Pb ₃₇ alloy (about 183 ° C.). Another situation requiring improved solvent protection is the refluidization of small solder deposits (eg, deposits less than about 300 μm wide) because the protective layer of liquid solvent is thin and easily permeable by oxygen. As such, there is a continuing need for solder paste solvents that have improved oxide removal activity (ie, solvent treatment activity) and increased resistance to oxidation at high temperatures for long periods of time.

Summary of the Invention

An object of the present invention is a solder paste solvent having a viscosity, rheological state, adhesion and slumping degree suitable for suspending, printing, and fixing the electronic component prior to curing (ie, before and during refluidization) of the metal solder powder. The provision of; Providing a solder paste solvent that removes oxides from the metal surface at elevated temperatures essential for lead-free solder alloys; Providing a solder paste solvent that prevents oxidation for extended solder durations essential for lead free soldering; Providing a solder solvent paste that does not corrode the solder metal before, during, or after the soldering process; And provision of a solder solvent paste that protects small solder deposits (eg, deposits less than about 300 μm in width) during the refluidization process.

Therefore, the present invention is briefly described as a basic component, a solvent component, an active component containing methyl succinic acid, 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole and mixtures thereof. It relates to a solder solvent composition comprising a facilitation component containing an imidazole compound selected from the group consisting of.

The present invention also relates to about 13.0 to about 23.0 wt% of hydrogenated resin, about 13.0 to about 23.0 wt% of hydrogenated rubber tree rosin, about 14.0 to about 30.0 wt% of glycol ether, and about 6.0 to about 12.0 wt% of hydroxy group terminated poly Butadiene, about 3.0 to about 15.0 wt% of petroleum distillate, about 4.0 to about 17.0 wt% of methyl succinic acid, about 3.0 to about 10.5 wt% of 2-ethylimidazole, optionally up to about 13 wt% of urine It relates to a solder solvent composition comprising a modifier, optionally up to about 2.0 wt% phosphine derivatives, and optionally up to about 2.5 wt% triazole derivatives.

In addition, the present invention relates to a solder paste containing metal solder powder dispersed in a solder solvent composition. The solder solvent composition is in a group consisting of a base component, a solvent component, an active component containing methyl succinic acid, 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole, and mixtures thereof Promotion components containing the selected imidazole compound. Optionally, the solder solvent composition includes a rheological component and a corrosion inhibitor component.

In addition, the present invention relates to a method of joining two solderable surfaces. The method includes applying a deposit of a solder paste on at least one solderable surface, the solder paste comprising a metal solder powder and a solder solvent composition, wherein the solder solvent composition comprises a base component, a solvent component, a methyl succinic acid. And an promoting component containing an imidazole compound selected from the group consisting of 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole and mixtures thereof. Include. Both solderable surfaces are wetted by melting the solder paste by applying heat to the at least one solderable surface to reflow the solder paste, and then joining the two solderable surfaces by cooling the molten solder to solidify the solder.

The invention also relates to an electronic component assembly comprising an electronic component having a plurality of solder wettable pads, a substrate having an electrical contact corresponding to the solder wettable pad of the electronic component, and a solder paste between the solder wettable pad and the electrical contact. Solder pastes are metal solder powders and base components, solvent components, active ingredients containing methyl succinic acid, 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole and mixtures thereof It includes a solder solvent composition containing a facilitation component containing an imidazole compound selected from the group consisting of. The solder solvent composition optionally includes a rheological component and a corrosion inhibitor component.

The present invention further relates to a method for producing a solder solvent composition comprising the step of mixing an active ingredient containing methyl succinic acid and an accelerating ingredient containing 2-ethylimidazole.

The foregoing and other features and advantages of the present invention will become apparent from the following detailed description.

The present invention relates to a solder solvent containing methyl succinic acid (also referred to as pyrotartaric acid). The IUPAC name for methylsuccinic acid is 2-methyl-1,4-butanedioic acid. The chemical formula of methylsuccinic acid is HO ₂ CCH (CH ₃ ) CH ₂ CO ₂ H. Surprisingly, the inclusion of methyl succinic acid in the solder solvent provides several advantages, such as increased solvent treatment activity, increased oxidation resistance, and improved degradation resistance even with increased temperature and duration.

Methylsuccinic acid can be contained in all process types of soldering process solvents. However, it is particularly useful when it is part of a solvent composition that is mixed with a powdered solder alloy to produce a solder paste. Therefore, the following discussion relates to the inclusion of methylsuccinic acid in solder paste applications. The viscous solvent composition of this invention contains a base component, a solvent component, and an activator component. Optionally, the solvent composition may comprise an accelerator component, a rheological component, and / or a corrosion inhibitor component.

Basic ingredients

Soldering solvents of the present invention are typically classified into oil soluble types wherein the base component is a thermoplastic or thermoset resin. Preferably, the base component includes thermoplastic resins such as rosin, modified rosin, rosin deformable resins and synthetic resins. Examples of rosin, modified rosin, and rosin modifying resins include wood rosin, rubber rosin, tall oil rosin, disproportionated rosin, hydrogenated rosin, polymeric rosin, hydrogenated resin, hydrogenated rubber wood rosin and Poly BD R45HTLO resin (Elf Atochem, Philadelphia, PA) is included. Examples of synthetic resins include carboxyl group-containing resins such as polyester resins, acrylic resins and styrenemaleic acid resins, epoxy resins, resol or novolac phenol resins, and KE 604 (Arakawa Chemicals, Japan) and Foral AX (Hercules Inc., Wilmington). , DE). The base component may include one or more of the aforementioned thermoplastic resins. The base component is preferably included from about 5 to about 95 wt%, more preferably from about 20 to about 50 wt% of the solvent. The base component prevents solder oxidation at elevated temperatures, provides a protective barrier against oxygen, and also activates the solder surface by removing oxygen from the surface and the solder.

Solvent components

The solvent of this invention contains a solvent component. The purpose of the solvent is to dissolve the base component and other solvent components, disperse the insoluble solvent component, and coat the solder metal alloy powder. If the solvent is volatile it will also promote fast fixation after the solvent has been applied to the substrate. During the refluidization process, the solvent evaporates leaving other reacted solvent components and / or unreacted solvent components.

Examples of the solvent include ketones such as acetone and methyl ethyl ketone; Alcohols such as methanol, ethanol, isopropyl alcohol, methylcellosolve, ethylcellosolve, 1-methoxy-2-propanol, carbitol and butylcarbitol; Esters of such alcohols; Aromatic solvents such as toluene and xylene; Glycol ethers such as tripropylene glycol n-butyl ether and tetraethylene glycol dimethyl ether; And terpenes such as pine oil and terpineol; Petroleum distillates and hydroxyl group terminated polybutadiene. The solvent mentioned above can be used independently or in combination.

The solvent component is preferably included at about 5 to about 95 wt%, more preferably at about 20 to about 70 wt% of the solvent. If the concentration of the solvent component is less than about 20 wt% of the solvent composition, the viscosity of the solvent is typically high enough to prevent printing and negatively affect the coatability of the solder paste. On the other hand, if the concentration of the solvent component exceeds about 70 wt%, the active fraction of the solvent (e.g., the base component and the active component) tends to be deficient, resulting in incomplete solder alloys during insufficient solvent treatment and refluidization. May result in fusion.

Active ingredient

The solvent of this invention contains the active ingredient containing methyl succinic acid. Preferably the activating component consists mainly of methylsuccinic acid. The active ingredient is preferably comprised from about 1 to about 30 wt%, more preferably from about 2 to about 20 wt% of the solvent. Methylsuccinic acid is available from a number of suppliers including SGA Specialties Group, LLC Annandale, NJ and 5-Star Group, Lewingston, PA.

Although considered unnecessary, the activating component may typically contain additional compounds including amine halide salts, and amine organic acid salts, phosphonic acids, phosphate esters, amino acids, alkanolamines, organic acids, and combinations thereof. If present, the additional compounds preferably include organic acids, and more preferably include carboxylic acids (eg, monocarboxylic acids, dicarboxylic acids and polycarboxylic acids) which may contain hydroxy groups and / or double bonds. Examples of monocarboxylic acids include aliphatic monocarboxylic acids such as caproic acid, enanthic acid, capric acid, pelagonic acid, lauric acid, palmitic acid and stearic acid. Monocarboxylic acids also include aromatic monocarboxylic acids such as benzoic acid, salicylic acid, aniseic acid, sulfanilic acid. Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid and itaconic acid, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and naphthalenedicarboxylic acid. Examples of tricarboxylic acids include tricarballylic acid, aconic acid and citric acid. Carboxylic acids are considered acceptable because they are weakly ionic compared to halide containing activators such as amine hydrochlorides (eg, amine hydrochloride and amine hydrobromide) commonly used in the electronics industry. In addition, since there are no halides, they do not cause corrosion of the aforementioned solder metals that occur when halides are present. If included, dicarboxylic acids are preferred because they provide an acceptable combination of soldering performance, minimal ionic impurity residue, and high surface insulation resistance.

The choice of base and active component materials is based, in part, on the melting temperature of the solder alloy used. The reaction initiation temperature of the base component and the activating component is preferably lower than the melting point of the solder alloy. For example, when the refluidization temperature of the Sn ₆₃ Pb ₃₇ solder alloy is about 183 ° C., an activating component having a melting point of about 130 ° C. to about 180 ° C. may be considered. An activating component with a lower melting temperature will react with the thermoplastic resin too early during the refluidization process, and an activating component with a higher melting point will result in incompletely fused solder joints because it does not bring the solder into a proper wet state.

Promotion ingredients

The solvent of the present invention includes a facilitating component that promotes the reaction between methylsuccinic acid (and other activating components) and the base component. In other words, the facilitating component reduces the temperature at which the solvent treatment chemical reaction (i.e., the interaction between the activating component and the base component) is initiated. The facilitating component preferably contains imidazole compounds or derivatives, including, for example, 2-methyl-4-ethylimidazole, 2-methylimidazole and 2-ethylimidazole. More preferably, the facilitating component consists mainly of 2-ethylimidazole. The facilitation component is preferably comprised from about 0.5 to about 15 wt%, more preferably from about 3 to about 11 wt% of the solvent. Imidazole compounds such as 2-ethylimidazole are commercially available from various suppliers, including BASF.

Optionally, the facilitating component may contain other compounds such as ammonium salts and tertiary amines. Examples of ammonium salts include triethylbenzylammonium chloride, trimethylbenzylammonium chloride and tetramethylammonium chloride. Examples of tertiary amines include benzyldimethylamine, tributylamine and tris (dimethylamino) methylphenol.

The relative amounts of methylsuccinic acid and 2-ethylimidazole are preferably selected to produce an excessively acidic solvent composition. The weight ratio of methylsuccinic acid to 2-ethylimidazole is preferably from about 6.7 to about 9.3, and more preferably from about 8 to about 11.

Rheological components

In order to improve the printability of the solder paste, the solvent preferably contains a rheological component. Typically, in rheology of solder paste, it is in the form of a gel or semisolid at rest, but flows like a liquid when a shear force is applied. This allows the paste to flow through the template when pressed using a compactor to maintain the pattern of the template even after removing the template from the substrate surface. This feature is preferably achieved by using thixotropic agents in the rheological components. Examples of thixotropic agents include hydrogenated castor oil, castor oil-based thixotropic agents such as THIXATROL ST available from Reox, Inc., and RHEOCIN, polyamide and polyethylene wax available from Sud-Chemie Rheologicals. The rheological component may comprise one or more of the foregoing materials, wherein the concentration of the rheological component is preferably from about 0.5 to about 15 wt% of the solvent, and more preferably from about 1 to about 11 wt% of the solvent. to be.

Corrosion inhibitor components

The solvents of the present invention may also contain a corrosion inhibitor component that reduces or prevents corrosion of the reflowed solder joints during use and / or subsequent thermal cycles associated with the manufacturing process. Examples of corrosion inhibitor components include phosphine derivatives such as triphenylphosphine and triazole derivatives such as hydroxybenzotriazole. The corrosion inhibitor component may comprise one or more of the above materials, preferably from about 0.1 to about 5 wt% of the solvent, and more preferably from about 0.5 to about 3 wt% of the solvent.

One embodiment of the solder solvent according to the present invention is shown in the table below.

ingredient type wt% Hydrogenated resin Basic ingredients 13.0-23.0 Hydrogenated Rubber Wood Rosin Basic ingredients 13.0-23.0 Glycol ether menstruum 14.0-30.0 Hydroxy Group Terminated Polybutadiene menstruum 6.0-12.0 Petroleum distillate menstruum 3.0-15.0 Methyl succinic acid Activator 4.0-17.0 2-ethylimidazole accelerant 3.0-10.5 Thixotropic agent Rheological Formulations 0.0-13.0 Phosphine derivatives Corrosion inhibitor 0.0-2.0 Triazole derivatives Corrosion inhibitor 0.0-2.5

Solvent manufacturing

The solvent composition of this invention can be manufactured by arbitrary suitable methods. Typically, the various components (ie, solvent component, base component, activating component, facilitating component, rheological component, and corrosion inhibitor component) are mixed together and then sufficient temperature (eg, until a uniform and uniform solution is obtained). For example, about 80 ° C. to about 150 ° C., and preferably about 100 ° C. to about 130 ° C., for a sufficient duration (eg, about 60 to about 180 minutes).

Although not essential, it is preferred that the activating and / or facilitating components be added to the solvent composition in a manner that limits and / or excludes chemical reactions between these components and / or chemical reactions with other components (particularly the base component). For example, although not wishing to be bound by a particular theory, it is presently believed that methylsuccinic acid and 2-ethylimidazole react to form methylsuccinic acid 2-ethylimidazole, which is believed to greatly enhance solvent activity. Solvent activity during refluidization was observed to be maximal when minimizing this reaction prior to the refluidization process (eg, during solvent preparation and during storage). That is, preferably at least one of the components is added to the solvent at the finishing stage of the solvent preparation process. More preferably, both methylsuccinic acid and 2-ethylimidazole are added at the finishing stage of the production process. In particular, when the solvent product is cooled to ambient temperature, methylsuccinic acid and 2-ethylimidazole are preferably added after the temperature has decreased to about 40 ° C or less. In addition to increasing solvent activity, minimizing the reaction prior to refluidization also increased the stability and shelf life of the paste.

Solder alloy

The solvent of the present invention can be used in any electrical contact solder alloy, such as conventional leaded solders (eg, Sn ₆₃ Pb ₃₇ and Sn ₆₂ Pb ₃₆ Ag ₂ ). However, this is generally referred to as a lead-free solder alloy and is particularly useful for solvent treatment of substantially lead free solder alloys, typically containing less than 0.3 wt% lead. Lead-free solder alloys tend to have higher liquefaction temperatures and / or longer reflow durations than leaded solder alloys. Examples of lead-free solder alloys include Au ₈₀ Sn ₂₀ , Sn _96.2 Ag _2.5 Cu _0.8 Sb _0.5 , Sn ₆₅ Ag ₂₅ Sb ₁₀ , Sn _96.5 Ag _3.5 , Sn _95.5 Ag _3.8 Cu _0.7 , Sn _96.5 Ag ₃ Cu _0.5 , Sn _95.5 Ag ₄ Cu _0.5 , Sn _93.6 Ag _4.7 Cu _1.7 , Sn ₄₂ Bi ₅₈ , Sn ₉₀ Bi _9.5 Cu _0.5 , Sn _99.3 Cu _0.7 , Sn ₉₉ Cu ₁ , Sn ₉₇ Cu ₃ , Sn _87.1 In _10.5 Ag ₂ Sb _0.4 , Sn _77.2 In ₂₀ Ag _2.8 , Sn _63.6 In _8.8 Zn _27.6 , Sn ₉₇ Sb ₃ and Sn ₉₅ Sb ₅ . The preferred methyl succinic acid containing solvent composition described above is particularly suitable for printing and solvent treatment of Sn _95.5 Ag ₄ Cu _0.5 and Sn _96.5 Ag ₃ Cu _0.5 alloys.

In the manufacture of solder pastes, the solder alloy is powder. Preferably, the alloy powder particles have a size of about 100 to about 400 meshes according to the Tyler Standard Screen Scale (ie, the particles pass through a screen having a body of about 150 μm but have a body of about 38 μm). Screen will not pass). Solder powders may be prepared by any suitable technique including inert gas atomization and centrifugal spraying.

Solder paste

The solder paste is preferably prepared by mixing the cooled solvent composition and the metal alloy powder in a conventional manner. The method of mixing is not critical but should be such that a uniform dispersion of the metal and the solvent is obtained. For example, blenders and rotary blade mixers can be used. The proportion of solder powder and solvent is chosen to provide a mixture having a concentration suitable for printing. Generally, the weight ratio of solder powder to solvent is in the range of about 80:20 to about 95: 5 and preferably about 85:15 to about 90:10.

Often it may be desirable to blend the solder paste to have a particular viscosity. Prior to testing the viscosity of the paste, it is desirable to leave for several hours to obtain a "rest" viscosity. If desired, the viscosity of the paste can be modified before and / or during use. For example, when the viscosity is too high, an additional solvent may be added. On the contrary, when the viscosity is too low, an additional solder alloy powder may be added. Preferably, the paste is then left to stand again before the viscosity is measured again.

Print and Reflux

As mentioned above, the solder paste is applied to selected areas on the printed circuit board through light copying and / or screen printing. The electronic device is bonded to the circuit board by mounting the electronic device on the applied solder paste and then heating the assembly in a furnace to melt or reflow the solder alloy. The surface peak temperature of the circuit board upon heating is preferably 250 ° C. or lower, most preferably about 50 ° C. above the liquefaction temperature of the solder alloy present in the paste.

It is believed that methylsuccinic acid and 2-ethylimidazole react during the refluidation to form a salt, namely methylsuccinic acid 2-ethylimidazole, which removes oxygen from the surface of the metal solder alloy and the substrate by activating the thermoplastic resin. And encapsulate the molten metal to form a liquid that prevents oxygen from reaching the solder joint during and after the refluidization process to protect the bonded metal from oxygen in the atmosphere. Preferably, at least about 50% of the available methylsuccinic acid and 2-ethylimidazole react to form an activator salt. More preferably, at least about 70% of the available methylsuccinic acid and 2-ethylimidazole react to form an activator salt. After refluidization, the preferred solvent composition makes it possible to test solder joints using circuit pin tests by leaving soft residues.

The solvent treatment activity of the methyl succinic acid-containing lead-free solder paste of the present invention was compared with the activity of the lead-free solder paste containing no methyl succinic acid using the solder ball test. Solder ball testing involves placing a solder paste deposit of about 6.5 mm diameter on an alumina plate and heating it to about 225-250 ° C. in an oven. Since the alumina was not wetted with the solder alloy, a suitably solvented solder paste deposit would form a gloss approximately 2 mm diameter circular ball upon heating. Poor performance of the solvent results in oxidized metal powder on the surface of the alumina surrounding the larger fused balls.

Specifically, the test solder paste contained about 87 to 89 wt% Sn _95.5 Ag ₄ Cu _0.5 alloy powder and about 11 to 13 wt% solvent prepared according to the above solvent composition table. The same comparative solder paste was also prepared except that phenylsuccinic acid was used instead of methylsuccinic acid.

Several refluidization tests were performed on test and comparative solder pastes. For example, the deposit was reflowed by heating to a temperature of about 230 ° C. at a constant rate of temperature increase of about 0.7 ° C./sec and then cooled (oven tolerance ± 5 ° C.). The deposit was held for about 60 seconds above about 217 ° C. The eutectic temperature of the Sn _95.5 Ag ₄ Cu _0.5 alloy is about 217 ° C. At a temperature slightly above the eutectic temperature (<about 5 ° C.) the alloy became paste form and reached a temperature slightly above the liquefaction temperature (ie the alloy was completely melted). Visual inspection of the paste deposits showed that the methylsuccinic acid containing paste was fully fused but the comparative paste was not.

In another test, the paste was only heated to about 229 ° C., only about 12 ° C. above the eutectic temperature. Even at these low temperatures, the methylsuccinic acid containing deposits formed fully fused solder balls.

For further comparison, in a typical mass production refluidization process for Sn _95.5 Ag ₄ Cu _0.5 alloy, the soldered surface is heated to a temperature of about 237 ° C. to about 245 ° C. which is likely to increase the oxidation of the solder to the atmosphere. Involved the process. Commercial heating rates are about 1 to 2 ° C./sec, less severe than 0.5 to 0.7 ° C./sec used during the test. In addition, the refluidization process often involves dipping to maintain the printed substrate at a temperature that gradually increases (eg, 60 ° C. and / or 180 ° C. for about 10 to 30 seconds, wherein the time above the liquefaction temperature is about 30-40 seconds to about 100 seconds. Increasing the duration of the refluidization process requires a solvent composition that is more resistant to the penetration of oxygen into the atmosphere through the liquid solvent. Solder pastes containing methylsuccinic acid reflowed even under these harsh oxidation conditions to form fully fused joints.

It is obvious that the above description is intended to be illustrative rather than restrictive. Many embodiments will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present invention should not be determined only with reference to the above description, but should also be determined with reference to the claims and the full scope of equivalents to which such claims are entitled.

Claims (36)

Basic ingredients; Solvent component; Active ingredients containing methylsuccinic acid; And a solder flux composition comprising an accelerating component containing an imidazole compound or derivative. The solder solvent composition of claim 1, wherein the facilitating component is selected from the group consisting of 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole, and mixtures thereof. . The solder solvent composition according to claim 1, wherein the activating component is mainly composed of methyl succinic acid, and the promoting component is mainly composed of 2-ethylimidazole. The method of claim 1 wherein the base component is in the range of about 5 to about 95 wt% of the solder solvent composition, the solvent component is in the range of about 5 to about 95 wt% of the solder solvent composition, and the activating component is about And a facilitating component in a range from about 0.5 to about 15 wt% of the solder solvent composition. The method of claim 1 wherein the base component is in the range of about 20 to about 50 wt% of the solder solvent composition, the solvent component is in the range of about 20 to about 70 wt% of the solder solvent composition, and the activating component is about about the solder solvent composition. Wherein the facilitating component is in the range of about 3 to about 11 wt% of the solder solvent composition. The base component is wood rosin, rubber rosin, tall oil rosin, disproportionated rosin, hydrogenated rosin, polymerized rosin, hydrogenated resin, hydrogenated rubber tree rosin, carboxyl group-containing resin, polyester resin, acrylic resin, styrene male A solder solvent composition comprising a thermoplastic resin selected from the group consisting of acid resins, epoxy resins, phenol resins, and mixtures thereof. The solder solvent composition according to claim 6, wherein the basic component is mainly composed of a hydrogenated resin and a hydrogenated rubber tree rosin. The solder solvent composition of claim 1 wherein the solvent component is selected from the group consisting of ketones, alcohols, esters of alcohols, aromatic solvents, glycol ethers, terpenes, petroleum distillates, hydroxy-terminated polybutadienes and mixtures thereof. . The solder solvent composition of claim 1 comprising a rheological component selected from the group consisting of hydrogenated castor oil, castor oil based thixotropic agents, polyamides, polyethylene waxes, and mixtures thereof. 10. The solder solvent composition of claim 9, wherein the rheological component comprises from about 0.5 to about 15 wt% of the solder solvent composition. 10. The solder solvent composition of claim 9, wherein the rheological component comprises about 1 to about 11 wt% of the solder solvent composition. The solder solvent composition of claim 1 comprising a corrosion inhibitor component selected from the group consisting of phosphine derivatives, triazole derivatives and mixtures thereof. 13. The solder solvent composition of claim 12, wherein the corrosion inhibitor component comprises from about 0.1 to about 5 wt% of the solder solvent composition. 13. The solder solvent composition of claim 12, wherein the corrosion inhibitor component comprises from about 0.5 to about 3 wt% of the solder solvent composition. About 13.0 to about 23.0 wt% hydrogenated resin, about 13.0 to about 23.0 wt% hydrogenated rubber tree rosin, about 14.0 to about 30.0 wt% glycol ether, about 6.0 to about 12.0 wt% hydroxy-terminated polybutadiene, about 3.0 To about 15.0 wt% petroleum distillate, about 4.0 to about 17.0 wt% methylsuccinic acid, about 3.0 to about 10.5 wt% 2-ethylimidazole, optionally up to about 13 wt% thixotropic agent, optionally Is about 2.0 wt% or less of a phosphine derivative, and optionally about 2.5 wt% or less of a triazole derivative. Basic ingredients; Solvent component; Active ingredients containing methylsuccinic acid; Facilitating components containing imidazole compounds or derivatives; Optionally a rheological component; And a solder paste comprising a metal solder powder optionally dispersed in a solder solvent composition comprising a corrosion inhibitor component. The solder paste of claim 16, wherein the weight ratio of the metal solder powder to the solder solvent composition is in the range of about 80:20 to about 95: 5. The solder paste of claim 16, wherein the weight ratio of the metal solder powder to the solder solvent composition is in the range of about 85:15 to about 90:10. The solder paste of claim 16, wherein the metal solder powder is a Pb-free solder alloy powder having a melting point in a range from about 70 ° C. to about 400 ° C. 18. The solder paste of claim 16, wherein the promoter is selected from the group consisting of 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole, and mixtures thereof. 17. The solder paste of claim 16, wherein the activating component consists mainly of methylsuccinic acid and the facilitating component consists mainly of 2-ethylimidazole. The method of claim 17, wherein the base component ranges from about 5 to about 95 wt% of the solder solvent composition, the solvent component ranges from about 5 to about 95 wt% of the solder solvent composition, and wherein the activation component is about about the solder solvent composition. In the range of 1 to about 30 wt%, the facilitating component is in the range of about 0.5 to about 15 wt% of the solder solvent composition, the rheological component is in the range of about 0.5 to about 15 wt% of the solder solvent composition, and the corrosion inhibitor component A solder paste, characterized in that in the range of about 0.1 to about 5 wt% of the silver solder solvent composition. 18. The method of claim 17 wherein the base component is in the range of about 20 to about 50 wt% of the solder solvent composition, the solvent component is in the range of about 20 to about 70 wt% of the solder solvent composition, and the activating component is about about the solder solvent composition. In the range of 2 to about 20 wt%, the facilitating component is in the range of about 3 to about 11 wt% of the solder solvent composition, the rheological component is in the range of about 1 to about 11 wt% of the solder solvent composition, and the corrosion inhibitor component A solder paste, characterized in that it ranges from about 0.5 to about 3 wt% of the silver solder solvent composition. The method of claim 17, wherein the base component is wood rosin, rubber rosin, tall oil rosin, disproportionated rosin, hydrogenated rosin, polymerized rosin, hydrogenated resin, hydrogenated rubber tree rosin, carboxyl group-containing resin, polyester resin, acrylic resin, styrene male A thermoplastic resin selected from the group consisting of acid resins, epoxy resins, phenol resins, and mixtures thereof; The solvent component is selected from the group consisting of ketones, alcohols, esters of alcohols, aromatic solvents, glycol ethers, terpenes, petroleum distillates, hydroxy-terminated polybutadienes and mixtures thereof; The rheological component is selected from the group consisting of hydrogenated castor oil, castor oil based thixotropic agents, polyamides, polyethylene waxes and mixtures thereof; The corrosion inhibitor component is a solder paste, characterized in that selected from the group consisting of phosphine derivatives, triazole derivatives and mixtures thereof. Applying a deposit of solder paste to at least one solderable surface, the solder paste comprising a metal solder powder and a solder solvent composition, wherein the solder solvent composition comprises a base component, a solvent component, an active component containing methyl succinic acid And a facilitating component containing an imidazole compound or derivative; Wetting both solderable surfaces with molten solder by applying heat to the at least one solderable surface to reflow the solder paste; And Bonding the two solderable surfaces by cooling the molten solder to solidify the solder. The two compounds of claim 25 wherein the facilitating component is selected from the group consisting of 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole, and mixtures thereof. Method of joining solderable surfaces. The method of joining two solderable surfaces according to claim 25, wherein the solder paste is applied through screen printing or yarns. (a) an electronic component having a plurality of solder wettable pads; (b) a substrate having electrical contacts corresponding to the solder wettable pads of the electronic component; And (c) (iii) a base component;     (Ii) solvent components;     (Iii) an active ingredient containing methylsuccinic acid;     (Iii) an accelerating component containing an imidazole compound or derivative;     (Iii) optionally, a rheological component; And     (Iii) optionally an electronic component assembly comprising a solder solvent composition comprising a corrosion inhibitor component and a solder paste between the solder wettable pad and the electrical contact, the metal solder powder. The electronic component assembly of claim 28, wherein the facilitating component is selected from the group consisting of 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole, and mixtures thereof. . A method for producing a solder solvent composition comprising mixing an active ingredient containing methyl succinic acid and an accelerating ingredient containing an imidazole compound or derivative. 31. The solder solvent composition of claim 30 wherein the facilitating component is selected from the group consisting of 2-methyl-4-ethylimidazole, 2-methylimidazole, 2-ethylimidazole, and mixtures thereof. Manufacturing method. 32. The method for producing a solder solvent composition according to claim 31, wherein the promoting component is 2-ethylimidazole. 33. The method of claim 32, wherein the base component, the solvent component, optionally the rheological component, and optionally the corrosion inhibitor component are mixed with the activating component and the accelerating component. 34. The composition of claim 33, wherein the base component is in the range of about 5 to about 95 wt% of the solder solvent composition, the solvent component is in the range of about 5 to about 95 wt% of the solder solvent composition, and wherein the activation component is about about the solder solvent composition. In the range of 1 to about 30 wt%, the facilitating component is in the range of about 0.5 to about 15 wt% of the solder solvent composition, the rheological component is in the range of about 0.5 to about 15 wt% of the solder solvent composition, and the corrosion inhibitor component A method for producing a solder solvent composition, characterized in that it ranges from about 0.1 to about 5 wt% of the silver solder solvent composition. 34. The solder of claim 33, wherein the base component, solvent component, rheological component, and corrosion inhibitor component are mixed at a temperature in the range of about 80 ° C to about 150 ° C for a duration of about 1 to about 3 hours. Solvent composition production method. 36. The solder solvent composition of claim 35, wherein the heated mixture of base component, solvent component, rheological component, and corrosion inhibitor component is cooled to a temperature of less than about 40 [deg.] C. prior to mixing with the activating and promoting components. Manufacturing method.