TW201607992A - Solder flux composition - Google Patents

Abstract

The present invention is related to a solder flux composition, which includes: a main composition, a sulfonate salt, and a solvent distributing the main composition and the sulfonate salt. A hydrolysis reaction occurs when the sulfonate salt is contacting to water in reflow soldering process, such that the hydrolysis reaction is capable of consuming water vapor generated from high temperature reflow soldering process, decreasing the generation of voids of solder bump, and improving reliability and mechanical strength of the solder point.

Description

Flux composition

The invention relates to a flux, in particular to a flux for soldering, in particular to a flux for soldering for reducing solder joint voids.

A flip-chip packaged semiconductor device, such as an integrated circuit, having tin alloy bumps formed on one surface of the wafer, commonly referred to as bumps, as a wafer-to-board and flip-chip packaged circuit, It can be a ceramic substrate, a printed circuit board, a flexible circuit board or a germanium wafer. The solder paste is printed on the wafer, and after heating at a high temperature, the alloy material in the solder paste is agglomerated into a hemispherical shape to form a bump on the surface of the wafer. After the alloy material is solidified, the bumps can be accurately connected to their corresponding flip-chips, and then the alloy material is secondarily reflowed by high temperature to re-solder the bumps between the wafers.

In the bump packaging technology, the screen printing method is the main process method. However, the screen printing method is prone to voids in minute bumps, and the reliability of solder ball breakage or offset is likely to occur in the post-process flip chip package bonding process.

The general flux composition includes rosin, active agent, solvent and anti-sagging agent; flux can be divided into solid flux, paste flux and liquid flux depending on the appearance and application. The solid flux is generally wrapped in a tin wire. When the wire is soldered, the wrapped solid flux removes the oxidized material from the solder joint. Paste flux is used for solder paste prepared by mixing flux and solder powder. It is formed on the substrate by printing. After placing the components, soldering is also applied. After the substrate is coated, the solder balls are placed. In addition to the positional shift of the solder ball, it can be directly heated and soldered to become a product. Liquid flux is usually used for wave soldering, and the fine spray or foam is evenly coated on the substrate to remove the base. After the oxidized material on the board, the substrate is brought into contact with the molten metal for soldering.

A typical example of soldering is soldering of circuit boards and electronic products by reflow soldering. The paste solder paste used in the reflow method is formed by mixing solder powder and a paste flux material, and printing a solder paste on a predetermined position of the substrate, and preheating and then heating and soldering under appropriate conditions.

However, in the bump packaging technology, there is a problem of bump voids. There are six reasons for bump voids: the first type of void is mainly due to the various chemical components of the flux in the solder material, or the circuit. The water vapor in the plates and components is caused by evaporation during the reflow process. As they evaporate, these gases are trapped in the molten solder and eventually form voids, the largest of the six voids. The second type of bump voids often occur between the solder joint and the surface of the circuit substrate, mainly due to the pits on the surface of the circuit substrate coating, so that after reflow, voids are formed. Such voids are often found on surface coated panels of silver. The third type of void is mainly small cracks caused by lead-free tin-silver-copper alloys. When the fourth type of void has a welding material at the UBM (Under Bump Metallurgy), the unfilled portion of the under-metallurgical layer is easily formed into a void after reflow. If you print the solder paste twice or twice, or use a smaller powder (Type 4 powder), you can reduce the appearance of such voids. The fifth type of voids in the tin-copper intermetallic layer (IMC), excessive aging, or excessive thermal cycling, may increase the voids in the intermetallic layer. The industry is also discussing the final cause. The sixth type of voids often appear on the metal layer of the solder and the circuit substrate, and is likely to be caused by the original manufacturing defects of the circuit board copper plate.

The hydrolysis reaction using the sulfonate in the present invention consumes water vapor generated during reflow, thereby reducing the generation of bump voids.

The present invention provides a flux comprising: a main ingredient component, Selected from the group consisting of a rosin-type resin and a water-soluble compound; a sulfonate; and a solvent in which the main component and the sulfonate are dispersed.

The sulfonate undergoes a hydrolysis reaction when it is exposed to water during the reflow process, and preferably has the following formula I:

Wherein R is selected from the group consisting of C3-C6 saturated or unsaturated, linear or branched ketohydrocarbyl, C1-C4 saturated or unsaturated, linear or branched carboxyl, C1-C4 saturated or not Saturated, linear or branched hydroxyhydrocarbyl, C1-C3 saturated or unsaturated, linear or branched aminohydrocarbyl, unsubstituted or unsubstituted aryl Or a group consisting of arylhydrocarbyl.

According to the present invention, the hydrolysis reaction of the sulfonate can consume water vapor generated during reflow, thereby reducing the occurrence of bump holes and increasing the reliability and mechanical strength of the solder joint.

The present invention further provides a solder paste for solder comprising a tin alloy powder uniformly blended with a flux according to any one of the preceding claims.

In the process of high temperature reflow, for example, the organic acid in the solder reacts with the tin oxide at a high temperature or the moisture inside the circuit board or the electronic component is heated, and it is possible to generate water vapor. The water vapor causes voids in the bumps. In this case, the flux contains a sulfonate which undergoes a hydrolysis reaction when it is in contact with water during the reflow process, thereby consuming water vapor generated during high-temperature reflow and reducing the occurrence of bump voids.

The term "sulfonate" as used in this specification is intended to cover any term. How to have the above formula I, and at a high temperature, preferably at a soldering temperature of less than 450 ° C, more preferably at a soldering temperature of less than 350 ° C, such as a soldering temperature of 100 ° C to 300 ° C, The sulfonate which undergoes the hydrolysis reaction in the following formula will be substantially followed.

In one embodiment, the R group in the sulfonate is selected from the group consisting of substituted or unsubstituted phenyl, naphthyl and anthracenyl. In a preferred embodiment, the R group in the sulfonate is selected from with a group consisting of wherein R ₁ , R ₂ and R ₃ are individually selected from a ketohydrocarbyl group saturated or unsaturated, linear or branched from hydrogen, C3-C6; C1-C4 saturated or unsaturated, linear Or a branched carboxyl group; a C1-C4 saturated or unsaturated, linear or branched hydroxyhydrocarbyl group; and a group of C1-C3 saturated or unsaturated, linear or branched amine hydrocarbon groups. In a more preferred embodiment, the sulfonate is an alkali metal, ammonium or amine salt of a sulfonic acid, most preferably an alkali metal, ammonium or amine salt of p-toluenesulfonic acid, such as sodium p-toluenesulfonate. . In general, the sulfonate can be added to any conventional flux and used in combination with other components of the flux. The amount of sulfonate in the flux may depend on the amount of other components in the solder or the amount of moisture that may be generated during the reflow process. However, the sulfonate will increase the viscosity in the flux. Under high temperature conditions, water will produce sulfuric acid after hydrolysis, and sulfuric acid will attack the metal. Therefore, the addition of an excessive amount of sulfonate to the flux causes solder joint reliability and solder life to decrease. In a specific example, the weight percentage of the sulfonate in the flux of the present invention is preferably 0.01 to 5% by weight, more preferably 0.05 to 2.5% by weight.

The flux in this case additionally contains the components in the conventional flux and is prepared into a solid, paste or liquid flux according to the conventional process. In a preferred embodiment, the flux in the present case is a paste-like flux suitable for soldering electronic components on a circuit substrate. Agent.

The main component of the flux in this case is a resin, which can be further classified into a rosin type and a water-soluble compound depending on the type of the resin to be used. The content of the main component is usually from about 10 to 90% by weight, preferably from about 20 to 85% by weight, more preferably from about 30 to 80% by weight, based on the total mass of the flux. The flux of the present invention can be roughly classified into three types: solvent cleaning type, water cleaning type and no-clean type, depending on the composition of the main agent, especially the content of the rosin type resin. In a preferred embodiment, the flux in the present case is a water-cleaning flux that must be cleaned with saponified water or deionized water after soldering, or a no-clean flux that does not require substantial cleaning after soldering.

When the main component of the flux in this case is a rosin-type resin, the rosin-type resin is usually produced by refining and then selectively chemically modifying the original rosin obtained from the pine plant. Rosin-type resin can exhibit fluxing ability because it produces a variety of organic acids at high temperatures, mainly abietic acid, which is a glassy or partially crystalline yellow solid with a molecular formula of C ₁₉ H ₂₉ COOH, melting point 172 ° C. Rosin is active at high temperatures to remove contaminants and oxides from metal surfaces, and is an inactive solid at normal temperature and humidity, so it exhibits excellent safety and reliability after the completion of the welding process. Any type of rosin-type resin conventionally used in flux technology is suitable for use in the present invention. Preferred rosin-type resins include, but are not limited to, natural rosin such as colloidal rosin, wood rosin, and hydrogenated rosin, disproportionated rosin, polymerized rosin, acid-modified Rosin, liquid rosin, maleic rosin, maleic rosin anhydride and other rosin, and combinations thereof. In a preferred embodiment, the rosin-type resin in the flux of the present invention comprises a combination of colloidal rosin, wood rosin and liquid rosin.

When the main component of the flux of the present invention is a water-soluble compound compound, the water-soluble compound is preferably selected from the group consisting of polyethylene glycol, polyethylene glycol ether, tetraethylene glycol, propylene oxide glyceryl ether copolymer, octanoic acid. Glycerin, ethylene oxide propylene oxide A compound of the group consisting of a copolymer, a polyoxyethylene lauryl ether, a polyethylene glycol tallow amine ether, a nonylphenol polyethoxy alcohol, and combinations thereof. In a preferred embodiment, the water soluble compound in the flux of the present invention is polyethylene glycol.

In a specific example, the main component of the flux of the present invention may be a combination of a rosin-type resin and a water-soluble compound, and the ratio between the two may depend on the desired flux properties. In a preferred embodiment, the main component of the flux of the present invention comprises two rosin-type resins such as liquid rosin and wood rosin, and a polyethylene glycol water-soluble compound. More preferably, liquid rosin, wood rosin and polyethylene glycol are mixed in a ratio of 1:0.01:9 to 8:1:1, for example, in a ratio of 1:0.1:1 to 1:0.5:3, and cost assistance The main ingredient in the flux.

The flux of the present invention further comprises a solvent for dispersing and preferably uniformly dispersing the components of the flux, adjusting the viscosity and specific gravity of the rosin base and/or the integral flux, and assisting in heat transfer. Any of the conventional solvents in the flux technology that achieve the above objectives and do not chemically react with the components of the flux are suitable for use in the present invention. The content of the solvent in the flux depends on the viscosity and specific gravity of the desired rosin or flux, and is usually about 5 to 90% by weight, preferably about 7.5 to 85% by weight, based on the total weight of the flux. Good is about 10~80% by weight. In a preferred embodiment, the solvent is selected from the group consisting of glycol solvents such as diethylene glycol monoethyl ether, diethylene glycol, diethylene glycol, and the like. In a more preferred embodiment, the solvent is diethylene glycol monoethyl ether.

Optionally, the flux of the present invention further comprises an active agent which assists in removing light oxides and pollutants on the surface to be soldered. In particular, the active agent is suitable for reducing the metal oxide present on the surface to be welded at a high temperature to allow the metal oxide to be removed. This cleaning function allows the solder to quickly form a metal layer on the surface to be soldered and then soldered. The active agent used in the present invention may be any active agent used in the flux, and is usually from 0 to 25% by weight, preferably from 0.5 to 20% by weight, more preferably from 5 to 2% by weight based on the total weight of the flux. 15% by weight. active The agent is usually an organic acid, an organic amine or a mixture thereof, preferably selected from the group consisting of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and hydrazine. Diacid, undecanedioic acid, dodecanedioic acid, itaconic acid, o-hydroxybenzoic acid, malic acid, triethanolamine salts of such organic acids, imidazoles, triazoles, amines and combinations thereof The group formed. In a preferred embodiment, the active agent is an organic dibasic acid such as adipic acid.

In the specific case where the flux is a paste flux, the flux in the present case further includes an anti-sagging agent to adjust the rheology of the flux to ensure that the paste flux can exhibit thick or thin physical properties. It is also possible to keep the components in the flux kept in suspension after being uniformly mixed without precipitation. In this embodiment, the amount of the anti-sagging agent in the flux depends on the rheology of the flux to be obtained, and is usually about 0.01 to 12% by weight, preferably about 0.01, based on the total weight of the flux. 8% by weight, more preferably about 0.5 to 6% by weight. Preferably, the anti-sagging agent is selected from the group consisting of fatty acid guanamine, castor oil, fat wax, and combinations thereof. In a preferred embodiment, the anti-sagging agent is castor oil.

In addition to these components, depending on the type of flux and the desired fluxing effect, an additional antioxidant for protecting the surface and reducing the residue of the main component, activator, etc. after reflow can be added. An anticorrosive agent for substances, an aliphatic or aromatic nonionic surfactant for reducing the surface tension generated by contact of the solder with the surface to be welded and enhancing the penetration of the organic acid activator, and a solid component such as an activator from the solution a medium-dissolved cosolvent, as well as a film former, a stabilizer, a foaming agent, a thickener, and the like. Suitable species and amounts of these additional additives are familiar to those of ordinary skill in the art of flux related art.

In a preferred embodiment, the flux in the present invention is basically composed of the aforementioned sulfonate, a main component, a solvent, an active agent and an anti-sagging agent, and more preferably the rosin-type resin is selected from the group consisting of colloidal rosin, Wood rosin, liquid rosin and combinations of them The group consisting of the water-soluble compound is polyethylene glycol, the sulfonate is p-toluenesulfonate, such as sodium p-toluenesulfonate, the active agent is adipic acid, the anti-sagging agent is castor oil, and the solvent is Diethylene glycol monoethyl ether. As used herein, "substantially composed of" means that the combination of components described above does not exclude the inclusion of other undocumented components which do not substantially affect the properties of the flux of the present invention. In another preferred embodiment, the flux of the present invention consists solely of the foregoing sulfonate, a base component, a solvent, an active agent, and an anti-sagging agent.

The fluxing method of the present invention is the same as the conventional fluxing method, and involves mixing or suspending various solid or liquid components of the flux in a solvent at a suitable temperature, except that the addition of the present invention is disclosed in the mixing process. Sulfonate. The detailed fabrication process of the flux is familiar to those of ordinary skill in the art of flux related. In the specific example in which the flux is a paste flux, the flux may be further mixed with the metal solder powder to prepare a uniform paste. Examples of commonly used metal solder powders include, but are not limited to, tin alloy powders and lead alloy powders. Tin alloy powder is mainly composed of tin, and metal elements such as lead, silver, nickel, bismuth, copper, indium and antimony may be added depending on the properties of the solder to be obtained. Lead alloy powder is mainly composed of lead, and metal elements such as tin, silver, nickel, bismuth, copper, indium and antimony may be added depending on the properties of the solder to be obtained. The ratio of the metal solder powder and the flux is not limited, and usually 80 to 97% by weight of the metal powder is mixed with 3 to 20% by weight of the flux, preferably 85 to 90% by weight and 10 to 15% by weight. The flux is mixed.

The flux application method in this case is the same as the conventional flux. As previously mentioned, the solid flux is typically wrapped in a tin wire that is heated together with the tin wire and applied to the solder joint to complete the soldering. The paste flux is usually formed by printing on a predetermined position of the substrate, and after the components are placed, the soldering is heated by reflow. Liquid flux is usually used for wave soldering. The flux is sprayed or evenly coated on the substrate. After removing the oxidized material on the substrate, the substrate is contacted with the molten metal for soldering. The flux in this case is particularly suitable for soldering, and the heating temperature during soldering is below 450 ° C, preferably below 350 ° C. For example, in the temperature range of 100 ° C to 300 ° C. Accordingly, the present invention also provides a solder containing the flux disclosed in the present specification.

The following examples are intended to illustrate the invention and are not intended to limit the scope of the invention.

In Example 1, 12 g of colloidal rosin, 20.50 g of liquid rosin, 32.00 g of wood rosin, 5.00 g of adipic acid, 24.00 g of diethylene glycol, 5.50 g of castor oil, and 1.00 g of sodium p-toluenesulfonate were heated and stirred. The solution is melted into a clear solution, and the flux is prepared after cooling; 88 g of tin powder is used (tin-copper alloy, the weight percentage of the alloy copper is 0.7, the balance is tin and trace impurities; the particle size of the tin powder is in the range of 15 to 25 μm. And 12 g of the flux was uniformly stirred and mixed to prepare a solder paste.

The preparation of Examples 2 to 3 was similar to that of Example 1, except that different amounts of rosin or non-rosin resin were added. The compositions and preparations of Comparative Examples 1 to 3 were similar to Examples 1 to 3, respectively, but a sulfonate was additionally added. The composition of these examples and comparative examples is shown in Table 1 below.

The solder hole test method is to print the solder paste on the wafer, and then The reflow is carried out in nitrogen gas having an oxygen content of 100 ppm or less, and the reflow temperature conditions are as shown in Table 2 below.

After the reflow was completed, the area ratio of the bump voids was measured with an X-ray detector (The Nordson Dage XD7600 NT Diamond X-ray). The test results are shown in Table 3 below.

The data of the measured bump voids showed that the same formulation of Example 1 and Comparative Example 1 was added with sodium p-toluenesulfonate, and the void area decreased from 4.13% of Comparative Example 1 to 1.26% of Example 1, and Example 2 The same as in Comparative Example 2, the void area decreased from 4.05% in Comparative Example 1 to 1.24% in Example 1. Example 3 compared In Example 1 and Example 2, the addition of sodium p-toluenesulfonate in Example 3 was small, and the ratio of the void area was high, but there was also a significant decrease as compared with Comparative Example 1 and Comparative Example 2. In Comparative Example 3, the solvent ratio of Comparative Example 3 was higher than that of Comparative Example 2 and Comparative Example 1, and the pore area of Comparative Example 3 was high.

In general, the addition of sodium p-toluenesulfonate to the flux has a significant effect of improving the voids in the bumps, and the voids are almost unavoidable. The use of too much solvent also causes an increase in the void area ratio, which is assisted by the addition of sodium p-toluenesulfonate. The weight percentage of the flux is 0.05 or more, and the test result is quite good.

While the present invention has been shown and described with reference to the preferred embodiments of the preferred embodiments of the present invention, the invention is not limited to the above-described embodiments, and those skilled in the art should understand that various forms and details can be changed therein. Without departing from the scope of the invention as covered by the appended claims.

Claims (20)

A flux comprising: a main component selected from the group consisting of a rosin-type resin and a water-soluble compound; a sulfonate; and a solvent in which the main component and the sulphur are dispersed Acid salt. The flux of claim 1, wherein the sulfonate has the following formula I: Wherein R is selected from the group consisting of C3-C6 saturated or unsaturated, linear or branched ketohydrocarbyl, C1-C4 saturated or unsaturated, linear or branched carboxyl, C1-C4 saturated or not Saturated, linear or branched hydroxyhydrocarbyl, C1-C3 saturated or unsaturated, linear or branched aminohydrocarbyl, unsubstituted or unsubstituted aryl Or a group consisting of arylhydrocarbyl. A flux as claimed in claim 2, wherein the R group is selected from the group consisting of substituted or unsubstituted phenyl, naphthyl and anthracenyl groups. A flux according to claim 3, wherein the R group is selected from the group consisting of with a group consisting of; wherein R ₁ , R ₂ and R ₃ are individually selected from the group consisting of hydrogen or C3-C6 saturated or unsaturated, linear or branched ketohydrocarbyl, C1-C4 saturated or unsaturated, linear Or a group of branched carboxyl groups, C1-C4 saturated or unsaturated, linear or branched hydroxyhydrocarbyl groups, C1-C3 saturated or unsaturated, linear or branched amine hydrocarbon groups. A flux according to claim 4, wherein the sulfonate is an alkali metal salt, an ammonium salt or an organic ammonium salt. A flux according to claim 5, wherein the sulfonate is sodium p-toluenesulfonate. The flux of the first aspect of the patent application, wherein the content of the sulfonate in the flux is 0.01 to 5% by weight based on the total weight of the flux. For example, the flux of the seventh aspect of the patent application, wherein the content of the sulfonate in the flux is 0.05 to 2.5% by weight based on the total weight of the flux. The flux according to claim 1, wherein the main component comprises a gelatin rosin, wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, acid modified rosin, liquid rosin, male rosin, Malay A rosin-type resin in the group consisting of rosin anhydride and a combination thereof. The flux of claim 1, wherein the main component comprises a copolymer selected from the group consisting of polyethylene glycol, polyethylene glycol ether, tetraethylene glycol, oxypropylene glyceryl ether, octanoic acid glycerin, epoxy A water-soluble compound in the group consisting of a copolymer of an alkoxypropylene oxide, a polyoxyethylene lauryl ether, a polyethylene glycol tallow amine ether, a nonylphenol polyethoxy alcohol, and a combination thereof. The flux of claim 1, wherein the content of the main component is from 10 to 90% by weight based on the total weight of the flux. The flux of claim 11, wherein the content of the main component is 30 to 80% by weight based on the total weight of the flux. The flux of claim 1, wherein the solvent is a glycol-based solvent selected from the group consisting of diethylene glycol monoethyl ether, diethylene glycol, and diethylene glycol. A flux as claimed in claim 1 further comprising an active agent for assisting in the removal of metal oxides and contaminants from the surface to be welded. The flux of claim 14, wherein the active agent is selected from the group consisting of Acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, itaconic acid, o-hydroxybenzoic acid , malic acid, a combination of triethanolamine salts, imidazoles, triazoles, amines and combinations of these organic acids. The flux of claim 15 wherein the active agent is from 1 to 5% by weight based on the total weight of the flux. The flux of claim 1 further comprising an anti-sagging agent for adjusting the rheology of the flux selected from the group consisting of fatty acid decylamine, castor oil, fat wax and the like. A group of combinations. A flux consisting essentially of: a principal component selected from the group consisting of a rosin-type resin and a water-soluble compound, wherein the rosin-type resin is selected from the group consisting of colloidal rosin, a group consisting of wood rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, acid-modified rosin, liquid rosin, maleic rosin, maleic rosin anhydride, and combinations thereof, and wherein the water-soluble compound is selected from the group consisting of Polyethylene glycol, polyethylene glycol ether, tetraethylene glycol, copolymer of oxypropylene glyceryl ether, octyl glycerol, copolymer of ethylene oxide propylene oxide, polyoxyethylene lauryl ether, polyethylene glycol a group consisting of a combination of tallow amine ether, nonylphenol polyethoxy alcohol, and combinations thereof; a sulfonate having the following general formula I: Wherein R is selected from the group consisting of C3-C6 saturated or unsaturated, linear or branched ketohydrocarbyl, C1-C4 saturated or unsaturated, linear or branched carboxyl, C1-C4 saturated or not Saturated, linear or branched hydroxyhydrocarbyl, C1-C3 saturated or unsaturated, linear or branched aminohydrocarbyl, unsubstituted or unsubstituted aryl Or a group of arylhydrocarbyl groups; an active agent for assisting in the removal of metal oxides and contaminants on the surface to be welded; an anti-sagging agent; and a solvent in which the main component is dispersed, Sulfonate, active agent and anti-sagging agent. The flux of claim 18, wherein the rosin-type resin is selected from the group consisting of colloidal rosin, wood rosin, liquid rosin, and a combination thereof, and the water-soluble compound is polyethylene glycol. The sulfonate is p-toluenesulfonate, the active agent is adipic acid, the anti-sagging agent is castor oil, and the solvent is diethylene glycol monoethyl ether. A solder paste for soldering comprising a tin alloy powder uniformly blended with a flux according to any one of the preceding claims.