CN118162803A - Soldering paste for BGA package and preparation method thereof - Google Patents

Abstract

The invention provides flux paste for BGA packaging and a preparation method thereof, and belongs to the technical field of flux paste for electronic packaging. The soldering paste comprises the following components: 20.0 to 25.0 percent of solvent, 35.0 to 40.0 percent of film forming agent, 5.5 to 6.0 percent of activating agent, 5.0 to 7.0 percent of thixotropic agent, 10.0 to 15.0 percent of humectant, 0.5 to 1.0 percent of surfactant, 1.5 to 2.0 percent of stabilizer, 3.0 to 5.0 percent of antioxidant and 3.0 to 5.0 percent of corrosion inhibitor. The soldering paste has the advantages of high storage stability, low corrosiveness after welding, adjustable viscosity, strong activity, less residues after welding, high welding quality and the like in the BGA packaging ball mounting process.

Description

Soldering paste for BGA package and preparation method thereof

Technical Field

The invention relates to the field of flux paste for electronic packaging, in particular to flux paste for BGA packaging and a preparation method thereof.

Background

Electronic packaging technology is one of the core technologies of the semiconductor industry and the integrated circuit industry, and has been rapidly developed in recent years. BGA (Ball GirdArray) ball grid array packages are a form of surface IC packaging that greatly increases packaging density and reduces packaging volume. With the high integration of chips, the requirements on packaging performance are more and more severe, and the traditional packaging form cannot meet the requirements of the current society.

The biggest difference between the BGA package and other package forms is that the solder balls replace the needle-shaped pins of the solder, and strict requirements are imposed on the coating process of the flux paste and the bonding quality of the BGA solder balls. Soldering paste is an indispensable component in the field of electronic packaging, and the quality of the soldering paste directly influences the quality and reliability of electronic products. In the field of BGA packaging, the flux paste is mainly applied to the process of ball mounting of the BGA to coat solder balls on a BGA pad. The soldering paste has the effects that in the ball mounting process of the BGA, a certain amount of soldering paste is coated on the surface of the base material, so that the adhesion force between the base material and the solder is enhanced, the BGA solder balls can be stably placed when being applied, and the efficiency and the yield are improved.

However, poor overall stability of the paste composition is a major problem today, which determines the lifetime of the product and thus affects the quality, reliability and stability of the BGA packaged product. In general, improper preparation, storage and use of the flux paste easily cause unstable surface viscosity, thick surface, insufficient consistency and the like of the flux paste, and further influence the printing stability in the BGA ball mounting process, so that defects, insufficient solder, lack of welding and the like of a pad pattern are caused. Therefore, the preparation of the flux paste with high storage stability, adjustable viscosity, small corrosion after welding and strong activity is a necessary trend in the BGA packaging industry.

Disclosure of Invention

In view of the above, the invention provides a flux paste for BGA package and a preparation method thereof, and the flux paste has the advantages of high storage stability, low corrosion after welding, adjustable viscosity, strong activity, less residues after welding, high welding quality and the like in the BGA package ball mounting process.

In order to achieve the technical effects, the invention adopts the following technical scheme:

a flux paste for BGA packages comprising, in mass percent:

Further, the solvent is prepared from diethylene glycol butyl ether and tetrahydrofurfuryl alcohol according to the weight ratio of 1:1-5 mass percent of a mixture. The main function of the solvent comprises dissolving the rest components in the soldering paste to make the soldering paste become uniform viscous liquid, and improving the viscosity stability and the storage life of the soldering paste.

Further, the film forming agent is at least one selected from the group consisting of perhydrogenated rosin, water white hydrogenated rosin, hydrogenated rosin and disproportionated rosin. The film forming agent has the functions of providing proper viscosity in the preparation process of the soldering paste, simultaneously enabling the welding spot to have better collapse resistance before reflow soldering and improving the reliability of the whole soldering.

Further preferably, the film former is prepared from perhydrogenated rosin and water white hydrogenated rosin in a ratio of 2:1 mass percent.

Further, the activator is at least one selected from azelaic acid, sebacic acid, glutaric acid, succinic acid, malonic acid and suberic acid. Further preferably, the activator is prepared from azelaic acid and sebacic acid according to a ratio of 0.7:1 mass percent. The action of the activator includes removing oxide from between the solder and the pad at the soldering temperature, thereby improving wettability between the solder and the pad.

Further, the thixotropic agent is castor oil. The thixotropic agent has lubricating effect in the printing process, improves the printing performance of the solder paste and is beneficial to demolding.

Further, the humectant is at least one selected from polyethylene glycol 8000 and glycerol. Further preferably, the humectant is polyethylene glycol 8000. The humectant has the effects of preventing soldering tin powder from being oxidized by contact with air, inhibiting the solder paste from being sanded and dried, and further effectively prolonging the storage time and the service life of the solder paste.

Further, the surfactant is alkylphenol ethoxylates. The surfactant has the function of better spreading the solder on the surface of the base material by reducing the surface tension of the base material, thereby obtaining a good welded joint.

Further, the stabilizer is paraffin wax. The stabilizer has the function of maintaining stability in the welding process, preventing bubbles and pinholes from being generated, and improving welding quality.

Further, the antioxidant is ascorbyl palmitate. The antioxidant functions to prevent the oxidation of the active material in the flux by inhibiting the formation of oxides between the solder and the copper substrate.

Further, the corrosion inhibitor is benzotriazole. The corrosion inhibitor can be added to form a layer of compact protective film on the surface of the copper substrate, so that corrosion to the copper plate is effectively reduced, growth of intermetallic compounds of a welding interface can be inhibited to a certain extent, and reliability of welding spots is improved.

The second object of the present invention is to provide a method for preparing a flux paste for BGA package, comprising the steps of:

(1) Weighing a solvent, a film forming agent and an activating agent according to mass percentage, mixing, heating and heating until the solvent, the film forming agent and the activating agent are completely dissolved to obtain a mixture A for later use;

(2) Adding the thixotropic agent into the mixture A, homogenizing for 3-5min after complete dissolution to obtain a mixture B for later use;

(3) Adding a humectant, a surfactant, a stabilizer, an antioxidant and a corrosion inhibitor into the mixture B, homogenizing for 3-5min after complete dissolution, and cooling to room temperature to obtain the soldering paste for BGA packaging.

Further, the temperature in the step (1) is raised to 90-100 ℃.

Compared with the prior art, the invention has the following beneficial effects: the flux paste provided by the invention has the advantages of high storage stability, low corrosiveness after welding, adjustable viscosity, strong activity, high welding quality and less residues after reflow welding and other welding in the BGA packaging ball mounting process.

Drawings

Fig. 1 is a viscosity test chart of the solder paste prepared in example 1 of the present invention;

FIG. 2 is a pattern of spreading of a paste flux prepared according to example 1 of the present invention;

FIG. 3 is a chart showing the solderability test of the paste composition of example 1 of the present invention;

FIG. 4 is a void fraction test chart of the solder paste prepared in example 1 of the present invention;

FIG. 5 is a surface topography of a paste prepared according to comparative example 1 of the present invention;

fig. 6 is a void fraction test chart of the solder paste prepared in comparative example 1 of the present invention;

FIG. 7 is a surface topography of a paste prepared according to comparative example 2 of the present invention;

fig. 8 is a void fraction test chart of the solder paste prepared in comparative example 2 of the present invention;

fig. 9 is a surface topography of a paste prepared according to comparative example 3 of the present invention;

Fig. 10 is a graph showing the printing performance of the paste prepared in comparative example 4 according to the present invention;

fig. 11 is a void fraction test chart of the solder paste prepared in comparative example 4 of the present invention;

Fig. 12 is a solderability testing chart of the solder paste prepared in comparative example 5 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the invention, are within the scope of the invention.

The test methods or test methods described in the following examples are all conventional methods unless otherwise specified; the starting materials and auxiliaries, unless otherwise specified, are obtained commercially from conventional sources or are prepared in conventional manner.

Example 1

A flux paste for BGA packaging comprises the following components in percentage by mass: 25.0wt% of solvent, 40.0wt% of film forming agent, 6.0wt% of activating agent, 5.0wt% of thixotropic agent, 15.0wt% of humectant, 1.0wt% of surfactant, 2.0wt% of stabilizer, 3.0wt% of antioxidant and 3.0wt% of corrosion inhibitor;

the solvent is prepared from diethylene glycol butyl ether and tetrahydrofurfuryl alcohol according to the following ratio of 1:1 mass percent of the mixture;

the film forming agent is prepared from perhydrogenated rosin and water white hydrogenated rosin according to the following weight ratio of 2:1 mass percent of a mixture;

The activator is prepared from azelaic acid and sebacic acid according to a ratio of 0.7:1 mass percent of a mixture;

The thixotropic agent is castor oil;

The humectant is polyethylene glycol 8000;

The surfactant is alkylphenol polyoxyethylene ether;

the stabilizer is paraffin;

The antioxidant is ascorbyl palmitate;

The corrosion inhibitor is benzotriazole.

The preparation method of the flux paste for BGA package comprises the following steps:

(1) Weighing a solvent, a film forming agent and an activating agent according to mass percentage, placing the solvent, the film forming agent and the activating agent in a reaction kettle, heating to 90-100 ℃, and stirring until the solvent is completely dissolved to obtain a mixture A for later use;

(2) Adding a thixotropic agent into a reaction kettle, mixing with the mixture A, stirring until the thixotropic agent is completely dissolved, and then opening a homogenizer for homogenizing for 5min to obtain a mixture B for later use;

(3) Adding a humectant, a surfactant, a stabilizer, an antioxidant and a corrosion inhibitor into a reaction kettle, mixing with the mixture B, stirring until the mixture is completely dissolved, starting a homogenizer for homogenizing for 5min, and cooling to room temperature to obtain soldering paste for BGA packaging;

(4) And (3) sequentially carrying out manual stirring and mechanical stirring on the soldering paste in the step (3) for 10min to obtain the soldering paste.

The soldering paste and the soldering paste prepared in example 1 are placed in a refrigerator at 0-10 ℃, the time for observing the soldering paste is 12 months, the time for observing the soldering paste is 6 months, the conditions of drying and sand generation do not occur on the surfaces of the soldering paste and the soldering paste, and the viscosity of the soldering paste and the soldering paste is stable, and the thermal slump and the weldability are excellent in the observing time.

Viscosity test was performed on the paste prepared in example 1, and viscosity test was performed on the paste using a PCU-285 viscosity tester of company MALCOM of japan, the measurement temperature was set to 25.0 ℃, the pre-stirring time was 10min, and the test time was 5min. As shown in fig. 1, under the condition of low-temperature storage at 0-10 ℃, the paste prepared in example 1 can maintain high stability within 12 months, and the viscosity of the paste is stabilized at about 35pa×s along with the extension of the standing time.

The spreading performance test was performed on the flux paste prepared in example 1, and the result is that the solder joint of the flux paste is round, the spreading rate is high, and the flux paste has no corrosiveness after welding, as shown in fig. 2.

The solder paste prepared in example 1 was tested for solderability, and tested on a BGA package having a pad size of 0.55mm, and as shown in fig. 3, the solder paste was excellent in solderability within 12 months, and no phenomena such as cold joint, solder leakage, etc. occurred on the package surface.

The voidage test was performed on the flux paste prepared in example 1, and as shown in fig. 4, the voidage of a single solder joint was 0.5%, less than 1%, and met the industrial-grade module standard.

Comparative example 1

The difference from example 1 is that the solvent is prepared from diethylene glycol methyl ether and tetrahydrofurfuryl alcohol in a ratio of 1:1 mass percent of the mixture.

The paste prepared in comparative example 1 was placed in a refrigerator at 0to 10c, and the surface stability of the paste was observed, and after 1 month, the paste appeared to dry out, sand out, and particles, and the surface glossiness was lowered, as shown in fig. 5; the void fraction of a single solder joint reaches 1.8%, which does not meet the industrial module standard, and the result is shown in fig. 6.

Comparative example 2

The difference from example 1 is that the solvent is prepared from diethylene glycol dibutyl ether and tetrahydrofurfuryl alcohol in a ratio of 1:1 mass percent of the mixture.

The paste prepared in comparative example 2 was placed in a refrigerator at 0-10 c, and after 2 months, the surface stability of the paste was observed, and the surface of the paste appeared to be sanded and particles, and the surface gloss was lowered, as a result of which, as shown in fig. 7, the void ratio of a single solder joint reached 1.3%, and the result was as shown in fig. 8, which did not meet the industrial-grade module standards.

Comparative example 3

The difference from example 1 is that the solvent is prepared from tripropylene glycol butyl ether and tetrahydrofurfuryl alcohol in a ratio of 1:1 mass percent of the mixture.

The paste and paste prepared in comparative example 3 were placed in a refrigerator at 0-10 ℃ and the surface stability of the paste and paste was observed, and after 14 days, the paste showed a substantial decrease in surface viscosity compared to example 1, the paste had a viscosity of 21.93pa×s, and a phenomenon of skip printing occurred at the time of thermal collapse and solderability test, and the result is shown in fig. 9.

Comparative example 4

The difference from example 1 is that the solvent is composed of diethylene glycol butyl ether and 2-ethyl-1, 3-hexanediol in a ratio of 1:1 mass percent of the mixture.

The flux paste prepared in comparative example 1 was placed in a refrigerator at 0-10 ℃ to observe the surface stability of the flux paste, and after 6 months, the surface of the flux paste appeared to dry out and sand, and the result is shown in fig. 10; when the film was subjected to a spreading test, the solder joint was unevenly distributed, and the void ratio of a single solder joint was 0.9%, and the result was shown in FIG. 11.

Comparative example 5

The difference from example 1 is that the solvent is composed of diethylene glycol methyl ether and 2-ethyl-1, 3-hexanediol in a ratio of 1:1 mass percent of the mixture.

The paste prepared in comparative example 5 was placed in a refrigerator at 0-10 ℃ and the surface stability of the paste was observed, after 7 days, the viscosity of the paste was greatly increased compared with example 1, the viscosity was 50.98pa×s, and it was not easy to leak under the steel mesh when the solderability test was performed, and the result was shown in fig. 12.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (9)

1. A paste composition for BGA packages, comprising, in mass percent:

2. A paste flux for BGA packages according to claim 1, wherein the solvent is prepared from diethylene glycol butyl ether and tetrahydrofurfuryl alcohol in an amount of 1:1-5 mass percent of a mixture.

3. A paste flux for BGA packages according to claim 1, wherein the film forming agent is at least one selected from the group consisting of perhydrogenated rosin, water white hydrogenated rosin, disproportionated rosin.

4. A paste flux for BGA packages according to claim 1, wherein the activator is selected from at least one of azelaic acid, sebacic acid, glutaric acid, succinic acid, malonic acid, suberic acid.

5. A paste flux for BGA packages according to claim 1, wherein the thixotropic agent is castor oil.

6. A paste flux for BGA packages according to claim 1, wherein the humectant is at least one selected from polyethylene glycol 8000, glycerol.

7. A paste flux for BGA packages according to claim 1, wherein the surfactant is alkylphenol ethoxylate, the stabilizer is paraffin wax, the antioxidant is ascorbyl palmitate, and the corrosion inhibitor is benzotriazole.

8. A method of preparing a paste flux for BGA packages according to any one of claims 1 to 7, comprising the steps of:

(1) Weighing a solvent, a film forming agent and an activating agent according to mass percentage, mixing, heating and heating until the solvent, the film forming agent and the activating agent are completely dissolved to obtain a mixture A for later use;

(2) Adding the thixotropic agent into the mixture A, homogenizing for 3-5min after complete dissolution to obtain a mixture B for later use;

(3) Adding a humectant, a surfactant, a stabilizer, an antioxidant and a corrosion inhibitor into the mixture B, homogenizing for 3-5min after complete dissolution, and cooling to room temperature to obtain the soldering paste for BGA packaging.

9. The method of preparing a paste for BGA packages according to claim 8, wherein the temperature of step (1) is raised to 90-100 ℃.