CN115846939A - Cleaning-free halogen-free high-lead solder paste and preparation method thereof - Google Patents
Cleaning-free halogen-free high-lead solder paste and preparation method thereof Download PDFInfo
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- CN115846939A CN115846939A CN202211622958.5A CN202211622958A CN115846939A CN 115846939 A CN115846939 A CN 115846939A CN 202211622958 A CN202211622958 A CN 202211622958A CN 115846939 A CN115846939 A CN 115846939A
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Abstract
The invention provides a soldering flux with low rosin content, which does not use halogen surfactants and solvents, and can effectively solve the problem that paste is not formed due to low rosin content by selecting proper surfactants, namely fatty alcohol ethoxylate Lutensol AT 25 and diethanol amine for compounding and a thixotropic agent containing polyamide. The corrosion inhibitor can further improve the forming problem of the paste by using the imidazole and azole corrosion inhibitors and improve the oxidation resistance of the paste. The raw materials of the soldering flux are common and easy to obtain, the preparation process is simple and convenient, the prepared paste has good viscosity, the oxidation resistance and the weldability of the solder paste can be kept, finally formed welding spots are bright and full, only a small amount of residues are left after welding and no halogen is contained, and the requirement of no cleaning is completely met; avoids the use of Freon or trichloroethylene and the like, and is more environment-friendly.
Description
Technical Field
The invention belongs to the technical field of welding, and relates to a soldering flux, in particular to a cleaning-free halogen-free high-lead solder paste prepared by using the soldering flux and a preparation method thereof.
Background
The high lead-tin paste is suitable for high-temperature welding, the melting point of the alloy reaches over 280 ℃, the lead content is higher than 85%, the high lead-tin paste belongs to RoHS exemption, and the high lead-tin paste is specially used for packaging and welding power semiconductors and mainly comprises a power tube, a diode, a triode, a rectifier bridge, a small integrated circuit and the like. At present, the environmental protection requirements of various countries on electronic products are higher and higher, countries such as Europe and America have strict requirements on executing environmental protection standards, and the flux is required not to contain halogen. However, the cleaning-free soldering flux is used for lead-free solder paste, the soldering flux used on the high-lead solder paste is mainly rosin-based soldering flux, the main components of the soldering flux are rosin, halogen surfactants and solvents, the residual soldering flux is more likely to cause corrosion and electric leakage of electronic components after welding, and the residual halogen is likely to cause strong chemical corrosion in a high-temperature and humid environment. Therefore, people need to clean the detergent by using Freon, trichloroethylene and the like, and the environment is greatly polluted.
Disclosure of Invention
The invention aims to provide the cleaning-free halogen-free high lead-tin paste aiming at the defects of the prior art, few residues are left after welding, no halogen is contained, the cleaning-free requirement can be completely met, the raw materials of the high lead-tin paste are common and easy to obtain, and the preparation process is simple.
In order to achieve the purpose, the invention adopts the technical scheme that: the cleaning-free halogen-free soldering flux comprises the following components in parts by weight: 4-12 parts of rosin, 2-5 parts of thixotropic agent, 4-10 parts of active agent, 2-6 parts of surfactant, 3-8 parts of corrosion inhibitor and 60-80 parts of organic solvent; the surfactant comprises a composition of fatty alcohol ethoxylates, lutensol AT 25 and diethanolamine, and the thixotropic agent comprises polyamide; the corrosion inhibitor is at least one of imidazole or azole corrosion inhibitor.
The flux paste has the advantages that the rosin content of the general flux is higher, and in order to prepare the flux with less residual after welding, the rosin consumption is reduced. However, the use of the rosin in a reduced amount makes the flux paste less likely to form paste, and the viscosity is poor, and the oxidation resistance, handling properties and solderability of the flux paste are significantly reduced. In order to solve the problem, the invention uses fatty alcohol ethoxy compound Lutensol AT 25 and diethanol amine for compounding, uses polyamide as a thixotropic agent component, and adds a certain amount of corrosion inhibitor, thereby effectively solving the problems of non-molding paste and poor use effect caused by rosin reduction. The soldering flux has good viscosity, can keep the oxidation resistance and the weldability of the solder paste, and finally forms bright and full welding spots, has little residue after welding, and completely meets the requirement of no cleaning; and a halogen surfactant and a solvent are not used, so that the phenomenon that residual halogen easily causes strong chemical corrosion is avoided.
As a preferred embodiment of the present invention, the thixotropic agent is a composition of polyamide and polyamide-modified castor oil, and the thixotropic agent is a mixture of fatty alcohol ethoxylate Lutensol AT 25: diethanolamine =1 to 3:1 to 2.
By using the proportion, the formed flux paste has less residues and better effect.
As a preferred embodiment of the invention, the corrosion inhibitor comprises at least one of 2-methylimidazole, 2-ethylimidazole, benzotriazole and 2-methylbenzimidazole.
The use of the imidazole and azole corrosion inhibitors can improve the oxidation resistance of the paste and also has a certain promotion effect on the forming of the paste.
More preferably, the corrosion inhibitor is a composition of an imidazole corrosion inhibitor and an azole corrosion inhibitor.
The imidazole corrosion inhibitor and the azole corrosion inhibitor are used together, so that the antioxidant effect is better, and the corrosion can be effectively avoided.
As a preferred embodiment of the present invention, the rosin includes at least one of a hydrogenated rosin and a modified rosin.
In a preferred embodiment of the present invention, the active agent is at least one of succinic acid, adipic acid, and benzoic acid.
As a preferred embodiment of the present invention, the organic solvent includes at least one of triethylene glycol, diethylene glycol hexyl ether, ethylene glycol monobutyl ether, diethylene glycol ethyl ether, tripropylene glycol butyl ether.
Correspondingly, the invention also provides a preparation method of the soldering flux, which comprises the following steps:
(1) Weighing raw materials of the soldering flux according to the weight parts, putting the raw materials into a reaction kettle for heating, heating to 50-60 ℃, starting stirring, stopping heating when the temperature is raised to 90-94 ℃, and continuing stirring;
(2) Cooling the mixture in the step (1) to 75-80 ℃, stopping stirring, naturally cooling to normal temperature to obtain paste soldering flux, grinding, and then placing in a refrigerator at 0-4 ℃ for refrigeration for more than 12 h;
(3) And taking out the soldering flux from the refrigerator, and placing for over 2 hours at normal temperature to return to the temperature to obtain the soldering flux.
The soldering flux provided by the invention can be effectively prepared according to the method provided by the invention.
In a preferred embodiment of the present invention, the stirring speed in the step (1) is 5000 to 5200r/min, and the stirring time is 35 to 45min.
Meanwhile, the invention also claims the application of the soldering flux.
The soldering flux of the invention can be combined with different alloys to prepare corresponding soldering paste.
Further, the invention also provides a cleaning-free halogen-free high-lead solder paste which is prepared from the following components in parts by weight: 88 to 92 parts of soldering tin powder alloy and 8 to 12 parts of soldering flux; the solder powder alloy is high-lead solder powder alloy with lead content more than 85%.
The soldering flux disclosed by the invention can be used for preparing a cleaning-free halogen-free high-lead solder paste by being alloyed with a certain amount of high-lead solder powder, and can effectively avoid the residue of the soldering flux when being used for packaging and welding a power semiconductor, so that the corrosion is avoided.
In a preferred embodiment of the present invention, the solder powder alloy is at least one of sn5pb92.5ag2.5 and Sn3Pb 97.
Further, the invention also provides a preparation method of the cleaning-free halogen-free high lead solder paste, which comprises the following steps: weighing the solder powder alloy and the soldering flux according to the weight parts, placing the solder powder alloy and the soldering flux into a dispersion machine for stirring at the stirring speed of 15-25 r/min for 5-15 min, and then continuously stirring for 5-15 min under vacuum to obtain the cleaning-free halogen-free high-lead solder paste.
Meanwhile, the invention also claims the application of the cleaning-free halogen-free high lead solder paste.
The invention provides a soldering flux with low rosin content, which does not use halogen surfactants and solvents, and can effectively solve the problem that paste is not formed due to low rosin content by selecting proper surfactants, namely fatty alcohol ethoxylate Lutensol AT 25 and diethanol amine for compounding and a thixotropic agent containing polyamide. The corrosion inhibitor can further improve the forming problem of the paste by using the imidazole and azole corrosion inhibitors and improve the oxidation resistance of the paste. The raw materials of the soldering flux are commonly and easily available, the preparation process is simple and convenient, the prepared paste has good viscosity, the oxidation resistance and the weldability of the solder paste can be kept, finally formed welding spots are bright and full, only a small amount of residues are left after welding and no halogen is contained, the requirement of no cleaning is completely met, the use of Freon or trichloroethylene is avoided, and the soldering flux is more environment-friendly.
Detailed Description
To better illustrate the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to specific examples.
Examples 1 to 5
Examples of fluxing agents according to the present invention, the compositions of which are shown in table 1 below.
Table 1 examples 1-4 flux composition
The preparation method of the soldering flux comprises the following steps:
(1) Weighing raw materials of the soldering flux according to the weight parts, putting the raw materials into a reaction kettle for heating, heating to 50-60 ℃, starting stirring, stopping heating when the temperature is raised to 90-94 ℃, and continuing stirring at the stirring speed of 5000-5200 r/min for 35-45 min;
(2) Cooling the mixture in the step (1) to 75-80 ℃, stopping stirring, naturally cooling to normal temperature to obtain paste soldering flux, grinding, and then placing in a refrigerator at 0-4 ℃ for refrigeration for more than 12 h;
(3) And taking out the soldering flux from the refrigerator, and placing for over 2 hours at normal temperature to return to the temperature to obtain the soldering flux.
Comparative examples 1 to 7
A comparative example of a soldering flux according to the present invention, the composition of which is shown in table 2 below.
Table 2 comparative examples 1-8 flux composition
The preparation method of the various proportional scaling powders is the same as the examples.
Example 8
Solder pastes (solder powder alloy Sn3Pb 97) were prepared according to table 3 below.
Table 3 comparative examples 1-8 flux composition
The preparation method of each high-lead solder paste comprises the following steps: weighing the solder powder alloy and the soldering flux according to the weight parts, placing the solder powder alloy and the soldering flux into a dispersion machine for stirring at the stirring speed of 15-25 r/min for 5-15 min, and then continuously stirring for 5-15 min under vacuum.
The performance of the solder paste of each formula is further tested, and the test method is as follows:
(1) Viscosity: spiral rotation test method (viscometer type: malcom PCU-02V, measuring range: 0.2-300 Pa.s)
(2) Tin bead, residue, corrosivity: and observing the welding spot by a microscope after the welding spot is obtained by welding the tin melting furnace.
(3) Expansion ratio: selecting a standard copper sheet, and using the copper sheet as a welded surface test piece after the copper sheet is subjected to polishing, acid washing, baking and other processes; the standard alloy used for tin-lead solder is a solid tin wire of Sn60Pb40 or Sn63Pb37, the wire diameter of the tin wire is 1.5-1.6 mm, the tin wire is wound into a ring with the inner diameter of 3mm, and the mass of the whole solder ring is about 0.3 g. And (3) testing conditions: the soldering temperature for the tin-lead process was 235 c. During testing, the prepared solder ring is placed in the center of a standard copper sheet, about 0.1ml of soldering flux is dripped into the ring (or the soldering flux is dripped firstly and then the solder ring is placed), then the test piece is placed on the surface of a tin melting furnace with a set soldering temperature, the test piece is taken out after being placed for 20 seconds, and after cooling, residues are cleaned by a solvent, and then the height (h) of the soldering point is measured.
The spreading factor (S) is calculated as follows: SR = (D-h)/Dx100%
Where D is the diameter of the solder ball assuming equal volume to the solder ring used, i.e., D =1.24v1/3,
v = m/ρ, where m is the mass of the solder ring (weighed) and ρ is the density of the solder ring.
The results of the individual solder paste tests are shown in Table 4.
Table 4 solder paste test results
| Test items | Soldering flux | Viscosity of the oil | Tin bead | Postweld residue | Spreading factor | Corrosiveness of |
| 1 | Example 1 | 45.3 | Is free of | Is rarely used | 85.7 | No corrosion phenomenon appears |
| 2 | Example 2 | 43.6 | Is free of | Is rarely used | 85.1 | No corrosion phenomenon |
| 3 | Example 3 | 43.9 | Is free of | Is rarely used | 86.3 | No corrosion phenomenon |
| 4 | Example 4 | 48.4 | Is composed of | Is rarely used | 85.6 | No corrosion phenomenon |
| 5 | Example 5 | 53.7 | Is free of | Is rarely used | 83.4 | No corrosion phenomenon appears |
| 6 | Example 6 | 46.2 | Is composed of | Is less | 86.4 | No corrosion phenomenon |
| 7 | Example 7 | 56.5 | Is composed of | Is rarely used | 82.8 | No corrosion phenomenon |
| 8 | Comparative example 1 | 41.5 | Is not substantially formed | Is less | / | No corrosion phenomenon |
| 9 | Comparative example 2 | 39.1 | Is not substantially formed | Is less | / | No corrosion phenomenon |
| 10 | Comparative example 3 | 40.1 | Much, poor forming | Is less | / | Slight corrosion phenomenon |
| 11 | Comparative example 4 | 42.7 | Much, poor forming | Is rarely used | / | Corrosion phenomenon appears |
| 12 | Comparative example 5 | 32.6 | Can not be molded | / | / | Corrosion phenomenon appears |
| 13 | Comparative example 6 | 59.7 | Is free of | Much more | 81.9 | No corrosion phenomenon |
| 14 | Comparative example 7 | 62.7 | Is free of | Much more | 82..4 | No corrosion phenomenon |
From table 4, it can be seen:
the halogen-free high-lead soldering paste prepared in the embodiments 1-5 of the invention has good performance, good stability, no tin bead, less residues after soldering, can completely meet the requirement of no cleaning, and has no corrosion phenomenon.
When the rosin is used in a large amount (comparative examples 6 and 7-test items 13 and 14), the forming effect of the paste can be effectively improved, but the cleaning-free purpose cannot be achieved due to a large amount of residues after welding.
When the amount of rosin is less, the compounding of the fatty alcohol ethoxylate Lutensol AT 25 and the diethanol amine is not used (refer to comparative examples 1 and 2-test items 8 and 9), the soldering flux cannot form paste, the viscosity of the obtained solder paste is reduced, the solderability is poor, and the problem that the paste is not formed when the amount of the rosin is low can be solved by compounding the fatty alcohol ethoxylate Lutensol AT 25 and the diethanol amine. And the amount of the surfactant and the absence of the polyamide also affect the paste forming effect and thus the welding effect (refer to comparative examples 3, 4 and 5).
In addition, as can be seen from comparative examples 3, 4 and 5, the corrosion inhibitor can reduce corrosion, and the imidazole corrosion inhibitor and the azole corrosion inhibitor are used together, so that the corrosion resistance effect is better.
Finally, it should be noted that the above contents are only used to illustrate the technical solutions of the present invention, and do not limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (10)
1. The cleaning-free halogen-free soldering flux is characterized by comprising the following components in parts by weight: 4-12 parts of rosin, 2-5 parts of thixotropic agent, 4-10 parts of active agent, 2-6 parts of surfactant, 2-8 parts of corrosion inhibitor and 60-80 parts of organic solvent; the surfactant comprises a composition of fatty alcohol ethoxylates, lutensol AT 25 and diethanolamine, and the thixotropic agent comprises polyamide; the corrosion inhibitor is at least one of imidazole or azole corrosion inhibitor.
2. The soldering flux according to claim 1, wherein the surfactant is a combination of fatty alcohol ethoxylate Lutensol AT 25 and diethanolamine in a mass ratio of fatty alcohol ethoxylate Lutensol AT 25: diethanolamine =1 to 3:1 to 2.
3. The flux according to claim 1, wherein the corrosion inhibitor comprises at least one of 2-methylimidazole, 2-ethylimidazole, benzotriazole, and 2-methylbenzimidazole; preferably, the corrosion inhibitor is a composition of an imidazole corrosion inhibitor and an azole corrosion inhibitor.
4. The flux of claim 1, wherein the thixotropic agent is a combination of polyamide and polyamide-modified castor oil;
the rosin comprises at least one of hydrogenated rosin and modified rosin;
the active agent is at least one of succinic acid, adipic acid and benzoic acid;
the organic solvent comprises at least one of triethylene glycol, diethylene glycol hexyl ether, ethylene glycol monobutyl ether, diethylene glycol ethyl ether and tripropylene glycol butyl ether.
5. The method for preparing the soldering flux according to claims 1 to 4, comprising the following steps:
(1) Weighing raw materials of the soldering flux according to the weight parts, putting the raw materials into a reaction kettle for heating, heating to 50-60 ℃, starting stirring, stopping heating when the temperature is raised to 90-94 ℃, and continuing stirring;
(2) Cooling the mixture in the step (1) to 75-80 ℃, stopping stirring, naturally cooling to normal temperature to obtain paste soldering flux, grinding, and then placing in a refrigerator at 0-4 ℃ for refrigeration for more than 12 h;
(3) And taking the soldering flux out of the refrigerator, and standing for over 2 hours at normal temperature to return to the temperature to obtain the soldering flux.
Preferably, in the step (1), the stirring speed is 5000-5200 r/min, and the stirring time is 35-45 min.
6. The use of the flux of claims 1-4.
7. The cleaning-free halogen-free high lead solder paste is characterized by comprising the following components in parts by weight: 88 to 92 parts of soldering tin powder alloy and 8 to 12 parts of soldering flux; the solder powder alloy is high-lead solder powder alloy with lead content more than 85%.
8. The clean-free halogen-free high lead solder paste of claim 7, wherein the solder powder alloy is at least one of Sn5Pb92.5Ag2.5 and Sn3Pb 97.
9. The method for preparing the no-clean halogen-free high lead solder paste of claim 7, comprising the following steps: weighing the solder powder alloy and the soldering flux according to the weight parts, placing the solder powder alloy and the soldering flux into a dispersion machine for stirring at the stirring speed of 15-25 r/min for 5-15 min, and then continuously stirring for 5-15 min under vacuum to obtain the cleaning-free halogen-free high-lead solder paste.
10. Use of the no-clean halogen-free high lead solder paste of claim 7.
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| CN202211622958.5A CN115846939A (en) | 2022-12-16 | 2022-12-16 | Cleaning-free halogen-free high-lead solder paste and preparation method thereof |
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| CN202211622958.5A CN115846939A (en) | 2022-12-16 | 2022-12-16 | Cleaning-free halogen-free high-lead solder paste and preparation method thereof |
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