A lead-free and halogen-free solder wire and its preparation method

Abstract

The present application relates to the technical field of welding materials, and particularly relates to a lead-free and halogen-free solder wire and a preparation method thereof. The lead-free and halogen-free solder wire is prepared from a tin alloy and a soldering flux. The weight percentage content of the added soldering flux is 4-7%. The soldering flux is prepared from raw materials with the following weight percentage contents: 2-5% of an organic acid mixture, 1-5% of an organic amine mixture, 6-15% of a thixotropic agent, 2-8% of a surfactant, and the balance is rosin. The organic amine mixture is made by mixing a small molecule organic amine and an amino-terminated hyperbranched polyamide. The weight ratio of the small molecule organic amine to the amino-terminated hyperbranched polyamide is 4:(0.5-2). The organic acid mixture is a mixture of adipic acid, 2-hydroxymethylbutyric acid, and stearic acid. It has the advantages of reducing the corrosion of the substrate during welding and improving the spreading rate of the solder wire.

Description

Technical Field

[0001] The present application relates to the technical field of welding materials, and particularly relates to a lead-free and halogen-free solder wire and a preparation method thereof. Background Art

[0002] A solder wire, also known as a solder filament, tin wire, or tin filament, is composed of two parts: a tin alloy and a soldering flux. Among them, the soldering flux is generally a rosin resin-based soldering flux composed of rosin, resin, halide activator, additive aids, and an organic carrier. Although such soldering fluxes have low cost, stable performance, and good solderability, they have strong post-welding corrosion, high ion contamination, and the halogen ions in the post-welding residues are likely to cause corrosion of the surface circuits of the printed circuit board, and then gradually cause a decline in electrical insulation performance and short circuits, etc., shortening the service life of electronic products.

[0003] Currently, there are lead-free solder wire soldering fluxes prepared by compounding raw materials such as organic acids, organic amines, and compound-modified rosin resins. Among them, the organic acids are usually adipic acid, suberic acid, glutaric acid, glutaric anhydride, myristic acid, lauric acid, malic acid, etc., and the organic amines include diethanolamine, triethanolamine, etc. Excessive organic acids will cause relatively high corrosion of the base material. Therefore, organic amines not only act as activators but also can neutralize with organic acids and acidic residues after welding to reduce the corrosiveness of the soldering flux. However, when the addition amount of organic amines reaches a certain level, it is easy to undergo a neutralization reaction with organic acids, and some of the neutralization products do not decompose into the original reactants during the welding process, resulting in insufficient activation and limited spread rate of the solder wire. Summary of the Invention

[0004] In order to reduce the corrosion of the base material during welding and improve the spread rate of the solder wire, the present application provides a lead-free and halogen-free solder wire and a preparation method thereof.

[0005] In a first aspect, the present application provides a lead-free and halogen-free solder wire, adopting the following technical solution:

[0006] A lead-free and halogen-free solder wire is prepared from a tin alloy and a soldering flux. The weight percentage content of the added soldering flux is 4 - 7%, and the soldering flux is prepared from the following raw materials in weight percentage content: 2 - 5% of an organic acid mixture, 1 - 5% of an organic amine mixture, 6 - 15% of a thixotropic agent, 2 - 8% of a surfactant, and the balance is rosin;

[0007] The organic amine mixture is made by mixing a small molecule organic amine and a terminal amino hyperbranched polyamide, and the weight ratio of the small molecule organic amine to the terminal amino hyperbranched polyamide is 4:(0.5 - 2);

[0008] The organic acid mixture is a mixture of adipic acid, 2-hydroxymethylbutyric acid, and stearic acid.

[0009] By adopting the above technical solution, the amino-terminated hyperbranched polyamide is a hyperbranched polymer, belonging to highly branched three-dimensional macromolecules. Hyperbranched polymers have many branching points and abundant terminal functional groups; their molecular chains are not easily entangled, and the viscosity does not change with the increase in molecular weight; they have excellent fluidity and film-forming properties. When the amino-terminated hyperbranched polyamide is applied to the flux, a large number of terminal amino functional groups are contained in its molecular structure. On the one hand, it can play an activation role as an organic amine activator. On the other hand, its reactive groups and reactivity are stronger, and it reacts with organic acids preferentially more than small-molecule organic amines. The neutralization product does not decompose into the original products during the soldering process, and its molecular structure still has active groups, and the neutralization product still has the role of an activator, thereby alleviating the problems of reduced activation and reduced solder wire expansion rate caused by the neutralization reaction of organic acids and organic amines. And its reaction with organic acids can reduce the corrosion of the substrate. In addition, the addition of the amino-terminated hyperbranched polyamide can slow down the flow rate of the flux, making the flow rate of the flux adapt to that of the tin alloy, and can push the rosin to float on the surface of the tin alloy. After soldering is completed, the rosin can wrap the solder joints, which can increase the antioxidant property of the solder joints. And after the amino-terminated hyperbranched polyamide moves to the surface of the tin alloy along with the rosin, it plays a role in film-forming and curing, making the antioxidant film formed on the surface of the solder joints more complete, further improving the antioxidant property of the tin alloy, and the anti-corrosion performance of the subsequent copper plate corrosion test is also better.

[0010] Preferably: the weight ratio of the small-molecule organic amine to the amino-terminated hyperbranched polyamide is 4:1.

[0011] By adopting the above technical solution, if the addition amount of the amino-terminated hyperbranched polyamide is too large, its reactivity is relatively high, and there are too many reactions with small-molecule acids, resulting in a decrease in the activation performance of the flux. When the weight ratio of diethanolamine to the amino-terminated hyperbranched polyamide added is 4:1, the synergistic effect between the two substances is optimal.

[0012] Preferably: the molecular weight of the amino-terminated hyperbranched polyamide is 800 - 1000, and the number of amino groups per single molecule is 7 - 9.

[0013] By adopting the above technical solution, a higher molecular weight of the amino-terminated hyperbranched polyamide has a better synergistic effect with the small-molecule organic amine. When the molecular weight is lower, its synergistic effect is lower.

[0014] Preferably: the small-molecule organic amine is diethanolamine or triethanolamine.

[0015] By adopting the above technical solution, both diethanolamine and triethanolamine can have a synergistic effect with the amino-terminated hyperbranched polyamide.

[0016] Preferably, the organic acid mixture is a mixture of adipic acid, 2-hydroxymethylbutyric acid, and stearic acid, and the added weight ratio is 2:1:(0.5 - 4).

[0017] By adopting the above technical solution, when adipic acid, 2-hydroxymethylbutyric acid, and stearic acid are added in this proportion range, the activation effect is relatively good.

[0018] Preferably, the thixotropic agent is one or more of hydrogenated castor oil, ethylene bis-stearamide, and polyethylene wax.

[0019] By adopting the above technical solution, any type of thixotropic agent within this range can be added.

[0020] Preferably, the surfactant is one or more of rosin alcohol ether surfactant, Tween - 30, AEO - 9, and NP - 9.

[0021] By adopting the above technical solution, the surfactant can make the compatibility between various substances in the soldering flux better.

[0022] Preferably, the rosin is one or two of hydrogenated rosin and hydrogenated acrylic acid modified rosin.

[0023] Preferably, the tin alloy is a tin - copper alloy or a tin - silver - copper alloy.

[0024] By adopting the above technical solution, the soldering flux of the present application is applicable to both tin - copper and tin - silver - copper alloys.

[0025] Second, the present application provides a preparation method of a lead - free and halogen - free soldering wire, adopting the following technical solution:

[0026] A preparation method of a lead - free and halogen - free soldering wire, which includes the following steps:

[0027] S1. According to the dosage in Table 1, heat the rosin to 130 - 150 °C and stir to melt it, then add the organic acid mixture, stir until completely melted, then add the organic amine mixture, stir until completely dissolved, and finally add the surfactant and thixotropic agent, and continue to stir to obtain the soldering flux, and cool it to 120 - 140 °C for heat preservation for later use;

[0028] S2. Melt the tin alloy and cast it into a hollow concentric cylindrical ingot, and solidify it after cooling;

[0029] S3. Pour the soldering flux heat - preserved in S1 into the concentric cylindrical ingot prepared in S2 and fill it up, and after cooling, obtain the lead - free and halogen - free soldering wire through extrusion, rolling, drawing, and wire winding.

[0030] By adopting the above technical solution, the preparation method of the present application has no special requirements for equipment, is suitable for large-scale production in factories, has a wide range of required technical parameters, and has a high production qualification rate.

[0031] In summary, the present application includes at least one of the following beneficial technical effects:

[0032] 1. The terminal amino hyperbranched polyamide is applied to the flux. Its molecular structure contains a large number of terminal amino functional groups. On the one hand, it can act as an organic amine activator to play an activation role. On the other hand, its reactive groups and reactivity are stronger, and it reacts with organic acids more preferentially than small molecule organic amines. The neutralization product does not decompose into the original product during the soldering process, and its molecular structure still has active groups, and the neutralization product still has the role of an activator, so as to alleviate the problems of reduced activation and reduced solder wire expansion rate caused by the neutralization reaction of organic acids and organic amines. And its reaction with organic acids can reduce the corrosion of the substrate. In addition, the addition of terminal amino hyperbranched polyamide can slow down the flow rate of the flux, make the flow rate of the flux adapt to that of the tin alloy, and can push the rosin to float on the surface of the tin alloy. After soldering is completed, the rosin can wrap the solder joints, which can increase the oxidation resistance of the solder joints. And after the terminal amino hyperbranched polyamide moves to the surface of the tin alloy with the rosin, it plays a film-forming and curing role, making the antioxidant film formed on the surface of the solder joints more complete, further improving the oxidation resistance of the tin alloy, and the anti-corrosion performance of the subsequent copper plate corrosion test is also better.

[0033] 2. The lead-free and halogen-free solder wire prepared by the present application can reach an expansion rate of 88.1% under excellent anti-splash performance and copper plate corrosion resistance. Specific Embodiments

[0034] The following further elaborates on the present application in conjunction with specific content.

[0035] Raw Materials

[0036] The raw materials used in the embodiments of the present application can all be purchased commercially; among them, the NOC (120°C ± 2h) content of the terminal amino hyperbranched polyamide is <3.0%; the effective ingredient content of the polyethylene wax is 99%; the rosin alcohol ether surfactant is of superior grade, and the effective ingredient content is 99%; the grade of the hydrogenated rosin is industrial grade; the grade of the hydrogenated acrylic acid modified rosin is industrial grade.

[0037] Examples

[0038] Example 1

[0039] A lead-free and halogen-free solder wire is made of a tin alloy and a flux. The tin alloy is Sn-0.7Cu, the weight percentage of the added flux is 5%, the raw materials of the flux and the dosage of each raw material are shown in Table 1, and the preparation method of the solder wire is as follows:

[0040] S1. Heat the rosin to 140°C and stir until melted according to the dosages in Table 1. Then add the organic acid mixture and stir until completely melted. Next, add the organic amine mixture and stir until completely dissolved. Finally, add the surfactant and thixotropic agent, and continue stirring for 30 min to obtain the soldering flux. Cool it to 140°C and keep it warm for use.

[0041] S2. Melt Sn - 0.7Cu and cast it into a hollow concentric cylindrical ingot. Cool it to 25°C and solidify.

[0042] S3. Pour the soldering flux kept warm in S1 into the concentric cylindrical ingot prepared in S2 and fill it up. After cooling to 25°C, make the lead - free and halogen - free solder wire through extrusion, rolling, wire drawing, and wire winding.

[0043] Among them, the organic acid mixture is a mixture of adipic acid, 2 - hydroxymethylbutyric acid, and stearic acid, and the added weight ratio is 2:1:2; the organic amine mixture is a mixture of diethanolamine and terminal amino - hyperbranched polyamide, and the added weight ratio is 4:1; the thixotropic agent is polyethylene wax; the surfactant is rosin alcohol ether surfactant, and the added weight ratio is 1:1; the rosin is a mixture of hydrogenated rosin and hydrogenated acrylic acid - modified rosin, and the added weight ratio is 2:1; the relative molecular weight of the terminal amino - hyperbranched polyamide is 800 - 1000, and the number of amino groups per single molecule is 7 - 9.

[0044] Table 1 Raw materials and dosages (kg) of the soldering flux in Example 1

[0045] Organic acid mixture 4 Organic amine mixture 4 Thixotropic agent 10 Surfactant 5 Rosin 77

[0046] Example 2

[0047] A lead - free and halogen - free solder wire, which is different from Example 1 in that in its organic amine mixture, the mixture of diethanolamine and terminal amino - hyperbranched polyamide has an added weight ratio of 4:0.5, and the remaining steps are the same as those in Example 1.

[0048] Example 3

[0049] A lead - free and halogen - free solder wire, which is different from Example 1 in that in its organic amine mixture, the mixture of diethanolamine and terminal amino - hyperbranched polyamide has an added weight ratio of 4:2, and the remaining steps are the same as those in Example 1.

[0050] Example 4

[0051] A lead - free and halogen - free solder wire, which is different from Example 1 in that in its organic amine mixture, diethanolamine is replaced with triethanolamine of equal weight, and the remaining steps are the same as those in Example 1.

[0052] Example 5

[0053] A lead - free and halogen - free solder wire, different from that of Example 1, in its organic acid mixture, the weight ratio of adipic acid, 2 - hydroxymethylbutyric acid, and stearic acid added is 2:1:4, and the remaining steps are the same as those of Example 1.

[0054] Example 6

[0055] A lead - free and halogen - free solder wire, different from that of Example 1, in its organic acid mixture, the weight ratio of adipic acid, 2 - hydroxymethylbutyric acid, and stearic acid added is 2:1:0.5, and the remaining steps are the same as those of Example 1.

[0056] Example 7

[0057] A lead - free and halogen - free solder wire, different from that of Example 1, its tin alloy is Sn - 1.0Ag - 0.5Cu, and the remaining steps are the same as those of Example 1.

[0058] Comparative Example

[0059] Comparative Example 1

[0060] A lead - free and halogen - free solder wire, different from that of Example 1, in its organic amine mixture, terminal amino - hyperbranched polyamide is not added, and the remaining steps are the same as those of Example 1.

[0061] Comparative Example 2

[0062] A lead - free and halogen - free solder wire, different from that of Example 1, in its organic amine mixture, diethanolamine is not added, and the remaining steps are the same as those of Example 1.

[0063] Comparative Example 3

[0064] A lead - free and halogen - free solder wire, different from that of Example 1, in its organic amine mixture, the relative molecular weight of the added terminal amino - hyperbranched polyamide is 350 - 370, and the number of amino groups per molecule is 3 - 4, and the remaining steps are the same as those of Example 1.

[0065] Comparative Example 4

[0066] A lead - free and halogen - free solder wire, different from that of Example 1, in its organic acid mixture, stearic acid is not added, and the remaining steps are the same as those of Example 1.

[0067] Performance Detection Test

[0068] Detection Method / Test Method

[0069] Lead-free and halogen-free solder wires were prepared according to the preparation methods of Examples 1-7 and Comparative Examples 1-4, and then tested according to the following testing method. The test results are shown in Table 2.

[0070] Anti-splash level: refer to the test method in SJ / T11389-2009 for testing. The lower the level, the better the anti-splash effect;

[0071] Expansion rate: refer to the test method in SJ / T11390-2009 for testing;

[0072] Copper plate corrosion: Corrosion refers to the chemical reaction between copper, solder and flux residues when the solder joint is exposed to 40℃ and 93%RH environment after welding. The copper plate corrosion experiment can examine the corrosion of flux residues after welding. Its judgment standard refers to IPC TM-6502.6.15C.

[0073] Table 2 Test results of Examples 1-7 and Comparative Examples 1-4

[0074] Anti-splash grade (level) Expansion rate (%) Copper plate corrosion Example 1 1 88.1 None Example 2 1 85.3 Slight corrosion Example 3 1 87.9 None Example 4 1 88.0 None Example 5 1 87.5 None Example 6 1 85.6 None Example 7 1 87.8 None Comparative example 1 1 80.2 Moderate corrosion Comparative example 2 2 74.7 None Comparative example 3 1 76.4 Slight corrosion Comparative example 4 1 84.9 None

[0075] It can be seen from Examples 1-7 and Comparative Examples 1-4, as well as the test data in Table 2, that the lead-free and halogen-free solder wire prepared in the present application has excellent anti-spatter performance and copper plate corrosion resistance, and its expansion rate can reach 88.1%.

[0076] The amino-terminated hyperbranched polyamide is a hyperbranched polymer, which belongs to a highly branched three-dimensional macromolecule. The hyperbranched polymer has many branching points and rich terminal functional groups; its molecular chain is not easy to entangle, and the viscosity does not change with the increase of molecular weight, which is different from linear macromolecules; it has excellent fluidity and film-forming properties. Based on its structural and performance advantages, it has been used as a new functional material, such as a cross-linking agent, a nonlinear optical material, and a high-spin organic macromolecule, and shows good effects. The present application applies the amino-terminated hyperbranched polyamide to the soldering flux, and its molecular structure contains a large number of terminal amino functional groups. On the one hand, it can play a role as an organic amine active agent, and on the other hand, it is assumed that even if it undergoes a neutralization reaction with a small molecule organic acid, the neutralization product is not decomposed into the original product during the re-welding process, and its molecular structure still has an active group, and the neutralization product still has the function of an active agent, thereby alleviating the problem of reduced activation and reduced solder wire expansion rate caused by the neutralization reaction of organic acid and organic amine. And its reaction with organic acid can reduce corrosion to the substrate.

[0077] From the detection data of Example 1 and Comparative Examples 1-2, it can be seen that adding a certain amount of terminal amino hyperbranched polyamide to the flux can significantly improve the spreading rate of the solder wire. However, from the detection data of Comparative Examples 1-2, the activation performance of the terminal amino hyperbranched polyamide is not as good as that of small molecule organic amines. Therefore, it needs to be compounded with small molecule organic amines to achieve better comprehensive effects.

[0078] If the addition amount of the terminal amino hyperbranched polyamide is too large, its reaction activity is relatively high, and there are too many reactions with small molecule acids, resulting in a decrease in the activation performance of the flux. Combining Examples 2-3, when the weight ratio of diethanolamine to terminal amino hyperbranched polyamide added is 4:1, the synergistic effect between the two substances is optimal.

[0079] In addition, experiments have found that the addition of terminal amino hyperbranched polyamide can slow down the flow rate of the flux, making the flow rate of the flux adapt to that of the tin alloy, and can push the rosin to float on the surface of the tin alloy. After welding is completed, the rosin can wrap the solder joints, which can increase the oxidation resistance of the solder joints. Moreover, after the terminal amino hyperbranched polyamide moves to the surface of the tin alloy along with the rosin, it plays a role in film formation and curing, making the antioxidant film formed on the surface of the solder joints more complete, further improving the oxidation resistance of the tin alloy, and the anti-corrosion performance in subsequent copper plate corrosion detection is also better.

[0080] From the detection data of Example 1 and Comparative Example 3, it can be seen that a higher molecular weight terminal amino hyperbranched polyamide and small molecule organic amines have a better synergistic effect. Combining the detection data of Example 4, small molecule organic amines such as diethanolamine or triethanolamine can be used for synergy.

[0081] From the detection data of Example 1, Examples 5-6, and Comparative Example 4, it can be seen that when the ratio of adipic acid and 2-hydroxymethylbutyric acid in the organic acid mixture of this application is fixed, the addition ratio of stearic acid has a greater impact on the spreading rate of the solder wire. The optimal addition ratio is that the weight ratio of adipic acid, 2-hydroxymethylbutyric acid, and stearic acid added is 2:1:2.

[0082] From the detection data of Example 1 and Example 7, it can be seen that the flux of this application is applicable to both tin-copper and tin-silver-copper alloys.

[0083] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contributions according to their needs after reading this specification, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A lead-free and halogen-free solder wire, characterized in that: It is prepared from tin alloy and soldering flux, the soldering flux is added in an amount of 4-7% by weight, and the soldering flux is prepared from the following raw materials in an amount of: 2-5% organic acid mixture, 1-5% organic amine mixture, 6-15% thixotropic agent, 2-8% surfactant, and the balance is rosin; The organic amine mixture is prepared by mixing a small molecule organic amine and an amino-terminated hyperbranched polyamide, wherein the weight ratio of the small molecule organic amine to the amino-terminated hyperbranched polyamide is 4:(0.5-2); the molecular weight of the amino-terminated hyperbranched polyamide is 800-1000, and the number of amino groups contained in a single molecule is 7-9; The organic acid mixture is a mixture of adipic acid, 2-hydroxymethylbutyric acid and stearic acid.

2. The lead-free and halogen-free solder wire according to claim 1, characterized in that: The weight ratio of the small molecule organic amine to the amino-terminated hyperbranched polyamide is 4:

1.

3. The lead-free and halogen-free solder wire according to claim 1, characterized in that: The small molecule organic amine is diethanolamine or triethanolamine.

4. The lead-free and halogen-free solder wire according to claim 1, characterized in that: The organic acid mixture is a mixture of adipic acid, 2-hydroxymethylbutyric acid and stearic acid, and the weight ratio of the organic acid mixture added is 2:1:(0.5-4).

5. The lead-free and halogen-free solder wire according to claim 1, characterized in that: The thixotropic agent is one or more of hydrogenated castor oil, ethylene bisstearic acid amide and polyethylene wax.

6. The lead-free and halogen-free solder wire according to claim 1, characterized in that: The surfactant is one or more of rosin alcohol ether surfactant, Tween-30, AEO-9 and NP-9.

7. The lead-free and halogen-free solder wire according to claim 1, characterized in that: The rosin is one or both of hydrogenated rosin and hydrogenated acrylic acid modified rosin.

8. The lead-free and halogen-free solder wire according to claim 1, characterized in that: The tin alloy is a tin-copper alloy or a tin-silver-copper alloy.

9. A method for preparing the lead-free and halogen-free solder wire according to any one of claims 1 to 8, characterized in that: It includes the following steps: S1. Mix the ingredients according to the weight percentage of each raw material, heat the rosin to 130-150°C and stir to melt, then add the organic acid mixture and stir until it is completely melted, then add the organic amine mixture and stir until it is completely dissolved, finally add the surfactant and thixotropic agent and continue stirring to obtain the flux, cool it to 120-140°C and keep it warm for later use; S2, melting the tin alloy and casting it into a hollow concentric cylindrical ingot, which is then cooled and solidified; S3, pour the soldering flux kept warm in S1 into the concentric cylindrical ingot prepared in S2 and fill it up, and after cooling, produce lead-free and halogen-free solder wire through extrusion, rolling, drawing and wire winding.