Lead-free and residue-free soldering flux and preparation method thereof

Abstract

The invention provides lead-free and residue-free soldering flux and a preparation method thereof, and relates to the technical field of soldering flux. The preparation method comprises the following steps: mixing 0.8 to 10 parts of dehydrated malic acid resin, 2 to 6 parts of ethylene bis stearamide, 0.35 to 2.8 parts of an active agent, 0.1 to 0.5 part of a corrosion inhibitor, 0.1 to 0.5 part of a coupling agent and 0.1 to 1.2 parts of a thixotropic agent; the lead-free and residue-free soldering flux is prepared by mixing the following components in parts by weight: 12-18 parts of ethylene glycol, 28-18 parts of ethyl-1, 3-hexanediol, and fully stirring to uniformly mix the components, thereby obtaining the lead-free and residue-free soldering flux. The lead-free and residue-free soldering flux can overcome the defects in the prior art, does not need hot pressing during use, is energy-saving and environment-friendly, and has the advantages of good conductivity, long-term storage and the like.

Description

Technical Field

[0001] This invention relates to the field of flux technology, and more specifically, to a lead-free, residue-free flux and its preparation method. Background Technology

[0002] For nearly a century, flux has been used in the soldering process of electronic product manufacturing. Flux is a chemical substance that helps and promotes the soldering process, while also providing protection and preventing oxidation. Flux is an auxiliary material that ensures the smooth progress of the soldering process. Its main function is to remove oxides from the surface of the solder and the base material being soldered, achieving the necessary cleanliness of the metal surface. It prevents re-oxidation of the surface during soldering, reduces the surface tension of the solder, and improves soldering performance. The quality of the flux directly affects the quality of the electronic products.

[0003] Existing fluxes tend to leave residues on the surface of electronic components after use, resulting in poor performance. Specifically, existing fluxes lead to poor electrical connection characteristics at solder joints, and the residues reduce conductivity, current carrying capacity, and temperature resistance, making them prone to desoldering. Furthermore, when combined with lead-free soldering metals, rosin or lead-free solder paste residues are easily left behind, which can further contribute to the failure of components soldered at high temperatures and humidity. After soldering, cleaning the solder joints produces metal salts, which readily corrode the circuit board. Therefore, this invention proposes a lead-free, residue-free flux to at least partially solve the problems that exist in the prior art. Summary of the Invention

[0004] The purpose of this invention is to provide a lead-free and residue-free flux and its preparation method, which can provide a solution to the shortcomings of the prior art and at least partially solve the problems that may exist in the prior art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A lead-free, residue-free flux comprising, by weight:

[0007] 0.8–10 parts of dehydrated malic acid resin;

[0008] 2-6 parts of ethylene bis-stearamide;

[0009] Surfactant: 0.35–2.8 parts;

[0010] Corrosion inhibitor 0.1-0.5 parts;

[0011] 0.1 to 0.5 parts of coupling agent;

[0012] Thixotropic agent 0.1–1.2 parts;

[0013] Ethyl-1,3-hexanediol 2.8 to 18 parts.

[0014] Optionally, the dehydrated malic acid resin is 4 to 8 parts.

[0015] Optionally, the ethylene bis-stearamide is in the form of 4 parts.

[0016] Optionally, the activator includes sebacic acid and triethylamine, wherein the ratio of sebacic acid to triethylamine is 6:1.

[0017] Optionally, the corrosion inhibitor is benzotriazole.

[0018] Optionally, the coupling agent is a silane coupling agent KH560, comprising o-hydroxybenzoic acid and propyltrimethoxysilane; the coupling agent component is 0.5 parts.

[0019] Optionally, the thixotropic agent is glyceryl stearate, and its component is 0.5 parts.

[0020] Optionally, the 2.8-18 component of the ethyl-1,3-hexanediol is 8.8 parts.

[0021] A method for preparing a lead-free and residue-free flux, comprising:

[0022] 0.8–10 parts of dehydrated malic acid resin, 2–6 parts of ethylene bis-stearamide, 0.35–2.8 parts of activator, 0.1–0.5 parts of corrosion inhibitor, 0.1–0.5 parts of coupling agent, 0.1–1.2 parts of thixotropic agent, and 2.8–18 parts of ethyl-1,3-hexanediol are mixed and stirred thoroughly to obtain the lead-free and residue-free flux.

[0023] A method for preparing a lead-free and residue-free flux includes: mixing 0.8-10 parts of dehydrated malic acid resin, 2-6 parts of ethylene bis-stearamide, 0.3-2.1 parts of sebacic acid, 0.05-0.3 parts of triethylamine, 0.1-0.5 parts of benzotriazole, 0.1-0.5 parts of silane coupling agent KH560, 0.1-1.2 parts of glyceryl stearate, and 2.8-18 parts of ethyl-1,3-hexanediol, and heating to 80°C while stirring thoroughly to ensure uniform mixing, thereby obtaining the lead-free and residue-free flux.

[0024] The present invention has at least the following advantages or beneficial effects:

[0025] The lead-free, residue-free flux is prepared by mixing 0.8–10 parts of dehydrated malic acid resin, 2–6 parts of ethylene bis-stearamide, 0.35–2.8 parts of activator, 0.1–0.5 parts of corrosion inhibitor, 0.1–0.5 parts of coupling agent, 0.1–1.2 parts of thixotropic agent, and 2.8–18 parts of ethyl-1,3-hexanediol, and stirring thoroughly to ensure uniform mixing. Using a lead-free, residue-free flux overcomes the shortcomings of existing technologies, eliminates the need for hot pressing during use, saves energy and is environmentally friendly, and also possesses good electrical conductivity and long-term storage capabilities. Detailed Implementation

[0026] To make the objectives, features, and advantages of this invention more apparent and understandable, the invention will be further described in detail below with reference to specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0027] In one embodiment of this application, a lead-free, residue-free flux comprises, by weight:

[0028] 0.8–10 parts of dehydrated malic acid resin;

[0029] 2-6 parts of ethylene bis-stearamide;

[0030] Surfactant: 0.35–2.8 parts;

[0031] Corrosion inhibitor 0.1-0.5 parts;

[0032] 0.1 to 0.5 parts of coupling agent;

[0033] Thixotropic agent 0.1–1.2 parts;

[0034] Ethyl-1,3-hexanediol 2.8 to 18 parts.

[0035] In this embodiment, the aforementioned lead-free and residue-free flux solves a series of problems caused by existing flux residues. The flux of this invention, which leaves virtually no residue after soldering lead-free alloy metals, can keep the surface of electronic components clean, effectively improve soldering ability, ensure the effectiveness of soldering results, and enable the surface of electronic products to achieve the necessary cleanliness. Specifically, the excellent electrical connection characteristics of lead-free alloys after soldering are improved, with high reliability, improved current resistance, and improved temperature resistance. It can be used with various lead-free soldering metals, and there is no rosin residue after soldering. It breaks through the traditional lead-free solder paste residue after soldering, which leads to failure of components soldered in high temperature and high humidity. It also breaks through the traditional lead-free solder paste residue cleaning after soldering, with no metal salt generation, effectively ensuring the service life of components and improving the cost and quality of manufacturing enterprises. The lead-free flux of this invention can be used in combination with other lead-free solders such as SAC305 alloy and SnSb alloy without any other adverse reactions.

[0036] In one embodiment of this application, the amount of dehydrated malic acid resin is 4 to 8 parts, and 5 parts, 5.2 parts, or 6 parts are preferred as a more favorable ratio. Dehydrated malic acid resin is a polymer resin, also known as dehydrated malic acid ester resin. It can remain stable under high temperature conditions, has high thermal stability, and can produce good adhesion and adjustability to various substrate surfaces.

[0037] In one embodiment of this application, the amount of ethylene bis-stearamide is 4 parts. Since the ethylene bis-stearamide (EBS) molecule has polar amide groups, EBS has a processing lubricating effect and a low-temperature anti-sticking effect on polymer resin. EBS can be inserted into the polymer resin to reduce the interaction between resin molecules and play the role of internal lubricant. On the other hand, EBS can prevent it from adhering to the metal surface due to the mutual friction between processing equipment in the resin melt, thus playing the role of external lubricant.

[0038] In one embodiment of this application, the surfactant comprises sebacic acid and triethylamine, wherein the ratio of sebacic acid to triethylamine is 6:1. For example, in this application, 0.6 parts sebacic acid and 0.1 parts triethylamine are preferred. Using sebacic acid and triethylamine as surfactants provides excellent surface wettability, while triethylamine can adjust the viscosity and drying speed of the coating, thereby achieving better coating effect and durability, ensuring optimal results and avoiding adverse reactions or negative impacts.

[0039] In one embodiment of this application, the corrosion inhibitor is benzotriazole, preferably 0.2 parts. A corrosion inhibitor is a substance commonly used to prevent metal corrosion; it can chemically react with the metal surface to form a protective film. This film can isolate the metal from contact with the external environment, preventing corrosive media from eroding the metal; it can also change the electrochemical reaction rate on the metal electrode, inhibiting the anodic and cathodic reactions of the metal, thus slowing down the metal corrosion process. Furthermore, the corrosion inhibitor can adjust the pH value of the environment, reducing the erosion of the metal by corrosive media.

[0040] In one embodiment of this application, the coupling agent is a silane coupling agent KH560, comprising o-hydroxybenzoic acid and propyltrimethoxysilane; the coupling agent component is 0.5 parts; the thixotropic agent is glyceryl stearate, its component is 0.5 parts; and the ethyl-1,3-hexanediol 2.8-18 component is 8.8 parts.

[0041] It should be noted that a thixotropic agent is a substance added to certain materials to change their rheological properties, causing the material to exhibit liquid characteristics under external force and quickly return to a solid state after the external force is removed.

[0042] As an example, a suitable alternative to the aforementioned lead-free, residue-free flux, after being mixed with lead-free alloy metal, using formic acid reflow for soldering at lower temperatures, is solder reflow under formic acid (HCOOH) vapor. The vapor reacts chemically with metal oxides at lower temperatures (150°C–160°C) to form a matrix; increasing the temperature further decomposes the matrix into hydrogen, water, and carbon dioxide. When used in conjunction with a vacuum reflow soldering system, these gases and vapors can be removed by a vacuum system. After two vacuum stages using nitrogen refilling, there is no atmosphere or oxygen in the chamber. The temperature is increased with the introduction of formic acid vapor (nitrogen acts as a carrier for the formic acid vapor) and held at 160°C, further increased to 220°C and held to provide time for solder reflow and oxide removal. The chamber is then purged with nitrogen and evacuated using a vacuum stage to remove any voids.

[0043] It should be noted that formic acid reflow soldering is a proven fluxless soldering method. Because the oxide removal properties of formic acid vapor are effective at lower temperatures, it is also a very flexible process. It eliminates the need for pre-reflow and post-reflow flux removal. Furthermore, due to the corrosiveness of formic acid, it leaves exposed metal surfaces suitable for further diffusion processes, such as wire bonding.

[0044] In one embodiment of this application, a method for preparing a lead-free and residue-free flux is also disclosed, comprising: mixing 0.8 to 10 parts of dehydrated malic acid resin, 2 to 6 parts of ethylene bis-stearamide, 0.35 to 2.8 parts of activator, 0.1 to 0.5 parts of corrosion inhibitor, 0.1 to 0.5 parts of coupling agent, 0.1 to 1.2 parts of thixotropic agent, and 2.8 to 18 parts of ethyl-1,3-hexanediol, and stirring thoroughly to ensure uniform mixing, thereby obtaining the lead-free and residue-free flux.

[0045] In one embodiment of this application, a method for preparing a lead-free and residue-free flux is also disclosed, comprising: mixing 0.8-10 parts of dehydrated malic acid resin, 2-6 parts of ethylene bis-stearamide, 0.3-2.1 parts of sebacic acid, 0.05-0.3 parts of triethylamine, 0.1-0.5 parts of benzotriazole, 0.1-0.5 parts of silane coupling agent KH560, 0.1-1.2 parts of glyceryl stearate, and 2.8-18 parts of ethyl-1,3-hexanediol, and heating to 80°C and stirring thoroughly to ensure uniform mixing, thereby obtaining the lead-free and residue-free flux.

[0046] In a specific example, it is preferable to mix 5.2 parts by weight of dehydrated malic acid resin, 4 parts by weight of ethylene bis-stearamide, 0.2 parts by weight of benzotriazole, 0.6 parts by weight of sebacic acid, 0.2 parts by weight of o-hydroxybenzoic acid or γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 0.1 parts by weight of triethylamine, 0.5 parts by weight of glyceryl stearate, and 8.8 parts by weight of 2-ethyl-1,3-hexanediol, and stir the mixture until homogeneous to obtain the lead-free and residue-free flux described above. This can be ensured by heating to 80°C and maintaining a constant temperature. Heating can improve the solubility of the solute in the solvent. Stirring the mixture can also improve the contact between the solute and the solvent, accelerate the dissolution process, and improve the uniformity and stability of the mixture.

[0047] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0048] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0049] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0050] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0051] The foregoing has provided a detailed description of the lead-free and residue-free flux and its preparation method provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A lead-free residue-free flux, characterized by, Including components by weight: 0.8–10 parts of dehydrated malic acid resin; 2-6 parts of ethylene bis-stearamide; Surfactant: 0.35–2.8 parts; Corrosion inhibitor 0.1-0.5 parts; 0.1 to 0.5 parts of coupling agent; Thixotropic agent 0.1–1.2 parts; Ethyl-1,3-hexanediol 2.8 to 18 parts.

2. The lead-free, residue-free flux according to claim 1, wherein, The amount of the dehydrated malic acid resin is 4 to 8 parts.

3. The lead-free, residue-free flux according to claim 1, wherein, The amount of ethylene bis-stearamide is 4 parts.

4. The lead-free, residue-free flux according to claim 1, wherein, The active agent includes sebacic acid and triethylamine, wherein the ratio of sebacic acid to triethylamine is 6:

1.

5. The lead-free, residue-free flux according to claim 1, wherein, The corrosion inhibitor is benzotriazole.

6. The lead-free, residue-free flux according to claim 1, wherein, The coupling agent is a silane coupling agent KH560, comprising o-hydroxybenzoic acid and propyltrimethoxysilane; the coupling agent component is 0.5 parts.

7. The lead-free, residue-free flux according to claim 1, wherein The thixotropic agent is glyceryl stearate, and its component is 0.5 parts.

8. The lead-free, residue-free flux according to claim 1, wherein, The ethyl-1,3-hexanediol 2.8-18 component comprises 8.8 parts.

9. A method of producing a lead-free and residue flux-free solder, characterized by, include: 0.8–10 parts of dehydrated malic acid resin, 2–6 parts of ethylene bis-stearamide, 0.35–2.8 parts of activator, 0.1–0.5 parts of corrosion inhibitor, 0.1–0.5 parts of coupling agent, 0.1–1.2 parts of thixotropic agent, and 2.8–18 parts of ethyl-1,3-hexanediol are mixed and stirred thoroughly to obtain the lead-free and residue-free flux.

10. A method of producing a lead-free and residue-free flux, characterized by, 0.8–10 parts of dehydrated malic acid resin, 2–6 parts of ethylene bis-stearamide, 0.3–2.1 parts of sebacic acid, 0.05–0.3 parts of triethylamine, 0.1–0.5 parts of benzotriazole, 0.1–0.5 parts of silane coupling agent KH560, 0.1–1.2 parts of glyceryl stearate, and 2.8–18 parts of ethyl-1,3-hexanediol are mixed and heated to 80°C and stirred thoroughly to ensure uniform mixing, thus obtaining the lead-free and residue-free flux.