A high flowability solder resist for multi-process adaptation and a preparation method thereof

Abstract

The present application relates to a kind of high flowability solder stop agent for multi-process adaptation and its preparation method.High viscosity yttria solder stop agent, paste, poor flowability, after dilution with glycol ethyl ether acetate, although viscosity is suitable for brushing, but when brush coating, due to low viscosity, yttria particles in solder stop agent are easy to settle and flow, leading to uneven coating thickness and leaving brush marks.To solve this problem, 1-3wt% of flaky boron nitride powder and 0.5wt% of alkaline polyester dispersant are added to the diluted solder stop agent.The three-dimensional network (a weak three-dimensional network) of reversible card house structure formed by boron nitride sheet in solder stop agent, easy to flow under high shear, easy to conform under low shear, improve the rheological property of solder stop agent, so that its rheological index is in the following range: viscosity is 0.5-2Pas at shear rate 100s ‑1 ; thixotropic index is 3-8; yield value: 10-40 Pa, flow time is about 60s.

Description

Technical Field

[0001] This invention relates to the field of metal superplastic forming / diffusion welding technology, and in particular to a high-flowability anti-weld flux adaptable to multiple processes and its preparation method. Background Technology

[0002] Superplastic forming / diffusion bonding (SPF / DB) composite technology is an important metal processing technology. The process involves coating areas that do not require welding with a layer of solder resist to form a solder resist pattern. In areas without solder resist, the metal plates are in contact, and diffusion bonding is achieved through atomic migration under high temperature and pressure.

[0003] For creating solder resist patterns on irregularly shaped curved metal surfaces, a film coating method is typically used. This involves applying a plastic film to the areas where solder resist is not needed, then spraying or brushing on the resist. After drying, the plastic film is removed, revealing the solder resist pattern on the curved surface. Existing diffusion welding machines use a paste-like resist formed by dispersing yttrium oxide in an organic carrier. This paste has high viscosity, making it difficult to apply evenly to curved metal plates, thus affecting the welding quality.

[0004] If a thinner is added to the existing solder resist, the viscosity can be adjusted to a shear rate of 100s. -1 At that time, the viscosity was 0.5-2 Pa. s. Within this viscosity range, the solder resist can be applied with a brush, but after brushing on curved surfaces, the yttrium oxide particles flow under gravity, i.e., sagging, resulting in uneven thickness of the prepared solder resist coating, brush marks on the surface, and failure to level out over a long period of time, resulting in uneven thickness, severe powder shedding, and also affecting the diffusion quality of the product. Summary of the Invention

[0005] This invention provides a high-flowability solder resist adaptable to multiple processes and its preparation method. It can be used not only for manual brush application but also for filling and spraying, solving the problems of sedimentation after dilution of existing paste-like solder resists, as well as uneven coating thickness and powdering caused by the downward flow of the solder resist after brushing on curved workpieces.

[0006] In a first aspect, the present invention provides a method for preparing a high-flowability solder stop agent adaptable to multiple processes, comprising: Add 1-3 wt% boron nitride flakes and 0.5 wt% alkaline polyester dispersant to the diluted solder resist; Boron nitride sheets are used to form a reversible, three-dimensional network of capillary structures in the solder resist, which facilitates flow under high shear and maintains shape under low shear, thus improving the rheological properties of the solder resist and achieving rheological parameters within the following range: at a shear rate of 100 s⁻¹... -1 The viscosity is 0.5-2 Pa. s; thixotropic index of 3-8; yield value of 10-40 Pa; leveling time of 60 s.

[0007] Furthermore, the anti-welding agent is a high-viscosity yttrium oxide anti-welding agent.

[0008] Furthermore, the anti-welding agent is diluted with ethylene glycol ethyl ether acetate.

[0009] Furthermore, the content of the ethylene glycol ethyl ether acetate is 10-15 wt%.

[0010] Furthermore, the boron nitride sheet is a hexagonal boron nitride nanosheet.

[0011] Furthermore, the boron nitride sheet has a length and width of 100-500 nm and a thickness of 5-20 nm.

[0012] Secondly, the present invention provides a high-flowability solder stop agent adaptable to multiple processes, which is obtained by the preparation method of the high-flowability solder stop agent adaptable to multiple processes as described above.

[0013] Furthermore, the solder resist agent is used to apply solder resist agent to the metal surface by brushing. The coating after brushing is free of drips and brush marks, and has a uniform thickness.

[0014] The above-described technical solution of the present invention has the following advantages: This invention provides a high-flowability solder stop agent adaptable to multiple processes and its preparation method. By adding 1-3 wt% boron nitride flakes and 0.5 wt% alkaline polyester dispersant to the diluted solder stop agent, the boron nitride flakes form a reversible, three-dimensional network with a cardioid structure within the solder stop agent. This improves the rheological properties of the solder stop agent, allowing it to flow easily under high shear and maintain its shape under low shear, resulting in a viscosity of 0.5-2 Pa at a shear rate of 100 s⁻¹. With a thixotropic index of 3-8, a yield value of 10-40 Pa, and a leveling time of 60 s, it can be used not only for manual brush coating but also for spray coating. It solves the problems of sedimentation after dilution of existing paste-like solder resists, as well as uneven coating thickness and powdering caused by the downward flow of solder resists after brushing on curved workpieces. Attached Figure Description

[0015] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1This is a schematic diagram of the three-dimensional cardboard structure formed by the boron nitride sheet in the solder resist according to an embodiment of the present invention. Detailed Implementation

[0017] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0018] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0019] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0020] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0021] The weights of the relevant components mentioned in the embodiments of this invention can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this invention is within the scope disclosed in the embodiments of this invention. Specifically, the mass described in the embodiments of this invention can be a mass unit known in the chemical industry, such as µg, mg, g, or kg.

[0022] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. For example, without departing from the scope of embodiments of the invention, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] This invention provides a method for preparing a high-flowability solder stop agent suitable for multiple processes, comprising: adding 1-3 wt% boron nitride flakes and 0.5 wt% alkaline polyester dispersant to a diluted solder stop agent; utilizing the boron nitride flakes to form a reversible carding structure three-dimensional network in the solder stop agent, which facilitates flow under high shear and maintains shape under low shear, thereby improving the rheological properties of the solder stop agent and ensuring that its rheological properties are within the following range: at a shear rate of 100 s⁻¹... -1 The viscosity is 0.5-2 Pa. s; thixotropic index of 3-8; yield value of 10-40 Pa; leveling time of 60 s.

[0025] In some embodiments, the anti-soldering agent is a high-viscosity yttrium oxide anti-soldering agent.

[0026] In some embodiments, the anti-soldering agent is diluted with ethylene glycol ethyl ether acetate.

[0027] In some embodiments, the content of the ethylene glycol ethyl ether acetate is 10-15 wt%.

[0028] In some embodiments, the boron nitride sheet is a hexagonal boron nitride nanosheet.

[0029] In some embodiments, the boron nitride sheet has a length and width of 100-500 nm and a thickness of 5-20 nm.

[0030] This invention also provides a high-flowability solder stop agent adaptable to multiple processes, which is obtained by the preparation method of the high-flowability solder stop agent adaptable to multiple processes as described above.

[0031] In some embodiments, the anti-weld agent is used to brush an anti-weld agent onto a metal surface, and the resulting coating is free of drips, brush marks, and has a uniform thickness.

[0032] The weld arrestor is a dispersion system formed by uniformly dispersing yttrium oxide nanoparticles in an organic carrier. For metal superplastic forming / diffusion welding, the weld arrestor after baking must contain only Y₂O₃ powder and small amounts of C, H, and N. The introduction of other elements will diffuse into the titanium alloy, leading to component failure.

[0033] The core requirements for the anti-weld agent in the brush coating process are: (1) low viscosity at high shear rate; (2) no flow at low shear rate, that is, high viscosity and sufficient yield value; (3) able to level in a short time and eliminate brush marks.

[0034] Traditional inks commonly employ the following methods to prevent dripping (sag): (1) silicate-modified organic bentonite with a layered structure; (2) silane forming a hydrogen bond network on the surface of vapor-phase SiO2. These two methods introduce impurities such as Si into the release agent, which reacts with the metal substrate at high temperatures. (3) anti-sag additives with polyamide wax or polyethylene wax as the main component. These wax additives do not dissolve in the ink but are dispersed as solid particles in the solvent. Being organic components, they cannot be completely diffused during superplastic forming, affecting diffusion performance. Therefore, none of these methods can solve the problem that this invention aims to address.

[0035] Hexagonal (h-BNNS) boron nitride, with B and N atoms in the layer separated by sp... 2 The covalent bonds form a six-membered ring structure (bond length 1.45 Å), and the BN bond strength is very strong, greater than 800 kJ / mol. This is the source of boron nitride's high-temperature resistance, good high-temperature stability, high thermal conductivity, and high mechanical modulus. During the high-temperature processes of superplastic forming / diffusion welding, the B and N atoms do not break due to the strong bond, and thus diffuse into the metal material. Like yttrium oxide, boron nitride is one of the functional materials used in solder resists in metal processing.

[0036] Boron nitride has only van der Waals forces between its layers, approximately 10-20 kJ / mol. Compared to yttrium oxide, it is much easier to obtain sheet-like boron nitride nanosheets. Therefore, this invention uses two-dimensional boron nitride nanosheets to form a reversible three-dimensional cardboard structure to control the rheological properties of the solder resist, thus meeting the requirements for brushing solder resist patterns onto curved metal surfaces.

[0037] The cardioid structure, with its two-dimensional flattened shape, facilitates face-to-face or edge-to-face contact between particles in the dispersion medium, forming a spatial network of overlapping flakes. A three-dimensional network structure is formed through weak van der Waals forces between the surface and edges of the boron nitride flakes, creating reversible overlap points between the flakes. Under shear forces, it slides easily without breaking. The cardioid network structure allows for sliding under high shear, providing a smooth and effortless application during scraping. After brushing, the three-dimensional network structure retains numerous overlap points, and the three-dimensional network structure recovers under the van der Waals forces between the flake surface and the edge of another flake, preventing flux run-through and allowing for rapid viscosity recovery.

[0038] like Figure 1 The diagram shows a three-dimensional trap structure formed by boron nitride sheets in solder resist. Under high shear, the trap structure slides along the shear direction. After the shear force disappears, the trap structure still exists, and it can quickly recover due to the van der Waals forces of the interlayer and edge charges of the boron nitride sheets. This improves the thixotropy and yield value of the low-viscosity solder resist, and suppresses the sagging and brush marks of the solder resist after brushing onto curved surfaces.

[0039] In this invention, hexagonal boron nitride nanosheets with a length and width of approximately 100-500 nm and a thickness of approximately 5-20 nm are used. Through experiments, it has been found that using a polyester-based alkaline polymeric dispersant to impart a suitable negative charge to the surface of the boron nitride nanosheets, with an addition amount of 1-3 wt%, can achieve excellent results.

[0040] The thixotropic index is calculated at 25°C with a high shear rate of 100 s⁻¹. -1 (Brush coating) and low shear rate of 0.1s -1 The ratio of viscosity at rest reflects the change in viscosity with shear rate. The larger the value, the stronger the thixotropy (easier to flow at high shear and easier to maintain shape at low shear). TI < 3: Weak thixotropy, small difference between low and high shear viscosity, prone to dripping of the flux (e.g., dripping when brushing on vertical surfaces); TI = 3-8: Moderate thixotropy, suitable for most application methods such as brushing and spraying, easy to spread (low viscosity at high shear) and prevents dripping (high viscosity at low shear); TI > 8: Excessively strong thixotropy, insufficient viscosity reduction at high shear, difficult brushing, and excessively rapid viscosity recovery after resting, easily leaving brush marks. The yield value of a solder resist refers to the stress value recorded when the solder resist begins to flow noticeably under gradually increased stress at a low shear rate. It is the minimum shear force required for the solder resist to start flowing from a static state. If the yield value is too high, it will be difficult to spread; if the yield value is too low, the yttrium oxide in the solder resist will easily settle and flow downwards under gravity, resulting in uneven coating thickness.

[0041] The solvent evaporation rate needs to be synchronized with the recovery rate of the thixotropic network in the cardboard structure to avoid "curing before leveling" (brush marks remaining) or "excessive sagging" (uneven thickness). Therefore, ethylene glycol ethyl ether acetate is used as the diluent, which has a medium evaporation rate. This increases the solvent evaporation rate in the solder resist, reduces the time for yttrium oxide particles in the solder resist to flow downwards, and ensures a leveling time of 50-60 seconds.

[0042] A high-viscosity yttrium oxide solder resist suitable for screen printing was diluted with ethylene glycol ethyl ether acetate to a viscosity suitable for brush application, i.e., a shear rate of 100 s. -1 At that time, the viscosity was 0.5-2 Pa. However, it has low thixotropy, with a thixotropic index less than 3 and a yield value less than 10 Pa. After adding 1-3 wt% of flake boron nitride and polyester-based alkaline dispersant, it is ground uniformly using a three-roll mill, and the viscosity is maintained at a shear rate of 100 s⁻¹. -1 0.5-2 Pa Under the premise of s, the thixotropic index is controlled at 3-8 (achieved through the reversible network of the cardboard structure in the solder resist); yield value: 10-40 Pa, leveling time: about 60s. In this way, it is ensured that the low viscosity solder resist does not drip or leave brush marks when brushed onto curved surfaces.

[0043] The present invention will be further illustrated below with specific examples, but these examples should not be used to limit the scope of protection of the present invention.

[0044] Existing release agents for diffusion welding are paste-like substances formed by dispersing yttrium oxide in parts within an organic carrier. They have high viscosity and cannot be brushed. Adding 10-15 wt% diluent can adjust the viscosity to a shear rate of 100 s. -1 0.5-2 Pa The diluent is ethylene glycol ethyl ether acetate. Within this viscosity range, the solder resist can be applied with a brush. However, after brushing on curved surfaces, the yttrium oxide particles flow under gravity, resulting in sagging and uneven thickness of the prepared solder resist pattern, with brush marks on the surface.

[0045] Example 1 Add 15 wt% ethylene glycol ethyl ether acetate thinner to the paste-like solder resist. After thorough mixing, the shear viscosity was tested to be 0.45 Pa·s, the thixotropic index (TI) was 1.3, the yield value was 0.5 Pa, and the leveling time was greater than 300 s, meaning brush marks would appear after drying. Then, add 3.0 wt% flake boron nitride powder and 0.5 wt% polyester alkaline dispersant, and grind evenly using a three-roll mill. The viscosity was tested to be 0.98 Pa·s, the thixotropic index (TI) was 9, the yield value was 38 Pa, and the leveling time was 65 s. The brush coating effect was good.

[0046] Example 2 Add 12 wt% ethylene glycol ethyl ether acetate thinner to the paste-like solder resist. After thorough mixing, the shear viscosity was tested to be 0.68 Pa·s, the thixotropic index (TI) was 1.6, the yield value was 0.9 Pa, and the leveling time was greater than 300 s, meaning brush marks would appear after drying. Add 2.0 wt% flake boron nitride powder and 0.5 wt% polyester alkaline dispersant, and grind evenly using a three-roll mill. The viscosity was tested to be 1.08 Pa·s, the thixotropic index (TI) was 7, the yield value was 33 Pa, and the leveling time was 60 s. The brush coating effect was good.

[0047] Example 3 Add 10 wt% ethylene glycol ethyl ether acetate thinner to the paste-like solder resist. After thorough mixing, the shear viscosity was tested to be 0.78 Pa·s, the thixotropic index (TI) was 1.7, the yield value was 2.1 Pa, and the leveling time was greater than 300 s, meaning brush marks would appear after drying. Add 1.0 wt% flake boron nitride powder and 0.5 wt% polyester alkaline dispersant, and grind evenly using a three-roll mill. The viscosity was tested to be 1.5 Pa·s, the thixotropic index (TI) was 4.5, the yield value was 18 Pa, and the leveling time was 68 s. The brush coating effect was good.

[0048] Example 4 Add 13wt% ethylene glycol ethyl ether acetate thinner to the paste-like solder resist. After thorough mixing, the shear viscosity was tested to be 0.56 Pa·s, the thixotropic index (TI) was 1.4, the yield value was 3.4 Pa, and the leveling time was greater than 300 s, meaning brush marks would appear after drying. Add 1.5wt% flake boron nitride powder and 0.5wt% polyester alkaline dispersant, and grind evenly using a three-roll mill. The viscosity was tested to be 0.99 Pa·s, the thixotropic index (TI) was 6, the yield value was 18 Pa, and the leveling time was 65 s. The brush coating effect was good.

[0049] In this embodiment of the invention, a high-viscosity yttrium oxide solder resist is diluted with ethylene glycol ethyl ether acetate, and then 1-3 wt% of flake boron nitride powder and 0.5 wt% of alkaline polyester dispersant are added. The boron nitride flakes form a reversible cardioid three-dimensional network within the solder resist, improving its rheological properties and ensuring its rheological parameters are within the following range: at a shear rate of 100 s⁻¹. -1 The viscosity is 0.5-2 Pa. Thixotropic index is 3-8; yield strength is 10-40 Pa; leveling time is approximately 60 seconds. The solder resist is applied to metal surfaces by brushing, resulting in a uniform coating without sagging or brush marks. Ethylene glycol ethyl ether acetate is used as a diluent to increase the evaporation rate of the solvent in the original solder resist, achieving a synergistic effect between the solvent evaporation rate and the recovery rate of the thixotropic network in the cardboard structure, thus avoiding "curing before leveling" (brush mark residue) or "excessive sagging."

[0050] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. The present invention is not limited to the specific methods described above and shown in the figures. Furthermore, for the sake of brevity, detailed descriptions of known methods and techniques are omitted here.

[0051] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-flowability solder stop flux adaptable to multiple processes, characterized in that, include: Add 1-3 wt% boron nitride flakes and 0.5 wt% alkaline polyester dispersant to the diluted solder resist; Boron nitride sheets are used to form a reversible, three-dimensional network of capillary structures in the solder resist, which facilitates flow under high shear and maintains shape under low shear, thus improving the rheological properties of the solder resist and achieving rheological parameters within the following range: at a shear rate of 100 s⁻¹... -1 The viscosity is 0.5-2 Pa. s; thixotropic index of 3-8; yield value of 10-40 Pa; leveling time of 60 s.

2. The method for preparing a high-flowability solder resist adaptable to multiple processes as described in claim 1, characterized in that, The anti-welding agent is a high-viscosity yttrium oxide anti-welding agent.

3. The method for preparing a high-flowability solder resist adaptable to multiple processes as described in claim 1, characterized in that, The anti-welding agent is diluted with ethylene glycol ethyl ether acetate.

4. The method for preparing a high-flowability solder resist adaptable to multiple processes as described in claim 3, characterized in that, The content of the ethylene glycol ethyl ether acetate is 10-15 wt%.

5. The method for preparing a high-flowability solder stop agent adaptable to multiple processes as described in claim 1, characterized in that, The boron nitride sheet is a hexagonal boron nitride nanosheet.

6. The method for preparing a high-flowability solder resist adaptable to multiple processes as described in claim 1, characterized in that, The boron nitride sheet has a length and width of 100-500 nm and a thickness of 5-20 nm.

7. A high-flowability solder resist adaptable to multiple processes, characterized in that, It is obtained by the preparation method of the high-flowability solder stop flux adapted to multiple processes as described in any one of claims 1 to 6.

8. The high-flowability solder resist for multi-process adaptation as described in claim 7, characterized in that, The solder resist agent is used to apply solder resist agent to the metal surface by brushing. The coating after brushing is free of drips and brush marks, and has a uniform thickness.

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