Hot-melt direct writing heating system and metal melting direct writing forming method

Abstract

The application provides a hot-melt direct-writing heating system and a metal-melting direct-writing forming method. The hot-melt direct-writing heating system comprises a barrel exhaust mechanism (1), a feeding heating system and a printing substrate heating system (2). The feeding heating system comprises a barrel heating mechanism (4) for heating a barrel (3) and a needle heating mechanism (5) for heating a direct-writing needle (6). The printing substrate heating system comprises a suction disc (21), a suction disc heating mechanism (22) and a cooling mechanism (23) for cooling the suction disc heating mechanism in sequence. The suction disc comprises a suction disc surface (211) and a high-temperature-resistant fixing ring (212) arranged along the circumference of the suction disc surface. The suction disc surface is uniformly provided with a plurality of micropores. The application independently designs two heating sources to heat the barrel and the direct-writing needle respectively, and the barrel exhaust mechanism exhausts all oxygen. The micropores arranged on the suction disc surface can uniformly distribute the vacuum on the suction disc surface, thereby improving the adsorption uniformity.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and in particular to a hot melt direct writing heating system. Background Technology

[0002] Direct-write printing, inkjet printing, spray printing, and electrohydraulic inkjet printing are the most widely used 3D printing technologies in the field of electronic 3D printing research. To achieve the processing and shaping of metal materials, metal particles and organic polymers are usually mixed to form an ink slurry, which is in a liquid or semi-solid state at room temperature. After printing, processes such as curing, sintering, and reflow soldering are used to retain only the metal printed lines, thus obtaining a metal formed body. However, this method has the problem of organic residue. If organic polymers are retained in the final metal printed product, it will cause the various properties of the printed product to differ from those of pure metal products. For example, if printing metal lines, organic polymer residue will cause the conductivity of the lines to decrease. The conductivity of materials such as silver paste, copper paste, and metallic inks in existing technologies is generally only 3%-60% of that of the corresponding pure metal materials; the coefficient of thermal expansion of the lines does not match that of pure metals, and the temperature resistance of the lines also decreases due to the presence of organic matter, resulting in a risk to the reliability of the printed metal lines.

[0003] Traditional metal 3D printing uses metal-containing pastes as raw materials, which results in the problem of residual organic polymers. Although using pure metals as raw materials can avoid these problems, 3D forming with pure metals presents technical challenges, such as the significant spheroidization phenomenon in SLM (Spark Molding Laminate) technology. In the manufacture of fused deposition modeling (FDM) 3D products using pure metals as raw materials, ensuring that the printed lines are in a uniformly molten state before reaching the substrate is a problem that needs to be solved to achieve high printing accuracy.

[0004] Common raw materials for metal particles include InAg alloys, SnBi alloys, SnAgCu alloys, and AuSn alloys, which can be in the form of wire, block, or sphere. These raw materials all have relatively high melting points. SAC305 has a melting point of 217℃, and InAg alloy has a melting point of 142℃. Considering heat conduction and heat loss, currently used barrel heating systems can only heat to around 160℃, which is insufficient for heating SAC305 and InAg alloys. Common barrel heating systems use aluminum alloy as the heat conductor, placing the barrel and needle inside for heating. Due to the large coefficient of linear expansion of aluminum alloy, the position of the needle tip changes significantly before and after heating. Another option is to use a silicone rubber heating plate as the heating source. However, silicone rubber is limited to a maximum heating temperature of 200℃ (when the temperature exceeds 200℃, the material's flexibility, resilience, and surface hardness decrease), therefore it cannot be used for printing materials with melting points greater than 200℃.

[0005] Furthermore, in existing printing systems, air trapped in the feed cylinder during the material feeding process cannot be expelled. When the alloy is heated to a molten state, it reacts with oxygen in the air to undergo an oxidation reaction. Existing suction cups have low heating temperatures and poor surface temperature uniformity. Due to the high linear thermal expansion coefficient of the metal material, the flatness of the suction cup surface is significantly affected by the heating temperature. The uneven distribution of vacuum vents on the suction cup surface leads to uneven force on the object being suctioned, which also affects the flatness of the object's surface. Finally, the lack of an active cooling system beneath the suction cup means that the temperature affects the accuracy and lifespan of the equipment below. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a hot melt direct writing heating system and a metal melting direct writing forming method to solve the technical problems of existing electronic 3D printing technology, such as the large positional change of the needle tip due to simultaneous heating of the barrel and the needle, the easy oxidation of molten material by residual air in the barrel, the low heating temperature of the barrel, and the inability to print high melting point pure metal raw materials.

[0007] To achieve the above and other related objectives, the present invention provides a hot melt direct writing heating system, including a barrel venting mechanism, a material feeding heating system, and a printing substrate heating system. The material feeding heating system includes a barrel heating mechanism for heating the barrel and a needle heating mechanism for heating the direct writing needle. The printing substrate heating system sequentially includes a suction cup, a suction cup heating mechanism, and a cooling mechanism for cooling the suction cup heating mechanism. The suction cup includes a suction cup surface and a high-temperature resistant fixing ring arranged circumferentially along the suction cup surface. The suction cup surface is uniformly provided with a plurality of microholes.

[0008] Commercially available barrel heating modules often use the same heat source to heat both the writing tip and the barrel simultaneously. Because the writing tip is smaller, its heat dissipation rate is much faster than that of the barrel. The contact between the writing tip and surrounding air during ejection also accelerates the rapid cooling and solidification of the alloy. Therefore, the temperature of the writing tip must be higher than the melting point of the alloy to ensure that the alloy can smoothly land on the wafer (printing substrate) heating system after ejection. However, prolonged exposure of all the alloy inside the barrel to high temperatures accelerates its oxidation. This application effectively avoids the above problems by designing two independent heating sources for the barrel and the writing tip. By uniformly distributing several micropores on the suction cup surface, a vacuum can be evenly distributed, improving the uniformity of substrate adsorption. The barrel venting mechanism can promptly remove all residual oxygen, preventing oxidation reactions between the alloy and oxygen in the barrel after it melts. A cooling mechanism promptly cools the heat from the suction cup heating mechanism, preventing any impact on the accuracy and lifespan of downstream equipment.

[0009] Preferably, the barrel heating mechanism includes a barrel heating source sleeved on the outer wall of the barrel. The barrel heating source includes a heat-conducting sleeve and a heating wire. The outer wall of the heat-conducting sleeve is provided with a spiral limiting groove. The heating wire is wound around the outer surface of the heat-conducting sleeve along the spiral limiting groove. The end of the heating wire is provided with a heating connector.

[0010] Preferably, the needle heating mechanism includes a direct writing needle located at the lower end of the barrel and a needle heating source sleeved on the outside of the direct writing needle.

[0011] Preferably, a heat-uniforming sleeve is provided between the outer wall of the barrel and the inner wall of the heat-conducting sleeve; the heat-uniforming sleeve extends downward and covers the space between the direct-write tip and the tip heating source. The heat-uniforming sleeve prevents the barrel heating source and the tip heating source from directly contacting the barrel and the direct-write tip, and the heat transfer through the heat-uniforming sleeve results in a more uniform heating temperature distribution. The direct-write tip being installed inside the heat-uniforming sleeve effectively reduces the change in distance between the direct-write tip and the suction cup surface caused by temperature variations, thereby improving the printing quality of alloy printing products.

[0012] Preferably, the heating source of the barrel is covered with a heat-insulating sleeve, and the heating source of the needle is covered with a needle insulation component.

[0013] Preferably, the heat insulation sleeve is provided with a material cylinder heat insulation shell to prevent heat from being dissipated into the air.

[0014] More preferably, the heat resistance temperature of the needle insulation component is -50 to 300°C.

[0015] Preferably, a heat-insulating pad is provided between the needle heating source and the needle insulation component.

[0016] Preferably, the barrel heating source is equipped with a barrel temperature measuring element, the needle heating source is equipped with a needle temperature measuring element, and both the barrel and needle temperature measuring elements are externally connected to a temperature control system. The barrel and needle temperature measuring elements can detect the temperature of the barrel and the direct-writing needle part in real time, respectively, and the temperature control system adjusts the temperature in real time to keep the temperature constant within the required range.

[0017] Preferably, the pore size of the micropores is 15–50 μm.

[0018] Preferably, the height of the suction cup surface is higher than the height of the high-temperature resistant fixing ring, generally by 1mm, to facilitate the placement and removal of the wafer (printing substrate), facilitate processing, and ensure the flatness of the suction cup surface.

[0019] Preferably, the high-temperature resistant fixing ring is connected to the suction cup surface through a pipeline, the high-temperature resistant fixing ring is provided with a vacuum passage, and the vacuum passage is externally connected to a vacuum connector.

[0020] Preferably, the high-temperature resistant retaining ring is provided with a plurality of positioning pins at intervals for fixing the printing substrate. This ensures that the wafer (printing substrate) is placed in the same position each time, improving printing accuracy.

[0021] Preferably, the suction cup heating mechanism includes a heat-resistant and heat-insulating outer shell and an insulation plate, a heating plate, and a heat-spreading plate stacked sequentially inside the heat-resistant and heat-insulating outer shell, wherein the heat-spreading plate is in contact with the bottom surface of the suction cup.

[0022] Preferably, the heat spreader is equipped with a temperature sensor to test the heating temperature of the printing substrate in real time, which facilitates precise temperature control.

[0023] Preferably, the coefficient of linear expansion of the suction cup at temperatures between 40 and 300°C is (6.8–7.2) × 10⁻⁶ m × ℃. This design allows the molten alloy to solidify at a uniform rate upon reaching the printing substrate, resulting in high precision and a fast forming rate for products directly formed from pure metal.

[0024] Preferably, the thermal conductivity of the insulation board is 0.08–0.15 W / m·K; the coefficient of linear expansion of the insulation board at temperatures ranging from 0 to 300°C is (7.2–7.4) × 10⁻⁶. -6 m*℃, the heat resistance temperature of the insulation board is 0~600℃.

[0025] Preferably, the coefficient of linear expansion of the heat spreader at a temperature of 20–300°C is (10.61–10.95) × 10⁻¹⁰. -6 m*℃; the thermal conductivity of the heat spreader is 16.3~21.5W / m·k.

[0026] Preferably, the heat-resistant temperature of the heat-resistant insulation shell is 20–350°C.

[0027] Because temperature changes cause material dimensions to change, the greater the temperature difference before and after heating from room temperature to 300℃, the greater the deformation of the material. To minimize the impact of temperature on the stability of the entire heating system, this application creatively uses materials with low coefficients of linear expansion for key components, reducing the influence of the material's physical properties on the direct-write system. For example, if the heat spreader is made of brass H59 (thermal conductivity 125.1 W / m*K, coefficient of linear expansion (17.8~20.9)*10), which has better thermal conductivity, this would be beneficial. -6At m*℃, under otherwise constant conditions, heating from 25℃ to 300℃ resulted in height changes of 31μm and 59μm respectively for the heat spreader made of austenitic stainless steel and H59 brass due to temperature variations. Since the heat spreader is fixed below the suction cup, these height changes directly affect the flatness of the suction cup surface. The effect of using different materials for the heat spreader on the suction cup surface is nearly doubled. Based on the above data analysis, selecting appropriate materials will make the entire heating system more stable.

[0028] Preferably, the cooling mechanism includes several stacked heat-insulating cooling units. Each heat-insulating cooling unit includes stacked heat-insulating plates and cooling plates, with the uppermost heat-insulating plate contacting the bottom of the suction cup heating mechanism. The cooling plates have coolant channels, and their side walls have coolant inlets and outlets connected to these channels. The coolant filling the channels contains not only water but also other liquids with high specific heat capacity.

[0029] Preferably, the venting mechanism includes a pressure cap sealed at the feed port of the material cylinder, an air injection connector at the upper end of the pressure cap, a vent plug on the side wall of the pressure cap, and an air injection channel and an venting channel independently connected to the internal cavity of the material cylinder inside the pressure cap. The air injection channel is connected to the air injection connector, and the venting channel is connected to the vent plug.

[0030] Preferably, a rotary joint and a sealing cap are sequentially provided between the pressure cap and the material cylinder feeding port. The sealing cap is sealed and fixed to the material cylinder feeding port. A sealing ring is provided inside the rotary joint. The rotary joint passes through the pressure cap and is sealed to the sealing cap through the sealing ring.

[0031] More preferably, the rotary joint and the sealing cap are threadedly connected. During the tightening of the threads, the rotary joint presses the sealing cap, thereby pressing and tightening the sealing ring to achieve a seal on the feed port of the material cylinder.

[0032] The present invention also provides a method for metal melting and direct writing forming based on the above-mentioned hot melt direct writing heating system, comprising the following steps:

[0033] A feeding and heating system is used to heat the barrel, causing the metal raw material inside the barrel to molten; a barrel venting mechanism is used to inject propellant gas into the barrel; the propellant gas is selected from one or more of nitrogen, helium, and argon.

[0034] The direct writing needle is heated using a needle heating mechanism;

[0035] The printing substrate is heated using a suction cup heating mechanism;

[0036] The heating temperatures of the metal raw materials, printing substrate, and direct writing needle form an increasing temperature gradient.

[0037] This invention creates an increasing temperature gradient between the printing substrate, the printing barrel, and the direct-write tip, ensuring the metal raw material is in a uniform molten state. This allows the printed lines to solidify at a uniform speed upon reaching the printing substrate. The resulting product, obtained through molten direct-write forming of pure metal, exhibits high precision and a fast forming rate. The above process ensures that the printed lines are in a uniform molten state along the contact point between the printing barrel and the printing substrate, and that the printed lines solidify smoothly upon reaching the substrate.

[0038] The principle of this application is as follows: The main effect of the heating temperature of the barrel on the molten metal liquid is to change the viscosity of the fluid and the surface tension at the direct writing tip. Heating the barrel causes the raw material to melt. During printing, the molten raw material flows from the barrel to the printing tip along the flow channel. The direct writing tip is exposed to the environment, and there is a heat transfer process between the molten raw material and the environment at the direct writing tip, which causes the temperature of the molten raw material at the direct writing tip to drop. Since the direct writing tip is very small, the temperature drop of the molten raw material at the direct writing tip is significant. When the ambient temperature is low and the printed lines are thin, the molten raw material may even solidify and stagnate at the direct writing tip. During printing, the unavoidable heat transfer between the molten material and the environment at the writing tip must be considered. This invention addresses this by raising the writing tip temperature higher than the barrel temperature. This control of the barrel temperature regulates the viscosity of the molten material and its surface tension at the writing tip. Furthermore, this higher temperature prevents localized condensation near the writing tip, avoiding uneven and non-smooth lines. During printing, the barrel temperature must be higher than the substrate temperature. Under natural conditions (without heating the substrate), the molten material travels from the writing tip to the environment and then to the substrate, gradually solidifying as it transitions from a high-temperature to a low-temperature environment, thus completing the printing process. Theoretically, without heating the substrate, a larger temperature difference between the printing material and the substrate leads to faster solidification and printing speed. However, the applicant's experiments revealed that a larger temperature difference does not necessarily result in a faster printing speed. A suitable printing process should involve the raw material being extruded from the writing nozzle and carried away by the relative movement between the workpiece and the writing nozzle. This keeps the raw material at the tip of the writing nozzle in a dynamic, continuous extrusion state. When the raw material contacts the workpiece, a heat-conducting path is formed between the workpiece and the writing nozzle. This path transfers the heat of the extruded raw material to the workpiece, forming a heat sink that rapidly solidifies the raw material. If the printing substrate is not heated, excessive temperature differences and sudden breaks at the end of the heat-conducting path will cause uneven solidification of the raw material, resulting in poor solidification and a slower solidification rate. Heating the printing substrate to a temperature lower than the barrel effectively balances the effects of temperature difference solidification and other limiting factors.

[0039] During printing, because the metal raw material cannot be heated to a molten state simultaneously within the barrel, there are differences in the degree of melting between the different parts. Therefore, introducing propulsion air into the barrel helps to fuse the successively molten materials and extrude them quickly, ensuring the uniformity of the molten metal raw material extruded to the print nozzle, which contributes to improving the accuracy of the printed product. After the raw material is molten through heating in the barrel, propulsion air is introduced into the material carrier. The propulsive action of the propulsion air ensures the uniformity of the molten metal raw material extruded to the print nozzle, while also increasing the extrusion speed of the molten metal raw material and improving printing efficiency. In addition, it can also promptly remove any residual oxygen, preventing oxidation reactions between the alloy and oxygen in the barrel after it has been heated to a molten state.

[0040] Preferably, the heating temperature of the barrel is 10–25°C higher than the melting point of the metal raw material. Heating the barrel melts the raw material, allowing it to flow from the barrel to the print head during printing. The main effect of the barrel's heating temperature on the molten raw material is to alter its viscosity and surface tension at the print head. Controlling the barrel's heating temperature to be 10–25°C higher than, or slightly higher than, the melting point of the metal raw material helps to combat heat dissipation at the print head, ensuring that the metal raw material from the barrel to the rear of the print head remains in a stable molten state and flows out at the fastest and most uniform speed.

[0041] Preferably, the heating temperature of the direct writing tip is 30–80°C higher than the melting point of the metal material; more preferably, the heating temperature of the direct writing tip is 30–50°C higher than the melting point of the metal material. At the direct writing tip, the metal material should be in a state of dynamic and continuous extrusion. Combined with the heating effect of the barrel, this helps to combat the heat dissipation problem at the printhead, ensuring that the metal material remains in a stable molten state after exiting the printhead and flows out at the fastest and most uniform speed.

[0042] Preferably, the heating temperature of the printing substrate is 20-30°C lower than the melting point of the metal raw material. Heating the printing substrate is crucial for achieving high precision in the formed product. By heating the printing substrate to 20-30°C below the melting point of the metal raw material, a smooth heat conduction path is formed between the printing substrate workpiece and the printing nozzle segment, preventing breakage at the end. This ensures that the printed lines are in a uniform molten state at the contact point between the raw material carrier and the printing substrate, and allows the printed lines to solidify smoothly upon reaching the printing substrate. If the heating temperature of the printing substrate is too high, although the metal raw material phase at the substrate is relatively uniform, the solidification rate is too slow, leading to remelting between the printing raw material and the printing substrate workpiece, exacerbating oxidation and causing deformation of the printed morphology. If the heating temperature of the printing substrate is too low, the solidification rate is too fast, resulting in an uneven metal raw material phase at the substrate, and a rough surface and poor precision in the printed product.

[0043] Preferably, the inlet pressure of the propellant gas is 1–5 psi. Within this range, the printing speed can be maximized while ensuring printing accuracy. When the inlet pressure is too high, the molten metal fluid will be blown apart, resulting in turbulence and affecting printing accuracy. It may also cause incompletely molten metal material to be pushed into the printhead, causing a risk of blockage. When the inlet pressure is in the range of 1–5 psi, the uniformity of the molten metal material can be ensured to the greatest extent, avoiding interference between materials that melt sequentially, thereby improving printing accuracy. When the inlet pressure is too low, the outflow velocity of the molten metal fluid will not increase significantly, and it will not significantly help to improve the printing speed. Furthermore, the slow outflow will cause the metal to stay at the printhead for a longer time, resulting in metal condensation, poor printing effect, and a risk of printhead blockage.

[0044] Preferably, the metal raw material is selected from one or more of elemental copper, elemental silver, In-based alloys, SnBi-based alloys, SnAgCu-based alloys, and AuSn-based alloys.

[0045] As described above, the present invention has the following beneficial effects:

[0046] (1) By designing two separate heating sources at the barrel and the direct writing needle respectively, the problem of using the same heating source to heat the direct writing needle and the barrel at the same time in the prior art is effectively avoided. The direct writing needle dissipates heat quickly, which accelerates the cooling and solidification of the alloy when the material is discharged.

[0047] (2) The use of a barrel exhaust mechanism can promptly remove all residual oxygen, thus preventing the alloy from undergoing an oxidation reaction with the oxygen in the barrel after it is heated to a molten state.

[0048] (3) By uniformly setting several micro-holes on the suction cup surface, the vacuum can be evenly distributed on the suction cup surface, which can improve the uniformity of printing substrate adsorption; the suction cup heating temperature is high, the suction cup surface temperature uniformity is good, and the flatness is less affected by the heating temperature.

[0049] (4) The printing substrate heating system uses a material with a low coefficient of linear expansion, which effectively reduces the impact of the material's physical properties on the direct writing system;

[0050] (5) A cooling mechanism is used to cool the heat of the suction cup heating mechanism in a timely manner to avoid affecting the accuracy and service life of the downstream equipment;

[0051] (6) By creating an increasing temperature gradient in the heating temperature of the printing substrate, the barrel, and the direct-write tip, the metal raw material is in a uniform molten state, and the printed lines solidify at a uniform speed after reaching the printing substrate. The products obtained by the molten direct-write forming of pure metal in this invention have high precision and fast forming speed. The above process can achieve a uniform molten state of the printed lines at the contact point between the barrel and the printing substrate, and allow the printed lines to solidify smoothly after reaching the printing substrate. Attached Figure Description

[0052] Figure 1 The diagram shown is a schematic diagram of the hot melt direct writing heating system of Example 1.

[0053] Figure 2 The diagram shown is an exploded view of the heating system for the printing substrate in Example 1.

[0054] Figure 3 This is a cross-sectional view of the cooling plate.

[0055] Figure 4 The diagram shown is an assembly drawing of the barrel venting mechanism and the barrel heating mechanism of Example 1.

[0056] Figure 5 Displayed as Figure 4 A sectional view.

[0057] Figure 6 The diagram shown is a structural schematic of the suction cup in Example 1.

[0058] Figure 7 The diagram shown is a structural schematic of the barrel heating source for Example 1.

[0059] Reference numerals: 1. Barrel venting mechanism; 11. Pressure cap; 111. Air injection connector; 112. Vent plug; 113. Air injection channel; 114. Vent channel; 12. Rotary joint; 13. Sealing cap; 14. Sealing ring; 2. Printing substrate heating system; 21. Suction cup; 211. Suction cup surface; 212. High-temperature resistant retaining ring; 214. Vacuum connector; 215. Positioning pin; 216. Vacuum air path; 22. Suction cup heating mechanism; 221. Heat-resistant insulation shell; 222. Insulation board; 223. Heating plate; 224. Heat spreader; 23. Cooling mechanism; 231. Heat insulation plate; 232. Cooling plate; 233. Coolant flow channel; 23 4. Coolant inlet; 235. Coolant outlet; 236. Cooling mechanism fixing plate; 24. Temperature sensor; 25. Notch; 26. Insulating protective cover; 3. Barrel; 31. Barrel fixing plate; 32. Barrel heat insulation plate; 4. Barrel heating mechanism; 41. Barrel heating source; 42. Uniform heat sleeve; 43. Heat insulation sleeve; 44. Barrel temperature measuring element; 45. Barrel heat insulation shell; 411. Heat conducting sleeve; 412. Heating wire; 413. Spiral limiting groove; 414. Heating and temperature measuring connector; 5. Needle heating mechanism; 51. Needle heating source; 52. Needle insulation element; 53. Needle temperature measuring element; 54. Heat insulation pad; 6. Direct writing needle. Detailed Implementation

[0060] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0061] In the description of this application, it should be noted that the terms "upper", "lower", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0062] Unless otherwise expressly specified and limited, the terms "connection," "fixed," and "set" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; or they can refer to a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0063] Example 1

[0064] like Figure 1 As shown, this application provides a hot melt direct writing heating system, including a barrel venting mechanism 1, a material feeding heating system and a printing substrate heating system 2. The material feeding heating system includes a barrel heating mechanism 4 for heating the barrel 3 and a needle heating mechanism 5 for heating the direct writing needle 6. The printing substrate heating system includes a suction cup 21, a suction cup heating mechanism 22 and a cooling mechanism 23 for cooling the suction cup heating mechanism.

[0065] like Figure 2 As shown, the suction cup heating mechanism includes a heat-resistant and heat-insulating outer shell 221 and a heat-insulating plate 222, a heating plate 223, and a heat-spreading plate 224 stacked sequentially within the heat-resistant and heat-insulating outer shell. The heat-spreading plate is in contact with the bottom surface of the suction cup and is equipped with a temperature sensor 24. The cooling mechanism includes two stacked heat-insulating cooling units, each including a stacked heat-insulating plate 231 and a cooling plate 232. The uppermost heat-insulating plate is in contact with the bottom of the suction cup heating mechanism. The cooling plate has a coolant flow channel 233. The heat-resistant and heat-insulating outer shell has a notch 25 and an insulating protective cover 26 adapted to the shape of the notch. The temperature sensor 24 extends outward from the notch. The bottom of the cooling mechanism has a cooling mechanism fixing plate 236.

[0066] In this embodiment, the coefficient of linear expansion of the suction cup at temperatures ranging from 40 to 300°C is 6.8 to 7.2 × 10⁻⁶. -6 The thermal conductivity of the insulation board is 0.08–0.15 W / m·K; the coefficient of linear expansion of the insulation board at temperatures ranging from 0 to 300°C is 7.2–7.4 × 10⁻⁶ m·℃. -6 The insulation board has a heat resistance temperature of 0–600℃; the heat spreader has a linear expansion coefficient of 10.61–10.95 × 10⁻⁶ m*℃ at 20–300℃. -6 m*℃; the thermal conductivity of the heat spreader is 16.3~21.5W / m·k; the heat resistance temperature of the heat-resistant insulation shell is 20~350℃.

[0067] like Figure 5As shown, the venting mechanism includes a pressure cap 11 sealed at the feed port of the material cylinder. The upper end of the pressure cap is provided with an air injection connector 111, and the side wall of the pressure cap is provided with a vent plug 112. The pressure cap is provided with an air injection channel 113 and an venting channel 114 that are connected to the internal cavity of the material cylinder. The air injection channel is connected to the air injection connector, and the venting channel is connected to the vent plug. A rotary connector 12 and a sealing cap 13 are also provided in sequence between the pressure cap and the feed port of the material cylinder. The sealing cap is sealed and fixed to the feed port of the material cylinder. A sealing ring 14 is provided inside the rotary connector. The rotary connector passes through the pressure cap and is sealed to the sealing cap through the sealing ring.

[0068] like Figure 5 As shown, the needle heating mechanism includes a needle heating source 51 sleeved on the outside of the writing needle, and the needle heating source is equipped with a needle temperature measuring element 53. Figure 7 As shown, the barrel heating mechanism includes a barrel heating source 41 sleeved on the outer wall of the barrel, and a barrel temperature measuring element 44. The barrel heating source includes a heat-conducting sleeve 411 and a heating wire 412. The outer wall of the heat-conducting sleeve is provided with a spiral limiting groove 413. The heating wire is wound along the spiral limiting groove on the outer surface of the heat-conducting sleeve, and the end of the heating wire is provided with a heating connector 414. A uniform heating sleeve 42 is provided between the outer wall of the barrel and the inner wall of the heat-conducting sleeve. The uniform heating sleeve extends downward and covers the space between the writing needle and the needle heating source. The heating source of the barrel is covered with a heat-insulating sleeve 43, and a barrel insulation shell 45 is provided outside the heat-insulating sleeve; the heating source of the needle is covered with a needle insulation component 52, and a heat-insulating gasket 54 is provided between the heating source of the needle and the needle insulation component; the heat resistance temperature of the needle insulation component is -50 to 300℃, and the barrel temperature measuring component and the needle temperature measuring component are externally connected to a temperature control system. The barrel is provided with a barrel fixing plate 31, and a barrel heat insulation plate 32 is provided between the barrel fixing plate and the barrel.

[0069] like Figure 6 As shown, the suction cup includes a suction cup surface 211 and a high-temperature resistant fixing ring 212 arranged circumferentially along the suction cup surface. The suction cup surface is uniformly provided with a plurality of micropores with a diameter of 30μm. The height of the suction cup surface is higher than the height of the high-temperature resistant fixing ring. The high-temperature resistant fixing ring is connected to the suction cup surface through a pipeline. The high-temperature resistant fixing ring is provided with a vacuum passage 216 in the radial direction. The vacuum passage is externally connected to a vacuum connector 214. The high-temperature resistant fixing ring is provided with a plurality of positioning pins 215 at intervals for fixing the printing substrate.

[0070] The working principle of this embodiment is as follows:

[0071] like Figure 5As shown, a protective gas (such as nitrogen) is injected into the barrel through the gas injection connector 111. The protective gas enters the barrel along the gas injection channel 113, and the air remaining in the barrel is discharged from the vent plug 112 along the exhaust channel 114, so as to prevent the molten alloy in the barrel from being oxidized.

[0072] Turn on the heating source 41 of the barrel, and the heat is evenly transferred to the barrel through the uniform heating sleeve 42, so that the alloy inside melts; the heat insulation sleeve 43 and the barrel insulation shell 45 are used for insulation to avoid heat loss.

[0073] Turn on the needle heating source 51, and the heat is evenly transferred to the writing needle 6 through the uniform heating sleeve 42 wrapped around the writing needle 6. The needle insulation component 52 keeps the needle warm and prevents heat loss.

[0074] like Figure 6 As shown, the wafer (printing substrate) is fixed on the suction cup using positioning pins 215, and connected to the vacuum generator using vacuum connector 214 to generate negative pressure on the suction cup surface 211. The suction cup surface, based on its microporous structure, can firmly adsorb the wafer (printing substrate).

[0075] like Figure 2 As shown, during the hot melt direct writing process, the heating plate 223 is turned on for heating, and the heat is evenly transferred to the suction cup 21 through the heat spreader 224. The heating temperature is monitored in real time by the temperature sensor 24, and the temperature is controlled and adjusted by an external temperature control system. Because the heat spreader is made of a material with specific properties, the change in the height of the heat spreader caused by temperature changes can be effectively reduced, thereby improving printing accuracy.

[0076] Coolant (water or other liquids with high specific heat capacity) is injected into the coolant channels 233 of the two cooling plates 232 through the coolant inlet 234. After the coolant exchanges heat with the suction cup heating system, it is discharged from the coolant outlet 235, which cools the heat of the suction cup heating mechanism in time and avoids affecting the accuracy and service life of the downstream equipment.

[0077] This application also provides a method for metal melting and direct writing forming using the above-mentioned hot melt direct writing heating system, including the following steps:

[0078] A feeding and heating system is used to heat the barrel, causing the metal raw material inside to melt; a barrel venting mechanism is used to inject nitrogen into the barrel; the heating temperature of the barrel is 10-25℃ higher than the melting point of the metal raw material; the metal raw material is SAC305 with a melting point of 217℃; the barrel heating temperature is 240℃.

[0079] The direct writing needle is heated by a needle heating mechanism; the heating temperature of the direct writing needle is 30-80℃ higher than the melting point of the metal raw material, specifically 260℃.

[0080] The printing substrate is heated by a suction cup heating mechanism; the heating temperature of the printing substrate is 20-30°C lower than the melting point of the metal raw material, specifically 195°C.

[0081] The heating temperatures of the metal raw materials, printing substrate, and direct writing needle form an increasing temperature gradient.

[0082] Example 2

[0083] The difference between Example 2 and Example 1 is that the number of heat insulation and cooling units is 3, the pore size of the micropores on the suction cup surface is 15μm, and the coefficient of linear expansion of the suction cup at temperatures ranging from 40 to 300°C is 7.0*10. -6 m*℃; the thermal conductivity of the insulation board is 0.1 W / m·K; the coefficient of linear expansion of the insulation board at temperatures ranging from 0 to 300℃ is 7.3*10 -6 The insulation board has a heat resistance temperature of 0–600℃; the heat spreader has a linear expansion coefficient of 10.8 × 10⁻⁶ m*℃ at a temperature of 20–300℃. -6 m*℃; the thermal conductivity of the heat spreader is 20.0 W / m·K; the heat resistance temperature of the heat-resistant insulation shell is 200~350℃, and the other components are exactly the same.

[0084] This application also provides a method for metal melting and direct writing forming using the above-mentioned hot melt direct writing heating system, including the following steps:

[0085] A feeding and heating system is used to heat the barrel, causing the metal raw material inside to melt; a barrel venting mechanism is used to inject nitrogen into the barrel; the heating temperature of the barrel is 10-25℃ higher than the melting point of the metal raw material; the metal raw material is SAC305 with a melting point of 217℃; the barrel heating temperature is 240℃.

[0086] The direct writing needle is heated by a needle heating mechanism; the heating temperature of the direct writing needle is 30-80℃ higher than the melting point of the metal raw material, specifically 260℃.

[0087] The printing substrate is heated by a suction cup heating mechanism; the heating temperature of the printing substrate is 20-30°C lower than the melting point of the metal raw material, specifically 195°C.

[0088] The heating temperatures of the metal raw materials, printing substrate, and direct writing needle form an increasing temperature gradient.

[0089] Example 3

[0090] The difference between Example 3 and Example 1 is that the number of heat insulation and cooling units is one; the pore size of the micropores on the suction cup surface is 50 μm; the linear expansion coefficient of the suction cup at a temperature of 40–300℃ is 7.2 × 10⁻⁶ m·℃; the thermal conductivity of the insulation board is 0.08 W / m·K; the linear expansion coefficient of the insulation board at a temperature of 0–300℃ is 7.2 × 10⁻⁶ m·℃; the heat resistance temperature of the insulation board is 0–600℃; the linear expansion coefficient of the heat spreader at a temperature of 20–300℃ is 10.61 × 10⁻⁶ m·℃; the thermal conductivity of the heat spreader is 16.3 W / m·K; and the heat resistance temperature of the heat-resistant insulation shell is 20–300℃. All other components are identical.

[0091] This application also provides a method for metal melting and direct writing forming using the above-mentioned hot melt direct writing heating system, including the following steps:

[0092] A feeding and heating system is used to heat the barrel, causing the metal raw material inside to melt; a barrel venting mechanism is used to inject nitrogen into the barrel; the heating temperature of the barrel is 10-25℃ higher than the melting point of the metal raw material; the metal raw material is InAg3 with a melting point of 143℃; the barrel heating temperature is 160℃.

[0093] The direct writing needle is heated by a needle heating mechanism; the heating temperature of the direct writing needle is 30-80℃ higher than the melting point of the metal raw material, specifically 180℃.

[0094] The printing substrate is heated using a suction cup heating mechanism; the heating temperature of the printing substrate is 20-30°C lower than the melting point of the metal raw material, specifically 120°C.

[0095] The heating temperatures of the metal raw materials, printing substrate, and direct writing needle form an increasing temperature gradient.

[0096] In summary, this invention effectively avoids the problems of using a single heating source to heat both the writing nozzle and the cylinder simultaneously, which leads to rapid heat dissipation from the writing nozzle and accelerated alloy solidification during ejection. The cylinder venting mechanism effectively removes residual oxygen, preventing oxidation reactions between the alloy and oxygen in the cylinder after it reaches a molten state. The uniform distribution of vacuum across the suction cup surface using numerous micropores improves substrate adsorption uniformity. The high suction cup heating temperature results in good surface temperature uniformity and minimal impact on flatness. The substrate heating system uses a material with a low coefficient of linear expansion, effectively reducing the influence of the material's physical properties on the writing system. A cooling mechanism promptly dissipates heat from the suction cup heating mechanism, preventing impact on the accuracy and lifespan of downstream equipment. Therefore, this invention effectively overcomes the shortcomings of existing technologies and possesses high industrial applicability.

[0097] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for direct writing of molten metal, characterized in that, A hot melt direct writing heating system is adopted, which includes a barrel venting mechanism (1), a material feeding heating system and a printing substrate heating system (2). The material feeding heating system includes a barrel heating mechanism (4) for heating the barrel (3) and a needle heating mechanism (5) for heating the direct writing needle (6). The printing substrate heating system includes a suction cup (21), a suction cup heating mechanism (22) and a cooling mechanism (23) for cooling the suction cup heating mechanism. The venting mechanism includes a pressure cap (11) sealed at the barrel feeding port. The pressure cap has an air injection connector (111) at its upper end and a vent plug (112) on its side wall. The pressure cap has an independent air injection channel (113) and an venting channel (114) that communicate with the internal cavity of the barrel. The metal melting direct writing forming method includes the following steps: A feeding and heating system is used to heat the material cylinder, causing the metal raw material inside the cylinder to molten; a material cylinder exhaust mechanism is used to inject propellant gas into the material cylinder; the propellant gas is selected from one or more of nitrogen, helium, and argon. The direct writing needle is heated using a needle heating mechanism; The printing substrate is heated using a suction cup heating mechanism; Among them, the heating temperatures of the metal raw materials, printing substrate and direct writing needle form an increasing temperature gradient; The heating temperature of the barrel is 10-25℃ higher than the melting point of the metal raw material; the heating temperature of the direct writing needle is 30-80℃ higher than the melting point of the metal raw material; and the heating temperature of the printing substrate is 20-30℃ lower than the melting point of the metal raw material.

2. The metal melting direct writing forming method according to claim 1, characterized in that, The air injection channel is connected to the air injection connector, and the exhaust channel is connected to the vent plug; the inlet pressure of the propulsion air is 1~5psi.

3. The metal melting direct writing forming method according to claim 1, characterized in that, The barrel heating mechanism includes a barrel heating source (41) sleeved on the outer wall of the barrel. The barrel heating source includes a heat-conducting sleeve (411) and a heating wire (412). The outer wall of the heat-conducting sleeve is provided with a spiral limiting groove (413). The heating wire is coiled around the outer surface of the heat-conducting sleeve along the spiral limiting groove. The end of the heating wire is provided with a heating connector (414). The needle heating mechanism includes a needle heating source (51) sleeved on the outside of the writing needle.

4. The metal melting direct writing forming method according to claim 1, characterized in that, The suction cup heating mechanism includes a heat-resistant and heat-insulating shell (221) and a heat-insulating plate (222), a heating plate (223) and a heat-spreading plate (224) stacked sequentially inside the heat-resistant and heat-insulating shell. The heat-spreading plate is in contact with the bottom surface of the suction cup and is equipped with a temperature sensor (24).

5. The metal melting direct writing forming method according to claim 1, characterized in that: The cooling mechanism includes several stacked heat-insulating cooling units. Each heat-insulating cooling unit includes stacked heat insulation plates (231) and cooling plates (232). The uppermost heat insulation plate is in contact with the bottom of the suction cup heating mechanism. The cooling plate is provided with a coolant flow channel (233). The side wall of the cooling plate is provided with a coolant inlet (234) and a coolant outlet (235) connected to the coolant flow channel.

6. A hot-melt direct-write heating system, characterized in that, To implement the metal melting direct writing forming method as described in claim 1, the hot melt direct writing heating system includes a barrel venting mechanism (1), a material feeding heating system and a printing substrate heating system (2). The material feeding heating system includes a barrel heating mechanism (4) for heating the barrel (3) and a needle heating mechanism (5) for heating the direct writing needle (6). The printing substrate heating system includes a suction cup (21), a suction cup heating mechanism (22), and a cooling mechanism (23) for cooling the suction cup heating mechanism. The suction cup includes a suction cup surface (211) and a high-temperature resistant fixing ring (212) arranged circumferentially along the suction cup surface. The suction cup surface is uniformly provided with a plurality of microholes.

7. The hot-melt direct-write heating system according to claim 6, characterized in that: The barrel heating mechanism includes a barrel heating source (41) sleeved on the outer wall of the barrel. The barrel heating source includes a heat-conducting sleeve (411) and a heating wire (412). The outer wall of the heat-conducting sleeve is provided with a spiral limiting groove (413). The heating wire is coiled along the spiral limiting groove on the outer surface of the heat-conducting sleeve. The end of the heating wire is provided with a heating connector (414). The needle heating mechanism includes a needle heating source (51) sleeved on the outside of the direct writing needle. A uniform heating sleeve (42) is provided between the outer wall of the barrel and the inner wall of the heat-conducting sleeve. The uniform heating sleeve extends downward and covers the space between the direct writing needle and the needle heating source.

8. The hot-melt direct-write heating system according to claim 7, characterized in that: The barrel heating source is covered with a heat-insulating sleeve (43), and the heat-insulating sleeve is covered with a barrel insulation shell (45); the needle heating source is covered with a needle insulation component (52), and a heat-insulating gasket (54) is provided between the needle heating source and the needle insulation component. The heat resistance temperature of the needle insulation component is -50~300℃; the barrel heating source is equipped with a barrel temperature measuring component (44), and the needle heating source is equipped with a needle temperature measuring component (53). The barrel temperature measuring component and the needle temperature measuring component are externally connected to a temperature control system.

9. The hot-melt direct-write heating system according to claim 6, characterized in that: The pore size of the micropore is 15~50μm; the height of the suction cup surface is higher than the height of the high temperature resistant fixing ring; the high temperature resistant fixing ring is connected to the suction cup surface through a pipeline; the high temperature resistant fixing ring is provided with a vacuum passage (216) in the radial direction; the vacuum passage is externally connected to a vacuum connector (214); and the high temperature resistant fixing ring is provided with a number of positioning pins (215) at intervals for fixing the printing substrate.

10. The hot-melt direct-write heating system according to claim 6, characterized in that: The suction cup heating mechanism includes a heat-resistant and heat-insulating shell (221) and a heat-insulating plate (222), a heating plate (223) and a heat-spreading plate (224) stacked sequentially inside the heat-resistant and heat-insulating shell. The heat-spreading plate is in contact with the bottom surface of the suction cup and is equipped with a temperature sensor (24).

11. The hot-melt direct-write heating system according to claim 10, characterized in that: The coefficient of linear expansion of the suction cup at temperatures ranging from 40 to 300°C is (6.8 to 7.2) * 10⁻¹⁰. -6 m*℃; the thermal conductivity of the insulation board is 0.08~0.15W / m·k; the coefficient of linear expansion of the insulation board at temperatures of 0~300℃ is (7.2~7.4)*10 -6 The heat resistance temperature of the insulation board is 0~600℃; the coefficient of linear expansion of the heat spreader at 20~300℃ is (10.61~10.95)*10. -6 m*℃; the thermal conductivity of the heat spreader is 16.3~21.5 W / m·k; the heat resistance temperature of the heat-resistant insulation shell is 20~350℃.

12. The hot-melt direct-write heating system according to claim 6, characterized in that: The cooling mechanism includes several stacked heat-insulating cooling units. Each heat-insulating cooling unit includes stacked heat insulation plates (231) and cooling plates (232). The uppermost heat insulation plate is in contact with the bottom of the suction cup heating mechanism. The cooling plate is provided with a coolant flow channel (233). The side wall of the cooling plate is provided with a coolant inlet (234) and a coolant outlet (235) connected to the coolant flow channel.

13. The hot-melt direct-write heating system according to claim 6, characterized in that: The air injection channel is connected to the air injection connector, and the exhaust channel is connected to the vent plug.

14. The hot-melt direct-write heating system according to claim 13, characterized in that: A rotary joint (12) and a sealing cap (13) are sequentially provided between the pressure cap and the material cylinder feeding port. The sealing cap is sealed and fixed to the material cylinder feeding port. A sealing ring (14) is provided inside the rotary joint. The rotary joint passes through the pressure cap and is sealed to the sealing cap through the sealing ring.

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