Manufacture of electrical circuits on insulating coatings

Abstract

A method for forming an electrical circuit on an insulating ceramic substrate or on an insulating ceramic layer (25) of a substrate (21), the method comprising: depositing an electrically conductive material (23) onto a surface of the ceramic substrate or ceramic layer; and aligning a laser beam (26) to the conductive material on the ceramic substrate and moving the laser beam relative to the ceramic substrate or ceramic layer along a predetermined circuit pattern such that the conductive material melts onto the ceramic surface or ceramic layer to form a conductive line (24).

Description

Technical Field

[0001] Electrical circuits can be formed by applying a pattern of conductive traces made from a metal alloy to an electrically insulating surface. Background Art

[0002] Coating techniques such as thermal spraying, plasma vapor deposition (PVD), or inkjet printing are used to create circuits on insulating surfaces such as aluminum oxide, such as electric heaters for household appliances or electric vehicles. The components are typically manufactured from a metal substrate to which an insulating plate made of glass or ceramic is soldered, or a ceramic coating is applied. The most widely used method is to deposit ceramic coatings based on aluminum oxide using thermal spraying.

[0003] However, these methods require additional processing steps, specialized tools, or masks in addition to depositing conductive lines on insulating surfaces.

[0004] Thermal spraying technology is widely used to form conductive and structured coatings. The main advantages of thermal spraying technology include high application speeds, for example, processing speeds of up to 150 g / min, which can cover 1 square meter with 30 μm of conductive material in less than 5 minutes of processing time. In addition, it has the ability to deposit on three-dimensional surfaces and low material costs. At the same time, however, thermal spray coatings always require masks to cover areas that cannot be coated. In addition, the production of long, meandering conductive lines by thermal spraying technology requires complex masks or post-processing, such as removing material by laser ablation. Both solutions incur additional costs comparable to the coating deposition. Special thermal spraying technologies, such as the MESOSCRIBE deposition process of CVD Materials Group or the ECOCOAT deposition process of ecoCOAT GmbH (Allershausen, Germany), require additional consumables and have processing speeds that are several orders of magnitude lower than those of atmospheric plasma spraying, arc wire spraying, and flame spraying.

[0005] PVD produces thin-film deposits, with the advantage of using floating masks that can be easily applied, reused, and / or refurbished multiple times. However, a disadvantage of using PVD in this application is its slow deposition rate. For example, depositing a layer thick enough to form a heater requires at least 10 hours per square meter, making it approximately 100 times slower than thermal spraying. The typical thickness of the deposited conductive lines ranges from 10 to 50 μm, often 15 to 30 μm. Therefore, the PVD processing time for a single component can take about an hour. In addition, the vacuum conditions required by PVD make the process unsuitable for continuous production.

[0006] Inkjet printing avoids the masking or post-deposition structuring issues of thermal spray technology, but it is not without its drawbacks. The printing material must be made from a slurry containing solvents and additives. The processing speed (for example, 1 to 8 hours per square meter) is much lower than that of technologies such as thermal spray. Moreover, the printed material must be dried and sintered after printing. These post-processing steps are time-consuming and energy-intensive, and there is a risk of cracking or delamination due to the large thickness required. Summary of the Invention

[0007] The present invention relates to a laser additive layer manufacturing (LALM) process, such as selective laser melting (SLM), laser beam powder bed fusion (LB-PBF), or layer-by-layer manufacturing (LOM) machining, for depositing conductive patterned circuits onto insulating surfaces. This technology combines the advantages of the aforementioned technologies, such as high-speed production, high efficiency, and high reproducibility, while providing reliable and cost-effective products.

[0008] The LALM process significantly reduces material consumption because it does not require masks and / or reprocessing, improves the efficiency of the production process and simplifies the production process. According to a non-limiting example, a conductive line (such as a Ni-based alloy, a Fe-based alloy, a Cu-based alloy or an Al-based alloy) can be deposited onto a surface by the LALM process at a thickness of 10 to 50 μm at a processing speed comparable to the application speed of thermal spraying technology (for example, 1 to 2 times that). In addition, according to a non-limiting example, a serpentine electric track can be applied to a 200 mm × 200 mm plate made of, for example, steel or aluminum alloy and having an electrically insulating surface by the LALM process in about 1 minute, which is several orders of magnitude faster than PVD and inkjet printing. However, unlike thermal spraying technology, the LALM process does not require masks or reprocessing steps (such as laser ablation) to form a serpentine conductive pattern.

[0009] The LALM process is far more efficient than other known processes because there is no material loss due to overspray. Specifically, the powder material or film applied to the panel surface in areas that are not conductive paths is not processed by the laser and, therefore, does not melt or undergo changes in morphology or composition. Furthermore, this unprocessed material on the panel can be recycled. In addition to its greater efficiency in terms of material consumption, the LALM process also consumes significantly less electrical energy than thermal spray techniques. For example, compared to atmospheric plasma spraying, electricity consumption is reduced by 10-20%; compared to arc wire spraying, it is reduced by 50-70%.

[0010] Compared to thermal spraying or inkjet printing, the conductive traces produced via LALM also have a more uniform structure, thus avoiding hot spots caused by the non-constant resistance of the metal layer. Furthermore, the resistivity of the conductive traces applied via LALM is lower than that achieved by thermal spraying and inkjet printing due to the lower oxide content and lower porosity formed during the deposition process. This allows the conductive traces to be thinner than with conventional techniques, reducing the amount of material required to fabricate them.

[0011] Additionally, unlike thermal spraying techniques and inkjet printing, the LALM process does not require post-processing to create patterns, or to dry and sinter the material.

[0012] While LALM processes (such as SLM), like inkjet printing and PVD, are limited to forming conductors on flat substrates, thermal spraying can be used on three-dimensional surfaces. This limitation is not a technical limitation, as the design of circuit components, such as heaters, is applied to flat surfaces.

[0013] An embodiment is directed to a method for forming a circuit on a substrate, comprising: depositing a conductive material onto a ceramic surface on the substrate or the substrate itself, and aiming a laser beam at the conductive material on the ceramic surface, moving the laser beam relative to the ceramic surface along a predetermined circuit pattern, so that the conductive material melts onto the ceramic surface to form a conductive circuit.

[0014] In an embodiment, the method may be a laser additive layer manufacturing (LALM) process.

[0015] In other embodiments, the LALM may be a selective laser melting (SLM) process. The SLM process may be performed in a protective atmosphere (eg, a protective argon atmosphere), and the conductive material may include a conductive powder or a conductive film.

[0016] According to other embodiments, the LALM may be a laser beam-powder bed fusion (LB-PBF) process. Additionally, the conductive material may include a conductive powder.

[0017] According to further embodiments, the LALM may be a Laminated Object Manufacturing (LOM) machine. Additionally, the conductive material may include a conductive film.

[0018] According to further embodiments, the predetermined pattern of the circuit may be a serpentine pattern.

[0019] In other embodiments, before depositing the conductive material, the method may further include at least one of the following steps: performing patterning pre-treatment on the surface to which the conductive traces are to be attached using a laser beam, or applying a seed layer to which the conductive traces are to be attached.

[0020] In some other embodiments, in order to achieve sufficient adhesion of the electric heating line, the method may further include at least one of the following steps: reducing the intensity of the laser beam, reducing the laser beam pulse width, or reducing the laser spot moving speed of the laser beam.

[0021] According to other embodiments, the conductive material may include a Ni-based, Fe-based, Al-based, or Cu-based alloy.

[0022] According to other embodiments, the substrate may be a metal substrate or a ceramic substrate.

[0023] According to other embodiments, the ceramic surface may be part of a ceramic layer formed on a substrate. The ceramic layer and the conductive trace may be part of a coating system applied to the substrate. The method may further include applying an insulating layer over the conductive trace and forming conductive contacts on the insulating layer. The insulating layer and the conductive trace may be part of the coating system. Additionally, before the ceramic layer is formed on the substrate, the method may further include applying a bond coat as part of the coating system to the substrate. The ceramic layer may be formed over the bond coat.

[0024] Other embodiments and advantages of the present invention may be obtained through a study of the text and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In the following detailed description, the present invention is further described by way of non-limiting embodiments thereof with reference to the several drawings shown, wherein like reference numerals designate similar parts throughout the several views of the drawings, as follows:

[0026] Figure 1 An electric heating element is shown formed by a coating system applied to a substrate;

[0027] Figure 2 An exemplary diagram showing a LALM process for forming a conductive circuit of a plate-type electric heating device on a ceramic substrate according to an embodiment of the present invention;

[0028] Figure 3A and 3B An exemplary diagram showing the structure of a plate type electric heater according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The details shown herein are illustrative only and are intended only for purposes of illustrating and discussing embodiments of the present invention. The purpose is to provide the most useful and understandable illustration of the principles and concepts of the present invention. In this regard, structural details of the present invention are not presented in detail, as they are beyond the scope required for a basic understanding. By combining this description with the accompanying drawings, those skilled in the art will be able to clearly understand how the various embodiments of the present invention can be implemented in practice.

[0030] Figure 1 An electric heating element (1) is shown, wherein a coating system (10) is formed on a substrate (11). The coating system (10) is formed by an optional metal bonding coating (12), such as Ni-based and Fe-based alloys (e.g., Ni 20Cr, Ni 5Al, AISI 420, AISI 316L), so that the heating element is better attached to the substrate (11), which is preferably made of aluminum alloy, low carbon steel, stainless steel, etc. In other non-limiting embodiments, the substrate (11) can be a ceramic substrate. A first insulating layer (13) composed of an electrically insulating ceramic material (such as Al2O3 or other ceramic materials or glass) is applied to electrically isolate the conductive heating line (14) from the substrate (11) or the bonding coating (12). The electrically conductive heating line (14) formed by the additive layer manufacturing (LALM) process consists of an electrically conductive material (such as Ni 20Cr, NiCr, pure Ni, or Ni-based alloys, Fe-based alloys, Al-based alloys or Cu-based alloys), that is, in particular a patterned electrically conductive layer, which is applied, for example, in a meander-type pattern layout.

[0031] A second insulating layer (15) composed of an electrically insulating ceramic material (such as Al2O3 or other ceramic materials or glass) is thermally sprayed onto and between the electrically conductive heating lines (14) to electrically isolate the conductive layer from the environment and prevent accidental contact. The conductive layer (16), such as copper or a copper-based alloy, is patterned in multiple areas during the thermal spraying process using a mechanical mask to allow the electrically conductive heating lines 14 to be connected to an external power source (not shown), such as by soldering.

[0032] According to an embodiment, a laser additive layer manufacturing (LALM) process may include a selective laser melting (SLM) process fed with a powder or film, a laser beam-powder bed fusion (LB-PBF) process fed with a powder, or a laminated object manufacturing (LOM) machining process fed with a film, for example. SLM and LB-PBF are known processes that are intended for the manufacture of three-dimensional structures, but have not been used in the field of substrate coating application because, compared to thermal spraying, these processes may be technically limited to planar applications and the application of weldable alloys to metal surfaces, and / or lack the production capacity to form coatings of several hundred microns. Similarly, the LOM machining process is known for the manufacture of three-dimensional structures, but not for substrate coating application. However, in order to address the shortcomings of known technologies in the production of patterned conductive lines, the inventors have discovered that the LALM process has a series of unique properties that can achieve a one-step processing method or additive process with higher efficiency and productivity than the existing technology.

[0033] According to an embodiment of the present invention, the SLM process uses a deposition method, which has so far only been used for weldable metal surfaces. In order to process a conductive heating circuit (14) made of a Ni-based alloy, Fe-based alloy, Al-based alloy, or Cu-based alloy on the surface of an insulating layer (13) made of aluminum oxide or other ceramic materials or glass, special measures are taken, such as: defining a set of processing parameters, preparing a process file for the circuit (14), spreading a thin layer of powder (i.e., 20μm to 120μm) onto the insulating layer (13), and starting the laser melting process. Depending on the physical properties of the deposited material and the insulating layer material, the processing parameters need to be adjusted.

[0034] The embodiment is directed to a LALM process for depositing a conductive line pattern (14) onto the surface of an insulating layer (13). This technology combines the advantages of the above technologies, such as high productivity and high reproducibility, and provides a reliable and cost-effective product while reducing the number of processing steps.

[0035] Since the LALM process does not require masking or post-processing (e.g., laser ablation) to form the conductive line pattern (14) on the insulating layer (13), such a process significantly reduces material consumption, improves the efficiency of the production process, and simplifies the production process. According to a non-limiting example, the conductive line (14), such as a Ni-based alloy, a Fe-based alloy, an Al-based alloy, or a Cu-based alloy, can be deposited by the LALM process at a thickness of 10 to 50 μm with a processing time comparable to the application speed of thermal spraying technology, such as SLM or LB-PBF using a conductive powder feed, or SLM or LOM machining using a conductive film feed. Although the processing time for material deposition may be 50 to 200% compared to atmospheric plasma spraying, these LALM processes do not require time-consuming post-processing. According to a non-limiting example, a serpentine pattern of electric tracks can be applied to a 200 mm×200 mm plate made of, for example, steel, aluminum alloy, or copper alloy by the LALM process in about 1 minute, which is several orders of magnitude faster than PVD and inkjet printing. Additionally, unlike thermal spraying techniques, these LALM processes do not require time-consuming pre-masking or time-consuming post-processing (such as laser ablation) on the substrate to form the meandering conductive patterns.

[0036] By way of non-limiting example, Figure 2An exemplary illustration of an SLM or LB-PBF process for forming a conductive trace (24) on an insulating layer (25) on a substrate (21) is shown. In this non-limiting embodiment, the substrate (21) can be, for example, a ceramic substrate, but other substrate materials (including metal substrates) can be used without exceeding the scope of the disclosed invention. However, it is noted that a bonding coating (not shown) can be selectively applied between the substrate (21) and the insulating layer (25). In the embodiment shown here, the conductive trace (24) is formed by, for example, a Ni-based, Fe-based, Al-based or Cu-based alloy powder (23) deposited onto the insulating layer (25). Although Figure 2 This is a side view, but it should be understood that the conductive circuit can be formed in a serpentine pattern. The laser (22) moves relative to the substrate (21) and can move according to a predetermined conductive circuit pattern, and emits a light beam to irradiate the alloy powder (23), causing the alloy powder (23) to melt and thereby form the conductive circuit (24).

[0037] In an embodiment, the SLM or LB-PBF process can be performed in the following manner: alloy powder (23) is distributed along a predetermined conductive line pattern, and then the alloy powder (23) is laser processed / melted to form the conductive line (24). Alternatively, the alloy powder (23) can be deposited onto the surface of the substrate (21) in the SLM or LB-PBF process, and the conductive line (24) can be formed in the following manner: the laser beam (26) melts the alloy powder (23) while the laser (22) moves relative to the substrate (21) along the predetermined conductive line pattern. In either case, it is obvious that these LALM processes do not cause material loss due to overspray. In addition, because the alloy powder (23) that has not been processed by the laser beam (26) in the LALM process remains unprocessed / unmelted in terms of its morphology or composition, the unprocessed / unmelted alloy powder (23) can be recycled after the conductive line (24) is fully formed.

[0038] In other embodiments, for example, where only a single thin layer needs to be deposited to form the electrical tracks, the conductive lines can be made by SLM using a thin metal film instead of a powder-based LALM process. Alternatively, it may be advantageous to deposit a single thin layer of electrical tracks using a LOM machining process. In a non-limiting embodiment, Figure 3A and Figure 3BThe side views of the conductive plate-type heating elements formed by the conductive film (such as Ni-based, Fe-based, Al-based or Cu-based alloy) are shown respectively. The conductive film has a thickness ranging from 10 to 50 μm and is placed on the substrate (31). The laser beam (36) is positioned and controlled to move along the thin film (33) so that the film material is melted only in the desired area, thereby forming a serpentine pattern heating line (34). Because the film material (33) is attached to the ceramic substrate only in the laser-processed area, that is, the formed heating line (34), the unprocessed area of ​​the remaining film material can be removed by, for example, compressed air, brushing or integrated stripping of the residual film, depending on the shape of the serpentine pattern. According to this embodiment, the serpentine form of the heating line (34) can be processed to have a narrow gap, for example, as low as 0.5 mm. In addition, the advantage of this embodiment is that when the laser beam heats the gas around the molten pool formed in the powder material, the risk of blowing away the conductive material near the laser spot moving along the conductive film (33) can be avoided. In addition, after the patterned heating circuit (34) formed by thin film metal is formed, if the circuit thickness needs to be increased, another thin film layer can be applied by SLM or LOM machining process, that is, the final circuit can be formed by a single film or by applying multiple thin film layers using additive process.

[0039] In addition to being more efficient in terms of material consumption, these LALM processes also consume significantly less electricity than thermal spray technologies. For example, compared to atmospheric plasma spray, electricity consumption is reduced by 10-20%; and compared to arc wire spray, it is reduced by 50-70%. Furthermore, where applicable, process gas consumption for these LALM processes is reduced by over 90% compared to atmospheric plasma spray, which uses process gases such as argon, hydrogen, helium, and mixtures thereof, which are 100% lost during the process. Consumption is even lower if some of these LALM processes can be performed in an inert gas atmosphere (such as argon or nitrogen) and / or the inert gas atmosphere can be maintained via a load lock system.

[0040] Compared to thermal spraying or inkjet printing, the conductive traces produced via LALM also have more uniform structures, avoiding hot spots caused by the non-constant resistance of the metal layer. Furthermore, the resistivity of conductive traces applied via LALM is lower than that achieved by thermal spraying and inkjet printing due to the lower oxide content and lower porosity formed during the deposition process. This allows the conductive traces to be thinner than with conventional techniques, reducing the amount of material required to fabricate them.

[0041] It should be noted that the above examples are for illustration only and should in no way be interpreted as limiting the present invention. Although the present invention has been described with reference to embodiments, it should be understood that the terms used herein are for descriptive and illustrative purposes and are not restrictive terms. Without departing from the scope and spirit of the present invention, the present invention may be adjusted in accordance with the appended claims and their amendments. Although the specific means, materials, and embodiments mentioned herein are helpful for understanding the present invention, the present invention is not limited to these specific details, and any functionally equivalent structures, methods, and applications within the scope of the appended claims are included within the scope of protection of the present invention.

Claims

1. A method for forming a circuit on a substrate, comprising: Depositing a conductive material onto the substrate itself or onto a ceramic surface overlying the substrate; and A laser beam is directed toward the conductive material on the ceramic surface, and the laser beam is moved relative to the ceramic surface along a predetermined circuit pattern, so that the conductive material is melted onto the ceramic surface to form a conductive line.

2. The method according to claim 1, wherein: The method is a Laser Additive Layer Manufacturing (LALM) process.

3. The method according to claim 1 and 2, wherein: The LALM is the Selective Laser Melting (SLM) process.

4. The method according to claim 3, wherein: The SLM process is performed in a protective atmosphere.

5. The method according to claim 4, wherein: The protective atmosphere is a protective argon atmosphere.

6. The method according to any one of the preceding claims, wherein: The conductive material includes conductive powder.

7. The method according to any one of claims 1 to 5, wherein: The conductive material includes a conductive film.

8. The method according to claims 1 and 2, wherein: The LALM is a Laser Beam Powder Bed Fusion (LB-PBF) process.

9. The method according to claim 8, wherein: The conductive material includes conductive powder.

10. The method according to claims 1 and 2, wherein: The LALM is Laminated Entity Manufacturing LOM machining.

11. The method according to claim 10, wherein: The conductive material includes a conductive film.

12. The method according to any one of the preceding claims, wherein: The predetermined circuit pattern is a meandering pattern.

13. The method according to any one of the preceding claims, wherein: Before depositing the conductive material, the method further comprises at least one of the following steps: Using the laser beam to pre-pattern the surface to which the conductive trace is to be attached, or A seed layer is applied to which the conductive tracks are to be attached.

14. The method according to any one of the preceding claims, wherein: In order to make the electric heating line fully attached, the method further comprises at least one of the following steps: reducing the intensity of the laser beam, reduce the pulse width of the laser beam, or The laser spot moving speed of the laser beam is reduced.

15. The method of claim 1, 6, 7, 9 or 11, wherein: The conductive material includes a Ni-based alloy, a Fe-based alloy, an Al-based alloy or a Cu-based alloy.

16. The method according to claim 1, wherein: The substrate is a metal substrate or a ceramic substrate.

17. The method according to claim 1, wherein: The ceramic surface is a portion of a ceramic layer formed on the substrate.

18. The method according to claim 17, wherein: The ceramic layer and the conductive tracks are components of the coating system applied to the substrate.

19. The method according to claim 18, further comprising: applying an insulating layer on the conductive line; and forming a conductive contact on the insulating layer, The insulating layer and the conductive line are components of the coating system.

20. The method according to claim 19, wherein: Prior to forming the ceramic layer on the substrate, the method further includes applying a bond coat as part of the coating system on the substrate, and wherein the ceramic layer is formed on the bond coat.

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