Hybrid 3D printing type radiator

Abstract

A heat sink (100) is described in which a fin powder (122) placed directly on a substrate (140) is mixed 3D printed using laser powder bed melting (LPBF) or selective laser melting (SLM) (200) for the fin (120). The fin powder (122) forms a powder bed, the height of which increases layer by layer, and the fins (120) are built layer by layer by laser melting and melting the fin powder (122). The fin powder (122) may be copper, a copper alloy, aluminum, or an aluminum alloy, while the associated substrate (140) is copper-based or aluminum-based. The substrate (140) is prepared by conventional processing, so the process (200) is referred to as a hybrid LPBF or SLM. The obtained radiator (100) has excellent heat dissipation and temperature stability performance.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] The present invention claims priority from Singapore patent application no. 10202202742X filed on March 18, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to hybrid 3D printing of a heat sink. In particular, fins of the heat sink are manufactured by 3D printing using laser powder bed fusion (LPBF) or more generally selective laser melting (SLM), wherein the fins are formed of copper or aluminum. Background Art

[0004] The heat sink is used to cool the electrical or electronic components thermally connected to the heat sink. Traditionally, the heat sink is formed by extrusion, powder metallurgy, processing such as EDM, etc.

[0005] Extruded heat sinks have simple fin geometry, but the fin size is relatively large; therefore, the fin size limits the surface area available for heat dissipation. Powder metallurgy, as disclosed in patent publication US20050252637 to Hon Hai Precision Industry Co., Ltd., appears to be suitable for producing heat sinks with finer fin geometries. Due to the need to improve heat sink performance, attempts have been made to manufacture the fins by using electrical discharge machining (EDM); however, EDM is a very slow process; EDM is also fraught with manufacturing limitations because the EDM wire often breaks. When the EDM-machined fins are attached to a substrate, the attachment interface causes resistance to heat flow from the substrate to the fins.

[0006] Therefore, it can be seen that a new method for manufacturing a heat sink is needed that provides more effective heat dissipation than conventionally available heat sinks. Preferably, such a method is cost-effective and suitable for large-scale production. Summary of the invention

[0007] In order to provide a basic understanding of the present invention, a simplified description is given below. This summary is not a broad overview of the present invention, nor is it intended to identify key features of the present invention. Instead, it is to present some inventive concepts of the present invention in a summarized form, as a prior explanation for the detailed description below.

[0008] The present invention seeks to provide a new type of heat sink that provides effective heat dissipation and a new process for manufacturing these heat sinks. The new process involves hybrid 3D printing of the fins of the heat sink, which is processed by laser powder bed fusion or selective laser melting of the fin powder on the processed substrate. The new process has been tested and the heat sink obtained has excellent heat dissipation performance.

[0009] In one embodiment, the present invention provides a heat sink comprising: a substrate; and a plurality of fins (fins), wherein a first layer of each fin is formed directly on the substrate using a laser powder bed melting (LPBF) or selective laser melting (SLM) process on fin powder placed on the substrate, wherein laser melting is used to build up the fins layer by layer to reach a predetermined height.

[0010] Preferably, the fins are made of CuCrZr, copper alloy powder or pure copper powder, and the substrate is processed from a copper-based material. In another embodiment, the fins are made of aluminum or aluminum alloy powder, and the substrate is processed from an aluminum-based material.

[0011] Preferably, the fins have a height to thickness ratio of substantially 4-20 and a height to pitch ratio of substantially 4-35.

[0012] Preferably, the fins are configured with a parallelogram cross-sectional shape or geometric shape. The fins are arranged in rows, and the row spacing is substantially equal to or greater than the inclined spacing between adjacent fins in the row.

[0013] Preferably, the base plate is provided with threaded holes for mounting a protective cover above or around the fins. The base plate is also provided with holes for mounting the heat sink to a component requiring heat dissipation.

[0014] In another embodiment, the present invention provides an LPBF or SLM method for hybrid 3D printing manufacturing of a heat sink, comprising: forming a substrate using conventional (conventional) subtractive processing; forming a powder bed of fin powder above the substrate; operating a laser to melt and fuse particles of the fin powder to build a first layer of the fin directly on the substrate; and adding fin powder to increase the height of the powder bed layer by layer, operating the laser to melt the fin powder to build the fin layer by layer until the fin reaches a predetermined height.

[0015] Preferably, the step of operating the laser to build the fins layer by layer comprises generating a pattern of fin geometry by a CAD or computer system and outputting the pattern to a scanner to direct a laser beam from the laser onto the fin powder. The pattern comprises fins in rows, each fin forming a parallelogram shape, and adjacent fins in the row are spaced apart at the hypotenuse of the parallelogram. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is described by way of non-limiting embodiments thereof with reference to the accompanying drawings, in which:

[0017] FIG1 shows the structure of a conventional radiator;

[0018] Figure 2 shows a plan view of a heat sink obtained according to an embodiment of the present invention; Figure 3Shows Figure 2 The fin profile of the heat sink is shown, while Figure 4 shows a side view of the heat sink, and Figure 5 A photograph showing a portion of a radiator;

[0019] Figure 6-8 The performance of the above heat sink and the control heat sink obtained by wire EDM are shown. Fig. 9 shows the thermal properties of the copper-based alloy used to make the above heat sink compared to the thermal properties of copper; and

[0020] Fig.10 A hybrid 3D printing method for manufacturing the above heat sink according to another embodiment of the present invention is shown. Fig.11 The layer-by-layer build-up of the 3D wing printing described above is shown. DETAILED DESCRIPTION

[0021] One or more specific and alternative embodiments of the present invention will now be described with reference to the accompanying drawings. However, it should be clear to those skilled in the art that the present invention can be implemented without these specific details. In order not to make the present invention unclear, some details may not be described in detail.

[0022] FIG. 1 shows the structure of a conventional heat sink 10. As shown, the conventional heat sink 10 has a plurality of fins 20. The fins 20 are attached to a substrate 40 via an adhesion interface layer (adhesion interface layer) 30 (which may be made of thermal adhesive, epoxy resin or solder); alternatively, the fins 20 may be attached to the substrate 40 using mechanical elements (such as screws), but this may result in an interface joint. As discussed in the background art, the fins 20 have a relatively large size, so the surface area for heat dissipation is limited. Even if the heat sink with the fins 20 is EDM wire cut (such an EDM wire cut heat sink is now labeled 10a), the adhesion interface layer 30 or the interface joint may result in resistance to heat flow from the substrate 40 to the fins 20.

[0023] Now, refer to Figure 2 and Figure 5, which shows a heat sink 100 of the present invention according to one embodiment. As shown, the heat sink 100 is composed of a plurality of fins 120 extending from a base plate 140. In one embodiment, the fins 120 have a very fine geometry and are made by melting and 3D printing a copper alloy powder 122 to extend directly from the copper-based base plate 140. In one embodiment, the copper alloy powder 122 is composed of CuCrZr, and the base plate 140 is a copper-based material, including a copper alloy. In another embodiment, the fins 120 are made of aluminum or aluminum alloy powder, and the base plate 140 is an aluminum-based material. In both embodiments, the fins 120 are 3D printed directly on the substrate 140 using copper, copper alloy, aluminum or aluminum alloy powder 122 by laser powder bed fusion (LPBF) or more generally selective laser melting (SLM) 200, while the substrate 140 is formed by conventional subtractive machining (e.g., milling, grinding, etc.); therefore, the heat sink 100 manufacturing is described as hybrid 3D printing using LPBF or SLM process 200 to form the fins 120 directly on the substrate 140. Other types of copper, copper alloy powders, aluminum, aluminum alloy powders, copper-based and aluminum-based substrates with excellent thermal conductivity can be used. LPBF or SLM 200 such as Fig.10 As shown, this will become clearer after describing the heat sink 100 and its thermal performance.

[0024] like Figure 2 As shown, holes H1 and H2 for mounting are formed on the base plate 140. When the heat sink 100 is put into use, the hole H1 (preferably with threads) is configured to mount a protective cover around or above the fin 120. The hole H2 is configured to mount the heat sink 100 to an electrical or electronic component to be cooled.

[0025] Figure 3 1 shows an exploded view of the fin 120 as viewed from above; in other words, Figure 3 The profile of the fins 120 is shown in plan view. In one embodiment, the fins 120 are parallelograms in plan view or cross-sectional view, having a longitudinal dimension S, a thickness T, a tilt pitch V, and a tilt angle α; the fins 120 are arranged in straight rows in the longitudinal S direction, but the rows are spaced apart by a dimension U. In one embodiment, the dimensions S, T, V, and U are substantially 1.4, 0.5, 0.3, and 0.5, respectively. The dimension S can vary from about 1 mm to several millimeters, and the tilt angle α can range from about 90 degrees to about 10 degrees. The size and spacing of the fins 120 or the fin geometry are not numerically limited, but are selected based on the heat dissipation performance and / or limitations of the design of the LPBF or SLM process 200.

[0026] Figure 4 Shows Figure 3 The height projection of the wing 120 is shown. Figure 4 As shown, the height of the fin 120 is represented by Y1, and the thickness of the base plate 140 is represented by Y2. The thickness Y2 can be selected to minimize any warping of the flatness of the heat sink after manufacturing. The height dimensions Y1, Y2 can range from about 2 mm to about 10 mm, and also depend on the heat dissipation performance and / or limitations of the design of the LPBF or SLM process 200. According to the above dimensions, the fin 120 is characterized by having a height-to-thickness ratio of substantially 4 to 20, and a height-to-pitch ratio of substantially 4 to 35.

[0027] Figure 6-8 The heat dissipation and pressure drop performance of the heat sink 100 and a control heat sink 12 formed entirely by wire EDM are shown. The control heat sink 12 is made of copper and has fin and base geometry similar to the heat sink 100 of the present invention. In the comparative study, the two heat sinks 12, 100 were installed on a CPU, and the CPU was operated at various water convection rates at 100% load. Figure 6 As shown in FIG. 1 , the hybrid 3D printed heat sink 100 reduces the CPU temperature. However, due to the high surface roughness of the 3D printed fins 120, as shown in FIG. Figure 7 As shown, the pressure drop of water flowing through the hybrid 3D printed heat sink 100 is higher than the pressure drop of water flowing through the heat sink 12. However, since the hybrid 3D printed heat sink 100 has a better cooling performance, the resulting pressure drop loss is reasonable. Figure 8 As shown, when evaluated using thermal resistance versus pump power characteristics, the hybrid 3D printed heat sink 100 exhibits higher overall performance than the control heat sink 12 .

[0028] Fig. 9 Some physical properties of the CuCrZr material 122 compared to copper are shown. It can be seen that despite the lower thermal conductivity of CuCrZr 122 (about 15-23% lower than copper), the heat sink 100 is as effective in dissipating heat as the copper heat sink 12 of the control group. The inventors believe that melting the fin powder 122 directly onto the substrate 140 through the LPBF or SLM process 200 can produce continuous material integrity between the substrate 40 and the fins 120. The inventors also believe that the tiny size of the fin powder 122 (a large range of about 20-70 μm) allows the fin powder 122 to melt and fuse to build continuous material integrity layer by layer within each fin 120. Continuous material integrity can mean that there are no voids, interfaces, or harmful defects that reduce heat conduction from the substrate 140 to the fin 120 or within the fin 20.

[0029] Now, refer to Fig.10, which is a schematic diagram of an LPBF or SLM process 200 according to another embodiment of the present invention. The LPBF or SLM process 200 shown is used to illustrate and describe a method for manufacturing a heat sink 100. As shown, a machine using the LPBF or SLM process 200 includes a powder supply station 210 disposed adjacent to a production station 220. The powder supply station 210 has a supply chamber 212, which is filled with fin powder 122 during use, and a supply piston 214 is operable to gradually supply the fin powder 122 upward. At the production station 220, the substrate 140 is installed in the production chamber 222, which is located above the production piston 224; during the manufacture of the heat sink 100, the production piston 224 is operable to move downward in a stepwise manner in coordination with the stepping movement of the supply piston 214. The tops of the powder supply station 210 and the production station 220 are aligned with each other. During the preparation process, the supply piston 214 is lifted, and the blade 240 is operated to scrape the top of the powder supply chamber 212 to reach the production chamber 222 to fill the gap around the substrate 140 installed in the production chamber 222. The preparation process can be repeated several times until the wing powder 122 is placed to a predetermined height (e.g., 0.05 mm) above the substrate 140, thereby forming a laser powder bed (LPB) in the production chamber 222; then the blade 240 is brought to the original position to the far left of the powder supply station 210. Any excess wing powder 122 is pushed into the overflow chamber 230 located near the production station 220.

[0030] To form the first layer of the fin 120 directly on the substrate 140, the laser element 260 is turned on, and the emitted laser beam 262 is reflected and scanned by the scanner 270 to impact the fin powder 122, causing the fin powder 112 to melt and the powder particles to fuse together, such as Fig.10 As shown. As the laser beam 262 is passed through and controlled by the scanner 270 according to the airfoil geometry, the airfoil powder 122 melts and melts to form the first layer of the airfoil 120 directly on the substrate 140. To form the second layer, the supply piston 214 is raised in a coordinated manner, and the production piston 224 is lowered in a coordinated manner, and then the blade 240 is moved to scrape the layer of airfoil powder 122 from the supply chamber 212 to the production chamber 222. The SLM process 200 continues to build the airfoil 120 layer by layer to the desired height Y1 in a manner similar to 3D additive printing. In another configuration of the LPBF or SLM process 200, each layer of the airfoil 120 can be formed by multiple passes of the laser beam 262, depending on the size and power of the laser beam 62. In addition, the airfoil geometry can be generated by a CAD or computer system, and the output is linked to the scanner 270, thereby directing the laser beam 262 onto the airfoil powder 122 and mechanizing or automating the process 200.

[0031] Fig.11The three-layered wing 120 is shown as the LPBF or SLM process 200 continues. As shown, as the laser beam 262 scans across the laser powder bed in the production chamber 222, the laser beam 262 produces a molten pool 124 of the wing powder 122; Fig.11 , as the laser beam 262 scans, the molten pool 124 solidifies to form the third layer 120 - 3 of the fin 120 . For illustration, Fig.11 A three-layered fin 120 is shown that is built up successively layer by layer.

[0032] The above-described LPBF or SLM process 200 for manufacturing the heat sink 100 has many advantages over known manufacturing methods. For example, as described above, the hybrid 3D printed heat sink 100 has similar or better cooling performance and higher temperature stability than the EDM wire cut heat sink 12. Other advantages are: no post-processing is required compared to traditional metal 3D printing, because traditional 3D printing requires the manufactured parts to be removed from the substrate. When compared to the EDM wire cut heat sink 12, no subtractive manufacturing process is involved for forming the fins 120, thus saving material because no material is wasted except for the subtractive machining process for forming the substrate 140. This hybrid LPBF or SLM process 200 is also a faster process than EDM wire cutting. In addition, this hybrid LPBF or SLM process 200 is suitable for batch manufacturing and higher throughput, making this hybrid process 200 more economical or efficient in producing heat sinks 100 with fine fin geometries and fine pitches.

[0033] Although specific embodiments have been described and illustrated, it should be understood that many changes, modifications, variations, and combinations of variations disclosed in the text description and drawings may be made to the invention without departing from the scope of the invention. For example, two or more laser elements 260 may be employed to increase the speed of the hybrid 3D printing manufacturing described above. When the hybrid LPBF or SLM process 200 uses aluminum-based fin powder, a non-oxidizing environment may be provided around the production chamber 222.

Claims

1. A heat sink, wherein: The radiator comprises: substrate; and A plurality of fins are provided, and a first layer of each fin is formed directly on the substrate using a laser powder bed fusion (LPBF) or selective laser melting (SLM) process on fin powder placed on the substrate, wherein the plurality of fins are built up layer by layer by laser melting to reach a predetermined height.

2. The heat sink according to claim 1, wherein: The wing powder is selected from: CuCrZr, pure copper, copper alloy, aluminum or aluminum alloy.

3. The radiator according to claim 1 or 2, wherein: The substrate is made of a material selected from copper, copper alloy, aluminum or aluminum alloy.

4. A heat sink according to any one of the preceding claims, wherein: Each of the plurality of fins has a height to thickness ratio of substantially 4-20.

5. A heat sink according to any one of the preceding claims, wherein: Each of the plurality of fins has a height to pitch ratio of substantially 4 to 35.

6. A heat sink according to any one of the preceding claims, wherein: Each of the plurality of fins is configured with a parallelogram cross-sectional shape or geometric shape.

7. The heat sink according to claim 6, wherein: The plurality of fins are arranged in rows, wherein a row spacing is substantially equal to or greater than an oblique spacing between adjacent fins in a row.

8. A heat sink according to any one of the preceding claims, wherein: Also included are a plurality of threaded holes for mounting a protective cover over or around the plurality of fins.

9. A heat sink according to any one of the preceding claims, wherein: The substrate also includes a plurality of holes, which are used to mount the substrate to a component requiring heat dissipation.

10. A laser powder bed fusion (LPBF) or selective laser melting (SLM) method for hybrid 3D printing manufacturing of a heat sink, the method comprising: Forming the substrate using conventional subtractive machining; forming a powder bed of wing powder above the substrate; operating a laser to melt and fuse particles of the airfoil powder to build a first layer of the airfoil directly on the substrate; adding the fin powder to increase the height of the powder bed layer by layer; and The laser is operated to melt the airfoil powder to build up the airfoil layer by layer until the airfoil reaches a predetermined height.

11. The method according to claim 10, wherein: The step of operating the laser to build up the airfoil layer by layer includes generating a pattern of the airfoil geometry by a CAD or computer system and outputting the pattern to a scanner to direct a laser beam from the laser onto the airfoil powder.

12. The method according to claim 11, wherein: The pattern comprises rows of the fins, each fin forming a parallelogram shape, and adjacent fins in a row are spaced apart at the hypotenuse of the parallelogram.

13. A heat sink, wherein: The heat sink according to any one of claims 1-9 is obtained by the hybrid 3D manufacturing method according to claims 10-12.

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