Modified gold-tin-plated hard gold heat sink material and preparation method and application thereof

Abstract

This invention relates to the field of heat sink materials, specifically to a modified gold-tin-hard gold-plated heat sink material, its preparation method, and its application. The modified gold-tin-hard gold-plated heat sink material comprises, from bottom to top, a first heat sink layer, a nickel plating layer, a gold plating layer, a gold-tin solder layer, another gold plating layer, a nickel plating layer, a second heat sink layer, a nickel plating layer, a hard gold plating layer, and a modified gold-tin-silicon solder layer. The first heat sink layer is oxygen-free copper, and the second heat sink layer is either molybdenum copper or tungsten copper. The hard gold plating layer comprises, from bottom to top, a nickel plating layer and a tungsten-titanium gold plating layer. This invention introduces tungsten and titanium into the gold plating layer on the surface of the heat sink material, significantly enhancing the hardness and corrosion resistance of the gold plating layer; it incorporates a small amount of silicon into the gold-tin solder, improving the ductile processing performance of the brittle gold-tin solder; and it achieves one-time molding of the solder-heat sink composite material through vacuum hot-press welding, reducing voids or overflow problems caused by solder dimensional errors during welding.

Description

Technical Field

[0001] This invention relates to the field of heat sink materials technology, specifically to a modified gold-tin-plated hard gold heat sink material, its preparation method, and its application. Background Technology

[0002] In the field of modern electronics, high-power optoelectronic devices are widely used in various high-tech products due to their excellent performance. However, these devices generate a large amount of heat during operation, and if heat cannot be dissipated in time, it will seriously affect their stability and reliability. To improve the heat dissipation performance of these devices, the packaging structure typically employs a design where a ceramic chip is covered with a heat sink material. This packaging structure mainly consists of a bottom heat sink, a ceramic chip, interconnect interfaces, and other layered structures, ensuring that heat can be effectively conducted and dissipated.

[0003] Gold-tin solder is widely used as a bonding solder between ceramic chips and heat sink materials in the packaging process of high-power devices due to its good electrical and thermal conductivity, high melting point, anti-electromigration ability and easy soldering. It can effectively transfer the heat generated on the ceramic chip to the heat sink material and then dissipate it into the environment, ensuring the stable operation of the device.

[0004] However, the gold-tin solder connection method currently used in the packaging of high-power devices still faces many challenges. On the one hand, when using pre-formed gold-tin solder for pressure welding, the brittleness and difficulty in deformation of gold and tin materials, coupled with the relative scarcity of high-quality domestic products, make it difficult to guarantee post-soldering reliability. Simultaneously, pre-formed solder pads are prone to dimensional errors during processing, leading to mismatches between the pads and heat sink specifications, resulting in post-soldering issues such as edge voids or solder overflow, posing a risk of desoldering or short circuits. On the other hand, while physical vapor deposition (PVD) can address solder connection issues to some extent by separately plating gold and tin layers onto the ceramic substrate and heat sink, this method suffers from difficulties in controlling the uniformity of solder composition. Furthermore, the entire deposition process is relatively complex, requiring significant time and cost. More importantly, for heat sink materials with high hardness, such as tungsten copper and molybdenum copper, the surface gold plating layer has relatively low hardness, making it prone to scratches during use, leading to material failure and severely impacting device reliability and lifespan. Summary of the Invention

[0005] To address the problems of unreliability of gold-tin solder after pressure welding and difficulty in controlling the uniformity of physical vapor deposition solder composition in the prior art, this invention provides a modified gold-tin-hard gold plating heat sink material, its preparation method, and its application. By modifying the gold-tin solder, the processing performance of brittle gold-tin solder is improved. The solder-heat sink composite material is formed in one step through vacuum hot pressing welding, thereby improving the accuracy and reliability of solder coverage.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A modified gold-tin-hard gold plating heat sink material includes, from bottom to top, a first heat sink layer, a nickel plating layer, a gold plating layer, a gold-tin solder layer, a gold plating layer, a nickel plating layer, a second heat sink layer, a nickel plating layer, a hard gold plating layer, and a modified gold-tin-silicon solder layer; the first heat sink layer is oxygen-free copper, the second heat sink layer is one of molybdenum copper or tungsten copper, and the hard gold plating layer includes a tungsten-titanium gold plating layer.

[0008] Furthermore, the chemical composition of the modified gold-tin-silicon solder layer includes, by weight percentage: 19-21% tin, 1-2% silicon, and the remainder gold; the thickness of the modified gold-tin-silicon solder layer is 0.025-0.05 mm.

[0009] Furthermore, the chemical composition of the gold-tin solder layer includes, by weight percentage: 19-21% tin, with the remainder being gold; the thickness of the gold-tin solder layer is 0.025-0.05 μm.

[0010] Furthermore, the thickness of the nickel plating layer, the gold plating layer, and the hard gold plating layer is 3-5 μm.

[0011] This invention also includes the following technical solutions:

[0012] A method for preparing a modified gold-tin-plated hard gold heat sink material includes the following steps:

[0013] (1) Hot-roll gold-tin solder and modified gold-tin-silicon solder at 240-255℃ respectively to obtain gold-tin solder sheets and modified gold-tin-silicon solder sheets;

[0014] (2) A nickel layer and a gold layer are sequentially plated on the upper surface of oxygen-free copper; a nickel layer and a tungsten titanium gold layer are sequentially plated on the upper surface of molybdenum copper or tungsten copper; a nickel layer and a gold layer are sequentially plated on the lower surface of molybdenum copper or tungsten copper; the nickel layer is electroplated, and the gold layer and the tungsten titanium gold layer are magnetron sputtered.

[0015] (3) The materials processed in steps (1) and (2) are placed from bottom to top in the order of oxygen-free copper, gold-tin solder sheet, molybdenum copper or tungsten copper and modified gold-tin silicon solder sheet, and placed in a vacuum eutectic furnace for hot pressing welding at 300-320℃ for 30-60s. After cooling, the modified gold-tin-hard gold heat sink material is obtained.

[0016] Further, the feature is that, in step (2), the tungsten-titanium gold layer is sputtered by sputtering with a tungsten-titanium target and a gold target, and the titanium content in the tungsten-titanium target is 10-20%.

[0017] This invention also includes the following technical solutions:

[0018] A modified gold-tin-plated hard gold heat sink material for use in high-power devices.

[0019] The mechanism involved in this invention is as follows:

[0020] Introducing tungsten and titanium into the metal coating on the surface of heat sink materials can significantly enhance the hardness and adhesion of the metal coating due to the high hardness of tungsten itself. Adding titanium can improve the corrosion resistance of the metal coating and improve the wettability of the metal layer with carbide, nitride and other ceramic chips by utilizing the activity of titanium, thereby improving the welding bond strength in subsequent use.

[0021] Adding trace amounts of silicon to gold-tin alloys results in the preferential formation of the δ-AuSn phase (AuSi phase) during solidification, which provides a nucleation basis, refines coarse primary phases, and improves the alloy's ductile processing performance. The silicon in the modified gold-tin-silicon solder and the tungsten in the tungsten-titanium gold layer can combine to form the WSi phase, improving the solder's compatibility with the hard gold heat sink and reducing the formation of hard W particles between solder layers, thus enhancing weld bonding strength. The melting point of gold-tin alloys is extremely sensitive to composition. During welding, gold elements in the tungsten-titanium gold plating diffuse into the modified gold-tin-silicon solder, altering its composition. The increased gold content and the closer the composition of the modified gold-tin-silicon solder to the eutectic point lead to a hypoeutectic structure, improving solder fluidity and wettability, aligning the solid-liquid phase lines, narrowing the melting range, and accelerating solidification. This reduces the occurrence of cold solder joints and improves welding reliability.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention provides a modified gold-tin-hard gold-plated heat sink material, its preparation method, and its application. By introducing tungsten and titanium into the gold plating layer on the surface of the heat sink material, the hardness of the gold plating layer is significantly enhanced, effectively reducing the risk of scratches during use and extending the service life of the heat sink material. Simultaneously, the corrosion resistance of the gold plating layer is improved. By incorporating a small amount of silicon into the gold-tin solder, the ductile processing performance of the brittle gold-tin solder is improved. The solder-heat sink composite material is formed in one step using vacuum hot-press welding, improving the accuracy of solder coverage and reducing voids or overflow problems caused by solder size errors during welding. The tungsten-copper or molybdenum-copper heat sink material used improves the bonding force between the heat sink substrate and the tungsten-titanium gold plating layer, ensuring the compatibility between the heat sink material and the chip. Furthermore, the addition of oxygen-free copper heat sink improves heat dissipation efficiency, making the heat sink material more suitable for use in high-power devices such as SiC. Attached Figure Description

[0024] The embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

[0025] Figure 1 A schematic diagram of an embodiment of the modified gold-tin-hard gold-plated heat sink material is shown;

[0026] Figure 2 A metallographic image of Example 1 is shown;

[0027] The attached diagram is labeled as follows: 1-First heat sink layer, 2-Nickel plating layer, 3-Gold plating layer, 4-Gold-tin solder layer, 5-Second heat sink layer, 6-Tungsten-titanium-gold plating layer, 7-Modified gold-tin-silicon solder layer. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] Example 1

[0030] Gold-tin solder and modified gold-tin-silicon solder were hot-rolled at 240℃ to obtain gold-tin solder sheets and modified gold-tin-silicon solder sheets, respectively. Nickel layers were electroplated on the upper surface of oxygen-free copper and the lower surface of molybdenum copper, followed by magnetron sputtering of a gold layer. Nickel layers were electroplated on the upper surface of molybdenum copper, followed by magnetron sputtering of a tungsten-titanium target with a titanium content of 10% and a gold target. The oxygen-free copper, gold-tin solder sheets, molybdenum copper and modified gold-tin-silicon solder sheets were placed in the order of bottom to top and placed in a vacuum eutectic furnace. A vacuum was drawn, nitrogen gas was introduced into the vacuum eutectic furnace, and hot-press welding was performed at 320℃ for 30s. After cooling, modified gold-tin-hard gold-plated heat sink material was obtained.

[0031] In this embodiment, the gold-tin solder layer contains 19% tin and has a thickness of 0.025 μm; the modified gold-tin-silicon solder layer contains 19% tin and 1% silicon and has a thickness of 0.05 mm; the nickel layer, gold layer and tungsten-titanium gold layer have a thickness of 3 μm.

[0032] Example 2

[0033] Gold-tin solder and modified gold-tin-silicon solder were hot-rolled at 255℃ to obtain gold-tin solder sheets and modified gold-tin-silicon solder sheets, respectively. Nickel layers were electroplated on the upper surface of oxygen-free copper and the lower surface of tungsten copper. Then, a tungsten-titanium gold layer was magnetron sputtered using a tungsten-titanium target with a titanium content of 20% and a gold target. A nickel layer was electroplated on the upper surface of tungsten copper, followed by magnetron sputtering of a tungsten-titanium gold layer. The oxygen-free copper, gold-tin solder sheets, molybdenum copper, and modified gold-tin-silicon solder sheets were placed in the order of bottom to top and placed in a vacuum eutectic furnace. A vacuum was drawn, nitrogen gas was introduced into the vacuum eutectic furnace, and hot-press welding was performed at 300℃ for 60s. After cooling, modified gold-tin-hard gold-plated heat sink material was obtained.

[0034] In this embodiment, the gold-tin solder layer contains 21% tin and has a thickness of 0.05 μm; the modified gold-tin-silicon solder layer contains 21% tin and 2% silicon and has a thickness of 0.025 mm; the nickel layer, gold layer and tungsten-titanium gold layer have a thickness of 5 μm.

[0035] This invention provides a modified gold-tin-hard gold-plated heat sink material, its preparation method, and its application. By introducing tungsten and titanium into the gold plating layer on the surface of the heat sink material, the hardness of the gold plating layer is significantly enhanced, effectively reducing the risk of scratches during use and extending the service life of the heat sink material. Simultaneously, the corrosion resistance of the gold plating layer is improved. By incorporating a small amount of silicon into the gold-tin solder, the ductile processing performance of the brittle gold-tin solder is improved. The solder-heat sink composite material is formed in one step using vacuum hot-press welding, improving the accuracy of solder coverage and reducing voids or overflow problems caused by solder size errors during welding. The tungsten-copper or molybdenum-copper heat sink material used improves the bonding force between the heat sink substrate and the tungsten-titanium gold plating layer, ensuring the compatibility between the heat sink material and the chip. Furthermore, the addition of oxygen-free copper heat sink improves heat dissipation efficiency, making the heat sink material more suitable for use in high-power devices such as SiC.

[0036] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in a suitable manner, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A modified gold-tin-plated hard gold heat sink material, characterized in that, It includes, from bottom to top, a first heat sink layer (1), a nickel plating layer (2), a gold plating layer (3), a gold-tin solder layer (4), a gold plating layer (3), a nickel plating layer (2), a second heat sink layer (5), a nickel plating layer (2), a hard gold plating layer (6), and a modified gold-tin-silicon solder layer (7); the first heat sink layer (1) is an oxygen-free copper layer, the second heat sink layer (5) is a molybdenum copper layer or a tungsten copper layer, and the hard gold plating layer includes a tungsten-titanium gold plating layer; The tungsten-titanium-gold coating is sputtered using a tungsten-titanium target and a gold target, wherein the titanium content in the tungsten-titanium target is 10-20%. The chemical composition of the modified gold-tin-silicon solder layer (7) by weight percentage includes: 19-21% tin, 1-2% silicon, and the remainder is gold.

2. The modified gold-tin-plated hard gold heat sink material according to claim 1, characterized in that, The thickness of the modified gold-tin-silicon solder layer (7) is 0.025-0.05 mm.

3. The modified gold-tin-plated hard gold heat sink material according to claim 1, characterized in that, The chemical composition of the gold-tin solder layer (4) by weight percentage includes: 19-21% tin, and the remainder is gold.

4. The modified gold-tin-plated hard gold heat sink material according to claim 1, characterized in that, The thickness of the nickel plating layer (2), the gold plating layer (3) and the hard gold plating layer (6) is 3-5 μm.

5. A method for preparing the modified gold-tin-plated hard gold heat sink material according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Gold-tin solder and modified gold-tin-silicon solder are hot-rolled at 240-255℃ respectively to obtain gold-tin solder sheets and modified gold-tin-silicon solder sheets; (2) A nickel layer and a gold layer are sequentially plated on the upper surface of the oxygen-free copper layer; a nickel layer and a tungsten titanium gold layer are sequentially plated on the upper surface of the molybdenum copper layer or the tungsten copper layer; and a nickel layer and a gold layer are sequentially plated on the lower surface of the molybdenum copper layer or the tungsten copper layer; the nickel layer is electroplated, and the gold layer and the tungsten titanium gold layer are magnetron sputtered. (3) The materials processed in steps (1) and (2) are placed from bottom to top in the order of oxygen-free copper layer, gold-tin solder sheet, molybdenum copper layer or tungsten copper layer and modified gold-tin silicon solder sheet, and placed in a vacuum eutectic furnace for hot pressing welding at 300-320℃ for 30-60 s. After cooling, the modified gold-tin-hard gold heat sink material is obtained.

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