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

Abstract

The invention relates to the technical field of heat sink materials, in particular to a modified gold tin-hard gold plated heat sink material and a preparation method and application thereof. Comprising 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 which are sequentially connected from bottom to top. The first heat sink layer is made of oxygen-free copper, the second heat sink layer is made of molybdenum copper or tungsten copper, and the hard gold plating layer comprises a nickel plating layer and a tungsten titanium gold plating layer which are sequentially connected from bottom to top. Tungsten and titanium are introduced into the gold-plated layer on the surface of the heat sink material, so that the hardness and corrosion resistance of the gold-plated layer are remarkably enhanced; a small amount of silicon is doped into the gold-tin solder, so that the shaping processing performance of the gold-tin brittle solder is improved; one-time forming of the solder-heat sink composite material is achieved in a vacuum thermocompression welding mode, and the problem of cavities or overflow caused by solder size errors in the welding process is solved.

Description

Technical Field

[0001] The invention relates to the technical field of heat sink materials, and in particular to a modified gold-tin-hard gold-plated heat sink material and a preparation method and application thereof. Background Art

[0002] In the field of modern electronic technology, high-power optical and electrical devices are widely used in various high-tech products due to their excellent performance. However, these devices generate a lot of heat when working. If the heat cannot be dissipated in time, it will seriously affect their stability and reliability. In order to improve the heat dissipation performance of the device, the packaging structure usually adopts a design in which a heat sink material is covered on a ceramic chip. This packaging structure is mainly composed of a bottom heat sink, a ceramic chip, an interconnect interface and other layer structures to ensure that the heat can be effectively conducted and dissipated.

[0003] Gold-tin solder is widely used as a connecting solder between ceramic chips and heat sink materials in the packaging process of high-power devices because of its good electrical conductivity, thermal conductivity, high melting point, resistance to electromigration and easy welding. 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 current gold-tin solder connection method used in the packaging process of high-power devices still faces many challenges. On the one hand, when using preformed gold-tin solder for pressurized welding, due to the brittleness of the gold-tin material itself and the difficulty in deformation processing, there are relatively few high-quality domestic products, which makes it difficult to ensure the reliability after welding. At the same time, the preformed solder sheet is prone to dimensional errors during the processing process, which makes the solder sheet and the heat sink specifications mismatch, and then there are problems such as post-welding edge voids or solder overflow, causing the risk of desoldering or short circuit. On the other hand, the connection between the ceramic sheet and the heat sink is achieved by plating gold and tin layers respectively by physical vapor deposition. Although it can solve the problem of solder connection to a certain extent, this method has the problem of difficult control of the uniformity of the solder composition. In addition, the entire deposition process is relatively complicated and requires a lot of time and cost. More importantly, for heat sink materials with higher hardness such as tungsten copper and molybdenum copper, the hardness of the surface gold plating layer is low, which is easy to be scratched during use, resulting in material failure, seriously affecting the reliability and service life of the device. Summary of the invention

[0005] In view of the problems in the above-mentioned prior art that it is difficult to ensure the reliability of gold-tin solder after pressurized welding and it is difficult to control the uniformity of physical vapor deposition solder composition, the present invention provides a modified gold-tin-hard gold-plated heat sink material and a preparation method and application thereof. By modifying the gold-tin solder, the processing performance of the gold-tin brittle solder is improved, and the one-time forming of the solder-heat sink composite material is achieved through vacuum hot pressing welding, thereby improving the accuracy and reliability of solder coverage.

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

[0007] A modified gold-tin-hard gold-plated heat sink material comprises a first heat sink layer, a nickel-plated layer, a gold-plated layer, a gold-tin solder layer, a gold-plated layer, a nickel-plated layer, a second heat sink layer, a nickel-plated layer, a hard gold-plated layer and a modified gold-tin-silicon solder layer connected in sequence from bottom to top; 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-plated layer comprises 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 rest 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 and the rest 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] The present invention also includes the following technical solutions:

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

[0013] (1) hot rolling the gold-tin solder and the modified gold-tin-silicon solder at 240-255° C. to obtain a gold-tin solder sheet and a modified gold-tin-silicon solder sheet;

[0014] (2) a nickel layer and a gold layer are plated in sequence on the upper surface of oxygen-free copper; a nickel layer and a tungsten-titanium-gold layer are plated in sequence on the upper surface of molybdenum-copper or tungsten-copper, and a nickel layer and a gold layer are plated in sequence on the lower surface of molybdenum-copper or tungsten-copper; the nickel layer is plated by electroplating, and the gold layer and the tungsten-titanium-gold layer are plated by magnetron sputtering;

[0015] (3) placing the materials processed in step (1) and step (2) in the order of oxygen-free copper, gold-tin solder sheet, molybdenum-copper or tungsten-copper and modified gold-tin-silicon solder sheet from bottom to top, and placing them in a vacuum eutectic furnace at 300-320° C. for 30-60 seconds for hot pressing welding, and obtaining a modified gold-tin-hard gold-plated heat sink material after cooling.

[0016] Furthermore, it is characterized in that in step (2), the tungsten-titanium-gold layer is co-sputtered by using a tungsten-titanium target and a gold target, and the titanium content in the tungsten-titanium target is 10-20%.

[0017] The present invention also includes the following technical solutions:

[0018] A modified gold-tin-hard gold-plated heat sink material is used for high-power device applications.

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

[0020] Tungsten and titanium are introduced into the metal coating on the surface of the heat sink material. Since tungsten itself has a high hardness, the addition of tungsten can significantly enhance the hardness and bonding strength of the metal coating. The addition of titanium can improve the corrosion resistance of the metal coating, and utilize the activity of titanium to improve the wettability of the metal layer with ceramic chips such as carbides and nitrides, thereby improving the welding bonding strength during subsequent use.

[0021] When a trace amount of silicon is added to the gold-tin alloy, the AuSi phase that is preferentially formed during the solidification of the alloy is the δ-AuSn phase, which provides a nucleation basis, can refine the coarse primary phase, and improve the plastic processing performance of the alloy. 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, which improves the matching of the solder and the hard gold heat sink, while reducing the generation of hard points W between the solder layers and improving the welding bonding strength. The melting point of the gold-tin alloy is extremely sensitive to the composition. During the welding process, the gold element in the tungsten-titanium-gold coating diffuses into the modified gold-tin-silicon solder, the composition of the modified gold-tin-silicon solder changes, the gold content increases, and the composition of the modified gold-tin-silicon solder approaches the eutectic point to form a hypoeutectic structure. The fluidity and wettability of the solder are improved, the solid-liquid phase line is consistent, the melting range is reduced, the solder solidifies quickly, the phenomenon of cold soldering is reduced, and the welding reliability is improved.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a modified gold-tin-hard gold-plated heat sink material and a preparation method and application thereof. By introducing tungsten and titanium into the gold-plated layer on the surface of the heat sink material, the hardness of the gold-plated layer is significantly enhanced, the risk of the plated layer being scratched during use is effectively reduced, the service life of the heat sink material is extended, and the corrosion resistance of the gold-plated layer is enhanced; by adding a small amount of silicon into the gold-tin solder, the shaping processing performance of the gold-tin brittle solder is improved; by a vacuum hot pressing welding method, one-time forming of the solder-heat sink composite material is achieved, the accuracy of solder coverage is improved, and the problem of voids or overflow caused by solder size errors during welding is reduced; the tungsten-copper or molybdenum-copper heat sink material used improves the bonding strength between the heat sink base and the tungsten-titanium-gold plating layer, ensures the matching of the heat sink material with the chip, and then adds an oxygen-free copper heat sink to improve the heat dissipation efficiency, so that the heat sink material is more suitable for use in high-power devices such as SiC. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which:

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

[0026] Figure 2 The metallographic diagram of Example 1 is shown;

[0027] Figure identification: 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 DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Example 1

[0030] The gold-tin solder and the modified gold-tin-silicon solder are hot-rolled at 240°C to obtain a gold-tin solder sheet and a modified gold-tin-silicon solder sheet; a nickel layer is electroplated on the upper surface of the oxygen-free copper and the lower surface of the molybdenum-copper, and then a gold layer is magnetron sputtered; a nickel layer is electroplated on the upper surface of the molybdenum-copper, and then a tungsten-titanium-gold layer is magnetron sputtered using a tungsten-titanium target material with a titanium content of 10% and a gold target material; oxygen-free copper, gold-tin solder sheet, molybdenum-copper and modified gold-tin-silicon solder sheet are placed in order from bottom to top, and put into a vacuum eutectic furnace, evacuated, nitrogen is introduced into the vacuum eutectic furnace, and hot pressing welding is performed at 320°C for 30s, and a modified gold-tin-hard gold-plated heat sink material is obtained after cooling.

[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, the gold layer and the tungsten-titanium-gold layer are 3 μm thick.

[0032] Example 2

[0033] The gold-tin solder and the modified gold-tin-silicon solder were hot-rolled at 255°C to obtain a gold-tin solder sheet and a modified gold-tin-silicon solder sheet respectively; a nickel layer was electroplated on the upper surface of the oxygen-free copper and the lower surface of the tungsten-copper, and 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 the tungsten-copper, and then a tungsten-titanium-gold layer was magnetron sputtered; oxygen-free copper, gold-tin solder sheet, molybdenum-copper and modified gold-tin-silicon solder sheet were placed in order from bottom to top, and put into a vacuum eutectic furnace, evacuated, nitrogen was introduced into the vacuum eutectic furnace, and hot pressing welding was performed at 300°C for 60s, and a modified gold-tin-hard gold-plated heat sink material was obtained after cooling.

[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 are 5 μm thick.

[0035] The present invention provides a modified gold-tin-hard gold-plated heat sink material and a preparation method and application thereof. By introducing tungsten and titanium into the gold-plated layer on the surface of the heat sink material, the hardness of the gold-plated layer is significantly enhanced, the risk of the plated layer being scratched during use is effectively reduced, the service life of the heat sink material is extended, and the corrosion resistance of the gold-plated layer is enhanced; by adding a small amount of silicon into the gold-tin solder, the shaping processing performance of the gold-tin brittle solder is improved; by a vacuum hot pressing welding method, one-time forming of the solder-heat sink composite material is achieved, the accuracy of solder coverage is improved, and the problem of voids or overflow caused by solder size errors during welding is reduced; the tungsten-copper or molybdenum-copper heat sink material used improves the bonding strength between the heat sink base and the tungsten-titanium-gold plating layer, ensures the matching of the heat sink material with the chip, and then adds an oxygen-free copper heat sink to improve the heat dissipation efficiency, so that the heat sink material is more suitable for use in high-power devices such as SiC.

[0036] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A modified gold-tin-hard gold-plated heat sink material, characterized in that: The invention comprises 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) which are connected in sequence from bottom to top; the first heat sink layer (1) is oxygen-free copper, the second heat sink layer (5) is one of molybdenum copper or tungsten copper, and the hard gold plating layer comprises a tungsten-titanium-gold plating layer.

2. The modified gold-tin-hard gold-plated heat sink material according to claim 1, characterized in that: The chemical components of the modified gold-tin-silicon solder layer (7) include, by weight percentage: 19-21% tin, 1-2% silicon, and the remainder gold; the thickness of the modified gold-tin-silicon solder layer (7) is 0.025-0.05 mm.

3. The modified gold-tin-hard gold-plated heat sink material according to claim 1, characterized in that: The chemical components of the gold-tin solder layer (4) include, by weight percentage: 19-21% tin and the remainder gold; the thickness of the gold-tin solder layer (4) is 0.025-0.05 μm.

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

5. A method for preparing the modified gold-tin-hard gold-plated heat sink material according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) hot rolling the gold-tin solder and the modified gold-tin-silicon solder at 240-255° C. to obtain a gold-tin solder sheet and a modified gold-tin-silicon solder sheet; (2) a nickel layer and a gold layer are plated in sequence on the upper surface of oxygen-free copper; a nickel layer and a tungsten-titanium-gold layer are plated in sequence on the upper surface of molybdenum-copper or tungsten-copper, and a nickel layer and a gold layer are plated in sequence on the lower surface of molybdenum-copper or tungsten-copper; the nickel layer is plated by electroplating, and the gold layer and the tungsten-titanium-gold layer are plated by magnetron sputtering; (3) placing the materials processed in step (1) and step (2) in the order of oxygen-free copper, gold-tin solder sheet, molybdenum-copper or tungsten-copper and modified gold-tin-silicon solder sheet from bottom to top, and placing them in a vacuum eutectic furnace at 300-320° C. for 30-60 seconds for hot pressing welding, and obtaining a modified gold-tin-hard gold-plated heat sink material after cooling.

6. The method for preparing a modified gold-tin-hard gold-plated heat sink material according to claim 5, characterized in that: In step (2), the tungsten-titanium-gold layer is co-sputtered by a tungsten-titanium target and a gold target, and the titanium content in the tungsten-titanium target is 10-20%.

7. An application of the modified gold-tin-hard gold-plated heat sink material according to any one of claims 1 to 4 in high-power devices.

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