A process for producing gold-tin thin film heat sink

Abstract

The present invention relates to the field of semiconductor production technology, and specifically to a process for producing gold-tin thin film heat sinks. The process for producing gold-tin thin film heat sinks in the present application utilizes high-precision hot rolling technology to roll gold-tin smelting ingots with precise composition into gold-tin solder strips with a thickness of 3 to 20 μm, and punches them into gold-tin preformed solder sheets of appropriate size; then utilizes ultrasonic welding, laser welding, hot pressing welding, resistance welding, etc. to spot weld the ultra-thin gold-tin preformed solder sheets on various metallized heat sinks, thereby achieving ultra-thin thickness of the gold-tin thin film heat sink, high dimensional precision, low cost, precise composition, and high density of the gold-tin structure. The process of the present application does not have the problems of large waste of precious metal materials and difficulty in recycling, and can greatly reduce the cost of gold-tin thin film heat sinks.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor production, and in particular to a process for producing a gold-tin thin film heat sink. Background Art

[0002] With the advancement of semiconductor technology, device sizes are shrinking, while heat generation per unit area is increasing. Excessively high chip operating temperatures can seriously impact device functionality, reliability, and lifespan. Improving device heat dissipation efficiency has become a key technology. A heat sink, in industry, refers to a heat dissipation device. Addressing heat dissipation is crucial among the various key technologies currently used in high-power optoelectronic devices. Heat sinks are typically made of high-power materials such as copper and aluminum. However, the TCE of copper and aluminum is very high, which is not compatible with the TCE of silicon chips. Therefore, other materials with matching TEC are used in heat sinks, such as aluminum nitride, aluminum oxide, BeO, tungsten copper, molybdenum copper, and Al-Si. The thermal resistance of the gold-tin solder, the medium connecting the heat sink to the laser chip, is also a key factor in determining the thermal resistance of the heat dissipation channel. Therefore, an ultra-thin layer (3-20 μm) of gold-tin solder is pre-deposited on the heat sink, commonly known as a gold-tin thin film heat sink.

[0003] In the semiconductor device industry, the most common gold-tin solder used on heat sinks is deposited using a thin-film process. Thin-film processes, such as vacuum evaporation and ion sputtering, enable precise control of film shape and thickness. For example, the Ni / Au electrodes and gold-tin solder used in optical communication device chip carriers are both produced using thin-film processes. However, the disadvantages of thin-film processes are: 1) low material utilization and slow deposition rates, which can easily lead to waste of precious metal Au. This incurs additional costs during precious metal recycling, especially for the gold-tin solder layer, contributing to high heat sink costs; 2) imprecise composition of the thin film, typically limited to ±5% Au content. Fluctuations in composition lead to fluctuations in the liquidus, which can lead to unstable solder melting temperatures during chip bonding and voids caused by poor interfacial wetting; 3) the deposited gold-tin layer is porous and prone to oxidation, resulting in poor air expulsion during solder melting. This can cause voids within the solder and at the interface, increasing thermal resistance.

[0004] To this end, the present invention addresses the shortcomings of thin film processes such as large material waste, inaccurate composition, and looseness and porosity. This application proposes a novel method for preparing various types of gold-tin thin film heat sinks. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a process for producing a gold-tin thin film heat sink.

[0006] To achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: A process for producing a gold-tin thin film heat sink, comprising the following method:

[0007] S1. Smelting gold and tin into gold-tin ingots with high-precision composition;

[0008] S2, rolling the gold-tin ingot into an ultra-thin gold-tin solder strip using high-precision hot rolling;

[0009] S3, punching the gold-tin solder strip into an ultra-thin gold-tin preform solder sheet of appropriate size;

[0010] S4. Install the ultra-thin gold-tin preform solder sheet on various metallized heat sinks by spot welding to obtain a gold-tin thin film heat sink.

[0011] Furthermore, step S1 includes using a high and low temperature melt mixing technology to first melt pure gold and pure tin in a 350°C vacuum melting furnace, keep warm for 10 minutes, and then pour into a graphite mold, and divide the gold and tin into two parts for melting separately.

[0012] Furthermore, the smelting process includes putting the first portion of gold-tin into a high-temperature vacuum melting furnace, keeping it warm for 10 minutes after melting, pouring it out to cool, and constantly monitoring the temperature; then putting the second portion of gold-tin into the high-temperature vacuum melting furnace, keeping it warm for 10 minutes after melting; finally, when the temperature of the first portion of gold-tin melt drops to 287-293°C, quickly pouring the second portion of gold-tin melt into it, mixing and cooling, and obtaining a gold-tin ingot of a high-low temperature mixed melt.

[0013] Furthermore, the temperature of the high temperature vacuum melting furnace is 347-353°C.

[0014] Furthermore, the ratio of the first gold-tin alloy to the second gold-tin alloy does not exceed 0.8-1.2:2.8-3.2.

[0015] Furthermore, step S2 includes using a four-roller mill to dynamically control the rolling temperature and the rolling pressure to roll the gold-tin ingot into a solder strip with a thickness of 3-20 μm.

[0016] Furthermore, the power source of the four-roller machine is the first and fourth large rollers, and the second and third small rollers are in contact with the foil, and the heat of the small rollers is transferred by the first and fourth large rollers; the temperature of the small rollers is 220℃±5℃; the surface roughness of the second and third small rollers is controlled between 0.5-0.8μm; and starting from the thickness of the gold-tin ingot of 0.03mm, the pressure of each pass is controlled between 5-8μm.

[0017] Furthermore, step S2 also includes, when the gold-tin ingot is rolled to a thickness of 0.03 mm, placing it in heat treatment oil at a temperature of 230°C for 40-60 minutes, then taking it out and cooling it naturally, using acetone and pure water respectively, degreasing it, and then rolling it to less than 10 μm; wherein, the heat treatment oil is a mineral heat transfer oil, and the components of the mineral heat transfer oil are xylene ether aromatic compounds, a C14-C30 long straight-chain heavy alkylbenzene mixture, and a C20 long straight-chain petroleum base oil.

[0018] Furthermore, before spot welding in step S4, the ultra-thin gold-tin preformed solder sheet is passed through a 200°C protective atmosphere tunnel furnace for stress relief annealing to improve the flatness of the solder sheet at a speed of 20 cm / s; and during the spot welding process, nitrogen or argon is always blown, and the flow rate of the nitrogen or argon is 0.5 m³ / min.

[0019] Furthermore, the spot welding method includes at least one of ultrasonic welding, laser welding, hot pressure welding, and resistance welding.

[0020] Beneficial effects of the present invention: As can be seen from the above description of the present invention, compared with the prior art, the present invention is a process for producing gold-tin thin film heat sinks. By utilizing high-precision hot rolling technology, gold-tin smelting ingots with precise composition are rolled into gold-tin solder strips with a thickness of 3 to 20 μm, and then punched into gold-tin preforms of appropriate sizes. Ultrasonic welding, laser welding, hot pressing welding, resistance welding, etc. are then used to spot weld the ultra-thin gold-tin preforms onto various metallized heat sinks. This allows the gold-tin thin film heat sink to be ultra-thin, with high dimensional precision, low cost, precise composition, and a dense gold-tin structure. The present process does not suffer from the problems of large waste of precious metal materials and difficulty in recycling, and can greatly reduce the cost of gold-tin thin film heat sinks.

[0021] The present invention can obtain an ultrafine grain structure through a high-low temperature melt mixing process, and the prepared ultrathin gold-tin solder sheet has the advantages of dense grain structure, precise solder melting point, good processing performance, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a flow chart of a process for producing a gold-tin thin film heat sink in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0024] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0025] Reference Figure 1 As shown, a preferred embodiment of the present invention, a process for producing a gold-tin thin film heat sink, includes the following method:

[0026] S1. Smelting gold and tin into gold-tin ingots with high-precision composition;

[0027] Because the melting points of pure tin and pure gold differ significantly, they are difficult to melt and mix evenly to form a dense, fine-grained eutectic structure. Therefore, a high-low temperature melt mixing technique is employed. Pure gold and tin are first melted in a 350°C vacuum melting furnace, held at this temperature for 10 minutes, and then poured into a graphite mold. The gold and tin are then separated and melted in two separate portions, each with a weight ratio of 1:3. The melting process involves placing the first portion of gold and tin into a 350°C vacuum melting furnace, melting it, holding it for 10 minutes, then pouring it out to cool, while constantly monitoring the temperature. The second portion of gold and tin is then placed into a 350°C vacuum melting furnace, melting it, holding it for 10 minutes, and finally, when the temperature of the first portion of gold and tin melt drops to 290°C, the second portion of gold and tin melt is quickly poured in, reaching a temperature of 347-353°C. The mixture is then mixed and cooled to produce a gold-tin ingot made from a high-low temperature mixed melt.

[0028] The advantages of using high and low temperature melt mixing technology are that it can achieve uniform composition, fine particles, and no primary phase growth. At the same time, the high temperature melt of 350°C and the low temperature melt of 290°C in this application are the most suitable temperatures found through experiments, and the allowable temperature fluctuation is ±3°C.

[0029] At the same time, the heat preservation effect makes the metal melt more uniform and thorough, and a longer holding time helps the metal components mix. However, it generally does not exceed 20 minutes. The mass ratio of high and low temperature melt is 1:3, which was determined through multiple experiments, and the optimal value is no more than 1±0.2:3±0.2.

[0030] S2, rolling the gold-tin ingot into an ultra-thin gold-tin solder strip using high-precision hot rolling;

[0031] Specifically, a four-roller mill dynamically controls the rolling temperature and rolling pressure to roll the gold-tin ingot into solder strips with a thickness of 3-20 μm. This four-roller mill, independently developed by the applicant, differs from a two-roller mill in its operation in that the power source comes from the first and fourth large rollers, while the second and third small rollers (30 mm in diameter) contact the foil, with heat transferred from the small rollers by the first and fourth large rollers. The measured temperature of the small rollers is 220°C ± 5°C; the surface roughness of the second and third small rollers is controlled between 0.5 and 0.8 μm; and starting from a gold-tin ingot thickness of 0.03 mm, the rolling pressure per pass is controlled between 5 and 8 μm.

[0032] Moreover, gold-tin foil needs to be heat-treated when rolled below a thickness of 0.015mm, and normal vacuum annealing easily causes the gold-tin to melt, making it difficult to precisely control the temperature. Therefore, heat-treating oil is used to heat-treat gold-tin foil, which has the advantage of uniform temperature and small fluctuations. The heat-treating oil is a mineral-type heat-conducting oil, whose components are xylene ether aromatic compounds, a mixture of C14-C30 long straight-chain heavy alkylbenzenes, and a C20 long straight-chain petroleum base oil. It is used when the thin strip is rolled to a thickness of 0.03mm. Place it in the heat-treating oil at a temperature of 230°C for 40-60 minutes, remove it and cool it naturally, then use acetone and pure water to remove the oil, and then roll it to less than 20μm.

[0033] S3, punching the gold-tin solder strip into an ultra-thin gold-tin preform solder sheet of appropriate size;

[0034] S4. Install the ultra-thin gold-tin preform solder sheet on various metallized heat sinks by spot welding to obtain a gold-tin thin film heat sink.

[0035] That is, preparing corresponding precision fixtures; clamping the heat sink and ultra-thin gold-tin preform solder sheet; and mounting the ultra-thin gold-tin preform solder sheet on various metallized heat sinks by spot welding or large-area welding to obtain a gold-tin thin film heat sink;

[0036] Specifically, before spot welding, the ultra-thin gold-tin preformed solder sheet needs to be passed through a 200°C protective atmosphere tunnel furnace at a speed of 20 cm / s. This step is to remove stress during the rolling process of the gold-tin solder sheet and prevent the release of thermal stress in some areas during the spot welding process, which may cause the solder sheet to warp and deform. During the spot welding process, nitrogen or argon gas must be blown at all times. Firstly, it is to reduce solder oxidation caused by spot welding, and secondly, it is to cool the solder during spot welding to avoid heat accumulation. Nitrogen or argon gas is blown through a bamboo tube with a flat mouth width of 3 cm to increase the purge area. The flow rate during spot welding is controlled at 0.5 m³ / min.

[0037] The present invention utilizes high-precision hot rolling technology to roll a precisely formulated gold-tin smelted ingot into a gold-tin solder strip with a thickness of 3 to 20 μm. This strip is then punched into gold-tin preforms of suitable dimensions. Ultrathin gold-tin preforms are then spot-welded to various metallized heat sinks using methods such as ultrasonic welding, laser welding, hot pressing, and resistance welding. This results in an ultra-thin gold-tin thin film heat sink with high dimensional precision, low cost, precise composition, and a dense gold-tin structure. This process eliminates the issues of significant precious metal waste and recycling difficulties, significantly reducing the cost of gold-tin thin film heat sinks.

[0038] Under the premise that no conflict occurs, those skilled in the art may freely combine and superimpose the above-mentioned additional technical features.

[0039] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A process for producing a gold-tin thin film heat sink, characterized in that: This includes the following methods: S1. Smelting gold and tin into gold-tin ingots with high-precision composition; Using high and low temperature melt mixing technology, pure gold and pure tin are first melted in a 350℃ vacuum melting furnace, kept warm for 10 minutes, and then poured into a graphite mold. The gold and tin are divided into two parts and melted separately; The smelting process includes placing a first portion of gold-tin into a high-temperature vacuum melting furnace at 347-353° C., holding the temperature for 10 minutes after melting, pouring out and cooling, and constantly monitoring the temperature; placing a second portion of gold-tin into the high-temperature vacuum melting furnace, holding the temperature for 10 minutes after melting; and finally, when the temperature of the first portion of gold-tin melt drops to 287-293° C., quickly pouring the second portion of gold-tin melt into the furnace, mixing and cooling, and obtaining a gold-tin ingot of a high-low temperature mixed melt. S2, rolling the gold-tin ingot into an ultra-thin gold-tin solder strip using high-precision hot rolling; S3, punching the gold-tin solder strip into an ultra-thin gold-tin preform solder sheet of appropriate size; S4, mounting the ultra-thin gold-tin preform solder sheet on various metallized heat sinks by spot welding to obtain a gold-tin thin film heat sink; Before spot welding, the ultra-thin gold-tin preformed solder sheet is passed through a 200°C protective atmosphere tunnel furnace for stress relief annealing to improve the flatness of the solder sheet at a speed of 20 cm / s; and during the spot welding process, nitrogen or argon gas is always used for protection, and the flow rate of the nitrogen or argon gas is 0.5 m / min.

2. The process for producing a gold-tin thin film heat sink according to claim 1, characterized in that: The ratio of the first part of the gold-tin alloy to the second part of the gold-tin alloy does not exceed 0.8-1.2:2.8-3.

2.

3. The process for producing a gold-tin thin film heat sink according to claim 1, characterized in that: The step S2 includes using a four-roller mill to dynamically control the rolling temperature and the rolling pressure to roll the gold-tin ingot into a solder strip with a thickness of 3-20 μm.

4. The process for producing a gold-tin thin film heat sink according to claim 3, characterized in that: The power source of the four-roller mill is the first and fourth large rollers, and the second and third small rollers are in contact with the foil. The heat of the small rollers is transferred by the first and fourth large rollers. The temperature of the small rollers is 220℃±5℃. The surface roughness of the second and third small rollers is controlled between 0.5-0.8μm. Starting from the thickness of the gold-tin ingot of 0.03mm, the pressure of each pass is controlled between 5-8μm.

5. The process for producing a gold-tin thin film heat sink according to claim 3, characterized in that: The step S2 further includes placing the gold-tin ingot into heat treatment oil at a temperature of 230° C. for 40-60 minutes after the ingot is rolled to a thickness of 0.03 mm, then taking it out and cooling it naturally, using acetone and pure water to remove the oil, and then rolling it to less than 20 μm; wherein the heat treatment oil is a mineral heat transfer oil, and the components of the mineral heat transfer oil are xylene ether aromatic compounds, a C14-C30 long straight-chain heavy alkylbenzene mixture, and a C20 long straight-chain petroleum base oil.

6. The process for producing a gold-tin thin film heat sink according to claim 1, characterized in that: The spot welding method includes at least one of ultrasonic welding, laser welding, hot pressure welding, and resistance welding.

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