Preparation method of high-thermal-conductivity eutectic solder and foil for TR component packaging

Abstract

The present application relates to a kind of TR assembly package high thermal conductive eutectic medium temperature solder and foil strip preparation method, belong to microelectronic system packaging field.The solder composition: Sb 10.5~12.5wt%, Sn 0.5~2.0wt%, Ag 0.1~0.5wt%, Cu 0.1~0.5wt%, Pd 0.05~0.2wt%, Ni 0.05~0.2wt%, In 0.01~0.1wt%, P0.002~0.01wt%, the balance is Pb.Its foil strip preparation method includes raw material selection and intermediate alloy preparation, non-vacuum medium frequency induction melting, fast cooling horizontal casting and isothermal rolling step.The alloy melting point is moderate, has high strength, high thermal fatigue and high thermal conductivity etc.;Alloy foil composition is uniform, IMC is small, surface is clean, and the yield is high, satisfies the multistage packaging demand of TR assembly in microelectronic system.

Description

Technical Field

[0001] This invention relates to a high thermal conductivity eutectic medium-temperature solder and foil / strip preparation method for TR component packaging, belonging to the field of microelectronic system packaging. Background Technology

[0002] With the development needs of modern national defense, radar is a key piece of equipment and an important component in the modernization of the national navy and air force and the informatization of national defense. The development and application of active phased array radar is a key research focus for various countries. The T / R module is the core of the active phased array radar antenna design. It typically refers to the part between the video signal and the antenna in a wireless transceiver system. A wireless transceiver system is formed by connecting the antenna at one end and the intermediate frequency processing unit at the other. It consists of a low-noise amplifier, power amplifier, limiter, phase shifter, etc., and its main functions are to amplify the transmitted signal, amplify the received signal, and control the signal amplitude and phase. Furthermore, an active phased array radar contains tens of thousands of T / R modules, accounting for more than half of the total radar cost. To achieve optimal performance of the T / R module within the array, the most suitable packaging design is required. Therefore, the T / R module packaging not only determines the effective range, spatial resolution, and receiving sensitivity of the active phased array radar system, but also the overall size, weight, composition, manufacturability, and system performance of the radar.

[0003] Currently, to ensure connection strength, high heat dissipation, and service reliability, T / R module packaging, based on the overall microsystem's structural packaging requirements, primarily uses soft soldering materials for interconnecting the module and substrate. These mainly include Sn-37Pb (eutectic melting point 183℃), Sn-3Ag-0.5Cu (eutectic melting point 217℃), and Au-20Sn (eutectic melting point 280℃) alloy solders. Especially considering the multi-gradient, graded packaging of the entire microsystem and the requirements for high-temperature soldering, there is a need for a combination of Sn-3Ag-0.5Cu alloy solder and Au-20Sn alloy solder. In the middle of the gold solder, a soft solder is added to achieve the brazing connection of T / R components. Considering that the melting point of Au-20Sn alloy solder is 280℃, the brazing temperature of this level of solder is not allowed to exceed 275℃. Similarly, since the brazing temperature of the next level Sn-3Ag-0.5Cu alloy solder needs to be controlled at least between 240 and 245℃, the solidus temperature (initial liquidus temperature) of the solder must not be lower than 245℃. Therefore, the melting temperature of the solder must be controlled at 250℃, eutectic or near-eutectic, to avoid a wide melting range affecting the fluidity and brazing performance of the solder. The existing solders for this temperature range are mainly Pb-16Sn-7.5Sb-1Ag alloy solder, with a melting point of 237-243℃; Pb-30Sn alloy solder, with a melting point of 183-257℃; Sn-5Sb alloy solder, with a melting point of 232-240℃; Sn-10Sb alloy solder, with a melting point of 242-250℃; Pb-25In alloy solder, with a melting point of 240-264℃; Pb-10Sb-5Sn alloy solder, with a melting point of 240-256℃; and Pb-10Sb alloy solder, with a melting point of 252-260℃; none of them meet the melting point requirements. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to design and develop a eutectic alloy solder with a melting point of about 250°C for T / R module packaging, and to meet the high reliability requirements of T / R module connection, high thermal conductivity requirements, and long service life requirements in harsh and complex environments.

[0005] The main objective of this invention is to provide a high thermal conductivity eutectic medium-temperature solder for TR module packaging. The eutectic melting point of this alloy is 249°C, and the recommended brazing temperature is 275°C. It is particularly suitable as an intermediate-stage brazing encapsulation material between Au-20Sn alloy solder and Sn-3Ag-0.5Cu (or Sn-4Ag) alloy solder, and has high strength, high thermal fatigue resistance, and high thermal conductivity, as well as excellent wettability.

[0006] Another objective of this invention is to provide a method for preparing a high thermal conductivity eutectic medium-temperature solder. This method yields alloy foil strips with uniform composition, fine IMC (integrated molecular weight), clean surface, high yield, and the ability to process any preform, thus meeting the multi-level packaging requirements of TR (transformer) components in microelectronic systems.

[0007] To achieve the above objectives, the present invention adopts the following design scheme:

[0008] A high thermal conductivity eutectic medium-temperature solder for TR component packaging is composed of the following components by weight percentage: Sb 10.5-12.5wt%, Sn 0.5-2.0wt%, Ag 0.1-0.5wt%, Cu 0.1-0.5wt%, Pd 0.05-0.2wt%, Ni 0.05-0.2wt%, In 0.01-0.1wt%, P 0.002-0.01wt%, with the balance being Pb, and the total amount of the above components is 100%.

[0009] The optimized weight percentage of each element is composed of:

[0010] The preferred mass percentage of Sb added is 11.0–11.5 wt%.

[0011] The preferred mass percentage of Sn element added is 1.0 to 1.5 wt%.

[0012] The preferred mass percentage of Ag element added is 0.2–0.4 wt%, more preferably 0.3–0.35 wt%.

[0013] The preferred mass percentage of Cu element added is 0.1–0.3 wt%, more preferably 0.2–0.25 wt%.

[0014] The preferred mass percentage of Pd element added is 0.05–0.1 wt%, more preferably 0.08–0.1 wt%.

[0015] The preferred mass percentage of Ni element added is 0.05–0.1 wt%, more preferably 0.08–0.1 wt%.

[0016] The preferred mass percentage of In added is 0.05–0.1 wt%, more preferably 0.05–0.08 wt%.

[0017] The preferred mass percentage of added P element is 0.002–0.005 wt%, more preferably 0.004–0.005 wt%.

[0018] Among them, Ag, Cu, Pd, Ni and In are microalloying elements, and P is an antioxidant modification element.

[0019] The innovation of this invention lies primarily in the design of a eutectic solder with a melting point of approximately 250°C that meets the high-reliability packaging requirements of TR components. The main design concept involves first selecting a Pb-Sb alloy composition, and then designing a Pb-11.1Sb binary eutectic composition (eutectic melting point 252°C). A small amount of Sn is then added to address the poor wettability of lead-antimony alloys and improve the solder's wettability for metal plating such as Au, Ni, PtAg, and Cu. Experiments have shown that the Sn content is less than 0.5 wt%. When dissolved in Pb, the wettability is not significantly improved. When the Sn content is higher than 2wt%, it forms Sn2Sb3 intermetallic compound with Sb, which undergoes a low-melting-point phase transformation at 180℃, which is not conducive to the high-temperature service of the solder joint. The addition of a small amount of Ag aims to further improve wettability, improve the anti-electromigration properties of the alloy solder, and optimize the alloy melting point. Experiments have shown that controlling the Ag content at 0.1-0.5wt% can not only optimize the performance but also obtain a reasonable melting temperature without deteriorating the alloy's processing performance. Similarly, adding a small amount of Cu aims to improve the thermal conductivity of the solder and the strength of the solder joint after welding. Experiments showed that the Cu content should be 0.1–0.5 wt%. Adding a small amount of Pd aims to improve the solder's welding activity, further enhancing the alloy's thermal conductivity, wettability, and thermal fatigue resistance, while also improving the solder's plasticity and reducing intergranular corrosion of the metal coating, thus improving the high alloy's corrosion resistance and oxidation resistance. Experiments showed that the Pd content should be 0.05–0.2 wt%. Adding a small amount of Ni aims to refine the grain size, improve processing plasticity, and enhance the solder's thermal fatigue resistance and welding strength. Experiments showed that the Ni content should be 0.05–0.2 wt%. t%; Adding a small amount of In aims to improve the wettability and thermal conductivity of the alloy, optimize the alloy melting point, and obtain a more reasonable eutectic melting point composition. However, if In exceeds 0.2wt%, low-melting-point liquid phase precipitation will occur, resulting in a decrease in the service life of the alloy. Experiments have shown that the In content should be added in the range of 0.01 to 0.1wt%. Adding trace amounts of P aims to purify the melt. In the molten state, P forms a phosphorus oxide film when it comes into contact with air, covering the surface of the melt and preventing air from contacting the alloy melt, thus avoiding the melt from absorbing gas and oxidizing. If the P content is below 0.002wt%, the effect is not obvious. If the P content is above 0.005wt%, it will cause a decrease in the plasticity of the alloy, generate harmful impurities, and thus affect the solder formation and reduce the performance of the solder joint.

[0020] A method for preparing a high thermal conductivity eutectic medium-temperature solder foil / strip for TR component packaging, the method comprising the following steps:

[0021] (1) Raw material selection and preparation of master alloy

[0022] According to the composition of the high thermal conductivity eutectic medium-temperature solder for TR component packaging mentioned above, high purity Pb, Sb, Sn, Ag, Cu, Pd, Ni, In and P are used as raw materials;

[0023] Sb-Ag master alloy, Sb-Cu master alloy, Sb-Pd master alloy, and Sb-Ni master alloy were prepared by vacuum medium-frequency induction melting, respectively; Sn-In master alloy and Sn-P master alloy were prepared by non-vacuum induction melting.

[0024] (2) Non-vacuum medium-frequency induction melting

[0025] The intermediate alloy obtained in step (1) is used to calculate the weight of each element and the weight of the intermediate alloy according to the weight percentage of each element in the eutectic medium-temperature solder. Using a non-vacuum induction melting furnace, Pb ingots, Sb particles and Sn ingots are placed in the alumina crucible of the medium-frequency induction furnace and heated. After all Pb ingots, Sb particles and Sn ingots have melted, SnP, SnIn, SbAg, SbCu, SbPd and SbNi intermediate alloys are added in sequence. After all the intermediate alloys have melted, the temperature is lowered to the refining temperature. After holding the temperature, water-based rosin is added and the alloy melt is stirred thoroughly to complete the degassing and remove the surface slag. The temperature is then raised to the casting temperature and held.

[0026] (3) Rapid cooling horizontal casting

[0027] The molten alloy melt obtained in step (2) is cast horizontally from the bottom of the alumina melting crucible using an oxygen-free copper traction plate and a high-temperature graphite crystallizer. The cooling medium is ultrapure water. Casting is carried out at a uniform speed to obtain an alloy slab with a thickness of 4-8 mm, a width of 15-300 mm, and uniform composition.

[0028] (4) Isothermal rolling

[0029] The alloy slab obtained in step (3) is rough rolled by a hot rolling mill to obtain a strip with a thickness of 0.8 to 1.0 mm and a width of 10 to 300 mm, and then rolled into a coil. The strip is then cold rolled in multiple passes by a cold rolling mill until a foil with a thickness of 0.05 to 0.1 mm and a width of 10 to 300 mm is obtained, and then rolled into a coil.

[0030] In step (1), when selecting raw materials, the purity of Pb, Sb, Sn, Ag, Cu, Pd, Ni, In, and P is 99.999% by mass percentage.

[0031] In step (1), Sb-Ag master alloy, Sb-Cu master alloy, Sb-Pd master alloy and Sb-Ni master alloy are prepared by vacuum medium frequency induction melting. The content of Ag in Sb-Ag master alloy is 40wt% and the balance is Sb; the content of Cu in Sb-Cu master alloy is 40wt% and the balance is Sb; the content of Pd in ​​Sb-Pd master alloy is 50wt% and the balance is Sb; the content of Ni in Sb-Ni master alloy is 40wt% and the balance is Sb.

[0032] Sn-In master alloy and Sn-P master alloy were prepared by non-vacuum induction melting. The Sn-In master alloy contained 50 wt% In and the balance was Sn. The Sn-P master alloy contained 5 wt% P and the balance was Sn.

[0033] In step (2), the melting method is non-vacuum medium frequency induction melting, the refining temperature is 300-400℃, the holding time is 5-10min, and the amount of water-white rosin added is 0.05wt% of the total alloy feed; the casting temperature is 400-450℃, and the holding time is 5-10min.

[0034] In step (3), the casting method is horizontal fast cooling casting, the traction plate is oxygen-free copper, the crystallizer material is high-quality graphite, the cooling medium is ultrapure water, the casting temperature is 400-450℃, the casting speed is 50-200mm / min, and an alloy slab with a thickness of 4-8mm, a width of 15-300mm, and uniform composition is obtained.

[0035] In step (4), the hot rolling mill is a 320 two-roll reversible hot rolling mill with a roll temperature of 120-170℃ and a hot rolling pass processing rate of 10%-15%, producing strip with a thickness of 0.8-1.0mm and a width of 10-300mm, which is then rolled into coils; the cold rolling mill is a 165 two-roll reversible cold rolling mill with a cold rolling temperature of 5℃-25℃, a cold rolling pass processing rate of 5%-10%, and a tension of 0-10kN, producing foil with a thickness of 0.05-0.1mm and a width of 10-300mm, which is then rolled into coils.

[0036] This invention relates to the alloy composition of the solder and the high thermal conductivity eutectic medium-temperature solder foil / strip prepared by the above-described method. The solder alloy has a eutectic melting point of 249°C, with a recommended brazing temperature of 275°C. It is particularly suitable as an intermediate-stage brazing encapsulation material for Au-20Sn alloy solder and Sn-3Ag-0.5Cu (or Sn-4Ag) alloy solder. It exhibits excellent wettability to Au, Ni, PtAg, and Cu plating, meeting the multi-stage encapsulation requirements of TR components in microelectronic systems. The preparation method is "intermediate alloy preparation + non-vacuum medium-frequency induction melting + rapid cooling horizontal casting + isothermal rolling." This process solves problems such as segregation of multi-element alloys, inability to form PbSb-based alloy foil / strip, numerous internal defects, long process, and low efficiency, making it suitable for stable mass production. The alloy foil / strip obtained using this preparation method has uniform composition, fine IMC, clean surface, high yield, and can be processed into any pre-formed product, meeting the multi-stage encapsulation requirements of TR components in microelectronic systems.

[0037] Advantages of this invention:

[0038] 1. The high thermal conductivity eutectic medium-temperature solder produced by the method of the present invention is suitable for TR component packaging in microelectronic systems, and is particularly suitable as an intermediate-level brazing package between Au-20Sn alloy solder and Sn-3Ag-0.5Cu (or Sn-4Ag) alloy solder.

[0039] 2. The high thermal conductivity eutectic medium-temperature solder produced by the method of the present invention has a moderate melting point, with a eutectic melting point of 249℃.

[0040] 3. The high thermal conductivity eutectic medium-temperature solder manufactured by the method of the present invention has excellent brazing processability, good wettability and high thermal conductivity, ensuring the heat conduction and heat dissipation efficiency of TR components. The brazed Au-plated devices achieve continuous and dense welds with fewer IMC and high reliability.

[0041] 4. The high thermal conductivity eutectic medium-temperature solder produced by the method of this invention after welding and cleaning has good resistance to thermal fatigue, ensuring the service life of electronic devices in high-temperature environments.

[0042] 5. The processing and preparation process using the method of this invention is novel, resulting in finished products with very few internal pores and defects, small IMC, no cracks at the edges, high processing efficiency, high yield, high surface cleanliness, no oil, and high flatness consistency. It is also suitable for the stable mass production of soft solder.

[0043] This invention presents a scientifically designed, rationally proportioned, and simply prepared high thermal conductivity eutectic medium-temperature solder, suitable for multi-level gradient soldering processes. The solder is a multi-element eutectic alloy with a moderate melting temperature and excellent wettability for Au, Ni, PtAg, and Cu plating; meeting the multi-level packaging requirements of TR components in microelectronic systems.

[0044] The eutectic medium-temperature solder of this invention is a high-lead soldering material with a eutectic melting point of 249°C and a recommended soldering temperature of 270–275°C. This alloy has a moderate melting point, making it particularly suitable as an intermediate-stage soldering encapsulation material between Au-20Sn alloy solder and Sn-3Ag-0.5Cu (or Sn-4Ag) alloy solder, and it possesses high strength, high thermal fatigue resistance, and high thermal conductivity. Attached Figure Description

[0045] Figure 1 Differential thermal analysis spectrum of the high thermal conductivity eutectic medium-temperature solder alloy foil prepared in Example 1 of the present invention;

[0046] Figure 2 Electron micrograph of the joint structure of a (275)℃ gold-plated Kovar substrate brazed with a high thermal conductivity eutectic medium-temperature solder alloy prepared in Example 1 of the present invention. Detailed Implementation

[0047] The high thermal conductivity eutectic medium-temperature solder of the present invention and its preparation method will be further described below with reference to specific examples of ingredient calculation.

[0048] The present invention relates to a high thermal conductivity eutectic medium-temperature solder for TR module packaging, with the following weight percentage composition: Sb 10.5–12.5 wt%, Sn 0.5–2.0 wt%, Ag 0.1–0.5 wt%, Cu 0.1–0.5 wt%, Pd 0.05–0.2 wt%, Ni 0.05–0.2 wt%, In 0.01–0.1 wt%, P 0.002–0.01 wt%, and the balance being Pb. The added microalloying elements include Ag, Cu, Pd, Ni, and In; the added antioxidant modifying element is P.

[0049] The mass percentage of Ag added is 0.1–0.5 wt%, preferably 0.2–0.4 wt%, more preferably 0.3–0.35 wt%; the mass percentage of Cu added is 0.1–0.5 wt%, preferably 0.1–0.3 wt%, more preferably 0.2–0.25 wt%; the mass percentage of Pd added is 0.05–0.2 wt%, preferably 0.05–0.1 wt%, more preferably 0.08–0.1 wt%; the mass percentage of Ni added is 0.05–0.2 wt%, preferably 0.05–0.1 wt%, more preferably 0. The content of added elements is 0.08–0.1 wt%; the content of added elements of In is 0.01–0.1 wt%, preferably 0.05–0.1 wt%, more preferably 0.05–0.08 wt%; the content of added elements of P is 0.002–0.01 wt%, preferably 0.002–0.005 wt%, more preferably 0.004–0.005 wt%; the content of added elements of Sb is 10.5–12.5 wt%, preferably 11–11.5 wt%; the content of added elements of Sn is 0.5–2.0 wt%, preferably 1.0–1.5 wt%.

[0050] The method for preparing eutectic medium-temperature solder foil and strip of the present invention involves steps such as intermediate alloy preparation, non-vacuum medium-frequency refining, rapid cooling horizontal casting, and isothermal rolling, including the following steps:

[0051] (1) Raw material selection and master alloy preparation: The raw materials selected were high-purity Pb ​​(99.999%), high-purity Sb (99.999%), high-purity Sn (99.999%), high-purity Ag (99.999%), high-purity Cu (99.999%), high-purity Pd (99.999%), high-purity Ni (99.999%), high-purity In (99.999%), and pure P (99.99%). Sb-Ag, Sb-Cu, Sb-Pd, and Sb-Ni master alloys were prepared using vacuum induction melting; Sn-In and Sn-P master alloys were prepared using non-vacuum induction melting.

[0052] The Sb-Ag master alloy has the following element mass percentages: Ag 40wt%, balance Sb; Cu master alloy has the following element mass percentages: Cu 40wt%, balance Sb; Pd master alloy has the following element mass percentages: Pd 50wt%, balance Sb; Ni master alloy has the following element mass percentages: Ni 40wt%, balance Sb; In master alloy has the following element mass percentages: In 50wt%, balance Sn; and P master alloy has the following element mass percentages: P 5wt%, balance Sn.

[0053] (2) Non-vacuum medium-frequency induction melting: The intermediate alloy obtained in step (1) is used to calculate the weight of each element and the weight of the intermediate alloy according to the weight percentage of each element in the eutectic medium-temperature solder; a non-vacuum induction melting furnace is used to place high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots into the alumina crucible of the medium-frequency induction furnace, and the temperature is raised. After the high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots are completely melted, SnP5, SnIn50, SbAg40, SbCu40, SbPd50, and S are added in sequence. For bNi40 master alloy, after the master alloy is completely melted, the temperature is lowered to 300-400℃ (refining), held for 5-10 minutes, and 0.05wt% (total alloy feed) of water-white rosin is added. The alloy melt is thoroughly stirred to complete degassing and remove surface slag. The temperature is then raised to 400-450℃ (casting), and held for 5-10 minutes. The melting method is non-vacuum medium-frequency induction melting. The amount of water-white rosin is 0.05wt% (total alloy feed), and its function is to degas and slag form the alloy melt.

[0054] (3) Rapid cooling horizontal casting: The molten alloy obtained in step (2) is cast horizontally from the bottom of the alumina melting crucible using an oxygen-free copper traction plate and a high-efficiency graphite crystallizer. The cooling medium is ultrapure water, and the alloy slab is cast at a uniform speed. During the casting process, the alloy melt temperature is maintained at 400-450℃, the casting speed is 50-200mm / min, and an alloy slab with a thickness of 4-8mm, a width of 15-300mm, and uniform composition is obtained. The casting method is horizontal rapid cooling casting, the traction plate is oxygen-free copper, the crystallizer material is high-efficiency graphite, and the cooling medium is ultrapure water.

[0055] (4) Isothermal rolling: The alloy slab obtained in step (3) is rough rolled by a 320 two-roll reversible hot rolling mill. The rolling mill roll temperature is 120-170℃, the hot rolling pass processing rate is 10%-15%, and a strip with a thickness of 0.8-1.0mm and a width of 10-300mm is obtained and coiled. A 165 two-roll reversible cold rolling mill is used. The cold rolling temperature is 5℃-25℃, the cold rolling pass processing rate is 5%-10%, the tension is 0-10kN, and multiple cold rolling passes are used until a foil with a thickness of 0.05-0.1mm and a width of 10-300mm is obtained and coiled.

[0056] The eutectic medium-temperature solder of the present invention is suitable for intermediate-level brazing encapsulation of Au-20Sn alloy solder and Sn-3Ag-0.5Cu (or Sn-4Ag) alloy solder, and has excellent wettability for Au, Ni, PtAg, Cu, etc.; it meets the multi-level packaging requirements of TR components in microelectronic systems.

[0057] Example 1:

[0058] Step 1: Raw material preparation and intermediate alloy preparation

[0059] According to the alloy composition in Table 1, raw materials were prepared and weighed according to the designed component ratio. The total feed amount for a single furnace was 100 kg. Vacuum induction melting was selected to prepare Sb-40Ag master alloy, Sb-40Cu master alloy, Sb-50Pd master alloy, and Sb-40Ni master alloy, respectively. Sn-50In master alloy and Sn-5P master alloy were prepared by non-vacuum induction melting.

[0060] Step (2) Non-vacuum intermediate frequency induction melting

[0061] The intermediate alloy obtained in step (1) is calculated according to the weight percentage of each element in the eutectic medium-temperature solder, and the weight of each element and the intermediate alloy are shown in Table 2. Using a non-vacuum induction melting furnace, high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots are placed in the alumina crucible of the medium-frequency induction furnace and heated. After all the high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots have melted, SnP5, SnIn50, SbAg40, SbCu40, SbPd50, and SbNi40 intermediate alloys are added in sequence. After all the intermediate alloys have melted, the temperature is lowered to 350℃ (refining), held for 10 minutes, 50g of water-based rosin is added, the alloy melt is stirred thoroughly, degassing is completed, and surface slag is removed. The temperature is then raised to 450℃ (casting) and held for 10 minutes.

[0062] Step (3) Rapid cooling horizontal casting

[0063] The molten alloy obtained in step (2) was used for horizontal casting. Starting from the bottom of the alumina melting crucible, an oxygen-free copper traction plate was used, and a high-efficiency graphite crystallizer was selected. The cooling medium was ultrapure water, and the alloy slab was cast at a uniform speed. The alloy melt temperature was maintained at 450℃ and the casting speed was 200mm / min during the casting process, resulting in an alloy slab with a thickness of 8mm, a width of 300mm, and uniform composition.

[0064] Step (4) Isothermal rolling

[0065] The alloy slab obtained in step (3) is rough rolled using a 320 two-roll reversible hot rolling mill with a roll temperature of 170°C and a hot rolling pass rate of 15% to obtain a strip with a thickness of 0.8 mm and a width of 300 mm, which is then rolled into a coil. A 165 two-roll reversible cold rolling mill is used with a cold rolling temperature of 20°C, a cold rolling pass rate of 10%, and a tension of 8 kN. Multiple cold rolling passes are used until a foil with a thickness of 0.05 mm and a width of 300 mm is obtained, which is then rolled into a coil.

[0066] Example 2:

[0067] Step 1: Raw material preparation and intermediate alloy preparation

[0068] According to the alloy composition in Table 1, raw materials were prepared and weighed according to the designed component ratio. The total feed amount for a single furnace was 100 kg. Vacuum induction melting was selected to prepare Sb-40Ag master alloy, Sb-40Cu master alloy, Sb-50Pd master alloy, and Sb-40Ni master alloy, respectively. Sn-50In master alloy and Sn-5P master alloy were prepared by non-vacuum induction melting.

[0069] Step (2) Non-vacuum intermediate frequency induction melting

[0070] The intermediate alloy obtained in step (1) is calculated according to the weight percentage of each element in the eutectic medium-temperature solder, and the weight of each element and the intermediate alloy are shown in Table 2. Using a non-vacuum induction melting furnace, high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots are placed in the alumina crucible of the medium-frequency induction furnace and heated. After all the high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots have melted, SnP5, SnIn50, SbAg40, SbCu40, SbPd50, and SbNi40 intermediate alloys are added in sequence. After all the intermediate alloys have melted, the temperature is lowered to 300℃ (refining), held for 10 minutes, 50g of water-white rosin is added, the alloy melt is stirred thoroughly, degassing is completed, and surface slag is removed. The temperature is then raised to 400℃ (casting) and held for 5 minutes.

[0071] Step (3) Rapid cooling horizontal casting

[0072] The molten alloy obtained in step (2) was used for horizontal casting. Starting from the bottom of the alumina melting crucible, an oxygen-free copper traction plate was used, and a high-efficiency graphite crystallizer was selected. The cooling medium was ultrapure water, and the alloy slab was cast at a uniform speed. The alloy melt temperature was maintained at 400℃ and the casting speed was 50mm / min during the casting process, resulting in an alloy slab with a thickness of 4mm, a width of 15mm, and uniform composition.

[0073] Step (4) Isothermal rolling

[0074] The alloy slab obtained in step (3) is rough rolled using a 320 two-roll reversible hot rolling mill with a roll temperature of 120°C and a hot rolling pass rate of 10% to obtain a strip with a thickness of 1.0 mm and a width of 15 mm, which is then rolled into a coil. A 165 two-roll reversible cold rolling mill is used with a cold rolling temperature of 25°C, a cold rolling pass rate of 5%, and a tension of 10 kN. Multiple cold rolling passes are used until a foil with a thickness of 0.1 mm and a width of 12 mm is obtained, which is then rolled into a coil.

[0075] Example 3:

[0076] Step 1: Raw material preparation and intermediate alloy preparation

[0077] According to the alloy composition in Table 1, raw materials were prepared and weighed according to the designed component ratio. The total feed amount for a single furnace was 100 kg. Vacuum induction melting was selected to prepare Sb-40Ag master alloy, Sb-40Cu master alloy, Sb-50Pd master alloy, and Sb-40Ni master alloy, respectively. Sn-50In master alloy and Sn-5P master alloy were prepared by non-vacuum induction melting.

[0078] Step (2) Non-vacuum intermediate frequency induction melting

[0079] The intermediate alloy obtained in step (1) is calculated according to the weight percentage of each element in the eutectic medium-temperature solder, and the weight of each element and the intermediate alloy are shown in Table 2. Using a non-vacuum induction melting furnace, high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots are placed in the alumina crucible of the medium-frequency induction furnace and heated. After all the high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots have melted, SnP5, SnIn50, SbAg40, SbCu40, SbPd50, and SbNi40 intermediate alloys are added in sequence. After all the intermediate alloys have melted, the temperature is lowered to 400℃ (refining), held for 8 minutes, 50g of water-based white rosin is added, the alloy melt is stirred thoroughly, degassing is completed, and surface slag is removed. The temperature is then raised to 450℃ (casting) and held for 8 minutes.

[0080] Step (3) Rapid cooling horizontal casting

[0081] The molten alloy obtained in step (2) was used for horizontal casting. Starting from the bottom of the alumina melting crucible, an oxygen-free copper traction plate was used, and a high-efficiency graphite crystallizer was selected. The cooling medium was ultrapure water, and the alloy slab was cast at a uniform speed. The alloy melt temperature was maintained at 450℃ and the casting speed was 100mm / min during the casting process, resulting in an alloy slab with a thickness of 6mm, a width of 200mm, and uniform composition.

[0082] Step (4) Isothermal rolling

[0083] The alloy slab obtained in step (3) is rough rolled using a 320 two-roll reversible hot rolling mill with a roll temperature of 150°C and a hot rolling pass rate of 12% to obtain a strip with a thickness of 0.8 mm and a width of 200 mm, which is then rolled into a coil. A 165 two-roll reversible cold rolling mill is used with a cold rolling temperature of 25°C, a cold rolling pass rate of 8%, and a tension of 5 kN. Multiple cold rolling passes are used until a foil with a thickness of 0.08 mm and a width of 180 mm is obtained, which is then rolled into a coil.

[0084] Example 4:

[0085] Step 1: Raw material preparation and intermediate alloy preparation

[0086] According to the alloy composition in Table 1, raw materials were prepared and weighed according to the designed component ratio. The total feed amount for a single furnace was 100 kg. Vacuum induction melting was selected to prepare Sb-40Ag master alloy, Sb-40Cu master alloy, Sb-50Pd master alloy, and Sb-40Ni master alloy, respectively. Sn-50In master alloy and Sn-5P master alloy were prepared by non-vacuum induction melting.

[0087] Step (2) Non-vacuum intermediate frequency induction melting

[0088] The intermediate alloy obtained in step (1) is calculated according to the weight percentage of each element in the eutectic medium-temperature solder, and the weight of each element and the intermediate alloy are shown in Table 2. Using a non-vacuum induction melting furnace, high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots are placed in the alumina crucible of the medium-frequency induction furnace and heated. After all the high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots have melted, SnP5, SnIn50, SbAg40, SbCu40, SbPd50, and SbNi40 intermediate alloys are added in sequence. After all the intermediate alloys have melted, the temperature is lowered to 300℃ (refining), held for 10 minutes, 50g of water-based rosin is added, and the alloy melt is stirred thoroughly to complete degassing and remove surface slag. The temperature is then raised to 400℃ (casting) and held for 10 minutes.

[0089] Step (3) Rapid cooling horizontal casting

[0090] The molten alloy obtained in step (2) was used for horizontal casting. Starting from the bottom of the alumina melting crucible, an oxygen-free copper traction plate was used, and a high-efficiency graphite crystallizer was selected. The cooling medium was ultrapure water, and the alloy slab was cast at a uniform speed. The alloy melt temperature was maintained at 400℃ and the casting speed was 80mm / min during the casting process, resulting in an alloy slab with a thickness of 8mm, a width of 300mm, and uniform composition.

[0091] Step (4) Isothermal rolling

[0092] The alloy slab obtained in step (3) is rough rolled using a 320 two-roll reversible hot rolling mill with a roll temperature of 160°C and a hot rolling pass rate of 13% to obtain a strip with a thickness of 0.9 mm and a width of 300 mm, which is then rolled into a coil. A 165 two-roll reversible cold rolling mill is used with a cold rolling temperature of 10°C, a cold rolling pass rate of 10%, and a tension of 10 kN. Multiple cold rolling passes are used until a foil with a thickness of 0.05 mm and a width of 250 mm is obtained, which is then rolled into a coil.

[0093] Example 5:

[0094] Step 1: Raw material preparation and intermediate alloy preparation

[0095] According to the alloy composition in Table 1, raw materials were prepared and weighed according to the designed component ratio. The total feed amount for a single furnace was 100 kg. Vacuum medium-frequency induction melting was selected to prepare Sb-40Ag master alloy, Sb-40Cu master alloy, Sb-50Pd master alloy and Sb-40Ni master alloy respectively. Sn-50In master alloy and Sn-5P master alloy were prepared by non-vacuum induction melting.

[0096] Step (2) Non-vacuum intermediate frequency induction melting

[0097] The intermediate alloy obtained in step (1) is calculated according to the weight percentage of each element in the eutectic medium-temperature solder, and the weight of each element and the intermediate alloy are shown in Table 2. Using a non-vacuum induction melting furnace, high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots are placed in the alumina crucible of the medium-frequency induction furnace and heated. After all the high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots have melted, SnP5, SnIn50, SbAg40, SbCu40, SbPd50, and SbNi40 intermediate alloys are added in sequence. After all the intermediate alloys have melted, the temperature is lowered to 380℃ (refining), held for 8 minutes, 50g of water-based rosin is added, the alloy melt is stirred thoroughly, degassing is completed, and surface slag is removed. The temperature is then raised to 420℃ (casting) and held for 10 minutes.

[0098] Step (3) Rapid cooling horizontal casting

[0099] The molten alloy obtained in step (2) is used for horizontal casting. Starting from the bottom of the alumina melting crucible, an oxygen-free copper traction plate is used, and a high-efficiency graphite crystallizer is selected. Ultrapure water is used as the cooling medium, and the alloy slab is cast at a uniform speed. The alloy melt temperature is maintained at 420℃, and the casting speed is 150mm / min, resulting in an alloy slab with a thickness of 5mm, a width of 220mm, and uniform composition. Step (4) involves isothermal rolling.

[0100] The alloy slab obtained in step (3) is rough rolled using a 320 two-roll reversible hot rolling mill with a roll temperature of 140°C and a hot rolling pass rate of 10% to obtain a strip with a thickness of 1.0 mm and a width of 220 mm, which is then rolled into a coil. A 165 two-roll reversible cold rolling mill is used with a cold rolling temperature of 25°C, a cold rolling pass rate of 5%, and a tension of 10 kN. Multiple cold rolling passes are used until a foil with a thickness of 0.05 mm and a width of 200 mm is obtained, which is then rolled into a coil.

[0101] Example 6:

[0102] Step 1: Raw material preparation and intermediate alloy preparation

[0103] According to the alloy composition in Table 1, raw materials were prepared and weighed according to the designed component ratio. The total feed amount for a single furnace was 100 kg. Vacuum induction melting was selected to prepare Sb-40Ag master alloy, Sb-40Cu master alloy, Sb-50Pd master alloy, and Sb-40Ni master alloy, respectively. Sn-50In master alloy and Sn-5P master alloy were prepared by non-vacuum induction melting.

[0104] Step (2) Non-vacuum intermediate frequency induction melting

[0105] The intermediate alloy obtained in step (1) is calculated according to the weight percentage of each element in the eutectic medium-temperature solder, and the weight of each element and the intermediate alloy are shown in Table 2. Using a non-vacuum induction melting furnace, high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots are placed in the alumina crucible of the medium-frequency induction furnace and heated. After all the high-purity Pb ​​ingots, high-purity Sb particles, and high-purity Sn ingots have melted, SnP5, SnIn50, SbAg40, SbCu40, SbPd50, and SbNi40 intermediate alloys are added in sequence. After all the intermediate alloys have melted, the temperature is lowered to 300℃ (refining), held for 10 minutes, 50g of water-based white rosin is added, the alloy melt is stirred thoroughly, degassing is completed, and surface slag is removed. The temperature is then raised to 450℃ (casting) and held for 5 minutes.

[0106] Step (3) Rapid cooling horizontal casting

[0107] The molten alloy obtained in step (2) was used for horizontal casting. Starting from the bottom of the alumina melting crucible, an oxygen-free copper traction plate was used, and a high-efficiency graphite crystallizer was selected. The cooling medium was ultrapure water, and the alloy slab was cast at a uniform speed. The alloy melt temperature was maintained at 450℃ and the casting speed was 200mm / min during the casting process, resulting in an alloy slab with a thickness of 5mm, a width of 100mm, and uniform composition.

[0108] Step (4) Isothermal rolling

[0109] The alloy slab obtained in step (3) is rough rolled using a 320 two-roll reversible hot rolling mill with a roll temperature of 170°C and a hot rolling pass rate of 10% to obtain a strip with a thickness of 1.0 mm and a width of 90 mm, which is then rolled into a coil. A 165 two-roll reversible cold rolling mill is used with a cold rolling temperature of 25°C, a cold rolling pass rate of 5%, and no tension. Multiple cold rolling passes are performed until a foil with a thickness of 0.1 mm and a width of 50 mm is obtained, which is then rolled into a coil.

[0110] Table 1. Component ratios of alloys in Examples 1-6

[0111]

[0112] Table 2 shows the weight of each element and intermediate alloy in Examples 1-6.

[0113]

[0114]

[0115] The melting point, dimensions, wetting properties (gold plating), and thermal conductivity of the eutectic medium-temperature solder foils and strips prepared in Examples 1-6 were tested respectively, and the experimental data are shown in Table 3.

[0116] Table 3 Performance of Eutectic Medium-Temperature Solder Foil and Strip in Examples 1-6

[0117]

[0118] like Figure 1 The figure shows the differential thermal curve of the eutectic solder prepared in Example 1. As can be seen from the figure, the melting temperature of the Pb-Sb-Sn-Ag-Cu-Pd-In-P alloy obtained by using the alloy ratio and preparation method designed in this invention is 249.07~249.73℃. The endothermic and exothermic peak curves are smooth and obvious, and there is no precipitation of low-melting-point phase or phase transformation. Considering the accuracy of the equipment test, the alloy melting point can be regarded as the eutectic temperature of 249℃, which meets the patent design requirements.

[0119] like Figure 2 The image shows an electron microscope (EM) image of the joint structure obtained by brazing a gold-plated Kovar substrate with eutectic solder prepared in Example 1. As can be seen from the image, the eutectic solder developed in this invention has a significant brazing effect on gold-plated devices. The metallurgical bond at the weld seam is dense, and there is no excessive dissolution of the gold layer. There are few intermetallic compounds in the reaction interface.

[0120] The eutectic medium-temperature solder of the present invention has a moderate melting temperature, good wettability for Au, Ni, PtAg and Cu plating, good brazing processability, and long service life. It is particularly suitable as an intermediate-level brazing package for Au-20Sn alloy solder and Sn-3Ag-0.5Cu (or Sn-4Ag) alloy solder, meeting the multi-level packaging requirements of TR components in microelectronic systems.

[0121] The above embodiments only illustrate the eutectic medium-temperature solder of the present invention. In the above technical solutions of the present invention, the content of metal elements in the solder alloy can be freely selected within a specified range, and will not be listed one by one here. Therefore, the technical solutions contained in the above description should be regarded as illustrative, rather than intended to limit the scope of protection of the patent application of the present invention.

Claims

1. A method for preparing a high thermal conductivity eutectic medium-temperature solder foil / strip for TR module encapsulation, comprising the following steps: (1) Raw material selection and preparation of master alloy The high thermal conductivity eutectic medium-temperature solder for TR module packaging is composed of the following components by weight percentage: Sb 10.5~12.5wt%, Sn 0.5~2.0 wt%, Ag 0.1~0.5 wt%, Cu 0.1~0.5 wt%, Pd 0.05~0.2 wt%, Ni 0.05~0.2 wt%, In 0.01~0.1 wt%, P 0.002~0.01 wt%, with the balance being Pb; high-purity Pb, Sb, Sn, Ag, Cu, Pd, Ni, In, and P are used as raw materials. Sb-Ag master alloy, Sb-Cu master alloy, Sb-Pd master alloy, and Sb-Ni master alloy were prepared by vacuum medium-frequency induction melting, respectively; Sn-In master alloy and Sn-P master alloy were prepared by non-vacuum induction melting. (2) Non-vacuum medium frequency induction melting The intermediate alloy obtained in step (1) is used to calculate the weight of each element and the weight of the intermediate alloy according to the weight percentage of each element in the eutectic medium-temperature solder. Using a non-vacuum induction melting furnace, Pb ingots, Sb particles and Sn ingots are placed in the alumina crucible of the medium-frequency induction furnace and heated. After all Pb ingots, Sb particles and Sn ingots have melted, SnP, SnIn, SbAg, SbCu, SbPd and SbNi intermediate alloys are added in sequence. After all the intermediate alloys have melted, the temperature is lowered to the refining temperature. After holding the temperature, water-based rosin is added and the alloy melt is stirred thoroughly to complete the degassing and remove the surface slag. The temperature is then raised to the casting temperature and held. (3) Rapid cooling horizontal casting The molten alloy melt obtained in step (2) is cast horizontally from the bottom side of the alumina melting crucible using an oxygen-free copper traction plate, a high-temperature graphite crystallizer, and ultrapure water as the cooling medium. Casting is carried out at a uniform speed to obtain an alloy slab with a thickness of 4~8mm, a width of 15~300mm, and uniform composition. (4) Isothermal rolling The alloy slab obtained in step (3) is rough rolled by a hot rolling mill to obtain a strip with a thickness of 0.8~1.0mm and a width of 10~300mm, and then rolled into a coil; a cold rolling mill is used to cold roll it in multiple passes until a foil with a thickness of 0.05~0.1mm and a width of 10~300mm is obtained, and then rolled into a coil.

2. The method for preparing high thermal conductivity eutectic medium-temperature solder foil and strip for TR component packaging according to claim 1, characterized in that: The high thermal conductivity eutectic medium-temperature solder for TR component packaging is composed of the following components by weight percentage: Sb content 11.0~11.5 wt%, Sn content 1.0~1.5 wt%, Ag content 0.2~0.4 wt%, Cu content 0.1~0.3 wt%, Pd content 0.05~0.1 wt%, Ni content 0.05~0.1 wt%, In content 0.05~0.1 wt%, P content 0.002~0.005 wt%, with the balance being Pb.

3. The method for preparing high thermal conductivity eutectic medium-temperature solder foil and strip for TR component packaging according to claim 1, characterized in that: By mass percentage, the purity of Pb is 99.999%, the purity of Sb is 99.999%, the purity of Sn is 99.999%, the purity of Ag is 99.999%, the purity of Cu is 99.999%, the purity of Pd is 99.999%, the purity of Ni is 99.999%, the purity of In is 99.999%, and the purity of P is 99.99%.

4. The method for preparing high thermal conductivity eutectic medium-temperature solder foil and strip for TR component packaging according to claim 1, characterized in that: The Sb-Ag master alloy contains 40 wt% Ag and the balance is Sb; the Sb-Cu master alloy contains 40 wt% Cu and the balance is Sb; the Sb-Pd master alloy contains 50 wt% P and the balance is Sb; the Sb-Ni master alloy contains 40 wt% Ni and the balance is Sb; the Sn-In master alloy contains 50 wt% In and the balance is Sn; the Sn-P master alloy contains 5 wt% P and the balance is Sn.

5. The method for preparing high thermal conductivity eutectic medium-temperature solder foil and strip for TR component packaging according to claim 1, characterized in that: The refining temperature is 300~400℃, the holding time is 5~10min, and the amount of water-white rosin added is 0.05wt% of the total alloy feed; the casting temperature is 400~450℃, and the holding time is 5~10min.

6. The method for preparing high thermal conductivity eutectic medium-temperature solder foil and strip for TR component packaging according to claim 1, characterized in that: The casting temperature is 400~450℃, and the casting speed is 50~200mm / min.

7. The method for preparing high thermal conductivity eutectic medium-temperature solder foil and strip for TR component packaging according to claim 1, characterized in that: The hot rolling mill is a 320 two-roll reversible hot rolling mill with a roll temperature of 120~170℃ and a hot rolling pass processing rate of 10%~15%; the cold rolling mill is a 165 two-roll reversible cold rolling mill with a cold rolling temperature of 5℃~25℃, a cold rolling pass processing rate of 5%~10%, and a tension of 0~10kN.

8. A high thermal conductivity eutectic medium-temperature solder for TR module packaging, characterized in that: It is prepared by any one of claims 1-7.

9. The application of the high thermal conductivity eutectic medium-temperature solder according to claim 8 in TR component packaging.

10. The application according to claim 9, characterized in that: The application of the solder in intermediate graded brazing packages using Au-20Sn alloy solder and Sn-3Ag-0.5Cu, or Au-20Sn alloy solder and Sn-4Ag alloy solder.

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