阅读说明：本技术 一种铝基复合材料电子封装壳体半固态成形技术 (Semi-solid forming technology for aluminum-based composite material electronic packaging shell ) 是由 王开坤 杨森 于 2020-11-12 设计创作，主要内容包括：本发明公开了一种高体积分数铝基复合材料电子封装壳体的半固态成形工艺方法,属于电子封装领域。用电阻炉将低体积分数TiB-2颗粒增强铝基复合材料在685～700℃下进行熔化,保温20～30min,并加以电磁搅拌；将复合材料熔体冷却至半固态温度区间,获得半固态浆料,或直接将合适尺寸大小的复合材料加热至半固态温度区间获得半固态坯料；将电子封装壳体成形腔设计在挤压模具凹模腔底部边缘水平方向；最后将半固态浆料或坯料挤压成形,获得电子封装壳体零件。优点在于,完成了颗粒增强铝基复合材料从原料到成品过程中增强颗粒体积分数由低到高的巧妙转变,实现了电子封装壳体短流程、低成本的近终成形制造,提高了壳体零件的表面质量和力学性能。(The invention discloses a semi-solid forming process method of a high-volume-fraction aluminum-based composite material electronic packaging shell, belonging to the field of electronic packaging. Using a resistance furnace to convert low volume fraction TiB 2 Melting the particle reinforced aluminum matrix composite material at 685-700 ℃, preserving heat for 20-30 min, and electromagnetically stirring; cooling the composite material melt to a semi-solid temperature range to obtain semi-solid slurry, or directly heating the composite material with a proper size to the semi-solid temperatureObtaining semi-solid blank in the interval; designing a forming cavity of the electronic packaging shell in the horizontal direction of the bottom edge of a concave die cavity of an extrusion die; and finally, extruding and forming the semi-solid slurry or the blank to obtain the electronic packaging shell part. The method has the advantages of completing the ingenious conversion of the volume fraction of the reinforced particles from low to high in the process of changing the raw materials of the particle reinforced aluminum matrix composite material into finished products, realizing the near-net forming manufacturing of the electronic packaging shell with short flow and low cost, and improving the surface quality and the mechanical property of shell parts.)

1. The invention aims to provide a method for utilizing low volume percent TiB₂The semi-solid forming process for preparing the high volume fraction composite material electronic packaging shell by using the particle reinforced aluminum-based composite material raw material is characterized by comprising the following process steps:

(1) drying the prepared aluminum-based composite material block at 100-120 ℃, heating and melting the aluminum-based composite material block by using a resistance furnace, preserving heat for 25-35 minutes, and stirring the composite material melt by using an electromagnetic stirring device.

(2) And (4) properly treating the composite material melt according to different semi-solid forming methods for carrying out the extrusion forming process in the step (4).

If a semi-solid rheoforming process is adopted, directly cooling the heat-preserved molten composite material to a semi-solid temperature range to obtain particle reinforced aluminum matrix composite material semi-solid slurry;

and (ii) if a semi-solid thixoforming process is adopted, pouring the composite material melt into a preset die for rapid cooling to obtain a thixoforming blank, cutting the blank into an ideal size according to actual requirements, and carrying out secondary induction heating on the blank until the blank is in a semi-solid temperature range during forming.

(3) The semi-solid extrusion forming electronic packaging shell mold is designed, and a shell forming cavity is designed in the horizontal direction of the bottom edge of a female mold cavity of an extrusion mold.

(4) Semi-solid extrusion forming is carried out on the electronic packaging shell: the forming temperature is determined by the temperature of a liquid-solid two-phase area of the composite material; the forming speed is controlled to be 90-150 mm/s; the preheating temperature of the die is 200-300 ℃; the forming pressure is set to be 450-650 kN; the pressure maintaining time is 6-10 s.

2. The method of claim 1, wherein TiB₂A356 composite or TiB₂The smelting temperature of the AlCu5MnCdV composite material is 685-700 ℃.

3. The method of claim 1, wherein TiB₂The matrix alloy of the/A356 composite material comprises the following components in percentage by mass: 6.5-7.5% of silicon, 0.30-0.45% of magnesium, 0.15-0.2% of titanium, 0.08-0.12% of iron, 0.05-0.10% of copper, 0.03-0.05% of manganese and the balance of aluminum; TiB₂The AlCu5MnCdV composite material matrix alloy comprises the following components in percentage by mass: 4.5-5.5% of copper, 0.03-0.06% of silicon, 0.32-0.38% of manganese, 0.10-0.18% of cadmium, 0.08-0.12% of vanadium, 0.13-0.18% of iron and the balance of aluminum. The volume percentage of the titanium boride reinforced particles in the composite material is 20-35%.

4. The method of claim 1, wherein TiB₂The solidus temperature range of the solution of the/A356 composite material is 573.57-622.24 ℃; TiB₂The solidus temperature range of the AlCu5MnCdV composite material liquid is 551.28-646.31 ℃.

5. The method according to claim 1, wherein the composite material slurry is poured at a temperature of 665-685 ℃ and cooled by circulating water cooling.

Technical Field

The invention belongs to the field of electronic packaging, and particularly relates to a TiB₂A semi-solid forming technology of particle reinforced aluminum matrix composite.

Background

With the rapid increase of the integration degree of the integrated circuit, the heat productivity of the chip is increased dramatically, and the service life of the chip is reduced correspondingly. This is mainly because in microelectronic integrated circuits and high-power rectifying devices, the thermal fatigue of electronic components occurs due to local thermal stress and poor heat dissipation caused by the mismatch of thermal expansion coefficients between materials, and thus, the reasonable electronic packaging is an effective way to solve the problem. The housing for packaging generally functions to fix, seal, dissipate heat and protect the chip, so the material for manufacturing the electronic packaging housing needs to have the characteristics of low thermal expansion coefficient, high thermal conductivity, high strength and rigidity, and in some special application fields, especially the aerospace field, the density of the housing material is required to be as low as possible to reduce the overall weight.

The particle reinforced aluminum-based composite material is formed by compounding a pure aluminum or aluminum alloy matrix and various ceramic particle reinforced phases, the composite material with high volume percentage can not only keep the good heat conductivity of metal but also obtain adjustable thermal expansion coefficient, and can also meet the requirements of other properties of an electronic packaging shell, so the particle reinforced aluminum-based composite material has great application prospect in the field of electronic packaging and represents the development direction of novel light packaging materials. However, the high volume fraction of the particulate reinforced aluminum matrix composite also has some disadvantages that limit the development thereof, such as: relatively high cost, difficulty in secondary processing (particularly plastic forming), and the like. Therefore, developing a short-flow, near-net-shape, and easily-controlled material forming process to manufacture the aluminum-based composite electronic packaging shell is a challenging and creative work, and has great theoretical significance and practical value.

In the early 70 s of the 20 th century, professor Flemings, usa's institute of technology, developed an advanced metal forming method, namely Semi-Solid Processing (SSP), between liquid metal casting and Solid metal plastic working. Research by professor Flemings shows that when metal is solidified, violent stirring is applied to inhibit the growth of crystal grains and break dendritic crystals, so that a fine and uniform nearly spherical microstructure is formed, a solid-liquid mixed slurry with a certain granular solid phase component suspended in a liquid metal mother solution is obtained, and the semi-solid slurry has excellent rheological property and thixotropy. Researchers now believe that semisolid dendrite spheroidization behavior is mainly related to various mechanisms:

(1) a dendrite fracture mechanism. The shear stress generated under strong stirring causes the crystal grains to collide with each other, leading to the rupture of dendrite arms (usually the rupture is at the root of dendrite arms), and the ruptured dendrites can play a role in promoting nucleation and inhibiting the growth of the crystal grains, thereby forming a plurality of fine crystal grains. These rosette-like small grains gradually evolve into a nearly spherical structure as the temperature is lowered.

(2) A dendrite fusing mechanism. The melt flow is accelerated by the vigorous stirring, which causes thermal vibrations and local thermal stresses, which make the longer-sized dendrite arm roots more susceptible to fusing by the heat flow. This is because the melting point is reduced because the mass fraction of the solute in the solid phase at the root of the dendrite arm is higher, and the diameter of the dendrite arm root is smaller than that of other parts, so the root of the dendrite arm is melted preferentially under the action of thermal disturbance, and the dendrite fragments brought into the melt by the heat flow are used as the substrate of crystal nucleation to promote the crystal grains to gradually turn into near-spherical shape.

(3) A dendrite bending mechanism. The dendrites will bend under flow stress, creating dislocations that result in plastic deformation. At temperatures above the solidus, the dislocations climb over each other to form grain boundaries, and when the difference in orientation of adjacent grains exceeds 20 ° and the grain boundaries can exceed twice the energy of the solid-liquid interface, the liquid phase will wet the grain boundaries and rapidly penetrate along the grain boundaries, separating the dendrite arms from the stems. Also, the separated dendrites can play a role in promoting the spheroidization of grains.

(4) Grain drift, mixing-suppression mechanism. While still others have considered that in the solid-liquid two-phase region, stirring is difficult to cause dendrite breakage, at least dendrite breakage is not a major factor in grain spheroidization. They propose that mixing and convection cause grain drift, greatly increasing the heterogeneous nucleation rate, and thus refining the grains. In the growth process of the crystal grains, the strong mixed convection greatly improves the mass transfer and heat transfer process of the melt, plays a great role in inhibiting the growth of the crystals, simultaneously, the mass transfer and heat transfer conditions of the crystal grains in all directions tend to be consistent, the growth form of the crystals is changed, and finally the crystal grains become round.

Compared with the traditional dendritic crystal solidification mode, because of the existence of the spherical crystal structure in the semi-solid slurry or the blank, the deformation resistance is smaller during processing, and a metal material with poorer plastic processing performance can be formed; the temperature is lower compared with the liquid casting forming temperature, the heat flow impact of the slurry or the blank to the die is small, and the service life of the die is correspondingly prolonged; the product produced by semi-solid processing has uniform microstructure, less defects such as internal cavities, shrinkage porosity and the like, and good surface quality. More importantly, the semi-solid processing technology is a near-net-shape forming technology, can reduce the waste of materials, shorten the production flow and further save the production cost.

Since the semi-solid processing technology is proposed, people have more and more deeply known the technology, and great progress is made in the aspects of experimental research, numerical simulation and the like. In the 90 s of the 20 th century, the semi-solid industry in some developed countries has gradually progressed to engineering applications. In 1994, the first semi-solid die forging aluminum alloy automobile hub plant in the world was established by the American Alumax Engineered Metal Processes (AEMP) company, which marked the shift of semi-solid processing technology from experimental research to engineering, and the annual yield of the plant reached 5000 ten thousand pieces by the time 1996. Following Alumax, HMM (Hot Metal moving), Lindberg Corporation, CML International, and Formcast, in turn, have used semi-solid forming techniques to produce aluminum and magnesium alloy parts. In europe, italy is one of the earliest countries in which semi-solid processing technology was commercialized. The Italy Stampal-SPA company can produce round billet with diameter of about 100mm and length up to 4m, and utilizes semi-solid thixoforming technology to produce engine oil injection stop block, gear box cover and rocker arm for Ford automobile company, and the semi-solid aluminum alloy automobile rear suspension rack produced by the company has a left and right supporting blank weight of 7kg and very complicated shape. In addition, mm (magneti marelli) in italy also produced semi-solid aluminum alloy parts for some automotive companies, reaching 7500 parts in 2000. Japan is a country which turns the semi-solid processing technology to industrial application earlier in Asian countries, and in the later 80 s, 14 iron and steel enterprises and 4 nonferrous metal companies in Japan jointly establish Rheotech corporation, and the corporation invests 30 billion yuan to research and develop the technology and uses automobile parts as the preferred application object of semi-solid metal forming processing. Some other companies in japan have subsequently begun working on the production of semi-solid shaped parts, such as Speed Star Wheel, which has successfully used semi-solid forming technology to produce aluminum alloy hubs weighing about 5 kg.

The semi-solid forming technology is relatively late in the beginning of China, and compared with the technology in foreign countries, the research in the technical field of semi-solid metal forming in China is relatively lagged. In view of the current research situation in China, the semi-solid forming technology is gradually entering the industrial popularization and application stage, and although the whole industrial scale is relatively small, from the industrial attention, many new products are produced by adopting the semi-solid forming technology, and meeting staff of the semi-solid technology and application seminar are gradually increased every year. In recent years, research institutions such as Beijing university of science and technology, Qinghua university, southeast university, Harbin university of industry, northwest university of industry, non-ferrous metal research institute and the like in many domestic schools have made great progress in basic theoretical research on semi-solid forming technology, independent research and development and manufacturing of related equipment and breakthrough of key technology with the support of national '863 project', '985 project' and national natural science fund.

Throughout the research progress at home and abroad, the metal semi-solid forming technology is mainly applied to the field of automobiles at present, and parts such as brake actuating cylinders, steering knuckles, rocker arms, engine pistons, hubs and the like of the automobiles are produced by utilizing semi-solid die casting, die forging and injection forming processes of aluminum and magnesium alloys under most conditions, and the production technology tends to be mature. However, the technology is not developed and applied to aluminum, magnesium-based composite materials, other alloys and composite materials thereof, so that the technology for manufacturing the particle reinforced aluminum-based composite material electronic packaging shell by using the metal semi-solid forming technology has certain innovativeness and practicability, and can provide valuable theoretical basis and technical support for manufacturing similar products.

In addition, the present applicant has discovered, when studying the filling process of the semi-solid a356 aluminum alloy slurry, that the semi-solid slurry is highly susceptible to segregation and separation of liquid and solid phases during the filling process of the mold cavity, which is generally related to the shape and structure of the mold cavity and the filling speed, temperature and pressure of the slurry. It is believed that segregation and separation of the liquid and solid phases during forming can result in non-uniform structure and composition of the formed article, thereby adversely affecting its performance. And in another pair of SiC_(p)In the research of the/A356 composite material thixoextrusion molding, when observing the microstructure of the molding area, the distribution density of SiC particles is consistent with the flowing and distribution rule of the liquid phase in the semi-solid slurry, and the distribution density of SiC particles is gradually increased along with the increase of the filling stroke of the semi-solid slurry.

For the in-situ synthesized particle reinforced aluminum matrix composite, although the surface of the reinforced particle is pollution-free and the compatibility with the matrix is better than that of the aluminum matrix composite prepared by an external method, the volume fraction of the particles in the in-situ synthesized aluminum matrix composite is generally lower, and the volume percentage of the particles required by the aluminum matrix composite for electronic packaging shells is generally required to be more than 50%. Therefore, the invention skillfully utilizes the adverse factors of liquid and solid phase segregation and separation during semi-solid forming to realize the favorable conversion of preparing the high volume fraction aluminum matrix composite electronic packaging shell by using the low volume fraction particle reinforced aluminum matrix composite.

Disclosure of Invention

The invention aims to provide a method for utilizing low volume percent TiB₂Preparation of high volume fraction TiB from reinforced aluminum-based composite material₂The semi-solid forming process of the composite material electronic packaging shell overcomes the problems of poor plasticity, difficult forming and the like of an aluminum-based composite material, and has low production cost and simple operation.

The process comprises the following steps:

(1) at 10Drying the prepared aluminum-based composite material block at 0-120 ℃, heating and melting the aluminum-based composite material block by using a resistance furnace, and preserving heat for 25-35 minutes to ensure TiB₂The particles are uniformly distributed, and meanwhile, an electromagnetic stirring device is used for stirring the composite material melt.

(2) And (4) properly treating the composite material melt according to different semi-solid forming methods for carrying out the extrusion forming process in the step (4).

If a semi-solid rheoforming process is adopted, directly cooling the heat-insulated molten composite material to a semi-solid temperature range to obtain particle reinforced aluminum matrix composite material semi-solid slurry;

and (ii) if a semi-solid thixoforming process is adopted, pouring the composite material melt into a preset die for rapid cooling to obtain a thixoforming blank, cutting the blank into an ideal size according to actual requirements, and carrying out secondary induction heating on the blank until the blank is in a semi-solid temperature range during forming.

(3) Designing an electronic packaging shell semi-solid state extrusion die, and designing a forming cavity in the horizontal direction of the bottom edge of a concave die cavity of the extrusion die so as to ensure that liquid and solid phase segregation and separation can occur in the horizontal direction when semi-solid state slurry or blank is subjected to extrusion force in the vertical direction.

(4) Semi-solid extrusion forming is carried out on the electronic packaging shell: the forming temperature is determined by the temperature of a liquid-solid two-phase area of the composite material; the forming speed is controlled to be 90-150 mm/s; the preheating temperature of the die is 200-300 ℃; the forming pressure is set to be 450-650 kN; the pressure maintaining time is 6-10 s.

Preferably, the composite material in step (1) is TiB₂A356 composite or TiB₂The AlCu5MnCdV composite material is prepared by a medium-frequency induction heating furnace without atmosphere protection, and the melting temperature of a sample is 685-700 ℃.

Preferably, TiB is used in step (1)₂The matrix alloy of the/A356 composite material comprises the following components in percentage by mass: 6.5-7.5% of silicon, 0.30-0.45% of magnesium, 0.15-0.2% of titanium, 0.08-0.12% of iron, 0.05-0.10% of copper, 0.03-0.05% of manganese and the balance of aluminum; TiB₂AlCu5MnCdV composite materialThe matrix alloy comprises the following components in percentage by mass: 4.5-5.5% of copper, 0.03-0.06% of silicon, 0.32-0.38% of manganese, 0.10-0.18% of cadmium, 0.08-0.12% of vanadium, 0.13-0.18% of iron and the balance of aluminum. The volume percentage of the titanium boride reinforced particles in the composite material is 20-35%.

Preferably, the semi-solid temperature range in step (2) is determined by Differential Scanning Calorimetry (DSC), and reasonable parameters should be set according to the material properties when testing. For the composite material, single-disk DSC EC2000 is adopted, the heating rate is 10K/min, and TiB is measured₂The solidus temperature range of the solution of the/A356 composite material is 573.57-622.24 ℃; TiB₂The solidus temperature range of the AlCu5MnCdV composite material liquid is 551.28-646.31 ℃. And (4) performing integral calculation on the melting peak to obtain a relation curve graph of the liquid-phase volume fraction and the temperature of the composite material. In actual production, the liquid phase volume fraction is usually controlled to 15% to 35% for easy transportation.

Preferably, the casting temperature of the composite material slurry in the step (2) is 665-685 ℃, and the composite material slurry is cooled by circulating water cooling, so that the matrix alloy obtains fine spherical crystals, the segregation of reinforcing particles is reduced, and the strength of the material is further improved.

The invention has the advantages and positive progress effects that:

at present, the preparation method of the high volume fraction particle reinforced aluminum matrix composite mainly comprises a powder metallurgy method and a pressureless infiltration method, but the methods have the defects of complex equipment, high manufacturing cost or long production period, and meanwhile, the aluminum matrix composite has poor plasticity and difficult secondary processing, and the more the content of the reinforced particles is, the more easily cracks, holes and other defects appear in the composite.

The invention uses low TiB through the process of semi-solid metal forming₂Preparation of high TiB from volume fraction aluminum-based composite material₂The volume composite electronic package housing. On one hand, the matrix alloy in the semi-solid slurry or the blank is a uniform near-spherical structure, and meanwhile, the semi-solid slurry or the blank has high viscosity, so that the particle sedimentation caused by different densities of the matrix and the particles is avoided, and the agglomeration behavior of the reinforced particles is greatly reduced. On the other hand, by using a chargerThe segregation and separation phenomena of the semi-solid slurry or the blank and the rule that the volume fraction of the reinforced particles is consistent with the liquid phase distribution complete the ingenious transformation of the volume fraction of the reinforced particles from low to high in the process of the particle reinforced aluminum matrix composite material from the raw material to the finished product.

The invention uses the semi-solid forming process to realize the near-net forming manufacture of the electronic packaging shell with short flow and low cost, the shell part has good surface quality and mechanical property, and simultaneously the requirements of high thermal conductivity and low thermal expansion coefficient required by electronic packaging are also met, the method process expands the manufacturing approach of the electronic packaging shell, and provides favorable technical support for the development and production of other similar products.

Drawings

Fig. 1 is an electronic package housing part prepared in accordance with the present invention.

Fig. 2 is a lower die (female die) model of the shell semi-solid extrusion die of the present invention.

Fig. 3 is an assembled model of the shell semi-solid extrusion die of the present invention.

Detailed description of the preferred embodiments

Example 1: preparation of TiB Using semi-solid rheoforming Process₂the/A356 composite material electronic packaging shell component.

For TiB at 100 DEG C₂Drying the block raw material of the/A356 composite material, setting the melting temperature to 685 ℃, preserving the heat for 30min after the composite material is completely melted so as to ensure TiB₂The particles were uniformly distributed during which time electromagnetic stirring was applied to the melt, which was subsequently cooled to a semi-solid temperature of 575 ℃ by controlling the melt temperature. The composite material matrix A356 alloy comprises the following components in percentage by mass: 6.6-7.1% of silicon, 0.32-0.39% of magnesium, 0.18-0.2% of titanium, 0.09-0.11% of iron, 0.06-0.10% of copper, 0.04-0.05% of manganese and the balance of aluminum; TiB₂The reinforcing particles were 28% by volume. The design structure form is a mold for backward extrusion forming of the cup-shaped part, and an electronic packaging shell forming cavity is processed at the edge position of the bottom of the female mold cavity. Semi-solid TiB by simple slurry conveying device₂the/A356 composite material slurry is sent to the concave die cavity of the extrusion die, the preheating temperature of the die is 260 ℃, and graphite is adoptedAnd (3) a release agent. The extrusion force of the press is 580kN, the extrusion speed is 100mm/s, and the dwell time is 10 s.

The thin-wall electronic packaging shell part with complex shape, uniform tissue components and good mechanical property can be prepared by the scheme. Detected TiB in the shell parts₂The volume percent of reinforcing particles is about 52%.

Example 2: preparation of TiB Using semi-solid rheoforming Process₂the/AlCu 5MnCdV composite material electronic packaging shell part.

For TiB at 110 ℃₂Drying the AlCu5MnCdV composite material block raw material, setting the smelting temperature to be 690 ℃, preserving the heat for 30min after the composite material is completely melted so as to ensure TiB₂The particles are homogeneously distributed, during which time electromagnetic stirring is applied to the melt, which is subsequently cooled to a semi-solid temperature of 570 ℃. The composite material matrix AlCu5MnCdV alloy comprises the following components in percentage by mass: 4.7-5.1% of copper, 0.04-0.06% of silicon, 0.33-0.35% of manganese, 0.10-0.18% of cadmium, 0.08-0.12% of vanadium, 0.13-0.15% of iron and the balance of aluminum; TiB₂The reinforcing particles are 33% by volume. The design structure form is a mold for backward extrusion forming of the cup-shaped part, and an electronic packaging shell forming cavity is processed at the edge position of the bottom of the female mold cavity. Semi-solid TiB by simple slurry conveying device₂The AlCu5MnCdV composite material slurry is sent to a female die cavity of an extrusion die, the preheating temperature of the die is 280 ℃, and a graphite release agent is adopted. The extrusion force of the press is 600kN, the extrusion speed is 120mm/s, and the dwell time is 9 s.

The thin-wall electronic packaging shell part with complex shape, uniform tissue components and good mechanical property can be prepared by the scheme. Detected TiB in the shell parts₂The volume percent of reinforcing particles was about 58%.

Example 3: preparation of TiB Using semi-solid thixoforming Process₂the/AlCu 5MnCdV composite material electronic packaging shell part.

Firstly, TiB₂Sawing AlCu5MnCdV composite material into block materials with proper sizes, heating the block materials to a semi-solid temperature of 570 ℃ by using an induction furnace, and obtaining a composite material matrix AlCu5MnCThe mass percentage of each component in the dV alloy is as follows: 4.8-5.3% of copper, 0.05-0.06% of silicon, 0.35-0.37% of manganese, 0.14-0.16% of cadmium, 0.09-0.11% of vanadium, 0.14-0.16% of iron and the balance of aluminum; TiB₂The reinforcing particles are 31% by volume. The design structure form is a mold for backward extrusion forming of the cup-shaped part, and an electronic packaging shell forming cavity is processed at the edge position of the bottom of the female mold cavity. Rapidly clamp the semi-solid TiB₂The AlCu5MnCdV composite material blank is placed in a concave die cavity of an extrusion die, the preheating temperature of the die is 300 ℃, and a graphite release agent is adopted. The press extrusion was 610kN, the extrusion speed was 110mm/s and the dwell time was 7 s.

The thin-wall electronic packaging shell part with complex shape, uniform tissue components and good mechanical property can be prepared by the scheme. Detected TiB in the shell parts₂The volume percent of reinforcing particles is about 55%.