A kind of low radioactive spherical silicon powder and its preparation method and application

Abstract

The present invention discloses a low-radioactive spherical silicon micropowder and a preparation method and application thereof, belonging to the technical field of microsilicon powder. The purity of the spherical silicon micropowder prepared by the present invention is ≥99.95%, and the content of radioactive element U is ≤1×10 ‑10 g / g, the spherical silicon micropowder is prepared by an intelligently controlled integrated system, the integrated system comprising an input device, a processing unit, a transmission device, a testing device, an execution device, a control device and an output device; wherein the input device, the processing unit and the output device are connected by a transmission device, the testing device and the execution device are installed on the inner wall, valve or external device of the processing unit, the control device performs intelligent control on the integrated system, and high-purity, low-radioactive spherical silicon micropowder is prepared by the integrated system, which can avoid secondary pollution caused by air dust or external pollution in the traditional separation preparation method, thereby ensuring the high purity and low radioactivity of the spherical silicon micropowder.

Description

Technical Field

[0001] The invention relates to the technical field of silicon micropowder, in particular to low-radioactive spherical silicon micropowder and a preparation method and application thereof. Background Art

[0002] Epoxy molding compound (EMC) is a powder molding compound made of epoxy resin as the base resin, high-performance phenolic resin as the curing agent, silicon micropowder and other fillers, and a variety of additives. 97% of the global integrated circuit (IC) packaging materials use epoxy molding compound. The molding process is to extrude EMC into a special mold cavity by transfer molding, embed the semiconductor chip in it, and complete cross-linking and curing molding to form a semiconductor device with a certain structural appearance. The epoxy molding compound currently used is mainly composed of filler (60% to 90%), epoxy resin (less than 18%), curing agent (less than 9%), and additives (about 3%). In the molding process, the epoxy group of the epoxy resin is opened by heating to react chemically with the curing agent, producing a cross-linking and curing effect to become a thermosetting plastic. The epoxy molding compound cured in the molding mold constitutes the packaging shell. Microelectronic packaging requires high moisture resistance, low stress, low α rays, resistance to dip soldering and reflow soldering, and good molding process performance. In response to these requirements, epoxy molding compounds must be doped with inorganic fillers in the resin matrix. The inorganic fillers currently used are basically silica micropowder, with a content of up to 90.5%. It has the functions of reducing the thermal expansion coefficient of the molding compound, increasing thermal conductivity, reducing the dielectric constant, being environmentally friendly, flame retardant, reducing internal stress, preventing moisture absorption, increasing the strength of the molding compound, and reducing the cost of the molding compound.

[0003] Common silicon powders in microelectronic packaging include crystalline silicon powder, molten silicon powder and spherical silicon powder. Among them, spherical silicon powder has good fluidity, the highest filling amount can be achieved, the internal stress concentration is the smallest, the strength is the highest, the friction coefficient is small, and the mold service life is greatly improved. However, among the silicon isotopes, except for silicon 28, silicon 29, and silicon 30, which are stable, other isotopes (25-36) are radioactive and will release α rays when decaying to travel in the silicon material and form electron-hole pairs. This will form an electric field in the depletion region to induce charge drift, causing the transistor to suffer current disturbances, and in severe cases, soft errors will be formed. Studies have shown that uranium (U) is currently the main factor in the generation of α rays in spherical silicon powder. As an important component of integrated circuit packaging materials, spherical silicon powder must strictly control its uranium (U) element content (≤1ppb) to obtain high-purity and low-radioactive spherical silicon powder to meet the needs of large-scale integrated circuit packaging. Summary of the invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a low-radioactive spherical silicon powder and a preparation method and application thereof, which have the advantages of high purity and low radioactivity.

[0005] The technical solution for achieving the purpose of the present invention is as follows:

[0006] A low-radioactive spherical silicon micropowder, wherein the purity of the spherical silicon micropowder is ≥99.95% and the content of radioactive element U is ≤1×10 -10 g / g, the spherical silicon micropowder is prepared by an intelligently controlled integrated system, the integrated system comprises an input device, a processing unit, a transmission device, a testing device, an execution device, a control device and an output device; wherein the input device, the processing unit and the output device are connected via a transmission device, the testing device and the execution device are mounted on the inner wall, valve or external device of the processing unit, and the control device performs intelligent control on the integrated system, the intelligent control method comprises: firstly obtaining the elemental composition information of the ground silicon micropowder; then using unique hot coding to digitize and normalize the elemental composition information to obtain elemental composition characteristic information; finally, inputting the elemental composition characteristic information into a radioactivity and purity control model to output control parameters.

[0007] The input device includes a raw material warehouse and a storage tank; the processing unit includes a crushing device, a grinding device, a magnetic separation and screening device, an impurity removal device and a plasma spheroidization furnace; the transmission device includes a conveying pipeline; the testing device includes an in-situ LA-ICP-MS instrument, a temperature transmitter, and a pressure transmitter; the execution device includes an electronic scale controller, a flow meter, an electromagnetic valve and a stirring paddle controller; the output device includes an airflow classification device and a bag dust collector.

[0008] The storage tanks include a hydrochloric acid storage tank, a nitric acid storage tank, a hydrofluoric acid storage tank and a pure water storage tank, and the storage tanks are connected to the impurity removal device through a delivery pipeline and a solenoid valve.

[0009] The pulverizing device is a jet mill, and the grinding device can be selected from a ball mill or a vibration mill.

[0010] The magnetic separation and screening device is an electromagnetic induction device connected to the screening device. After being powered on, it can generate a magnetic field to absorb iron-containing substances such as magnetite and limonite in the quartz sand coarse material. The screening device can be selected from a vibrating screen, an ultrasonic vibrating screen, a rotary screen, a swing screen, etc. The mesh number of the screen is 800 to 1500 meshes, and the magnetic separation device is simultaneously turned on during the screening process to remove Fe impurities. The sieved silicon powder enters the impurity removal device, and the unsieved quartz sand returns to the grinding device for further grinding.

[0011] The impurity removal device is an acid-corrosion-resistant pickling reactor, such as a double-cone reactor with polytetrafluoroethylene as the inner wall material, and is equipped with a heating device, a stirring device, etc.

[0012] If necessary, the testing device may also include monitoring equipment such as an industrial television camera.

[0013] The element composition information includes element types and element contents, which are determined by in-situ LA-ICP-MS.

[0014] The element composition information is digitized using unique hot coding and based on the classification of element types that are soluble in acid. The content information corresponding to the digitized element composition is normalized to obtain element composition characteristic information. The normalization formula is: norm =(XX min ) / (X max -X min ), where X norm Normalized data, X is the original data, X max is the maximum value in the original data, X min is the minimum value in the original data.

[0015] The classification based on the element type that is soluble in acid includes: a. The classification of elements soluble in dilute hydrochloric acid or dilute caustic acid is {Ca, Fe, K, Li, Mg, Na, Ni, Sr}; b. The classification of elements soluble in hydrofluoric acid is {Th, Ti, Cr}; c. The classification of elements soluble in nitric acid is {U, Cu}; d. The classification of elements soluble in a mixture of hydrochloric acid, nitric acid and hydrofluoric acid is {Al, Zr}; e. The classification of elements soluble in concentrated hydrochloric acid is {Mn}.

[0016] The system control parameters control the composition, proportion, concentration, soaking time and temperature of the mixed acid by controlling the solenoid valve and temperature transmitter of the storage tank and the stirring paddle controller, thereby achieving the effect of controlling the purity and radiation value of the silicon micropowder.

[0017] Preferably, the radioactivity and purity control model is an algorithm model based on Random Forest, which is composed of multiple decision trees, each of which is independently constructed, which can reduce the risk of overfitting of the model and improve the accuracy and robustness of the prediction.

[0018] The radioactivity and purity control model is trained by conventional acid washing and purification data of quartz sand coarse material, and the model is regularly optimized according to the purity and radioactivity value data of spherical silicon micropowder produced by the integrated system of intelligent control.

[0019] The conventional pickling purification data are the pickling purification data of the laboratory stage. Specifically, the crystalline quartz sand coarse material or fused quartz sand coarse material from different origins or manufacturers is selected, and the element composition and content of the coarse material are determined by ICP. After magnetic separation, it is washed with at least one of hydrochloric acid, nitric acid, hydrofluoric acid and water until the purity is ≥99.99% and the U content is ≤1×10 -11g / g, the parameters obtained in the purification process including but not limited to the type, composition, ratio, content, number of acid washes, number of aqueous washes, temperature, soaking time, etc. are input into the radioactivity and purity control model for training, and each set of data is used as a decision tree, and there are no less than 10 decision trees.

[0020] Preferably, an in-situ LA-ICP-MS detector can be connected to the plasma spheroidization furnace to detect the elemental composition information of the purified spherical silicon powder and feed it back to the radioactivity and purity control model, thereby optimizing the model.

[0021] Another object of the present invention is to provide a method for preparing low-radioactive spherical silicon micropowder, comprising the following steps: crystallized quartz sand or fused quartz sand coarse material is put into a raw material bin, conveyed to a pulverizing device for pulverization after being measured by an electronic scale controller, the pulverized quartz sand coarse material enters a grinding device for grinding to obtain silicon micropowder, the silicon micropowder enters a magnetic separation and screening device to remove magnetic materials and passes through an 800-1500 mesh sieve, the unscreened silicon micropowder returns to the grinding device for grinding, the elemental composition of the sieved silicon micropowder is determined by in-situ LA-ICP-MS, and digitized and normalized to obtain elemental composition characteristic information, which is input into a radioactivity and purity control model to obtain control parameters, and the composition, proportion, concentration, immersion time and temperature of the mixed acid are controlled by controlling the solenoid valve and temperature transmitter of the storage tank and the stirring paddle controller to remove impurities and radioactive elements, and finally, after high-temperature spheroidization in a plasma spheroidization furnace, it is classified by an airflow classification device and collected in a bag dust collector for packaging.

[0022] Another object of the present invention is to protect the application of the low-radioactive spherical silicon powder in epoxy molding materials and copper-clad laminates.

[0023] Beneficial Effects

[0024] The present invention provides a low-radioactive spherical silicon micropowder and a preparation method and application thereof. The high-purity, low-radioactive spherical silicon micropowder is prepared through an integrated system, which can avoid the secondary pollution caused by air dust or external pollution in the traditional separation preparation method, and ensure the high purity and low radioactivity of the spherical silicon micropowder. In addition, the spherical silicon micropowder integrated system is automatically and intelligently controlled through intelligent control, and the element composition information of the silicon micropowder is converted into a coding language. Through model training, control parameters are output to control the composition, proportion, concentration, pickling times, sequence, soaking time and temperature of the acid or mixed acid, so as to achieve the effect of accurately controlling the purity and radiation value of the silicon micropowder, which can adapt to the purification needs of quartz ores from different sources, avoid the problem of product quality differences due to different raw material batches in the traditional pickling process, simplify the process flow, and ensure stable product quality, and also achieve accurate control of radioactive elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of an integrated system for producing spherical silicon powder.

[0026] In the figure: 110-raw material warehouse, 120-storage tank, 210-crushing device, 220-grinding device, 230-magnetic separation and screening device, 231-electromagnetic induction equipment, 232-sieve, 240-impurity removal device, 241-heating equipment, 242-stirring equipment, 250-plasma spheroidization furnace, 310-transport pipeline, 411-in-situ LA-ICP-MS instrument, 412-temperature transmitter, 413-pressure transmitter, 421-electronic scale controller, 422-solenoid valve, 510-airflow classification device, 520-bag dust collector.

[0027] Figure 2 Schematic diagram of the process of intelligent control of the integrated system. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0030] The raw materials used in the embodiments and comparative examples are described as follows:

[0031] Quartz sand coarse material 1: purchased from Guangdong Peninsula Quartz Sand Factory;

[0032] Example

[0033] A low-radioactive spherical silicon powder is prepared by an intelligently controlled integrated system. Figure 1 As shown, it includes an input device, a processing unit, a transmission device, a testing device, an execution device, a control device and an output device; wherein the input device, the processing unit and the output device are connected through a transmission device, the testing device and the execution device are installed on the inner wall, valve or external device of the processing unit, and the control device performs intelligent control on the integrated system, and the intelligent control method includes: firstly obtaining the element composition information of the ground silicon micropowder; then using unique hot coding to digitize and normalize the element composition information to obtain element composition characteristic information; finally, inputting the element composition characteristic information into the radioactivity and purity control model, and outputting the control parameters.

[0034] The input device includes a raw material bin 110 and a storage tank 120; the processing unit includes a crushing device 210, a grinding device 220, a magnetic separation and screening device 230, an impurity removal device 240 and a plasma spheroidization furnace 250; the transmission device includes a conveying pipeline 310; the testing device includes an in-situ LA-ICP-MS instrument 411, a temperature transmitter 412, and a pressure transmitter 413; the execution device includes an electronic scale controller 421, a flow meter, a solenoid valve 422 and a stirring paddle controller; the output device includes an airflow classification device 510 and a bag dust collector 520.

[0035] The storage tanks include a hydrochloric acid storage tank, a nitric acid storage tank, a hydrofluoric acid storage tank and a pure water storage tank, and the storage tanks are connected to the impurity removal device through a delivery pipeline and a solenoid valve. The concentrations of hydrochloric acid, nitric acid and hydrofluoric acid in the storage tanks are conventional concentrations available on the market, specifically, the concentration of hydrochloric acid is 35-37%, the concentration of nitric acid is 68-75%, and the concentration of hydrofluoric acid is 40%.

[0036] In a specific embodiment, the preparation method of spherical silicon powder comprises the following steps:

[0037] The quartz sand coarse material is put into the raw material warehouse, weighed and measured by an electronic scale controller, and then transported to the air flow mill for primary crushing. The crushed quartz sand coarse material enters the ball mill for grinding to obtain silicon micropowder, and the silicon micropowder enters the vibrating screen for screening. The mesh number of the vibrating screen is 1250 mesh, and the vibrating screen is equipped with an electromagnetic induction device. After power is turned on, it has magnetism and can absorb Fe-containing particles in the silicon micropowder. After the power is turned off, the magnetism disappears, and the Fe-containing particles are separated by a special pipeline. The large particles of silicon micropowder that have not been screened are returned to the grinding device for grinding, and the screened silicon micropowder enters the impurity removal device for further acid washing and water washing.

[0038] The impurity removal device is connected to the hydrochloric acid storage tank, the nitric acid storage tank, the hydrofluoric acid storage tank and the pure water storage tank, and the volume of the added acid and pure water is controlled by the solenoid valve. In addition, in the present invention, a certain amount of sample is automatically weighed every time period after the sieved silicon micropowder is dissolved in nitric acid and hydrofluoric acid and then enters the external in-situ LA-ICP-MS to determine its elemental composition, as shown in Table 1. It should be noted that the elemental composition information contained in the quartz sand coarse material from different sources is also different, and it is impossible to list all of them in the embodiments of the present invention. Based on the elemental composition information that quartz sand coarse material may contain in general, the classification based on the element type that can be dissolved in acid includes: a. The classification of those dissolved in dilute hydrochloric acid or dilute caustic acid is {Ca, Fe, K, Li, Mg, Na, Ni, Sr}; b. The classification of those dissolved in hydrofluoric acid is {Th, Ti, Cr}; c. The classification of those dissolved in nitric acid is {U, Cu}; d. The classification of those dissolved in a mixture of hydrochloric acid, nitric acid and hydrofluoric acid is {Al, Zr}; e. The classification of those dissolved in concentrated hydrochloric acid is {Mn}.

[0039] The obtained results are digitized using one-hot encoding, and the content of silicon powder is coded using minimum-maximum normalization. The normalization formula is: X norm =(XX min ) / (X max -X min ), where X norm Normalized data, X is the original data, X max is the maximum value in the original data, X min is the minimum value in the original data, and the element composition characteristic information is obtained, as shown in Table 2.

[0040] The element composition characteristic information is input into the radioactivity and purity control model to obtain the control parameters. The composition, proportion, concentration, soaking time and temperature of the mixed acid are controlled by controlling the solenoid valve and temperature transmitter of the storage tank and the stirring paddle controller to remove impurities and radioactive elements. In this embodiment, the impurity removal program output by the control parameters is: the first pickling: add concentrated hydrochloric acid in a volume of 1.2 times that of the silicon micropowder to the impurity removal device containing silicon micropowder, heat to 65°C and soak for 30 minutes, then stir for 10 minutes, and filter press; the second pickling: control the solenoid valves of the hydrochloric acid, nitric acid and hydrofluoric acid storage tanks and the pure water solenoid valve to configure the mixed acid solution in the impurity removal device. The program shows that the volume ratio of hydrochloric acid: nitric acid: hydrofluoric acid: water is 1:3:3:15, and it is heated to 50°C and soaked for 10 to 20 minutes and then slowly Stir slowly for 30 to 60 minutes, then filter press; third pickling: control the solenoid valves of the hydrochloric acid and nitric acid storage tanks and the pure water solenoid valve to configure the mixed acid solution in the impurity removal device, the program shows that the volume ratio of hydrochloric acid: nitric acid: water is 1:1:20, soak for 30 minutes and then slowly stir for 30 to 60 minutes, then filter press, and soak and wash with pure water for 1 to 3 times; finally, after high-temperature spheroidization in a plasma spheroidization furnace, it is classified by an airflow classification device and collected in a bag dust collector for packaging, and finally spherical silicon micropowder is obtained, and its chemical composition data is shown in Table 3

[0041] The final spherical silicon powder has a purity of ≥99.95% and a radioactive element U content of ≤1×10 -10 g / g,

[0042] In this embodiment, the radioactivity and purity control model is an algorithm model based on Random Forest, which is composed of multiple decision trees, each of which is independently constructed, which can reduce the overfitting risk of the model and improve the accuracy and robustness of the prediction.

[0043] The radioactivity and purity control model is trained by conventional acid washing and purification data of quartz sand coarse material, and the model is regularly optimized according to the purity and radioactivity value data of spherical silicon micropowder produced by the integrated system of intelligent control.

[0044] The conventional pickling purification data are the pickling purification data of the laboratory stage. Specifically, the crystalline quartz sand coarse material or fused quartz sand coarse material from different origins or manufacturers is selected, and the element composition and content of the coarse material are determined by ICP. After magnetic separation, it is washed with at least one of hydrochloric acid, nitric acid, hydrofluoric acid and water until the purity is ≥99.99% and the U content is ≤1×10 -11 g / g, the parameters obtained in the purification process including but not limited to the type, composition, ratio, content, number of acid washes, number of aqueous washes, temperature, soaking time, etc. are input into the radioactivity and purity control model for training, and each set of data is used as a decision tree, and there are no less than 10 decision trees.

[0045] In a specific embodiment, an in-situ LA-ICP-MS detector can be connected to the plasma spheroidization furnace to detect the elemental composition information of the purified spherical silicon powder and feed it back to the radioactivity and purity control model, thereby optimizing the model.

[0046] Table 1 Elemental composition information of silicon micropowder before impurity removal

[0047]

[0048]

[0049] Table 2 Elemental composition characteristic information of silicon micropowder before impurity removal

[0050] Classification Numericalization Normalization {Ca, Fe, K, Li, Mg, Na} {1,0,0,0} 1 {Ti, Cr} {0,1,0,0} 0.014839 {U, Cu} {0,0,1,0} 0 {Al, Zr} {0,0,0,1} 0.160291

[0051] Table 3 Chemical composition data of spherical silicon powder

[0052]

[0053]

[0054] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing low-radioactive spherical silicon powder, characterized in that: The method comprises the following steps: coarse crystalline quartz sand or fused quartz sand is put into a raw material bin, and is transported to a pulverizing device for pulverization after being measured by an electronic scale controller; the pulverized coarse quartz sand enters a grinding device for grinding to obtain silicon micropowder; the silicon micropowder enters a magnetic separation and screening device to remove magnetic materials and passes through an 800-1500 mesh sieve; the unscreened silicon micropowder is returned to the grinding device for grinding; the element composition of the sieved silicon micropowder is determined by in-situ LA-ICP-MS, and is digitized and normalized to obtain element composition characteristic information, which is input into a radioactivity and purity control model to obtain control parameters; the composition, proportion, concentration, immersion time, number of pickling times, sequence and temperature of the mixed acid are controlled by a solenoid valve and a temperature transmitter of a control storage tank and a stirring paddle controller to remove impurities and radioactive elements; finally, the mixed acid is spheroidized at high temperature in a plasma spheroidizing furnace, and is classified by an airflow classification device and collected in a bag dust collector for packaging; The purity of the spherical silicon powder is ≥99.95%, and the content of radioactive element U is ≤1×10 -10 g / g, the spherical silicon powder is prepared by an integrated system of intelligent control, the integrated system includes an input device, a processing unit, a transmission device, a testing device, an execution device, a control device and an output device; wherein the input device, the processing unit and the output device are connected by a transmission device, the testing device and the execution device are installed on the inner wall, valve or external device of the processing unit, and the control device performs intelligent control on the integrated system, the input device includes a raw material warehouse and a storage tank; the processing unit includes a crushing device, a grinding device, a magnetic separation and screening device, an impurity removal device and a plasma spheroidization furnace; the transmission device includes a conveying pipeline; the testing device includes an in-situ LA-ICP-MS instrument, a temperature transmitter, and a pressure transmitter; the execution device includes an electronic scale controller, a flow meter, a solenoid valve and a stirring paddle controller; the output device includes an airflow classification device and a bag dust collector; the storage tanks include hydrochloric acid storage tanks, nitric acid storage tanks, hydrofluoric acid storage tanks and pure water storage tanks, and the storage tanks are connected to the impurity removal device through a conveying pipeline and a solenoid valve; The intelligent control method comprises: firstly obtaining the element composition information of the ground silicon micropowder; then using unique hot coding to digitize and normalize the element composition information to obtain element composition characteristic information; finally inputting the element composition characteristic information into a radioactivity and purity control model to output control parameters; the element composition information is digitized based on the classification of element types soluble in acid using unique hot coding, and the content information corresponding to the digitized element composition is normalized to obtain the element composition characteristic information, and the classification based on element types soluble in acid comprises: a. the classification of dissolving in dilute hydrochloric acid or dilute nitric acid is {Ca, Fe, K, Li, Mg, Na, Ni, Sr}; b. the classification of dissolving in hydrofluoric acid is {Th, Ti, Cr}; c. the classification of dissolving in nitric acid is {U, Cu}; d. the classification of dissolving in a mixed acid of hydrochloric acid, nitric acid and hydrofluoric acid is {Al, Zr}; e. the classification of dissolving in concentrated hydrochloric acid is {Mn}; the radioactivity and purity control model is an algorithm model based on RandomForest.

2. The method for preparing low-radioactive spherical silicon powder according to claim 1, characterized in that: The element composition information includes element types and element contents, which are determined by in-situ LA-ICP-MS.

3. The method for preparing low-radioactive spherical silicon powder according to claim 1, characterized in that: The normalization processing formula is: norm =(XX min ) / (X max -X min ), where X norm Normalized data, X is the original data, X max is the maximum value in the original data, X min is the minimum value in the original data.

4. The method for preparing low-radioactive spherical silicon powder according to claim 1, characterized in that: The system control parameters control the composition, proportion, concentration, pickling times, sequence, soaking time and temperature of the acid or mixed acid by controlling the solenoid valve and temperature transmitter of the storage tank and the stirring paddle controller, thereby achieving the effect of controlling the purity and radiation value of the silicon micropowder.

5. The method for preparing low-radioactive spherical silicon powder according to claim 1, characterized in that: The radioactivity and purity control model is trained by conventional acid washing and purification data of quartz sand coarse material, and the model is regularly optimized according to the purity and radioactivity value data of spherical silicon micropowder produced by the integrated system of intelligent control.

6. Application of the low-radioactive spherical silicon powder prepared by the method for preparing low-radioactive spherical silicon powder according to any one of claims 1 to 5 in epoxy molding compounds and copper-clad laminates.

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