Low-alpha tin production device and production method

Abstract

This invention discloses a low-alpha tin production apparatus and method. The production apparatus includes: a heating furnace, a feeding system for conveying raw materials into the heating furnace, a discharging system for discharging reacted materials from the heating furnace to the outside, a vacuum pump group for evacuating the heating furnace, a condensation system for collecting lead vapor generated after heating the raw materials, and a control system. The condensation system is connected to the top of the heating furnace. The condensation system includes multiple condensers for condensing lead vapor. Adjacent condensers are connected to each other, to the top cover of the heating furnace, and to the vacuum pump group via gas channels. Each condenser is equipped with a gravity sensor below it to sense the weight of the condensed lead vapor. The production of low-alpha tin using this invention features low energy consumption, low pollution, and high efficiency. Energy consumption is approximately 50% of that of existing technologies, and the production process does not use strong acids or alkalis, making it environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of low-α tin preparation technology, specifically to a low-α tin production apparatus and production method. Background Technology

[0002] A logic error resulting from a change in the physical state of an integrated circuit is called a soft error. The bombardment of high-energy particles can cause erroneous changes in the physical state of an integrated circuit, thus creating a fault. When this fault manifests at the logic level, it results in a soft error. Soft errors can cause logic errors in integrated circuits, leading to control system malfunctions and incalculable losses, especially in the military field.

[0003] In the field of electronic packaging, the solder balls used for BGA packaging emit alpha rays, which can cause soft errors in the logic circuits of electronic products, thus affecting the normal use of the products. This is because the impurity element 210Pb in tin decays to produce 210Po, and 210Po releases alpha rays when it decays again. As semiconductor devices develop towards miniaturization and multifunctionality, the probability of soft errors in integrated circuits is constantly increasing. Therefore, developing low-alpha tin to solve the soft errors generated by integrated circuits has become very important.

[0004] In a published patent, Mitsubishi Corporation of Japan prepared low-alpha tin using an electrolytic refining method, and the resulting low-alpha tin had an X-ray emission level of 0.002 cph / cm. 2 However, the electrolytic preparation of low-alpha tin requires strong acids and lead nitrates, which can pollute the environment, making this method unsuitable for large-scale production. Chongqing Qunwei Co., Ltd. uses vacuum distillation and zone melting to prepare low-alpha BGA tin balls, and the alpha radiation of the tin balls is less than 0.001 cph / cm. 2 However, tin needs to be heated to 1400℃-1600℃, which not only results in incomplete lead purification but also low production efficiency and high energy consumption, with an energy consumption of about 25-30 kWh / kg. Dongguan Yong'an Technology Co., Ltd. uses a combination of vacuum distillation and laser isotope separation to prepare low-alpha metallic tin. Although laser isotope separation can directly remove 210Pb, the energy consumption is too high, exceeding 50 kWh / kg. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a low-alpha tin production apparatus and method. The production of low-alpha tin using the apparatus of this invention features low energy consumption, low pollution, and high efficiency, with energy consumption approximately 50% of that of existing technologies. Furthermore, the production process does not use strong acids or alkalis, making it environmentally friendly.

[0006] To achieve the above objectives, the specific solution adopted by the present invention is as follows:

[0007] A low-alpha tin production apparatus, comprising:

[0008] A heating furnace for heating raw materials placed therein;

[0009] A feeding system for conveying raw materials into a heating furnace, the feeding system being connected to the top of the heating furnace;

[0010] A discharge system is provided for discharging the reacted material from the heating furnace to the outside of the furnace, and the discharge system is connected to the bottom of the heating furnace.

[0011] A condensation system is used to collect lead vapor generated after the raw materials are heated. The condensation system is connected to the top of the heating furnace. The condensation system includes multiple condensers for condensing lead vapor. Adjacent condensers are connected to each other, between condensers and the top cover of the heating furnace, and between condensers and the vacuum pump group through gas channels. Each condenser is equipped with a gravity sensor below it to sense the weight of the condensed lead vapor.

[0012] A vacuum pump unit is used to evacuate the heating furnace, and the vacuum pump unit is connected to the end of the condensation system away from the heating furnace.

[0013] The control system is connected to the heating furnace, feeding system, unloading system, condensation system, and vacuum pump group.

[0014] Furthermore, the heating furnace includes a furnace body and an upper cover for sealing the furnace body. Inside the furnace body, a cylindrical crucible, a heat preservation ring, and an induction coil are arranged coaxially from the center line outwards. The bottom of the cylindrical crucible is provided with a sealing plate gate valve for receiving raw materials. The control system can control the sealing plate gate valve to rotate 90° downwards from the horizontal position.

[0015] Furthermore, the feeding system includes a hopper, a primary feeding channel, and a secondary feeding channel connected in sequence. A feeding gate valve is provided between the primary feeding channel and the secondary feeding channel. The end of the secondary feeding channel away from the feeding gate valve is connected to the top cover of the heating furnace.

[0016] Furthermore, the unloading system includes an upper unloading channel, a lower unloading channel, an unloading gate valve, a mold, and an unloading trolley. The upper unloading channel is connected to the bottom of the furnace body, the unloading gate valve is located between the upper unloading channel and the lower unloading channel, the mold is located inside the unloading trolley, and the mold is located below the lower unloading channel. By opening the unloading gate valve, the material after the reaction can be controlled to flow from the heating furnace into the mold.

[0017] Furthermore, a cooling water pipe for cooling the reacted material is provided outside the upper unloading channel.

[0018] Furthermore, a filter screen for filtering gas is installed in the gas passage between the condenser and the vacuum pump unit.

[0019] A method for producing low-alpha tin using the aforementioned low-alpha tin production apparatus mainly includes the following steps:

[0020] (1) Start the control system and close all gate valves;

[0021] (2) Add industrial pure tin as raw material. The raw material enters the primary feeding channel from the silo.

[0022] (3) Close the feed inlet of the silo and turn on the vacuum pump unit to continuously draw a vacuum until the vacuum level is lower than 10 Pa.

[0023] (4) Open the feed gate valve to allow the raw materials to enter the heating furnace;

[0024] (5) The heating furnace starts working. When the heating furnace heats to 1800-1900℃, the lead begins to volatilize. The generated lead vapor enters the condensation system. The heating furnace is kept at 1800-1900℃ until the readings of the gravity sensors in the condensation system do not change significantly within 5-15 minutes. The reaction ends then.

[0025] (6) First open the cooling water pipe, then open the sealing plate gate valve and the unloading gate valve so that the reacted material enters the mold after cooling to form welding rods;

[0026] (7) Close the discharge gate valve to complete the first round of raw material purification;

[0027] (8) Repeat the above steps to start the second round of feeding to ensure that the heating furnace continues to work.

[0028] Furthermore, during the production process, when the reading of any gravity sensor reaches its upper limit, the control system is shut down, the condenser is removed, the lead adhering to the condenser is taken out, the condenser is cleaned and reinstalled in its original position, and then work can resume.

[0029] Beneficial effects:

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] (1) Using induction heating, compared with electrolytic refining, it does not require the use of strong acids and lead nitrate, which is environmentally friendly;

[0032] (2) The heating speed is fast. Compared with electrolytic refining and laser isotope separation, the energy consumption is low, the production efficiency is high, and the product quality is good. For example, the final product obtained by electrolytic refining will be affected by electrolyte impurities, while the product obtained by this method is less affected by reaction factors.

[0033] (3) The production method is simple. Compared with electrolytic refining and laser isotope separation, the production process is shorter. For example, electrolytic refining requires control of the addition of solution, the speed of stirring and electrolysis parameters. This method is simple to operate and easy to industrialize. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the production apparatus in this invention.

[0035] Illustration markings:

[0036] 1. Feeding system; 11. Hopper; 12. Primary feed channel; 13. Feed gate valve; 14. Secondary feed channel;

[0037] 2. Condensation system, 21. Primary gas passage, 22. Primary condenser, 23. Primary gravity sensor, 24. Secondary gas passage, 25. Secondary condenser, 26. Secondary gravity sensor, 27. Tertiary gas passage, 28. Filter screen;

[0038] 3. Vacuum pump set;

[0039] 4. Control system;

[0040] 5. Heating furnace; 51. Top cover; 52. Furnace body; 53. Insulation ring; 54. Induction coil; 55. Straight cylindrical crucible; 56. Sealing plate gate valve.

[0041] 6. Unloading system; 61. Upper unloading channel; 62. Unloading gate valve; 63. Lower unloading channel; 64. Mold; 65. Unloading trolley;

[0042] 7. Cooling water pipes. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0044] A low-alpha tin production apparatus mainly includes:

[0045] A heating furnace 5, which is used to heat the raw materials placed therein;

[0046] Feeding system 1, which is used to feed raw materials into heating furnace 5, and is connected to the top of heating furnace 5;

[0047] The unloading system 6 is used to discharge the reacted material in the heating furnace 5 to the outside of the furnace, and the unloading system 6 is connected to the bottom of the heating furnace 5.

[0048] The condensing system 2 is used to collect lead vapor generated after the raw materials are heated. The condensing system 2 is connected to the top of the heating furnace 5. The condensing system 2 includes multiple condensers for condensing lead vapor. Adjacent condensers are connected to each other, between condensers and the top cover of the heating furnace 5, and between condensers and vacuum pump group 3 through gas channels. Each condenser is equipped with a gravity sensor below it to sense the weight of the condensed lead vapor.

[0049] Vacuum pump assembly 3 is used to evacuate the heating furnace 5. The vacuum pump assembly 3 is connected to the end of the condensing system 2 away from the heating furnace 5.

[0050] The control system 4 is connected to the heating furnace 5, the feeding system 1, the unloading system 6, the condensation system 2, and the vacuum pump group 3.

[0051] like Figure 1 As shown, the feeding system 1 includes a hopper 11, a primary feeding channel 12, a feeding gate valve 13, and a secondary feeding channel 14. The hopper 11 has a feed inlet at its top, and is used to receive raw materials poured in through the feed inlet. The primary feeding channel 12 connects the hopper 11 and the feeding gate valve 13, and is used to transport raw materials. The feeding gate valve 13 is located between the primary feeding channel 12 and the secondary feeding channel 14, and is connected to both. It is used to connect and block the primary feeding channel 12 and the secondary feeding channel 14. The flow of raw materials from the primary feeding channel 12 into the secondary feeding channel 14 can be controlled by opening and closing the feeding gate valve 13, and the secondary feeding channel 14 is also kept airtight when closed. The secondary feeding channel 14 is connected to the upper cover 51 of the heating furnace 5, and is used to allow raw materials to flow into the heating furnace 5.

[0052] The heating furnace 5 includes a furnace body 52 and an upper cover 51 for sealing the furnace body 52. ​​Inside the furnace body 52, a cylindrical crucible 55, a heat-insulating ring 53, and an induction coil 54 are arranged coaxially from the center line outwards. The bottom of the cylindrical crucible 55 is provided with a sealing plate gate valve 56 for receiving raw materials. The control system 4 can control the sealing plate gate valve 56 to rotate downwards by 90° from a horizontal position. Specifically, the upper cover 51 is made of 304 stainless steel, and the top of the upper cover 51 is provided with an observation hole for observing the reaction of the raw materials. The cylindrical crucible 55 is used to ensure that the raw materials are heated evenly, and the heat-insulating ring 53 is used to keep the cylindrical crucible 55 warm.

[0053] As a preferred option, the insulation ring 53 can be made of ordinary refractory materials, castables, and alumina, etc. More preferably, it can be made of corundum, which has good high-temperature insulation and mechanical strength, as well as high thermal conductivity and low thermal expansion coefficient.

[0054] The unloading system 6 includes an upper unloading channel 61, a lower unloading channel 63, an unloading gate valve 62, a mold 64, and an unloading trolley 65. The upper unloading channel 61 is connected to the bottom of the furnace body 52. ​​The unloading gate valve 62 is located between the upper unloading channel 61 and the lower unloading channel 63. The mold 64 is located inside the unloading trolley 65 and below the lower unloading channel 63. The unloading gate valve 62 can be opened to control the flow of the material after the high-temperature reaction from the heating furnace 5 into the mold 64, while closing it can ensure the sealing of the heating furnace 5. The mold 27 is located at the bottom of the entire device and is used to collect the reacted material so that the reacted material forms welding rods.

[0055] The upper unloading channel 61 is equipped with a cooling water pipe 7, which is used to cool the reacted material so that the reacted material flows into the mold 64 after cooling down.

[0056] In detail, Figure 1 In the condensation system 2, there are primary gas channels 21, primary condensers 22, primary gravity sensors 23, secondary gas channels 24, secondary condensers 25, secondary gravity sensors 26, tertiary gas channels 27, and filters 28. The primary gas channel 21 is connected to the upper cover 51 of the heating furnace 5 and is used to transfer lead vapor to the primary condenser 22. The primary condenser 22 is located between the primary gas channels 21 and 24 and is used to condense lead vapor, collecting impurities and preventing impurity gases from contaminating the vacuum pump assembly 3. The secondary gas channel 24 is located between the primary condensers 22 and 25 and is used to transfer the gas after one condensation. The secondary condenser 25 is located between the secondary gas channels 24 and tertiary gas channels 27 and is used for secondary condensation of the gas, collecting any remaining impurities and preventing impurity gases from contaminating the vacuum pump. The tertiary gas channel 27 is located between the secondary condensers 25 and the vacuum pump assembly 3 and is used to transfer the gas after two condensations. The filter screen 23 is located on the tertiary gas channel 27 and is used to filter the gas, serving as a third collection of impurities in the gas to prevent impurities from contaminating the vacuum pump. The primary gravity sensor 23 is located below the primary condenser 22 and is used to sense the weight after condensing impurities. The secondary gravity sensor 26 is located below the secondary condenser 25 and is used to sense the weight after a second collection of impurities. When the readings of the primary gravity sensor 23 and the secondary gravity sensor 26 no longer increase, it indicates that the impurities have been basically collected, and the discharge gate valve 62 can be opened to discharge the material, while the next round of feeding begins.

[0057] Vacuum pump unit 3 is located on the far right of the entire heating furnace 5. It is used to draw a vacuum to ensure that the furnace is in a vacuum state and that the vacuum degree is below 10 Pa.

[0058] In detail, the control system 4 is located on the lower right side of the main body of the heating furnace 5, and is used to control the opening and closing of the gate valve and the opening and closing of the vacuum pump group 3.

[0059] A method for producing low-alpha tin specifically includes the following steps:

[0060] (1) Start control system 4 and close all gate valves;

[0061] (2) Add raw material industrial pure tin, the raw material enters the primary feeding channel 12 from the material bin 11;

[0062] (3) Close the feed inlet of hopper 11, turn on vacuum pump group 24, and continuously draw vacuum until the vacuum level is lower than 10pa.

[0063] (4) Open the feed gate valve 13 to allow the raw material to enter the heating furnace 5;

[0064] (5) When the heating furnace 5 starts working, the lead begins to volatilize when the heating furnace 5 is heated to 1800-1900℃. The generated lead vapor enters the condensation system 2 (enters the primary condenser 22 through the primary gas channel 21. After one crystallization, the gas enters the secondary condenser 25 through the secondary gas channel 24. The remaining impurities undergo secondary crystallization). The heating furnace 5 is kept at 1800-1900℃ until the readings of the primary gravity sensor 23 and the secondary gravity sensor 26 no longer change significantly within 10 minutes. The reaction ends then.

[0065] (6) First open the cooling water pipe 7, then open the sealing plate gate valve 56 through the control system 4, and at the same time open the unloading gate valve 62. After the material is cooled by the cooling water, it enters the mold 64 to form a welding rod.

[0066] (7) Close the unloading gate valve 62 to complete the first round of raw material purification.

[0067] (8) Repeat the above steps to start the second round of feeding to ensure that the heating furnace 5 continues to work.

[0068] It should be noted that during the production process, when the readings of any gravity sensor 23 or 26 reach the upper limit, the control system 4 is shut down, the condensers 22 and 25 are removed, the lead adhering to the condensers 22 and 25 is removed, the condensers 22 and 25 are cleaned and reinstalled in their original positions, and then the operation can be restarted.

[0069] The obtained samples were subjected to alpha ray counting tests, and the following test results were obtained. The experimental results are shown in Table 1.

[0070] Table 1. Results of α-ray concentrations before and after the reaction of the raw materials.

[0071] Sample number 1 2 3 4 5 <![CDATA[Alpha ray quantity before reaction (cph / cm 2 )]]> 1.2 1.3 1.2 1.5 1.4 <![CDATA[Alpha ray quantity after reaction (cph / cm 2 )]]> 0.0005 0.0007 0.0005 0.0005 0.0006

[0072] As shown in Table 1, the solder bars produced using the production method of the present invention are low-α solder bars.

[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A low-α tin production apparatus, characterized in that, include: A heating furnace for heating raw materials placed therein; A feeding system for conveying raw materials into a heating furnace, the feeding system being connected to the top of the heating furnace; A discharge system is provided for discharging the reacted material from the heating furnace to the outside of the furnace, and the discharge system is connected to the bottom of the heating furnace. A condensation system is used to collect lead vapor generated after the raw material is heated to 1800~1900℃. The condensation system is connected to the top of the heating furnace. The condensation system includes multiple condensers for condensing lead vapor. Adjacent condensers are connected to each other, between condensers and the top cover of the heating furnace, and between condensers and the vacuum pump group through gas channels. Each condenser is equipped with a gravity sensor below it to sense the weight of the condensed lead vapor. A vacuum pump unit is used to evacuate the heating furnace, and the vacuum pump unit is connected to the end of the condensation system away from the heating furnace. The control system is connected to the heating furnace, feeding system, unloading system, condensation system, and vacuum pump group.

2. The low-α tin production apparatus according to claim 1, characterized in that, The heating furnace includes a furnace body and an upper cover for sealing the furnace body. Inside the furnace body, a cylindrical crucible, a heat preservation ring, and an induction coil are arranged coaxially from the center line outwards. The bottom of the cylindrical crucible is provided with a sealing plate gate valve for receiving raw materials. The control system can control the sealing plate gate valve to rotate 90° downwards from the horizontal position.

3. The low-α tin production apparatus according to claim 2, characterized in that, The feeding system includes a hopper, a primary feeding channel and a secondary feeding channel connected in sequence. A feeding gate valve is provided between the primary feeding channel and the secondary feeding channel. The end of the secondary feeding channel away from the feeding gate valve is connected to the top cover of the heating furnace.

4. A low-α tin production apparatus according to claim 3, characterized in that, The unloading system includes an upper unloading channel, a lower unloading channel, an unloading gate valve, a mold, and an unloading trolley. The upper unloading channel is connected to the bottom of the furnace body. The unloading gate valve is located between the upper and lower unloading channels. The mold is located inside the unloading trolley and below the lower unloading channel. By opening the unloading gate valve, the material after the reaction can be controlled to flow from the heating furnace into the mold.

5. A low-α tin production apparatus according to claim 4, characterized in that, The upper unloading channel is equipped with a cooling water pipe for cooling the material after the reaction.

6. A low-α tin production apparatus according to claim 1, characterized in that, A filter screen for filtering gas is installed in the gas passage between the condenser and the vacuum pump unit.

7. A method for producing low-α tin using the low-α tin production apparatus of claim 5, characterized in that, The main steps include the following: (1) Start the control system and close all gate valves; (2) Add industrial pure tin as raw material. The raw material enters the primary feeding channel from the silo. (3) Close the feed inlet of the silo and turn on the vacuum pump unit to continuously draw a vacuum until the vacuum level is lower than 10 Pa; (4) Open the feed gate valve to allow the raw materials to enter the heating furnace; (5) The heating furnace starts working. When the heating furnace heats to 1800~1900℃, the lead begins to volatilize. The generated lead vapor enters the condensation system. The heating furnace is kept at 1800~1900℃ until the readings of each gravity sensor in the condensation system do not change significantly within 5-15 minutes. The reaction ends then. (6) First open the cooling water pipe, then open the sealing plate gate valve and the unloading gate valve so that the reacted material enters the mold after cooling to form welding rods; (7) Close the discharge gate valve to complete the first round of raw material purification; (8) Repeat the above steps to start the second round of feeding to ensure that the heating furnace continues to work.

8. A method for producing low-α tin according to claim 7, characterized in that: During production, when any gravity sensor reading reaches its upper limit, the control system is shut down, the condenser is removed, the lead adhering to the condenser is taken out, the condenser is cleaned and reinstalled in its original position, and then work can resume.

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