Silver-based brazing filler metal chip desoldering method

Abstract

The invention belongs to the field of chip recovery, and particularly relates to a silver-based brazing filler metal chip desoldering method which comprises the following steps: S1, smelting a mixed alloy to obtain a liquid alloy; s2, liquid alloy is applied to the to-be-removed part of the silver-based brazing filler metal, and the to-be-removed part is wrapped by the liquid alloy; performing ultrasonic treatment on the liquid alloy for 1-100 seconds to obtain the desoldered silver-based brazing filler metal; in the mixed alloy, the weight percentage of gallium is more than 50%; the part to be removed is an interconnection chip of the silver-based brazing filler metal chip. Compared with previous chip dismounting methods such as manual dismounting and remelting dismounting, the method has the advantages that the chip welded by the silver-based brazing filler metal can be effectively dismounted, and the dismounted chip is high in integrity and has maintenance value; when the chip interconnection is removed by adopting the chip interconnection removing method, the chip interconnection can be quickly removed in a short time, and the chip dismounting efficiency is greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of chip recycling, and in particular relates to a method for desoldering a silver-based solder chip. Background Art

[0002] There are usually two ways to disassemble and repair chips: manual disassembly and remelting. Since solder is usually used to connect the chip to the printed circuit board, the connection strength is high, and it is difficult to completely disassemble it by manual disassembly. Even if it is removed, the chip will be damaged to varying degrees, which is not conducive to the disassembly and repair of the chip; the remelting disassembly method is to heat the chip welding layer to remelt the solder in it for disassembly. The integrity of the chip disassembled by this method is generally good, but there is a risk of damaging the printed circuit board, chip, and other components due to high temperature, and the remelting disassembly method cannot disassemble high-temperature service solder such as silver-based solder. Silver-based solder has the characteristics of low-temperature welding and high-temperature service, and has been widely used in the packaging of core chips in various fields. These chips are expensive, but can only be repaired by manual disassembly. The losses caused by this are difficult to measure each year, and the maintenance cost is high, the efficiency is low, and the cycle is long.

[0003] The prior art CN202011620689.X discloses a chip desoldering and recovery device, comprising a shell, a shell cavity being provided in the shell, a chip detection device being provided in the shell cavity, the chip detection device comprising a detection mounting plate, and the detection mounting plate being fixedly arranged on the upper inner wall of the shell cavity. The invention has a built-in chip detection device, which can separate good and bad chips through detection by correcting the chip position, thereby improving the recovery efficiency of good chips. The invention has a built-in chip heating desoldering and recovery device, which can detach the chip from the PCB board by performing air-heat desoldering treatment on the chip.

[0004] Prior art CN213256240U provides a chip recovery device, comprising: a loading platform, a first heating unit and a second heating unit. The loading platform is suitable for carrying a chip module. The first heating unit is suitable for being located above the chip module. The second heating unit is located at the side of the loading platform. The chip recovery device provided by the utility model can improve the heating efficiency by setting up a double heating unit. In addition, it can adapt to chip modules of different structures.

[0005] However, the above two existing technologies both use high temperature to separate metal objects from plastic plates. On the one hand, high temperature will produce a large amount of toxic gas, so the toxic gas needs to be purified before it can be discharged, which increases the recycling cost; on the other hand, the above two comparative documents still cannot dismantle the silver-based solder chip that serves at high temperature, which will damage the chip. Summary of the invention

[0006] The object of the present invention is to provide a method for desoldering a silver-based solder chip without damaging the chip.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for desoldering a silver-based solder chip comprises the following steps:

[0009] S1, melting the mixed alloy to obtain a liquid alloy;

[0010] S2, applying liquid alloy to the part to be released of the silver-based solder, so that the part to be released is wrapped by the liquid alloy; ultrasonically treating the liquid alloy for 1-100s to obtain the desoldering silver-based solder;

[0011] In the mixed alloy, gallium accounts for more than 50% by weight;

[0012] The part to be released is an interconnection chip of a silver-based solder chip.

[0013] In one preferred embodiment, the mixed alloy further includes one or more of indium, tin, zinc, copper, silver, aluminum, bismuth, cobalt, titanium, and iron.

[0014] In one of the preferred embodiments, the mixed alloy includes, by weight, 50-90 parts of gallium, 10-50 parts of indium, 0-50 parts of tin, 0-50 parts of zinc, 0-50 parts of copper, 0-50 parts of silver, 0-50 parts of aluminum, 0-50 parts of bismuth, 0-50 parts of cobalt, 0-50 parts of titanium and 0-50 parts of iron.

[0015] In one preferred embodiment, the mixed alloy comprises, by weight, 50-70 parts of gallium, 15-25 parts of indium, and 5-15 parts of tin.

[0016] In one preferred embodiment, the mixed alloy comprises 70-80 parts of gallium and 20-30 parts of indium by weight.

[0017] In one preferred embodiment, the mixed alloy comprises, by weight, 50-70 parts of gallium, 1-5 parts of zinc, and 5-15 parts of tin.

[0018] In one preferred embodiment, the silver-based solder is cleaned before desoldering.

[0019] In one preferred embodiment, the cleaning step is: use a detergent to clean the dirt, oil stains and dust on the silver-based solder, and then use hot air to dry it to ensure that the chip surface and its surroundings are dry and clean to obtain the silver-based solder to be released.

[0020] In one preferred embodiment, the cleaning agent is anhydrous ethanol or detergent.

[0021] In one preferred embodiment, the interconnection chip is a solder connection between a silver-based solder and a printed circuit board.

[0022] In one preferred embodiment, the interconnection chip is made of one or more of silver, copper and zinc.

[0023] In one preferred embodiment, the welding method includes a low melting point alloy welding method and a bonding method.

[0024] In one preferred embodiment, the nominal melting point of the liquid alloy is 5°C to 120°C.

[0025] In one preferred embodiment, the smelting temperature is 100°C to 2000°C.

[0026] In one preferred embodiment, the ultrasonic amplitude is 0.1 μm to 100 μm, the ultrasonic frequency is 20 kHz to 50 kHz, and the ultrasonic power is 100 W to 10000 W.

[0027] In one of the preferred embodiments, the applying is performed by syringe injection or dispensing with a dispensing machine.

[0028] The present invention utilizes the fact that gallium can solid-dissolve silver under certain conditions. When a gallium-based liquid metal with appropriate fluidity and liquid state at room temperature is used to dissolve the silver-based solder, the silver in the solder will gradually solid-dissolve and enter the gallium-based liquid metal. The gallium-based liquid metal is liquid metal at room temperature and can freely flow into the narrow gap of the welding interface to dissolve the silver in the silver-based solder, thereby destroying the interconnection between the chip and the printed circuit board. Ultrasonic vibration is then used to accelerate this process, thereby realizing the function of disconnecting the chip interconnection in a short time.

[0029] The beneficial effects of the present invention are:

[0030] 1. Compared with the previous chip disassembly methods such as manual disassembly and remelting disassembly, the present invention can effectively disassemble the chip soldered by silver-based solder, and the disassembled chip has high integrity and has maintenance value;

[0031] 2. The present invention is used to release chip interconnections, which can quickly release chip interconnections in a short time, greatly improving the efficiency of chip disassembly;

[0032] 3. Gallium-based liquid metal is easy to recycle and clean after use. It can be recycled many times. It is an environmentally friendly invention. The entire operation process does not produce any toxic waste liquid or waste gas.

[0033] 4. The process of the present invention is simple, easy to implement, low-cost, and can be achieved under normal atmospheric temperature without heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of desoldering of a silver-based solder chip of the present invention; DETAILED DESCRIPTION

[0035] The present invention is not limited to the following specific embodiments. A person skilled in the art can implement the present invention in various other specific embodiments according to the contents disclosed in the present invention, or any simple changes or modifications made to the design structure and ideas of the present invention fall within the protection scope of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0036] Example 1

[0037] like Figure 1 As shown, a chip desoldering method based on the gallium-based liquid metal solid solution principle is specifically completed in the following steps:

[0038] 1. Preparation of interconnected chips to be released: Take a printed circuit board with a chip to be desoldered and place it on the work platform. Use a cotton swab dipped in anhydrous ethanol to wipe the dirt, oil stains and dust on the surface of the chip and its surroundings. Then use a hair dryer to dry it with hot air for 1 minute to obtain a clean interconnected chip to be released.

[0039] 2. Preparation of gallium-based liquid metal: Weigh 68.5g of pure gallium, 21.5g of pure indium particles, and 10g of pure tin particles, and place them together in a 50ml crucible. The melting temperature is selected to be 300℃, and the melting time is 30min. After cooling at room temperature for 1h, the liquid metal is collected with a syringe to obtain gallium-indium-tin eutectic liquid metal with a nominal melting point of 5℃.

[0040] 3. Disconnect the chip interconnection: Take out the interconnected chip to be disconnected obtained in step 1 and place it together with the printed circuit board on a clean work platform to keep it level. Use a syringe to apply an appropriate amount of gallium indium tin liquid metal around the chip so that the liquid metal completely wraps the solder. Set the ultrasonic amplitude to 5μm, the ultrasonic frequency to 35kHz, the ultrasonic duration to 300s, and the ultrasonic power to 300W. Turn off the ultrasonic power after 300s and use tweezers to carefully remove the chip. Then use a clean syringe to collect most of the liquid metal first, and then use a cotton swab dipped in anhydrous ethanol to wipe the chip welding surface, gather the gallium indium tin liquid metal, and then use a syringe to collect it to complete the recovery of the gallium-based liquid metal. Complete the rapid desoldering of the chip soldered with silver-based solder.

[0041] Example 2

[0042] A chip desoldering method based on the gallium-based liquid metal solid solution principle is specifically completed in the following steps:

[0043] 1. Preparation of interconnected chips to be released: Take a printed circuit board with a chip to be desoldered and place it on the work platform. Use a cotton swab dipped in detergent to wipe the dirt, oil stains and dust on the surface of the chip and its surroundings. Then use a hair dryer to dry it with hot air for 1 minute to obtain a clean interconnected chip to be released.

[0044] 2. Preparation of gallium-based liquid metal: Weigh 75.5g of pure gallium and 24.5g of pure indium particles by weight, place them together in a 50ml crucible, select the melting temperature to be 200℃, and melt for 30min. After cooling at room temperature for 1h, put it into the needle of the dispensing machine to obtain gallium-indium liquid metal with a nominal melting point of 15.5℃;

[0045] 3. Disconnect the chip interconnection: Take out the interconnected chip to be disconnected obtained in step 1, and place it together with the printed circuit board or the device with the printed circuit board on a clean work platform to keep it level. Use a handheld dispensing needle to apply an appropriate amount of gallium-indium liquid metal around the chip so that the liquid metal completely wraps the solder. Set the ultrasonic amplitude to 8μm, the ultrasonic frequency to 30kHz, the ultrasonic duration to 300s, and the ultrasonic power to 500W. Turn off the ultrasonic power after 300s, and use tweezers to carefully remove the chip. Then use a clean syringe to collect most of the liquid metal first, and then use a cotton swab dipped in anhydrous ethanol to wipe the chip welding surface, gather the gallium-indium liquid metal and collect it again to complete the recovery of gallium-based liquid metal. Complete the rapid desoldering of the chip soldered with silver-based solder.

[0046] Example 3

[0047] A chip desoldering method based on the gallium-based liquid metal solid solution principle is specifically completed in the following steps:

[0048] 1. Preparation of interconnected chips to be released: Take a printed circuit board with a chip to be desoldered and place it on the work platform. Use a cotton swab dipped in anhydrous ethanol to wipe the dirt, oil stains and dust on the surface of the chip and its surroundings. Then use a hair dryer to dry it with hot air for 1 minute to obtain a clean interconnected chip to be released.

[0049] 2. Preparation of gallium-based liquid metal: Weigh 61g of pure gallium, 25g of pure indium particles, 13g of pure tin particles, and 1g of pure zinc particles. Place them together in a 50ml crucible, select the melting temperature to be 450℃, and melt for 1h. After cooling to room temperature for 2h, use a syringe to collect and obtain gallium, indium, tin, and zinc liquid metal with a nominal melting point of 7.6℃;

[0050] 3. Disconnect the chip interconnection: Take out the interconnected chip to be disconnected obtained in step 1 and place it together with the printed circuit board on a clean work platform to keep it level. Use a syringe to apply an appropriate amount of gallium, indium, tin and zinc liquid metal around the chip so that the liquid metal completely wraps the solder. Set the ultrasonic amplitude to 10μm, the ultrasonic frequency to 20kHz, the ultrasonic duration to 300s, and the ultrasonic power to 800W. Turn off the ultrasonic power after 300s and use tweezers to carefully remove the chip. Then use a clean syringe to collect most of the liquid metal first, and then use a cotton swab dipped in anhydrous ethanol to wipe the chip welding surface, gather the gallium, indium, tin and zinc liquid metal and collect it again to complete the recovery of gallium-based liquid metal. Complete the rapid desoldering of the chip soldered with silver-based solder.

[0051] It should be noted that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for desoldering a silver-based solder chip, characterized in that: The following steps are involved: S1, melting the mixed alloy to obtain a liquid alloy; S2, applying liquid alloy to the to-be-released part of the silver-based solder, so that the to-be-released part is wrapped by the liquid alloy; Ultrasonic liquid alloy for 1-100s to obtain desoldering silver-based solder; In the mixed alloy, gallium accounts for more than 50% by weight; The part to be released is an interconnection chip of a silver-based solder chip.

2. The method for desoldering a silver-based solder chip according to claim 1, characterized in that: The mixed alloy comprises, by weight, 50-90 parts of gallium, 10-50 parts of indium, 0-50 parts of tin, 0-50 parts of zinc, 0-50 parts of copper, 0-50 parts of silver, 0-50 parts of aluminum, 0-50 parts of bismuth, 0-50 parts of cobalt, 0-50 parts of titanium and 0-50 parts of iron.

3. The method for desoldering a silver-based solder chip according to claim 1, characterized in that: Silver-based solders are cleaned prior to desoldering.

4. The method for desoldering a silver-based solder chip according to claim 3, characterized in that: The cleaning steps are: use a detergent to clean the dirt, oil stains and dust on the silver-based solder, and then use hot air to dry it to ensure that the chip surface and its surroundings are dry and clean to obtain the silver-based solder to be released.

5. The method for desoldering a silver-based solder chip according to claim 1, characterized in that: The interconnection chip is a soldering connection between the silver-based solder and the printed circuit board; the components of the interconnection chip are one or more of silver, copper and zinc.

6. The method for desoldering a silver-based solder chip according to claim 1, characterized in that: The nominal melting point of the liquid alloy is 5°C to 120°C.

7. The method for desoldering a silver-based solder chip according to claim 1, characterized in that: The smelting temperature is 100°C to 2000°C.

8. The method for desoldering a silver-based solder chip according to claim 1, characterized in that: The ultrasonic amplitude is 0.1 μm to 100 μm, the ultrasonic frequency is 20 kHz to 50 kHz, and the ultrasonic power is 100 W to 10000 W.

9. The method for desoldering a silver-based solder chip according to any one of claims 1 to 8, characterized in that: The application is performed by injection with a syringe or dispensing with a dispenser.

Images