Method for tin dissolving and unsoldering of waste circuit board

Abstract

The invention belongs to the technical field of electronic waste recycling, and particularly discloses a method for tin dissolving and desoldering of a waste circuit board, which comprises the following steps of: carrying out dust removal treatment on the waste circuit board by adopting a high-pressure blower gun; preparing a hydrochloric acid solution for desoldering; putting the waste circuit board into a closed glass reaction kettle, and injecting a hydrochloric acid solution into the closed glass reaction kettle; dissolving and soaking the waste circuit board, and mechanically stirring in the whole process; and respectively taking out the component and the substrate, washing with clear water, drying, and collecting the de-soldering tail liquid. The desoldering tail liquid is subpackaged, and centrifugal separation is carried out after subpackaging; and upper-layer waste liquid is poured out of the separated sealing-off tail liquid, neutralization treatment is conducted, lower-layer solid matter is recycled, and the welding flux is obtained. By the adoption of the tin dissolving and desoldering method for the waste circuit board, rapid separation of ECs and a substrate (PWB) can be achieved, tin-lead solder on the waste circuit board can be removed in an environment-friendly and efficient mode, and convenience is provided for further resource utilization.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic waste recycling, and in particular relates to a method for dissolving tin and desoldering waste circuit boards. Background Art

[0002] As an important pre-processing link for the resource utilization of waste printed circuit boards (WPCBs), the desoldering and separation of components (ECs) and substrates (PWBs) has received widespread attention in the industry. At present, the research and application of mechanical grinding desoldering and thermal desoldering are the most common. Mechanical grinding can efficiently peel off the solder feet to achieve the recycling of components (ECs), but it has high requirements for cutting and grinding equipment, and there is still a risk of pollution from heat generation during the grinding process; thermal desoldering technology can be roughly divided into hot air, mineral oil, paraffin, fine sand, infrared, laser, molten tin and other typical methods according to different heating media. This type of desoldering technology is relatively mature, especially the use of molten tin furnaces. However, due to the problems of heat loss and harmful substance emissions, the actual operation of the molten tin desoldering process in production is restricted to a certain extent. Therefore, it is particularly important to seek more efficient, clean and feasible desoldering methods.

[0003] Therefore, there is a need in the art to develop a method for dissolving tin and desoldering waste circuit boards that can effectively solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for dissolving tin and desoldering waste circuit boards, which can realize the rapid separation of components (ECs) and substrates (PWBs), and the environmentally friendly and efficient removal of tin-lead solder on waste circuit boards, providing convenience for further resource utilization.

[0005] To achieve the above object, the present invention provides a method for dissolving tin and desoldering waste circuit boards, comprising the following steps: Step S1, using a high-pressure air gun to remove dust from the waste circuit boards; Step S2, preparing a hydrochloric acid solution for desoldering; Step S3, placing the waste circuit boards treated in step S1 into a sealed glass reactor, and injecting the hydrochloric acid solution prepared in step S2 into the sealed glass reactor; Step S4, dissolving and soaking the waste circuit boards to allow them to undergo a dissolution reaction, with mechanical stirring being performed throughout the process; Step S5: After the dissolution reaction is completed, the sealed glass reactor is opened, the components and substrate are taken out respectively, and they are rinsed with clean water and then dried, and the desoldering tail liquid is collected; Step S6, packaging the desoldering tail liquid, and centrifugally separating the desoldering tail liquid after packaging; Step S7, pour out the upper waste liquid of the separated desoldering tail liquid and neutralize it, and recover the lower solid matter to obtain the solder.

[0006] Preferably, in step S2, the concentration of the hydrochloric acid solution for desoldering is 30 - 150 g / L.

[0007] Preferably, in step S3, when injecting the hydrochloric acid solution prepared in step S2 into the sealed glass reaction kettle, the mass ratio of the hydrochloric acid solution to the waste circuit board is 4:1 - 7:1.

[0008] Preferably, in step S3, add NaCl particles into the sealed glass reaction kettle, and cooperate with mechanical stirring in step S4 to fully dissolve the NaCl particles.

[0009] Preferably, after the NaCl particles are fully dissolved, the concentration of NaCl in the chloride salt solvent in the sealed glass reaction kettle is 200 - 500 g / L.

[0010] Preferably, in step S4, the dissolution and soaking time is 50 - 140 min, the temperature of the dissolution and soaking solution is 30 - 90 °C, and the rotation speed of the mechanical stirring is 200 - 600 rpm.

[0011] Preferably, in step S6, the centrifugation time is 10 - 20 min, and the rotation speed of the centrifugation is 3000 - 5000 rpm.

[0012] The present invention adopts the above - mentioned method for dissolving tin and desoldering waste circuit boards, and the beneficial effects are as follows: (1) The method for dissolving tin and desoldering waste circuit boards proposed by the present invention, that is, using a solvent to soak the waste circuit board, through scientifically formulating the solvent formula and dissolution reaction conditions, enables the solder to be efficiently dissolved under mild conditions, thereby realizing the complete separation of components (ECs) from the substrate (PWB), and at the same time obtaining good solder recovery and tail - liquid treatment effects; (2) By scientifically formulating the solvent and regulating the dissolution reaction conditions in the present invention, the solder dissolution rate can reach 99%, thereby realizing the complete separation of components (ECs) from the substrate (PWB); it can effectively avoid the risks of thermal desoldering process in terms of energy consumption and pollution; in addition, tin - lead solder can be efficiently recovered from the desoldering tail liquid for recycling, and the remaining waste liquid can be rendered harmless after neutralization; (3) The present invention has the advantages of simple operation, low cost, environmental friendliness, and good desoldering effect, etc., which can provide convenience for further resource utilization.

[0013] Next, through the drawings and examples, the technical solutions of the present invention will be further described in detail. Brief Description of the Drawings

[0014] Figure 1 It is a schematic flow chart of an embodiment of the method for dissolving tin and desoldering waste circuit boards of the present invention; Figure 2This is a comparison diagram of the desoldering effect of a method for desoldering tin from waste printed circuit boards in the present invention; among them, a) is a diagram of the waste printed circuit board raw material; b) is a diagram of the desoldering effect of the acid solution immersion in the comparative example; c) is a diagram of the desoldering effect of the trichloride salt solution immersion in the example. Detailed implementation mode

[0015] The technical solution of the present invention will be further described below with reference to the accompanying drawings and examples.

[0016] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those of ordinary skill in the field to which the present invention belongs.

[0017] As Figure 1 shown, a method for desoldering tin from waste printed circuit boards includes the following steps: Step S1: Dust the waste printed circuit board with a high-pressure air gun, as Figure 2 shown in a)

[0018] Step S2: Prepare a hydrochloric acid solution for desoldering.

[0019] Step S3: Put the waste printed circuit board processed in Step S1 into a sealed glass reaction kettle, and inject the hydrochloric acid solution prepared in Step S2 into the sealed glass reaction kettle.

[0020] Step S4: Dissolve and soak the waste printed circuit board to make it undergo a dissolution reaction, and perform mechanical stirring throughout the process.

[0021] Step S5: After the dissolution reaction is completed, open the sealed glass reaction kettle, take out the components and the substrate respectively, rinse them with clean water and dry them, and collect the desoldering tail liquid.

[0022] Step S6: Subpackage the desoldering tail liquid, and perform centrifugal separation after subpackaging.

[0023] Step S7: Pour out the upper-layer waste liquid from the separated desoldering tail liquid and perform neutralization treatment, and recycle the lower-layer solid substance to obtain the solder.

[0024] Example 1 A method for desoldering tin from waste printed circuit boards includes the following steps: Step S1: Dust the waste printed circuit board with a high-pressure air gun.

[0025] Step S2: Prepare a hydrochloric acid solution for desoldering, and the concentration of the prepared hydrochloric acid solution for desoldering is 110 g / L.

[0026] Step S3: Put the waste printed circuit board processed in Step S1 into a sealed glass reaction kettle, and inject the hydrochloric acid solution prepared in Step S2 into the sealed glass reaction kettle, and the mass ratio of the hydrochloric acid solution to the waste printed circuit board is 4:1.

[0027] Add NaCl particles into a sealed glass reactor. After the NaCl particles are fully dissolved, the concentration of NaCl in the chloride salt solvent in the sealed glass reactor is 400 g / L.

[0028] Step S4: Dissolve and soak the waste circuit board to carry out a dissolution reaction, and perform mechanical stirring throughout the process.

[0029] The dissolution and soaking time is 80 min, the temperature of the dissolution and soaking solution is 90 °C, and the rotation speed of the mechanical stirring is 400 rpm.

[0030] Step S5: After the dissolution reaction is completed, open the sealed glass reactor, take out the components and the substrate respectively, rinse them with clean water and then dry them, and collect the desoldering tail liquid.

[0031] Step S6: Subpackage the desoldering tail liquid, and perform centrifugal separation after subpackaging. The centrifugal separation time is 15 min, and the rotation speed of the centrifugal separation is 4000 rpm.

[0032] Step S7: Pour out the upper-layer waste liquid from the separated desoldering tail liquid and perform neutralization treatment, and recycle the lower-layer solid substance to obtain the solder.

[0033] The dissolution rate of the solder obtained in this example is 81%.

[0034] Example Two A method for dissolving tin and desoldering waste circuit boards includes the following steps: Step S1: Use a high-pressure air gun to remove dust from the waste circuit board.

[0035] Step S2: Prepare a hydrochloric acid solution for desoldering, and the concentration of the prepared hydrochloric acid solution for desoldering is 70 g / L.

[0036] Step S3: Put the waste circuit board treated in Step S1 into a sealed glass reactor, and inject the hydrochloric acid solution prepared in Step S2 into the sealed glass reactor. The mass ratio of the hydrochloric acid solution to the waste circuit board is 5:1.

[0037] Add NaCl particles into the sealed glass reactor. After the NaCl particles are fully dissolved, the concentration of NaCl in the chloride salt solvent in the sealed glass reactor is 200 g / L.

[0038] Step S4: Dissolve and soak the waste circuit board to carry out a dissolution reaction, and perform mechanical stirring throughout the process.

[0039] The dissolution and soaking time is 110 min, the temperature of the dissolution and soaking solution is 90 °C, and the rotation speed of the mechanical stirring is 400 rpm.

[0040] Step S5: After the dissolution reaction is completed, open the sealed glass reactor, take out the components and the substrate respectively, rinse them with clean water and then dry them, and collect the desoldering tail liquid.

[0041] Step S6: Subpackage the desoldering tail liquid, and perform centrifugal separation after subpackaging. The time for centrifugal separation is 15 min, and the rotation speed for centrifugal separation is 4000 rpm.

[0042] Step S7: Pour out the upper-layer waste liquid from the separated desoldering tail liquid and perform neutralization treatment, and recycle the lower-layer solid substance to obtain the solder.

[0043] The dissolution rate of the solder obtained in this embodiment is 85%.

[0044] Embodiment Three A method for dissolving tin and desoldering waste circuit boards includes the following steps: Step S1: Use a high-pressure air gun to remove dust from the waste circuit board.

[0045] Step S2: Prepare a hydrochloric acid solution for desoldering, and the concentration of the hydrochloric acid solution for desoldering is 150 g / L.

[0046] Step S3: Put the waste circuit board treated in Step S1 into a sealed glass reaction kettle, and inject the hydrochloric acid solution prepared in Step S2 into the sealed glass reaction kettle. The mass ratio of the hydrochloric acid solution to the waste circuit board is 4:1.

[0047] Add NaCl particles to the sealed glass reaction kettle. After the NaCl particles are fully dissolved, the concentration of NaCl in the chloride salt solvent in the sealed glass reaction kettle is 200 g / L.

[0048] Step S4: Dissolve and soak the waste circuit board to make it undergo a dissolution reaction, and perform mechanical stirring throughout the process.

[0049] The dissolution and soaking time is 140 min, the temperature of the dissolution and soaking solution is 90 °C, and the rotation speed of the mechanical stirring is 400 rpm.

[0050] Step S5: After the dissolution reaction is completed, open the sealed glass reaction kettle, take out the components and the substrate respectively, rinse them with clean water and then dry them, and collect the desoldering tail liquid. The desoldering effect is as Figure 2 shown in c).

[0051] Step S6: Subpackage the desoldering tail liquid, and perform centrifugal separation after subpackaging. The time for centrifugal separation is 15 min, and the rotation speed for centrifugal separation is 4000 rpm.

[0052] Step S7: Pour out the upper-layer waste liquid from the separated desoldering tail liquid and perform neutralization treatment, and recycle the lower-layer solid substance to obtain the solder.

[0053] Comparative Example One A method for dissolving tin and desoldering waste circuit boards includes the following steps: Step S1: Use a high-pressure air gun to remove dust from the waste circuit board.

[0054] Step S2: Prepare a hydrochloric acid solution for desoldering, and the concentration of the prepared hydrochloric acid solution for desoldering is 150 g / L.

[0055] Step S3: Put the waste circuit board processed in Step S1 into a sealed glass reaction kettle, and inject the hydrochloric acid solution prepared in Step S2 into the sealed glass reaction kettle. The mass ratio of the hydrochloric acid solution to the waste circuit board is 7:1.

[0056] Step S4: Dissolve and soak the waste circuit board to make it undergo a dissolution reaction, and perform mechanical stirring throughout the process.

[0057] The dissolution and soaking time is 80 min, the temperature of the dissolution and soaking solution is 70 °C, and the rotation speed of the mechanical stirring is 400 rpm.

[0058] Step S5: After the dissolution reaction is completed, open the sealed glass reaction kettle, take out the components and the substrate respectively, rinse them with clean water and then dry them, and collect the desoldering tail liquid.

[0059] Step S6: Subpackage the desoldering tail liquid, and perform centrifugal separation after subpackaging. The centrifugal separation time is 15 min, and the rotation speed of the centrifugal separation is 4000 rpm.

[0060] Step S7: Pour out the upper-layer waste liquid from the separated desoldering tail liquid and perform neutralization treatment, and recycle the lower-layer solid substance to obtain the solder.

[0061] Comparative Example 2 A method for dissolving tin and desoldering waste circuit boards includes the following steps: Step S1: Use a high-pressure air gun to remove dust from the waste circuit board.

[0062] Step S2: Prepare a hydrochloric acid solution for desoldering, and the concentration of the prepared hydrochloric acid solution for desoldering is 110 g / L.

[0063] Step S3: Put the waste circuit board processed in Step S1 into a sealed glass reaction kettle, and inject the hydrochloric acid solution prepared in Step S2 into the sealed glass reaction kettle. The mass ratio of the hydrochloric acid solution to the waste circuit board is 4:1.

[0064] Step S4: Dissolve and soak the waste circuit board to make it undergo a dissolution reaction, and perform mechanical stirring throughout the process.

[0065] The dissolution and soaking time is 80 min, the temperature of the dissolution and soaking solution is 90 °C, and the rotation speed of the mechanical stirring is 400 rpm.

[0066] After the dissolution reaction is completed, open the sealed glass reaction kettle, take out the components and the substrate respectively, rinse them with clean water and then dry them, and collect the desoldering tail liquid. The desoldering effect is asFigure 2 as shown in b) of

[0067] Step S6: Subpackage the desoldering tail liquid, and perform centrifugal separation after subpackaging. The time for centrifugal separation is 15 min, and the rotational speed for centrifugal separation is 4000 rpm.

[0068] Step S7: Pour out the upper-layer waste liquid from the separated desoldering tail liquid and perform neutralization treatment, and recover the lower-layer solid substance to obtain the solder.

[0069] Calculate the dissolution rates of Example 1, Example 2, Example 3, Comparative Example 1, and Comparative Example 2 respectively, and the obtained dissolution rates are shown in Table 1.

[0070] Table 1 Dissolution Rate ;

[0071] As can be seen from Table 1 above, the dissolution rates of Example 1, Example 2, and Example 3 are all higher than those of Comparative Example 1 and Comparative Example 2, and the dissolution rate of the solder obtained in Example 3 is as high as 99%.

[0072] Therefore, by adopting the above method for dissolving tin and desoldering waste circuit boards, the tin-lead solder on the waste circuit boards can be efficiently dissolved, the rapid separation of components (ECs) and substrates (PWBs) can be realized, and it provides convenience for further resource utilization.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for dissolving tin and desoldering waste circuit boards, characterized in that: The following steps are involved: Step S1, using a high-pressure air gun to remove dust from the waste circuit boards; Step S2, preparing a hydrochloric acid solution for desoldering; Step S3, placing the waste circuit boards treated in step S1 into a sealed glass reactor, and injecting the hydrochloric acid solution prepared in step S2 into the sealed glass reactor; Step S4, dissolving and soaking the waste circuit boards to allow them to undergo a dissolution reaction, with mechanical stirring being performed throughout the process; Step S5: After the dissolution reaction is completed, the sealed glass reactor is opened, the components and substrate are taken out respectively, and they are rinsed with clean water and then dried, and the desoldering tail liquid is collected; Step S6, packaging the desoldering tail liquid, and centrifugally separating the desoldering tail liquid after packaging; Step S7, pour out the upper waste liquid of the separated desoldering tail liquid and neutralize it, and recover the lower solid matter to obtain the solder.

2. The method for desoldering waste circuit boards according to claim 1, characterized in that: In step S2, the concentration of the desoldering hydrochloric acid solution is prepared to be 30-150 g / L.

3. The method for dissolving tin and desoldering waste circuit boards according to claim 1, characterized in that: In step S3, when the hydrochloric acid solution prepared in step S2 is injected into the sealed glass reactor, the mass ratio of the hydrochloric acid solution to the waste circuit boards is 4:1-7:

1.

4. The method for dissolving tin and desoldering waste circuit boards according to claim 3, characterized in that: In step S3, NaCl particles are added into the sealed glass reactor, and mechanical stirring is performed in step S4 to fully dissolve the NaCl particles.

5. The method for dissolving tin and desoldering waste circuit boards according to claim 4, characterized in that: After the NaCl particles are fully dissolved, the concentration of NaCl in the chloride salt solvent in the closed glass reactor is 200-500 g / L.

6. The method for desoldering waste circuit boards according to claim 1, characterized in that: In step S4, the dissolving and soaking time is 50-140 min, the temperature of the dissolving and soaking solution is 30-90° C., and the speed of the mechanical stirring is 200-600 rpm.

7. The method for desoldering waste circuit boards according to claim 1, characterized in that: In step S6, the time of centrifugal separation is 10-20 minutes, and the speed of centrifugal separation is 3000-5000 rpm.

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