Method for manufacturing electronic part and method for regenerating electronic part

Abstract

To provide a method for manufacturing an electronic part and a method for regenerating an electronic part, in which an electronic part removed from a board mounted with lead-containing solder can brought into the scope of reuse by removing the lead.SOLUTION: A method for manufacturing an electronic part in which components other than tin contained in tin-based solder are removed comprises an immersion step in which an electronic part having tin-based solder on its surface is immersed in a molten bath containing tin to thereby remove the components other than tin contained in the tin-based solder.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing an electronic component, and a method for recycling an electronic component, and more particularly to a method for manufacturing an electronic component that can be suitably used when including a step of removing lead from tin-lead solder. [Background technology]

[0002] For example, elevators are products that are generally used for long periods, such as 20 to 30 years or more along with buildings, and there is a demand for a continuous supply of maintenance parts such as printed circuit boards. On the other hand, the period between when electronic components such as ICs mounted on printed circuit boards are released and when they are no longer in production is short. For this reason, during the maintenance period of elevators, production is maintained by repeatedly replacing electronic components. Methods for maintaining production include redesigning printed circuit boards, reusing ICs (Integrated Circuits), and securing the lifetime use of discontinued parts for long-term storage.

[0003] Patent Document 1 discloses a method for manufacturing an electronic component in which the electronic component is an electronic component that has been manufactured more than three years ago, has terminals that are soldered to a substrate, and the terminals are plated with a metal for soldering, and the terminal surfaces are regenerated by carrying out a process for removing a metal oxide film, the process including a formic acid reduction heat treatment of the metal oxide film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-131196 A Summary of the Invention [Problem to be solved by the invention]

[0005] In IC reuse, one of the means of maintaining production, circuit boards that were in use at customer sites are collected and the ICs removed from them are mounted on newly manufactured circuit boards. However, ICs removed from circuit boards mounted with SnPb (tin-lead) solder cannot be used as they are as reused products because they contain lead, and there is an issue that it is not possible to secure the number of reused ICs. The present invention aims to provide a method for manufacturing electronic components and a method for recycling electronic components, which enable electronic components that have been removed from a board mounted with solder containing lead to be reused by removing the lead. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a method for manufacturing electronic components from which components other than tin contained in tin-based solder have been removed, the method comprising an immersion step of immersing an electronic component having tin-based solder on its surface in a molten metal containing tin to remove components other than tin contained in the tin-based solder. In this case, a method for manufacturing electronic components can be provided that allows electronic components removed from a board mounted with solder containing lead to be reused by removing the lead.

[0007] Here, the component to be removed in the immersion step may be lead, in which case lead, which is a harmful component, can be removed. The tin-based solder may be a tin-lead solder, and the immersion process may be performed to remove the lead contained in the tin-lead solder. In this case, the lead contained in the tin-lead solder may be removed. Furthermore, the tin-lead solder may be coated on the electrodes of the electronic component. In this case, the lead can be removed from the tin-lead solder coated on the electrodes of the electronic component. Furthermore, the immersion step can be performed with an immersion time of 3 seconds or less and with immersion between 1 and 5 times, which makes it difficult for heat to affect the electronic components. The immersion step can be performed while applying ultrasonic vibrations, which can prevent short circuits caused by solder adhering across the electrodes. Furthermore, the dipping process can replace lead with components contained in the molten metal, thereby adjusting the composition of the tin-based solder. Furthermore, the molten metal can be a lead-free solder, which makes it easier to process by a dipping process.

[0008] The present invention also provides a method for recycling electronic components having electrodes coated with tin-based solder, the method comprising a removal step of removing the electronic components soldered with tin-based solder from a substrate, and an immersion step of removing components other than tin contained in the tin-based solder by immersing the electrodes in a molten metal containing tin. In this case, a method for recycling electronic components can be provided that can be reused by removing lead even for electronic components removed from a substrate mounted with solder containing lead. Effect of the Invention

[0009] According to the present invention, it is possible to provide a method for manufacturing electronic components and a method for recycling electronic components, which enable electronic components that have been removed from a board mounted with solder containing lead to be reused by removing the lead. [Brief description of the drawings]

[0010] [Figure 1] 1(a) to 1(c) are diagrams illustrating an outline of a method for producing an electronic component to which the present invention is applied. [Diagram 2] 1(a) and 1(b) are diagrams showing a state in which terminals of an electronic component are covered with solder. [Diagram 3] 1(a) and 1(b) are diagrams illustrating a method for immersing electrodes of an electronic component in molten lead-free solder. [Figure 4] 4(a) to 4(c) are diagrams showing the results of DSC analysis. [Diagram 5] 1(a) and 1(b) are diagrams showing the results of DSC analysis. [Figure 6] FIG. 1 shows the results of EDS analysis after two immersion treatments. [Figure 7](a) is a SEM photograph after two immersion treatments, and (b) is a Pb mapping image obtained by EDS analysis of Fig. 7(a). [Figure 8] This is a diagram mapping the elements other than Pb, namely carbon (C), silicon (Si), silver (Ag), oxygen (O), copper (Cu), and tin (Sn). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. <Outline of manufacturing method for electronic components> 1(a) to (c) are diagrams showing an outline of a method for producing an electronic component to which the present invention is applied. First, an electronic component is prepared by removing it from a board (FIG. 1(a); removal process). The electronic component is, for example, an integrated circuit such as an IC or an LSI (Large Scale Integration), but is not limited to this. The electronic component may be, for example, a capacitor, a resistor, a diode, a transistor, a transformer, a relay, a switch, a connector, etc. FIG. 1(a) illustrates an electrode E of the electronic component. The electronic component is removed from the printed circuit board to which the electronic component was soldered. In this case, the electrode (terminal) E of the electronic component is covered with the solder that was used when the electronic component was soldered to the printed circuit board.

[0012] 2(a) and 2(b) are diagrams showing a state in which terminals of an electronic component are covered with solder. FIG. 2(b) shows an IC as an electronic component. FIG. 2(a) shows that electrode E of the IC is covered with solder. In this case, the solder is tin-lead solder (SnPb solder). This means that electrode E of the electronic component is plated with a tin-lead alloy (SnPb plating). Note that the name of the tin-lead solder does not matter as long as it is a solder made of an alloy of tin and lead. For example, it may be called tin-lead solder or tin-lead eutectic solder.

[0013] Returning to Figure 1, next, an immersion process is performed in which the terminals of the electronic component are immersed in molten lead-free solder (Figure 1(b); immersion process). Figure 1(b) illustrates the state in which electrode E of the electronic component is immersed in molten lead-free solder. 3(a) and 3(b) are diagrams showing a method for immersing electrodes E of an electronic component in molten lead-free solder. In order to immerse the electrodes E of the electronic component in the molten lead-free solder, in this embodiment, a molten solder bath shown in Fig. 3(b) is used. The molten solder bath is composed of a container for storing the molten lead-free solder and a heater for keeping the molten lead-free solder in a molten state. The molten lead-free solder is kept in a molten state by applying heat from the heater. Furthermore, the electrodes E of the electronic component are immersed in the molten lead-free solder and the two are brought into contact with each other. As a result, lead is dissolved from the SnPb solder covering the electrode E of the electronic component into the molten lead-free solder, and the lead is removed. At this time, the components contained in the molten lead-free solder move toward the SnPb plating. In other words, the components contained in the molten lead-free solder replace the lead in the SnPb plating. The components of the molten lead-free solder are not particularly limited as long as they are solder that does not contain lead, but for example, it is a SnAgCu-based solder that contains tin (Sn) as the main component and silver (Ag) and copper (Cu). In this embodiment, a molten lead-free solder with a composition of Sn3Ag0.5Cu (wt%) is used. In addition, the components of the molten lead-free solder may also contain bismuth (Bi), zinc (Zn), nickel (Ni), phosphorus (P), antimony (Sb), aluminum (Al), germanium (Ge), indium (In), etc. For example, SnBi-based solder, SnZnBi-based solder, and SnCu-based solder can be mentioned.

[0014] In the dipping step, the dipping time is preferably 3 seconds or less, and the dipping is preferably performed 1 to 5 times. If the dipping time exceeds 3 seconds, the electronic components are likely to be affected by heat. If the dipping frequency exceeds 5 times, the electronic components are likely to be affected by heat. To remove lead, dipping 2 times or less is usually sufficient.

[0015] The immersion step may be performed while applying ultrasonic vibrations, which can prevent short circuits caused by the solder adhering across the electrodes E.

[0016] Returning to FIG. 1 again, next, the electronic component is removed from the molten solder bath (FIG. 1(c); removal process). After being removed, the electronic component is cooled. This completes the manufacturing process of an electronic component in which the lead has been removed from the solder that covered the electrodes E.

[0017] In the above example, the electronic component is immersed in molten lead-free solder in the immersion process, but this is not limited to this, and any molten metal containing tin may be used. In addition, the molten metal is preferably tin-based. For example, the molten metal may be 100% tin. Here, the molten metal containing tin as the main component means that tin is 50% or more of the total weight ratio of the elements. In the above example, the electronic component is coated with SnPb solder, but this is not limited to this, and any tin-based solder may be used. In the immersion process, the electronic component having tin-based solder on its surface is immersed in molten metal containing tin as the main component, thereby removing components other than tin contained in the tin-based solder. In this embodiment, however, the component to be removed in the immersion process is lead.

[0018] The above-described method can also be considered as a method for recycling electronic components. In other words, the above-described method can be considered to be a method for recycling electronic components having a tin-based solder coated on the surface of electrode E, and includes a removal process for removing the electronic component soldered with tin-based solder from the board, and an immersion process for removing components other than tin contained in the tin-based solder by immersing electrode E in a molten metal containing tin.

[0019] According to the embodiment described above, it is possible to provide a method for manufacturing electronic components that can be reused by removing the lead from electronic components that have been removed from a board mounted with solder containing lead, thereby expanding the scope of reuse and ensuring the quantity of electronic components. Another method for maintaining production is to secure a supply of discontinued parts for lifetime use, in which discontinued electronic parts are stored for a long period of time in the amount required for the maintenance period of elevators, etc., and then mounted on newly manufactured printed circuit boards. However, there is a problem that an oxide film is formed on the surface of the electrode E of the electronic parts due to long-term storage, which deteriorates the solder wettability and makes them unusable, and electronic parts are likely to run out of stock. The present invention makes it possible to realize sustainable, waste-free operation of electronic parts, such as recycling electronic parts whose solder wettability has deteriorated due to long-term storage. EXAMPLES

[0020] [Evaluation method] As an IC, a TSOP (thin SOP (Small Outline Package)) component was removed from the printed circuit board, and the SnPb solder remaining on the electrodes and covering them was subjected to the above-mentioned immersion treatment. The immersion time was 3 seconds, and immersion was performed once or twice. The following analysis and tests were then performed.

[0021] (DSC (Differential Scanning Calorimeter) analysis) Before and after the SnPb solder was immersed, DSC analysis was performed to measure the amount of Pb contained.

[0022] (EDS (Energy Dispersive X-ray Spectroscopy) Analysis) After immersion in SnPb solder, the specimens were observed using a SEM (Scanning Electron Microscope) and the elements contained therein were analyzed using EDS analysis.

[0023] (Share Test) To confirm whether the strength was maintained after immersion in SnPb solder, a shear test was conducted in accordance with JIS Z 3198-7.

[0024] [Evaluation results] 4(a) to (c) and 5(a) to (b) show the results of the DSC analysis. Figure 4(a) shows the results of DSC analysis of SnPb solder before dipping, while Figure 4(b) shows the results of DSC analysis of SnPb solder after one dipping treatment. Furthermore, Figure 4(c) is an enlarged view of a part of Figure 4(b). 4 and 5, the horizontal axis represents temperature and the vertical axis represents heat quantity.

[0025] As shown in Figure 4(a), the SnPb solder before the immersion treatment starts to melt at 179.8°C and finishes melting at 206.7°C. The peak at 182.1°C in Figure 4(a) is due to Pb. Furthermore, as shown in Figure 4(b), after the immersion process that removed the lead, a peak at 182.3°C due to Pb and a peak at 226.8°C due to the replaced Sn3Ag0.5Cu (wt%) solder were observed, and based on the ratio of the heat quantities, the remaining lead was calculated to be approximately 2%.

[0026] Figure 5(a) shows the results of DSC analysis of the SnPb solder after two dipping treatments. There was a small peak at 182.3℃ due to Pb, and the proportion was very small at 0.3%. The strength in the shear test was 16.8[N], which was an internal fracture of the solder, and the strength was sufficient.

[0027] Figure 5(b) shows the results of a DSC analysis of SnPb solder that was dipped twice and flow heated once. Other than a small peak caused by 0.05% or less Pb, no peak was observed near 183°C. In other words, there was almost no Pb content. The shear strength was 13.4 [N], which was an internal solder fracture, and the strength was sufficient.

[0028] FIG. 6 shows the results of EDS analysis after two immersion treatments. In FIG. 6, the horizontal axis represents the energy of the characteristic X-rays, and the vertical axis represents the number of counts. As shown in the figure, the Pb peak is small, indicating that Pb has been sufficiently removed.

[0029] Figure 7(a) is an SEM photograph after two immersion treatments. Figure 7(b) is a mapping of Pb by EDS analysis of Figure 7(a). Pb is not localized, but is dispersed throughout the metal. FIG. 8 is a mapping diagram for elements other than Pb, including carbon (C), silicon (Si), silver (Ag), oxygen (O), copper (Cu), and tin (Sn). Silicon (Si) exists in a localized state, but the other elements are not localized and exist dispersed throughout the electrode.

[0030] Although the present embodiment has been described above, the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear from the claims that various modifications and improvements to the above embodiment are also included in the technical scope of the present invention. [Explanation of symbols]

[0031] E…Electrode

Claims

1. A method for manufacturing electronic components in which components other than tin contained in tin-based solder are removed, comprising the steps of: A method for manufacturing an electronic component, comprising an immersion step of immersing an electronic component having a tin-based solder on its surface in a molten metal containing tin to remove components other than tin contained in the tin-based solder.

2. The method for manufacturing an electronic component according to claim 1 , wherein the component removed in the immersion step is lead.

3. 3. The method for manufacturing an electronic component according to claim 2, wherein the tin-based solder is a tin-lead solder, and the immersion step removes lead contained in the tin-lead solder.

4. 4. The method for manufacturing an electronic component according to claim 3, wherein the tin-lead solder is applied to an electrode of the electronic component.

5. 2. The method for producing an electronic component according to claim 1, wherein the immersion step includes immersion for a period of 3 seconds or less, and immersion is performed once or more and five or less times.

6. The method for producing an electronic component according to claim 1 , wherein the immersion step is carried out while applying ultrasonic vibration.

7. The method for producing an electronic component according to claim 1 , wherein the immersion step replaces the lead with a component contained in the molten metal.

8. The method for manufacturing an electronic component according to claim 1 , wherein the molten metal is a lead-free solder.

9. A method for recycling electronic components having electrodes coated with tin-based solder, comprising the steps of: A removal process of removing electronic components soldered with tin-based solder from a substrate; The method for recycling electronic components includes an immersion step of immersing the electrode in a molten metal containing tin to remove components other than tin contained in the tin-based solder.

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