Method for reducing electrodes of electronic components

Abstract

This invention provides a method for reducing the electrodes of electronic components in a way that can suppress a decrease in reliability. [Solution] The electronic component is placed in a processing chamber and heated to a predetermined temperature within the chamber. Then, the pressure inside the processing chamber is reduced, and formic acid is supplied to the chamber to reduce the electrode surface of the electronic component in a formic acid atmosphere for a certain period of time. Furthermore, the pressure inside the processing chamber is released, and the heating of the electronic component is stopped.

Description

[Technical Field]

[0001] This invention relates to a method for reducing electrodes of electronic components. [Background technology]

[0002] Because elevators operate alongside buildings for nearly several decades, they undergo regular repairs and maintenance. During these repairs, the control boards for the elevators are updated, and the electronic components mounted on them are replaced. Due to the long-term nature of elevator maintenance, electronic components are stockpiled for extended periods to mitigate the risk of them being discontinued and unavailable as replacements in the future. However, electronic components stored for long periods face the problem of "solder repellency," where the electrode terminals fail to be properly wetted with solder. Therefore, a method has been proposed to regenerate the electrode terminals of long-stored electronic components through formic acid reduction treatment (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-131196 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, the method described in Patent Document 1 involves formic acid reduction treatment at 220-280°C for 2 to 10 minutes. Under these conditions, the high temperature state persists for several minutes, placing a heavy burden on older electronic components. As a result, the reliability of the electronic components subjected to formic acid reduction treatment decreases.

[0005] To solve the above-mentioned problems, the present invention provides a method for reducing the electrodes of electronic components that can suppress a decrease in reliability.

[0006] Furthermore, the above-mentioned and other objectives of the present invention, as well as the novel features of the present invention, will be made clearer by the description herein and the accompanying drawings. [Means for solving the problem]

[0007] The present invention provides a method for reducing the electrodes of an electronic component, which involves placing the electronic component in a processing chamber and heating it to a predetermined temperature within the chamber. Then, the pressure inside the processing chamber is reduced, and formic acid is supplied to the chamber to reduce the electrode surface of the electronic component in a formic acid atmosphere for a certain period of time. Finally, the pressure inside the processing chamber is released, and the heating of the electronic component is stopped. [Effects of the Invention]

[0008] According to the present invention, a method for reducing the electrodes of electronic components that can suppress a decrease in reliability can be provided.

[0009] Furthermore, issues, configurations, and effects other than those mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0010] [Figure 1] This is a conceptual diagram of a method for reducing electrode terminals of electronic components using the formic acid reduction treatment of the present invention. [Figure 2] This is a two-axis graph showing the relationship between temperature, pressure, and time inside a formic acid reflow apparatus during a method for reducing electrodes of electronic components using formic acid reduction treatment. [Figure 3] This is a two-axis graph showing the relationship between temperature, pressure, and time inside a formic acid reflow apparatus during a method for reducing electrodes of electronic components using formic acid reduction treatment. [Figure 4] This diagram shows the heating element and electronic components in the processing chamber of a formic acid reflow apparatus. [Figure 5] This diagram shows the heating element and electronic components in the processing chamber of a formic acid reflow apparatus. [Figure 6] This figure shows the temperature change of electronic components in the processing chamber of a formic acid reflow apparatus. [Figure 7] This is a two-axis graph showing the relationship between temperature, pressure, and time inside a formic acid reflow apparatus during a method for reducing electrodes of electronic components using formic acid reduction treatment. [Figure 8] It is a diagram showing an example of a conventional method for reducing electrode terminals of electronic components using formic acid reduction treatment. [Figure 9] It is a diagram showing an example of the temperature of an electronic component in a conventional method for reducing electrode terminals of electronic components using formic acid reduction treatment. MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, example embodiments for carrying out the present invention will be described, but the present invention is not limited to the following examples. Note that the description will be given in the following order. 1. Summary of the present invention 2. First embodiment of a method for reducing an electrode of an electronic component 3. Second embodiment of a method for reducing an electrode of an electronic component

[0012] <1. Summary of the present invention> Prior to describing the embodiments of the present invention, an outline of the present invention will be described. First, the mechanism of formic acid reduction heat treatment will be described. It is known that the formic acid reduction heat treatment process proceeds through the following steps: (1) adsorption of formic acid onto a metal surface, (2) dissociation of oxygen atoms from a metal oxide, and (3) abstraction of oxygen atoms and desorption of CO2 and H2O.

[0013] When focusing on Sn in a low temperature range of 150°C to 200°C, which is around the melting point of SnPb (183°C), Sn+2HCOOH→Sn(COOH)2+H2···(1) SnO+2HCOOH→Sn(COOH)2+H2O···(2) re-oxidation of the metal and re-oxidation with MeO, which is the result of reduction of SnO2, are suppressed. When the temperature exceeds 220°C, the organometal (Me(COOH)2) Sn(COOH)2→Sn+2CO2+H2···(3) decomposes into metal, carbon dioxide and hydrogen.

[0014] As described above, formic acid reduction heat treatment involves two types of reactions: one at a low temperature of approximately 150°C to 200°C and another at a high temperature of 220°C or higher. Therefore, conventional methods for reducing the electrode terminals of electronic components using formic acid require the electronic components to be kept at a high temperature of 220°C or higher.

[0015] For example, Figure 8 shows an example of a conventional method for reducing the electrode terminals of electronic components using formic acid reduction. In Figure 8, the vertical axis is temperature [°C] and the horizontal axis is time [minutes (min)]. As shown in Figure 8, the processing chamber containing the electronic components is heated from room temperature (20°C) to a set temperature of 280°C under reduced pressure. Furthermore, the temperature of 280°C is maintained for approximately 5 minutes. The formic acid reduction treatment of electronic components involves placing the electronic components in a treatment chamber and heating them under reduced pressure. A mixed atmosphere of acid and nitrogen gas is then supplied to the treatment chamber. This reduces the electrode terminals of the electronic components according to the mechanism of formic acid reduction heat treatment described above. In the example shown in Figure 8, the temperature in the treatment chamber is set to 280°C to perform the reaction in the high-temperature range of 220°C or higher formic acid reduction heat treatment.

[0016] Figure 9 shows the temperature of the electronic components at this time. In Figure 9, the vertical axis is temperature [°C] and the horizontal axis is time [minutes (min)]. In Figure 9, the temperature inside the processing chamber is shown by solid line 51, the temperature at the tip of the electrode terminal of the electronic component is shown by solid line 52, and the temperature at the base of the electrode terminal of the electronic component is shown by solid line 53. As shown in Figure 9, if the temperature in the processing chamber is maintained at 280°C, the tip of the electrode terminal of the electronic component will reach 240°C, and the base of the electrode terminal will reach 220°C. This temperature will persist for several minutes. If such high temperatures are maintained, it may cause thermal damage to the electronic component.

[0017] Electronic components should ideally be operated within the junction temperature (Tj) range of the semiconductor elements they contain. The junction temperature is the temperature of the PN junction of the semiconductor element and is the operating temperature that guarantees the performance and lifespan of the semiconductor element during operation. The maximum temperature at which the PN junction of the semiconductor element can operate is called the maximum junction temperature (Tjmax). If the semiconductor element exceeds the maximum junction temperature, it may cease to function properly. Generally, the maximum junction temperature is set to a different value for each electronic component product, but for semiconductor elements using Si, it is set to around 150°C to 175°C. In some cases, the maximum junction temperature may be set to around 100°C to 110°C depending on the electronic component.

[0018] Therefore, conventional methods for reducing the electrode terminals of electronic components using formic acid reduction tend to generate thermal stress on the electronic components that exceeds the maximum junction temperature. As a result, conventional formic acid reduction methods are prone to causing malfunctions and damage to semiconductor devices, leading to a decrease in the reliability of electronic components.

[0019] Therefore, the present invention proposes a method for reducing the electrode terminals of electronic components using formic acid reduction treatment, which can reduce the thermal load on the electronic components. Figure 1 shows a conceptual diagram of the method for reducing the electrode terminals of electronic components using formic acid reduction treatment according to the present invention. In Figure 1, the vertical axis represents the internal temperature of the electronic component [°C], and the horizontal axis represents the processing time [seconds (sec)]. As shown by the solid line 3 in Figure 1, the internal temperature of the electronic component rises as the processing time increases. Therefore, in this invention, as shown in distribution 1, the formic acid reduction treatment is performed under conditions where the processing time is short and the internal temperature of the electronic component does not rise. By shortening the processing time, this method terminates the formic acid reduction treatment before the heat in the processing chamber reaches the semiconductor elements inside the electronic component and exceeds the maximum junction temperature. This reduces the thermal load on the semiconductor elements of the electronic component and ensures the reliability of the electronic component. Furthermore, in this invention, as shown in Distribution 2, the formic acid reduction treatment is performed using conditions that prevent the internal temperature of the electronic component from rising, even under conditions that increase the processing time. This method, even when the processing time is extended, employs a technique that makes it difficult for heat in the processing chamber to reach the semiconductor elements inside the electronic component, thereby terminating the formic acid reduction treatment before exceeding the maximum junction temperature. This reduces the thermal load on the semiconductor elements of the electronic component and ensures the reliability of the electronic component.

[0020] <2. First Embodiment of a Method for Reducing Electrodes of Electronic Components> Hereinafter, an example of a method for reducing the electrodes of an electronic component according to an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following example. In the figures described below, common components are denoted by the same reference numerals. Furthermore, in the drawings used herein, identical or corresponding components are denoted by the same reference numerals, and repeated descriptions of these components may be omitted.

[0021] [Method for reducing electrodes in electronic components] The following describes the method for reducing the electrodes of an electronic component according to the first embodiment. In the method for reducing the electrodes of electronic components according to this embodiment, a formic acid reflow apparatus capable of formic acid reduction treatment is used. First, the electronic components to be subjected to formic acid reduction treatment are placed in the treatment chamber of the formic acid reflow apparatus. Then, the treatment chamber is replaced with an inert gas such as nitrogen.

[0022] Next, the treatment chamber is heated to a predetermined temperature under an inert gas atmosphere. Furthermore, after the treatment chamber reaches the predetermined temperature, the temperature is maintained for a certain period of time. By maintaining the temperature at the predetermined temperature for a certain period of time, the electrode terminals of the electronic component are reliably heated to the temperature at which the formic acid reduction treatment takes place. At this time, it is preferable to attach a temperature sensor such as a thermocouple to the electronic component. It is preferable to confirm whether the electrode terminals of the electronic component have reached the temperature at which the formic acid reduction treatment takes place using the temperature sensor.

[0023] The predetermined temperature inside the processing chamber is preferably 150°C to 220°C. In particular, it is preferably 160°C to 190°C. The formic acid reduction treatment is started at 150°C or higher. For this reason, the predetermined temperature inside the processing chamber is preferably 150°C or higher, and preferably 160°C or higher to ensure that the formic acid reduction treatment is started reliably. Furthermore, in order to reduce thermal damage to electronic components, it is preferable that the heating temperature be as low as possible. Moreover, it is preferable that the temperature be lower than the melting point of the metal coating the surface of the electrode terminals of the electronic components. Common metals used to coat the surface of the electrode terminals of electronic components include SnPb eutectic solder plating and tin plating. Specifically, since the melting point of SnPb eutectic solder is 183°C, it is preferable that the temperature inside the processing chamber be 190°C or lower. Also, since the melting point of tin is around 217°C, it is preferable that the temperature inside the processing chamber be 220°C or lower.

[0024] Furthermore, it is preferable that the set temperature inside the processing chamber is such that the temperature of the electronic component is below a predetermined temperature that serves as a degradation criterion for the semiconductor elements embedded in the electronic component. As described above, the electronic component housed in the processing chamber is heated by heating the inside of the processing chamber. At this time, if the semiconductor elements embedded in the electronic component exceed the predetermined temperature that serves as a degradation criterion, the reliability of the electronic component is likely to decrease. For example, if the semiconductor elements mounted on the electronic component exceed the junction temperature (Tj) of the PN junction due to heating, the reliability of the electronic component is likely to decrease. Therefore, for example, it is preferable to obtain in advance the relationship between the temperature in the processing chamber, the heating time, and the internal temperature of the electronic component, and to set the heating temperature in the processing chamber to the heating time under the condition that the internal temperature of the electronic component does not exceed the junction temperature. In other words, it is preferable that the set temperature inside the processing chamber be set based on the junction temperature of the PN junction of the semiconductor element embedded in the electronic component. Furthermore, it is preferable that the set temperature inside the processing chamber be set to a temperature that is below the maximum junction temperature (Tjmax) of the semiconductor element embedded in the electronic component.

[0025] Next, after heating the electronic components to the treatment temperature, the pressure inside the treatment chamber, which is under an inert gas atmosphere, is reduced. Typically, heating inside the treatment chamber is performed under atmospheric pressure (1 atm = 1.013 × 10⁻¹⁰). 5 The process starts at approximately Pa. Therefore, the pressure inside this processing chamber is reduced from atmospheric pressure to a predetermined pressure. Then, with the pressure inside the processing chamber reduced, formic acid is supplied into the processing chamber.

[0026] To perform the formic acid reduction treatment in a short time, a higher formic acid concentration in the treatment chamber is preferable. The higher the formic acid concentration in the treatment chamber, the shorter the time it takes for the formic acid reduction treatment at the electrode terminals of electronic components to be completed. Therefore, by increasing the formic acid concentration and completing the formic acid reduction treatment in a short time, thermal damage to electronic components can be reduced. In other words, in the processing chamber where the electronic components are housed, it is preferable to set the formic acid concentration of the formic acid vapor atmosphere so that the internal temperature of the electronic components does not exceed a predetermined temperature that serves as a degradation criterion during the time until the reduction heat treatment is completed.

[0027] The formic acid concentration in the processing chamber depends on the concentration of formic acid supplied and the pressure inside the processing chamber. To increase the formic acid concentration inside the processing chamber, it is preferable to increase the concentration of the supplied formic acid. Furthermore, a lower pressure inside the processing chamber when supplying formic acid can increase the formic acid concentration inside the processing chamber. To increase the formic acid concentration in the processing chamber, it is preferable to supply the formic acid to the chamber without mixing it with an inert gas such as nitrogen. For example, special grade formic acid reagents have a purity of 98% or higher. By supplying highly pure formic acid to the processing chamber without mixing it with an inert gas, the formic acid concentration in the processing chamber can be increased.

[0028] Furthermore, the processing chamber is filled with an inert gas before the formic acid is supplied. The presence of an inert gas in the processing chamber reduces the formic acid concentration. Therefore, by reducing the amount of inert gas in the processing chamber before supplying formic acid, the formic acid concentration in the processing chamber can be increased. For example, by reducing the pressure in the processing chamber to 100 Pa or less and supplying high-purity formic acid, the formic acid concentration in the processing chamber can be increased to 98% or higher. In this way, by increasing the formic acid concentration in the processing chamber, the formic acid reduction treatment can be completed in a short time, and thermal damage to electronic components can be reduced.

[0029] Furthermore, the formic acid concentration in the processing chamber can be confirmed by monitoring the pressure inside the chamber. The pressure inside the processing chamber increases with the supply of formic acid. In particular, the greater the amount of formic acid supplied, the greater the pressure inside the processing chamber. Therefore, the formic acid concentration inside the processing chamber can be confirmed not only by observing the concentration (purity) of the formic acid supplied to the processing chamber, but also by observing the amount of pressure reduction inside the processing chamber and the pressure inside the processing chamber due to the supply of formic acid. For example, the formic acid concentration inside the processing chamber is preferably 50% or higher, and preferably 70% or higher. Moreover, in order to reduce thermal damage to electronic components, a higher formic acid concentration is preferable, so the formic acid concentration inside the processing chamber is preferably 98% or higher.

[0030] Next, formic acid is supplied into the processing chamber, and after the pressure inside the processing chamber reaches a predetermined pressure, that state is maintained for a certain period of time. After the supply of formic acid, the temperature and pressure are maintained for a certain period of time to perform formic acid reduction treatment on the electrode terminals of electronic components in a formic acid atmosphere. The time for which the temperature and pressure are maintained at a constant level is defined as the processing time for the formic acid reduction treatment. When considering thermal damage to electronic components, a shorter processing time for formic acid reduction is preferable. Assuming a sufficient supply of formic acid to the processing chamber, and given that the processing chamber has a high concentration of formic acid, the formic acid reduction process can be completed in a few seconds to tens of seconds. Therefore, it is preferable that the formic acid reduction process takes less than 120 seconds, and especially less than 100 seconds. This processing time allows for formic acid reduction using a high concentration of formic acid, while also reducing thermal damage to electronic components compared to conventional methods for formic acid reduction of electrode terminals of electronic components. Furthermore, if the formic acid concentration in the processing chamber is increased to 98% or higher, the formic acid reduction treatment of the electrode terminals of electronic components can be completed in a few seconds. For this reason, the processing time for formic acid reduction treatment is preferably 1 to 10 seconds. This processing time further reduces thermal damage to electronic components.

[0031] Next, the reduced pressure in the processing chamber is released, and an inert gas is supplied to the chamber, returning the pressure inside the processing chamber to atmospheric pressure. By supplying an inert gas to the processing chamber, the concentration of formic acid in the chamber is reduced. Due to the decrease in formic acid concentration, the formic acid reduction reaction in the processing chamber stops or slows down. This suppresses excessive reactions at the electrode terminals of electronic components caused by the formic acid reduction treatment, thereby reducing damage to electronic components caused by the formic acid reduction treatment.

[0032] Furthermore, the pressure inside the processing chamber is reduced again. By reducing the pressure inside the processing chamber, the formic acid inside the chamber is discharged to the outside. The pressure inside the processing chamber at this time is reduced to, for example, the same level as the pressure reduction treatment performed before supplying formic acid to the processing chamber as described above. The pressure inside the processing chamber is not particularly limited as long as the formic acid can be removed from the processing chamber. The pressure inside the processing chamber during this pressure reduction treatment is set appropriately to ensure that the formic acid is sufficiently removed from the processing chamber, depending on the formic acid concentration inside the processing chamber, the amount of formic acid supplied, etc.

[0033] Furthermore, in a formic acid reflow apparatus, it is preferable to recover the formic acid discharged from the processing chamber. It is also preferable to circulate the recovered formic acid within the formic acid reflow apparatus and supply it back into the processing chamber. For formic acid reduction treatment of electronic components, it is preferable to use a formic acid reflow apparatus that has a configuration that allows for the recovery and circulation of formic acid as described above. For example, if the high-concentration formic acid atmosphere used in the above-mentioned formic acid reduction treatment is released directly outside the apparatus, it will have a significant environmental impact. For this reason, it is preferable to circulate the formic acid within the apparatus without releasing it outside. In addition, by circulating unreacted formic acid within the apparatus, the amount of formic acid used can be reduced. This makes it possible to reduce the electrodes of electronic components by formic acid reduction treatment at a low cost.

[0034] Next, the formic acid inside the processing chamber is discharged to the outside, and then inert gas is supplied back into the processing chamber to return the pressure inside the chamber to atmospheric pressure. Then, the heating inside the processing chamber is stopped. After the temperature inside the processing chamber has cooled sufficiently, the electronic components are recovered from the processing chamber. Through the above process, a method for reducing the electrodes of electronic components using formic acid reduction can be implemented.

[0035] [Specific example of a method for reducing electrodes in electronic components (1)] Next, we will explain a specific example (1) using the aforementioned method for reducing the electrodes of electronic components. Figure 2 shows a two-axis graph illustrating the relationship between temperature, pressure, and time in the formic acid reflow apparatus during the formic acid reduction treatment method for reducing electrodes of electronic components described above. In the graph shown in Figure 2, the vertical axis (left axis) represents temperature [°C], the vertical axis (right axis) represents the logarithmic pressure in the processing chamber [Pa], and the horizontal axis represents time [seconds (sec)]. In addition, in the graph shown in Figure 2, solid line 20 shows the relationship between pressure in the processing chamber and time, and solid line 21 shows the relationship between the temperature of the electronic component housed in the processing chamber and time.

[0036] First, the electronic components to be subjected to formic acid reduction treatment are placed inside the processing chamber of the formic acid reflow apparatus. Then, as shown by the solid line 20 in Figure 2, the pressure inside the processing chamber is reduced to release the air (atmosphere) inside the processing chamber, and an inert gas is supplied. In Figure 2, the process of reducing the pressure inside the processing chamber and returning to atmospheric pressure by supplying an inert gas is performed twice. This replaces the air inside the processing chamber with an inert gas such as nitrogen.

[0037] Furthermore, the processing chamber containing the electronic components is heated, and the electronic components are heated as shown by the solid line 21 in Figure 2. Heating of the processing chamber may be started after replacing the processing chamber with an inert gas, or it may be performed at the same time as the inert gas replacement process. Replacing the processing chamber with an inert gas is necessary to suppress unwanted reactions such as oxidation of the electrodes of the electronic components by oxygen, etc., but at low temperatures, reactions that would affect the reliability of the actual electronic components are unlikely to occur. For this reason, the inert gas replacement process may be performed at low temperatures immediately after starting heating of the processing chamber.

[0038] Next, the processing chamber is heated until it reaches a predetermined temperature. In the example shown in Figure 2, the temperature inside the processing chamber for formic acid reduction is set to 180°C. As shown by the solid line 21, the temperature of the electronic components is also heated to approximately 180°C. In the example shown in Figure 2, approximately 80 seconds have passed for the electronic components to heat up to the specified temperature. In Figure 2, the solid line 21 represents the temperature inside the electronic component package. In the example with a set temperature of 180°C shown in Figure 2, no significant temperature difference was obtained between the inside of the electronic component package and the electrode terminals; therefore, only the temperature inside the package is shown in Figure 2.

[0039] Next, as shown by the solid line 20, the pressure inside the treatment chamber with an inert gas atmosphere is reduced. In Figure 2, the period during which the reduced pressure treatment is performed (reduced pressure period) is shown as period 22. As shown in Figure 2, the pressure inside the treatment chamber is approximately the same as atmospheric pressure (approximately 1 × 10⁻⁶). 5 The pressure is reduced from Pa to below 100 Pa. In the example shown in Figure 2, it takes about 50 seconds to reduce the pressure inside the processing chamber.

[0040] Next, formic acid is supplied to the processing chamber under reduced pressure. Then, the electrode terminals of the electronic components are subjected to formic acid reduction treatment. As shown in Figure 2, by supplying formic acid, the pressure inside the processing chamber, which has been reduced to less than 100 Pa, drops to 5 × 10⁻⁶ 3 The pressure increases to approximately Pa. The pressure inside the treatment chamber after formic acid is supplied depends on the volume inside the treatment chamber and the amount of formic acid supplied. In Figure 2, the duration of the formic acid reduction treatment is shown as period 23. In the example shown in Figure 2, the treatment duration is 10 seconds.

[0041] Next, the depressurization in the processing chamber is released and inert gas is supplied to the processing chamber, returning the pressure inside the processing chamber to atmospheric pressure. In Figure 2, the period for the process of returning the pressure inside the processing chamber to atmospheric pressure is shown as period 24. As shown in Figure 2, by supplying inert gas to the processing chamber, 5 × 10 3 The pressure, which was around Pa, was reduced to atmospheric pressure (approximately 1 × 10⁻⁶). 5 The pressure is increased to approximately Pa. This reduces the formic acid concentration in the treatment chamber, stopping or mitigating the formic acid reduction reaction. In the example shown in Figure 2, it takes about 20 seconds to return the pressure to atmospheric pressure.

[0042] Next, the pressure inside the processing chamber is reduced to discharge the formic acid inside the chamber to the outside. Then, inert gas is supplied back into the processing chamber to return the pressure inside the chamber to atmospheric pressure. In Figure 2, the period of the process from reduced pressure to returning to atmospheric pressure inside the processing chamber is shown as period 25. As shown in Figure 2, the pressure inside the processing chamber is reduced to about 100 Pa in order to discharge the formic acid inside the processing chamber to the outside. Furthermore, after the reduction in pressure, inert gas is supplied back into the processing chamber to return the pressure to atmospheric pressure. In the example shown in Figure 2, the period required from the start of the reduction in pressure to returning to atmospheric pressure is about 50 seconds.

[0043] After returning the pressure inside the processing chamber to atmospheric pressure, heating inside the chamber is stopped. As a result, the temperature of the electronic components gradually decreases, as shown by the solid line 21 in Figure 2. After the temperature of the electronic components has sufficiently decreased, they are retrieved from the processing chamber.

[0044] In the reduction treatment of electrode terminals of electronic components using the formic acid reduction treatment described above, the processing time for supplying formic acid and performing surface treatment on the electrode terminals is approximately 10 seconds. Furthermore, the time during which the electronic component is heated to 150°C or higher from the start to the end of the reduction treatment of the electrode terminals of the electronic component is approximately 150 seconds. As described above, in the method for reducing the electrode terminals of electronic components according to this embodiment, the formic acid reduction treatment of the electrode terminals is performed using a high concentration of formic acid, making it possible to perform the reduction treatment of the electrode terminals at a temperature of about 180°C. Furthermore, because a high concentration of formic acid is used for the formic acid reduction treatment of the electrode terminals, the treatment time can be shortened. As a result, compared to conventional reduction treatments using formic acid, it is possible to perform the reduction treatment of the electrode terminals of electronic components at a lower temperature and in a shorter time. Therefore, thermal damage to electronic components can be suppressed, and a decrease in the reliability of electronic components can be suppressed.

[0045] [Specific examples of methods for reducing electrodes in electronic components (2)] Next, we will explain a specific example (2) using the method for reducing the electrodes of the electronic components described above. Note that the following specific example (2) uses the same conditions as specific example (1) above, except that the set temperature is changed to 220°C. Therefore, the explanations similar to those for specific example (1) above will be omitted.

[0046] Figure 3 shows a two-axis graph illustrating the relationship between temperature, pressure, and time inside the formic acid reflow apparatus in the formic acid reduction treatment method for reducing electrodes of electronic components described above. In the graph shown in Figure 3, the vertical axis (left axis) is temperature [°C], the vertical axis (right axis) is the logarithmic pressure inside the processing chamber [Pa], and the horizontal axis is time [seconds (sec)]. Furthermore, the graph shown in Figure 3 is an example where the set temperature was raised to 220°C. In the graph shown in Figure 3, the dashed line 30 shows the relationship between pressure and time inside the processing chamber. The solid line 31 shows the relationship between the temperature of the central part of the electronic component package housed inside the processing chamber and time. The solid line 32 shows the relationship between the temperature of the base of the electrode terminals of the electronic component housed inside the processing chamber and time. The solid line 33 shows the relationship between the temperature of the tip of the electrode terminals of the electronic component housed inside the processing chamber and time.

[0047] First, an electronic component to be subjected to formic acid reduction treatment is accommodated in a processing chamber of a formic acid reflow apparatus. Then, as indicated by a broken line 30 in FIG. 3, the pressure inside the processing chamber is reduced, the air (atmosphere) in the processing chamber is discharged, and an inert gas is supplied. Further, the inside of the processing chamber accommodating the electronic component is heated, and the electronic component is heated as indicated by solid lines 31, 32, and 33 in FIG. 3. At this time, in the electronic component, the temperature at the tip end portion of the electrode terminal indicated by the solid line 33 is the highest, and the electronic component is heated to over 230°C. Also, as indicated by the solid line 31, the temperature at the central portion of the package of the electronic component is the lowest, and the electronic component is heated to approximately 220°C. The temperature at the root portion of the electrode terminal indicated by the solid line 32 tends to be slightly lower than that at the tip end portion, and the root portion is heated to approximately 230°C.

[0048] Next, as indicated by the broken line 30, the pressure inside the processing chamber in an inert gas atmosphere is reduced. As shown in FIG. 3, the pressure inside the processing chamber, which is approximately the same as atmospheric pressure (about 1×10 5 Pa), is reduced to 100 Pa or lower. In the example shown in FIG. 3, the period 22 of the pressure reduction processing in the processing chamber is approximately 15 seconds.

[0049] Next, with the pressure inside the processing chamber kept reduced, formic acid is supplied into the processing chamber to perform formic acid reduction treatment on the electrode terminals of the electronic component. As shown in FIG. 3, supplying formic acid causes the pressure inside the processing chamber, which has been reduced to 100 Pa or lower, to become 5×10 3 Pa, and the pressure increases to this level. The pressure depends on the volume inside the processing chamber and the amount of formic acid supplied. In FIG. 3, the period 23 of the formic acid reduction treatment is 10 seconds.

[0050] Next, the pressure reduction in the processing chamber is released, an inert gas is supplied into the processing chamber, and the pressure inside the processing chamber is returned to normal pressure. By supplying the inert gas into the processing chamber, the pressure, which was approximately 5×10 3 Pa, is adjusted to normal pressure (about 1×10 5 Pa), the formic acid concentration in the processing chamber is reduced to stop or mitigate the reaction of the formic acid reduction treatment. In FIG. 3, the period 24 of the processing for returning the pressure inside the processing chamber to normal pressure is approximately 20 seconds.

[0051] Next, the pressure inside the processing chamber is reduced to discharge the formic acid inside the chamber to the outside. Then, inert gas is supplied back into the processing chamber to return the pressure inside the processing chamber to atmospheric pressure. As shown in Figure 3, in order to discharge the formic acid inside the processing chamber to the outside, the pressure inside the processing chamber is reduced to about 100 Pa, and then inert gas is supplied back into the processing chamber to return the pressure to atmospheric pressure. In the example shown in Figure 3, the period required from the start of depressurization to returning to atmospheric pressure is about 50 seconds.

[0052] After returning the pressure inside the processing chamber to atmospheric pressure, heating inside the chamber is stopped. As a result, the temperature of the electronic components gradually decreases, as shown by the solid lines 31, 32, and 33 in Figure 3. After the temperature of the electronic components has sufficiently decreased, they are retrieved from the processing chamber.

[0053] In the reduction treatment of electrode terminals of electronic components using the formic acid reduction treatment described above, the processing time for supplying formic acid and performing surface treatment on the electrode terminals is approximately 10 seconds. Furthermore, the time during which the electronic component is heated to 150°C or higher from the start to the end of the reduction treatment of the electrode terminals of the electronic component is approximately 360 seconds. As described above, in the method for reducing the electrode terminals of electronic components according to this embodiment, by performing formic acid reduction treatment of the electrode terminals using a high concentration of formic acid, it is possible to reduce the electrode terminals in a short time of about 10 seconds, even in a high-temperature environment of about 220°C. As a result, compared to conventional reduction treatment using formic acid, it is possible to reduce the electrode terminals of electronic components at a lower temperature and in a shorter time. Therefore, it is possible to suppress thermal damage to electronic components and suppress the deterioration of the reliability of electronic components.

[0054] [Methods for heating electronic components] This section describes a specific example of a method for heating electronic components using the aforementioned method for reducing the electrodes of electronic components. The electronic components are placed in the processing chamber of the formic acid reflow apparatus and heated within the chamber. The electronic components are placed on a heating element provided in the processing chamber of the formic acid reflow apparatus. By activating the heating element, heat is transferred from the heating element to the electronic components, thereby heating them.

[0055] Figure 4 shows a heating element installed in the processing chamber of a formic acid reflow apparatus, and an electronic component placed on the heating element. In Figure 4, a DIP (Dual Inline Package) is shown as an example of an electronic component. As shown in Figure 4, the electronic component 10 has a package 11 in which a semiconductor element is mounted, and electrode terminals 12 protruding from both sides of the package 11. In the reduction treatment by formic acid reduction, the coating such as solder plating formed on the surface of these electrode terminals 12 is reduced. Furthermore, as shown in Figure 4, the electronic component 10 is placed so that the side of the package 11 where the electrode terminals 12 do not protrude (the top surface) is in direct contact with the heating element 16. The electronic component 10 has a thermocouple 13 attached inside the package 11 for measuring the internal temperature of the package 11. The thermocouple 13 for measuring the internal temperature is inserted into the package 11 through an opening formed in the package 11. The electronic component 10 also has a thermocouple 14 attached to the base of the electrode terminal 12 for measuring the base of the electrode terminal. And the electronic component 10 has a thermocouple 15 attached to the tip of the electrode terminal for measuring the tip of the electrode terminal.

[0056] <3. Second Embodiment of a Method for Reducing Electrodes of Electronic Components> Next, a method for reducing the electrodes of an electronic component according to the second embodiment will be described. In the second embodiment of the method for reducing the electrodes of electronic components, the only difference from the first embodiment described above is the method of heating the electronic components housed in the processing chamber of the formic acid reflow apparatus. Therefore, the same explanation as in the first embodiment described above will be omitted.

[0057] [Methods for heating electronic components] Figure 5 shows a heating element installed in the processing chamber of a formic acid reflow apparatus, and electronic components placed on the heating element. As shown in Figure 5, the electronic component 10 has a package 11 on which a semiconductor element is mounted, and electrode terminals 12 protruding from both sides of the package 11. The electronic component 10 is placed with the side of the package 11 on which the electrode terminals 12 protrude (bottom surface) facing the heating element 16. The electronic component 10 has a thermocouple 13 attached inside the package 11 for measuring the internal temperature of the package 11. The electronic component 10 also has a thermocouple 14 attached to the base of the electrode terminal 12 for measuring the base of the electrode terminal. Furthermore, the electronic component 10 has a thermocouple (not shown) attached to the tip of the electrode terminal for measuring the base of the electrode terminal.

[0058] Furthermore, a jig 17 is positioned between the bottom surface of the package 11 and the heating element 16. The height of the jig 17 is greater than the distance from the bottom surface of the package 11 to the tip of the electrode terminal 12. As a result, the presence of the jig 17 between the package 11 and the heating element 16 prevents the electronic component 10 from directly contacting the heating element 16, and it is held in a state of being suspended from the heating element 16.

[0059] [Temperature changes in electronic components] Figure 6 shows the temperature change when heating is applied to an electronic component housed in the processing chamber of a formic acid reflow apparatus in the state described in Figure 5 above. In Figure 6, the vertical axis is temperature [°C] and the horizontal axis is time [seconds (sec)]. In Figure 6, the temperature at the tip of the electrode terminal of the electronic component is shown by the solid line 41, and the temperature inside the package is shown by the dashed line 42.

[0060] As shown in Figure 6, the temperature at the tip of the electrode terminal, indicated by the solid line 41, rises to approximately 200°C. In contrast, the temperature inside the package, indicated by the dashed line 42, rises to approximately 180°C. Therefore, there is a difference of about 20°C between the temperature at the tip of the electrode terminal and the temperature inside the package. In the heating method of the first embodiment shown in Figure 3 above, the temperature difference between the tip of the electrode terminal and the temperature inside the package is about 10°C. In other words, by housing the electronic components in the processing chamber in the manner shown in Figure 5 above, the rise in temperature inside the package relative to the temperature at the tip of the electrode terminals can be suppressed. Therefore, by applying the heating method for electronic components shown in Figure 5 above, it becomes possible to heat the electronic components in a way that prevents heat from reaching the semiconductor elements inside the processing chamber. As a result, even under conditions where the processing time is long, as shown in Distribution 2 of Figure 1 above, it becomes possible to heat the electronic components without raising their internal temperature, thereby reducing the thermal load on the semiconductor elements of the electronic components and ensuring the reliability of the electronic components.

[0061] [Specific examples of methods for reducing electrodes in electronic components (3)] Next, we will describe a specific example (3) of the electrode reduction method that applies the electronic component heating method described above. Note that the following specific example (3) uses the same conditions as specific example (2) above, except that it applies the electronic component heating method shown in Figure 5. Therefore, the same explanation as in specific example (2) above will be omitted.

[0062] Figure 7 shows a two-axis graph illustrating the relationship between temperature, pressure, and time inside the formic acid reflow apparatus in the formic acid reduction treatment method for reducing electrodes of electronic components described above. In the graph shown in Figure 7, the vertical axis (left axis) is temperature [°C], the vertical axis (right axis) is the logarithmic pressure inside the processing chamber [Pa], and the horizontal axis is time [seconds (sec)]. Furthermore, in the graph shown in Figure 7, the solid line 70 shows the relationship between pressure and time inside the processing chamber. The solid line 71 shows the relationship between the temperature of the central part of the electronic component package housed inside the processing chamber and time.

[0063] First, the electronic components to be subjected to formic acid reduction treatment are placed inside the processing chamber of the formic acid reflow apparatus. Then, as shown by the solid line 70 in Figure 7, the pressure inside the processing chamber is reduced to release the air (atmosphere) inside the processing chamber and supply an inert gas. Furthermore, the processing chamber containing the electronic components is heated, and the electronic components are heated as shown by the solid line 71 in Figure 7. At this time, as shown by the solid line 71, the temperature of the central part of the electronic component package is heated to approximately 220°C.

[0064] Next, as shown by the solid line 70, the pressure inside the treatment chamber with an inert gas atmosphere is reduced. As shown in Figure 7, the pressure inside the treatment chamber is approximately equal to atmospheric pressure (approximately 1 × 10⁻⁶). 5 The pressure is reduced from Pa to 100 Pa or less. In the example shown in Figure 7, the period of depressurization in the treatment chamber is approximately 25 seconds.

[0065] Next, with the pressure inside the processing chamber reduced, formic acid is supplied to the processing chamber to perform formic acid reduction treatment on the electrode terminals of the electronic components. As shown in Figure 7, by supplying formic acid, the pressure inside the processing chamber, which has been reduced to less than 100 Pa, is reduced to 5 × 10⁻⁶ 3 The pressure increases to approximately Pa. The pressure depends on the volume in the treatment chamber and the amount of formic acid supplied. In Figure 7, the duration of the formic acid reduction treatment 23 is 10 seconds.

[0066] Next, the depressurization in the processing chamber is released, and inert gas is supplied to the processing chamber, returning the pressure inside the processing chamber to atmospheric pressure. By supplying inert gas to the processing chamber, 5 × 10 3 The pressure, which was around Pa, was reduced to atmospheric pressure (approximately 1 × 10⁻⁶). 5 The pressure is increased to approximately Pa to reduce the formic acid concentration in the treatment chamber, thereby stopping or mitigating the formic acid reduction reaction. In Figure 7, the treatment period 24 for returning the pressure in the treatment chamber to atmospheric pressure is approximately 20 seconds.

[0067] Next, the pressure inside the processing chamber is reduced to discharge the formic acid inside the chamber to the outside. Then, inert gas is supplied back into the processing chamber to return the pressure inside the processing chamber to atmospheric pressure. As shown in Figure 7, in order to discharge the formic acid inside the processing chamber to the outside, the pressure inside the processing chamber is reduced to about 100 Pa, and then inert gas is supplied back into the processing chamber to return the pressure to atmospheric pressure. In the example shown in Figure 7, the period required from the start of depressurization to returning to atmospheric pressure is about 60 seconds.

[0068] After returning the pressure inside the processing chamber to atmospheric pressure, heating inside the chamber is stopped. As a result, the temperature of the electronic components gradually decreases, as shown by the solid line 71 in Figure 7. After the temperature of the electronic components has sufficiently decreased, they are retrieved from the processing chamber.

[0069] In the reduction treatment of electrode terminals of electronic components using the formic acid reduction treatment described above, the processing time for supplying formic acid and performing surface treatment on the electrode terminals is approximately 10 seconds. Furthermore, the time during which the electronic component is heated to 150°C or higher from the start to the end of the reduction treatment of the electrode terminals of the electronic component is approximately 220 seconds. Thus, in the method for reducing the electrode terminals of electronic components of this embodiment, the electrode terminals can be reduced by performing a formic acid reduction treatment on the electrode terminals using a high concentration of formic acid. As a result, a heating method that can suppress the rise in temperature inside the package can suppress thermal damage to the electronic components and prevent a decrease in the reliability of the electronic components.

[0070] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible. For example, the embodiments described above are explained in detail to make the present invention easier to understand, and the present invention is not necessarily limited to embodiments that have all the described configurations. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment. It is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to delete or add / replace parts of the configuration of each embodiment. [Explanation of Symbols]

[0071] 1,2 Distribution, 10 Electronic component, 11 Package, 12 Electrode terminal, 13,14,15 Thermocouple, 16 Heating heater, 17 Jig, 22,23,24,25 Period, 3,20,21,30,31,32,33,41,51,52,53,70,71 Solid line, 42 Dashed line

Claims

1. The electronic components are placed inside the processing chamber. The electronic component is heated to a predetermined temperature in the processing chamber. The pressure inside the aforementioned processing chamber is reduced, Formic acid is supplied into the processing chamber to reduce the electrode surface of the electronic component in a formic acid atmosphere for a certain period of time. The pressure in the aforementioned processing chamber is released, Stop heating the aforementioned electronic component. A method for reducing electrodes in electronic components.

2. The heating temperature of the electronic component is below a predetermined temperature that serves as a degradation standard for the semiconductor element embedded in the electronic component. A method for reducing the electrodes of an electronic component according to claim 1.

3. The heating temperature of the electronic component is set based on the junction temperature of the PN junction of the semiconductor element. A method for reducing the electrodes of an electronic component according to claim 2.

4. The heating temperature of the electronic component is less than or equal to the maximum rated value of the junction temperature of the semiconductor element. A method for reducing the electrodes of an electronic component according to claim 3.

5. The formic acid concentration in the aforementioned processing chamber is 98% or higher. A method for reducing the electrodes of an electronic component according to claim 1.

6. The formic acid concentration in the processing chamber is set so that the internal temperature of the component does not exceed a predetermined temperature that serves as a degradation standard for the electronic component during the time it takes to complete the reduction process. A method for reducing the electrodes of an electronic component according to claim 1.

7. The processing time in the formic acid atmosphere is 1 to 10 seconds. A method for reducing the electrodes of an electronic component according to claim 1.

8. The aforementioned electronic component is placed in direct contact with the heater in the processing chamber. A method for reducing the electrodes of an electronic component according to claim 1.

9. The electronic component is held in a suspended state above the heater in the processing chamber. A method for reducing the electrodes of an electronic component according to claim 1.

10. After stopping the heating of the electronic component, the pressure inside the processing chamber is reduced again to recover the formic acid supplied to the processing chamber, and the recovered formic acid is circulated within the apparatus and supplied back into the processing chamber. A method for reducing the electrodes of an electronic component according to claim 1.

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