WO2000044958A1 - Method of preserving surface-treated member - Google Patents

Abstract

A treated member after subjected to fluorination is placed in a room-temperature, dry air, or a dry nitrogen gas, or a dry atmosphere such as vacuum.

Description

 Description Preservation method for surface-treated products

 The present invention relates to a method for storing a surface-treated member for a long time, and more particularly to a method for storing a surface-treated product that has been surface-treated using a halogen-based gas. Background art

 Conventionally, a member to be processed such as a metal or a semiconductor substrate has been placed in a vacuum and subjected to surface treatment using vacuum plasma to improve wettability to solder. However, surface treatment using vacuum plasma requires not only expensive vacuum equipment but also much time and labor such as the need to reduce pressure. For this reason, in recent years, a reactive halogen-based gas such as hydrogen fluoride (HF) has been generated by atmospheric pressure discharge that does not require a vacuum device, and this halogen-based gas is used to process the workpiece under atmospheric pressure. Has been put to practical use.

 However, if the member (surface-treated product) subjected to surface treatment (fluorination treatment) with a treatment gas containing fluorine gas or hydrogen fluoride gas is left in the air, the effect of the surface treatment disappears in about three hours. . That is, after performing fluoridation treatment with a treatment gas containing fluorine gas or hydrogen fluoride gas, the pH value of the surface of the surface-treated product is measured using pH test paper. If it is less than 6 but left in the atmosphere for about 3 [^], the pH value will be 7 and it will be neutral, and the effect of the surface treatment will be lost. For this reason, the surface treatment device is connected to the next process device (for example, a joining device), or the surface treatment device is incorporated in the next process device. Next, it is desirable to perform a process such as soldering in the next step.

However, the target material whose surface has been treated for In some cases, such as when the surface treatment is not possible, it is necessary to store the surface-treated product for a long time. Therefore, it has been desired to develop a method for preserving the surface-treated product for a long time without losing the effect of the surface treatment.

 The present invention has been made in view of the above-described demands, and has as its object to enable a member to be subjected to surface treatment to be stored for a long time while maintaining the effect of the surface treatment.

Disclosure of the invention

According to the study of the present inventors, when a member to be treated is subjected to a fluoridation treatment as a surface treatment, there is a correlation between the amount of HF detected as a pH value and the effect of the fluoridation treatment. I found out. In this case, the HF detected as the pH value using the pH test paper is F that is not chemically bonded to the surface-treated member (surface-treated product), that is, the surface of the surface-treated product. It is probable that F attached to the surface reacts with water contained in the pH test paper to form HF, and this HF is detected. When the fluoridation treatment is performed, the surface treatment is effective when the pH value is about 6 or less. When the pH value is 6, the amount of F present on the surface of the surface-treated product is approximately equal to 10 ¹⁴ / cm ² .

 In addition, according to the study of the present inventors, it has been found that when the fluorinated member to be treated is left in the air, the effect of the surface treatment is largely affected by the moisture in the air. The mechanism is

(1) HF next to F are reacted with H ₂ 0 which is attached to the surface of the surface treated product, is released by HF This is vaporized in the air F is due to be reduced.

(2) F adhering to the surface of the surface-treated product is reacted with the surface treatment article itself and the H ₂ 0 in the catalyst, F is taken in the surface-treated product.

 And so on.

The present invention has been made based on the above findings, and in order to achieve the above object, a method for storing a surface-treated product according to the present invention comprises the steps of: It is characterized by placing the workpiece in a dry atmosphere I have.

 In the present invention configured as described above, the halogen such as F adhered to the surface of the member to be treated does not react with the moisture existing in the atmosphere, and the state of attaching to the surface of the member to be treated for a long time is maintained. Therefore, the effect of the surface treatment can be maintained for a long time.

 In a dry atmosphere, keep the dew point below 120 ° C. If the dew point is 120 ° C. or less, the number of water molecules contained in the atmosphere becomes extremely small, and the substantial effect on halogens such as F adhered to the surface of the surface-treated member to be treated is reduced. It can be almost eliminated. More preferably, the temperature is set in the range of 140 ° C. to −30 ° C. The dry atmosphere may be formed of any gas as long as it is stable at room temperature, and may be formed of dry air or nitrogen gas. Dry air and nitrogen gas are stable at room temperature and easy to handle, and can be obtained relatively inexpensively to reduce storage costs. Further, the dried atmosphere may be formed under reduced pressure. When the pressure is reduced, water molecules are discharged together with the nitrogen gas molecules and the oxygen gas molecules, so that they hardly exist in the decompression vessel. Can last. It is desirable that the surface-treated member is kept at a temperature equal to or lower than room temperature. If the surface-treated member is stored at a high temperature of, for example, 80 ° C or more, F or the like adhering to the surface of the member receives thermal energy from the surroundings and separates from the surface of the member. The effect of the surface treatment will be lost. For this reason, it is desirable that the member to be processed be stored at a temperature as low as possible. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is an explanatory diagram of a surface treatment apparatus used in an example.

 FIG. 2 is a view showing a relationship between a pH value and a difference in a standing atmosphere of a fluorinated solder plating copper plate in an example.

FIG. 3 shows the results of a wetting and spreading test on a gold plating substrate with respect to differences in the atmosphere in which the fluorinated solder balls were left in the example. FIG. 4 is a diagram showing the relationship between the difference in the atmosphere in which the fluorinated tin pellets were left in the working example and the solid bonding strength with the gold plating substrate.

 Fig. 5 shows the leaching time, the pH value of the solder plating copper plate, the solder ball wetting and spreading, and the tin pellet when the solder plating copper plate, solder ball, and tin pellet were fluorinated and left in the air. It is a figure which shows the relationship with solid joining strength. BEST MODE FOR CARRYING OUT THE INVENTION

 A preferred embodiment of the method for storing a surface-treated product according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a surface treatment apparatus for fluorinating a member to be treated. In FIG. 1, in a surface treatment apparatus 10, a discharge unit 16 is connected to a source gas source 12 via a source gas pipe 14. The raw material gas pipe 14 is provided with a flow control valve 18 such as a mass flow controller. The carbon tetrafluoride gas is a stable fluorine-based gas supplied from the raw material gas source 12 to the discharge unit 16. (CF ₄ ) can be adjusted at will. One end of a branch pipe 20 is connected to the source gas pipe 14 between the source gas source 12 and the flow control valve 18. The other end of the branch pipe 20 is connected to a water bubbling unit 24 via a flow control valve 22 such as a mass flow controller, and a part of the carbon tetrafluoride gas is supplied to the water bubbling unit 24. I can guide you. The water bubbling unit 24 is connected to one end of a pipe 26 connected to the raw material gas pipe 14 downstream of the flow control valve 18 so that the four baffles flowing into the water bubbling unit 24 are connected. Water (steam) is added to the carbonized gas so that it can be returned to the raw material gas piping 14.

The discharge unit 16 is provided with a heater 28 so as to prevent condensation of water vapor flowing in with the carbon tetrafluoride gas. The discharge unit 16 is connected to a processing gas pipe 32 connected to a processing chamber 30 at a tip thereof, and is formed by reacting carbon tetrafluoride gas with water vapor by electric discharge. A reactive fluorine-based gas such as is supplied via a processing gas pipe 32 to a processing chamber 30 in which a member to be processed 34 is disposed. A nitrogen gas source 38 is connected to the processing gas pipe 32 via a carrier gas pipe 36. A flow control valve 40 is provided in the carrier gas pipe 36, and a nitrogen gas serving as a carrier gas for transporting the active fluorine-based gas generated in the discharge unit 16 to the processing chamber 30. The amount can be adjusted arbitrarily. One end of a branch pipe 42 is connected to the carrier gas pipe 36 on the upstream side of the flow control valve 40. The branch pipe 42 is provided with a flow control valve 44 and a heater 46, and has the other end connected downstream from the carrier gas pipe connection part of the processing gas pipe 32. A part of the nitrogen gas from 38 is heated and supplied to the processing gas pipe 32.

 The processing chamber 30 is formed in, for example, a rectangular parallelepiped, a cube, or a cylindrical body, and has a processing gas pipe 32 connected to an upper portion thereof and an exhaust pipe 48 connected thereto, and flows into the processing chamber 30. After that, the processing gas (mixed gas of reactive fluorine-based gas and nitrogen gas) after the fluorination treatment can be introduced into the abatement apparatus 50. Further, the processing chamber 30 is provided with a heat sink 52, which heats and holds the processing target member 34 disposed in the processing chamber 30 at a predetermined temperature to easily perform surface treatment (fluorination processing). ) Is available.

 In the conventional surface treatment apparatus 10 configured as described above, the carbon tetrafluoride gas at atmospheric pressure flowing from the source gas source 12 to the source gas pipe 14 is dried through the flow control valve 18. At the same time, a part of the carbon tetrafluoride gas is flowed into the water publishing unit 24 to add steam, and the discharge unit is supplied through the pipe 26 and the raw material gas pipe 14. To 16 The discharge unit 16 generates a gas discharge through a mixed gas of carbon tetrafluoride gas and water vapor,

CF ₄ + H ₂₀ → COF ₂ + 2 HF

COF ₂ + H ₂₀ → CO ₂ + 2 HF

The CF ₄ reacts with the steam (H ₂ 0) to generate a reactive fluorine gas such as HF and sends it to the processing gas pipe 32 as shown in FIG. The reactive fluorine-based gas from the discharge unit 16 flows into the processing gas pipe 32 via the carrier gas pipe 36 and flows into the processing gas pipe 32 via the branch pipe 42. It is mixed with the dried heated nitrogen gas and flows into the processing chamber 30 as a fluorinated gas. The member 34 to be processed, such as a metal, disposed in the processing chamber 30 is fluorinated (surface-treated) in contact with the processing gas, and is subjected to a process for improving solder wettability. Further, the processing gas obtained by surface-treating the member to be processed 34 is sent to the abatement apparatus 50 via the exhaust pipe 48 to be rendered harmless and released into the atmosphere. The material to be treated (surface treated product) 34 should be placed in dry air or dry nitrogen gas, or in a vacuum under reduced pressure, and kept at room temperature or lower. As a result, the surface-treated product can be stored for a long time without losing the effect of the fluoridation treatment, and the surface treatment can be performed even if the treatment cannot be immediately performed in the next process. And the flexibility of production planning can be improved.

 【Example】

The sample was fluorinated using the surface treatment device 10 shown in Fig. 1, and it was examined whether the pH value, wet spread, and solid bonding strength were affected by differences in storage atmosphere. In the fluoridation treatment, the conditions of the fluoridation treatment are the same, and the flow rate of dry carbon tetrafluoride gas without adding water (steam) Q! (See Fig. 1) Flow rate of carbon tetrafluoride gas supplied at 10 ml / min to the water coupling unit 24 through the branch pipe 20 and to which water vapor was added by the water coupling unit 24 2 3 0 ml / min, dry have a heated and fed as a carrier gas through the carrier gas pipe 3 6 (dry) flow rate Q ₃ of nitrogen gas 3 0 0 ml / min, pressure heat by the heater 4 6 branch pipes 4 2 dry nitrogen gas at a flow rate Q ₄ was supplied as a diluent gas via that is 3 0 0 ml / min.

The set temperature of heater 28 provided in discharge unit 16 was set to 70 ° C, and the set temperature of heater 46 for heating nitrogen gas was set to 150 ° C. At this time, the discharge unit The junction of the gas from the 16 side and the heated nitrogen gas (the connection point between the processing gas pipe 32 and the branch pipe 42) The temperature of the nitrogen gas at A is about 120 ° C, and the processing that flows into the processing chamber 30 The concentration of HF in the gas is 4400 ppm. Furthermore, the set temperature of the heater 52 provided in the processing chamber 30 was 135 ° C, and the heating temperature of the member to be processed (sample) 34 was 90 ° C.

 In the fluoridation treatment, a sample is first placed in the processing chamber 30, the processing chamber 30 is replaced with dry nitrogen gas for 10 minutes, and then a processing gas having an HF concentration of 4400 ppm is introduced into the processing chamber 30 to fluorinate the sample. Immediately after the completion of the fluoridation treatment, a dry nitrogen gas was introduced into the treatment chamber 30 and replaced with nitrogen gas for 10 minutes. << Example 1 >>

 A sample with a copper plate soldered is fluorinated under the above conditions.After leaving for 3 hours in various atmospheres, the surface residual F is measured using a pH test paper wetted with water. Asked. The sample used was a copper plate with a length of 5 mm, a width of 5 mm, and a thickness of 0.2 mm, which was soldered with 80% tin and 20% lead. FIG. 2 shows the state of the atmosphere and the pH value after 3 hours.

As is evident from Fig. 2, when the fluorinated sample was left in the atmosphere (relative humidity of about 40%) for 3 hours, the pH value showed a neutral value of 7.0. It will not change. This is considered to be because the moisture in the atmosphere reacts with F adhering to the sample to become HF and evaporates into the atmosphere, and the moisture acts as a catalyst, and F is taken into the solder plating. In addition, even if the storage atmosphere is dry (dry) nitrogen gas, if the holding temperature is as high as 100 ° C, the effect of the fluoridation treatment disappears after 3 hours. This is probably because F attached to the sample gained thermal energy and separated from the sample. Even if the standing atmosphere is nitrogen gas, the effect of the fluoridation treatment is lost after 3 hours in nitrogen gas to which water is added and the relative humidity is 76%. The reason for this is thought to be due to the moisture contained in the nitrogen gas, indicating that moisture is a major factor in losing the effect of the surface treatment. On the other hand, if the storage atmosphere is dry air (dew point: about -20 ° C), dry nitrogen gas (dew point: about 150 ° C), dry oxygen gas, and vacuum (vacuum degree: 13Pa), 3 hours have passed. of The pH value was the same as that immediately after the fluorination treatment, and the pH test was also good. For this reason, surface treatment products that have undergone fluoridation can lose their long-term surface treatment effects by placing them in a dry atmosphere at room temperature, in dry air, in dry nitrogen gas, or in a vacuum. Can be stored without having to.

 In FIG. 2, a mark 〇 indicates that the state is the same as that immediately after the fluoridation treatment, and a mark X indicates that the effect of the fluoridation treatment is reduced to the same degree as that of the untreated treatment.

 << Example 2 >>

 A 0.74 mm diameter solder ball made of 63% tin and 37% lead solder is fluorinated under the above conditions, left in a different atmosphere for 3 hours, and then placed on a gold-plated substrate Then, a wet spread test was conducted to check the spread of the solder balls. The board on which the solder balls are placed is a glass epoxy board made of glass fiber and epoxy resin, with a nickel plating on the surface as a base metal and a 0.3 m thick gold plating on it. Using. Then, after placing the solder balls on the gold plating, the solder balls were melted by heating to about 240 ° C. in a nitrogen gas atmosphere, and the spread was observed. Figure 3 shows the results of the experiment. The meanings of the symbols Δ and X shown in the figure are the same as those in FIG. 2, and the symbol Δ indicates that the effect of the fluorine treatment is lower than immediately after the treatment.

 As shown in the figure, when the fluorinated solder balls are left in the atmosphere (about 40% relative humidity) or in dry nitrogen gas at 100 ° C for 3 hours, the wetting and spreading test The effect of the fluoridation treatment almost disappears. The two symbols (marks) in the figure indicate the intermediate state between them. For example, those marked with a △ mark and an X mark indicate that the effect of the fluoridation treatment is Although it is greatly reduced, it shows that the effect of treatment is slightly smaller than that of the case without treatment.

Also, if left in humid nitrogen gas (relative humidity about 76%), the effect of the fluoridation treatment is completely lost after 3 hours. On the other hand, the atmosphere in which the fluorinated solder balls are placed is dry air (dew point: about 120 ° C), dry nitrogen gas (dew point: about 150 ° C), and vacuum (0.13 Pa ) If left at room temperature, if the holding temperature is room temperature, the effect of the fluoridation treatment on the wetting and spreading test will hardly decrease. For these reasons, it is desirable to store the product in a dry atmosphere at a temperature not higher than room temperature without heating.

 << Example 3 >>

 The tin pellets were fluorinated under the above fluoridation conditions, left in different atmospheres for 3 hours, and then subjected to solid bonding (bonding without melting) to the gold-plated substrate to evaluate the bonding strength. Was. The tin pellet used as the sample is a disk with a diameter of 2 mm and a thickness of l mm. The substrate to which the tin pellets were solid-bonded was a copper substrate having a length of 10 mm, a width of 10 mm, and a thickness of 1 mm, and a gold plating of 0.3 mm thick. At the time of joining, both were heated to about 100 ° C., and a joining pressure of a total load of 6 kgf was applied to the tin pellet to press it against the gold-plated copper substrate. Fig. 4 shows the results. The symbols 〇, △, and X are the same as in Fig. 2.

 Even after leaving the fluorinated tin pellets at room temperature for 3 hours in dry air with a dew point of about --20 ° C and dry nitrogen gas with a dew point of about 150 ° C, the effect of the fluorination treatment is still significant. It was almost the same as immediately after the treatment. On the other hand, when left in the air at a humidity of about 40%, the solid bonding strength is lower than immediately after the treatment even when the holding temperature is room temperature. In addition, when left in a nitrogen gas at room temperature with a humidity of about 76%, in the solid bonding strength test, it decreases to the same level as that of untreated.

 For this reason, it is desirable to store the product in a dry atmosphere at a temperature not higher than room temperature without heating.

 << Comparative Example >>

The copper plates, solder balls, and tin pellets used in Examples 1, 2, and 3 subjected to the solder plating are fluorinated under the above-described fluorination conditions, and then these are immersed in the air at room temperature and a relative humidity of about 40%. It was left to stand, and the changes in the pH value of the solder plating copper plate over time, the spread of the solder balls on the gold-plated substrate, and the solid bonding strength between the tin pellet and the gold-plated substrate were examined. Figure 5 shows the results. The substrate used for the solder ball wetting and spreading test was the same as in Example 2 above, and the substrate used for the solid bonding strength evaluation was the same as in Example 3 above. Further, in the drawings, the symbols 〇, 印, and X are the same as those in the above embodiments. And the blank is a trial Indicates that no experiment was performed.

 As shown in Fig. 5, the effect of the fluoridation treatment does not decrease so much when one hour has passed after being left in the air after the fluoridation treatment. However, after 2 hours, the effect of the fluoridation treatment is clearly reduced. After 3 hours, the pH value becomes 7.0, and the effect of the fluoridation treatment is almost eliminated. However, in the case of solid joining, the effect of the fluoridation treatment remains to some extent. From this, it can be said that the storage of the fluorinated workpiece in the atmosphere is limited to three hours or less. Also, it seems that the effect of the fluoridation treatment has little effect unless the pH value is 6 or less. Industrial applicability

 As described above, according to the present invention, by placing a surface-treated object in a dry atmosphere, halogens such as F adhered to the surface of the member to be treated are present in the atmosphere. It can be prevented from reacting with moisture and detaching from the surface of the member to be treated or being taken into the member to be treated, and can be kept attached to the surface of the member to be treated for a long time, Long-lasting effect of surface treatment

Claims

The scope of the claims 1. A method for preserving a surface-treated article, comprising treating a member to be treated with a halogen-based gas, and then placing the member to be treated in a dry atmosphere. 2. The method according to claim 1, wherein the dry atmosphere has a dew point of −20 ° C. or less. 3. The method for storing a surface-treated product according to claim 2, wherein the dry atmosphere has a dew point set in a range of −40 ° C. to −30 ° C. 4. The method for storing a surface-treated product according to any one of claims 1 to 3, wherein the dry atmosphere is formed by dry air or nitrogen gas. 5. The method for storing a surface-treated product according to any one of claims 1 to 3, wherein the dried atmosphere is formed under reduced pressure. 6. The method for storing a surface-treated product according to any one of claims 1 to 5, wherein the member to be surface-treated is maintained at a temperature equal to or lower than room temperature.