JP2006086311A - Component mounting method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a component mounting method and an apparatus capable of preventing a substrate and a component which have been cleaned from being contaminated, and capable of mounting the component while maintaining a clean state. <P>SOLUTION: The component mounting method comprises a step (S1) of plasma-cleaning the substrate and electronic component in a vacuum chamber; a step (S2) of forming protective films on the surfaces of the plasma-cleaned substrate and electronic component without opening the inside of a vacuum chamber to the atmosphere; a recleaning step (S3) of irradiating ultraviolet rays (or electric beams or atmosphere plasmas) to the substrate and electronic component, which are formed with the protective films thereon, to remove the protective films; and a step (S4) of mounting the electronic component on the substrate of which protective film has been removed. With this configuration, the protective films prevent contaminants in the atmosphere from depositing on the cleaned surfaces of the substrate and electronic component, and the removal of the protective films immediately before the mounting enables bonding while maintaining each surface of the substrate and electronic component in a clean state. Thus, satisfactory bonding can be achieved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a component mounting method and apparatus for flip-chip mounting electronic components on a substrate, and more particularly to an electronic component performed prior to mounting and a component mounting method and apparatus capable of maintaining the effect of cleaning the substrate.

  In the conventional flip chip mounting method, as shown in FIG. 4, the surface of the substrate and the electronic component is plasma cleaned in step S11, and then mounted in the subsequent step S12. In the plasma cleaning process at that time, the surface of the substrate or electronic component is cleaned by placing the substrate and electronic component in the chamber and generating plasma in an atmosphere into which Ar gas or O 2 gas is introduced. In the mounting process, the cleaned substrate and electronic components are taken out into the atmosphere and mounted and mounted on a mounting machine, and good bonding is obtained by using the cleaned substrate and electronic components.

However, in this mounting method, contaminants in the atmosphere are re-adsorbed while the substrate and electronic components after plasma cleaning are taken out from the chamber and mounted, and the effect of cleaning is reduced. In order to solve this problem, it is conceivable to form a protective film after cleaning. As this type of method, there is a technique for generating a protective film after light cleaning. For example, as shown in FIG. 5, a sample 23 is mounted on a sample holder 22 in a light cleaning device 21, and light from a light source 24 ( The protective film is cleaned by ultraviolet rays, electron beams, or X-rays, and the protective film material gas 25 is sprayed on the surface of the sample 23 after the cleaning to generate a protective film that can be removed by the light (for example, patent) Reference 1).
JP 11-214345 A

  As described above, in the conventional mounting method, contaminants in the atmosphere are re-adsorbed while the substrate and electronic components after plasma cleaning are taken out from the chamber and mounted, and the effect of cleaning is reduced. was there. Even in the method of forming the protective film after the light cleaning, there is a problem that contamination by inorganic substances such as sweat components (NaCL, KCL, etc.) from the human body occurs during the light cleaning.

  SUMMARY OF THE INVENTION The present invention solves the above-described problems, and an object of the present invention is to provide a component mounting method and apparatus capable of preventing contamination of a substrate and electronic components after cleaning and mounting them while maintaining a clean state.

  In order to solve the above-described problems, a component mounting method according to the present invention includes a step of plasma cleaning a substrate and an electronic component in a vacuum chamber, and the plasma cleaned substrate and electronic component without opening the vacuum chamber to the atmosphere. Forming a protective film on the surface, removing the protective film by irradiating the substrate and electronic components on which the protective film is formed with ultraviolet rays, an electron beam or atmospheric plasma, and removing the protective film And a step of mounting an electronic component on the substrate.

  The component mounting apparatus of the present invention includes a vacuum chamber, an etching gas plasma for cleaning a surface of the processing object in the vacuum chamber in which the processing object that is at least one of a substrate and an electronic component is installed, and the A plasma processing apparatus having plasma generating means for sequentially generating plasma of a reactive gas that forms a protective film on the surface of the object to be processed and irradiation with ultraviolet rays, electron beams or atmospheric plasma capable of removing the protective film And a mounting machine for mounting and mounting the substrate on which the protective film is formed and the electronic component.

  According to the component mounting method and the component mounting apparatus described above, adhesion of atmospheric contaminants to the substrate surface and electronic component surface after plasma cleaning can be prevented by the protective film, and this protective film is removed immediately before mounting. By doing so, each surface can be joined in a clean state. Therefore, good bonding can be obtained.

  In mounting using a flip chip mounting machine, it is possible to irradiate ultraviolet rays, electron beams, or atmospheric plasma until just before mounting without obstructions such as tools, so that the joint (electrode) can be maintained in a cleaner state.

  Since the component mounting method and apparatus of the present invention have a configuration in which a substrate and an electronic component are plasma-cleaned and a protective film is formed on the surface of the cleaned substrate and electronic component without being exposed to the atmosphere. The protective film can prevent the adhesion of contaminants in the air to the subsequent substrate surface and electronic component surface. By removing this protective film immediately before mounting, each surface can be bonded in a clean state. Is possible. Therefore, good bonding can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a flowchart showing a flow of a component mounting method according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a plasma processing apparatus constituting a component mounting apparatus used in the component mounting method, and FIG. It is a partial enlarged view of the mounting machine which comprises an apparatus.

  In this component mounting method, as shown in FIG. 1, first, a substrate and electronic components are put in a chamber and plasma cleaned (step S1), and the cleaned substrate and electronic components are released in the same chamber without opening to the atmosphere. A protective film is formed on the surface of the component (step S2).

  Next, the substrate and electronic components are taken out of the chamber, mounted on the mounting machine, and cleaned again in that state (step S3). In this case, since contaminants in the atmosphere only adhere on the protective film and the substrate and electronic components are not contaminated, re-cleaning means removing the protective film. Then, the cleaned electronic component is mounted on the substrate (step S4). In this way, as a result of re-cleaning the substrate and electronic components immediately before mounting and mounting them in a cleaned state, good bonding can be obtained.

Details will be described below.
In the plasma processing apparatus shown in FIG. 2, the chamber 1 is provided with a lower electrode 3 insulated by an insulator 2 and an openable / closable cover 4 facing the lower electrode 3, and an exhaust duct 5 and gas supply The nozzles 6 and 7 are open to the side, the openable / closable lid 4 is grounded, the high frequency power supply 8 is connected to the lower electrode 3, and the exhaust duct 5 and the nozzles 6 and 7 are respectively connected to a vacuum pump, a gas tank, etc. Plasma can be generated in the chamber 1 in a state of being connected to an unillustrated).

  At the time of plasma cleaning, the substrate 9 and the electronic component 10 to be cleaned are placed on the lower electrode 3 and then evacuated through the exhaust duct 5. The pressure in the chamber 1 at this time is desirably 10 Pa or less.

Next, Ar gas as a cleaning gas is sprayed from the nozzle 6 into the chamber 1 at a flow rate of 7 sccm, and high-frequency power is output from the high-frequency power source 8 to the lower electrode 3 while maintaining the pressure in the chamber 1 at 10 Pa, for example, output 7 mW / mm. ² , Ar plasma is generated in the chamber 1, and surface cleaning is performed by etching the electrode surfaces of the substrate 9 and the electronic component 10 by several nm. After the cleaning is completed, the supply of the cleaning gas is stopped and the Ar gas is exhausted.

In forming the protective film, CHF ₃ gas as a reactive gas for the protective film is sprayed from the nozzle 6 at a flow rate of 20 sccm without opening the chamber 1 to the atmosphere, and the high-frequency power source is maintained while maintaining the internal pressure of the chamber 1 at 80 Pa. By supplying high-frequency power to the lower electrode 3 from 8 at an output of 4 mW / mm ² , for example, plasma of CHF ₃ gas is generated in the chamber 1, and the substrate 9 and the electronic component 10 previously cleaned have several A protective film made of a monomolecular layer of nm or several molecular layers of hydrocarbon and hydrogen fluoride is formed. After the film formation is completed, the supply of reactive gas is stopped, the exhaust is stopped, and the atmosphere is released. Then, the substrate 9 and the electronic component 10 are taken out from the chamber 1.

  In the mounting machine shown in FIG. 3, 11 is a stage on which a substrate 9 is installed, 12 is a bonding tool capable of adsorbing an electronic component 10, and includes a motor, a cylinder, etc. as a mechanism for vertical movement, It is controlled by. Reference numerals 13 and 14 denote a substrate-side light source and an electronic component-side light source, respectively, and ultraviolet rays (or electron beams or atmospheric plasma) are emitted from just before mounting to mounting on the substrate 9 on the stage 11 and the electronic component 10 on the bonding tool 12. It is attached to the mounting machine body (not shown) at an angle that allows irradiation.

  In this mounting machine, as shown in the drawing, after the substrate 9 is placed on the stage 11 and the electronic component 10 is attracted to the bonding tool 12 and aligned with each other, the substrate side light source 13 and the electronic component side light source 14 respectively. While irradiating ultraviolet rays (or electron beam or atmospheric plasma) and lowering the bonding tool 12, the electronic component 10 is mounted on the substrate 9 while removing the protective film on the surface of the substrate 9 and the electronic component 10.

At this time, the protective film is removed by ultraviolet rays. The protective film is irradiated with ultraviolet rays from the substrate-side light source 13 and the electronic component-side light source 14 as ultraviolet ray generators, so that the chemical bonds of the protective film are broken by photon energy. The protective film in this state and the excited oxygen atoms generated by the ultraviolet rays cause a chemical reaction, and the protective film containing C, H, F, and O as components is decomposed and removed into CO ₂ , H ₂ O, F _{2, and the} like. The Similarly, when atmospheric plasma is used, excited oxygen atoms generated by atmospheric plasma generated by the atmospheric plasma generator chemically react with a protective film containing C, H, F, and O as components, and the protective film is CO ₂ , It is decomposed and removed into H ₂ O, F _{2 and the} like. Even in the case of using an electron beam, the protective film containing C, H, F, and O as components is removed by being decomposed into CO ₂ , H ₂ O, F _{2, and the} like by the electron beam generated by the electron beam generator.

  In this way, the step of removing the protective film from the electronic component 10 and the substrate 9 using ultraviolet rays, electron beams or atmospheric plasma generated by the substrate-side generation source 13 and the electronic component-side generation source 14, and the electronic component 10 to the substrate 9 By simultaneously performing the process of mounting on the substrate 9 and the surface of the electronic component 10 from which the protective film has been removed, the substrate electrode 9a and the electronic component electrode 10a are bonded in a clean state without being exposed to the atmosphere. Can be made. Therefore, a favorable joining state can be obtained as compared with the conventional method.

In the above-described embodiment, 7 mW / mm ² is used as a high-frequency output for plasma cleaning of the substrate 9 and the electronic component 10. However, in the plasma processing step, the electrode surfaces of the substrate 9 and the electronic component 10 are etched by several nm. There is no particular limitation on the output.

Although Ar gas is used as the cleaning gas, the same cleaning effect can be obtained by physical cleaning using an inert gas such as N ₂ gas or Kr gas. The gas flow rate is not particularly limited. It is possible to perform more effective cleaning by selecting an appropriate gas type according to the expected type of contaminant. For example, by including O ₂ gas in the cleaning gas, only physical cleaning can be performed. And contaminants can be removed by chemical cleaning. Although the pressure inside the chamber 1 is 10 Pa, it is possible to obtain the same cleaning effect under a pressure of 0.1 Pa to 100 Pa.

Although CHF ₃ gas was used as a reaction gas for the protective film, molecules containing fluorocarbon or hydrocarbon in the main chain and chemically or physically adsorbed on the uppermost layer of the substrate 9 or the electronic component 10 (of the protective film) Any structure can be used without particular limitation, and the same effect can be obtained.

RF plasma power when the protective film formation was set to 4 mW / mm ^2, it is preferably in the range of 12 mW / mm ² from 7 mW / mm ^2, enters the etched region in the output in excess of 12 mW / mm ^2, to generate a protective film Is difficult.

  Although the pressure in the chamber at the time of generating the protective film is 80 Pa, a similar protective film can be generated if the pressure is in the range of 50 Pa to 120 Pa. The flow rate of the reaction gas is not particularly limited.

  The thickness of the protective film is ideal when it is easily removed in the re-cleaning step, and a film thickness of about several nanometers is ideal. If the film thickness is equal to or larger than the monomolecular layer, it can function as a protective film. . In consideration of the protective film removal step, the thickness can be used as long as the film thickness is 1 μm or less.

The flowchart which shows the flow of the component mounting method in one Embodiment of this invention. 1 is a schematic cross-sectional view of a plasma processing apparatus constituting a component mounting apparatus that performs the component mounting method shown in FIG. FIG. 1 is a partially enlarged view of a mounting machine constituting a component mounting apparatus that performs the component mounting method shown in FIG. A flowchart showing the flow of a conventional component mounting method Schematic cross-sectional view of a conventional optical cleaning device applicable to component mounting

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 3 Lower electrode 4 Openable / closable lid 5 Exhaust duct 6, 7 Gas supply nozzle 8 High frequency power supply 9 Substrate 10 Electronic component 11 Stage 12 Bonding tool 13 Substrate side light source 14 Electronic component side light source

Claims (3)

Plasma cleaning the substrate and electronic components in a vacuum chamber;
Forming a protective film on the surface of the plasma-cleaned substrate and electronic component without opening the vacuum chamber to the atmosphere;
Irradiating the substrate on which the protective film is formed and the electronic component with ultraviolet rays, an electron beam or atmospheric plasma, and removing the protective film;
And a step of mounting an electronic component on the substrate from which the protective film has been removed. A plasma of an etching gas for cleaning the surface of the processing object and a protective film on the surface of the processing object in the vacuum chamber in which the processing object that is at least one of the substrate and the electronic component is installed. A plasma processing apparatus having plasma generating means for sequentially generating plasma of reactive gas to be formed;
A component mounting apparatus comprising: an irradiating unit configured to irradiate ultraviolet rays, an electron beam, or atmospheric plasma capable of removing the protective film; and a mounting device for mounting and mounting the substrate on which the protective film is formed and the electronic component.   The component mounting apparatus according to claim 2, wherein the mounting machine is a flip chip mounting machine.

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