JP2015085267A - Desmear treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a desmear treatment device capable of performing desmear treatment with high treatment efficiency.SOLUTION: A desmear treatment device includes: a treatment chamber in which an object to be treated is disposed; a light source irradiating the object to be treated with vacuum ultraviolet ray via a light transmission window; active species source supply means for supplying an active species source to be activated by the vacuum ultraviolet ray from the light source to the inside of the treatment chamber; and decompression means for decompressing the inside of the treatment chamber. The active species source is configured to be supplied in a state that the inside of the treatment chamber is kept in the decompression state. In the desmear treatment device, it is preferable that the decompression means has a function to decompress the inside of the treatment chamber to 70kPa or less, and it is preferable that the active species source supply means supplies treatment gas having oxygen concentration of 90% or more as the active species source.

Description

  The present invention relates to a desmear processing apparatus used for desmear processing in a printed circuit board manufacturing process, for example.

  Currently, for example, a dry cleaning method using ultraviolet rays is known as a method for performing a desmear (smear removal) process in a printed circuit board manufacturing process. In particular, a method using active oxygen such as ozone generated by vacuum ultraviolet rays radiated from an excimer lamp is suitably used because a predetermined treatment can be performed more efficiently and in a short time.

  For example, Japanese Patent Application Laid-Open No. 8-180757 of Patent Document 1 describes that in dry desmear processing, organic substances are decomposed and removed using active species (active oxygen atoms) generated by decomposition from ozone. Yes. Further, it is described that it is preferable to use ozone treatment utilizing the action of ozone and active species and ultraviolet irradiation treatment in combination for decomposition and removal of organic substances.

JP-A-8-180757

  Thus, ozone used in desmear treatment is usually generated by irradiating vacuum ultraviolet rays to a treatment gas containing a predetermined concentration of oxygen. It is required to feed up. On the other hand, vacuum ultraviolet rays from a light source are absorbed by oxygen, and generated active species are deactivated in a very short time. For this reason, some of the generated active species contribute to the desmear treatment, while others may be deactivated without contributing to the desmear treatment, and the processing efficiency of the desmear treatment is not high. There was a problem.

  The present invention has been made based on the above circumstances, and an object of the present invention is to provide a desmear processing apparatus capable of performing desmear processing with high processing efficiency.

The desmear processing apparatus of the present invention is activated by a processing chamber in which an object to be processed is disposed, a light source that irradiates the processing object with vacuum ultraviolet rays through a light transmission window, and vacuum ultraviolet rays from the light source in the processing chamber. Active species source supply means for supplying the activated species source to be converted,
The processing chamber is provided with a decompression means for decompressing the inside of the processing chamber,
The active species source is supplied in a state where the processing chamber is maintained in a reduced pressure state.

In the desmear treatment apparatus of the present invention, it is preferable that the decompression unit has a function of decompressing the processing chamber to 70 kPa or less.
The activated species source supply means preferably supplies a processing gas having an oxygen concentration of 90% or more as an activated species source.

  According to the desmear treatment apparatus of the present invention, the active species generated by irradiating the active species source with the vacuum ultraviolet rays from the light source through the light transmission window in a state where the processing chamber is maintained in a reduced pressure state. Since the mean free process becomes longer, the amount of active species contributing to the treatment of the object to be treated can be increased, and thus the treatment efficiency can be improved.

  Further, since the active species can be reliably contributed to the processing of the object to be processed by increasing the mean free path of the active species, for example, a processing gas having an oxygen concentration of 90% or more is supplied as the active species source. As a result, the generation efficiency of active species is improved, and the processing efficiency can be further improved.

It is explanatory drawing which shows the outline of a structure in an example of the desmear processing apparatus of this invention.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is an explanatory diagram showing an outline of a configuration in an example of a desmear processing apparatus of the present invention.
The desmear treatment apparatus includes a housing 10 in which a mounting table 30 on which a flat workpiece (for example, a wiring board material such as a multilayer printed board) W is placed, and an interior of the housing 10. And a light source disposed on the mounting table 30 through a light transmission window.

  For example, the light transmission window is formed with respect to the housing 10 in a state in which the plate-like window member 20 made of synthetic quartz glass that transmits vacuum ultraviolet rays extends in parallel with the flat workpiece mounting surface 31 of the mounting table 30. Therefore, the internal space of the housing 10 is partitioned vertically by the window member 20. And the lower space part in which the mounting base 30 was provided is made into the process chamber 15, and the upper space part is made into the light source arrangement room (lamp house) 11 by which a light source is arrange | positioned.

  In the light source arrangement chamber 11, a light source that irradiates the workpiece W with vacuum ultraviolet rays through the window member 20 is provided. The light source in this example is configured such that a plurality of ultraviolet lamps 25 each radiating vacuum ultraviolet rays are arranged at positions spaced apart from each other with their lamp central axes positioned in the same horizontal plane. In FIG. 1, for convenience, three ultraviolet lamps are shown. Examples of such an ultraviolet lamp 25 include a low-pressure mercury lamp that emits ultraviolet light having a peak at a wavelength of 185 nm, a deuterium lamp that emits ultraviolet light having a wavelength of 180 to 370 nm, and a xenon excimer that emits vacuum ultraviolet light having a center wavelength of 172 nm. A lamp can be used. Among these, it is preferable to use a xenon excimer lamp because the intensity of vacuum ultraviolet rays is high and active species can be generated efficiently.

  Further, an inert gas introduction part 12a and an inert gas discharge part 12b for an inert gas such as nitrogen gas are provided on the side wall of the casing 10 that defines the light source arrangement chamber 11, and the inert gas introduction is performed. A nitrogen gas source (not shown) is connected to the part 12a. When processing the workpiece W, the atmosphere in the light source arrangement chamber 11 is replaced with an inert gas (for example, nitrogen gas) in order to prevent vacuum ultraviolet rays from the ultraviolet lamp 25 from being absorbed by oxygen. The

The desmear treatment apparatus includes active species source supply means for supplying an activated species source activated by vacuum ultraviolet rays from the ultraviolet lamp 25 into the processing chamber 15.
The active species source supply means preferably supplies a processing gas having an oxygen concentration of 90% or more as an active species source. When the oxygen concentration in the processing gas is 90% or more, the amount of ozone and active species (oxygen radicals) generated by vacuum ultraviolet rays can be increased, and the intended processing can be performed reliably.
In this example, an oxygen gas supply source 35 is connected to an active species source introduction portion 16 formed on the side wall of the housing 10 defining the processing chamber 15 via a conduit 36 and branches from the conduit 36. The ozone generation means 38 is connected via the branch pipe 39 thus supplied, and therefore oxygen gas or a mixed gas obtained by mixing ozone with oxygen gas is supplied into the processing chamber 15 as an active species source.
As the ozone generating means 38, for example, an ozonizer or an ultraviolet lamp device that generates ozone using oxygen gas as a raw material can be used.

Moreover, in the desmear processing apparatus of this invention, it is preferable that the mounting table 30 is provided with a heating mechanism (not shown) for heating the workpiece W. According to such a structure, since the effect | action by ozone and an active species can be accelerated | stimulated with the temperature of the to-be-processed surface Wa of the to-be-processed object W rising, a process can be performed efficiently.
The heating condition by the heating mechanism is preferably such that the temperature of the surface Wa of the workpiece W is, for example, 80 ° C. or higher and 340 ° C. or lower, more preferably 80 ° C. or higher and 200 ° C. or lower. It is a condition.

Thus, in the above desmear processing apparatus, there is provided a decompression means for decompressing the inside of the processing chamber 15 to a predetermined decompressed state when the workpiece W is processed.
The pressure in the processing chamber 15 at the time of processing the workpiece W is preferably, for example, 70 kPa (gauge pressure −30 kPa) or less, more preferably 10 to 70 kPa (gauge pressure −90 to −30 kPa). More preferably, the pressure is 25 to 70 kPa (gauge pressure is −75 to 30 kPa). By setting the pressure in the processing chamber 15 to 70 kPa or less, the mean free path of the generated active species becomes longer, and desmear processing is performed under atmospheric pressure as shown in the results of the experimental example described later. The processing efficiency can be improved as compared with the case. On the other hand, when the pressure in the processing chamber 15 is set to be smaller than 10 kPa, the pressure applied to the window member 20 is increased. Therefore, the thickness of the window member 20 is increased so as to obtain sufficient resistance against the load. For example, 20 mm or more. When the thickness of the window member 20 is increased, the amount of vacuum ultraviolet light from the ultraviolet lamp 25 absorbed by the window member 20 increases, so that the amount of vacuum ultraviolet light used for desmear processing is reduced and the processing efficiency is lowered. Resulting in.
In this example, a gas discharge portion 17 for discharging the gas in the processing chamber 15 (shown by a hatched arrow for convenience) is formed on the lower wall of the casing 10 that defines the processing chamber 15. The gas discharge unit 17 is connected to a pressure reducing means such as a vacuum pump 40 through a conduit 41. Here, it is preferable to use a decompression means having a function of decompressing the inside of the processing chamber 15 to 70 kPa or less.

  In the above, the size d of the vertical distance (gap) between the processing surface Wa of the workpiece W and the light emitting surface 21 of the window member 20 is, for example, 1 mm or more, preferably 1 to 5 mm. The The size d of the gap varies depending on the decompressed state in the processing chamber 15 during processing of the workpiece W, but when the pressure in the processing chamber 15 is set to 10 kPa, for example, the size of the gap (maximum value). ) D can be 5 mm. By having such a configuration, it is possible to avoid scratching the processing surface Wa due to undesired contact between the processing surface Wa of the processing object W and the light emitting surface 21 of the window member 20. In addition, it is possible to prevent processing unevenness from occurring.

Hereinafter, a desmear processing method by the above desmear processing apparatus will be described.
In this desmear processing apparatus, in a state where the workpiece W is placed on the workpiece placement surface 31 of the placement table 30, and the treatment object W is heated by the heating means provided on the placement table 30, The inside of the processing chamber 15 is depressurized by the vacuum pump 40. Then, in a state where the inside of the processing chamber 15 is maintained in a predetermined reduced pressure state, oxygen gas is supplied from the oxygen gas supply source 35 and ozone generated by the ozone generating means 38 is mixed with the oxygen gas. Gas is supplied into the processing chamber 15 as an active species source. On the other hand, an inert gas (for example, nitrogen gas) is supplied (purged) into the light source arrangement chamber 11 to replace the inside of the light source arrangement chamber 11 with an inert gas atmosphere. When each ultraviolet lamp 25 is turned on, vacuum ultraviolet rays radiated from each of the ultraviolet lamps 25 are applied to the surface Wa of the workpiece W through the window member 20. As a result, vacuum ultraviolet rays that reach the surface Wa of the workpiece W and ozone and active species (for example, oxygen radicals) generated by the vacuum ultraviolet rays are formed on the surface Wa of the workpiece W. Smear (organic resin) is decomposed and removed.
In the above, the illuminance of the ultraviolet rays applied to the workpiece W is, for example, 10 to 200 mW / cm ² . Moreover, although the ultraviolet irradiation time with respect to the to-be-processed object W is set suitably considering the illumination intensity of an ultraviolet-ray, the residual state of a smear, etc., it is 50 to 300 seconds, for example.

Thus, as described above, active species such as oxygen radicals generated by irradiation with vacuum ultraviolet rays have a very short life and can only exist, for example, about 10 ⁻⁸ sec. In the case where the process is performed, there are those that disappear without contributing to the process of the workpiece W. However, since the inside of the processing chamber 15 is maintained in a predetermined reduced pressure state, the average free process of the active species becomes longer according to the desmear processing apparatus configured as described above. The amount of active species that contribute can be increased, the desired desmear treatment can be performed in a short time, and the treatment efficiency can be improved.
Moreover, since the active species can be reliably contributed to the processing of the workpiece W by increasing the mean free path of the active species, for example, a processing gas having an oxygen concentration of 90% or more is supplied as the active species source. As a result, the processing efficiency can be further improved. Moreover, since the size d of the gap between the surface Wa to be processed W and the light exit surface 21 of the window member 20 can be increased, the surface Wa to be processed and the window member 20 of the object W to be processed. It is possible to avoid the workpiece W from being damaged or broken due to undesired contact with the light emitting surface 21 and to reliably suppress or prevent the occurrence of processing unevenness.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made.
For example, the active species source is not limited to oxygen gas or a mixed gas in which ozone is mixed with oxygen gas, but is more suitable as long as it generates active species by irradiation with vacuum ultraviolet rays. You can use what is used for. For example, water vapor, air, carbon monoxide gas, carbon dioxide gas, and the like can be used. When water vapor is used, hydroxyl radicals (OH radicals) are generated in addition to oxygen radicals.
In addition, the light transmission window does not need to be formed by a plate-like window member that is airtightly fixed to the housing. For example, the synthetic quartz provided with the ultraviolet lamp inserted therein is used. You may be comprised with the tube member which consists of glass. In the thing of such a structure, what is necessary is just to be comprised so that an inert gas may be purged inside a pipe member.
Furthermore, it may be configured to be provided with a physical vibration processing means for applying physical vibration to the workpiece subjected to the ultraviolet irradiation treatment. As the physical vibration processing means, for example, an ultrasonic oscillator that applies ultrasonic vibration using water as a vibration medium can be used. With such a configuration, the desired desmear process can be more reliably performed.

  Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

With reference to the configuration shown in FIG. 1, a desmear processing apparatus according to the present invention having the following specifications was produced.
[Place (30)]
Dimensions: 520x610mm, thickness 50mm
Material: Aluminum [heating means]
Resistive heating heater [ultraviolet lamp (25)] operating under heating conditions where the temperature of the surface to be processed is 150 ° C.
Xenon excimer lamp with emission length of 830mm Number of UV lamps: 8 Input power: 500W
[Window member (20)]
Window member dimensions: 540 x 600 mm, thickness 5 mm
Material: Synthetic quartz glass Gap (d): 1 mm between the light emitting surface of the window member and the workpiece mounting surface of the mounting table
[Active species source supply means]
Active species source (processing gas): mixed gas in which ozone is mixed with oxygen gas and the oxygen concentration is 90% [inert gas supply means]
Inert gas: Nitrogen gas Inert gas supply: about 30 liters / min
[Processed object (W)]
A test wiring board material in which a through hole is formed in an insulating layer in a laminate in which an insulating layer is formed on a copper foil, and smear remains at the bottom of the through hole. Thickness of the copper foil: 100 μm
Insulating layer: Silica having an average particle size of 1.0 μm contained in an epoxy resin in a proportion of 40% by mass Insulating layer thickness: 100 μm
[Pressure reduction means]
A vacuum pump having a function of depressurizing the processing chamber to 70 kPa or less

<Example 1>
In a state where the pressure in the processing chamber (15) is reduced to 70 kPa by the vacuum pump (40), and the active species source is supplied at a supply rate of 10 liters / min while maintaining the processing chamber (15) in a reduced pressure state. Each ultraviolet lamp (25) was turned on under the condition that the illuminance of the light exit surface (21) of the window member (20) was 100 mW / cm ^2, and the desmear treatment of the test wiring board material (W) was performed.
In this desmear process, the ultraviolet irradiation time was changed stepwise from 50 seconds to 600 seconds. Then, the bottom of the through hole (surface to be processed) in the test wiring board material (W) for which the desmear treatment has been completed is observed with a scanning electron microscope, and the ultraviolet irradiation time when smear residue is no longer recognized for the first time is examined. It was. The results are shown in Table 1 below.

<Comparative Example 1>
In Example 1, except that the pressure in the processing chamber (15) was set to 100 kPa (atmospheric pressure), a desmear treatment of the test wiring board material (W) was performed under the same processing conditions as in Example 1, By the same method as in Example 1, the ultraviolet irradiation time when smear residue was not recognized for the first time was examined. The results are shown in Table 1 below.

  From the above results, it was confirmed that the processing can be performed in a short time by performing the desmear process while maintaining a reduced pressure in the processing chamber. The reason for this is that by maintaining the processing chamber in a reduced pressure state, the mean free path of oxygen radicals generated by irradiation with vacuum ultraviolet rays becomes longer, and the light emission surface of the window member and the surface of the test wiring board material This is presumably because the amount of oxygen radicals that contacted the smear and contributed to the decomposition increased even though the distance between and was set to be relatively large at 1 mm.

<Reference Example 1>
In Example 1, the test wiring board material (W) was used under the same processing conditions as in Example 1 except that the ultraviolet irradiation time was 300 sec and the pressure in the processing chamber (15) was changed according to Table 2 below. The desmear treatment was performed. Then, the light emitting surface (21) of the window member (20) and the mounting table (30) covered with the smear remaining in the test wiring board material (W) after the desmear treatment is completed are obtained. The maximum value (maximum gap) of the distance d between the workpiece surface (31) was examined. The results are shown in Table 2 below.

From the above results, it can be confirmed that the distance (ultraviolet irradiation distance) between the light emitting surface of the window member and the workpiece mounting surface of the mounting table can be set larger as the pressure in the processing chamber is lowered. It was done.
Therefore, for example, the desmear processing apparatus is set to the desired pressure by setting the pressure (depressurized state) in the processing chamber according to the distance between the light emitting surface of the window member and the workpiece mounting surface of the mounting table. While it is possible to reliably perform desmear processing, it is possible to reliably avoid scratching the processing surface due to undesired contact between the processing surface of the processing object and the light emitting surface of the window member. Will be able to.

DESCRIPTION OF SYMBOLS 10 Case 11 Light source arrangement room 12a Inert gas introduction part 12b Inert gas discharge part 15 Processing chamber 16 Active species source introduction part 17 Gas discharge part 20 Window member 21 Light emission surface 25 Ultraviolet lamp 30 Mounting stand 31 Workpiece mounting Placement surface W Processed object Wa Processed surface 35 Oxygen gas supply source 36 Conduit 38 Ozone generating means 39 Branch pipe 40 Vacuum pump 41 Conduit

Claims (3)

A processing chamber in which an object to be processed is disposed, a light source that irradiates the processing object with vacuum ultraviolet rays through a light transmission window, and an active species source that is activated by the vacuum ultraviolet rays from the light source are supplied into the processing chamber. Active species source supply means
The processing chamber is provided with a decompression means for decompressing the inside of the processing chamber,
The desmear processing apparatus, wherein the active species source is supplied in a state where the processing chamber is maintained in a reduced pressure state.   The desmear processing apparatus according to claim 1, wherein the decompression unit has a function of decompressing the processing chamber to 70 kPa or less.   2. The desmear treatment apparatus according to claim 1, wherein the active species source supply means supplies a processing gas having an oxygen concentration of 90% or more as an active species source.

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