JPH03140475A - Method for introducing liquid into micropore - Google Patents

Abstract

PURPOSE:To introduce liquid into micropores in a short time by introducing a boiling matter soluble in a liquid into micropores in a base material and bringing the micropores into contact with a nonboiling liquid while maintaining the state where the above boiling matter is kept being introduced. CONSTITUTION:A liquid is introduced into micropores in a base material 1. For this purpose, the base material 1 is placed into a vessel 3, and a boiling vapor 6 and/or boiling liquid soluble in a liquid is introduced into the micropores in the base material 1. Then, while keeping the state of introduction, the micropores 2 are brought into contact with a nonboiling liquid 9. At this time, water vapor is used as the above boiling vapor, and water or a solution in which water is used as a solvent are used as the above boiling liquid and the above nonboiling liquid. By this method, the cost of equipment can be reduced and economized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for introducing a liquid into microholes formed in a substrate. INDUSTRIAL APPLICABILITY The present invention is effectively applied, for example, to introducing a liquid for pretreatment when performing plating treatment on the inner wall surface of a microhole on which a conductive film is formed to establish conduction between both surfaces of a printed wiring board. .

[Prior art and problems to be solved by the invention] Usually,
When cleaning, plating, etching, or the like a wet method using an aqueous solution on a substrate having micropores, it is necessary to bring the entire surface of the substrate into contact with the liquid. However, although the liquid easily comes into contact with the outer surface of the base material, it is difficult for the liquid to enter the inside of the micropores, and the liquid hardly comes into contact with the inner wall surfaces of the holes.

FIG. 3 is a schematic cross-sectional view for explaining the situation. As shown in FIG. 3(a), a base material 1 having microholes 2
is placed in a gas 7 such as air, and then the (
As shown in b), when the base material is immersed in the liquid 5, the gas 7 remains as bubbles in the microholes, thereby creating a portion of the inner wall surface of the hole that the liquid 5 does not come into contact with.

In particular, when forming a plating film on the inner wall surface of a hole such as in a printed wiring board, an appropriate aqueous solution is used to perform the degreasing process, catalyst treatment process, electroless plating process, electroplating process, and between each process. Since there are many processes such as a water washing process, the problem of gas remaining in the holes can cause serious defects in the printed wiring board.

In recent years, as the wiring density of printed wiring boards has increased, the hole diameter has gradually become smaller (with a hole diameter of 0.1 mm).
There is a growing demand for something of the order of φ. Therefore, as a method of introducing liquid into such a microhole, for example, Japanese Patent Application Laid-Open No. 62-154797 and Japanese Patent Application Laid-open No. 62-154
A proposal has been made in Publication No.-190794.

However, the proposal in JP-A No. 62-154797 uses a vibrating defoaming device to vibrate the base material to drive out the air in the holes and introduce liquid; Although the air in the hole can be easily removed, it is difficult to expel the air in the center of the hole and introduce the liquid, and there is a problem that the reliability is still insufficient.

In addition, the proposal of the above-mentioned Japanese Patent Application Laid-open No. 1987-190794 is as follows:
This method reduces the pressure in the vacuum degassing tank to remove the air inside the hole, and then introduces the flux solution into the hole. This method is extremely reliable if it can be completely evacuated, but the entire tank needs to be sealed, and the equipment needs to be strong and have a structure that prevents air leaks. However, there is the problem of high equipment costs.Also, with ordinary vacuum pumps, when a gas containing moisture is sucked in, the circulating oil inside the pump is affected by moisture and decomposes, so liquids are not used. In order to avoid this, it is common to use water pumps to reduce the pressure, but water pumps have low pressure reduction capabilities and take a long time to obtain a vacuum. The problem is that productivity is low.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method that does not have the above-mentioned problems of the prior art and can efficiently introduce a liquid into a microhole using simple equipment.

[Means for Solving the Problems] According to the present invention, in order to achieve the above object, in a method of introducing a liquid into micropores of a base material, boiling vapor and/or boiling liquid soluble in the liquid is introduced. Provided is a method for introducing a liquid into a microhole, the method comprising introducing a liquid into a microhole of a base material, and bringing the microhole into contact with a non-boiling liquid while maintaining the introduced state.

In the present invention, the boiling vapor may be water vapor, and both the boiling liquid and the non-boiling liquid may be water or a solution using water as a solvent.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view for explaining an example of the method of the present invention.

In FIG. 1, (a) shows a base material 1 in the air, and a through microhole 2 is formed in the base material.

In FIG. 1, (b) shows the state in which the base material 1 is accommodated in the processing container 3. As shown in FIG. The container 3 is covered with a lid 4 having a communication port with the outside. The container 3 has two parts, the left part containing a first liquid 5 which is heated by heating means 8 to a boiling state.

The space inside the container 3 is filled with vapor 6 of the first liquid 5, and the substrate 1 put into the container 3 from the outside is first placed in the vapor 6 (inside the container in Fig. 1). (See left).

In boiling steam 6, the vapor pressure is the same as atmospheric pressure, so
The atmospheric pressure inside the microhole 2 becomes higher than the atmospheric pressure by the partial pressure of the air inside the hole. Therefore, the air within the hole cannot remain and is expelled from the microscopic hole 2 into the large bowl and further out of the container 3. As a result, the entire inside of the microhole 2 is replaced with boiling steam 6.

Next, as described above, the air inside the hole is purged and boiled steam is 6
The base material 1 in a state where it has been replaced with
Without letting it out, it is immersed in the second liquid 9 and the microhole 2 is brought into contact with the liquid 9 (see the right side inside the container in Figure 1).
. The second liquid 9 is not boiling and has boiling vapor 6
and soluble.

The vapor 6 in the microhole 2 liquefies and dissolves into the liquid 9. As a result, the inside of the microhole 2 is filled with the liquid 9, and the liquid 9 can be completely introduced into the hole.

Figure 2 schematically shows the above process, and (a
) shows the state in which the substrate 1 is in the air 7, (b) shows the state in which the air 7 in the micropores 2 is expelled and replaced by boiling steam 6, and (c) shows the state in which the substrate 1 is immersed in the liquid 9. (d) shows the state immediately after the vapor 6 has liquefied and the liquid 9 has flowed into the microhole 2.
Indicates the state introduced within.

Although the first liquid 5 and the second liquid 9 are not particularly limited, for example, water and its solution, organic solvents such as alcohol and ether, etc. can be used.

The first liquid 5 and the second liquid 9 may be the same or different as long as they are soluble in each other.

Water or an aqueous solution using water as a solvent can be advantageously used because it is inexpensive, easy to handle, and has a low boiling point. For example, water can be used as the first liquid 5 and a degreasing aqueous solution can be used as the second liquid 9.

In addition, when performing treatment using a liquid, it is necessary to immerse it in various aqueous solutions one after another (this is done by boat fishing, and if the liquid is completely introduced into the micropores at the first stage of treatment, Since the inner wall surface of the microhole is in a wet state, during the process (b) in Figure 3.
Therefore, the present invention is most effective when applied at the initial stage of treatment. However, it is necessary to completely introduce the liquid at each treatment step. In such cases, the present invention can be adopted for each processing step.In this way, when performing each processing step, the present invention is extremely simple compared to the conventional method using vacuum depressurization, especially in terms of equipment. Become something.

The liquid 5 can be introduced into the microhole 2 by immersing the liquid 5 until the liquid 5 is completely immersed, and then stopping the heating and cooling the liquid 5 by the cooling means 10. In this way, it is a completely non-sealable container,
The first liquid and the second liquid are the same in the same container,
It is possible to achieve the objectives of the invention.

In the above example, a case was described in which the substitution was performed in boiling steam, but the present invention also allows the embodiments shown in FIGS. 4 and 5 to be possible. In these figures, the first
Similar members in the figures are given the same reference numerals.

In the example shown in FIG. 4, by immersing the base material 1 in the boiling liquid 5, it is possible to expel the gas in the micropores 2 and replace it with a mixture of boiling vapor and boiling liquid. be.

In the example shown in FIG. 5, the container 3 does not have a lid, and heating means 8 and cooling means 10 are provided inside the container. in this case,
The liquid 5 is brought to a boiling state by the heating means 8, and the base material 1 is put into it, and the replacement is completed. The same applies to the case.

Furthermore, in the method of the present invention, conventional methods can also be used in combination. In other words, by adding a vibration degassing device, rapid replacement is possible, and if a vacuum depressurization method is also used,
Reduced pressure lowers the boiling point of a liquid, and for example, water can be boiled at temperatures below 100°C, so 100°C
It can also be applied to aqueous solutions whose temperature cannot be raised to a certain level.

Hereinafter, specific examples using the above method of the present invention will be described.

'! JiJLL: 0.6 mm thick glass epoxy double-sided copper clad plate (manufactured by Toshiba Chemical Corporation: TLC-W-551) with a drill of 0.1 mm.
A large number of holes of mmφ were made and used as a sample base material.

Tap water was poured into the left side of the container 3 shown in FIG. 1(b) and brought to a boil by the heater 8. A degreasing solution (manufactured by Yuken Kogyo Co., Ltd.: Pakuna 30 g/I2) was placed in the right side of the container, and the temperature was adjusted to 80°C. The substrate was suspended in boiling steam in the container 3, left for 10 minutes, and then removed from the container 3 (the substrate was placed in the degreasing liquid and immersed for 10 minutes. After performing electroless copper plating, a copper plating film was formed by electroplating until the maximum thickness of Omukai reached 20 μm.Next, this base material was cut into chips for each microhole, and The conductor resistance of the hole was measured.

School Yutaka Uni A sample base material was obtained in the same manner as in Example 1.

The base material was placed in an empty beaker, and the pressure was reduced using an aspirator using a Pelger for 10 minutes.
The pressure was reduced to mHg. Next, tap water was introduced into the beaker while maintaining the reduced pressure. The base material was taken out and immersed in the degreasing solution at 80° C. in the same manner as in Example 1, and the same treatments and measurements as in Example 1 were performed.

A base material similar to Mitate Uni Example 1 was prepared, and the left side of the container shown in Figure 4 was filled with tap water and kept in a boiling state, and the right side was filled with the above degreasing liquid at 80°C. . The base material was immersed in boiling water for 10 minutes, and without being taken out from the container 3 (the base material was placed in a degreasing liquid and immersed for 10 minutes. The base material was taken out and the same procedure as in Example 1 was carried out.

Mitate 1: The same base material as in Example 1 was prepared, and the container shown in FIG. 5 was filled with tap water and kept in a boiling state. After immersing the substrate in this boiling water for 10 minutes, the heating was stopped, and tap water at about 20°C was passed through a copper spiral tube as a cooling means.
It was cooled to about 20°C. Remove the base material from the container and
After being immersed in the degreasing solution at a temperature of 10° C. for 10 minutes, the same procedure as in Example 1 was carried out.

Mitate! A: A beaker was filled with the above degreasing solution and maintained at 80°C. The same base material as in Example 1 was immersed in a beaker, the pressure was reduced in the same manner as in Comparative Example 1, and the degreasing solution was brought to a boiling state at 350 mmHg and held for 5 minutes, then returned to atmospheric pressure and the base material was taken out. . Hereinafter, the same procedure as in Example 1 was carried out.

The results of measuring the conductor resistance of the microholes in the above Examples and Comparative Examples are shown in Table 1 below. In each example or comparative example, the number of chips measured was 100, and 50
A value of mΩ or more was determined to be defective, and the defective rate was calculated.

From the results shown in Table 1, as in Comparative Example 1, with the conventional depressurization method, sufficient vacuum could not be obtained in 10 minutes and the defective rate was 4%, but in the example of the present invention, the defective rate was lower. are all 0%,
It was found to be good.

[Effects of the Invention] As explained above, according to the present invention, the following effects can be obtained.

1) It is possible to introduce liquid into microholes in a short time, and it is more efficient than the conventional vacuum depressurization method.

2) Since sufficient effects can be obtained with simple equipment, equipment costs are low and it is economical.

3) It can be combined with conventional methods and has a wide range of applications.

[Brief explanation of the drawing]

FIG. 1, FIG. 4, and FIG. 5 are all schematic cross-sectional views for explaining the method of the present invention. FIG. 2 is a schematic sectional view showing the process of the present invention. FIG. 3 is a schematic cross-sectional view showing how gas remains in the microhole. DESCRIPTION OF SYMBOLS 1... Base material, 3... Container, 5.9... Liquid, 7... Gas, 10... Cooling means.

Claims (2)

[Claims] (1) In a method of introducing a liquid into microholes in a base material,
Introducing boiling vapor and/or boiling liquid soluble in the liquid into the microholes of the base material, and bringing the microholes into contact with a non-boiling liquid while maintaining the introduction state, the liquid in the microholes. How to introduce. (2) The method for introducing a liquid into a microhole according to claim 1, wherein the boiling vapor is water vapor, and the boiling liquid and the non-boiling liquid are both water or a solution using water as a solvent.