JPH04208595A - Defoaming method for interior of small-diameter hole of printed circuit board - Google Patents

Abstract

PURPOSE:To provide excellent permeability and to scarcely generate refoaming by dipping a printed circuit board in defoaming solution of mixture of low surface tension agent having permeability to the inner wall of a small-diameter hole and hydrophilic imparting agent having hydrophilic properties, and defoaming by vibration, etc. CONSTITUTION:A printed circuit board 3 is dipped in defoaming solution 2 of mixture of low surface tension agent having permeability to the inner wall of a small-diameter hole 4 and hydrophilic imparting agent for holding hydrophilic properties at the wall, and defoamed by forcible means such as vibration, etc. In this case, bubbles 6 in the hole 4 are extracted by effects of the tension agent and the forcible vibration of a vibrator 5, and hydrophilic properties are imparted to the hole 4 by the effect of the imparting agent contained in the solution 2. Thus, liquid holding properties are imparted, and refoaming is eliminated.

Description

[Detailed description of the invention]

[00011

[Industrial Field of Application] The present invention relates to a method for defoaming inside small-diameter holes in a plating process for printed wiring boards. [0002] In recent years, as the circuit density of printed wiring boards has become higher, the diameter of the via holes formed in printed wiring boards has become smaller and smaller. When the diameter of the pier hole is reduced, air bubbles tend to remain in the pier hole during the plating process, and the formation of a plating film is likely to be inhibited. Therefore, in order to eliminate air bubbles in the peer holes in the plating solution, the generation of air bubbles is suppressed by holding the printed wiring board at an angle, applying vibration, using a low surface tension liquid, or a combination of these. was. [0003]

[Problems to be Solved by the Invention] According to the above-described conventional means for eliminating air bubbles in the pier hole, while the printed wiring board is being conveyed from one plating tank to the next plating tank, air bubbles inside the pier hole may be removed due to the influence of mechanical vibrations, etc. The problem was that the liquid was drained out and air bubbles were generated inside the pier hole again. The present invention was made in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide a defoaming method that has good permeability to the inner wall of a small-diameter hole in a printed wiring board and is less likely to generate bubbles again. [0004]

[Means for Solving the Problems] A low surface tension agent that has permeability to the inner wall of the small diameter hole 4 of the printed wiring board 3, and a hydrophilicity imparting agent that maintains hydrophilicity to the inner wall of the small diameter hole 4. The printed wiring board 3 is immersed in a defoaming solution 2 made of a mixture of the following, and is defoamed by force means such as vibration. [0005]

[Effect] Conventionally, defoaming can be done by applying vibration using a low surface tension liquid, but the reason why the liquid could not be retained in the small diameter pores during subsequent transfer between species is because the hydrophilicity at the time of degassing This is because it was not given. FIG. 1 is a diagram explaining the principle of the present invention, and FIG. 1(A) shows a cross-sectional view of a small diameter hole in a printed wiring board being immersed in a defoaming solution. In this case, the air bubbles 6 in the small-diameter holes 4 are removed due to the effect of the low surface tension agent contained in the defoaming liquid 2 and forced vibration by the vibrator 5, and the air bubbles 6 in the small-diameter holes 4 are removed due to the effect of the hydrophilicity imparting agent contained in the defoaming liquid 2. Hydrophilic properties are provided within the pores 4. Next, Figure 1(B) shows a cross-sectional view of a small diameter hole in a printed wiring board that has been lifted out of the defoaming solution. Since the defoaming liquid 2 is held in the small diameter hole 4, even if it is transferred to the next tank in this state, the defoaming liquid 2 in the small diameter hole 4 will not come out, and no re-foaming will occur. [0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the drawings. The defoaming solution used in the present invention is composed of a mixed solution of a low surface tension agent and a hydrophilicity imparting agent, and specifically, alcohol can be used as the low surface tension agent, and monoethanolamine or the like can be used as the hydrophilicity imparting agent. - As an example, the concentration of isopropyl alcohol (hereinafter abbreviated as IPA) is 30% and 0% as the alcohol of the low surface tension agent, and the commercial product name Conditioner 1175 (mono) manufactured by Sible Far East Co., Ltd. is used as the hydrophilicity imparting agent. Ethanolamine concentration 40
% and triethanolamine concentration of 10%. The defoaming properties and liquid retention properties of each defoaming solution were measured for combinations of defoaming solutions whose mixing ratios were changed as shown in sample numbers 1 to 12 in Table 1. [0007] First, the defoaming property was measured by drilling 30 holes of 0.35φ in a transparent vinyl chloride board with a thickness of 3M, and gently immersing the transparent vinyl chloride board in a defoaming solution. The number X of holes in which the defoaming liquid is contained (defoamed holes) among the total number of 30 holes of 0.35φ in the test tube was counted by observation, and the results are shown in the defoaming number X column. However, it has been confirmed that all holes that have not been defoamed here are defoamed in the vibration process of the vibrator 5 shown in FIG. [00081 Next, the liquid retention measurement results were as follows:
Thirty holes of 0.35Φ were made in a transparent vinyl chloride board of size 1.3m, and after immersing it in a defoaming solution, all the holes were defoamed by the vibration process of the vibrator 5, and the board was pulled out of the defoaming solution. After being left in the air for 60 seconds and 180 seconds, the number Y of holes holding liquid was counted by observation, and the results are shown in the columns Y6o and Ytso for the number of liquid holding holes in Table 1. Note that the temperature at the time of measurement was 19 degrees Celsius, and the humidity was 35%. [0009]

[Table 1] [00101 As can be seen from the results of this Table 1, 117
In the case of sample number 1 in which 5 liquids are not mixed, the number of liquids retained after 60 seconds is 29, but the number of liquids retained after 180 seconds is 1.
The number rapidly decreased to 4, indicating a high possibility of re-foaming. FIG. 2 shows measurement data of liquid retention according to the present invention, and from the results of Table 1, the horizontal axis shows the sample number (i.e., IP
Mixing ratio classification of A and conditioner 1175) is taken,
The vertical axis shows the liquid retention rate in % after standing for 180 seconds. As you can see from this figure, 30% concentration of IP
Conditioner 1175 with a concentration of 0.3 to 2.5% to A
It has been found that liquid retention can be maintained for 180 seconds by adding . [00111] Furthermore, it is known that once hydrophilicity is imparted to the inner wall of the small diameter hole of a printed wiring board, the effect is maintained regardless of the subsequent cleaning process. Therefore, the printed wiring board imparted with liquid retention properties according to the present invention,
A normal plating film can be obtained without re-foaming in the subsequent plating process. [0012]

As is clear from the above description, according to the present invention, the plating solution completely enters the small-diameter holes in the plating process of printed wiring boards, and the reliability of the plating film inside the small-diameter holes is improved. It has the effect of contributing to sexual improvement.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a diagram showing measurement data of liquid retention according to the present invention.

[Explanation of symbols]

1 tank 2 Defoaming liquid 3 Printed wiring board 4 Small diameter hole 5 Vibrator

Claims (1)

[Claims] 1. A low surface tension agent that is permeable to the inner wall of the small diameter hole (4) of the printed wiring board (3), and a hydrophilic agent that maintains hydrophilicity to the inner wall of the small diameter hole (4). Defoaming in a small diameter hole of a printed wiring board, characterized in that the printed wiring board (3) is immersed in a defoaming liquid (2) mixed with an imparting agent and defoamed by forced means such as vibration. Method.