JPH0470550A - Evaluation method for small-diameter hole degassing properties of printed circuit boards - Google Patents

Abstract

PURPOSE:To enhance the reliability of the quality of a product by carrying out the simulation of defoaming operation before performing actual manufacturing and quantifying the defoamed states under respective operating conditions to measure the same to calculate the optimum operating condition. CONSTITUTION:A definite solution 2 to be tested is received in an experimental tank 1 at least a part of which is made transparent. A large number of small holes 4 having a diameter same to that of the small size via-holes of a printed circuit board ready to manufacture are formed on a transparent plate 3 having the same thickness as the printed circuit board and this plate 3 is dipped in the solution 3. Thereafter, defoaming operation ready to be carried out in an actual manufacturing process is performed so that the plate 3 is allowed to stand as it is or inclined or struck to be vibrated. Then, the end surface of the plate 3 is seen through from the outside of the experimental tank 1 to observe the small size holes 4 by an eye 6 and a defoaming ratio (number of defoamed holes/total number of holes) is calculated to quantify a defoamed state. By this method, simulation is performed and the optimum operating condition imparting the highest defoaming ratio is calculated.

Description

[Detailed Description of the Invention] [Summary] Regarding the evaluation method for the degassing performance of small diameter holes in printed circuit boards, the operating conditions are simulated before the production of printed circuit boards to quantitatively evaluate the degassing performance of small diameter holes, and the optimization of the operation is evaluated. In order to be able to investigate the conditions, an experimental tank made at least partially transparent was filled with a test solution, and a transparent plate with a large number of small pores having a predetermined pore diameter was immersed in the test solution. After performing a predetermined defoaming operation, the transparent plate was observed from outside the experimental tank and the proportion of small diameter holes from which air bubbles had escaped was measured.

[Industrial application field]

The present invention relates to a method for evaluating the degassing properties of small diameter holes in printed circuit boards.

[Traditional technique]

In recent years, as the circuit density of printed circuit boards has increased, the diameter of peer holes formed in printed circuit 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, for example, and the formation of the plating film is likely to be inhibited. Therefore, in order to eliminate air bubbles inside the peer holes in the plating solution, the printed circuit board is tilted or vibrated, or a low surface tension liquid is added to the plating solution.

The optimum conditions, such as the angle of inclination of the printed circuit board, the impact force and frequency of striking the printed circuit board, the type, concentration, and temperature of the low surface tension liquid, are determined by actually producing the printed circuit board and confirming the results. There is. However, to confirm this result, for example, it is better to vibrate the printed circuit board by hitting it than not to apply it, or it is better to add a low surface tension liquid such as alcohol rather than not. Only a very rough qualitative evaluation has been made.

[Problem to be solved by the invention]

When determining the optimal conditions for plating through qualitative evaluation after the fact (which cannot be determined in advance), the causes of the results are not fully investigated, so for example, the type and concentration of the optimal low surface tension liquid is determined. However, there are problems in that it takes time to find the optimal conditions such as temperature, and a large number of defective products are produced during trials. Another problem is that the installed equipment may have to be modified in order to improve the quality of the product after production has started.

The present invention has been made in view of the above circumstances, and makes it possible to quantitatively evaluate the degassing performance of small diameter holes by simulating operating conditions before producing printed circuit boards, and to determine the optimal operating conditions. The purpose is to

[Means to solve the problem]

In order to achieve the above-mentioned purpose, the method for evaluating the degassing properties of small holes in a printed circuit board according to the present invention is, for example, as shown in FIG. Then, the transparent plate 3 in which a large number of small diameter holes 4 having a predetermined pore size were formed was immersed in the test liquid 2, and after a predetermined defoaming operation was performed, the transparent plate 3 was observed from outside the experimental tank l, and the small diameter holes were A measure is taken to measure the proportion of small-diameter holes 4 from which air bubbles 5 have escaped (hereinafter referred to as defoaming rate).

[For production]

In the present invention, by measuring the defoaming rate of the transparent plate 3 after performing a predetermined defoaming operation in the experimental tank l, the experimentally set operating conditions can be determined before starting the production of printed circuit boards. The defoaming state of the transparent plate 3 below is quantitatively evaluated.

〔Example〕

Hereinafter, a method for evaluating the defoaming properties of small diameter holes in a printed circuit board according to an embodiment of the present invention will be described with reference to FIG.

The experimental tank 1 shown in FIG. 1 only needs to be made partially transparent, but here, the entire experimental tank 1 is made of a transparent material such as glass or acrylic resin.

Into this experimental tank 1, a plating treatment solution mixed with a low surface tension solution containing, for example, alcohol, surfactant, etc., was added to the test solution 2.
Fill as.

Then, a large number of small-diameter holes 4 having the same diameter as the small-diameter peer holes formed in the printed circuit board are formed in a transparent plate 3 having the same thickness as the printed circuit board to be produced, and this transparent plate 3
immersed in test solution 2.

At this time, air bubbles 5 are trapped in each small diameter hole 4 of the transparent plate 3.

The material of the transparent plate 3 may be transparent enough to allow observation of the small diameter hole 4 and the presence or absence of air bubbles 5 inside the small diameter hole 4 through the end face of the transparent plate 3 from the outside of the experimental tank 1. Here, in order to obtain experimental results in a short time, the transparent plate 3 is made of an acrylic resin that has high hydrophobicity and processability, and is chemically stable with respect to the test liquid 2.

Further, the arrangement of the small diameter holes 4 is not particularly limited, but here, in order to make it easy to clearly see all the small diameter holes 4, they are arranged in a vertical line.

Thereafter, the defoaming operation to be performed in the actual production process is simulated, such as leaving the transparent plate 3 as it is, tilting it, or hitting the transparent plate 3 to vibrate it.

After completing this defoaming operation, look through the end face of the transparent plate 3 from the outside of the experimental tank l and observe the small diameter holes 4 with your eyes 6. For example, as shown in FIG. The defoaming state can be quantified by measuring the number of small-diameter holes 4 (defoaming holes) in which air bubbles 5 have disappeared and calculating the defoaming rate (number of pA bubble pores/total number of pores).

These steps can be carried out by changing the inclination angle of the transparent plate 3 as necessary.
Optimal operating conditions such as the inclination angle of the transparent plate 3, vibration frequency, type of low surface tension liquid, concentration, temperature, etc. can be determined by repeating different impact force, vibration frequency, type of low surface tension liquid, concentration, temperature, etc. can be investigated.

In addition, by repeating the above procedure while changing the thickness of the transparent plate 3 and the diameter of the small diameter hole 4, the maximum thickness of the printed circuit board for a given hole diameter and the minimum hole diameter that can be formed on a printed circuit board of a given thickness can be determined. etc. can be obtained.

In this way, according to the small-diameter hole degassing properties of this printed circuit board, before actual production, a degassing operation can be simulated under various operating conditions, and the degassing state under each operating condition can be evaluated. By quantifying and measuring , it is possible to determine the optimal operating conditions that give the highest defoaming rate. By installing or modifying equipment that meets the optimal operating conditions, it is possible to eliminate the need for equipment modifications after production has started, increase the operating efficiency of the plating equipment, and improve the optimal operating conditions. There is no need to carry out trial production on the production line until the final product is determined, which prevents the occurrence of defective products due to trial production, and because only products made under optimal operating conditions are shipped as products, confidence in product quality can be increased. can be increased.

In the above embodiment, the bubbles 5 are visually observed after the defoaming operation, but the bubbles 5 may be observed using, for example, an industrial television monitor.

It is also possible to detect the presence or absence of air bubbles 5 in each small-diameter hole 4 using an optical sensor, and calculate the defoaming rate using a computer or the like.

〔Effect of the invention〕

As described above, according to the present invention, before actual production, a defoaming operation is simulated, and the defoaming state under each operating condition is quantified and measured. Therefore, by repeating the simulation of the defoaming operation and the measurement of the defoaming rate under various operating conditions, it is possible to determine the optimal operating conditions that provide the highest defoaming rate.

As a result, by installing equipment that meets the optimal operating conditions or modifying the equipment before starting production, it is no longer necessary to make unnecessary equipment modifications after the start of production, and the operating efficiency of the plating equipment is improved. can be increased.

In addition, since trial production is not performed on the production line until the optimal operating conditions are changed, it is possible to prevent the occurrence of defective products due to trial production, and because only products manufactured under optimal operating conditions are shipped as products, the quality of the products is improved. It is possible to increase the credibility of

FIG.

In the figure, 1... Experimental tank, 4...small diameter hole, 2...Test solution, 3...Transparent plate, 5... Air bubbles.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a method for evaluating the degassing properties of small diameter holes in a printed circuit board according to an embodiment of the present invention, and FIG. 2 is a diagram of a transparent plate showing an example of the observation results of the degassing state of the transparent plate. figure

Claims (1)

[Scope of Claims] [1] A transparent plate (3) filled with a test liquid (2) in an experimental tank (1) that is at least partially transparent, and in which a large number of small holes (4) having a predetermined hole diameter are formed. ) as the test solution (2)
The transparent plate (3) was observed from outside the experimental tank (1) after being immersed in the liquid and subjected to the prescribed degassing operation, and the air bubbles (
5) A method for evaluating small-diameter hole defoaming properties of a printed circuit board, the method comprising measuring the proportion of small-diameter holes (4) in which 5) has escaped.