JPH073911B2 - Printed circuit board manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a printed circuit board, and in particular, a tent is formed with a solder resist ink or a component marking ink in a through hole in which a component terminal is not inserted. This is referred to as “tenting”).

Recently, surface mounting technology (SMT: Surface Mounting Technolog)
y) has come to be used very often in order to physically shorten the wiring path and to make it thinner in consumer equipment due to the pursuit of high speed and high speed mounting in computers etc. . This inevitably requires a small-diameter through hole, but this through hole is used for electrical continuity, and component terminals are often not inserted.

In such a printed circuit board, the printed circuit board may be set on the test machine by vacuum suction when performing a test after mounting the component, and there is a demand for a tent to be attached to a hole where the component terminal is not inserted in some way. .

At this time, if the tent is not attached, the air leaks from it and the vacuum setting of the substrate cannot be performed. Usually, the tenting rate (the ratio of through holes that are actually used among the through holes that require a tent) is required to be 80 to 90% or more.

(Description of Prior Art) In manufacturing a printed circuit board, a solder resist and a component marking are generally formed by a screen printing method.

In screen printing, as shown in FIG. 1, a plate is formed on a mesh 2 provided in a frame 1 in a pattern corresponding to a wiring pattern of a printed circuit board 3, and an ink 5 is applied by a squeegee 4 through an opening of the mesh 2. It is carried out by pushing.

Conventionally, the printing of the portion to be tented was performed simultaneously with the solid solder printing of the other portion, as shown by the shaded area in FIG.

(Problems of the prior art) At this time, the solder resist provided in a portion other than the tenting portion is provided in order to repel solder so as not to attach to a portion where solder should not adhere during soldering. Therefore, since the solder resist repels solder at unnecessary portions, it is a very troublesome phenomenon that ink does not stick to the printed circuit board called "blurring" and there is a step on the surface of the printed circuit board. It is often the case that ink does not stick to the portion corresponding to the shadow in the squeegee direction of printing. Therefore, in such a conventional method, there is a large variation in whether or not the tenting is performed within one substrate, and further, there is a large variation in whether or not the tenting is performed for each substrate. It was very scarce. Then, after the completion of printing, the inspection was performed, and the solder resist printing was performed once again on the substrate that was not tented.

This is explained as follows from the ink transfer mechanism. As shown in FIG. 3 (a), in the portion other than the through hole portion, the pressure from the squeegee 4 is received by the substrate, and the ink 5 is pushed out from the mesh 2 to the substrate 3 by the pressure therebetween, while In the hole portion, as shown in FIG. 3 (b), it is intended to print in the hollow portion.
It is considered that there was nothing to receive the pressure of the squeegee, and the ink supply became unstable. Since the amount of ink ejected (transfer to the substrate) was unstable, the amount of ink remaining on the plate was also unstable, and the tenting property when printing was continued was also unstable.

For this reason, "bleeding" other than the tenting part
To prevent the phenomenon of "blurring" of the tenting part at the same time is usually 0.05% on the surface of the printed circuit board.
Since conductors with a height of ~ 0.20mm are often arranged vertically and horizontally, it is inevitable that ink will not be deposited on the side of a line perpendicular to the printing direction.

Therefore, when setting the printing conditions for screen printing of solder resist, the so-called "blurring", where ink must be applied, and "bleeding", where ink should not be applied, are applied. It is set at the very limit of both the phenomenon of being lost.

However, it is not easy to set such a condition, and such a condition does not exist at present, and there is no choice but to carry out in a form that does not satisfy either condition.

(Explanation of Structure / Operation of Invention) The present invention has been made in view of such a situation, and according to the present invention, all of the above-mentioned drawbacks are solved.

The details will be described below.

The present invention screen-prints a solder resist ink having a viscosity of 100 to 2,000 poise, or a component marking ink, only on a portion of a through hole forming a tent with a pattern having a diameter 0.03 to 1.00 mm larger than the diameter of the through hole. To do.

That is, FIG. 4 shows a cross-sectional view of an example of the present invention. First, ordinary solder resist printing is performed by clearing the through-hole portion to be tented (cross-section 7), and then the diameter of the through-hole is larger than the diameter of the through-hole. By using screen printing with a large diameter of 0.03 to 1.0 mm, the tenting film 8
Is formed.

In the present invention, it is necessary to be careful of "bleeding" because only the portion of the through-hole that covers the tent is printed with a tenting pattern having a diameter 0.03 to 1.0 mm larger than the diameter of the through-hole to be tented. Since there is almost no difference or the tolerance for "bleeding" is widened, it is possible to set printing conditions for transferring a large amount of ink, and thus the tenting film is formed.

That is, the printing conditions are preferably set as follows.

Let the squeegee rest. (Reduce the angle between the squeegee and the plate.) Round the corners of the squeegee. Increase the squeegee speed (printing speed). Make the rubber hardness of the squeegee soft. It should be noted that the number of tenting prints may be one, but it is two consecutive times. It is preferable to perform screen printing in the different directions as described above because stability of tenting is particularly increased.
In other words, if you perform screen printing more than twice consecutively,
Since the tenting film can be stably formed without changing the printing conditions to the normal solder resist printing, the indirect time (the time required for adjusting the printing conditions) can be shortened.

The diameter of the pattern for sticking the tent is preferably 0.03 mm or more and 1.0 mm or less in consideration of variations in registration. If the thickness is less than 0.03 mm, tenting will not be performed when the registration is uneven. When the thickness is larger than 1.0 mm, it is easy to apply the solder resist film on the periphery where it should not be applied.

The shape is preferably a circle, but a quadrangle, 6
It may be a prism or the like and does not define any shape.

Here, the diameter in the case of a polygon means the length of the diagonal.

Further, in the description in FIG. 4, the solder resist is printed first, but the order of printing the tenting pattern is not particularly limited. Even if the tenting printing is performed first and the solder resist printing is performed after that, it does not matter.

Further, the ink used in the present invention is preferably a solder resist ink or a component marking ink,
Desired resistance (eg solder heat resistance, surface hardness, adhesion, et
There is no particular limitation as long as it is an ink having c).

The viscosity is preferably 100 to 2,000 poise, and if it is less than 100 poise, the ink will not flow into the holes to form a film. It is difficult to make a film.

(Effect of the Invention) According to the present invention, a sufficient tenting film can be obtained with a little effort. It can be said that the time and effort required to change the printing conditions and print twice consecutively in the case of one-time printing are extremely small compared with the indirect time of registering the substrate and setting. Since a sufficient tenting film can be obtained with such a small amount of work, the efficiency is greatly improved as compared with the conventional work such as 100% inspection and reprinting.

Hereinafter, examples of the present invention will be described in comparison with comparative examples.

(Example 1) First, as shown in FIG. 5, 0.2 mmφ, 0.3 mmφ, 0.4 mmφ, 0.5
360 mm through holes (11, 12, 13, 14 each)
A substrate having holes (5 rows horizontally and 18 columns vertically) was prepared. However, there are holes 15 with a hole diameter of 0.8 mm and a land diameter of 1.4 mm at the four corners.

This plate has holes (21, 2
2, 23, 24) was prepared as shown in Fig. 6. Here, the black portion is the portion to be printed. The plate is an aluminum frame with 150
A mesh Tetoron mesh was put on the plate, and plate making was carried out with an emulsion film thickness of 20 μm.

Next, continuous screen printing was performed twice under the following conditions.

Ink / Asahi 240GS (Asahi Chemical Laboratory Co., Ltd. solder resist ink, viscosity 160-200 poise) Printer / Argon Hydra II After printing and after desired baking (130 ° C 30 minutes)
When evaluated, all-hole solder resist ink was tented.

Further, 100 sheets were continuously printed, and the above result was maintained.

(Example 2) In exactly the same manner as in Example 1, continuous screen printing was performed twice using only the following ink.

S-200W (Component marking ink manufactured by Taiyo Ink Mfg. Co., Ltd., viscosity 210 poise) From the first sheet to the 100th sheet, as in Example 1, tenting was performed 100%.

Comparative Example 1 The substrate shown in FIG. 5 was printed with the plate shown in FIG.
Incidentally, in FIG. 7, the image area is shown by hatching.

Here, the four corners have a hole diameter of 0.8 mm and a land diameter of 1.4 mm,
The pattern 26 was printed on the entire surface, except for the clear 25, which had a land diameter of +0.2 mm. When the four corners (the diameter of the land size + 0.2 mm was used as the non-image area) were not bulged, the average tenting rate was only 19% for the total hole diameters of 0.2φ to 0.5φ. (1st sheet) I printed 1st to 10th sheets
It only showed a tenting rate of 15-25%.

[Brief description of drawings]

FIG. 1 is an explanatory view showing screen printing, FIG. 2 is a pattern showing conventional tenting printing, FIG. 3 (a) is printing of a portion other than through holes of a printed circuit board, and FIG. 3 (b). Prints through holes on the printed circuit board
FIG. 5 shows a cross section of a through hole portion of one embodiment of the present invention, FIG. 5 shows a test substrate, FIG. 6 shows a tenting print pattern, and FIG. 7 shows a print pattern. (1) …… Frame, (2) …… Mesh (3) …… Printed circuit board, (4) …… Squeegee (5) …… Solder resist ink (6) …… Through hole (7) …… Solder resist pattern (8) …… Tenting printing

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-54-9770 (JP, A) JP-A-61-234595 (JP, A) Actual development-Sho-62-76556 (JP, U)

Claims (1)

[Claims] 1. A solder resist ink or a component marking ink having a viscosity of 100 to 2000 poise is used in a method of placing a tent in a through hole of a printed circuit board, in which a component terminal is not inserted, by a diameter of the through hole. Even with a pattern of 0.03 to 1.00 mm larger diameter, printing conditions to transfer a large amount of ink selectively on only one side, only the above through hole part in a process different from solder resist printing of other parts, or twice A method for manufacturing a printed circuit board, which comprises screen-printing by printing.