JPH06103789B2 - Method and apparatus for manufacturing through hole of printed wiring board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing through holes of a printed wiring board having printed patterns on both sides.

[0002]

2. Description of the Related Art As a method of conducting a through hole having a diameter of 0.7 to 0.8 mm formed between lands on the front and back of a printed wiring board, a method of conducting by copper plating and a method of conducting using a conductive paste have been conventionally used. There was a way to make it happen.

Among these, as a method of using the conductive paste, there is a pin type method shown in FIG. This is done by pin 2 so that the tip is dipped in a conductive paste in a tray (not shown) arranged on the lower surface of the through hole 1a of the printed wiring board 1.
Is inserted from above to below the through hole 1a, the conductive paste 3 is attached in a ball shape to the lower end thereof, and the paste is pulled upward as it is to apply and solidify on the inner wall surface of the through hole 1a.

More specifically, as shown in FIG. 5 (a), with the A surface 1A of the printed wiring board 1 as the lower surface, the pin 2 is pulled out to a portion of the inner wall of the through hole 1a close to the A surface 1A. After the paste 3a is attached and the solvent in the conductive paste 3a is removed by baking to solidify, the printed wiring board 1 is turned over and the B side 1B is made the bottom side as shown in FIG. 5B. Similarly, the conductive paste 3b is attached and baked on the portion of the inner wall of the hole 1a near the surface B.

After this, as shown in FIG. 5C, the A surface 1A of the through hole 1a is placed with the A surface 1A facing upward.
A silk screen plate 5 having a printing pattern corresponding to the land 4A is set on the upper surface of the land 4A formed in advance on the side edge, and the conductive paste 6 applied on the upper surface is made of a rubber plate having a thickness of about 10 mm. A squeegee plate 7 is screen-printed to provide a conductive paste 6a portion, which is also baked.

Further, as shown in FIG. 5 (d), the through hole 1a is formed with the printed wiring board 1 inverted and the side B facing upward.
Similarly, the conductive paste 6b is printed and baked by screen printing on the upper surface of the land 4B formed in advance on the edge of the B surface 1B side. The silk screen plate 5'at this time has a print pattern corresponding to the land 4B on the B side 1B of the printed wiring board 1.

Through the above steps, the printed wiring board 1
The through hole 1a becomes a through hole in which the lands 4A, 4B on both sides are conducted by the conductive pastes 3a, 3b, 6a, 6b.

Another method using the conductive paste is a vacuum printing method shown in FIG. In this method, as shown in FIG. 6A, while vacuum suction is performed from the lower surface (B surface 1B) side of the through hole 1a of the printed wiring board 1 with the A surface 1A facing upward, The conductive paste 9 on the silk screen plate 8 having a corresponding printing pattern is injected into the through hole 1a with the squeegee 10, the conductive paste 9a is attached to the A surface 1A side of the inner wall of the through hole 1a, and this is baked. Solidify.

Next, as shown in FIG. 6B, the printed wiring board 1 is turned over, and the conductive paste 9b is similarly vacuum-sucked with the B side 1B as the upper side to the B side 1B side of the inner wall of the through hole 1a. It is attached to and baked to solidify. The print pattern of the silk screen plate 8'at this time is B side 1B.
Corresponding to the through hole 1a.

Then, as shown in FIG. 6C, a silk screen plate 11 having a printing pattern corresponding to the pattern of the land 4A on the A side is set, and the conductive paste 9c is placed on the upper surface of the land 4A. Screen print and bake this. Further, as shown in FIG. 6 (d), the printed wiring board 1 is turned over so that the B surface 1B is on the upper side, and similarly, the conductive paste 9d is screen-printed on the upper surface of the land 4B to be baked and solidified. The printing pattern of the silk screen plate 11 'at this time corresponds to the pattern of the land 4B on the B side 1B.

[0011]

However, in the pin type method of FIG. 5 described above, it is difficult to control the shape and size of the ball of the conductive paste 3 at the tip of the pin 2 to be constant,
Through holes are usually 50 to 10 on one printed wiring board.
Since 0 is also formed, disconnection between both sides in those through holes,
Significant variations in quality, such as high and low conduction resistance between both sides, occur. Further, as shown in FIG. 5, two kinds (5, 5 ') of silk screen plates are required, and at least four steps of coating and solidifying work are required, and the above-mentioned variation becomes larger, and mass productivity is improved. It becomes unreliable.

Also, in the vacuum suction printing method, the conductive paste is individually applied to the inner wall of the through hole 1a to be a pinhole from both sides, and as shown in FIG.
Since four steps are required as in the pin type method, the quality of the through hole fluctuates, and there are problems in mass productivity and reliability as in the above case. Further, this method requires four kinds of silk screen plates (8, 8 ', 11, 11').

An object of the present invention is to completely fill the through holes with the conductive paste in one printing so that the process can be greatly simplified and the manufacturing method and apparatus for improving the mass productivity and reliability of the through holes. Is to provide.

[0014]

To this end, the manufacturing method of the present invention comprises a first step of preparing a printed wiring board in which through holes are formed between lands on the front and back surfaces, and the through holes of the printed wiring board. And a second step of setting a mask plate having a pattern hole having a size overlapping with the land on the printed wiring board so that the pattern hole includes the land, and at least a squeegee having a convex curved surface on a sliding contact surface is lengthened. A third step of sliding on the mask plate in a direction intersecting the direction to fill the conductive paste on the mask plate from one surface side of the through hole through the pattern hole, and the other surface side of the through hole. And a fourth step of placing the above-mentioned conductive paste protruding onto the land on the other surface side.

Further, the manufacturing apparatus of the present invention is a mask plate which is set on one surface of a printed wiring board and has a through hole of the printed wiring board and a pattern hole having a size overlapping the land around the through hole. And a squeegee having a convex curved surface at least in a sliding contact surface for sliding the conductive paste placed on the mask plate into the through hole by sliding on the mask plate in a direction intersecting the longitudinal direction. As configured.

[0016]

According to the present invention, the filling amount of the conductive paste into the through hole of the printed wiring board is dramatically increased by the pattern hole of the mask plate and the convex curved surface shape of the sliding contact surface of the squeegee.
Since the filling of the necessary and sufficient amount of the conductive paste is completed by one printing operation, the process is simple and the conduction between the front and back of the formed through hole is ensured.

[0017]

EXAMPLES Examples of the present invention will be described below. FIG. 1 is a diagram showing a through hole manufacturing method according to one embodiment. In this embodiment, the lands 4 on both sides 1A and 1B are used.
A printed wiring board 1 having a through hole 1a formed between A and 4B
With the A surface 1A as the upper surface, the lower surface of the penetration 1a is supported by appropriate means in a posture in which it is not pressed.

Then, as shown in FIG. 1A, a metal mask plate 21 whose entire circumference is supported by a silk screen 20 is arranged on the upper surface. Needless to say, the pattern holes 21a of the metal mask plate 21 correspond to the positions of the through holes 1a of the printed wiring board 1, but the size thereof overlaps with the through holes 1a and a part of the land 4A. Accurately position as size.

In this state, the conductive paste 22 is applied to the upper surfaces of the metal mask plate 21 and the silk screen 20, and then the column-shaped squeegee 23 is slidably moved in a direction orthogonal to its longitudinal direction without rotating. The conductive paste 22 is press-fitted into the through hole 1 a of the printed wiring board 1 from the pattern hole 21 a of the metal mask plate 21.

At this time, the conductive paste 22a is filled to the extent that a part of the conductive paste 22a projects downward from the through hole 1a. At this time, the conductive paste 22a is simultaneously applied to a part of the land 4A on the upper surface 1A.

Thereafter, as shown in FIG. 1B, when the A surface 1A and the B surface 1B of the printed wiring board 1 are reversed and placed on the horizontal plane plate 24, the influence of gravity is exerted. ,
A part of the conductive paste 22a protruding to the B surface 1B side hangs down in the circumferential direction and comes to be placed on the land 4B.

Therefore, if baking is performed after this, the solvent in the conductive paste 22a is blown off and the conductive paste 22a is solidified to complete the through holes, and the through holes complete the lands 4A and 4B of the printed wiring board 1.
Will be conducted.

As the conductive paste 22, a silver paste having a viscosity of about 300 poise (PS) was used.
It is also possible to use copper paste or carbon paste. In the present embodiment, the baking conditions were set to a temperature of 150 ° C. and a time of 30 minutes, but the baking conditions are set according to the conductive paste used. If baking is insufficient, solidification will be insufficient, and conversely, excessive baking will cause breakage of through holes.

The metal mask plate 21 described above has a wall thickness of about 0.15 to 0.20 mm, and as shown in FIG. 2, the entire lower surface periphery thereof is attached to the silk screen 20. Since the silk screen 20 does not exist on the lower surface of the pattern hole 21a of the metal mask plate 21, the amount of conductive paste passing through the pattern hole 21a increases.

The increase in the amount of the passing conductive paste becomes more remarkable by using the column-shaped squeegee 23. The squeegee 23 catches the conductive paste 22 between the lower surface of the squeegee 23 in the sliding movement direction and the metal mask plate 21 and pushes the conductive paste 22 into the pattern holes 21a of the metal mask plate 21. Is a convex curved surface, the angle of the portion in contact with the metal mask plate 23 becomes smaller at a portion closer to the contact point, so that the conductive paste pushing action at this portion is squeegeeed.
This is because the pressing is effective not on the line (conventional squeegee) along the longitudinal direction of 3 but on the surface. Further, since the front surface portion of the squeegee 23 in the sliding movement direction is also a convex curved surface, the amount of conductive paste stored therein increases.

In this embodiment, as the squeegee 23, a hard rubber material having a diameter of 30 mm (hardness of 60 degrees as measured by a Rockwell hardness meter) is used. However, the portion contacting the metal mask plate 21 and the conductive paste are used. The portion that captures 22 is only required to be a convex curved surface. Therefore, the squeegee 23 is not limited to a true circular cross section, and may be a columnar member having an elliptical shape or a semicircular shape only at the tip. The radius of curvature of the convex curved surface is preferably 10 to 20 mm.

As described above, according to this embodiment, since the conductive paste 22 is printed only once on one side of the printed wiring board 1, only one metal mask plate 21 is required as a printing pattern. After this printing, the printed wiring board 1 may be turned upside down, wait until the protrusions of the conductive paste protruding downward are smoothed, and then baked and solidified. Therefore, compared with the conventional through hole manufacturing method. The working process is simplified to about 1/4.

Moreover, the through hole is the printed wiring board 1.
Since the through hole 1a is filled with the conductive paste 22a so as to protrude to the opposite side, the lands 4 on both sides thereof are formed.
The conduction between A and 4B is ensured, and it becomes a high-quality and highly reliable through hole with little variation.

The method of applying the conductive paste 22a to the land 4B on the back surface 1B side is not limited to the method of reversing the printed wiring board 1 and leaving it to stand, but pressing the flat plate from the lower surface side after the printing is completed. Alternatively, a method of crushing the conductive paste 22a protruding to the land 4B side can be adopted.

FIG. 3 shows ten through holes (measurement numbers 1 to 1).
Regarding 10), the result of measuring the conduction resistance between the front and back lands is shown. Measuring instrument is LCR meter (HP4262A)
At 1 KHz and 1000 mΩ range. here,
Maximum value is 13 mΩ, minimum value is 8 mΩ, average value is 10.2
mΩ, by the conventional method (maximum value is 25 m
Ω, the minimum value is 13 mΩ, and the average value is 20.3 mΩ), the conduction resistance is significantly reduced.

FIG. 4 shows the results of the load test. Power supply is DC 40V, load is constant current load (PLZ27L), 100mA, 150mA, 200mA, 250mA
It was performed at a constant current of A, 300 mA, and 1 A. No breakage occurred in the through holes for all the samples of measurement numbers 1 to 10.

Although a printed wiring board made of an ordinary material is used here, through holes can be similarly formed on a ceramic substrate or a glass substrate. The diameter of the through hole for forming these through holes is approximately 0.3 mm.
That is all. The mask plate 21 is not limited to metal,
Of course, it may be formed of a silk screen.

[0033]

As described above, according to the present invention, there is an advantage that the manufacturing process is greatly simplified, and the manufactured through hole has little variation, and a highly reliable through hole can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of a method for manufacturing a through hole according to the present invention.

FIG. 2 is a plan view of a metal mask plate used in the manufacturing method.

FIG. 3 is a diagram showing measurement results of front-back conduction resistance of through holes obtained by the same manufacturing method.

FIG. 4 is a diagram showing measurement results of a load test of through holes obtained by the same manufacturing method.

FIG. 5 is an explanatory view of a conventional through-hole manufacturing method by a pin type method.

FIG. 6 is an explanatory view of a conventional through-hole manufacturing method by a vacuum suction method.

[Explanation of symbols]

1: Printed wiring board, 1A: A side, 1B: B side, 1
a: through hole, 2: pin, 3, 3a, 3b: conductive paste, 4A, 4B: land, 5, 5 ': silk screen plate, 6, 6a, 6b: conductive paste, 7: squeegee,
8, 8 ': silk screen plate, 9, 9a to 9d: conductive paste, 10: squeegee, 11, 11': silk screen plate, 20: silk screen, 21: metal mask plate, 22, 22a: conductive paste, 23 : Cylindrical squeegee, 24: Flat plate.

Claims (6)

[Claims] 1. A first step of preparing a printed wiring board in which a through hole is formed between lands on the front and back surfaces, and a mask plate having a pattern hole having a size overlapping the through hole and the land of the printed wiring board. A second step of setting the pattern holes on the printed wiring board so that the pattern holes include the lands, and sliding at least a squeegee having a convex curved surface on the mask plate in a direction intersecting the longitudinal direction. And a third step of filling the conductive paste on the mask plate from one surface side of the through hole through the pattern hole, and the conductive paste protruding on the other surface side of the through hole to the land on the other surface side. And a fourth step of mounting the through hole on the printed wiring board. 2. The method of manufacturing a through hole of a printed wiring board according to claim 1, wherein the mask plate is formed of metal or silk screen. 3. The method for manufacturing a through hole of a printed wiring board according to claim 1, wherein the fourth step is a step of reversing the front and back of the printed wiring board and leaving the printed wiring board left in a substantially horizontal state. 4. The method of manufacturing a through hole of a printed wiring board according to claim 1, wherein the fourth step is a step of crushing the conductive paste protruding from the other surface side. 5. A squeegee that is slid to fill the through holes of a printed wiring board in which through holes are formed between lands on the front and back surfaces so that at least the sliding contact surface has a convex curved surface. An apparatus for manufacturing a through hole of a printed wiring board, which is characterized in that 6. A mask plate set on one surface of a printed wiring board is provided with a through hole of the printed wiring board and a pattern hole having a size overlapping the land around the through hole. The manufacturing apparatus for a through hole of a printed wiring board according to claim 5.