JP2571105B2 - Through-hole printing equipment - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to a paste on the inner surface of a large number of through holes provided for conductively connecting wiring conductors on both surfaces of a circuit board used for a thick film hybrid integrated circuit. The present invention relates to a through-hole printing apparatus for applying a conductive ink.

(Prior art and its problems) In order to increase the degree of circuit integration, thick-film hybrid integrated circuits require printed wiring conductors on both the front and back sides of a circuit board (for example, an alumina board, hereinafter referred to as a board), which is the base of the circuit configuration. By adopting a structure that conducts conductive printing on the inner surface of a small (for example, about 0.1 mmφ to 2 mmφ) through hole provided to conduct the conductor parts on both surfaces according to Serves the desired purpose. A method of performing conductor printing on the inner surface of such a through-hole is called through-hole printing. In this case, the cross-sectional shape of the ideal through-hole printed with the through-hole is as shown in FIG. 2 to 5 show the cross-sectional shapes of the through holes when printing is incomplete. In these figures, reference numeral 1 denotes a circuit board, 2 denotes conductive ink, and 3 denotes an inner surface of a through hole.

Conventionally, in order to perform such through-hole printing, a screen printing machine that prints a wiring conductor is generally used, and a vacuum pressure interlocking with a printing operation of applying a paste-like conductive ink is applied from a direction opposite to a printing surface, A method is employed in which the paste-like conductive ink applied near the through-hole is suction-controlled to adhere to the inner surface of the through-hole. However, in such a conventional method, incomplete through-hole printing shown in FIGS. 2 to 5 is often formed, and therefore, all the individual holes printed with through-holes are subjected to an external appearance inspection. Defective parts were detected and incomplete parts were corrected. Such an operation is inefficient and has many problems in terms of product reliability.

That is, in the example of FIG. 2, there is a portion below the hole 3 where the ink is not applied. In the example shown in FIG. 3, scattered ink (convex portions) scattered during vacuum suction is attached to the back surface conductor. In the example of FIG. 4, the ink on the inner surface of the hole 3 is lacking.
In the example shown in FIG. 5, the hole 3 is filled with ink. These problems are summarized as follows.

(1) There is a lack of printing on the whole or a part of the inner surface of the hole, and it takes a long time to perform a total inspection for detecting those defective portions and to repair it, which is an obstacle to improving the work efficiency. .

Especially when there are many holes to be printed on the same board in the same board, for example, the board dimensions are 50 mm long x 50 mm wide x thickness
When there are 200 holes with a diameter of 0.4 mm on a 0.6 mm substrate and through-hole printing is performed simultaneously on the holes, poor printing inside the holes is remarkable and reproducibility is low.

(2) If the degree of vacuum is increased to prevent the occurrence of the failure described in (1) and the suction force of the paste-like conductive ink is increased, the paste-like ink scatters and adheres to the periphery of the printed wiring, thereby causing a circuit short circuit accident. There is a high risk of occurrence. In addition, the fine adjustment control of the vacuum pressure has a technical limit, so that the occurrence of defects cannot be completely prevented.

(3) If there is a hole in the same substrate that requires printing of through holes of different diameters or shapes, or if the number of holes per unit area of the substrate is extremely deviated to a part of the substrate surface, the vacuum pressure Control was impossible.

(Object of the Invention) An object of the present invention is to solve the above-mentioned problems and to provide a through-hole printing apparatus capable of reliably performing through-hole printing.

(Structure of the Invention) As a means for solving the above-mentioned problems, a through-hole printing apparatus according to the present invention employs a conductor coated in advance near a through hole provided at a position where wiring conductors on both sides of a substrate are connected. The centrifugal force generating part that can apply the centrifugal force in the direction perpendicular to the substrate surface to the paste-type ink uniformly and smoothly apply it to the inner surface of the through hole. It is. According to the present invention, ideal through-hole printing is performed, and a circuit board having good reproducibility and quality can be efficiently produced.

That is, the through-hole printing apparatus of the present invention prints a predetermined printed wiring pattern on the surface of a circuit board used for a thick film hybrid integrated circuit, and forms a large number of through holes provided at predetermined positions of the wiring pattern. A screen printing device for applying and printing paste-like conductive ink for forming a conductor on the inner surface, and fixed to the lower side of the horizontal substrate at substantially the center of the upper side of the horizontal substrate fixed to the side surface of the base of the screen printing device At least one disk-shaped rotary table that is horizontally held and rotatable in conjunction with the motor that has been rotated, and the surface of the circuit board is provided at the periphery of the upper surface of the disk-shaped rotary table with the radius of the disk-shaped rotary table. A centrifugal force generator having a plurality of circuit board holders arranged to hold the circuit board so as to be perpendicular to the direction, and the circuit board is rotated by rotation of the electric motor. Is characterized in that said large number of through the pasty conductor ink applied printed in the vicinity of the holes are configured to be uniformly smooth coating on the inner surface of the through hole.

Conventionally, through-hole printing was formed by the action of [screen printing machine] + [vacuum pressure]. On the other hand, the present invention provides (a) [screen printing machine] + [vacuum pressure] + [centrifugal force generating section] Or (b) there is a fundamental difference in that it is constituted by [screen printing machine] + [centrifugal force generating section].

 Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 6 is a partial front sectional view in the case of the above-mentioned (a) [screen printing machine] + [vacuum pressure] + [centrifugal force generating section]. The configuration in the case of (b) is a case where no vacuum pressure is applied in FIG.
In the figure, the part composed of the shaft 10, the rotary table 11, the holder 12, the shielding plate 13, the electric motor 14, the horizontal board 15, the housing 16, the control circuit 17, and the operation unit 18 on the right side from the center is a through hole according to the present invention. 2 shows a centrifugal force generating unit which is a main part of the printing apparatus.

On the other hand, the screen printing machine on the left side of the figure is a conventional screen printing machine in which a substrate (circuit board) 22 is mounted on a substrate table 21 on a base 20, and a printed wiring pattern is formed in a negative shape. An appropriate amount of paste ink 24 is placed on the screen 23. By lowering the squeegee (ironing board) 25 and moving the squeegee 25 from the front of the figure to the back while applying printing pressure to the screen 23,
A predetermined wiring conductor pattern on the screen 23 is copied to the print substrate 22. Further, in this case, the substrate table 21 has a cut-out portion at a position corresponding to the position of the through-hole for the through-hole printing of the printing material 22 so that the vacuum pressure acts on the paste-like ink 24.

When a printed wiring pattern is copied while applying a vacuum pressure of about 50 to 200 mmHg to a through hole of the substrate 22 requiring through-hole printing through a cutout portion of the substrate table 21, the paste ink is applied with a vacuum pressure. In order to form through-hole printing by suction, it is sucked and adhered to the inner surface of the through-hole, but in the above process, as described above, incomplete through-hole printing is formed as shown in FIGS. You. The through-hole printing of the clogged hole as shown in FIG. 5 can be electrically non-defective when a continuity test is performed, but is clearly defective in structure.

FIG. 7 is a perspective view of the upper surface of a turntable 11 horizontally fixed to the shaft 10 of the centrifugal force generating section in FIG. 6 corresponds to A- which passes through the center of the turntable 11 in FIG.
FIG. In FIG. 7, the shielding plate 13 is omitted for easy understanding.

Now, the printing material (circuit board) 22 in the incomplete through-hole printing state after the [screen printing machine] + [vacuum pressure] process as described above is used for the holder 12 of the centrifugal force generating unit which is a main part of the present invention. When the operation unit 18 is operated and the electric motor 14 is rotated, the rotating table 11 that is linked by the shaft 10 is rotated, and the printing material 22 is rotated together with the holder 12. Due to this rotation, a centrifugal force F expressed by the following equation acts on the paste-like conductive ink near the through hole copied on the printed matter 22 in a direction perpendicular to the rotation direction (arrow). That is, if the centrifugal force acting on the paste ink is F, Where, W: Weight of paste ink (kg) r: Rotation radius (cm) ω: Angular acceleration (rad / s) g: Gravitational acceleration (≒ 980) (cm ² / sec ² ) At low speeds, the centrifugal force is small and does not contribute to the formation of through-hole printing. However, when the rotational speed is gradually increased to reach the critical point of the surface tension of the paste-like ink or more, the paste-like ink moves in the direction of arrow F in FIG. It flows uniformly along the inner surface of the through hole and is smoothed.
As a result, uniform through-hole printing as shown in FIG. 1 is formed. Moreover, the excess paste ink does not withstand the centrifugal force and collides with and adheres to the shielding plate 13.

The centrifugal force F acts on each through-hole printed portion in proportion to the weight W of the paste ink as shown in the above equation,
For example, as shown in FIG. 5, a large centrifugal force proportional to the amount of ink acts on a printed portion of a through-hole in which the amount of ink is large and the hole is clogged, and acts to eliminate the clogged hole. Also, when the amount of ink is small, it acts to blur the inner surface of the hole. After the printing process described above,
After the baking process, the printing on one side is completed, and then the other side is similarly subjected to the same operation from the screen printing, and the printing process is completed.

In this manner, uniform through-hole printing can be performed with good reproducibility by setting the number of rotations in accordance with the print pattern and the shape of the holes on the printing medium, the viscosity and amount of the paste-like ink, the printing state, and the like.

In the embodiment shown in FIGS. 6 and 7, the circumference of the rotary table 11 is divided into four equal parts and the holder 12 is arranged so that four print substrates 22 can be mounted. It is also possible to arbitrarily divide the frequency or to arrange the holders 12 concentrically twice. Further, since the centrifugal force F is proportional not only to the rotational speed and the weight of the ink but also to the rotational radius r, the dimensions of each part are set in consideration of the workability of each.

FIG. 8 is a rotary table of a centrifugal force generating unit according to the present invention.
An embodiment is shown in which 11 is mounted on the same shaft 10 in two stages, and the respective part numbers are the same as in the case of FIG. 7, and the operation is also the same.

In the above embodiments, the operation of through-hole printing by the configuration of [screen printing machine] + [vacuum pressure] + [centrifugal force generating section] suitable for actual mass production has been mainly described. Is also effective in the case of a configuration of [screen printing machine] + [centrifugal force generating section] in which no vacuum pressure is applied.

In a specific use example of the device of the present invention, the diameter is about 180 mmφ.
A 50mm square substrate (circuit board) with about 100 0.4mmφ through holes is mounted on a rotary table with a rotation speed of about 1700r.p.
The work was completed in about 30 seconds by applying centrifugal force by rotation of m. It was proved that high quality through-hole printing was obtained, and the quality could be guaranteed by sampling inspection.

Further, in the present invention, from the viewpoint of workability, function as a device, miniaturization and safety, the centrifugal force generating unit is a through-hole printing device fixed to a screen printer, but the centrifugal force generating unit is independent. Of course, it is also possible to use an existing screen printing machine as an apparatus.

In this embodiment, the case of conductor printing has been described. However, if a paste-like resistive ink, a dielectric ink, or other ink is used, the present invention can be applied to the case of resistance or other printing.

(Effects of the Invention) As described above in detail, in the through-hole printing forming method by the vacuum suction method using the conventional screen printing machine, there are many printing defects on the inner surface of the hole and the reproducibility of the through-hole printing is ensured. However, in the through-hole printing apparatus using the centrifugal six according to the present invention, a force for eliminating the paste-like ink printed in the clogged state acts, and the paste-like ink is used. When printed in a small area, a force that blurs the entire inner surface of the hole acts to maintain the uniformity of through-hole printing, as well as to improve the efficiency of printing work, improve yield, and improve reliability. This has an extremely large effect in terms of improvement of the thickness, and can dramatically improve the production efficiency of the thick film hybrid integrated circuit IC.

[Brief description of the drawings]

1 to 5 are partial cross-sectional views of a through-hole printing portion of a circuit board used for a thick film hybrid integrated circuit, and FIG. 6 is an embodiment of a through-hole printing apparatus having a fixed centrifugal force generating unit according to the present invention. FIG. 7 is a front view including a partial cross section of the example, FIG. 7 is a perspective view including a partial structure of the centrifugal force generating portion of one embodiment of the present invention shown in FIG. 6 and a mounted state of a substrate, and FIG. FIG. 9 is a perspective view showing an embodiment in which the rotary table of the centrifugal force generating unit has two stages. 1,22 ... print substrate (substrate), 2 ... conductive ink, 3 ...
Inner surface of through hole, 10… axis, 11… rotating table, 12…
Holder, 13… Shield plate, 14… Electric motor, 15… Base, 16… Case, 17… Control circuit, 18… Operation unit, 20…
... Base, 21 ... Substrate table, 23 ... Printing screen, 24 ... Paste ink, 25 ... Squeegee.

Claims (1)

(57) [Claims] A printed wiring pattern is printed on a surface of a circuit board used for a thick film hybrid integrated circuit, and a conductor is formed on an inner surface of a large number of through holes provided at predetermined positions of the wiring pattern. A screen printing device for applying and printing paste-like conductive ink for printing, and an electric motor fixed to the lower side of the horizontal substrate at substantially the center of the upper side of the horizontal substrate fixed to the side surface of the base of the screen printing device. At least one that is horizontally held and rotatable
A plurality of disc-shaped rotary tables, and a circuit board arranged around the upper surface of the disc-shaped rotary table so as to hold the circuit board so that the surface of the circuit board is perpendicular to the radial direction of the disc-shaped rotary table. A centrifugal force generating unit having a plurality of circuit board holders provided, wherein the paste-like conductive ink applied and printed near the plurality of through holes of the circuit board by rotation of the motor is provided on an inner surface of the through hole. A through-hole printing apparatus characterized in that it is configured to be uniformly and evenly applied to a printing medium.