JPH0462890A - Formation of thick film through-hole - Google Patents

Abstract

PURPOSE:To enable formation of a baked film having thick edge by drying and hardening print paste without a separating a substrate from a through-hole board after printing a conductor using the through-hole board having a through- hole whose hole diameter is smaller than that of a through-hole of the substrate and by baking a printed substrate along to print a conductor of a through-hole part. CONSTITUTION:For example, an alumina substrate 1 wherein a hole of a hole diameter of 0.5mm is shaped as a hole 2 for a through-hole and a through-hole board 3 which is provided with a hole of a hole diameter of 0.35mm shaped in registration to a position of the hole 2 are used, air flow is made through a suction hole 5 below the through-hole board and silver palladium paste is printed on the substrate by squeegeeing using a 200 mesh screen. A circuit part and a through-hole part on the substrate are formed by the print conductor 4. Thereby, it is possible to acquire a conductive layer wherein a through-hole part is incorporated by drying the substrate 1 and the through-hole board 3 without separation and then by separating them and baking the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming thick film through holes in double-sided printed wiring boards and the like.

[Prior Art] With the increase in the mounting density of electronic components on printed wiring boards, wiring boards are being used to connect both sides of conductor circuits on double-sided printed wiring boards and to make electrical connections between inner layers on multilayer wiring boards. Through-hole type substrates are often used, in which conductive layers are connected through holes provided on the front and back sides of the board.

The through-hole part in this type of board is usually
It is formed using the following steps. That is, as shown in the schematic cross-sectional view of FIG. 3, in accordance with the hole position of the hole 2 for the through hole in an insulating substrate, for example, an alumina substrate, a hole larger than the hole diameter of the substrate is formed. The formed jig is used as a base for the board during conductor printing, and the printing machine is operated to create an air flow by sucking air through the suction holes 5 below this base (hereinafter referred to as the through-hole board). A bed portion 6 is arranged.

As seen in the schematic cross-sectional view of Fig. 4, which shows an enlarged view of the through-hole section in such a state, a conductor 4 such as silver palladium paste is printed on the surface of the board by squeezing printing, and then the printed conductor 4 is Through-hole portions are formed by heating and drying the substrate at a temperature of 150° C. for about 10 minutes, and then baking it at 850° C. for 10 minutes.

[Problems to be Solved by the Invention] However, when a through hole is formed by the method described above, as shown in FIG. The film thickness of the conductor layer 4 is thinner than that of the conductor layer 4, and when a half IB for mounting components is placed in this part, the so-called half [
11<Since it is easy to crack, in order to increase the thickness of the film on the edges, conventionally, only the through-hole areas were printed to compensate for solder resistance, which resulted in an increase in cost. .

Therefore, the purpose of the present invention is not to supplement the semi-el resistance by adding a conductor printing process for through poles in addition to the conductor printing process on the board surface, as in the past, but rather The purpose of this invention is to provide a method for forming thick film through poles that can be performed in tJ%.

[Means and actions for solving the problem] The inventor of the tree
As a result of research to achieve the above objective, we found that when printing conductive paste on the board surface to form a conductive layer on the conductor part and through-hole part, the edge part of the through-hole on the side where the back side of the board contacts the through-hole plate If the end portion of the conductor layer is placed in a through hole, for example, so that the angle formed on the exposed surface side of the coated conductor film that is bent at the edge portion is smaller than 180 degrees, the edge Since the thickness of the film does not become thinner, the printing paste is dried and hardened without separating the board from the through-hole board after printing the conductor using a through-hole board with through-holes with a diameter smaller than that of the through-holes on the board. We have discovered that a thick film through hole that solves the above problems can be obtained by firing only the conductor in the through hole portion and firing the conductor in the through hole portion (=1), and have arrived at the present invention.

That is, the method for forming a thick film through hole of the present invention can be described as follows.

Holes for through-holes that communicate with the front and back sides of the insulating substrate are formed, and the through-hole plate is used as a stand when printing a conductive film on the substrate. After creating a downward suction air flow and printing a conductive paste for conductor circuits on the conductor part and through-hole part of the board, dry and bake the board and print on the conductor part and through-hole part. In a method for forming a thick film through hole that involves baking a conductor, the hole has a diameter smaller than that of the through hole provided in an insulating substrate, and the hole is aligned with the hole for the through hole. A perforated plate or an air-permeable plate that allows air to freely pass through is used as a through-hole plate for mounting an insulating substrate, and after printing a conductive film in this way, the insulating substrate and through-hole plate are used. Without separating the hole plate,
A method for forming a thick film through hole, which comprises drying the conductive paste, separating the insulating substrate from the through pole plate, and firing the insulating substrate.

FIG. 1 is a schematic cross-sectional view for explaining the method of forming a thick film through hole in an embodiment of the present invention, and FIG. 2 is an enlarged view of the state of the through hole immediately after printing a conductor in the method of the present invention. It is a schematic cross-sectional view.

In the method of the present invention, a substrate 1 in which through-hole holes 2 are drilled, and a through-hole plate 3 having holes with a smaller diameter than the substrate 1, which are aligned with the holes 2, are used for printing. After printing the conductor part and through-hole part on the top surface of the board while suctioning air from the suction hole 5 provided in the machine bed part 6, the printed conductor 4 is dried as it is without separating the through-hole plate 3. Then, only the printed circuit board is fired to burn out the conductors. In this way, the conductor film on the edge of the substrate through-hole, at least on the side that was in contact with the through-hole plate, has a sufficient thickness. Next, if you turn the board over and repeat the same process,
A conductive film of sufficient thickness is formed on both edges of the substrate through-hole.

Note that the same effect can be obtained by using an air-permeable material such as paper that allows air to move freely as the through-hole plate 3.

In the conventional method for forming thick-film through-holes, the thickness of the through-hole edges of the substrate separated from the through-hole plate after printing the conductive base becomes thinner due to the surface tension of the paste, but in the method of the present invention, Since they do not separate, the surface tension causes the film to dry while remaining thick at the through-pole edge portion 8 on the back side of the substrate, so the edge film thickness of the fired film can also be thickened, and the film thickness on the front side edge 7 can also be increased by turning the substrate over. The film thickness can be increased by repeating similar operations.

The present invention will be further explained below with reference to Examples.

[Embodiment] A method of forming a thick film through hole in an embodiment of the present invention will be explained with reference to FIG. 1 described above, and FIG. 2 described above, which shows an enlarged view of the through hole portion immediately after printing a conductor. That is, an alumina substrate with a thickness of 0.635 mm in which a hole with a hole diameter of 0.5 mm is bored as a hole 2 for a through hole];
Using a through-hole plate 3 with a hole of hole diameter Q of 35 mm that matches the position of the hole, creating an air flow through the suction hole 5 below the through-hole plate, and squeezing using a two-round mesh screen. A silver-palladium paste was printed on the substrate, and the printed conductor 4 formed a circuit section and a through-hole section on the substrate. Note that reference numeral 6 indicates the bed of the printing press, and the board was fixed using leaf springs from four directions.

In the above state, without separating the substrate] and the through-hole plate 3, dry them at 150°C for 10 minutes, then separate them and bake the substrate 1 at 850°C for 10 minutes to form the through-hole portion. A conductive layer was obtained.

As seen in FIG. 2, the through-hole edge 7 on the front side of the board has a thin conductor film thickness due to the surface tension of the paste, but the through-hole edge 8 in contact with the through-hole plate on the back side of the board has an edge. Since the surface of the conductive film at the edge portion is bent at an angle of less than 1.80 degrees, the film thickness at the edge portion is thick.

In addition, when the substrate 1 is turned over and printed on the other side, the through-hole edge 7 portion where the film thickness has become thinner is formed as a thick edge portion for the same reason, and the edge obtained by this method is The thickness of the through-hole edge portion was 40 μm, whereas the thickness of the through-hole edge portion obtained by printing a conductor on the substrate surface using a conventional method was only 4 μm.

In the manner described above, a thick film circuit board was obtained in which the front and back sides were electrically connected through the thick film through holes.

[Effects of the Invention] As explained above, in order to satisfy solder resistance, in the past, apart from printing the conductor part, only the through-hole part was printed one on each side.
Compared to the conventional method of printing 42 times, according to the method for forming thick film through poles of the present invention, it is possible to reduce the number of printings by 2 times when producing a thick film circuit board, and It has great economic effects, such as reducing board costs by 5% and manufacturing lead time by 10%.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view for explaining a method of forming a thick film through hole in an embodiment of the present invention. FIG. 2 is an enlarged sectional view showing the state of a through-hole portion immediately after conductor printing in the method of the present invention. FIG. 3 is a schematic cross-sectional view for explaining a conventional method of forming a thick film through hole. FIG. 4 is an enlarged cross-sectional view showing the state of a through-hole portion immediately after conductor printing in a conventional method. Explanation of symbols 1...Alumina board 2...Through hole] 0 3...Through hole board 4...Printed conductor 5...Suction hole 6...Printing machine bed Part 7: Through hole on the front side 8: Through hole on the back side Edger edge Patent applicant Taiyo Yuden Co., Ltd. Representative Patent attorney Masahiko Maruoka

Claims (1)

[Claims] Holes for through-holes that communicate with the front and back sides of the insulating substrate are formed, and the through-hole plate is used as a stand when printing a conductive film on the substrate. After creating a downward suction air flow and printing a conductive paste for conductor circuits on the conductor part and through-hole part of the board, dry and bake the board and print on the conductor part and through-hole part. In a method for forming a thick film through hole that involves baking a conductor, the hole has a diameter smaller than that of the through hole provided in an insulating substrate, and the hole is aligned with the hole for the through hole. A perforated plate or an air-permeable plate that allows air to freely pass through is used as a through-hole plate for mounting an insulating substrate, and after printing a conductive film in this way, the insulating substrate and through-hole plate are used. Without separating the hole plate,
A method for forming a thick film through hole, which comprises drying the conductive paste, separating the insulating substrate from the through hole plate, and firing the insulating substrate.