JP3695769B2 - Method for manufacturing thick film circuit board - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for manufacturing a thick film circuit board, and more particularly, to a method for manufacturing a thick film circuit board including first and second conductor wirings connected through through holes formed in an insulating layer.
[0002]
[Prior art]
In recent years, a thick film circuit board on which electronic components are mounted is required to have a high density, and the number of layers is increasing.
The multilayered thick film circuit board includes, for example, an insulating substrate, a lower conductor wiring formed on one surface of the insulating substrate, an insulating layer formed on one surface of the insulating substrate so as to cover the lower conductor wiring, And a second conductor wiring formed on the layer. A through-hole having a diameter of 300 to 700 μm is formed in the insulating layer, and a via-hole conductor that connects the lower conductor wiring and the upper conductor wiring is formed in the through-hole.
[0003]
In order to form the thick film circuit board, first, a copper paste to be a lower conductor wiring is applied on an insulating substrate. Subsequently, a paste to be an insulating layer is applied on the insulating substrate. At this time, a through hole is formed at a predetermined position in the insulating layer. Further, the insulating layer is dried at 100 to 150 ° C. and fired at 900 ° C. Next, the via-hole conductor is printed and fired, and a copper paste to be the upper conductor wiring is applied on the insulating layer. At this time, the upper conductor wiring is connected to the first conductor wiring through a through hole formed in the insulating layer. The entire substrate is baked at a high temperature of about 900 ° C.
[0004]
[Problems to be solved by the invention]
In the conventional method for manufacturing a thick film circuit board, after applying a paste material to be an insulating layer, the paste material before drying may fall inside the through hole and close the through hole. In this case, poor conduction occurs between the upper conductor and the lower conductor.
An object of the present invention is to reduce poor conduction between conductors.
[0005]
[Means for Solving the Problems]
A method of manufacturing a thick film circuit board according to the present invention includes an insulating substrate, a first conductor wiring formed on one surface of the insulating substrate, and a predetermined position formed on one surface of the insulating substrate so as to cover the first conductor wiring. And a second conductor wiring that is formed on the insulating layer and connected to the first conductor wiring through the through hole. This manufacturing method includes a first conductor wiring forming step, a connecting conductor portion forming step, an insulating layer forming step, and a second conductor wiring forming step.
[0006]
In the first conductor wiring forming step, a first conductor wiring is formed on the one surface of the insulating substrate. In the connecting conductor portion forming step, the connecting conductor portion is formed at the predetermined position on the first conductor wiring. The insulating layer forming step is performed by applying the insulating paste a plurality of times by screen printing so that the connecting conductor portion is located in the through hole and the diameter of the through hole is increased according to the upper layer. An insulating layer is formed on the one surface of the insulating substrate. In the second conductor wiring forming step, the second conductor wiring is formed on the insulating layer so as to be connected to the connecting conductor portion through the through hole.
[0007]
[Action]
In the method of manufacturing a thick film circuit board according to the present invention, the connecting conductor portion is formed on the first conductor wiring before the insulating layer, and the insulating layer is formed on the insulating substrate so that the connecting conductor portion fits into the through hole. Form. Accordingly, the connection conductor portion can be prevented from being cut off, and the conduction failure between the first conductor wiring and the second conductor wiring is reduced.
[0008]
【Example】
A thick film circuit board 1 shown in FIG. 1 has electronic components mounted thereon, an insulating substrate 2, a lower conductor wiring 3 formed on the upper surface of the insulating substrate 2, and a lower conductor wiring 3 on the upper surface of the insulating substrate 2. The insulating layer 4 is formed so as to cover the upper surface, and the upper conductor wiring 5 is formed on the insulating layer 4. Through holes 4 a (diameter 300 to 500 μm) are formed at a plurality of predetermined positions of the insulating layer 4, and via-hole conductors 6 filled in the through holes 4 a connect the lower conductor wiring 3 and the upper conductor wiring 5. are doing. The diameter of the through hole 4a increases as it goes upward.
[0009]
The insulating substrate 2 is a rectangular substrate made of alumina, AlN, mullite, or the like. The lower conductor wiring 3, the upper conductor wiring 5, and the via-hole conductor 6 are formed by firing a copper paste (for example, DP9153 manufactured by DuPont). The insulating layer 4 is obtained by drying a paste material (for example, dielectric paste AP5815 manufactured by Asahi Glass Co., Ltd.).
[0010]
Next, a method for manufacturing the thick film circuit board 1 will be described.
First, as shown in FIG. 2, an insulating substrate 2 made of, for example, alumina, AlN, mullite or the like is prepared. Next, as shown in FIG. 3, a copper paste to be the lower conductor wiring 3 is applied on the insulating substrate 2 by screen printing. And as shown in FIG. 4, the copper paste (diameter 300-500 micrometers) used as the via-hole conductor 6 is formed on the lower conductor wiring 3 by performing screen printing several times. A plurality of via hole conductors 6 are formed so as to coincide with the positions where the through holes 4a of the insulating layer 4 are formed when completed. Each via-hole conductor 6 extends upward in the figure.
[0011]
Further, as shown in FIG. 5, an insulating paste to be the insulating layer 4 is applied to the upper surface of the insulating substrate 2 by screen printing. The insulating paste is applied a plurality of times. As shown in FIG. 6, the first layer 4 </ b> A, the second layer 4 </ b> B, and the third layer 4 </ b> C are formed on the lower conductor wiring 3. The insulating layer 4 covers the lower conductor wiring 3, but a through hole 4 a is formed at a position corresponding to the via hole conductor 6, and the via hole conductor 6 is fitted into the through hole 4 a.
[0012]
As described above, since the via-hole conductor 6 is formed before the insulating layer 4, it is difficult to block the through-hole 4a even if the paste material hangs down inside the through-hole 4a. Furthermore, since the diameter of the through hole 4a is set so as to increase according to the upper layer, the upper part of the through hole 4a is unlikely to hang down inward.
[0013]
Next, the insulating substrate 2 is put in a drying furnace, and the insulating layer 4 is dried at 100 to 150 ° C.
On the insulating layer 4 after drying, a copper paste to be the upper conductor wiring 5 is applied by screen printing. At this time, the upper conductor wiring 5 is connected to the via-hole conductor 6 through the through hole 4a. Here, since the through-hole 4a is not blocked by the dripping of the paste material, the conduction failure between the upper conductor wiring 5 and the lower conductor wiring 3 is reduced.
[0014]
Finally, the insulating substrate 2 is baked at a high temperature of about 900 ° C. in a non-oxidizing atmosphere. Thereby, the thick film circuit board 1 is completed.
[Experimental example]
Thick film circuit boards were manufactured by the conventional manufacturing method and the manufacturing method according to the present invention, and the conductor defect rates of the two were compared. In this experiment, 100 via hole conductors having a diameter of 300 μm were formed on the lower conductor wiring. The presence / absence of conduction was measured with an insulation resistance meter, and 10 ⁹ Ω or more was considered to be good conduction. In the conventional manufacturing method, the conduction failure rate is 6%, and in the production method according to the present invention, the conduction failure rate is 0%.
[Other Examples]
In the above embodiment, the insulating layer 4 is formed in three layers, but the present invention can also be adopted in four or more layers.
[0015]
【The invention's effect】
In the method of manufacturing the thick film circuit board according to the present invention, the connecting conductor portion is formed on the first conductor wiring before the insulating layer, so that the connecting conductor portion is not easily cut off, and the first conductor wiring and the second conductor wiring are formed. Reduces the continuity of electrical connection.
[Brief description of the drawings]
FIG. 1 is a schematic vertical sectional view of a thick film circuit board manufactured according to an embodiment of the present invention.
FIG. 2 is a view showing one stage of a manufacturing process of a thick film circuit board.
FIG. 3 is a view showing one stage of a manufacturing process of a thick film circuit board.
FIG. 4 is a view showing one stage of a manufacturing process of a thick film circuit board.
FIG. 5 is a view showing one stage of a manufacturing process of a thick film circuit board.
FIG. 6 is a view showing one stage of a manufacturing process of a thick film circuit board.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thick film circuit board 2 Insulating board 3 Lower conductor wiring 4 Insulating layer 4a Through-hole 5 Upper conductor wiring 6 Via-hole conductor

Claims (1)

An insulating substrate; a first conductor wiring formed on one surface of the insulating substrate; an insulating layer formed on the one surface of the insulating substrate so as to cover the first conductor wiring and having a through hole at a predetermined position; A method of manufacturing a thick film circuit board comprising a second conductor wiring formed on the insulating layer and connected to the first conductor wiring through the through-hole,
A first conductor wiring forming step of forming the first conductor wiring on the one surface of the insulating substrate;
A connecting conductor portion forming step of forming a connecting conductor portion at the predetermined position on the first conductor wiring;
By applying the insulator paste a plurality of times by screen printing, the connecting conductor portion is positioned in the through hole, and the diameter of the through hole is increased according to the upper layer, the insulating layer is Forming an insulating layer on the one surface of the insulating substrate;
A second conductor wiring forming step of forming the second conductor wiring on the insulating layer so as to be connected to the connecting conductor portion through the through hole;
Of manufacturing a thick film circuit board.

Images