JPS63188994A - Method of forming thick film through-hole - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] In a method of forming a thick film through hole by a suction printing method, the opening area of the large diameter pilot hole of the thick film through hole is made substantially the same as the opening area of the small diameter pilot hole. By connecting and attaching a tongue piece to a part of the inner wall surface of the large-diameter prepared hole and forming an opening surrounded by an arc, even if large and small-diameter prepared holes are mixed, it can be attached to the inner wall surface of the hole at the same time. This allows the conductive paste to be uniformly applied by suction.

[Industrial application field]

The present invention relates to a method for forming thick film through holes in circuit boards, such as thick film hybrid integrated circuit boards.

When forming thick film through holes on a circuit board using thick film technology, the diameter of the thick film through hole for the purpose of simply connecting patterns on both sides of the board is usually 0.3 mm.
~0.6 mm, and in the case of this small diameter pilot hole, print the conductive paste to form a pattern while suctioning and venting from the opposite side of the printed surface, and apply the conductive paste to the inner wall surface of the through-hole pilot hole by suction. It can be applied uniformly by a so-called suction printing method that forms thick film through holes.

On the other hand, the diameter of the thick film through hole into which the mounted component glue dowel is inserted and connected is usually large, 0.8 mm to 1.2 mm, and in circuit boards that have both large and small diameter prepared holes, it is difficult to use conductive paste. The suction conditions are adjusted to those common to large and small diameter pilot holes, and the coating is applied separately in several steps depending on the type of pilot hole, but the film thickness on the large diameter pilot hole becomes uneven. easy.

Under these circumstances, even in the case of large-diameter pilot holes, it is possible to apply suction uniformly, and even in the case of a mixture of large and small-diameter pilot holes, a thick film can be formed at the same time with one suction application, improving work efficiency and yield. There is a need for a method of forming thick film through holes.

[Conventional technology]

Conventionally, as shown in the perspective view of a circuit board in FIG. 4, in the case of a circuit board 11 in which thick film through holes have both large and small diameter pilot holes, for example, a ceramic circuit board, large and small diameter pilot holes 12 are used.
a, 12b The conductive paste is applied to the inner wall surface of the hole by suction in two separate steps using a suction printing method.

That is, as shown in the perspective view of FIG. 5(a) and the cross-sectional view of FIG. ,
An auxiliary plate 13 is prepared in which a suction hole 13a slightly larger than the diameter of the large-diameter pilot hole 13a is bored, which is sufficient to absorb machining errors in the hole diameter and hole position of the large-diameter pilot hole 12a.

The circuit board 11 is placed on this auxiliary plate 13, and the suction hole 13a is
and the large-diameter pilot hole 12a of the circuit board 11, and close the small-diameter pilot hole 12b.

In this state, a conductive paste is printed on the surface of the circuit board 11 while suctioning and venting in the direction opposite to the printed surface, that is, in the direction of the downward arrow on the auxiliary plate 13, to form the land llb of the large-diameter pilot hole 12a. Apply the conductive paste above by suction.

Next, as shown in the perspective view of FIG. 6(a) and the cross-sectional view of FIG. 6(b), as a second step, the small-diameter prepared hole 12b of the thick film through hole has a small diameter of 0.6n+. Another auxiliary plate 14 having a suction hole 14a slightly larger than the diameter of the pilot hole 12b is prepared.

On this auxiliary plate 14, the circuit board 11 on which the conductor paste has been suction-coated into the large-diameter pilot hole 12a is placed, the suction hole 14a and the small-diameter pilot hole 12b are aligned, and the large-diameter pilot hole 12a is closed.

In this state, conductive paste is printed on the surface of the circuit board 11 while suctioning and venting on the opposite side of the printed surface, that is, in the downward arrow direction of the auxiliary plate 14, and connects the land Ilb of the small diameter pilot hole 12b and the wiring pattern lla. The conductive paste is applied onto the prepared hole 12b by suction.

Through the above two steps, the conductive paste is suction applied to the large and small diameter pilot holes 12a and 12b, and then fired to complete the thick film through hole 12.

[Problem that the invention seeks to solve]

However, according to the above method, the thick film forming process requires the same number of steps as the number of hole diameter types, so it takes a very large number of man-hours. A suction force is obtained by the suction speed, resulting in a uniform film thickness, but when the diameter of the lower hole exceeds about 0.8 tsuru, the flow velocity near the inner wall of the hole decreases, and the film thickness tends to become uneven. , When processing circuit boards with a mixture of small-diameter pilot holes in one process, it is difficult to adjust the flow rate of the airflow passing through the pilot holes, and the suction speed may vary depending on the size of the pilot holes. Therefore, the amount of conductive paste sucked varies depending on the diameter, and there is a problem that the thickness of the through-hole is likely to be unevenly coated.

The present invention provides a method for forming thick film through holes that solves the above problems.

[Child actor to solve problems]

The above-mentioned problem with the conventional structure is that a tongue piece that makes the opening area of the large-diameter pilot hole of the thick film through hole substantially the same as the opening area of the small-diameter pilot hole is connected to a part of the inner wall surface of the large-diameter pilot hole. After applying the conductive paste to the inner wall surface of the hole including the area around the tongue piece and the large-diameter pilot hole using a suction printing method, after drying, the tongue piece is cut off at the connecting part and fired. solved by.

[Effect]

By adjusting the area of the tongue piece attached to the pilot hole of the thick film through hole, the suction speed of the conductive paste can be adjusted, and the airflow flowing on the inner wall of the hole can be made into a laminar flow to ensure uniform suction to the conductive paste during pattern printing. By applying force, thixotropy (T
A predetermined amount of suction can be sucked into the opening using the HIXOTROR'Y, and the conductive paste can be uniformly applied to the inner wall surface.

〔Example〕

The gist of the present invention will be explained in detail below based on embodiments shown in the drawings.

FIG. 1 (al), (b), (C) are plan views showing the process order.

FIG. 1(a) shows the first step, in which the thick film through hole 2 has a large-diameter pilot hole 2a with a hole diameter of 0.8 m to 1.2 inches, and 0.8 m to 1.2 inches.
．． In a circuit board 1 having a mixture of small-diameter prepared holes 2b of 31- to 0.6 fins, for example, a ceramic circuit board, large-diameter prepared holes 2a are mixed.
The area is surrounded by a circular arc, which is a feature of the present invention, that is, the opening 2a-2 has a crescent shape 2a-2a, and the tongue piece 2a-1 formed by laser beam processing, for example, is formed by a large-diameter pilot hole. By connecting and attaching it to a part of the inner wall surface of the hole 2a, the opening area is substantially the same as the opening area of a hole having a diameter of 0.6 mm.

The small diameter pilot hole 2b has the same area.

That is, the size of each tongue piece 2a-1 is adjusted according to the diameter of the large-diameter lower hole 2a of each bladder, so that the flow velocity approaches the flow rate passing through the small-diameter lower hole 2b, and all large and small-diameter lower holes 2a are adjusted. , 2b,
The opening 2a-2 is formed so that the flow rate is adjusted to be approximately constant, and suction application can be performed under the suction conditions of the small-diameter lower hole 2b.

Next, in FIG. 1 (bl indicates the second step, the small diameter pilot hole 2b
The surface of the circuit board 1 (on the paper side), which has a mixture of large-diameter prepared holes 2a with tongue pieces as described above, is printed by suction printing from the bottom opposite to the printed surface (on the paper side). ) to form a wiring pattern 1a and a land 1b, and the conductive paste on the prepared holes 2a and 2ba is sucked and applied to the inner wall surface of the hole and dried.

Next, FIG. 1(C) shows the third step, in which all the tongue pieces 2 are
After cutting a-1 at the connecting portion, it is fired to complete the thick film through hole 2.

Incidentally, as shown in FIG. 2, a notch 28-3 is made in the connecting portion of the tongue piece 2a-1 so that it can be easily removed in the next step.

Furthermore, although no thick film is formed on the cut-off portion of the tongue piece 2a-1, the formed thick film portion can be used for sufficient conductive connection.

As shown in FIG.
It goes without saying that there is no problem even if the opening area is made small by forming the opening 2a-2 in -2b or U-shape 2a-2c.

〔Effect of the invention〕

As described in detail above, according to the present invention, even in large-diameter pilot holes, a uniform film thickness similar to that in small-diameter pilot holes can be formed, and even circuit boards with both large and small-diameter pilot holes can be coated in one printing process. Since thick films can be formed using this process, work efficiency and yield are improved, and highly reliable circuit boards can be obtained, which is extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the process order of one embodiment according to the present invention, Fig. 2 is a perspective view showing the incision of the connecting portion of the tongue according to the present invention, and Fig. 3 is a plan view showing another embodiment according to the present invention. A plan view, FIG. 4 is a perspective view showing a circuit board with a mixture of large and small diameter prepared holes according to the prior art, FIG. 6(a) and 6(b) are a perspective view and a cross-sectional view showing the second step according to the prior art. In the figures, 1 is a circuit board, 1a is a wiring pattern, 1b is a land, and 2 is a thick film through. Hole, 2a is a large diameter pilot hole, 2b is a small diameter pilot hole, 2a-1 is a tongue piece, 2a-2 is an opening, 2a-2a is crescent-shaped, 2a-2b is C-shaped, 2a-2c is U-shaped, 2a-3 indicates a cut.First step (al) Second step (bl Third step (C1) A plan view showing the process order of an embodiment according to the present invention.
figure

Claims (1)

[Claims] In a method of forming thick film through holes with different hole diameters on a circuit board by a suction printing method, the opening area of the large diameter pilot hole (2a) of the thick film through hole (2) is compared with the small diameter pilot hole (2b).
) The tongue piece (2a-1
) is connected to a part of the inner wall surface of the large diameter pilot hole (2a), and then the area including the tongue piece (2a-1) and the periphery of the large diameter pilot hole (2a) is printed using the suction printing method. A thick film through hole characterized in that a conductive paste is applied to the inner wall surface of the hole by suction, and after drying, the tongue piece (2a-1) is cut off at the connecting part and fired to complete the thick film through hole (2). How to form a hole.