JPH088506A - Through hole double-sided board - Google Patents

Abstract

PURPOSE:To eliminate contact failure caused by an increase in conductor resistance and disconnection on upper and lower ends of a through hole. CONSTITUTION:A through hole 2 penetrating a ceramic board 1 is provided, and an upper conductor 3 formed on the upper surface of the board 1 and a lower conductor 4 formed on the lower surface of the board 1 are brought into contact via the through hole 2. The through hole 2 is inclined in relation to the board 1, and the inclination is limited within a range of 35-55 deg. to a plane perpendicular to the board. Since at least a part of end portions at upper and lower apertures of the through hole 2 has an obtuse angle, the thickness of this part can be made sufficiently large, thus preventing disconnection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a through-hole double-sided board in which circuit conductors provided on both sides of a ceramic board are connected through through-holes. Such a through-hole double-sided board is used as a circuit board or the like in a hybrid IC product.

[0002]

2. Description of the Related Art When conductor wiring is provided on both sides of a ceramic substrate, a through hole penetrating the ceramic substrate is generally provided to secure a connection between the conductors provided on the upper and lower surfaces of the substrate (for example, Japanese Patent Laid-Open No. Hei 4). -206990, etc.). An example of such a through-hole double-sided board is shown in FIG. 8. A plurality of through-holes 2 penetrating the ceramic board 1 are formed at predetermined locations, and the upper conductor 3 formed on the upper surface of the board 1 is the through-hole. It is connected to the lower conductor 4 on the lower surface side of the substrate via 2 (FIG. 9).

The through holes 2 are formed by punching an unfired ceramic green sheet placed on a holding table with a pin-shaped punching tool, and then firing the substrate 1.
And Next, the upper conductor 3 is printed and fired while sucking vacuum in the through hole 2 portion, and the substrate 1 is inverted to form the lower conductor 4 on the lower surface thereof by the same process. As a result, the conductors 3 and 4 are overlapped with each other on the inner peripheral wall of the through hole 2 and can be electrically connected.

[0004]

However, in the above-mentioned conventional structure, as shown in FIG. 9, the film thickness of the conductors 3 and 4 at the edge portions 21 of the through holes 2 opened on the upper and lower surfaces of the substrate 1 is increased. Becomes extremely thin, increasing the conductor resistance,
Alternatively, there is a possibility that contact failure may occur due to disconnection.
This is because it is not easy to make the film thickness of the conductor paste to be applied sufficiently thick due to the flow of the conductor paste because the above-mentioned edge portion 21 of the through hole 2 is a right angle, and the conductor paste is dried after the application. Due to contraction.
For this reason, the conductor paste is usually applied twice to increase the film thickness, but the process is complicated and the sufficient effect cannot be always obtained.

However, according to the present invention, the film thickness of the upper conductor and the lower conductor formed on the upper and lower surfaces of the substrate is increased in a simple process to surely connect them to each other, thereby increasing the conductor resistance and making contact due to disconnection. The purpose is to eliminate defects such as defects.

[0006]

In order to solve the above problems, the through-hole double-sided board of the present invention has a through-hole 2 penetrating a ceramic substrate 1 as shown in FIG. The first conductor 3 formed on the upper surface of the substrate 1 and the second conductor 4 formed on the lower surface of the substrate 1 are in contact with each other via. The through hole 2 is inclined with respect to the substrate 1, and its inclination angle α is in the range of 35 to 55 ° with respect to the plane perpendicular to the substrate 1.

[0007]

In the above structure, since the through hole 2 is inclined, at least part of the upper and lower opening edges of the through hole 2 has an obtuse angle (shown as arrows a and b in FIG. 1). Therefore,
At least in this portion, the conductor paste can be easily applied and the conductor film thickness can be made sufficiently thick, so that contact failure or the like due to disconnection can be prevented. Further, the first conductor 3 and the second conductor 4 have an overlap in the through hole 2 and are electrically connected.

[0008]

1 is a cross-sectional view of a through-hole double-sided board of the present invention. In the figure, an alumina substrate 1, which is a ceramic substrate, has through holes 2 penetrating the substrate 1 at appropriate places.
Is formed. The through hole 2 penetrates the substrate 1 obliquely, and its inclination angle α is 35 ° or more with respect to a plane perpendicular to the substrate 1. By setting the inclination angle α of the through hole 2 to be 35 ° or more, in the upper and lower openings of the through hole 2, a part of the peripheral edge portion shown by arrows a and b in the figure becomes a gentle inclination continuing from the surface of the substrate 1, It is possible to prevent conductor breakage. Inclination angle α is 3
If it is less than 5 °, the conductor film thickness at the peripheral portion cannot be made sufficiently thick, and there is a risk of disconnection, which is not preferable. Although the possibility of wire breakage decreases as the inclination angle α increases, it is difficult to form when the space is insufficient, and it is not practical. Therefore, it is preferably 35 ° to 55 °.
It is good to set it in the range of °.

Further, at the upper end opening edge of the through hole 2,
The position facing the gentle slope portion indicated by the arrow a is a curved surface portion 22 that continues smoothly from the surface of the substrate 1, and the conductor paste can be evenly applied onto the curved surface portion 22. Thus, the upper end opening of the through hole 2 can secure a sufficient film thickness over almost the entire circumference, and can prevent problems such as disconnection.

An upper conductor 3 serving as a first conductor is formed on the upper surface of the substrate 1, while a conductor 4 serving as a second conductor is formed on the lower surface of the substrate 1, and both conductors 3 and 4 are through holes 2 It enters inside and covers the inner wall surface from above and below, and has an overlap in the vicinity of the middle part and is electrically connected. In the figure, 5 is a resistor.

A method of forming the through hole 2 having the above shape will be described below. In FIG. 2, the holding table 6 has an inclination angle β of 35 ° or more, and the unfired alumina green sheet 11 is placed thereon. The punching tool 7 has a pressing surface parallel to the surface of the green sheet 11 and a pin-shaped punching portion 71 that vertically projects downward from the pressing surface. The punching portion 71 has a base end part of the curved surface of the through hole 2. It is formed into a curved surface corresponding to the portion 22. Using the punching tool 7, the green sheet 11 is pressed from above, and the punching portion 71 is pressed.
Through, the green sheet 11 is punched obliquely to form the through hole 2 having the curved surface portion 22 (FIG. 3). The scraps escape downward through the holes 61 provided in the holding table 6 (FIG. 2).

The green sheet 11 having the through holes 2 is then fired at 1500 to 1600 ° C. to form the substrate 1, and then the upper conductor 3 is further formed on the upper surface (FIG. 4). As the conductor material, gold, silver, copper, silver-palladium, silver-platinum, or the like can be used. After the conductor paste is printed and dried by vacuum suction from the lower surface of the substrate by a normal thick film forming method, 800 to Bake at 950 ° C. The film thickness is 7 to 15 μm. The upper conductor 3 thus formed enters the through hole 2 and mainly covers the upper half of the inner wall surface thereof. Here, the upper opening edge of the through hole 2 has an obtuse angle as shown by an arrow a, and since the curved surface portion 22 is formed at this facing position, at least these portions have an upper portion. The film thickness of the conductor 3 can be made sufficiently thick.

Thereafter, in the same manner, a conductor paste is printed on the lower surface of the substrate 1 and fired to form the lower conductor 4. In the through hole 2, the lower conductor 4 mainly covers the lower half of the inner wall surface of the through hole 2, and the portion shown by the arrow b at the lower end opening has an obtuse angle, so that a thick film can be formed in this portion. It should be noted that the portion indicated by arrow c has an acute angle and thus the film thickness may be thin, but since conduction can be secured at the facing portion b, contact failure or the like does not occur. The upper conductor 3 and the lower conductor 4 overlap each other in the through hole 2 as shown in FIG. 5, and the overlap can be thickened especially on the inner wall surface below the curved surface portion 22, so that the conductors 3 and 4 can be reliably connected. You can

Although the curved portion 22 is formed at the upper opening edge of the through hole 2 in the above embodiment, the curved portion 22 does not necessarily have to be provided. In this case, as shown in FIGS. 6 and 7, a portion having an acute angle also occurs at the upper opening edge, but since the right half portion shown by the thick line in FIG. 6 has an obtuse angle, no disconnection occurs at this portion. The same applies to the lower end opening, and the left half portion shown by the thick line in FIG. 6 has an obtuse angle. Then, the upper conductor 3 and the lower conductor 4 are surely connected in the through hole 2 to ensure conduction.

In the present embodiment, an example of an alumina substrate was described as the ceramic substrate, but other than this, various substrates such as aluminum nitride, silicon carbide, beryllia, glass ceramics, etc. may be used as the ceramic substrate. Can be used.

[0016]

As described above, by adopting the through hole shape of the present invention, the conductor film thickness at the upper and lower edges of the through hole can be made sufficiently thick. Therefore, it is possible to prevent the occurrence of contact failure due to increase in conductor resistance and disconnection, and reliability is improved. Further, the labor such as double coating of the conductor paste can be saved and the manufacturing process can be simplified.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional view of a through-hole double-sided board according to an embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a manufacturing process of a through-hole double-sided board.

FIG. 3 is a partially enlarged sectional view of a green sheet having a through hole formed therein.

FIG. 4 is a partially enlarged sectional view of a through-hole double-sided board having conductors formed on both sides.

5 is a sectional view taken along line VV of FIG.

FIG. 6 is a plan view of a through-hole double-sided board according to another embodiment of the present invention.

7 is a sectional view taken along line VII-VII in FIG.

FIG. 8 is an overall perspective view of a conventional through-hole double-sided board.

9 is a partially enlarged sectional view of a conventional through-hole double-sided board, which is a sectional view taken along line IX-IX of FIG.

[Explanation of symbols]

 1 Ceramic Substrate 2 Through Hole 22 Curved Surface Part 3 Upper Conductor (First Conductor) 4 Lower Conductor (Second Conductor) 5 Resistor 6 Holding Base 7 Punching Tool

Claims (1)

[Claims] 1. A through hole having a through hole penetrating a ceramic substrate, and a first conductor formed on the upper surface of the substrate and a second conductor formed on the lower surface of the substrate are in contact with each other through the through hole. A double-sided hole through-hole substrate, wherein the through-hole is inclined with respect to the substrate and the inclination angle thereof is within a range of 35 to 55 ° with respect to a plane perpendicular to the substrate. substrate.