JPS6053097A - Method of forming conductor in 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 The present invention relates to a method for forming conductors in through holes in the production of thick film circuits that can be used in radios, televisions, video tape recorders, and the like.

Conventional structure and problems thereof FIG. 1 shows an example of a thick film circuit. The thick film paste printed on the alumina substrate 1 is dried and fired to form a thick film conductor layer 2. A thick film resistor 3 is formed. Thick film paste for conductors is generally composed of silver-radium alloy powder, glass frit, resin binder, organic solvent, etc. Further, the thick film paste for the resistor is composed of silver-palladium paste and ru δnium oxide, and the other components are substantially the same as the paste for the conductor. On the alumina substrate 1, a chimp capacitor 4 is connected to a thick film conductor layer 2 by solder 5.
is connected to. With the recent demand for smaller electronic devices, there is an increasing need for circuit boards used there to be smaller and more highly integrated. Therefore, instead of the conventional general board that utilizes only one side as shown in Fig. 1, it is possible to effectively use both sides of the board by using a thick film conductor layer 2 formed in the through holes 6 in the alumina substrate 1 as shown in Fig. 2. Double-sided thick film circuits have come into use.

The conventional manufacturing process for double-sided thick film circuits is 0.5M to 0.6A.
In order to form a conductive circuit on the substrate with good print accuracy without bleeding using a conductive paste containing silver-palladium metal powder on the alumina substrate 1 of N, the viscosity is 2,100-2,500.
Screen printing was done using Hoiz's relatively high viscosity paste. The main printing conditions at that time are generally as follows.

(1) Screen: 360-400 mesh (2) Screen material: stainless steel (3) Screen emulsion thickness: 10-2 Qμfn (4) Squeegee speed: 10-15 C/n/sec Next, apply the printed paste After drying, a through hole portion is printed inside the through hole having a diameter of 0.5φ to 0.6φ with a viscosity lower than that of the paste. This is because if screen printing is performed inside the through holes at a relatively high viscosity (112,100 to 2,500 poise, which is used for printing conductor circuits on the board), the through ball formation yield will be poor. It is necessary to screen print with a low viscosity paste to improve the quality. Furthermore, if the conductive circuit portion on the substrate and the inside of the through hole are simultaneously formed using a low viscosity paste, bleeding will occur in the conductive circuit portion on the substrate.

In other words, the printing of the conductive circuit portion on the board and the printing inside the through-holes were formed in separate processes using pastes with different viscosities, resulting in a problem of long processes and poor productivity.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned drawbacks and simultaneously prints the conductor circuit portion on the substrate and coats the conductor inside the through-hole, thereby shortening the process and improving productivity.

Structure of the Invention The present invention provides a screen that is placed on one side of a substrate having through holes, and a conductive paste on the screen that is coated with cedar.
This is a method for forming a conductor in a through-hole, in which a paste is placed on the substrate by moving a conductor, and a paste is applied inside the through-hole by vacuum suction from the opposite side of the substrate.

Description of examples An embodiment of the present invention will be explained with reference to FIG.

Board size 90 ma Le* -/lz 6
(silver-palladium based)
The conductor width is 0.2M or more by changing the viscosity of 10 and using a 36o mesh stainless steel screen 11.
Screen printing was performed on the on-board conductor circuit portion 12 with a conductor spacing of 0.2 mm or more and the inside of the through hole 13.

Note that the paste viscosity was measured under the following conditions.

(1) Measuring device Nireopexy analyzer (manufactured by Oiki Seisakusho) (2) Measuring method: Cone & plate (3) Cone angle: 1.57 degrees (4) Cone diameter: 6c1n (5) Plate rotation speed: 1 r, p, m (6) Measurement temperature: 25° C. As a result, the lower the paste viscosity, the better the through hole formation yield. However, if the viscosity of the paste is too low, smearing occurs in the conductive circuit portion on the substrate, resulting in poor printability. In other words, when the paste viscosity of the first example is 900 voids or less,
In Example 1 of the second to fourth examples in which bleeding occurred in the conductor circuit portion on the substrate, the through hole formation yield was 100% and good printability was obtained at OOO to 2.000 poise. Further, at 2,100 poise or more in the fifth and sixth embodiments, the printability of the conductive circuit portion on the substrate is good, but the through hole formation yield is poor at 90% or less because of the high viscosity. Inn◆
Table 2 below shows the squeegee speed, through hole formation yield, and printability.

This shows that the slower the squeegee speed is, the longer the vacuum suction time is, but the paste is sufficiently coated inside the through holes, so the through hole formation yield is improved.

As shown in Examples 7 to 10 of Table 2, the through hole formation yield was 100% when the squeegee speed was 8 crn/sec or less.
Good results were obtained.

In addition, as in Examples 11 and 12, when the squeegee speed is 9 fps/sec or more, productivity improves, but the through-hole formation yield deteriorates to 90% because there is not enough time for the conductive paste to coat inside the through-holes. .

Note that screen printing was performed on alumina substrates having through-hole diameters of 0.7 φm and 0.8 φm under the same conditions as described above, and similar results were obtained.

Table 1 Table 2 Effects of the Invention As described above, according to the present invention, the on-board conductor circuit portion and the inside of the through hole can be formed at the same time, thereby shortening the process and improving productivity.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of a thick film circuit, FIG. 2 is a sectional view showing a thick film circuit using both sides of a substrate, and FIG. 3 is a sectional view of an apparatus implementing an embodiment of the present invention. be. 1...Alumina substrate, 6...Through hole, 7...Suction jig, 8...Suction port, 9...
...Squeegee-110...Silver-palladium paste, 11...Screen, 12...Conductor circuit section, 13...Through hole inside. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (3)

[Claims] (1) Place a screen on one side of the substrate with through holes, and squeegee the conductive paste on this screen.
A method for forming a conductor in a through-hole, in which a conductive paste is applied onto the substrate by moving the conductive paste, and a conductive paste is applied inside the through-hole by vacuum suction from the opposite side of the substrate. (2) The viscosity of the conductive paste is between 1.00 and 2.00. O
A method for forming a conductor in a through-hole according to claim 1, wherein the through-hole conductor is o○ voids. (3) The method for forming conductors in through-holes according to claim 1, wherein the squeegee movement speed is 8 F/sec or less.