JPH0586879B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method of manufacturing a hybrid IC substrate, particularly a through-hole printing method.

Conventional configuration and its problems 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 and a thick film resistor 3. Thick film pastes for conductors are generally composed of silver-palladium alloy powder, glass frit, resin binder, organic solvent, etc. Thick film pastes for resistors use ruthenium oxide instead of silver-palladium, and others are for conductors. It consists of something almost the same as paste. A chip capacitor is connected to the thick film conductor layer 2 by solder 5 on the alumina substrate 1 . With the recent demand for downsizing of electronic devices, there is an increasing need for circuit boards included therein to be downsized and highly integrated. Therefore, from the conventional general board using only one side as shown in FIG. 1, to the one shown in FIG. Effective use of double-sided thick film circuits has come into use.

Conventionally, as shown in FIG. 3, the method of forming a conductive paste in a through hole involves applying a pressure of about 500 c.c./min through the hole to the alumina substrate 9, as shown by the arrow in the figure. There is a method of forming the planar circuit portion 13 and the through-hole internal conductor portion 14 by using the screen plate 10 and the rubber squeegee 12 to apply the conductive paste 11 while suctioning the conductive paste 11 with a vacuum cleaner. The problem in this case is that the suction jig 1 of the printing press is
When an alumina substrate 16 with holes is placed on top of the alumina substrate 16 and suction is applied as shown by the arrow in the figure, when suction is applied with strong pressure (500c.c./min) to enable through-hole printing at the same time as plane printing, Alumina substrate 1
6, the center part of the substrate is largely warped in the suction direction as shown by the broken line in the figure. As a result of experiments by the inventors, 100
□500C on a 96% alumina substrate of mm x 0.8tmm.
A warpage of approximately 0.5 mm was observed under suction pressure of C./min. As a result of the above warping, the screen gap between the screen plate and the substrate becomes larger than a set value during printing, resulting in large variations in printing thickness. As a result of experiments conducted by the inventors, under the above substrate size and printing conditions, the printing thickness was approximately 1.5 times the normal thickness in the central area where the warpage was particularly large, and defects such as printing smearing occurred frequently.

Two methods are currently being used to solve the above problems. Firstly,
As shown in FIG. 5, this is a method in which suction printing is performed using a printing table 17 which has holes drilled corresponding to the positions of the holes drilled in the alumina substrate 9 and having a somewhat larger diameter. In this case, although stable printing performance can be obtained, it is necessary to create, store, and manage the printing table each time the model is changed, which poses a big problem in terms of process and cost. The second method is to use the printing method shown in FIG. 3 as is. In this case, the viscosity of the conductor paste is reduced from the usual 150,000 cps to about 50,000 cps, and the suction force during printing is reduced to about 100 c.c./min (the board does not warp). In this case, it is possible to obtain good printability of the through-hole portion without changing the printing jig, etc., but the fine patternability of the flat printing portion formed at the same time is not possible (occurrence of bleeding, etc.). Therefore, when lowering the viscosity of the paste, a method is used in which the printing of the flat printing part and the printing of the through-hole part are performed in separate processes, which requires one additional cycle of printing and drying processes compared to the normal process. .

OBJECTS OF THE INVENTION The present invention solves the above-mentioned drawbacks and makes it possible to simultaneously perform printing on a good flat area and through-hole area.

Structure of the Invention The through-hole printing method of the present invention simultaneously prints on the flat surface of the substrate and applies paste to a part of the inside of the through-hole hole under a weak suction force, and then, before the paste dries, By suctioning with a stronger suction force than during printing, good flat printing and good paste application on the inner wall of the through hole can be easily obtained.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

It has a hole with a diameter of 0.6mm as shown in Figure 6A.
An alumina substrate 9 of 100□mm×0.8tmm is formed into a predetermined plane pattern 18 using a screen plate 10, a silver-palladium conductive paste 11 with a viscosity of 150,000 cps, and a rubber squeegee 12 under a suction force of 10 c.c./min. , paste 19 is applied to the upper part of the through hole.
Next, as shown in FIG. 6B, before the conductor paste dries (30 seconds after printing at room temperature), it is sucked in the direction of the arrow in the figure with a suction force of 200 c.c./min. As a result, it was possible to obtain a good plane printed part and a through-hole inner wall printed part.

In this embodiment, if the suction force during printing was too high, defects such as over-thick printing or bleeding near the center of the substrate in the flat printing section occurred as described in the problems of the conventional method. On the other hand, if the suction force during printing is too low, as shown in Figure 7, the amount of paste applied to the top of the through-hole during printing is too small, causing the inner wall of the through-hole to be coated with high suction after printing. Paste 14 could not be obtained in sufficient quantity.
The subsequent steps are in an oven at a temperature of 150℃.
After drying for 15 minutes, a conductor was printed on the other side in the same way as above, and after drying in the same way, it was fired in a continuous oven at 850℃ for 15 minutes to create a conductor circuit of a double-sided hybrid IC with electrical continuity between the front and back sides through through holes. This is a step of obtaining a formed substrate.

In the above embodiments, the formation of conductor circuits has been described, but the present invention can be similarly used when printing a cover coat on a substrate using a coating material mainly composed of epoxy resin or glass powder.

Effects of the Invention As described above, the through-hole printing method of the present invention has the following effects:
By simultaneously printing on the flat surface of the board and applying paste to a part of the inside of the through-hole hole under a low suction force, and then applying suction with a stronger suction force than during printing before the paste dries, This method does not require special jigs or increase the number of steps unlike the conventional method, and is a very effective method that allows for good print formation.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views showing an example of a hybrid IC, Figures 3, 4, and 5 are cross-sectional views showing conventional printing methods, and Figures 6A, B, and 7 are cross-sectional views of a conventional printing method. FIG. 1 is a sectional view showing an embodiment of the invention. 9... Board, 10... Screen version, 11...
Conductive paste material, 12...Squeegee, 13,1
8 conductor on plane printed part, 14... conductor on inner wall of through hole, 19... conductor coated on top of through hole.

Claims (1)

[Claims] 1. When printing through-holes to establish electrical continuity between the front and back surfaces by applying conductive paste to the inner wall of the hole drilled in the board, the through-holes are printed at the same time as a circuit is formed on the flat surface of the board under a low suction force. A through hole in which a conductive paste is applied to a part of the inside of the hole, and after the application is completed, the conductive paste is sucked downward from the applied surface through the hole with a stronger suction force than when forming the circuit, and the conductive paste is applied to the inner wall of the hole. Printing method.