JPS59126698A - Method of producing multilayer printed circuit board - 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 manufacturing a multilayer wiring board, and particularly to a method for manufacturing a multilayer wiring board with higher density.

Since the circuit density that can be mounted on one board is limited,
A multilayer wiring board is an effective means of improving packaging density.

By the way, it is well known that forming a wiring pattern is a big problem when manufacturing such a multilayer wiring board.In general, screen printing is the most commonly used method for forming this pattern. Firing techniques, negative or positive type 7-otolithography, etching techniques, etc. are used. but,
These techniques also have limitations as described below.

First, screen printing! Firing technology manufactures multilayer wiring boards by alternately screen-printing conductive paste and insulating paste in a desired pattern on a board and firing them. According to this method, conductors in different layers are connected to each other. The size of so-called through holes for this purpose is limited to around 150 μm, and it is generally impossible to process them with dimensions smaller than this. This means that there is a limit to how high the density of a multilayer wiring board can be increased by pattern formation using screen printing and baking techniques.

Next is the negative type 7-otolithography and etching technology.
Negative photoresists are generally said to have good adhesion to insulating films, especially glass films, but when processing through-holes with a width of 30 μm to 50 μm in a glass film with a thickness of about 1 μm, the side etcher requires a large amount of work. and the through hole width is 10
It becomes about 0 to 200 μm. This is a negative 7 otolith.

This means that etching technology is also not suitable for increasing the density of multilayer wiring boards.

Although it is a positive type photolithography/etching technique, the positive type 7 photoresist has poor adhesion to an insulating film, especially a glass film. Therefore, according to the conventional manufacturing method in which through-holes are formed by depositing such a positive type photoresist directly on the insulating film, the photoresist F and the insulating film are removed especially during wet etching using chemicals. The etching solution had seeped into the space between the two and increased the side etch.

As described above, in the multilayer wiring technology using the conventional method as described above, the packaging density of the wiring board reaches its limit at the process level when the conductor pitch of the first layer conductor is 4 wires/cage and line/gear wire. Yields were also generally poor.

This invention has been made in view of the above-mentioned circumstances, and it manufactures a multilayer wiring board that enables higher-density packaging by improving the dimensional accuracy in the side direction of through holes that connect conductors of different layers. The purpose is to provide a method.

In other words, Jin's invention uses chromium, sapphire, etc., which have excellent adhesion to the insulating film, as an etching mask for the insulating film, instead of a positive type 7-otoresist, which has poor adhesion to the insulating film, especially glass film. The etching mask is deposited on the film, the deposited etching mask is patterned using a well-known positive photoetching technique, and the insulating film is etched through the patterned etching mask material. The idea is to form a through hole.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a multilayer wiring board according to the present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

FIG. 1 sequentially shows the manufacturing steps of an embodiment of the method for manufacturing a multilayer wiring board according to the present invention, and the manufacturing method will be explained in the order of the steps with reference to the drawings.

(1) Gold (AU) is screen printed to a thickness of 5 μm as the first layer conductor 2 on a substrate 1 made of ceramic or the like, and then fired. (See FIG. 1(a)) (2) A positive type 7 photoresist 3 is coated on the Au film 2 to a thickness of 4 to 8 μm.

(See FIG. 1) (3) Ultraviolet light is applied to the photoresist 3 through the photomask 4 on which a suitable wiring pattern for the first layer conductor is drawn (exposure). (See Figure 1 (C)) (4) After exposure, develop with an organic solvent, etc. After obtaining the desired resist pattern 3 (development), heat treatment is performed to improve the adhesion between the resist 3 and the AU film 2. (post bake)
administer. (See FIG. 1(d)) (5) Next, the AU film 2 is etched with an iodine-potassium iodide-based etching solution. (See FIG. 1(e)) (6) After the etching is completed, the unnecessary resist 3 is peeled off and removed. (Figure 1(f)
(See) The above is the pattern forming process for the first layer conductor 2 using the well-known positive photoetching technique. In this way, the first layer conductor 2 with a pitch of 8 conductors/conductor (conductor width of 75 μm and space width S of 50 μm) is formed.

(7) Next, screen print a glass film as the insulating film 5.
It is formed to a thickness of 20 μm by firing.

The thickness of the glass film 5 is preferably thicker in order to alleviate the unevenness of the glass film 5 caused by the unevenness of the ceramic substrate 1 and the protrusion of AHH2O. (See Figure 1) (8) Further, on the upper layer of this glass film 5, chromium (C4) is vacuum-deposited as a metal 6 for an etching mask that is not melted by the etching solution (acidic acid mixture) for the glass film 5. It is formed to a thickness of 0.5 to 1.0 μm by means such as the above. (See Fig. 1 (h)) (9) A positive photoresist 3 with a thickness of 2 to 4 μm is coated on the Cr film 6 again, and after fc, ultraviolet light is applied through the photomask 7 for through-hole processing. is incident on the photoresist 3 (M light),
, (See Figure 1 (in)) (10) When this exposure step is completed, development and boss baking are performed in the same manner as in the step (4) above to obtain the desired resist pattern 3. (See Figure 1 (I)). (11) Next, the Cr film 6 is etched using, for example, a ceric ammonium nitrate-based etching solution.

At this time, etching may be performed by immersing the substrate in the above-mentioned etching solution, or etching may be carried out by spraying the above-mentioned etching solution or other liquid onto the substrate using a shower etching technique. . According to shower etching technology that applies physical force, side etching can be reduced and dimensional accuracy can be further improved. (See Figure 1(k)) Above (9)
) (10) In the photolithography process of (11), Cr
Since the film 6 has strong adhesion strength to the positive resist 3, it can be processed with high dimensional accuracy for predetermined resist dimensions.
By etching the glass layer 5 using the film 6 as an etching mask, through holes are formed at predetermined locations (see FIG. 1(1)). As the etching solution for the glass layer 5, for example, a mixed solution of local acid and dinic acid is suitable. In this step, the Cr film 6 has good adhesion strength to the glass layer 5, and side etching can be suppressed to about the thickness of the glass layer 5 or less.

FIG. 2 shows an enlarged view of the through-hole portion formed in this manner. Note that the numbers assigned to this figure correspond to the numbers of each component in FIG.

In this figure, since the side etch width did of the glass layer 5 is almost equal to the film thickness of the glass layer 5 at the through-hole portion, the relationship between the through-hole width n and the width m of the C7 film 6 is approximately expressed by the equation below. It becomes like this.

m=n-26=n-'lh Therefore, for example, if the width m of the Cr film 60 is processed to 30 μm and etched, the null-hole width n will be approximately 60 μm.
can be formed into

(13) After the above etching is completed, the unnecessary resist 3 is peeled off, and then the Cr film 6 is removed, for example (11).
) is removed by etching with the 27thium ammonium nitrate etching solution used in step ). Of course, the etching solution does not affect the glass layer 5' and the first layer conductor 2. (See Figure 1) (14) Au'(r) is screen printed and fired as the second layer conductor 8 on the soil layer of the glass layer 5 in which the through holes are formed. is printed thickly, and as mentioned above, the etched cross section of the through-hole section is sloped at a gentle 75λ of about 45 degrees due to side etching, so the thickness of the second layer conductor 8 is reduced to about 10 to 15 μm. If you do this, there will be no disconnection.

(See Figure 1 (n)) (15) Finally, using the photomask for the second layer conductor on which appropriate wiring patterns have been drawn, use the pattern forming process for the first layer conductor (the first (See Figures (2) to (6))
By performing photoetching similar to the above, the wiring turns of the second layer conductor are formed (see Fig. 1 (0)). If there are three or more layers, fc
, (7) to (15) may be repeated again.

However, in the above-mentioned embodiment, the wiring conductor is A,
However, other materials may be used for the wiring conductor 11, such as Ag-Pb-Cu.

Further, in the above-described embodiments, the wiring conductor is a thick film, but the wiring conductor may be a thin film that can be fired.

In this case, the thickness of the insulating film can be made thinner, and the dimensional accuracy of the through holes formed in the insulating film can be further improved.

Furthermore, in the above-mentioned embodiment, CRT was used as the metal for the etching mask, but this metal for the etching mask can be etched with an etching solution that does not corrode the underlying insulating film, and has good adhesion to the insulating film. Any other material may be used as long as it is of good quality. When the insulating film is made of glass, molybdenum (Mo) or the like may be used as the etching mask metal.

As explained above, according to the method for manufacturing a multilayer wiring board according to the present invention, appropriate through holes are formed in the insulating film using co9MO or the like, which has good adhesion to the insulating film, as an etching mask. It is possible to improve the dimensional accuracy of the through hole in the side direction. Further, along with this, it is possible to improve the multilayer wiring density. Note that since only positive type photoresists are used, the manufacturing process is simplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a method for manufacturing a multilayer wiring board according to the present invention in the order of its manufacturing steps, and FIG. 2 is an enlarged view showing a through-hole portion formed by the method for manufacturing a multilayer wiring board according to the present invention. This is an enlarged view. DESCRIPTION OF SYMBOLS 1... Substrate, 2... First layer conductor, 3... Positive photoresist, 4.7... Photomask, 5... Insulating film, 6... Etching mask material, 8...・Second layer conductor Figure 1 (C) (G) (b) (]) (k) (L) (m) (n)
(0) Figure 2

Claims (1)

[Claims] (1) An insulating film is deposited on a first conductor formed on a substrate, and further connected to the first conductor through a through hole formed in the insulating film. In the method for manufacturing a multilayer wiring board having two or more layers, which consists of repeating the steps of forming a second conductor on the insulating film, the second conductor has good adhesion to the insulating film and is not etched by an etching solution for the insulating film. After depositing the mask material, the through holes are formed in the insulating film by forming a desired pattern in the deposited etching mask material and etching the insulating film through the pattern of the formed etching mask material. (2) The method for manufacturing a multilayer wiring board according to claim (1), wherein the insulating film is glass and the etching mask material is chromium. (3) The method for manufacturing a multilayer wiring board according to claim (1), wherein the insulator M is glass and the etching mask material is molybdenum.