JPS63177586A - 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] [Field of Industrial Application] The present invention is applicable to circuit boards used in various electronic devices, such as printed wiring boards, module wiring boards, and ceramic wiring boards, between front and back circuits, between inner layer circuits, or between front and back circuits. This invention relates to the structure of a conductive connection hole that provides conductive connection with an inner layer circuit.

[Conventional technology]

Conventionally, connections between the front and back circuits of various circuit boards, connections between inner layer circuits, and connections between front and back circuits and inner layer circuits of the various circuit boards mentioned above were made through the circuit board using a press, drill, plasma, light (e.g. laser), etc. This was accomplished by drilling a hole and using chemical plating or a combination of chemical plating and electroplating on the inner wall of the hole. In addition, after performing these platings, there are also products that are filled with solder or the like of a dissimilar metal. In addition, there are also cases where the through hole is not plated and a conductor wire is inserted into the through hole and both ends are fixed to the circuit with solder, eyelet pins are inserted, and conductive paste or pellets are filled (
There is a Japanese Patent Application Publication No. 61-100999).

The cross-sections of various conventional conductive connection holes are shown in FIG. 4 and 4) show a case in which a plating film is formed only on the inner wall of the conductive connection hole (through hole) 3 of the front and back circuits 2. Except for the connecting holes between the inner layer circuits (of these), which are filled with resin, there are no connections between the front and back circuits.
The feature is that the conductive connection hole between the front and back circuits and the inner layer circuit is a hollow button.

(C) shows a hole made conductive by plating and filled with solder of a different metal or conductive paste. ) is the one in which the inner wall of the hole is not plated and each eyelet is inserted,
■ indicates that a conductor wire is inserted into the hole and its both ends are fixed to the front and back circuits with solder; ■ indicates that a conductive paste or pellet is inserted into the hole; , indicates a conductive paste or pellet inserted.

FIG. 5 is a diagram showing a state in which electronic components are mounted on a conventional circuit board having conductive connection holes. FIG. 5 shows a state in which a component fixing land is pulled out from the conductive connection hole, and the connecting bump 5 of the component 4 is fixed onto it. 5) shows a state in which the connecting bang 5 of the component 4 is fixed on the conductive pellet.

[Problems that the invention does not even try to solve]

In recent years, due to the high-density anti-component mounting of circuit boards, the miniaturization of circuits has progressed, and the wiring density has been improved. Specifically, the circuit@/interval is 0.1/0.1 tax~0.
06/0.06 m. For this reason, conductive connection holes between front and back circuits, between inner layer circuits, or between front and back circuits and inner layer circuits have been put into practical use with a diameter of 0.3 to 0.1 m, and in some cases, conductive connection holes with a diameter of ≠0.1H or less have been made as prototypes. has been done.

In circuit boards with such high-density microcircuits, the conventional conductive connection holes having the above-described structure cause various problems as described below.

In the case where plating is formed only on the inner wall of the hole, cracks are likely to occur in the plating film due to the heat generated when components are mounted. When through-holes are filled with solder or the like, cracks are likely to occur in the plating film due to the heat generated during filling with solder. This means that the plating film is formed only on the inner wall of the hole (the inside of the hole is hollow), and therefore reliability is poor.

Therefore, the component could not be directly fixed to the bill holder, and it was necessary to pull out the circuit (-) for fixing the component through the hole. For this reason, even if the circuit is miniaturized, there is a problem in that the wiring density of the microcircuit cannot be improved by providing lands. This problem is the same even when the inner wall of the hole is not plated and a conductor wire is inserted and its both ends are fixed with solder, or when an eyelet is inserted. In particular, in the case where the conductor wire is inserted and fixed with solder or the eyelet hook is inserted, there is a problem that the connection between the inner layer circuit and the conductor wire or eyelet hook is not good.

On the other hand, the method disclosed in JP-A-61-100999, in which conductive pellets are filled with or without a plating film on the inner wall of the hole, enables high-density component mounting because components can be directly fixed to the tag. However, since this conductive pellet is made of metal and resin and is inserted into a hole using a punch, press, etc., if the hole is less than -0.1 m, it will not be sufficiently filled, so if the hole diameter is ≠0. 3 tm or more, and therefore has been an obstacle to substantially improving the wiring density of fine circuits.

It is an object of the present invention to solve the above-mentioned conventional problems and to enable improved wiring density and high-density component mounting.

[Means for solving problems]

The above purpose is to completely fill the entire conductive connection hole between the front and back circuits of the circuit board, between the inner layer circuits, or between the front and back circuits and the inner layer circuit with a metal that is integral with the metal of these circuits and is the same as the metal of these circuits. This is achieved by what is being done.

〔Example〕

An example of an embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. In the case of a double-sided circuit board, the prisoner in Figure 1 is (
6) is a sectional view of a multilayer circuit board. Prisoner in Figure 2
(6) is a plan view of the circuit in the hole portion. 1 and (2) show a state in which the circuit 2 is wired on both sides and the inner layer of the insulating plate 10, and the conductive connection hole 3 is integrated with the circuit and filled with the same metal.

2 and (6) show an embodiment in which there is no land in the portion of the conductive connection hole 3, and this is an example in which the distance between the holes can be narrowed and a high-density microcircuit can be formed. In particular, when the conductive connection hole is 160.1 tea or less, wiring can be performed with a circuit width and an interval of 0.1 m or less, respectively.

Fig. 2 (0 to @ show an embodiment in which a land is provided in the conductive connection hole as in the conventional case. In the present invention, as shown in Figs. 1 and 2, the conduction connection hole is integrated with the circuit. In addition, by filling with the same metal, the connection bumps 5 of the components 4 can be directly fixed to the tag as shown in FIG. 3, thereby achieving both improved wiring density of fine circuits and high-density component mounting. can be achieved.

In the present invention, there are many known methods for completely filling the conductive connection hole with the same metal as the circuit, such as chemical plating, a combination of chemical plating and electroplating, thermal melting, plasma, sputtering, etc. method can be applied. These are selected depending on the type of insulating plate used, the type of filling metal for the circuit and conductive connection hole, and the size of the hole. Among these methods, the technical aspects of filling the holes, ease of operation, mass production (
From the viewpoint of industrial utility value (yield, cost), etc., chemical plating, a combined method of chemical plating and electroplating, and a thermal melting method are preferred. Below is an overview of this champion.

The chemical plating method involves drilling holes in various types of insulating plates or insulating plates covered with metal foil such as copper, and then applying metals (Pd, Au, Cu, Ni, etc.) that act as catalysts for chemical plating reactions to the surface and inner walls of the holes. This is a method in which the metal is deposited and then chemically plated with Cu, Ni, etc. For circuit formation, after chemically plating the entire surface,
A photoresist is formed on it, then a circuit pattern is drawn by photography, the 7 photoresists other than the circuit are removed, the exposed chemical plating film and metal foil are etched away, and finally the 7 photoresists on the circuit are removed. Completed except for. As another circuit forming method, it is also possible to apply a full additive method in which a metal resist is first formed in areas other than the circuit forming part, and then chemical plating is performed on the circuit forming part to form the circuit. That is, the chemical plating method forms circuits and conductive connection holes using only a chemical plating film.

The combined use of chemical plating and electroplating is a method in which the aforementioned chemical plating is first applied thinly, and then a thick layer is formed using electroplating of the same metal as the chemical plating.

The circuit formation method is to form a photoresist after electroplating and form the circuit by etching in the same way as the chemical plating method described above, or to form a photoresist in areas other than the circuit formation area after chemical plating and to form holes. An example of this method is to thicken the inner wall and circuit by electroplating, then remove the photoresist, and then remove the exposed chemically plated film and underlying metal foil by etching.

The thermal melting method uses various types of ceramic plates covered with metal foil, and after making holes, a ball made of the same metal as the metal foil is placed on a billboard, and the metal is melted in an electric furnace heated to a temperature higher than the melting temperature of the metal. This is a method in which the foil and metal balls are melted to fill the hole and are simultaneously integrated, and then etched to remove metal other than the circuit to form the circuit. Of course, the metal ball used in this method must have a volume larger than that of the hole. The metal foil may be formed by plating after making holes.

Insulating plates include paper, glass cloth, aramid fibers, etc. impregnated with organic resins such as phenol, epoxy, and polyimide and laminated and bonded, various ceramic materials, metal plates wrapped in organic resin, and various other types. Examples include those in which insulating substrates are bonded together, and the present invention is not limited to any of them. On the other hand, as a method for making holes in the insulating plate, known methods such as pressing, drilling, plasma, melting, laser, and chemical processing can be applied depending on the type of the insulating plate and the intended hole diameter. Further, the shape of the hole viewed from the top surface may be a circle, a modification of a circle, a polygon, or a modification thereof. On the other hand, the cross-sectional shape of the hole may be a cube, a triangular pyramid, a cone, a cylindrical shape, or the like.

The metals forming the circuit and the metals filling the conductive connection holes include copper, nickel, gold, silver, platinum, tin, lead, 3-Hart, tungsten, molybdenum, niobium, palladium,
Examples include alloys thereof, and the present invention is not limited to any of these.Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 An insulating plate (glass cloth base material K, impregnated with epoxy resin and laminated and bonded) with a total thickness of about 1.0 mm and having copper foils of about 9 μm thickness on both sides was drilled with a drill of ≠0.1 mm. A hole was formed. Next, the surface of the copper foil was cleaned with an aqueous ammonium persulfate solution, and then washed with water.

Next, the copper foil was treated with an aqueous solution of 15% hydrochloric acid, and then immersed in a palladium colloid catalyst solution to apply palladium to the surface of the copper foil and the inner walls of the holes. After washing with water, palladium was activated with 3.6-dihydrochloric acid and washing with water was performed. Next, plating was carried out at 70° C. for about 20 hours using a chemical steel plating solution having the following composition, while replenishing the consumable components of steel, formalin, and sodium hydroxide, and removing generated hydrogen by ultrasonic stirring.

Chemical steel plating solution composition Copper sulfate 10 l/l Ethylenediaminetetraacetic acid 35 f/137 thiformin 3 td/ Sodium hydroxide pH
12,8 (20℃) Measure 1 ε' Dipyridyl 35
m1/1 polyethylene glycol (molecular weight 600)2
After washing with water and drying, a dry film resist for etching resistance was laminated on both sides, a circuit with a width of 0.06 mm and a film with an interval of 0.08 tag were adhered, and the circuit was exposed with a high-pressure mercury lamp. was baked. Then, develop
Furthermore, copper other than the circuit was removed using iron chloride etching solution.

Next, the etching-resistant dry film resist on the circuit was removed to obtain a high-density circuit board.

As a result of observing the top surface of this circuit board, it was found that the conductive connection hole of ≠0.1 was completely blocked, as shown in Figure 2.
, 06 sieve width circuits were completely formed with intervals of 0.08 m width. Next, the circuit board was cut through the conductive connection hole, and the cross section was observed.As a result, the entire conduction connection hole was completely filled with copper.

Example 2 Overall thickness of about 0.14-μm with copper foil about 18 μm thick on both sides
An excimer laser (wavelength 308 nm, pulse output 400 mJ, oscillation time 3Q) was used.
A hole with a diameter of about 0.05 wm was formed using the same method. Thereafter, a high-density circuit board was obtained in the same manner as in Example 1. However, the circuit width/interval was O,OS 10,05 tm. Further, the chemical steel plating time was 11 hours.

As a result of observing this circuit board from the top, it was found that the conductive connection hole was completely blocked, as shown by ■ in Figure 2.
m-wide circuits were formed at intervals of 0.05-. Next, we cut the conductive connection hole portion of this circuit board and observed the cross section, which revealed that the entire conduction connection hole was completely filled with copper.

Example 3 Using the insulating plate used in Example 2, holes were formed with a -0.1 m drill. Thereafter, in the same manner as in Example 1, palladium, which serves as a catalyst for a chemical plating reaction, was deposited on the surface and the inner wall of the hole. Next, using a chemical copper plating solution having the above composition, a plating film of about 1.6 μm was formed on the surface and the inner wall of the hole. next,
After washing with water, it was washed with 50% H, So, and then washed with water again. Next, using a copper sulfate electric steel plating solution (manufactured by Ebara Cordierite, Cu-BRITE TH solution), the solution temperature was 30°C.
Plating was carried out for 3 hours at a current density of λ5A/dm' and a combination of air stirring and ultrasonic stirring. Next, after washing with water and drying, the dry film resist for etching resistance was laminated, the circuit was baked, developed, etched, and the dry film resist for etching resistance was removed in the same manner as in Example 1 to obtain a high-density circuit board. Ta.

As a result of observing this circuit board from the top side, (A) I in Figure 2
As shown in c, 0,06-width circuits in which the -0,1 tm conductive connection holes were completely blocked were formed at intervals of 0.08 m width. Next, the circuit board was cut through the conductive connection hole, and a cross-sectional examination revealed that the entire conduction connection hole was completely filled with copper.

Example 4 0.75-thick beryllia ceramics (manufactured by Plush Ferman, USA) with KCOs laser ≠〇, 06
I made a hole for va. Next, Pd as a catalyst for the chemical plating reaction was attached to the surface and the inner wall of the hole, and plated with the same chemical copper plating as in Example 1 for 5 hours to deposit a plating film with a thickness of about 15 μm on the inner wall and surface of the hole. . In this state, the hole was not filled, so a copper ball with a volume of about 4 cm was placed on the tag part and left in an electric furnace at 1100° C. for about 20 minutes to extrude. As a result, a copper-clad ceramic plate was obtained in which the copper plating film and the copper balls were dissolved and the holes were closed. After polishing the copper surface to make it flat, it was washed with 5tsH, So, further washed with water, and then dried. Next, a dry film resist for etching resistance was laminated. Thereafter, a high-density circuit board was obtained in the same manner as in Example 1.

As a result of observing this circuit board from the top surface, as shown in a3) of Fig. 2, the conductive connection holes were completely blocked.
Circuits with a width of wg were formed at intervals of Q, 05 m.

Next, this conductive connection hole was cut and the cross section was observed. As a result, the conductive connection hole was completely filled with copper.

According to the circuit board of the present invention, the conductive connection hole is filled with the same metal as the circuit, so compared to the conventional hole where only the inner wall of the hole is made conductive with the same metal as the circuit. , which has the effect of further improving through-hole reliability. This is due to the difference that in the conventional method metal is formed only on the inner wall of the hole and the pitting body is hollow, whereas in the present invention the pitting body is completely filled with metal. Table 1 shows the results of a thermal shock test conducted to confirm the reliability of this conductive connection hole. Table 1 shows Example 1 of the present invention.
The circuit board made in 2 and 2 was compared with a comparative product. The comparative product is the conventional circuit board shown in Figure 4, which is the circuit board of Example 1.
It was made using the same method as above, except that the plating time was 12 hours and the thickness of the plating film on the inner wall of the hole was 3011 m.

In the thermal shock test (2), one cycle consisted of keeping the sample at -65°C for 2 hours, then suddenly raising it to +125°C and keeping it for 2 hours. In the thermal shock test (2), the sample was immersed in solder at 288° C. for 10 seconds and cooled to room temperature once. In the data in Table 1, the denominator is the number of observed through holes, and the numerator is the number of cracked through holes. It can be seen that the circuit board of the present invention has excellent through-hole reliability.

〔Effect of the invention〕

According to the present invention, by completely filling the conduction connection hole with the same metal as the circuit, it is possible to directly fix the component onto the conduction hole without having to pull out a land for fixing the component. Moreover, since the conductive holes are not filled with conductive paste or pellets, small diameter holes of ≠0.1 mg or less are also possible, and the distance between the holes can be further narrowed. Therefore, both high-density microcircuits and high-density anti-component mounting are possible.

[Brief explanation of the drawing]

Figures 1 (2) and (3) are cross-sectional views of the conductive connection hole portion of a circuit board according to an embodiment of the present invention, and Figures 2 (5) to (3) are circuits of the conduction connection hole portion of a circuit board according to an embodiment of the present invention. 3 is a sectional view showing an example of mounting components on a circuit board according to an embodiment of the present invention, FIGS. ) is a sectional view showing an example of mounting components on a conventional circuit board. 1... Insulating plate 2... Circuit 3... Continuity connection hole 4... Part of part 5... Connection bump. Figure 1 Figure 2 (A) (8) (C) (D) (E) Figure 3

Claims (1)

[Claims] 1. The entire conductive connection hole between the front and back circuits, between the inner layer circuit, or between the front and back circuits and the inner layer circuit is completely filled with the same metal as the metal of these circuits. circuit board.