JP2675657B2 - Method for forming through holes in printed circuit boards - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming through holes in a wiring circuit board, and more specifically, in the manufacture of a wiring circuit board used as a mounting board for semiconductor elements, etc. The present invention relates to a method of forming a through hole which is a conductor structure that penetrates the front and back of a plate.

[Conventional technology]

Among wiring circuit boards, particularly for mounting boards for semiconductor elements that require fine and high-quality wiring circuits, instead of the conventional plating method or the like, a conductor film or other material is formed by thin film forming means such as vacuum deposition or sputtering. A method of forming a functional film has been proposed.

The formation of the film by this thin film forming means is that the conductor film can be formed relatively easily on the ceramic substrate and that not only the conductor film but also various functional films such as insulators, resistors and dielectrics can be formed by the same method. Advantages of being able to form a film, forming a high-quality film with few impurities, and being able to manufacture a printed circuit board with low skin resistance and excellent high-frequency characteristics by making the surface roughness of the joint surface between the substrate surface and the conductor film fine. have.

When forming the conductor film of the wiring circuit board by the thin film forming means as described above, the so-called through holes used for connecting the wiring circuits on the front and back surfaces of the substrate and for mounting various element parts are used. The conductor film is also formed on the inner surface of the through-hole hole in the same step as that for forming the conductor film.

For example, in the sputtering method, as shown in FIG. 12, on the cathode 3 installed in the processing chamber 1 at a position facing the surface of the substrate 2 with a certain distance (usually several tens mm or more), A target 4 made of a conductive material such as Cu is attached to the processing chamber 1, and the inside of the processing chamber 1 is evacuated by a vacuum pump (not shown) connected to an evacuating port 5, and a supply is also provided in the processing chamber 1. Ar gas or the like is introduced from the port 6, a voltage is applied to the cathode 3 to turn the target 4 into plasma, and the conductor material of the target 4 is deposited on the surface of the substrate 2 to form a film. If the through hole 2a is formed in the substrate 2, the conductor material is also deposited on the inner surface of the through hole 2a, so that the through hole is formed simultaneously with the conductor film on the surface of the substrate 2. . Although the above description relates to the sputtering method, a through hole is basically formed by the same processing method even by a thin film forming means such as a vacuum evaporation method.

[Problems to be solved by the invention]

However, in the above-described method of forming a through hole by the conventional thin film forming means, there is a problem that the conductor film having a sufficient thickness is not formed on the inner surface of the through hole hole, resulting in poor quality performance of the through hole. .

It is considered that this is due to the causes described below.

In the conventional processing method as shown in FIG. 12, the conductive material reaches the front surface of the substrate 2 facing the target 4 almost uniformly. Therefore, the through hole 2a
The amount of the conductor material reaching the inside of is equal to or less than the amount of the conductor material reaching the end face of the through hole hole 2a facing the target 4.

Therefore, as shown in FIG. 13, the thickness T of the substrate 2, the thickness t ₀ of the conductor film 4a formed on the surface of the substrate 2, the inner diameter d of the through hole 2a, and the inner surface of the through hole 2a are uniform. The thickness t of the conductor film 4b when a conductor film having a uniform thickness is formed.
Then, when these relations are obtained, the following equation is obtained.

When ^{π (d / 2) 2 t} 0 ≒ πd (T + t 0) t ... (1) (1) approximates the _{equation, t ≒ dt 0/4 (} T + t 0) ... (2) (2) In formula, for example, Table 1 below shows the results of obtaining the values of t and t / t ₀ when d was changed under the assumption that T = 0.635 and t ₀ = 0.01.

From the results in the above table, the thickness t ₀ of the conductor film 4a on the substrate surface is
As compared with the above, as the thickness t of the conductor film 4b on the inner surface of the through hole is very thin and the inner diameter d of the hole 2a for through hole becomes smaller, the thickness t of the conductor film 4b on the inner surface of the through hole becomes smaller. I understand. For example, when d / T is 1 or less, only the thickness of 20% or less of the thickness t ₀ of the conductor film 4a on the substrate surface is formed.

Thus, in the conventional processing method, the through hole
It is extremely difficult to form a conductor film having a sufficient thickness on the inner wall of 2a.

Further, as shown in FIG. 14, the conductor material reaching the inner surface of the through hole 2a of the substrate 2 from the target 4 is
There is also a problem that it is easy to deposit on the inlet side of the through-hole 2a close to the target 4, and the proportion of the conductive material reaching the back of the through-hole 2a far from the target 4 decreases. Therefore, on the inner surface of the through-hole 2a, the thickness of the conductor film 4b may differ depending on the location, and the thickness on the back side becomes smaller than that on the inlet side, resulting in an increase in the resistance value of the through-hole. In some cases, it may cause slump or poor conduction.

Therefore, an object of the present invention is to provide a through-hole forming method for a printed circuit board by means of a thin film forming means having excellent quality performance of a conductor film, and to ensure that the thickness of the conductor film formed on the inner surface of the through-hole is sufficient over the entire inner surface. (EN) It is possible to provide a method of forming a high-quality through hole which can be secured and has a small conduction resistance without causing a conduction failure.

[Means for solving the problem]

A through-hole forming method for a printed circuit board according to the present invention, which solves the above-mentioned problems, provides a conductor material source in the vicinity of each through-hole provided on a substrate, and heats the conductor material source by discharge. Then, it is evaporated and deposited on the inner surface of the through hole hole.

As the substrate, an ordinary substrate material for a wiring circuit board, which is made of ceramics, glass, synthetic resin, or other material, can be freely used according to the application of the wiring circuit board. Through holes are formed in the substrate by a usual processing means. The diameter and aspect ratio of the through hole can be set freely.

As the conductive material source, it is possible to form a film by evaporating by a discharge, electric heating or the like among conductive materials made of various metals or metal compounds used in ordinary printed circuit boards such as Cu and Au. Use material.

The conductor material source is arranged close to the through hole hole for each through hole hole formed in the substrate. That is, the inner space of the through-hole or the through-hole is arranged so that the conductive material obtained by heating the source of conductive material by vaporization and evaporating can easily reach the entire inner surface of each through-hole. The source of conductive material shall be placed just outside both end faces of the hole.

As a means for evaporating the conductive material source and depositing it on the inner surface of the through-hole, basically the same principle or mechanism as in the ordinary thin film forming / applying means can be applied, but the inner surface of the through-hole is well-suited. In order to form a different conductor film, the following constitution is preferable.

First, as a conductor material source, a pair of discharge electrodes made of a conductor material is arranged on both sides of the substrate with a hole for a through hole interposed therebetween, and a voltage is applied between the pair of discharge electrodes under a reduced pressure atmosphere to cause discharge. A method of evaporating the discharge electrode made of a conductive material can be adopted.

It is preferable that the pair of discharge electrodes made of a conductive material have sharp ends facing each other in an acute angle or a needle shape so that the discharge electrodes can easily discharge each other. Further, since the shorter the distance between the discharge electrodes is, the easier the discharge is, it is preferable to dispose the discharge electrodes as close to the substrate or through-hole as possible. Set the interval to about 1 mm or less. The discharge electrode is
The entire electrode may be arranged outside both sides of the substrate, or a part of the discharge electrode may be arranged so as to enter the inside of the through hole hole to the extent that it does not come into contact with the opposing discharge electrode. Since the discharge electrode consumes and reduces the conductor material due to discharge, when performing repeated treatment using the same discharge electrode, if necessary, adjust the position of the discharge electrode by the amount corresponding to the decrease in the conductor material, The shape of the discharge electrode may be modified.

When a voltage is applied to the discharge electrode to cause discharge, the atmosphere in the processing chamber in which the substrate and the discharge electrode are housed is kept in a reduced pressure atmosphere to facilitate discharge and to improve the inner surface of the through hole hole. A conductor film is formed. Specifically, in a decompressed atmosphere, the processing chamber is evacuated and an inert gas such as Ar gas is introduced into the processing chamber so that the pressure of the inert gas is set between several Torr and several 10 Torr. It is preferable to keep it. The specific setting of the inert gas pressure can be performed in the same manner as in the normal thin film forming method, taking into consideration the so-called Paschen's law.

The voltage applied to the discharge electrode is set to a voltage equal to or higher than the discharge start voltage sufficient to cause discharge at the discharge electrode at the start of processing, and when discharge is started, the discharge arc expands to the substrate, etc. It is preferable to lower the applied voltage so as not to give damage so that the discharge is performed at the discharge sustaining voltage necessary for sustaining the discharge. The discharge sustaining voltage varies depending on various conditions such as the inner diameter of the through hole hole, the gas pressure of the atmosphere, the distance between the discharge electrodes, etc., but is usually about several tens of volts.

When the substrate is provided with a large number of through-hole holes, the discharge electrodes may be moved to the positions of the through-hole holes using only a pair of discharge electrodes to form the conductor film by discharge. However, a plurality of different sets of discharge electrodes may be used for each through hole. When a plurality of sets of discharge electrodes are used, an independent pair of discharge electrodes for each through-hole and a wiring circuit for applying a voltage to the discharge electrodes and a power supply may be provided, or a plurality of sets of discharge electrodes may be provided. May be applied with a voltage through a wiring connected to one power source. A voltage can be simultaneously applied to the discharge electrodes arranged in the plurality of through-holes to form a conductor film on the inner surfaces of the through-holes, whereby efficient processing can be performed. By sequentially switching wirings from the same power source to apply a voltage to a plurality of sets of discharge electrodes, it is possible to process even if the capacity of the power source is small.

In addition, if voltage is applied to a pair of discharge electrodes in which a large number of sharp tips are arranged in parallel, and the substrate is relatively moved in parallel with the facing surface of the discharge electrodes, the gap between the sharp tips of the discharge electrodes is passed. When the hole for hole passes, discharge occurs through the hole for through hole forming the shortest path between the discharge electrodes, and a conductor film is formed on the inner surface of the hole for through hole at that portion.
Normally, in the through-hole hole that constitutes the shortest path between the discharge electrodes, the line connecting the tip portions of the opposing discharge electrodes coincides with the central axis of the through-hole hole. Therefore, as the substrate passes, the through-hole holes that form the shortest path between the discharge electrodes move in order,
The conductor film can be continuously formed in all of the plurality of holes for through holes.

Next, a method different from the above-mentioned method using discharge will be described. That is, as a conductor material source, a thin wire made of a conductor material is inserted through a hole for a through hole, and the conductor material thin wire is evaporated in a vacuum atmosphere by energizing the conductor material thin wire.

The fine conductor material wire can be manufactured by the same means as the ordinary conductor wire for wiring except that the above-mentioned material serving as the conductor material source is used. The wire diameter is at least not more than the thickness that can be inserted into the through hole hole, and a conductor film having a sufficient thickness can be formed when the conductor material is evaporated and deposited on the inner surface of the through hole hole. The thickness of the conductor material must be large enough to supply the conductor material. Although the specific wire diameter varies depending on the purpose of the through hole, the required performance, etc., under normal conditions, the wire diameter d ₁ determined by the following formula is preferable.

k: correction coefficient d ₂ : through hole hole inner diameter t: required film thickness of conductor film The correction coefficient k is a value obtained based on experiments, experience, etc. depending on the processing conditions.

The thin conductor material wire is wired and connected to a power source so that it can be energized in a state of being inserted through the through hole. Since the fine conductor material wire may be present only inside the through hole hole or in the vicinity of the inside and both ends of the through hole, a normal wiring conductor is connected to the fine conductor material wire outside the substrate.
Unlike the thin conductor material wire, it is preferable to use a material and a wire diameter that do not evaporate when electricity is applied to the conductor for wiring.

It is preferable that a current flowing through the thin conductor material wire be a relatively large current so that the thin conductor material wire can be vaporized in a short time and deposited on the inner surface of the through-hole. For example, wire diameter
In the case of 0.1mm copper wire, about 0.1
The conductor film can be formed within seconds. When the fine conductor material wire is energized and the fine conductor material wire is completely evaporated, no current flows thereafter.

The atmosphere for energizing the thin conductor material wire is a vacuum atmosphere. Generally, the higher the degree of vacuum, the better the evaporation of the conductor material fine wire and the formation of the conductor film, and the formation of a high-quality conductor film. However, in consideration of practicality and productivity, the ordinary thin film forming method is used. The degree of vacuum used in the above may be used.

When forming a through hole on a substrate with a large number of through hole holes, it is efficient to simultaneously energize the conductor material thin wires that are inserted and arranged for each through hole hole to simultaneously form a conductor film. Work can be done. Further, if the plurality of thin conductor material wires are sequentially energized by sequentially switching the wiring, it is possible to process with a power source having a relatively small capacity.

Further, one end of each thin conductor material wire inserted through the many through-holes is connected and kept at the same potential such as ground potential, and the other end of each thin conductor material wire is opened. Then, the contacts connected to the power source are scanned, and the other ends of the respective conductor material thin wires are sequentially contacted, and an electric current is caused to flow through the conductor material thin wires in that portion. The conductor film can be formed in the holes easily and efficiently.

In the above method, the conductor material thin wire, that is, the conductor material source itself is energized to evaporate.However, as described below, the conductor material is indirectly heated by using a heating wire that generates heat by energization separately from the conductor material. It can also be evaporated.

That is, a conductor material-coated heat generating wire in which a conductor material layer serving as a conductor material source is coated on the outer periphery of a heat generating wire that generates heat when energized is inserted into a through hole hole, and the heat generating wire is energized in a vacuum atmosphere. By doing so, the conductor material layer can be evaporated.

For the heating wire, a wire such as a tungsten wire that efficiently generates heat when energized but does not evaporate like a conductive material source is used. The conductor material as described above is coated on the outer periphery of the heating wire to a constant thickness to form a conductor material layer, thereby forming a conductor material-coated heating wire. An ordinary wiring lead wire for supplying a current is connected to both ends of the conductor material-covered heating wire so that the heating wire can be energized. The thickness of the conductor material layer that covers the heating wire is equal to or smaller than the thickness of the conductor material-covered heating wire that can be inserted into the through-hole, and is equal to the diameter of the thin conductor material wire that is obtained by the above equation (3). It should be set so that a corresponding amount of conductive material can be supplied.

The method of arranging the conductor-material-covered heating wire in the through-hole, the method of setting the vacuum atmosphere, the method of energizing, etc. may be the same as in the case of using the conductor-material thin wire described above.

In this method, since the heating wire remains in the through hole even after the conductor film is formed in the through hole, it is necessary to remove the heating wire from the substrate after the processing.

In the through hole forming method according to the present invention described above, among the conductor films formed on the substrate, only the conductor film on the inner surface of the through hole hole is formed. The method of forming a conductor film by the thin film forming means may be applied. Either of the conductor film forming step on the inner surface of the through hole and the conductor film forming step on the substrate surface may be performed first. In addition, if the processing conditions such as the processing atmosphere can be matched, the formation of a uniform conductor film on the substrate surface by the conductor material target arranged at a position distant from the substrate surface and the placement of the conductor film close to each through hole hole It is also possible to simultaneously perform the formation of the conductor film on the inner surface of the through-hole hole by the above-mentioned conductor material source.

A conductive material source may be arranged and a current may be applied to each of the substrates to form a conductive film in the through-hole holes. However, if the through-hole holes are in the same position, a plurality of substrates are stacked. It is also possible to dispose a conductor material source inside each through hole hole or on both sides of the substrate as it is, and simultaneously form a conductor film in the through hole hole that is communicated with a plurality of substrates.

[Action]

When the conductor material source is arranged close to each through hole hole provided on the substrate, and the conductor material source is evaporated and deposited on the inner surface of the through hole hole, the inner surface of each through hole hole is formed. Ensures that the required amount of conductive material is supplied,
A conductor film having a sufficient thickness can be formed on the inner surface of the through hole.

That is, in the conventional method for forming a conductor film on a printed circuit board, in order to form a conductor film on the entire substrate on average,
Since the processing was performed with the conductor material source (target) separated from the substrate by a certain distance, a conductor film with a uniform thickness is formed on the substrate surface, but the inner surface of the narrow through-hole hole is sufficiently large. A conductor film having a uniform thickness was not formed, and in particular, the conductor film could not be formed deep in the through hole hole.

On the other hand, if the conductor material sources are arranged close to the individual through-hole holes as in the present invention, a sufficient amount of conductor material can be applied to the entire inner surface even for narrow and deep through-hole holes. It is possible to form a conductive film having a uniform and sufficient thickness on the entire inner surface of the through-hole.

Further, if the conductor material is vaporized by applying a voltage to a pair of discharge electrodes made of a conductive material disposed on both sides of the substrate with the through hole hole interposed, the through hole hole is penetrated. Because a discharge will occur,
The conductive material evaporated by the discharge is reliably supplied to the inside of the through hole hole along the discharge path. As a result, a uniform conductor film is formed on the entire inner surface of the through hole hole. Since the discharge electrodes made of a conductive material are simply arranged on both sides of the substrate and nothing needs to be provided inside each through-hole, the processing operation can be performed easily and efficiently. Further, by this, the conductive film can be continuously formed in a large number of through-holes while moving the discharge electrode and the substrate relatively, and the process can be automated or can be made into a continuous process.

Then, by energizing the conductor material thin wire penetratingly arranged in the through hole hole to cause the conductor material thin wire itself to generate heat and evaporate, the conductor material thin wire inside the through hole hole is surrounded by the inner surface of the through hole hole. Since the conductor material is reliably and evenly supplied, the conductor film having a uniform thickness can be efficiently formed. If the thin conductor material wire evaporates, nothing will exist inside the through-hole, so the substrate with the conductor film formed in the through-hole can be immediately taken out and moved to the next step. .

Next, by using the conductor material-coated heating wire, the conductor material layer can be efficiently heated and evaporated by the heat generated by the heating wire, and the conductor film can be efficiently formed even with a power source having a small capacity. It is possible to improve the forming efficiency of the, and shorten the working time.

〔Example〕

Next, embodiments of the present invention will be described in detail below with reference to the drawings.

1 to 4 show a method of evaporating a conductive material source by electric discharge.

First, FIG. 1 shows a basic configuration and its operating principle.

A through hole 12 having a predetermined inner diameter is formed through a substrate 10 made of ceramic or the like. This through hole substrate is used as a processing chamber 20 where the atmosphere of the internal space can be controlled.
Housed in Although not shown, the processing chamber 20 is connected to a vacuum pump via a vacuum exhaust port, and a gas supply source is connected to a supply port for Ar gas or the like. The specific structure of the processing chamber 20 is the same as the processing chamber used in a normal thin film forming means.

On both sides of the substrate 10, insert a through hole 12
A pair of discharge electrodes 30, 30 made of a conductive material such as The discharge electrodes 30, 30 have sharpened sharp tips at their opposite ends, and discharge easily occurs from these tips. The ends of the discharge electrodes 30, 30 are arranged within 1 mm from both surfaces of the substrate 10 so as to be close to each other, and the line connecting the ends is arranged so as to coincide with the central axis of the through hole hole 12. A DC power supply 40 is connected to the discharge electrodes 30, 30 via a wire 42. As the power source, a direct current power source is usually used, but a high frequency power source or the like can also be used. Also in each of the following embodiments, the invention is not limited to the DC power supply.

The processing chamber 20 is evacuated and Ar gas is introduced to keep the processing chamber 20 in a reduced pressure atmosphere in which Ar gas exists.
In this state, when a voltage of about several tens of volts is applied between the discharge electrodes 30,30, discharge is generated between the discharge electrodes 30,30,
The conductive material forming the discharge electrodes 30, 30 is evaporated, the conductive material is supplied to the inside of the through hole hole 12 along the discharge path, and the conductive material is deposited on the inner surface of the through hole hole 12 to form a conductive film. Is formed.

Next, FIG. 2 shows a case where through holes are formed in the substrate 10 in which a large number of through hole holes 12 are provided. In the following embodiments, the structure of the processing chamber 20 is not shown.

A pair of discharge electrodes 30, 30 having a cross section of an acute-angled isosceles triangle is provided on both sides of each through-hole 12 of the substrate 10, and the wiring 42 connected to each discharge electrode 30, 30 is switched. It is connected to the DC power supply 40 via the switch 43. When the current is sequentially applied to the respective discharge electrodes 30 and 30 while switching the changeover switch 43, a discharge is generated between the discharge electrodes 30 and 30 in the part where the current is applied, and for the through hole at the place where the discharge occurs. A conductor film 32 is formed on the inner surface of the hole 12. In this embodiment, the DC power supply 40 has one discharge electrode.
Since it is sufficient for 30,30 to have a capacity for causing a discharge, it is possible to process with a relatively small capacity power supply.

The embodiment shown in FIG. 3 is a needle-shaped discharge electrode with a sharp tip.
30 and 30 are used, and each discharge electrode 30, 30 is provided with a wiring 42 and a connection / disconnection switch 44 connected to another DC power source 40. In this way, if a separate power source is used for each of the discharge electrodes 30, 30, each power source capacity can be small. Also, if each disconnection switch 44 is connected at the same time, multiple sets of discharge electrodes 3
Discharge at 0 and 30 at the same time, and each through hole hole 12
Conductive films can be formed all at once, and work efficiency is good. In addition, connecting each disconnection switch 44 in order,
It is also possible to sequentially form a conductor film in each through hole hole 12.

In the embodiment shown in FIG. 4, the facing surfaces of the discharge electrodes 30, 30 have a large number of sharp tips, that is, sharp tips, closely arranged,
It is formed in a so-called sawtooth shape. Such a discharge electrode
When an electric current is applied to 30,30, a discharge will occur at a position where the discharge path is the shortest among the respective facing tips 34,34. Therefore, when the substrate 10 between the discharge electrodes 30 and 30 is moved in parallel with the facing surface of the discharge electrodes 30 and 30, the central axis of any of the through-holes 12 of the substrate 10 becomes the discharge electrode.
At the stage where it coincides with the line connecting any of the tip portions 34, 34 of 30, 30, electric discharge occurs at the tip portions 34, 34 of that portion, and a conductor film is formed in the through hole hole 12. When the through-hole 12 is moved from the positions of the tip portions 34, 34, the discharge in this portion ends and a new discharge starts in another portion. In this way, the through-hole holes 12 of the entire substrate 10 are
On the other hand, the conductor film is sequentially formed by the discharge.

In the above embodiment, it is not necessary to arrange the discharge electrodes 30, 30 in accordance with the positions of the through-holes 12, and it is not necessary to switch the changeover switch for each through-hole 12, so that it is simple and reliable. All through hole holes
A conductor film can be formed for 12. Therefore, the substrate 10
Even if the structure and the design of the through hole 12 are changed, the discharge electrodes 30, 30 and the like can be used with the same structure. In the above description, the discharge electrodes 30, 30 are fixed and the substrate 10 side is moved, but conversely, the same function can be achieved by fixing the substrate 10 and moving the discharge electrodes 30, 30 side. .

Next, reference examples not included in the present invention will be described. FIGS. 5 to 8 show a method of using a thin conductor material wire. First, FIG. 5 shows a basic configuration and its operating principle. The same parts as those in the above-described embodiment are designated by the same reference numerals, and duplicated description will be omitted.

Inside the processing chamber 20, the conductor material thin wire 50 is arranged by penetrating the inside of the through hole 12 of the substrate 10, and both ends of the conductor material thin wire 50 are outside both sides of the substrate 10 and are connected to the DC power supply 40. It is connected to the connecting wire 42. The conductor material thin wire 50 is
If it is arranged at the center position of the through hole hole 12, a uniform conductor film can be formed on the entire inner circumference of the through hole hole 12.
It is preferable to maintain the conductor material thin wire 50 at a predetermined position by supporting the wires 42, 42 connected to both ends of the conductor material thin wire 50 by an appropriate means (not shown).

When a large current is passed through the conductor material thin wire 50 after the processing chamber 20 is placed in a vacuum atmosphere, the conductor material thin wire 50 itself generates heat and evaporates. Since the evaporated conductor material adheres to the inner surfaces of the surrounding through-holes 12, the conductor film is formed on the inner surfaces of the through-holes 12. If the conductor material evaporates, the conductor material thin wire 50 disappears, so that nothing remains inside the sulu hole 12. Therefore, the substrate 10 on which the conductor film is formed in the through-hole 12 after the above-mentioned processing steps are completed can be immediately taken out and moved to the next step.

As shown in FIG. 6, when a large number of through-holes 12 are provided in the substrate 10, a conductor material thin wire 50 is inserted through each of the through-hole holes 12, and the conductor material thin wires 50 are inserted into the through-holes 12. If a changeover switch 43 is provided between the connecting wire 42 and the power source 40, the conductor material thin wire 50 of each through hole hole 12 is sequentially energized to form a conductor film, as in the embodiment of FIG. Can be made. In the embodiment shown in FIGS. 6 to 8, the structure of the processing chamber 20 is not shown.

As shown in FIG. 7, all the fine conductor material wires 50 inserted and arranged in the plurality of through-holes 12 are connected to one power source 40 by the wiring 42, and all are connected by the disconnection switch 44 at one place. By energizing the conductor material thin wire 50, the conductor film can be formed all at once in the through-hole holes 12.

In the embodiment shown in FIG. 8, the lower end of the fine conductor material wire 50 inserted through the through hole 12 is fixed to the supporting electrode 54, and the supporting electrode 54 is connected to the DC power source 40 via the wiring 42. There is. The upper end of the thin conductor material wire 50 is opened in a state of protruding above the substrate 10. An armature 52 having a sharp tip is provided above the substrate 10 so as to be movable in a direction parallel to the substrate 10. The armature 52 is connected to the DC power source 40 via the wiring 42.
It is connected to the.

In this state, when the armature 52 is moved in the horizontal direction as shown in the upper diagram to the lower diagram of FIG. 8, when the armature 52 comes into contact with the upper end of the conductor material thin wire 50, the conductor of that portion is contacted. An electric current flows through the thin material wire 50, and the thin conductive material wire 50 heats and evaporates, so that the conductor film 32 is formed on the inner surface of the through hole hole 12. As the armature 52 moves, it contacts another conductor material thin wire 50 one after another, thereby sequentially supplying an electric current to each conductor material wire 50 to cause heat generation and evaporation, and the through hole 12
A conductor film can be formed on the substrate. That is, armature 52
Scanning along the substrate 10
The electric current is sequentially supplied to 50 and the conductor film is formed in the through hole hole 12.
32 can be formed.

In the above-described embodiment, the current supply can be automatically switched by simply moving and scanning the armature 52 without operating the changeover switch.

Next, FIGS. 9 to 11 show a method using a conductor material-coated heating wire.

First, FIG. 9 shows a basic configuration and its operating principle. The same parts as those in the above-described embodiment are designated by the same reference numerals, and duplicated description will be omitted.

In the above method, the conductor material fine wire 50 is provided in the through hole hole 12.
However, in this method, the through-hole holes 12
The conductor-material-covered heating wire 60 is arranged in advance. The conductor material coated heating wire 60 has a coating layer made of the same conductor material as described above around the heating wire 62 made of a tungsten wire or the like.
64 is formed. Both ends of the heating wire 62 are exposed from the covered conductive material layer 64 and are connected to the wiring 42 connected to the DC power supply 40. When a current is applied to the heating wire 62 in a vacuum atmosphere in the processing chamber 20, the heating wire 62 generates heat to heat and evaporate the conductor material layer 64. The conductive material that has generated heat is deposited on the inner edge of the surrounding through-hole hole 12 to form a conductive film. When the conductor material evaporates, the conductor material layer 64 disappears, but the heating wire 62 remains, so the power supply to the heating wire 62 is cut off and the heating wire 62 is removed from the through hole hole 12.

FIG. 10 shows a substrate 10 having a large number of through hole holes 12.
In the case of forming a through hole in the through hole, the conductor material covered heating wire 60 inserted through each through hole hole 12 is
It is connected to the DC power source 40 at one place via 42, and the connection / disconnection switch 44 enables simultaneous energization. Also, the eleventh
In the illustrated embodiment, the wiring 42 of each conductor material coated heating wire 60 is
Is connected to the power source 40 via the changeover switch 43, and by operating the changeover switch 43, a large number of conductor material coated heating wires are connected.
The conductive film 66 is sequentially formed in the through-holes 12 by sequentially energizing 60. If the capacity of the DC power supply 40 has a margin, the method of energizing all at once as in the embodiment shown in FIG. 10 has high work efficiency. Further, in the embodiment shown in FIG. 11, it is also possible to use a small capacity DC power supply 40.

〔The invention's effect〕

According to the through-hole method for a printed circuit board according to the present invention described above, the conductor material source is arranged in the vicinity of each through-hole hole provided on the substrate, and the conductor material source is discharged. By heating and evaporating and depositing on the inner surface of the through-hole, it is possible to reliably form a conductor film having a sufficient thickness in the through-hole.
Further, there is no difference in thickness between the entrance side and the back side of the through hole hole, and a conductor film having a uniform thickness can be formed.

As a result, it becomes possible to form a through hole provided with a conductor film having a uniform and sufficient thickness, which cannot be produced by the conventional method of forming a through hole by a thin film forming means, which causes less resistance and causes conduction failure. It is possible to provide a wiring circuit board with a through hole that is extremely excellent in quality performance without worry. Since the method according to the present invention is a method of forming a conductor film based on the same principle as a conventional vacuum vapor deposition method, sputtering method or other so-called thin film forming means, it is denser and more closely adhered than a conventional plating method or the like. It goes without saying that the conductor film has the advantages of the thin film forming means such as high strength and excellent electric characteristics.

In particular, by evaporating the conductive material using the discharge electrode as described above, it is not necessary to provide anything inside the through hole hole, and the processing work can be performed easily and efficiently. Become. It is also possible to continuously form a conductor film in a large number of through-holes, which is a method suitable for automation of processing or continuous processing.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a method of using a discharge electrode in the present invention, FIG. 2 is an overall structure diagram, and FIGS. 3 and 4 are overall structure diagrams showing different embodiments, respectively. FIG. 5 is a schematic configuration diagram showing an embodiment of a method using a fine conductor material wire, FIG. 6 is an overall structure diagram, FIGS. 7 and 8 are overall structure diagrams showing different embodiments, and FIG. 9 is a conductor. Schematic configuration diagram showing the method of using the material coated heating wire, FIG. 10 and
11 is an overall structural view showing another embodiment, FIG. 12 is a schematic structural view showing a conventional example, FIG. 13 is an enlarged sectional view showing the thickness of a conductor film, and FIG. 14 is actually formed. It is an expanded sectional view showing a state of a conductor film. 10 …… Substrate, 12 …… Through hole, 20 …… Processing chamber,
30 ... Discharge electrode, 40 ... DC power supply, 42 ... Wiring, 50 ...
Conductor material thin wire, 60 ... Conductor material coated heating wire, 62 ... Heating wire, 64 ... Conductor material layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Miyano 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd. (72) Hiroaki Kitamura 1048, Kadoma, Kadoma City, Osaka Matsushita Electric Works Co., Ltd. 56) References JP-A-62-214170 (JP, A) JP-A-58-55563 (JP, A)

Claims (1)

(57) [Claims] 1. A through hole of a wiring circuit board in which a conductor material source is arranged in the vicinity of each through hole hole provided in a substrate, and the conductor material source is evaporated to adhere to the inner surface of the through hole hole. A method of forming a hole, wherein, as the conductor material source, a pair of discharge electrodes made of a conductor material are arranged on both sides of a substrate with a hole for a through hole interposed therebetween, and a voltage is applied between the pair of discharge electrodes under a reduced pressure atmosphere. A method of forming a through hole in a printed circuit board, wherein a discharge electrode made of a conductive material is evaporated by applying and discharging.