JPH08186384A - Method for manufacturing printed circuit board - Google Patents

Abstract

PURPOSE: To obtain a method for manufacturing a printed circuit board securing compact and thin design, strict design specifications, and characteristics. CONSTITUTION: In a method for manufacturing a multilayer wiring type printed circuit board where upper and lower adjacent conductor layers are laminated via an insulator layer 12 and the adjacent conductor layers are electrically connected, a conductor connection part for electrically connecting the conductor layers is formed on a conductor layer 11 consisting of a metal foil or a conductor circuit pattern and an insulator powder 13 is sprayed in atomized powder using, for example, a nozzle 14 for uniform deposition, thus forming an insulator layer 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed circuit board, and more particularly to a method for manufacturing a printed circuit board, which mainly includes a method for forming an insulator layer and a method for forming an electrical connection between conductor layers. .

[0002]

2. Description of the Related Art Regarding a printed circuit board of this type,
For example, literature; printed circuit board technology and its quality assurance: published by Applied Technology Publishing Co., Ltd.
(Published August 27, 2013).

Conventionally, in the manufacture of printed circuit boards, a sheet obtained by impregnating a copper-clad laminate, copper foil and glass fiber woven in a cloth shape with an insulating resin such as an epoxy resin (this sheet is hereinafter referred to as prepreg). ) Or the like is used to form a circuit pattern by etching the copper foil portion of the copper-clad laminate to form a circuit required as a circuit board. By stacking a plurality of copper clad laminates, prepregs, copper foils, etc. on which circuits have been formed, according to the circuit design, and pressing with a heat press or the like, one multilayer wiring type printed circuit board is obtained. It was Also, in the case of a substrate that requires electrical connection between conductor circuit layers, such as a multilayer substrate having many copper layers such as copper wiring layers such as copper foil of a copper-clad laminate, For the connection by the conductor of, the through hole is formed, the inner wall of the through hole is coated with a conductive film by a method such as plating, and a structure for electrically connecting with a layer required for connection is adopted. Therefore, it was necessary to make a hole in a required place with a drill or the like.

[0004]

In the conventional method of manufacturing a printed circuit board as described above, the size of the board is reduced as well as the size of the board, and the thickness between layers is also reduced, as in the recent requirements in this technical field. When the through hole becomes thin and the hole diameter of the through hole must be made very small for that reason, or when the conductor pattern of the circuit becomes fine, there are problems as listed below.

(A) Since the thickness of the substrate (material) before press lamination becomes extremely thin, handling becomes difficult. (B) It becomes difficult to accurately form a pinhole or the like from a very thin material with good accuracy. (C) With methods such as drilling, there is a limit to the hole diameter that can be processed. (D) When the diameter of the through hole is reduced in the plating in the small diameter through hole and its pretreatment process, the plating solution and the processing solution do not enter the hole, so that the plating is not formed, resulting in poor conduction. (E) In an inner bias through hole that has been conventionally used to connect an intermediate layer of a multilayer substrate having four or more layers, the cavity in the through hole is insulated in order to ensure the electrical characteristics (eg, electric capacity) of the substrate. The resin and ink were filled so that there would be no voids, but when the diameter of the inner bias through hole became small, the voids remained because the resin and ink to be filled did not enter inside, and the electrical characteristics of the substrate And the substrate quality was remarkably deteriorated. (F) In the conventional laminating method using a press, the molten resin is made to flow between the conductor circuit patterns by the heat at the time of pressing so that the spaces between the patterns are filled with the resin. As it proceeded, the resin did not flow well between the circuit patterns, and as a result, cavities were created as in the previous section, and the electrical characteristics of the substrate were changed, resulting in a marked deterioration of the substrate quality.

Due to the problems described in (a) to (f) above, it is difficult to manufacture a printed circuit board, and the rate of occurrence of defects increases, and if it further progresses, it cannot be manufactured by the above method. That is, there is a problem in that it is impossible to manufacture a substrate that can ensure the characteristics according to the design specifications.

[0007]

According to a method of manufacturing a printed circuit board according to the present invention, conductive layers adjacent to each other are laminated with an insulating layer interposed therebetween, and adjacent conductive layers are stacked. In a method for manufacturing a multilayer wiring type printed circuit board, in which a conductor connecting portion for electrically connecting between conductor layers is formed on a conductor layer made of a metal foil or a conductor circuit pattern. After the formation, the insulating powder is sprayed in the form of powder mist to be uniformly deposited to form the insulating layer.

Here, in spraying / precipitating the insulating powder on the conductive layer in the form of powder mist, the insulating powder is charged, and at the same time, the conductive layer is charged to a charge opposite to that of the insulating powder. You may use it. Further, the conductor connecting portion may be formed by applying or printing a conductor powder formed in a paste form to form a conductor mass. For this conductor block, it is also preferable to use a metal block formed by ball bonding type wire bonding. Further, a lower conductor layer of the conductor layers adjacent to each other above and below is formed, a conductor connecting portion is formed on the lower conductor layer, and then an insulator layer is formed. The upper conductor layer may be formed after the part is mechanically processed to remove a part of the insulator layer deposited on the head.

[0009]

According to the present invention, a printed circuit board is manufactured in which conductive layers adjacent to each other vertically are laminated with an insulating layer interposed therebetween, and conductive layers adjacent to each other are electrically connected. By the method, after forming a conductor lump for electrically connecting between the conductor layers on the conductor layer formed of a metal foil or a conductor circuit pattern as a connection portion, finely powdered insulator powder is atomized. Since the insulating layer is formed by spraying and uniformly depositing, it is possible to form a thin insulating layer that cannot be manufactured by a method using an insulating sheet such as a conventional prepreg. Thinning becomes easy. In this case, since a fine powder of insulating powder is used, even a fine conductor circuit pattern can be sufficiently filled between the patterns,
A good insulator layer is obtained.

Further, since the structure is such that a conductor mass is formed and used to establish electrical connection between conductor layers, an electrical connection structure with an extremely small area, which has been impossible with the conventional through-hole connection. This contributes to downsizing of the printed circuit board.

[0011]

EXAMPLES In this example, a four-layer substrate, which is easy to explain, will be described as an example.
It goes without saying that there is no particular limitation. (First Embodiment) FIG. 1 is a schematic explanatory view showing a method for forming an insulator layer on a conductor layer according to the present invention. In the figure, the first conductor layer 11 on the surface layer is a copper foil or a conductor circuit described in detail later. The insulator layer 12 is formed on the first conductor layer 11 by the forming method according to the present invention described below. The insulator layer 12 is the first conductor layer 1
It constitutes an insulator layer between the first and second conductor layers (described later).

Insulator layer 1 provided on the first conductor layer 11
As the method of forming No. 2, the following two methods are possible. (One Method) Insulating resin powder 13 such as epoxy resin is uniformly sprayed and applied onto the first conductor layer 11. In this case, the nozzle 14 is used so that the insulating resin powder 13 can be uniformly sprayed on the flat surface. The insulating resin powder 13 is sprayed from the nozzle 14 and drops toward the first conductor layer 11, where it is deposited or deposited to form a uniform insulator layer 12. (Another Method) First, the conductor circuit provided on the first conductor layer 11 is charged, and the insulating resin powder 13 is charged to a charge opposite to the charge of the conductor circuit. Then, the electrically insulating resin powder 13 is uniformly sprayed on the conductor circuit (not shown) on the first conductor layer 11 to form the insulator layer 12. As described above, by applying the mechanism of electrostatic coating, the insulating film formed by the insulating powder formed on the conductor circuit provided on the first conductor layer 11 is electrically connected at the time of formation. It is possible to firmly adhere due to the attractive force.

The method using the charged powder is limited to the case of the conductor circuit provided on the copper foil or the metal plate, and the method of the above () is used for the case of the conductor circuit pattern provided on the insulator. One method) is used. This is because when embedding between conductor circuit patterns is taken into consideration, there is no conductor that applies an electric charge opposite to that of the powder between the conductor circuit patterns provided on the insulator. This is because it doesn't go in between.

The insulator layer formed by the above method is
By heating and baking, it becomes possible to form a strong adhesive force in the region between the copper foil and the conductor circuit. The firing temperature must be higher than the curing temperature of the resin used. Then, by this firing, the film itself becomes a strong film. Further, when the insulator layer is formed on the metal plate on which the circuit is formed, the unnecessary metal plate is peeled off after the formation.

When it is necessary to form a vertical electrical connection (corresponding to a conventional through hole) in the insulator layer for conduction between the conductor layers, the following manufacturing method is applied. FIG. 2 is a schematic explanatory view showing a method for forming the above electrical connection portion according to the present invention. In FIG. 2, first, a plating resist (not shown) such as a photoconductor dry film is attached to the entire surface of the first conductor layer copper foil 21, and then a mask film that deposits plating on the connection portion is used. Exposure and development are performed to form holes for connecting portions, that is, through holes, in the plating resist. Then, plating is performed on the entire surface, and the plating is deposited only on the connection hole portion,
After forming the connection block 22, the plating resist is removed. Note that, in FIG. 2, the first conductor layer copper foil 21 is shown as a single plate-shaped body, and the connection block 22 is formed on it, but this shows a connection block for grounding, for example. It is because it is a thing. When the first conductor layer copper foil 21 is a conductor circuit pattern, the connection block is provided at a predetermined position for connection of the pattern. In this way, the connecting portion is plated with the connecting portion mass 2 such as a metal conductor column or prism.
2 is formed. The shape of the connecting portion mass 22 is not limited to the above-described column or prism, and may be any shape. The height of the connection block 22 is formed to be the same as the height of the insulating layer provided between the conductor layers.

After that, the unnecessary plating resist is peeled off, and an insulator layer is formed in the region other than the connection portion by the above-mentioned insulator layer forming method. The state in that case and the state of the step of removing the insulator layer on the conductor mass for the connecting portion are shown in FIGS.
This will be described with reference to the schematic diagram of. First, when the insulator layer is formed, as shown in the left diagram of FIG.
Since the insulator powder 32 is also deposited on the surface 1, the portion is scraped off with an appropriate spatula 33 or the like as shown in the right diagram of FIG. Reference numeral 34 denotes a lump of the insulator powder 32 scraped off from the connecting portion conductor lump 31 by the spatula 33 or the like. In addition, as shown in FIG. 4, after forming the conductor mass 42 for the connection portion, the insulator layer 43 is formed, and after heat curing, polishing is performed by an appropriate method such as brush polishing or buff polishing to remove unnecessary insulators. May be removed, and the head 44 of the conductor mass 42 for connection part may be exposed.

The production of the conductor mass of the connecting portion as described above is not limited to the above-mentioned plating method, but a conductive material such as copper powder, silver powder, gold powder or other metal powder may be coated with epoxy. Make a paste by mixing appropriate amount of resin such as and an organic solvent such as toluene, and apply this conductor paste to the position of the connection portion using a dispenser or the like, or
Alternatively, batch printing may be performed using a screen plate. Then, the lump state applied by these applying methods may be cured by removing the organic solvent by air drying or warm air to form the connection portion lump. As another method of forming the connection block, the method shown in FIG. 5 may be used. Figure 5
The left side of FIG. 3 is an explanatory view of the manufacturing method, and the right side of FIG. As shown in the left figure, this method uses a ball bond type wire bonding device to
Alternatively, a metal wire such as aluminum may be directly bonded onto the conductor layer 51, and the wire 54 may be cut at a predetermined height position 52 to form a connection block. In addition, 53
Indicates a crushed ball after bonding, and this and wire 5
4, a metal block corresponding to the connection block 22 is formed. This completes the formation of the insulator layer on the first conductor copper foil and the formation of the electrical connection between the first conductor layer and the second conductor layer.

Next, a method for forming the first conductor copper foil as a conductor circuit pattern will be described. First, an etching resist pattern is formed on the first conductor copper foil.
Then, in order to protect the connecting portion with the second conductor layer, an etching resist is formed on the entire connecting portion side. Next, unnecessary copper is removed with an appropriate etching solution. This completes the formation of the first conductor layer circuit pattern. The formation of the first conductor layer circuit pattern may be performed after the final formation of the conductor layer.

The above-mentioned method is a manufacturing method when the insulating layer is formed on the copper foil. Here, the insulating layer is formed on the first conductor layer circuit pattern by the following method. Since it may be formed, the forming method will be described with reference to the schematic process diagrams of FIGS. As shown in FIG. 7A, a plating resist 702 is formed on a metal plate 701 such as a stainless steel plate having a mirror-finished surface, and using this, as shown in FIG. 7B. The conductor circuit pattern 703 is formed by pattern plating. The mirror-finished stainless steel plate is used because the conductor circuit can be easily separated from the stainless steel plate after the laminated substrate is formed. Further, the formation of the conductor circuit is not limited to the above pattern plating, and for example, the conductor paste may be formed by printing using a screen plate or the like. Next, as shown in FIG. 7C, a plating resist 704 for connecting portion plating is formed in a region other than the connecting portion forming position of the conductor circuit pattern 703, and then plating is performed, as shown in FIG. 7D. Thus, the connection block 705 is formed at the connection formation position. Then, by removing the plating resist 704, as shown in FIG. 7E, a connection block 705 is formed at a predetermined position of the conductor circuit pattern 703 on the metal plate 701 as required.

An insulator layer is formed on the conductor circuit or on the conductor circuit on which the connection block is already formed, for example, by the method using the insulator powder 13 described above. The peeling of the stainless steel plate is performed after forming the insulating layer, but may be peeled after forming the multilayer substrate by laminating the required number of layers. Further, in the case of multilayering by pressing described in Example 2 described later, the stainless plate is used as it is as a pressing jig, and peeled off after the pressing is completed.

Next, in order to form the second conductor circuit pattern layer, an electroless plating film used for supplying electric power for electrolytic plating is formed on the surface of the insulator layer. A conductor circuit pattern is formed on the electroless plated film by using a plating resist by a method such as electrolytic plating only on a necessary portion. Then, the plating resist is peeled off and removed. Further, if necessary, the connection portion between the second conductor layer and the third conductor layer is formed by the above-described method. In this case, if the electroless plating film other than the unnecessary conductor circuit portion and the connection portion are formed, the electroless plating film other than the connection portion and the conductor circuit portion is removed with an appropriate etching solution. The formation of this conductor circuit layer is not limited to the above-mentioned pattern plating method, and the conductive paste is printed and applied using a screen plate or the like, or a metal foil such as a copper foil is pasted, followed by a method such as etching. Alternatively, the circuit may be formed in step (1), and then the connection portion may be formed by the method described above. Alternatively, a circuit-formed copper foil on which a circuit is formed in advance may be attached to the copper foil by a method such as etching or punching, and the connection portion may be formed by the above-described method, if necessary.

Next, an insulator layer is formed between the second conductor layer and the third conductor layer, and the insulator layer between the first conductor layer and the second conductor layer described above is formed. It is carried out in the same manner as the method for forming. As described above in detail, in the method of forming the insulating layer on the conductive layer on which the circuit formation is completed by the method according to the present invention, the insulating powder sufficiently enters even between the miniaturized circuit patterns. Therefore, it is very effective in securing the quality and characteristics of the substrate.

Although briefly described below, the method for forming the third conductor layer is the same as the method for forming the second conductor layer. Then, the formation of the insulator layer between the third conductor layer and the fourth conductor layer is performed by the same method as the above-described method of forming the insulator layer between the first conductor layer and the second conductor layer. To implement. Finally, the fourth
The conductor layer is formed by the same forming method as the above-mentioned second conductor layer. Then, the unnecessary stainless steel plate is peeled off. Since the surface of the stainless steel plate is mirror-finished, it can be easily peeled off as described above. When the circuit of the first conductor layer is not formed, the circuit can be formed by etching by a method using a dry film on the release surface of the stainless steel plate.

The production of the printed circuit board according to the present invention is completed through the above steps, but thereafter, solder resist coating, solder coating, external processing, etc. are carried out according to the specifications.
A printed circuit board is formed. FIG. 6 shows a manufacturing flowchart of the above-described first embodiment, that is, a manufacturing method of a printed circuit board having four connecting layers and four conductor layers. In the present embodiment, the substrate having four conductor layers has been described as an example, but as is clear from the above description, a printed circuit board in which the first conductor layer to the fourth conductor layer are sequentially stacked. 2 shows a manufacturing method of. In this case, as described above, the number of conductor layers is not limited to four, and two or more layers having a desired number of layers can be applied.

(Second Embodiment) FIG. 8 is an explanatory view of a manufacturing method by means of a sectional view of a main part showing a second embodiment of the present invention. In the present embodiment, unlike the case of the first embodiment, as shown in FIG.
As can be seen from the above, a core layer or a conductor layer having, for example, first to fourth conductor layers provided with a conductor layer and a connection portion is formed for each layer if necessary, and these are pressed by a press or the like. The manufacturing method of the printed circuit board formed by lamination molding is shown.

In FIG. 8, first, the first conductor layer 811 is formed.
A connection block 813 for electrically connecting the first and second conductor layers is provided at a predetermined position above, and the first and second conductor layers are insulated by the method described in the first embodiment. Insulator layer 8
A first core layer 810 having 12 formed thereon is prepared. In this case, since the upper part of the connecting portion mass 813 is headed out by the method shown in the embodiment of FIG. 3 or FIG. 4, the conductor is exposed. Next, a connection block 823 for electrically connecting the second and third conductor layers is provided at a predetermined position on the second conductor layer 821, and the second and third conductor layers are insulated by the same method. A second core layer 820 on which an insulating layer 822 is formed is prepared. The above-mentioned head start is also implemented here. Further, a connecting portion block 83 for electrically connecting the third and fourth conductor layers to a predetermined position on the third conductor layer 831.
3 is provided and an insulator layer 832 for insulating between the third and fourth conductor layers is formed by the same method as the third core layer 830.
To prepare. Here again, the above-mentioned head start is implemented.
Further, a fourth conductor layer 841 made of copper foil or the like and having a circuit pattern formed as needed is prepared.

In the formation of each core layer described above, the firing of the insulating layer by heat is not performed at the curing temperature, but is performed at a temperature not lower than the glass transition temperature and is performed by heating until the resin is once melted. Has become. By this method, the film formed of the powder becomes an insulating film in a melted and solidified state, and there is an advantage that handling is easy. Then, each layer member prepared as described above, that is, the first core layer 8
10, the second core layer 820, the third core layer 830, and the fourth conductor layer 841 are stacked with high positional accuracy, and hot pressing or the like used in the manufacture of general printed circuit boards is performed to cure the resin. By heating above, the multilayer substrate according to the present invention is obtained. In some cases, each layer member prepared as described above, that is, the first core layer 81.
0, the second core layer 820, the third core layer 830 and the fourth conductor layer 841 formed of a metal foil may be prepared and stacked to form a four-layer board substrate by a method such as a conventional hot press. .
At this time, the fourth conductor layer 841 on which the circuit is not formed
Finally, the circuit is formed by a method such as etching. FIG. 9 shows a simple flow chart of the method for manufacturing the printed circuit board of the second embodiment.

As described above in detail with reference to the first and second embodiments, the metal nodules for electrically connecting the conductor layers are connected to each other on the conductor layer composed of the metal foil or the conductor circuit pattern. After it is formed as a part, a fine powder of the insulating powder is sprayed in the form of a mist to uniformly deposit and form the insulating layer,
Since it is possible to form a thin insulator layer that cannot be manufactured by the conventional method using an insulating sheet such as a prepreg, it is possible to easily achieve a large reduction in thickness for a printed circuit board having the same number of layers. In addition, since a fine powder of insulating powder is used, even fine conductor circuit patterns can be sufficiently filled in between the patterns, and a good insulating layer can be obtained, thus ensuring strict design specifications and characteristics of the printed circuit board. To be done.

Further, since a small lump of metal is formed and used to establish electrical connection between the conductor layers, electrical connection with an extremely small area, which has been impossible with the conventional through-hole connection. This makes it possible to configure the printed circuit board and contributes to downsizing of the printed circuit board.

[0030]

As described above in detail, according to the present invention, the conductor layers are laminated via the insulator layer, and the adjacent conductor layers are electrically connected. In a method of manufacturing a printed circuit board, after forming a conductor mass for making an electrical connection between conductor layers on a conductor layer made of a metal foil or a conductor circuit pattern as a connection portion, a fine powder of insulating powder Since it is sprayed in the form of a mist and uniformly deposited to form an insulating layer, it is possible to form a thin insulating layer that cannot be manufactured by a method using an insulating sheet such as a conventional prepreg. Thinning is easily achieved with good quality. In addition, since finely divided insulating powder is used in the formation of the insulating layer, even a fine conductor circuit pattern can be sufficiently filled between the patterns, a good insulating layer can be obtained, and the printed circuit board can be strict. Design specifications and characteristics are secured. Such an insulating layer forming method of the present invention, compared with a conventional substrate manufactured by pouring resin melted by hot pressing between conductor circuits,
Since the resin has sufficiently entered between the circuits before melting,
This is because it makes it possible to manufacture a substrate of very high quality.
Also, because the structure is such that a conductor block is formed and used to make electrical connection between conductor layers, it is possible to make an electrical connection structure with a very small area, which was not possible with conventional through-hole connections. , Greatly contributes to downsizing of printed circuit boards. And, compared to the conventional electrical connection between the conductor layers by through holes, in the present invention, since the connection is made by the conductor mass, not only can the resistance of this connection portion be lowered, There is an advantage that it can withstand a large current. Furthermore, in the practical application of the substrate,
Since the heat generated from the mounted electronic parts and integrated circuit parts can be easily diffused and dissipated through the connection block mass,
This has the effect of contributing to higher density of board mounting.
In addition, the through hole that was always used in the past is no longer necessary, and the connection part is not hollow as in the past, so it is formed in the middle layer like the inner bias through hole and it is necessary to fill the inside with resin etc. However, there is an advantage that it is not necessary, and thus there is an effect that the thickness of the substrate can be further stabilized.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing a method for forming an insulator layer on a conductor layer according to the present invention.

FIG. 2 is a schematic explanatory view showing a method for forming an electrical connection portion according to the present invention.

FIG. 3 is a schematic diagram illustrating a state of a step of removing an insulating layer on a conductor block for a connecting portion according to the present invention.

FIG. 4 is a schematic view for explaining another aspect of the step of removing the insulating layer on the conductor mass for connection portion according to the present invention.

FIG. 5 is an explanatory view showing another method for forming a connection block according to the present invention.

FIG. 6 is a manufacturing flowchart of the first embodiment of the present invention.

FIG. 7 is an explanatory view showing a method for forming a connection portion block of the present invention.

FIG. 8 is an explanatory view of a manufacturing method according to a main part sectional view showing a second embodiment of the present invention.

FIG. 9 is a manufacturing flow chart of the second embodiment of the present invention.

[Explanation of symbols]

 11, 811 First conductor layer 12, 43, 812 Insulator layer 13 Insulating resin powder 14 Nozzle 21 First conductor layer Copper foil 22, 813, 823, 833 Connection part block 31 Conductor block for connection part 32 Insulation Body powder 33 Spatula 34 Lump of insulating powder 42 Conductor lump for connection portion 44 Head 51 Conductor layer 52 Predetermined height position 53 Crushed ball after bonding 54 Wire 701 Metal plate 702, 704 Plating resist 703 Conductor circuit pattern 810 No. 1 core layer 812, 822, 832 insulator layer 705, 813, 823, 833 connection block 820 second core layer 821 second conductive layer 830 third core layer 831 third conductive layer 841 fourth conductive layer

Front page continuation (72) Inventor Ho Nakakuki 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (5)

[Claims] 1. A multilayer wiring type printed circuit board in which vertically adjacent conductor layers are laminated with an insulator layer interposed therebetween, and the adjacent conductor layers are electrically connected to each other. In the manufacturing method of 1., after forming a conductor connecting portion for electrically connecting between the conductor layers on the conductor layer formed of a metal foil or a conductor circuit pattern, the insulating powder is sprayed in a mist state. And uniformly depositing the insulating layer to form the insulating layer. 2. When the insulating powder is sprayed / precipitated on the conductive layer in the form of powder mist, the insulating powder is charged, and the conductive layer is charged to a charge opposite to that of the insulating powder. The method of manufacturing a printed circuit board according to claim 1, wherein the printed circuit board is charged. 3. The method for manufacturing a printed circuit board according to claim 1, wherein the conductor connecting portion is formed by applying or printing a conductor powder formed in a paste form to form a conductor mass. 4. The method of manufacturing a printed circuit board according to claim 3, wherein the conductor block is a metal block formed by ball bonding type wire bonding. 5. A lower conductor layer of the conductor layers which are vertically adjacent to each other is formed, the conductor connecting portion is formed on the lower conductor layer, and then the insulator layer is formed. 2. The upper conductor layer is formed after the head of the conductor connecting portion is mechanically processed to remove a part of the insulator layer deposited on the head. Method of manufacturing printed circuit board.