JP2018037430A - Multi-layer printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layer printed board capable of easily completing an EMI countermeasure without frequently repeating layout.SOLUTION: A multi-layer printed board constructs a trimmer capacitor by soldering a hexagonal nut 102 to a land 202 of a through-hole 104 of which a part of a surface is cut. By using the trimmer capacitor, a band-pass filter or a band-elimination filter or the like is constructed on a multi-layer printed board, thereby easily realizing an EMI countermeasure.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a multilayer printed circuit board.

  Especially in industrial applications, the scale of electronic circuits in recent years has been increasing. The multilayer printed circuit board is an important element constituting such a large-scale electronic circuit. In recent digital electronic circuits, the frequency of clocks used tends to increase, and measures against EMI (electromagnetic interference) are required. In addition, with the increase in the frequency of circuits, stray capacitance, stray inductance, and the like generated in the printed pattern of a multilayer printed board cannot be ignored.

  As a prior art document that seems to be related to the present invention, there is Patent Document 1 in which a technique for forming a trimmer capacitor on a printed circuit board is disclosed.

JP-A-5-55721

  When the shape and length of the wiring pattern of the printed board changes, the level of radiation noise increases or decreases, and the frequency of radiation noise varies. For this reason, as a countermeasure against EMI, the printed circuit board manufacturing site repeats a cut-and-try operation in which a printed circuit board is prototyped, an EMI test is performed, a printed circuit board with a changed wiring pattern is further prototyped, and an EMI test is performed. Yes. This is very inefficient.

  The present invention has been made in view of such a point, and an object of the present invention is to provide a multilayer printed circuit board that can easily complete EMI countermeasures without repeating design frequently.

  In order to solve the above problems, the multilayer printed board of the present invention includes a top single-layer board on which a printed pattern with a conductor is formed on the surface, a bottom single-layer board on which a conductor layer with a conductor is formed on the surface, One or more intermediate single-layer substrates having a printed pattern formed by a conductor on the surface and constituting a multilayer substrate sandwiched between the uppermost single-layer substrate and the lowermost single-layer substrate, and the intermediate single-layer substrate Is formed on the inner wall of the through hole penetrating the lowermost single-layer substrate and has electrical continuity with the conductor layer existing at the periphery of the through-hole of the lowermost single-layer substrate, and the through-hole periphery of the uppermost single-layer substrate And a land which is a part of the printed pattern provided on the conductor and a conductor plating formed so as not to have electrical continuity. Furthermore, a male screw housing part formed with a female screw fixed to the land with electrical conduction, and a male screw housed in the male screw housing part and constituting a trimmer capacitor between the conductor plating and the land are provided. .

According to the multilayer printed circuit board of the present invention, it is possible to realize a multilayer printed circuit board that can easily complete EMI countermeasures without repeating design frequently.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is the external appearance perspective view of the multilayer printed circuit board which is embodiment of this invention, and the external appearance perspective view of a back side. It is the external appearance top view which looked at the trimmer capacitor formed on the multilayer printed circuit board from the front side, and sectional drawing. Schematic diagram showing an assembly of single-layer substrates on which the multilayer printed circuit board is based, schematic diagram showing a multilayer printed circuit board obtained by crimping an assembly of many single-layer substrates, and a through hole for a trimmer capacitor on the multilayer printed circuit board FIG. 2 is a schematic view showing a state in which a through hole is formed, and a cross-sectional view of a multilayer printed board in which a through hole is formed. A cross-sectional view showing a state in which the first copper plating is applied to the multilayer printed board in which the through hole is formed, and a cross-sectional view showing a state in which the through-hole of the multilayer printed board subjected to the copper plating is subjected to a cutting process; After printing the printed pattern on the multilayer printed circuit board with the etching resist, the cross-sectional view showing the state where the through hole is further closed with the resin plate, and after removing the etching resist, the state where the nut is soldered to the printed pattern It is a cross-sectional view shown. It is the external appearance top view and sectional drawing which looked at the trimmer capacitor formed on the multilayer printed circuit board in another embodiment from the front side.

[Appearance of multilayer printed circuit board 101]
FIG. 1A is an external perspective view of the front side of a multilayer printed circuit board 101 according to an embodiment of the present invention. FIG. 1B is an external perspective view of the back side of the multilayer printed circuit board 101.
As shown in FIG. 1A, a metal hexagon nut 102 is provided on a part of the multilayer printed board 101, and a screw 103, which is a metal minus screw, is attached to the hexagon nut 102.
As shown in FIG. 1B, a through-hole 104 is formed at a portion of the multilayer printed board 101 where the screw 103 is attached. In addition, alignment marks 105 which are holes for positioning are provided at the four corners of the multilayer printed circuit board 101.

[Appearance and Internal Configuration of Trimmer Capacitor Formed on Multilayer Printed Circuit Board 101]
FIG. 2A is an external top view of the trimmer capacitor formed on the multilayer printed circuit board 101 as viewed from the front side.
FIG. 2B is a cross-sectional view of the multilayer printed circuit board 101 on which a trimmer capacitor is formed when cut along AA in FIG. 2A.
2C is a cross-sectional view of the multilayer printed circuit board 101 in a state where the capacitance of the trimmer capacitor is changed from the state of FIG. 2B.

As shown in FIG. 2B, the multilayer printed board 101 is configured by alternately stacking intermediate copper foil layers 204 and resin layers 206.
As shown in FIGS. 2A and 2B, a land 202 is formed on a printed pattern 201 formed on the surface of the multilayer printed board 101, and a through hole 104 is formed at the center of the land 202. At this time, the copper plating layer 203 formed inside the through hole 104 includes an intermediate copper foil layer 204 formed between the layers of the multilayer printed board 101 and a back side copper formed on the back side of the multilayer printed board 101. Electrical connection with the foil layer 205 (conductor layer) is achieved.

In the multilayer printed circuit board 101 formed in this way, the through hole 104 is cut with a drill or the like from the surface side of the multilayer printed circuit board 101 to form a copper plating layer 203 (conductor) formed inside the through hole 104. Remove some of the plating. In the through hole 104, a space 104a from which the copper plating layer 203 has been removed is formed.
Then, the printed pattern 201 and the land 202 formed on the surface of the multilayer printed circuit board 101, which were originally electrically connected to the copper plating layer 203 formed inside the through hole 104, are formed by a drill or the like. Electrical insulation is generated by partially removing the copper plating layer 203 by the cutting process.
The thickness of the through hole 104 is such that the shaft 103a of the screw 103 can be accommodated and the shaft 103a and the copper plating layer 203 are not in contact with each other. That is, the shaft 103a and the copper plating layer 203 serve as electrodes for forming a trimmer capacitor using air existing between them as a dielectric.

  A printed pattern 201 is formed on the front side of the multilayer printed circuit board 101 for mounting components. On the other hand, the printed pattern 201 may be formed on the back side of the multilayer printed circuit board 101 as in the case of the front side, or parts may not be mounted. When components are not mounted on the back side of the multilayer printed circuit board 101, a so-called “solid earth” called “print pattern 201 by etching” is not formed, and the entire surface remains the back side copper foil layer 205 which is a ground node.

A hex nut 102 is soldered to a land 202 formed on the front side of the multilayer printed board 101 in the through hole 104. In addition, a screw 103 is attached to the hex nut 102. Even if the screw head of the screw 103 is positive, the function as a trimmer capacitor is achieved, but when adjusting the trimmer capacitor, it is necessary to use a non-metallic screwdriver such as synthetic resin, so the screw head is negative. It is preferable that it is formed because it is difficult to damage non-metallic drivers.
The material of the hex nut 102 needs to be a metal that can be soldered because of the soldering. For example, iron and its alloy, brass, etc. are mentioned.
Since the material of the screw 103 does not require soldering, the object can be achieved if it is a metal. For example, in addition to iron and its alloy, brass, etc., which are the same as the hexagonal nut 102, an aluminum alloy that is difficult to solder can be used.

The hexagon nut 102 and the screw 103 are electrically connected to a printed pattern 201 formed on the surface of the multilayer printed board 101. In many cases, the print pattern 201 is an unbalanced connection signal line or a balanced connection hot-side signal line. On the other hand, the copper plating layer 203 formed inside the through hole 104 is connected to an unbalanced connection ground node or a balanced connection cold side signal line.
Thus, the hexagon nut 102, the screw 103 attached to the hexagon nut 102, and the copper plating layer 203 formed inside the through hole 104 form a trimmer capacitor to be inserted on the signal path.
A multilayer printed board 101 according to an embodiment of the present invention is a multilayer printed board 101 in which the trimmer capacitor is integrally formed.

As shown in FIG. 2C, when the screw 103 attached to the hexagon nut 102 constituting the trimmer capacitor is loosened, the area of the surface of the screw 103 facing the shaft 103a and the copper plating layer 203 inside the through hole 104 is increased. Decrease. As a result, the capacitance of the capacitor formed between the screw 103 and the copper plating layer 203 decreases.
When adjusting the capacitance of the trimmer capacitor, it is preferable to turn the screw 103 with a non-metallic screwdriver in order to prevent noise from entering.

In order to adjust the capacitance of the trimmer capacitor, the multilayer printed circuit board 101 is brought into an actual operation state, and is adjusted while measuring a predetermined signal from the multilayer printed circuit board 101. First, necessary components are mounted on the multilayer printed circuit board 101 to make the product semi-finished. Next, a prescribed power supply and signal are applied to the multilayer printed circuit board 101 to put the electronic circuit configured on the multilayer printed circuit board 101 into an actual operation state. Then, a certain probe is mounted on the multilayer printed circuit board 101, and the screw 103 is turned while measuring the detected signal with a predetermined measuring device or the like, thereby adjusting the capacitance of the trimmer capacitor.
In order to fix the capacitance of the trimmer capacitor that has been adjusted, an adhesive such as an ultraviolet curable resin may be applied to the screw 103 and the hexagon nut 102 and solidified.

[Manufacturing Process of Multilayer Printed Circuit Board 101]
Hereinafter, the manufacturing process of the multilayer printed circuit board 101 which concerns on embodiment of this invention is demonstrated.
FIG. 3A is a schematic diagram showing an assembly of single-layer substrates that are the basis of the multilayer printed circuit board 101.
FIG. 3B is a schematic view showing a multilayer printed circuit board 101 to which an assembly of a large number of single-layer boards is pressure-bonded.
FIG. 3C is a schematic diagram illustrating a state in which a through hole 104 for a trimmer capacitor is formed in the multilayer printed circuit board 101.
3D is a cross-sectional view of the multilayer printed circuit board 101 in which the through hole 104 shown in FIG. 3C is formed.

  First, as shown in FIG. 3A, single-layer substrates 301a, 301b,... 301n on which a printed wiring pattern is formed on one side and serving as a base of the multilayer printed circuit board 101 are prepared. In FIG. 3A, the single layer substrate 301 a is disposed on the top of the single layer substrate group and becomes the surface of the multilayer printed circuit board 101. Similarly, in FIG. 3A, the single-layer board 301n is arranged at the lowest position of the single-layer board group and is the back surface of the multilayer printed board 101.

  Alignment marks 105 are provided at the four corners of the single-layer substrates 301a, 301b,. The uppermost single-layer substrate 301a (uppermost single-layer substrate) and the lowermost single-layer substrate 301n (lowermost single-layer substrate) are not formed with a printed wiring pattern, and the entire surface is plated with copper. Arrange the layer substrate. Although not shown, a single-layer substrate 301b sandwiched between the uppermost single-layer substrate 301a and the lowermost single-layer substrate 301n,... 301m (intermediate single-layer substrate) is printed on the front or back surface in advance. A wiring pattern is formed.

Next, as shown in FIG. 3B, each single layer substrate 301a, 301b,... 301n is positioned through an alignment mark 105 through a pin (not shown), and each layer of the single layer substrates 301a, 301b,. The multilayer printed circuit board 101 is configured by pressure bonding.
Next, as shown in FIG. 3C, a hole for forming a trimmer capacitor is formed at a desired location on the multilayer printed board 101 to form a through hole 104. Then, as shown in FIG. 3D, the cross section of the intermediate copper foil layer 204 constituting the printed wiring pattern and the resin layer 206 of the single-layer substrates 301a, 301b,. Moreover, since it is a stage before performing etching, the front side copper foil layer 302 which is a stage before the print pattern 201 is formed exists on the front side of the multilayer printed circuit board 101.

4E is a cross-sectional view illustrating a state in which copper plating is applied to the multilayer printed board 101 in which the through hole 104 is formed, as illustrated in FIGS. 3C and 3D.
FIG. 4F is a cross-sectional view showing a state in which the through hole 104 of the multilayer printed board 101 subjected to copper plating shown in FIG. 4E is cut with a drill.
FIG. 4G shows an etching resist for forming the printed pattern 201 printed on the multilayer printed circuit board 101 in which the through hole 104 is drilled by the through hole 104 shown in FIG. 4F, and the dry films 402a and 402b are formed in the through hole. FIG.

FIG. 4H shows the multilayer printed circuit board 101 on which the etching resist is printed and the dry films 402a and 402b shown in FIG. 4G are etched, and the copper foil is partially removed to form the printed pattern 201. 5 is a cross-sectional view showing a state in which the etching resist 401 and the dry films 402a and 402b are removed, and the hexagon nut 102 is soldered to the land 202 formed on the upper surface of the through hole 104.
That is, the manufacturing method of the multilayer printed circuit board 101 according to the embodiment of the present invention is a manufacturing method applying a tenting method using a dry film.

As shown in FIG. 4E, when copper plating is applied to the through hole 104 formed in the multilayer printed circuit board 101 in FIG. 3D, a copper plating layer 203 is formed on the front and back surfaces of the multilayer printed circuit board 101 and inside the through hole 104. It is formed. Then, electrical conduction is achieved through the copper plating layer 203 in the intermediate copper foil layer 204 exposed in the cross section inside the through hole 104. Moreover, the thickness of the front side copper foil layer 302 and the back side copper foil layer 205 increases when the copper plating layer 203 overlaps. Up to this point, the procedure for forming the through hole 104 in the conventional general multilayer printed circuit board 101 is exactly the same.
Next, as shown in FIG. 4F, the through hole 104 is cut with a drill. In this cutting process, the land 202 of the printed pattern 201 is cut to such a depth that electrical insulation with the copper plating layer 203 formed inside the through hole 104 is achieved. Then, in the through hole 104, a space 104a from which the copper plating layer 203 has been removed is formed.

Next, as shown in FIG. 4G, an etching resist 401 for forming the print pattern 201 is applied to the front and back surfaces of the multilayer printed board 101. At that time, an etching resist 401 is applied including the peripheral portion of the through hole 104.
If only the etching resist 401 is applied, an etching solution such as ferric chloride enters the hollow through hole 104 in the etching state, and the copper plating layer 203 inside the through hole 104 is eroded. . Therefore, the dry film 402a and the dry film 402b are attached to the through hole 104 on the front side opening portion of the multilayer printed board 101 and the back side opening portion, respectively, and the copper plating layer 203 inside the through hole 104 is removed from the etching solution. Protect.

  Then, the multilayer printed circuit board 101 is etched from the state shown in FIG. 4G. The inside of the through hole 104 is protected from the intrusion of the etching solution by the etching resist 401 and the dry films 402a and 402b. When the etching is finished, the dry films 402a and 402b and the etching resist 401 are removed. As a result, a copper foil land 202 is formed around the through hole 104 on the surface of the multilayer printed circuit board 101. A hexagon nut 102 is fixed to the land 202 by soldering. Thus, the components of the trimmer capacitor shown in FIG. 4H are completed. When the screw 103 is attached to the hexagon nut 102, the trimmer capacitor shown in FIG. 2 is completed.

Trimmer capacitors are usually available as a single part. However, the size of the trimmer capacitor is as large as about 5 to 7 mm in diameter. In addition, an ultra-small surface mount component trimmer capacitor is commercially available but is expensive.
The multilayer printed circuit board 101 according to the embodiment of the present invention has a structure in which a trimmer capacitor and the multilayer printed circuit board 101 are integrated, and can be realized by a hexagon nut 102 and a screw 103 that are generally very easy to obtain. Since the hexagon nut 102 may be soldered to the through hole 104, a very low-cost trimmer capacitor can be realized. It is also possible to increase the maximum capacitance of the trimmer capacitor by changing the dimensions of the screw and the through hole 104.
The capacitance of the trimmer capacitor that can be realized by the hexagon nut 102 is about several to several tens of pF. However, this level of capacitance is sufficient for countermeasures against EMI, which is an electromagnetic wave in a high frequency region.

In addition, although the hexagon nut 102 was illustrated as a component which accommodates a screw, since the objective is to accommodate a screw, it does not necessarily need to be the hexagon nut 102. Since the internal thread which accommodates the axis | shaft 103a of the screw | thread 103 should just be formed in the metal which can be soldered, you may cut | disconnect an internal thread to a thin steel plate, for example.
As a superordinate concept that includes such a thin steel plate on which the female screw is formed and the hexagon nut 102, it will be referred to as a male screw housing component on which the female screw is formed.

  In the above-described embodiment, the trimmer capacitor using the combination of the normal screw 103 that requires a female screw and the hexagon nut 102 that provides the female screw is illustrated, but the type of screw is not limited thereto. A so-called tapping screw that does not require an internal thread can also be used. In this case, instead of the hexagon nut 102, a thin metal plate with a hole is soldered to the land 202.

[Method of fixing nuts arranged on multilayer printed circuit board 101]
3 and 4 do not mention a method of soldering by accurately arranging the hexagon nut 102 on the land 202 of the multilayer printed circuit board 101. FIG. If the hexagon nut 102 is not correctly placed at the center of the through hole 104, the shaft 103a of the screw 103 will come into contact with the copper plating layer 203 inside the through hole 104, and will no longer serve as a trimmer capacitor. For this reason, a method for accurately positioning the hex nut 102 or the male screw housing component in the through hole 104 must be considered. Various methods are conceivable for this.

FIG. 5A is an external top view of the trimmer capacitor formed on the multilayer printed circuit board 101 as viewed from the front side.
FIG. 5B is a cross-sectional view of the multilayer printed circuit board 101 on which a trimmer capacitor is formed when cut along AA in FIG. 5A.
FIG. 5C is a cross-sectional view of the multilayer printed circuit board 101 in a state where the capacitance of the trimmer capacitor is changed from the state of FIG. 5B.
The trimmer capacitor shown in FIGS. 5A, 5B, and 5C differs from the trimmer capacitor shown in FIGS. 2A, 2B, and 2C in that a sleeve 501a that forms a step instead of the hexagon nut 102 as a male screw housing part. The clinching fastener 501 having The land 202 formed on the surface of the multilayer printed circuit board 101 is subjected to counterboring for accommodating the sleeve 501a of the clinching fastener 501. This counterboring process is the stage of FIG. 4E or FIG. 4F, that is, before or after cutting the through hole 104 with a drill, applying the etching resist 401 of FIG. 4G to the front and back surfaces of the multilayer printed board 101, The through hole 104 is formed at a stage before the dry films 402a and 402b are attached and closed.

In addition to the clinching fastener 501 and the counterbore processing shown in FIG. 5, various methods are conceivable as a method of accurately positioning the male screw housing component on the land 202. Listed below.
(1) The land 202 is etched according to the shape of the hexagon nut 102. The hexagon nut 102 is arranged in a hexagonal empty pattern of the multilayer printed circuit board 101 where the lands 202 are removed by etching. That is, the thickness of the copper plating layer positions the hexagon nut 102. The same applies to the case where a metal plate having a female thread is used instead of the hexagon nut 102.
(2) According to the shape of the hex nut 102, three pins are implanted in the land 202 and arranged in an equilateral triangle shape. The pin holds three sides of the hex nut 102.
(3) From the back side of the multilayer printed board 101, a screw having a shaft longer than the thickness of the multilayer printed board 101 is inserted into the through hole 104, and the hexagon nut 102 is screwed into this screw. In this state, the hex nut 102 and the land 202 are soldered. When soldering is finished, the screw is removed from the hex nut 102. The same applies to the case where a metal plate having a female thread is used instead of the hexagon nut 102.

In the embodiment of the present invention, the multilayer printed circuit board 101 is disclosed.
The multilayer printed circuit board 101 constitutes a trimmer capacitor by soldering a hexagonal nut 102 to a land 202 of a through hole 104 whose surface is partially cut. By using this trimmer capacitor to form a band-pass filter, a band elimination filter or the like on the multilayer printed circuit board 101, an EMI countermeasure can be easily realized. This eliminates the time and labor required to make a trial production many times when designing the multilayer printed circuit board 101, and can greatly reduce the delivery time when designing the multilayer printed circuit board 101.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and other modifications and application examples are provided without departing from the gist of the present invention described in the claims. including.

DESCRIPTION OF SYMBOLS 101 ... Multilayer printed circuit board, 102 ... Hex nut, 103 ... Screw, 104 ... Through hole, 105 ... Alignment mark, 201 ... Print pattern, 202 ... Land, 203 ... Copper plating layer, 204 ... Intermediate copper foil layer, 205 ... Back side Copper foil layer, 206 ... resin layer, 301a, 301b, 301m, 301n ... single layer substrate, 302 ... front side copper foil layer, 401 ... etching resist, 402a, 402b ... dry film, 501 ... clinching fastener

Claims (3)

A top single-layer substrate on which a printed pattern is formed by a conductor on the surface;
A lowermost single-layer substrate having a conductor layer formed on the surface thereof; and
A printed pattern is formed by a conductor on the surface, and one or more intermediate single-layer substrates constituting a multilayer substrate sandwiched between the uppermost single-layer substrate and the lowermost single-layer substrate;
Formed on the inner wall of a through hole penetrating the intermediate single layer substrate and the lowermost single layer substrate, and has electrical continuity with the conductor layer present at the periphery of the through hole of the lowermost single layer substrate; And conductor plating formed so as not to have electrical continuity with lands that are part of the printed pattern provided at the periphery of the through hole of the uppermost single-layer substrate,
A male screw housing component formed with a female screw, which is fixed to the land with electrical conduction,
A multilayer printed circuit board comprising a male screw housed in the male screw housing component and constituting a trimmer capacitor between the conductor plating and the land. Insulation between the land and the conductor plating is achieved by removing the conductor plating by cutting from the center of the land.
The multilayer printed circuit board according to claim 1. The conductor plating also has electrical continuity with the printed pattern of one or more intermediate single layer substrates.
The multilayer printed circuit board according to claim 2.

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