JP5151519B2 - Multilayer circuit board - Google Patents

Description

  The present invention relates to a multilayer circuit board, and more particularly to a motor drive circuit board and a motor control circuit board for an electric power steering apparatus using the same.

  The electric power steering device for a vehicle drives a steering assist motor so that a suitable steering assist force is obtained in accordance with a steering torque applied to a steering wheel by a driver, a vehicle speed, or the like. The steering assist motor is driven by a motor drive circuit built in an electronic control unit (hereinafter referred to as ECU), and the amount of drive current to be supplied to the steering assist motor is also built in the ECU. Calculated by the motor control circuit.

  In recent years, ECUs incorporating these circuits have been further miniaturized, and in order to reduce the area occupied by the circuit boards on which these circuits are mounted, a method of multilayering the circuit boards is often employed. Such a multilayer circuit board has a configuration in which, for example, a copper conductor layer and an insulating layer made of ceramic or glass epoxy are laminated in multiple layers and bonded to a metal substrate (heat sink) typically made of aluminum. doing.

  Such a multilayer circuit board is provided with through holes (via holes) for connecting different conductor layers. In a general multilayer circuit board, the through hole is formed so as to connect the uppermost conductor layer on which the electronic component is placed and the lowermost conductor layer. Since the through hole is formed so as to penetrate from the uppermost conductor layer on which the heat generating electronic component is placed to the lowermost conductor layer, it often has a role of heat dissipation.

The following prior arts are known in relation to the present invention. Patent Document 1 discloses that a laminated glass ceramic circuit board is provided with a via-hole conductor made of a low-resistance metal material, and a surface conductor is formed on the via-hole conductor exposed on both main surfaces of the laminated body. Patent Document 2 discloses that in a heat dissipation structure for an electronic component in which a substrate on which an element is mounted is covered with a heat dissipation plate and a housing, a plurality of thermal vias connected to the heat dissipation plate are formed on the substrate.
JP-A-9-153679 Japanese Patent Laid-Open No. 2004-363183

  As described above, through holes formed in a general multilayer circuit board are often formed so as to pass through all the conductor layers even when it is not necessary to conduct all the conductor layers. For example, in a multilayer circuit board having three conductor layers, a through hole is formed up to the third layer, which is the lowest layer, even when the first layer, which is the uppermost layer, is connected to the next second layer. The Therefore, the through holes from the second layer to the third layer are unnecessary portions. However, since a signal is also transmitted to this portion, this portion may function as an antenna that radiates noise that causes electromagnetic interference (EMI). Such noise can occur in any through hole having the unnecessary portion. That is, a through hole that does not pass through all the conductor layers but passes through three or more conductor layers and has the above unnecessary part may cause noise that causes electromagnetic interference from the unnecessary part. is there.

  Therefore, an object of the present invention is to provide a multilayer circuit board that can reduce noise generated from a through hole formed inside the board.

The first invention is a laminated circuit portion formed by alternately laminating conductor layers and insulating layers;
A through hole connecting two or more different conductor layers;
One end is connected to the end portion of the through hole having an end portion that is not connected to any of the circuit patterns included in the conductor layer, and the power supply line included in the conductor layer is any of the circuit patterns. A termination resistor connected at the other end to the ground wire ,
The termination resistor, so as to pass through at least one of said insulating layer, characterized Rukoto such a buried resistor is formed in the stacking direction.

According to a second invention, in the first invention,
The one end of the termination resistor is connected to the end of the through hole by one of the inner conductor layers provided with the insulating layer on both sides,
Wherein the terminating resistor and the other end, by a different one of said internal conductor layer, and wherein the Rukoto connected to the power supply line or the ground line.

According to the first aspect of the invention, the end of the through hole that is not connected to any of the circuit patterns and the termination resistor that is connected to any of the circuit patterns are provided, so that the characteristic impedance mismatch in the through hole The generation of radiation noise, conduction noise, and the like caused by the above can be suppressed.
Further, according to the first aspect, the termination resistor can be easily connected to the constant potential conductor by the configuration in which the other end of the termination resistor is connected to the power supply line or the ground line.
Furthermore, according to the first invention, the termination resistor can be formed inexpensively and in a small size by using the embedded resistor as the termination resistor. Also, the component mounting area on the surface of the laminated circuit portion can be reduced by the embedded resistor.

According to the second aspect, since both ends of the termination resistor are in the inner conductor layer, the component mounting area on the surface layer of the laminated circuit portion due to the embedded resistor can be made zero.

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a perspective view including a cross section of a multilayer circuit board according to an embodiment of the present invention. The multilayer circuit board shown in FIG. 1 is formed by alternately laminating a conductor layer and an insulation layer by sandwiching an insulation layer 15 between each of the conductor layers from the first conductor layer 11 to the fourth conductor layer 14. And a metal substrate 20 provided therebelow for heat dissipation.

  The metal substrate 20 is made of a metal having good thermal conductivity such as aluminum and functions as a heat sink. The metal substrate 20 is provided so as to be in contact with the lowermost insulating layer of the insulating layer 15 and is typically thermocompression bonded to the insulating layer.

  Further, the first to fourth conductor layers 11 to 14 constituting the laminated circuit portion include a circuit pattern formed of copper or the like, and the insulating layer 15 is a synthetic material in which an insulating resin material is impregnated into glass fibers ( So-called prepreg). The first to fourth conductor layers 11 to 14 are made of a metal such as aluminum, nickel, silver, titanium, or gold instead of copper, or an alloy of these metals, or nickel plating or nickel / gold plating on the surface thereof. It may be formed of what has been. In addition, these metals, alloys, and laminated films may be formed by any one of or a combination of pressure bonding, sputtering, chemical vapor deposition, vacuum vapor deposition, and thick film printing.

  As shown in FIG. 1, the multilayer circuit portion is formed by alternately laminating first to fourth conductor layers 11 to 14 and a plurality of insulating layers 15 and thermocompression bonding. An electronic component (not shown) is placed on a certain conductor layer 11. The first conductor layer 11 that is the uppermost layer includes the first circuit patterns 110a and 110b and the adjustment pattern 111, and the second conductor layer 12 includes the second circuit pattern 120 that is the ground line. The third conductor layer 13 includes a third circuit pattern 130 that is a power supply line, and the fourth conductor layer 14 that is the lowermost layer of the conductor layer includes fourth circuit patterns 140a and 140b and connection patterns. 141 is included. The first to fourth circuit patterns 110a, 110b, 120, 130, 140a, and 140b are formed by a known process such as formation of an etching resist or etching. The adjustment pattern 111 and the connection pattern 141 are different from the circuit pattern because they do not form a circuit similar to the circuit pattern as described later, but are formed in the same manner using the same conductor.

  The laminated circuit portion is provided with three through holes 301 to 303 configured to reduce radiation noise. Both of these have a common structure in that the first conductor layer 11 and the fourth conductor layer 14 are connected through each insulating layer 15, but as described later, the presence or absence of a termination resistor and its The structure is different. Hereinafter, FIG. 1 will be described in detail with reference to FIG.

  FIG. 2 is a perspective view including a cross section of a conventional multilayer circuit board. The multilayer circuit board shown in FIG. 2 has a structure in which the characteristic configuration of the present invention is omitted from the multilayer circuit board shown in FIG. 1, and the same components are denoted by the same reference numerals and the description thereof is omitted. Omitted.

  The through holes 301 to 303 shown in FIG. 1 are interlayer connection holes formed by a well-known method in the thickness direction between the first to fourth conductor layers 11 to 14 and the plurality of insulating layers 15. More specifically, the through holes 301 to 303 are holes that penetrate from the insulating layer immediately below the uppermost first conductor layer 11 to the fourth conductor layer 14 that is the conductor layer immediately above the lowermost insulating layer. A conductor layer of metal plating such as copper plating is formed on the inner surface, and the inside is filled with resin. With such a through structure, the through-holes 301 to 303 allow the heat generated in the electronic component placed on the first conductor layer 11 to be transferred to the insulating layer (that is, the lowermost insulating layer) immediately above the metal substrate 20. It has a heat dissipation function that transmits heat to the layer) with good thermal conductivity.

  Among these, the through-hole 301 connects the first circuit pattern 110a in the first conductor layer 11 and the fourth circuit pattern 140a in the fourth conductor layer 14, and there is no unnecessary portion. It has the same structure as the conventional through hole 301 shown in FIG.

  However, the through hole 302 shown in FIGS. 1 and 2 connects the first circuit pattern 110b of the first conductor layer 11 and the second circuit pattern 120 (ground line) of the second conductor layer 12. The subsequent portion, that is, the portion extending from the second conductor layer 12 to the fourth conductor layer 14 is an unnecessary portion. This unnecessary portion is indicated by a dotted line A in FIG.

  As described above, since the signal flowing through the first circuit pattern 110b is also transmitted to this unnecessary portion A, this portion functions as an antenna that emits noise that causes electromagnetic interference (EMI) in the configuration of FIG. There are things to do.

  Therefore, in the configuration of the present embodiment, as shown in FIG. 1, the terminal portion of the unnecessary portion, that is, the portion reaching the fourth conductor layer 14 is connected to the second through the substrate embedded resistor 311 that functions as a terminal resistor. The conductor layer 12 is terminated by connecting to the second circuit pattern 120 (ground line).

  More specifically, in order to connect the second circuit pattern 120 (ground line) in the second conductor layer 12 to the fourth conductor layer 14, a small interlayer in the thickness direction between these and the insulating layer 15 therebetween. A connection hole is formed, and a substrate embedding resistor 311 filled with a metal having a predetermined resistance value is provided in the small interlayer connection hole. An end portion of the substrate embedding resistor 311 reaching the fourth conductor layer 14 and an end portion of the through hole 302 reaching the fourth conductor layer 14 are connected by the connection pattern 141. Then, the substrate embedding resistor 311 functions as a termination resistor by setting the resistance value of the substrate embedding resistor 311 to an appropriate value that matches the characteristic impedance so that signal reflection is suppressed. Therefore, a signal transmitted to the unnecessary portion of the through hole 302 flows to the second circuit pattern 120 (ground line) without being radiated as an electromagnetic wave (at least the radiated electromagnetic wave is suppressed). Thus, since electromagnetic interference (EMI) can be reduced, generation | occurrence | production of an unnecessary noise can be suppressed. In addition, when a noise is generated, a metal case for noise shielding is often used as a case for storing the multilayer circuit board. Cost can be reduced.

  In the above description, noise radiated as an electromagnetic wave has been described as an example. However, the present invention is not limited to this, and noise generated by an unnecessary portion of a through hole is typically conducted noise (due to a reflected wave). However, it can be similarly suppressed.

  Similarly to the through hole 302, the through hole 303 has an unnecessary portion. That is, the through hole 303 includes a third circuit pattern 130 (power supply line) in the third conductor layer 13 and a fourth circuit pattern 140b in the fourth conductor layer 14 as shown in FIGS. Subsequent portions, that is, portions extending from the first conductor layer 11 to the third conductor layer 13 are unnecessary portions. This unnecessary portion is indicated by a dotted line B in FIG.

  As described above, since the signal flowing through the fourth circuit pattern 140b is also transmitted to the unnecessary portion B, this portion functions as an antenna that emits noise that causes electromagnetic interference (EMI) in the configuration of FIG. There are things to do.

  Therefore, in the configuration of the present embodiment, as shown in FIG. 1, the adjustment pattern 111 is provided at the end portion of the unnecessary portion, that is, the portion reaching the first conductor layer 11, and this end portion is embedded in the adjustment pattern 111 and the substrate. Termination is achieved by connecting to the second circuit pattern 120 (ground line) in the second conductor layer 12 via the resistor 312.

  The substrate embedding resistor 312 has substantially the same configuration as the substrate embedding resistor 311 except that an adjustment pattern 111 is newly provided. The adjustment pattern 111 is wired with a conductor used in the circuit pattern so as to have a predetermined resistance value. Further, the adjustment pattern 111 and a substrate embedded resistor 312 having an appropriate resistance value are arranged. One end of the conductor layer 11 is connected. Then, if the resistance value of the adjustment pattern 111 and the resistance value of the substrate embedding resistor 312 are set to appropriate values that match the characteristic impedance so that signal reflection is suppressed, the adjustment pattern 111 and the substrate embedding resistor 312 can be obtained. Functions as a termination resistor. Therefore, generation of noise can be suppressed as in the case of the through hole 302. Further, even when the sufficient resistance value cannot be set only by the substrate embedding resistor 312 because the length of the substrate embedding resistor 312 is not sufficient, the resistor formed by the adjustment pattern 111 is connected in series. Thus, it is possible to set an appropriate value for characteristic impedance matching. The adjustment pattern 111 does not necessarily have to be routed and may have an appropriate length and width so that an appropriate resistance value can be obtained.

  If the resistance value of the substrate embedding resistor 312 is too large, the substrate embedding resistor 312 is configured by a general conductor, and the resistance value of the adjustment pattern 111 is set to an appropriate value for characteristic impedance matching. Also good. Furthermore, instead of or together with the adjustment pattern 111, a printing resistance using a material such as carbon (typically a very thin resistance formed by a well-known method by performing ink jet printing or offset printing). The structure used may be sufficient. Thus, if at least one of the substrate embedding resistors 311 and 312, the adjustment pattern 111, and the printing resistor is used, the termination resistor can be formed inexpensively and in a small size.

  The through holes 302 and 303 do not necessarily have to be connected to the second circuit pattern 120 (ground line) via the substrate embedding resistors 311 and 312 and the like. For example, the third circuit pattern 130 (power supply) Line) or other constant potential circuit patterns or other conductors. The through holes 302 and 303 connect the first conductor layer 11 and the fourth conductor layer 14, but this is merely an example, and the conductors among the through holes connecting two or more different conductor layers are conductors. Any termination resistor may be connected to a through hole having an end portion that is not connected to any of the circuit patterns included in the layer. Further, the connection relationship between the through holes 302 and 303, the board embedding resistors 311 and 312 and the adjustment pattern 111 is merely an example, and two ends of a certain through hole are provided in a multilayer circuit board having a multilayer structure different from the multilayer circuit board. A configuration in which each is terminated with two termination resistors, or a configuration in which a substrate embedding resistor, an adjustment pattern, or the like is shared in order to terminate a plurality of through holes may be employed.

  Here, the multilayer circuit board according to the present embodiment is typically used for a power circuit board for controlling large electric power, such as a motor drive circuit board for an electric power steering apparatus, a motor control circuit board, and the like. Normally, an ECU (electronic control unit) for an electric power steering apparatus includes a motor control circuit that calculates the amount of drive current supplied to the steering assist motor, and a motor drive that drives the steering assist motor by controlling a large current. And a power circuit such as a circuit. By using the multilayer circuit board for these boards, it is possible to suppress the occurrence of the noise described above.

1 is a perspective view including a cross section of a multilayer circuit board according to an embodiment of the present invention. It is a perspective view including the cross section of the conventional multilayer circuit board.

Explanation of symbols

  11-14: First to fourth conductor layers, 15: Insulating layer, 20: Metal substrate, 110a, 110b: First circuit pattern, 111: Adjustment pattern, 120: Second circuit pattern (ground line), 130 ... third circuit pattern (power supply line), 140a, 140b ... fourth circuit pattern, 141 ... connection pattern, 301-303 ... through hole, 311,312 ... substrate embedded resistor, A, B ... no need for through hole portion

Claims (2)

A laminated circuit portion formed by alternately laminating conductor layers and insulating layers;
A through hole connecting two or more different conductor layers;
One end is connected to the end portion of the through hole having an end portion that is not connected to any of the circuit patterns included in the conductor layer, and the power supply line included in the conductor layer is any of the circuit patterns. A termination resistor connected at the other end to the ground wire ,
The termination resistor, so as to pass through at least one of said insulating layer, characterized Rukoto such a buried resistor is formed in the stacking direction, a multilayer circuit board. The one end of the termination resistor is connected to the end of the through hole by one of the inner conductor layers provided with the insulating layer on both sides,
Wherein the other end of the termination resistor by a different one of said internal conductor layer, and wherein the Rukoto connected to the power supply line or the ground line, multi-layer circuit board according to claim 1.

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