Circuit board

Abstract

To provide a circuit board capable of reducing radiation noise.SOLUTION: A DC-DC converter circuit board 10 includes a power supply control IC 20 mounted on the DC-DC converter circuit board 10 and supplying power, a substrate, and a conductive pattern L formed on the substrate. The conductive pattern L includes an input line Li for inputting power to the power supply control IC 20 and an output line Lo for outputting power from the power supply control IC 20. The DC-DC converter circuit board 10 includes an additional conductive conductor portion 30 provided on the conductive pattern L at the end of the input line Li or the output line Lo on the power supply control IC 20 side.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to circuit boards. [Background technology]

[0002] The vehicle control device described in Patent Document 1 is electrically connected to an on-board battery and a microcomputer, and has a power supply including a step-down DC-DC converter that converts the battery voltage, for example, 12.5 V, to 5 V (see paragraph 0019 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-160640 Summary of the Invention [Problem to be solved by the invention]

[0004] In the step-down DC-DC converter described in Patent Document 1, the wiring width between terminals tends to become narrower in recent years due to the miniaturization of IC chips, which increases the wiring impedance and may ultimately increase radiation noise.

[0005] The present disclosure has been made in consideration of the above-described circumstances, and aims to provide a circuit board capable of reducing radiation noise. [Means for solving the problem]

[0006] In order to achieve the above object, the circuit board according to the present disclosure comprises: a power supply control element mounted on the circuit board and supplying power; A substrate; a conductive pattern formed on the substrate, The conductive pattern is an input line for inputting power to the power supply control element; an output line for outputting power from the power supply control element; The circuit board includes an additional conductive conductor portion provided on the conductive pattern at an end of the input line or the output line on the power supply control element side. [Effects of the Invention]

[0007] According to the present disclosure, radiation noise can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a circuit diagram of a DC-DC converter circuit board according to a first embodiment of the present disclosure. FIG. [Figure 2] 1 is a plan view of a portion of a mounting surface of a DC-DC converter circuit board according to a first embodiment of the present disclosure. FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view taken along the line III-III in FIG. 2. [Figure 4] FIG. 10 is a plan view of a portion of a mounting surface of a DC-DC converter circuit board according to a second embodiment of the present disclosure. [Figure 5] FIG. 10 is a plan view of a portion of a mounting surface of a DC-DC converter circuit board according to a modified example of the present disclosure. [Figure 6] 10 is a schematic cross-sectional view of a line detail and an additional conductor portion according to a modified example of the present disclosure. [Figure 7] 10 is a schematic cross-sectional view of a line detail and an additional conductor portion according to a modified example of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) A DC-DC converter circuit board, which is an example of a circuit board according to a first embodiment of the present disclosure, will be described with reference to FIGS. 1 to 3. FIG.

[0010] The DC-DC converter circuit board 10 is a voltage drop circuit that drops the voltage input from the power supply 6 and outputs the dropped voltage to a load 7. The load 7 is a vehicle display device that receives the voltage from the DC-DC converter circuit board 10 and displays vehicle information. This vehicle display device is, for example, a type that includes a liquid crystal display panel and a backlight, neither of which are shown. Note that this vehicle display device is not limited to this type and may be of any type, for example, a type equipped with an organic electroluminescence display (OLED) or a type equipped with a digital mirror device (DMD).

[0011] (Circuit configuration) First, the circuit configuration of the DC-DC converter circuit board 10 will be described with reference to FIG. The DC-DC converter circuit board 10 includes a power supply control IC (Integrated Circuit) 20, an inductor 4, capacitors 1 and 5, an input line Li, an output line Lo, a ground line (ground pattern) Lg, a power supply terminal Pv, and a ground terminal Pg.

[0012] The power supply control IC 20 includes a switching element 2, a diode 3, an input terminal 20i, an output terminal 20o, and a ground terminal 20g. The power supply terminal Pv is electrically connected to the anode terminal of the power supply 6 , and the ground terminal Pg is electrically connected to the cathode terminal of the power supply 6 .

[0013] A first end of the input line Li is electrically connected to the power supply terminal Pv, and a second end of the input line Li is electrically connected to the input terminal 20i of the power supply control IC 20. A first end of the output line Lo is electrically connected to the output terminal 20 o of the power supply control IC 20 , and a second end of the output line Lo is electrically connected to the anode terminal of the load 7 . The inductor 4 is provided on the output line Lo.

[0014] A first end of the switching element 2 is electrically connected to the input terminal 20i, and a second end of the switching element 2 is electrically connected to the output terminal 20o. The switching element 2 is configured by a transistor (not shown). The switching element 2 is controlled to be turned on and off by a switch control unit (not shown).

[0015] The cathode terminal of the diode 3 is electrically connected to an electrical line L1 in the power supply control IC 20 between the switching element 2 and the output terminal 20o. The electrical line L1 is connected between the input terminal 20i and the output terminal 20o. The anode terminal of the diode 3 is electrically connected to an electrical line L2 in the power supply control IC 20 that is conductive to the ground line Lg. The electrical line L2 is connected between a terminal connected to the anode line of the load 7 and the ground terminal 20g. The diode 3 prevents the current accumulated in the inductor 4 from flowing to the ground line Lg when the switching element 2 is turned off.

[0016] A first end of the capacitor 1 is electrically connected to the input line Li, and a second end of the capacitor 1 is electrically connected to the ground line Lg. The capacitor 5 is connected in parallel with the load 7 . Capacitors 1 and 5 are provided to remove noise and smooth the voltage waveform.

[0017] The operation of the DC-DC converter circuit board 10 will be described. The switching element 2 is periodically switched between on and off by a switch control unit (not shown). When the switching element 2 is turned on, power is supplied from the power supply 6 to the load 7 via the output terminal 20o of the power supply control IC 20, and energy is stored in the inductor 4. When the switching element 2 is turned off, power supply from the output terminal 20o of the power supply control IC 20 stops, but power is supplied to the load 7 based on the energy stored in the inductor 4. In this way, the DC-DC converter circuit board 10 supplies a voltage lower than the power supply voltage from the power supply 6 to the load 7 by the switching element 2 repeatedly turning on and off.

[0018] (physical configuration) Next, the physical configuration of the DC-DC converter circuit board 10 will be described with reference to FIGS. The DC-DC converter circuit board 10 includes a substrate 40, a conductive pattern L, a plurality of additional conductor portions 30, a power supply control IC 20, an inductor 4, and a plurality of capacitors 1 and 5.

[0019] The substrate 40 has a rectangular plate shape, and has mounted thereon the components of the DC-DC converter circuit board 10 (the power supply control IC 20, the inductor 4, and the capacitors 1 and 5). The substrate 40 is formed, for example, from FR-4 (Flame Retardant Type 4), which is a glass woven fabric made by weaving glass fibers into a cloth-like material and impregnating it with epoxy resin. A conductive pattern L is formed on the mounting surface 41 of the substrate 40 as a wiring pattern. The conductive pattern L forms the above-mentioned input line Li, output line Lo, and ground line Lg (solid ground). On a mounting surface 41 of the substrate 40, a power supply control IC 20, an inductor 4, and capacitors 1 and 5 are mounted.

[0020] As shown in FIG. 3, the conductive pattern L includes a copper foil pattern LC and a copper plating layer LP. The copper foil pattern LC is laminated on the mounting surface 41 of the substrate 40 . The copper plating layer LP is laminated on the copper foil pattern LC. The copper plating layer LP is formed at the same time as forming copper plating on the inner circumferential surface of a through-hole via (not shown) in the base material 40 after drilling the hole.

[0021] As shown in FIG. 2, the power supply control IC 20 includes a main body package 21, a plurality of input terminals 20i, a plurality of output terminals 20o, and a ground terminal 20g. The main package 21 is shaped like a rectangular chip. The inside of the main package 21 is made of resin, which encapsulates an IC chip including the switching element 2 and the diode 3. The terminals 20i, 20o, and 20g are formed as lead frames and are exposed from a first side surface 21a and a second side surface 21b of the main package 21.

[0022] A plurality of (four in this example) input terminals 20i are arranged along the longitudinal direction of a first side surface 21a of the four side surfaces around the main package 21. Multiple (three in this example) output terminals 20o are arranged along the longitudinal direction of second side surface 21b, one of the four side surfaces around main package 21. One ground terminal 20g is arranged on second side surface 21b, sandwiched between two output terminals 20o. First side surface 21a and second side surface 21b are positioned facing each other and parallel to each other.

[0023] Each input terminal 20i is electrically connected to a respective line segment La of an input line Li, each output terminal 20o is electrically connected to a respective line segment La of an output line Lo, and each ground terminal 20g is electrically connected to a line segment La of a ground line Lg. Each of the partial line sections La has a narrow, generally rectangular shape extending toward the terminals 20i, 20o, and 20g of the power supply control IC 20. Each of the partial line sections La is a portion located at the end of each of the lines Li, Lo, and Lg on the power supply control IC 20 side.

[0024] The multiple additional conductor portions 30 are formed from a conductive material and, when stacked on the line section La, effectively increase the volume of the line section La, thereby functioning to reduce the wiring impedance component that impedes the flow of electricity. The additional conductor portions 30 are formed from solder. The additional conductor 30 has a rectangular parallelepiped shape. The thickness Th of the additional conductor 30 is set to 100 μm to 150 μm. The additional conductor 30 is formed by soldering using a metal mask. The thickness Th of the additional conductor 30 is thicker than the thickness of the thin line portion La, and is set to, for example, three to five times the thickness of the thin line portion La. The thickness of the thin line portion La is 35 μm to 40 μm, for example, approximately 38 μm. The width W of the additional conductor portion 30 is set to be the same as or smaller than the width of the thin line portion La.

[0025] In this example, one line segment La of an input line Li that is electrically connected to one input terminal 20i is provided with additional conductor portions 30a and 30b as two additional conductor portions 30. This line segment La connects one of the capacitors 1 to the ground pattern Lg, and is formed so that two linear portions intersect at an obtuse angle. Each of the additional conductor portions 30a and 30b is formed on each linear portion of this line segment La. In this example, additional conductor portions 30a, 30b are provided in the line section La that is conductive to the input terminal 20i located at the end of the multiple input terminals 20i, but additional conductor portions 30 may also be provided in the line section La that is conductive to other input terminals 20i. The number of additional conductor portions provided on one line section La is not limited to two, but may be one, or three or more.

[0026] Furthermore, an additional conductor portion 30c is provided in one line portion La of the output line Lo that is conductive to one output terminal 20o as one additional conductor portion 30. This one output terminal 20o is located between the ground terminal 20g and another output terminal 20o. An additional conductor portion may be provided in the line section La that is electrically connected to another output terminal 20o, and the number of additional conductor portions provided on one line section La can be changed appropriately in the same manner as above.

[0027] (effect) According to the first embodiment described above, the following effects are achieved. (1) The DC-DC converter circuit board 10 includes a power supply control IC 20, which is an example of a power supply control element mounted on the DC-DC converter circuit board 10 and supplies power, a substrate 40, and a conductive pattern L formed on the substrate 40. The conductive pattern L includes an input line Li for inputting power to the power supply control IC 20 and an output line Lo for outputting power from the power supply control IC 20. The DC-DC converter circuit board 10 includes an additional conductive conductor portion 30 provided on the conductive pattern L at the end of the input line Li or the output line Lo on the power supply control IC 20 side. According to this configuration, the wiring impedance component can be reduced by the additional conductor portion 30. This reduces harmonic noise in the current loop waveform, and can reduce radiation noise.

[0028] (2) The additional conductor portion 30 is made of solder. According to this configuration, it is possible to form the additional conductor 30 in the soldering process, and therefore the additional conductor 30 can be formed easily.

[0029] (3) The additional conductor portion 30 is formed of solder into a rectangular parallelepiped shape. According to this configuration, the additional conductor 30 can be easily formed using a metal mask. Furthermore, by using a metal mask, the thickness of the additional conductor 30 can be increased, which makes it easier to reduce the wiring impedance component.

[0030] (Second embodiment) A DC-DC converter circuit board, which is an example of a circuit board according to a second embodiment of the present disclosure, will be described with reference to FIG. In this embodiment, the DC-DC converter circuit board 10A is different from the first embodiment in that it is a multi-power step-down circuit that outputs a plurality of different voltages (3 V and 5 V). The following mainly describes the differences from the first embodiment.

[0031] 4, a plurality of input terminals 120i, a plurality of output terminals 120o, and a ground terminal 120g are provided on one side surface 122 of a main package 121 of the power supply control IC 120. Of the terminals 120i, 120o, and 120g arranged in a row, the two input terminals 120i are arranged on the outermost sides, the ground terminal 120g is arranged in the center, and the two output terminals 120o are each arranged between the ground terminal 120g and the input terminal 120i.

[0032] Additional conductor portions 30d and 30e are provided on the line portion La of each input line Li that is connected to each input terminal 120i. An additional conductor portion 30f is provided on the line detail La of the ground line Lg that is electrically connected to the ground terminal 120g. Voltages (for example, 1.5V and 5V) corresponding to different loads are supplied from the output lines Lo that are connected to the output terminals 120o.

[0033] (effect) According to the second embodiment described above, the following effects are achieved. When the DC-DC converter circuit board 10A is a multiple-power step-down circuit, the density of the terminals 120i, 120o, 120 and the lines Li, Lo, Lg of the power supply control IC 120 increases, which tends to narrow the line width and spacing of the lines Li, Lo, Lg. For this reason, applying the additional conductor portions 30d, 30e, 30f to a multiple-power step-down circuit is particularly beneficial from the viewpoint of reducing radiation noise.

[0034] The present disclosure is not limited to the above-described embodiments and drawings. Modifications (including deletion of components) may be made as appropriate within the scope of the present disclosure. An example of such a modification is described below.

[0035] (Variation) In each of the above embodiments, the additional conductor portions 30, 30a to 30f were provided on the line segment La, but this is not limited to this and they may be provided other than on the line segment La as long as they are on the end of the input terminal 20i, 120i or the output terminal 20o, 120o on the power supply control IC 20, 120 side. 5, the input line Li includes two line segment portions La and a main body portion Lb from which the two line segment portions La extend. The additional conductor portion 30h is formed on the main body portion Lb in an area adjacent to the two line segment portions La. The two line segment portions La are electrically connected to two adjacent input terminals 20i. Furthermore, the present invention is not limited to the example of FIG. 5, and may have a configuration in which one line detail La extends from the main body Lb. In this way, the lines Li, Lo, and Lg may be provided at positions other than the detailed line portion La as long as they are around the detailed line portion La.

[0036] In each of the above embodiments, the additional conductor 30 is formed as a rectangular parallelepiped with a thickness Th of 100 μm to 150 μm, but this is not limiting, and the additional conductor 130 may be formed as a thin plate with a thickness Th of 2 μm to 20 μm, as shown in Fig. 6. In this case, the additional conductor 130 may be formed by a solder leveler. Furthermore, as shown in FIG. 7, the additional conductor portion 230 may have a semi-cylindrical or semi-spherical shape with its bottom surface in contact with the upper surface of the line segment La. The additional conductors 30, 130, and 230 may be made of a metal material other than solder.

[0037] In the above embodiments, the DC-DC converter circuit boards 10 and 10A are step-down circuits, but they may also be step-up circuits. When the DC-DC converter circuit boards 10 and 10A are configured as step-up circuits, a switching element 2 is provided in the position of the diode 3, a diode 3 is provided in the position of the inductor 4, and an inductor 4 is provided in the position of the switching element 2 in FIG.

[0038] In each of the above embodiments, the additional conductor portions 30, 130, 230 may be provided on all the line-segment portions La or in the vicinity of the line-segment portions La. In each of the above embodiments, the DC-DC converter circuit boards 10 and 10A may be a driver that drives a light source or a motor as a load. That is, the load is not limited to a display device, and may be a driver that drives a light source or a motor. In each of the above embodiments, the power supply control ICs 20 and 120 incorporate the switching element 2 and the diode 3, but the diode 3 may not be incorporated and may be mounted outside the power supply control ICs 20 and 120. [Explanation of symbols]

[0039] 1,5...capacitor, 2...switching element, 3...diode, 4...inductor, 6...power supply, 7...load, 10,10A...DCDC converter circuit board, 20,120...power supply control IC, 20i,120i...input terminal, 20o,120o...output terminal, 21,121...main body package, 21a...first side, 21b...second side, 30,30a to 30f,30h,130,230...additional conductor portion, 40...substrate, 41...mounting surface, 122...side, L...conductive pattern, L1,L2...electrical line, LC...copper foil pattern, LP...copper plating layer, La...line detail, Lb...main body, Li...input line, Lo...output line, Lg...ground line, ground pattern, Pg,20g,120g...ground terminal, Pv...power supply terminal

Claims

1. A circuit board, a power supply control element mounted on the circuit board and supplying power; A substrate; a conductive pattern formed on the substrate, The conductive pattern is an input line for inputting power to the power supply control element; an output line for outputting power from the power supply control element; the circuit board includes an additional conductor portion that is provided on the conductive pattern at an end of the input line or the output line on the power supply control element side and has electrical conductivity; Circuit board.

2. The additional conductor portion is formed of solder. The circuit board according to claim 1 .

3. The additional conductor portion is formed of solder in a rectangular parallelepiped or thin plate shape. The circuit board according to claim 1 .

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