Electronic device

Abstract

To suppress cracking of solder resist 32 which is apt to occur to a part where an outer edge 310a of a land exposure part 310 is close to an opening edge 11a of a through hole 11.SOLUTION: Solder resist 32 is formed over a peripheral edge part of a land part 31 except a land exposure part 310 at a circumference of a through hole 11 to be an over-resist region 320. The land exposure part 310 is formed elliptically for workability of a laser soldering process. An outer edge 31a of the land part 31 is in a small elliptic shape smaller in ellipticity than an ellipse of the outer edge 310a of the land exposure part 310, and both are not similar to each other. The width dimension L of the over-resist region 320 is relatively large at a part where the outer edge 310a of the land exposure part 310 is along the minor axis of an ellipse close to the opening edge 11a of the through hole 11, and cracking is thereby suppressed.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This invention relates to an improvement of an electronic device including a circuit board on which a plurality of electronic components are mounted, and a terminal passing through a through-hole of the circuit board is soldered to an annular land portion surrounding the through-hole.

Background Art

[0002] In circuit boards of various electronic devices, a terminal passing through a through-hole of the circuit board may be soldered to an annular land portion surrounding the through-hole. In such a case, there is a concern that the land portion may be peeled off or lifted from the substrate surface due to heating during soldering.

[0003] Patent Document 1 discloses that, in order to suppress such peeling or lifting of the land portion, a solder resist is provided so as to overlap the periphery of the land portion with a certain width (for example, a width of 0.15 mm). That is, in Patent Document 1, a so-called over-resist region where the solder resist overlaps the land portion is formed with a certain width over the entire circumference of the land portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a configuration having an over-resist region where the solder resist overlaps the land portion as described above, stress is generated in the substrate around the through-hole when the terminal is soldered, so that cracks may occur in the solder resist of the over-resist region. In particular, cracks are more likely to occur as the outer edge of the land portion, which is the interface between the land portion made of metal and the solder resist material, is closer to the opening edge of the through-hole.

Means for Solving the Problems

[0006] In one aspect of the present invention, there is provided an electronic device including a circuit board on which a plurality of electronic components are mounted and a solder resist is provided on the surface, and terminals passing through through-holes of the circuit board are soldered to an annular land portion surrounding the through-holes. The land portion has an over-resist region where the solder resist is overlapped including at least the peripheral portion of the land portion, and a land exposed portion located closer to the through-hole side than the over-resist region and where the land surface around the through-hole is exposed. The outer edge shape of the land exposed portion is formed so as not to be similar to the outer edge shape of the land portion by the over-resist region. For example, a part of the circumferential direction of the land exposed portion becomes a heat-receiving position in the soldering process, the width dimension of the over-resist region is small in the direction of the heat-receiving position, and the width dimension of the over-resist region is relatively large in other directions. For example, the land exposed portion expands radially outward at one location in the circumferential direction that becomes the heat-receiving position in the soldering process, compared with the width dimension of the over-resist region at that location, the width dimension of the over-resist region at the circumferential position on the opposite side across the through hole from that location is relatively large. In another aspect of the present invention, there is provided an electronic device including a circuit board on which a plurality of electronic components are mounted, and terminals passing through through holes of the circuit board are soldered to an annular land portion surrounding the through holes, a solder resist provided on the surface of the circuit board is formed to overlap the peripheral edge of the land portion leaving the land exposed portion around the through hole, the outer edge of the land exposed portion forms an ellipse with a relatively large flatness ratio, the outer edge of the land portion forms an ellipse or a perfect circle with a relatively small flatness ratio.

Advantages of the Invention

[0007] According to this invention, while arbitrarily ensuring the shape of the land exposed portion that is actually soldered, the outer edge of the land portion is separated from the opening edge of the through-hole, and the occurrence of cracks in the solder resist in the over-resist region can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0010] First, the overall configuration of an electronic device according to an embodiment of the present invention will be briefly described. In one embodiment, the present invention is applied to an electric actuator device 101 of an electric power steering device of an automobile shown in FIG. 1. Note that since the basic configuration of this electric actuator device 101 is disclosed in, for example, Japanese Patent Application Laid-Open No. 2020-148639, only the minimum necessary explanation will be given here.

[0011] FIG. 1 is an exploded perspective view of an electric actuator device 101 that provides a steering assist force to a steering mechanism (not shown) in an electric power steering device. This electric actuator device 101 includes a cylindrical motor unit 1, an inverter power module 2, a circuit board 3 formed of a multilayer circuit board bent in a substantially U shape, a connector member 4 in which a plurality of connectors are integrally assembled, and a motor cover 5 attached to one end of the motor unit 1 so as to cover the inverter power module 2, the circuit board 3, and the connector member 4.

[0012] The motor unit 1 houses a three-phase AC motor inside a cylindrical housing 7, and has a connecting portion 6a such as a gear or a spline at the tip of a rotating shaft 6 protruding from the tip surface of the housing 7. It is connected to the steering mechanism via this connecting portion 6a. The motor is a three-phase permanent magnet brushless motor, the stator is provided with three-phase coils, and permanent magnets are arranged on the outer peripheral surface of the rotor. In addition, the motor is provided with two systems of coils and corresponding permanent magnets in order to provide redundancy.

[0013] One end of the housing 7 on the side opposite to the connecting portion 6a is configured as a bottom wall portion 7a having a horseshoe-shaped contour in which a part of the outer peripheral edge extends in the radial direction. A motor cover 5 having a horseshoe-shaped contour corresponding to the bottom wall portion 7a is attached so as to cover the bottom wall portion 7a. An inverter power module 2, a circuit board 3, and a connector member 4 are accommodated in an overlapping manner in the axial direction of the rotating shaft 6 in a space formed between the bottom wall portion 7a and the motor cover 5. Here, both ends of each coil of the motor penetrate the bottom wall portion 7a as coil terminal portions 9 and project toward the motor cover 5 side, and are connected to corresponding terminals of the inverter power module 2 by TIG welding or the like.

[0014] The inverter power module 2 includes two inverter modules 2A that drive the motor and a relay module 2B that serves as a neutral point relay for the coils. These three are arranged so as to form a substantially U shape surrounding the rotating shaft 6. The inverter modules 2A and the relay module 2B are fixed to the end face of the motor unit 1 via a pressing member 2C. Further, the inverter modules 2A and the relay module 2B are provided with a plurality of pin-shaped motor drive terminals 10. The motor drive terminals 10 extend toward the circuit board 3 along the axial direction of the rotating shaft 6, and as will be described later, after passing through the through holes 11 of the circuit board 3, they are conductively connected to the wiring of the circuit board 3 by laser soldering.

[0015] The connector member 4 includes three connectors that point in the same direction along the axial direction of the rotating shaft 6. Specifically, a power supply connector 4a located at the center, a sensor input connector 4b to which signals from sensors (for example, a steering angle sensor and a torque sensor) arranged on the steering mechanism side are input, and a communication connector 4c for performing communication (for example, CAN communication) with other control devices in the vehicle are provided. These connectors 4a, 4b, and 4c project to the outside through the opening 8 of the motor cover 5.

[0016] The circuit board 3 is composed of a multilayer printed wiring board, for example, a so-called 8-layer printed wiring board having 8 metal foil layers (for example, copper foil layers). This multilayer printed wiring board is formed by laminating several base materials made of, for example, glass epoxy, which have metal foil layers on one or both sides, via a prepreg (adhesive layer), and then integrating them by heating and pressing. Then, a desired circuit pattern is formed by etching each metal foil layer and forming vias extending in the lamination direction.

[0017] The circuit board 3 is disposed between the bottom wall portion 7a of the housing 7 and the connector member 4 in a shape bent in a substantially U shape. FIG. 2 shows the circuit board 3 in a developed state. The circuit board 3 includes a first rigid portion 21 that is a power system board on which an electronic component group through which a relatively large current flows for driving the motor via the inverter power module 2 is mounted, a second rigid portion 22 that is a control system board on which control system electronic components through which a relatively small current flows are mounted, and a flexible portion 23 in which the number of base material layers between the two is reduced. And the circuit board 3 is accommodated between the housing 7 serving as a housing and the motor cover 5 in a state where the flexible portion 23 is bent and deformed so that the first rigid portion 21 and the second rigid portion 22 overlap each other in the axial direction of the rotation shaft 6. The first rigid portion 21 and the second rigid portion 22 in the bent state are separated from each other by a distance such that the electronic components mounted on each do not contact each other, and are supported in a state of being parallel to each other while maintaining a planar state.

[0018] As shown in Fig. 2, a large number of electronic components 24 arranged on the circuit board 3 are surface-mounted by reflow soldering mainly on the first surface 3A of the circuit board 3 which is mainly in a bent state and faces inward. That is, land portions for connecting each electronic component 24 are formed on the metal foil layer on the surface layer of the circuit board 3 made of a multilayer printed circuit board. After applying a solder resist described later, cream solder is printed on these land portions by a printing technique using masking. Then, after mounting each electronic component 24 at a predetermined position, the circuit board 3 is heated in a furnace to melt the solder, thereby performing soldering. Note that some of the electronic components are mounted on the second surface on the opposite side of the first surface 3A, and these are also reflow soldered at the same time.

[0019] In the first rigid portion 21 of the circuit board 3, circular through holes 11 through which the pin-shaped motor drive terminals 10 extending from the above-described inverter power module 2 penetrate are formed, and annular land portions 31 are provided around each through hole 11. The motor drive terminals 10 are individually laser soldered to the land portions 31 instead of reflow soldering. In the laser soldering process, the tip of the wire-shaped solder material fed onto the land portion 31 is heated and melted by irradiation with laser light to form a fillet covering the terminal 10 and the land portion 31.

[0020] Next, with reference to FIGS. 3 and 4, the configuration of the land portion 31, which is the main part of the present invention, will be described. FIGS. 3 and 4 show the land portion 31 of the first embodiment. The land portion 31 is formed by etching the metal foil layer on the surface layer of the multilayer circuit board. On the metal foil layer of the circuit board 3, a solder resist 32 serving as an insulating film is further provided to prevent solder from adhering to unnecessary portions and to protect the circuit pattern. The solder resist 32 is made of so-called solder resist ink and is applied substantially over the entire surface of the circuit board 3, leaving the land portions such as the land portion 31 that require soldering and the outer peripheral edge of the circuit board 3, using a printing technique such as screen printing. That is, the solder resist 32 is laminated in layers on the etched metal foil layer, and the base material surface and the circuit pattern (circuit wiring) of the circuit board 3 are covered by the solder resist 32.

[0021] Here, at the peripheral portion of the annular land portion 31 surrounding the through hole 11, the solder resist 32 is provided so as to overlap the land portion 31 in order to suppress peeling or lifting of the land portion 31. In the present invention, the range of the solder resist 32 overlapping the land portion 31 is called the over-resist region 320, and the central portion of the land portion 31 that is exposed (however, finally covered with a solder fillet) without being covered by the solder resist 32 is called the land exposed portion 310. The outer edge 310a of the land exposed portion 310 is also the inner edge of the over-resist region 320 at the same time. The outer edge of the land portion 31 is indicated by a broken line with the symbol 31a. The outer edge 31a of the land portion 31 indicated by this broken line is covered by the solder resist 32.

[0022] The land exposed portion 310 is dimensioned corresponding to the desired solder fillet size formed by laser soldering. In particular, it has an elliptical shape centered on the through hole 11 in consideration of the workability in the laser soldering process. In the laser soldering process, laser light is irradiated along the major axis direction of the ellipse toward the heat-receiving position indicated by the circle labeled 33 in FIG. 4, and the tip of the wire-shaped solder material is also fed out near the heat-receiving position 33 so as to receive this laser light. The heat-receiving position 33 is set near the position where the major axis of the ellipse intersects the opening edge of the through hole 11, as shown in FIG. 4. The land exposed portion 310 is formed in an elliptical shape to ensure the supply of the solder material to the land exposed portion 310 even in the presence of product errors or equipment errors in the laser soldering process. In the present invention, the "elliptical shape" does not refer only to the narrow sense of the ellipse based on the strict mathematical definition, but means a broad sense of the ellipse widely including so-called oval shapes, rugby ball shapes, etc. The illustrated example rather forms a shape (often called an oval shape) included in the broad sense of the ellipse in which a pair of semi-circles are connected by two parallel straight lines, rather than the narrow sense of the ellipse in mathematics.

[0023] The land portion 31 has an elliptical shape in which the major axis and the minor axis directions coincide with those of the land exposed portion 310 and which is larger than the land exposed portion 310. Therefore, an over-resist region 320 that is continuously annular over the entire circumference exists between the outer edge 31a of the land portion 31 and the outer edge 310a of the land exposed portion 310. Here, the outer edge 310a of the land exposed portion 310 forms an ellipse with a relatively large flatness ratio, and the outer edge 31a of the land portion 31 forms an ellipse with a relatively small flatness ratio. The flatness ratio is defined as "(major axis - minor axis) / major axis" and becomes 0 for a perfect circle. In the illustrated example, the outer edge 31a of the land portion 31 forms a broad sense of the ellipse in which a pair of semi-circles are connected by two parallel straight lines. Thus, the outer edge 31a of the land portion 31 and the outer edge 310a of the land exposed portion 310 are not similar shapes to each other. Therefore, the width dimension L of the annularly extending over-resist region 320 is not constant. In the present invention, the "width dimension L" of the over-resist region 320 refers to the dimension measured in the direction perpendicular to the tangent at each part of the outer edge 310a of the land exposed portion 310.

[0024] In the first embodiment, the width dimension L of the over-resist region 320 is minimized at the portion along the major axis of the ellipse of the land exposure portion 310 and maximized at the portion along the minor axis.

[0025] FIG. 4 is an explanatory diagram showing the dimensional relationship of each part in the first embodiment. The minimum width dimension L of the over-resist region 320 along the major axis of the ellipse of the land exposure portion 310 is shown as L1, and the maximum width dimension L of the over-resist region 320 along the minor axis is shown as L2. At the portion where the outer edge 31a of the land portion 31 forms a straight line, the width dimension L is constant (maximum L2). At the portion where the outer edge 31a of the land portion 31 forms an arc, the width dimension L gradually changes.

[0026] Compared with the radius of curvature R1 of the arc portion of the outer edge 31a of the land portion 31, the radius of curvature R2 of the arc portion of the outer edge 310a of the land exposure portion 310 is relatively small. Therefore, the width dimension L increases as it approaches both ends (connection portions with the straight portions) of the semi-circle from the portion along the major axis of the ellipse at the center of the semi-circle.

[0027] On the other hand, focusing on the distance D (radial distance measured radially from the center of the through hole 11) between the opening edge 11a of the through hole 11 and the outer edge 310a of the land exposure portion 310, the distance D is maximized at D1 at the position along the major axis of the ellipse of the land exposure portion 310 and minimized at D2 at the position along the minor axis of the ellipse. And the width dimension L of the over-resist region 320 is minimized at L1 in the direction where the distance D is maximized at D1, and the width dimension L of the over-resist region 320 is maximized at L2 in the direction where the distance D is minimized at D2.

[0028] In other words, as shown in FIG. 4, the land exposed portion 310 has a pair of first regions 310b where the distance D from the opening edge 11a of the through hole 11 to the outer edge 310a of the land exposed portion 310 is relatively large, and a pair of second regions 310c where the distance D from the opening edge 11a of the through hole 11 to the outer edge 310a of the land exposed portion 310 is relatively small. On the outer peripheral side of the first region 310b, the width dimension L of the over-resist region 320 is relatively small, and on the outer peripheral side of the second region 310c, the width dimension L of the over-resist region 320 is relatively large.

[0029] When the soldering process is performed, stress is generated in the base material of the circuit board 3 near the opening edge 11a of the through hole 11. Therefore, if the outer edge 310a of the land exposed portion 310, which is the inner edge of the over-resist region 320 like the second region 310c, is close to the opening edge 11a of the through hole 11, there is a concern about the action of stress on the solder resist 32 that becomes the over-resist region 320. However, in the above embodiment, since the width dimension L of the over-resist region 320 is large (for example, L2) at a location where the outer edge 310a of the land exposed portion 310 is close to the opening edge 11a of the through hole 11, the occurrence of cracks in the solder resist 32 in the over-resist region 320 is suppressed. That is, the position of the interface between the land portion 31, which is likely to be the starting point of crack generation, and the solder resist 32 (that is, the outer edge 31a of the land portion 31) is separated from the opening edge 11a of the through hole 11, and cracks are less likely to occur.

[0030] In the first region 310b, the width dimension L of the over-resist region 320 is small (for example, L1), but in this first region 310b, the outer edge 310a of the land exposed portion 310, which is the inner edge of the over-resist region 320, is far from the opening edge 11a of the through hole 11. Therefore, even if the width dimension L of the over-resist region 320 is small, cracks are less likely to occur.

[0031] In addition, since the first region 310b becomes the heat-receiving position 33, even if the stress of the base material of the circuit board 3 due to thermal expansion and contraction becomes large at the heat-receiving position 33, the outer edge 310a of the land exposure portion 310 is sufficiently separated from the through-hole 11, so that crack suppression can be achieved. The width dimension L of the over-resist region 320 in the direction of the heat-receiving position 33 becomes relatively small among the circumferential directions because the outer edge 310a of the land exposure portion 310 is separated from the opening edge 11a of the through-hole 11, and becomes, for example, the minimum L1.

[0032] Therefore, in this first embodiment, the generation of cracks in the solder resist 32 in the over-resist region 320 can be effectively suppressed in each part in the circumferential direction of the annularly continuous over-resist region 320.

[0033] Incidentally, if the outer edge 310a of the land exposure portion 310 and the outer edge 31a of the land portion 31 are configured to form similar elliptical shapes with each other to form an over-resist region 320 having a constant width, cracks are likely to occur in the solder resist 32 in the over-resist region 320 at a portion along the minor axis of the ellipse where the outer edge 310a of the land exposure portion 310 is close to the through-hole 11.

[0034] Next, FIG. 5 shows the configuration of the land portion 31 of the second embodiment. In this second embodiment, the land portion 31 basically has the same shape as the land portion 31 of the first embodiment, and the outer edge 31a forms an elliptical shape centered on the through-hole 11, specifically, an elliptical shape in which a pair of semi-circles are connected by two parallel straight lines. The flatness ratio of this ellipse is relatively small. The peripheral portion of the land portion 31 has the solder resist 32 overlapped as an over-resist region 320 leaving the land exposure portion 310.

[0035] Here, in the second embodiment, the land exposed portion 310 has an elliptical shape in which its outer edge 310a is biased in one direction in the major axis direction with respect to the through hole 11. Specifically, it has a shape formed by connecting a pair of semi - circles with two parallel straight lines, and one of the semi - circles is located relatively close to the opening edge 11a of the through hole 11. As a result of the land exposed portion 310 being biased in one direction in the major axis direction with respect to the through hole 11, the land exposed portion 310 expands greatly in the radial direction from the opening edge 11a of the through hole 11 only in one direction which becomes the heat - receiving position 33. In the region on the opposite side of the heat - receiving position 33 across the through hole 11, the land exposed portion 310 is relatively small.

[0036] Also, compared with the radius of curvature R1 of the arc - shaped portion of the outer edge 31a of the land portion 31, the radius of curvature R2 of the arc - shaped portion of the outer edge 310a of the land exposed portion 310 is set relatively small. Here, in the second embodiment, on the side opposite to the heat - receiving position 33, the semi - circle of the land portion 31 and the semi - circle of the land exposed portion 310 have a concentric or nearly concentric relative relationship.

[0037] Therefore, the width dimension L of the over - resist region 320 is relatively large (for example, maximum L2) and substantially constant in the section between the concentric semi - circular portions and the pair of straight - line portions of the land portion 31, and is relatively small (minimum L1) in the major axis direction on the heat - receiving position 33 side.

[0038] Therefore, also in this second embodiment, the width dimension L of the over - resist region 320 is set large at the location where the outer edge 310a of the land exposed portion 310 is close to the opening edge 11a of the through hole 11, and at the location where the width dimension L of the over - resist region 320 is small, the outer edge 310a of the land exposed portion 310 is away from the opening edge 11a of the through hole 11. Thereby, the occurrence of cracks in the solder resist 32 which becomes the over - resist region 320 is suppressed in each part in the circumferential direction.

[0039] Also, in this second embodiment, since the land exposed portion 310 is enlarged only on one side where laser light is irradiated and solder material is supplied in the radial direction, the total area of the land exposed portion 310 is smaller than that in the first embodiment. Therefore, compared with the first embodiment, the solder fillet can be miniaturized, and the amount of heat required in the soldering process is reduced.

[0040] Next, FIG. 6 shows the configuration of the land portion 31 of the third embodiment. In this third embodiment, the outer edge 310a of the land exposed portion 310 has an elliptical shape centered on the through hole 11, similar to the first embodiment. Specifically, it has a shape formed by connecting a pair of semi - circles with two parallel straight lines, and the heat - receiving position 33 is set on one side in the major - axis direction.

[0041] For such a shape of the land exposed portion 310, the land portion 31 is configured such that its outer edge 31a forms a perfect circle centered on the through hole 11. Therefore, the width dimension L of the over - resist region 320 is minimum L1 at the portion along the major axis of the ellipse of the land exposed portion 310, and maximum L3 at the portion along the minor axis of the ellipse of the land exposed portion 310, particularly at the portion along the radius line passing through the center of the through hole 11 (that is, the portion where the distance D between the opening edge 11a of the through hole 11 and the outer edge 310a of the land exposed portion 310 is minimum). The circular land portion 31 of this third embodiment corresponds to the elliptical land portion 31 of the first embodiment with an aspect ratio of 0. Therefore, the width dimension L of the over - resist region 320 at each portion along the minor - axis direction of the ellipse of the land exposed portion 310 is larger than the width dimension L in the case of the first embodiment.

[0042] Also in such a third embodiment, cracks in the solder resist 32 in the over - resist region 320 are reliably suppressed in each portion in the circumferential direction.

[0043] As is clear from FIG. 6, the radius of the circular land portion 31 is larger than the radius of curvature of the arc - shaped portion of the outer edge 310a of the land exposed portion 310.

[0044] The asymmetric-shaped land exposure portion 310 of the second embodiment shown in FIG. 5 may be combined with the circular land portion 31 of the third embodiment shown in FIG. 6.

[0045] In addition to the shapes of the first to third embodiments described above, the land portion 31 can have an appropriate arbitrary shape. FIG. 7 shows a fourth embodiment in which the land portion 31 is square as an example. The outer edge 310a of the land exposure portion 310 forms an ellipse centered on the through hole 11, similar to the first and third embodiments. The land portion 31 forms a square with the through hole 11 located at the center, and each side of the square is parallel to the major and minor axis directions of the land exposure portion 310.

[0046] Also in such a fourth embodiment, at a portion where the distance D between the opening edge 11a of the through hole 11 and the land exposure portion 310 is small (the portion along the minor axis of the ellipse), the width dimension L of the over-resist region 320 becomes large, and at a portion where the width dimension L of the over-resist region 320 is small (the portion along the major axis of the ellipse), the distance D between the opening edge 11a of the through hole 11 and the outer edge 310a of the land exposure portion 310 is large. Therefore, in each part in the circumferential direction, cracks in the solder resist 32 in the over-resist region 320 are surely suppressed.

[0047] As described above, some embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and various modifications are possible. Although an elliptical example was shown for the land exposure portion 310 in each of the above embodiments, the present invention is not limited to this, and it can have any shape suitable for soldering to a terminal passing through the through hole 11. When the outer edge 310a of the land exposure portion 310 is an irregular shape with an uneven distance from the opening edge 11a of the through hole 11, as in each of the above embodiments, by relatively widening the width dimension L of the over-resist region 320 at a portion where the outer edge 310a of the land exposure portion 310 is close to the opening edge 11a of the through hole 11, crack generation at that portion is suppressed.

[0048] Also, even if the land exposed portion 310 is a perfect circle concentric with the through hole 11, by setting the shape of the land portion 31 such that the width dimension L of the over-resist region 320 partially increases in a predetermined direction in which the stress increases due to the soldering process, crack generation in the solder resist 32 in the over-resist region 320 can be suppressed.

[0049] In the above embodiment, the formation of the solder resist 32 by printing the solder resist ink has been described as an example. However, the present invention can be similarly applied when the solder resist 32 is formed by other methods such as a photographic method.

Explanation of Reference Numerals

[0050] 1... motor unit, 2... inverter power module, 3... circuit board, 4... connector member, 5... motor cover, 7... housing, 10... motor drive terminal, 11... through hole, 11a... opening edge, 31... land portion, 31a... outer edge, 310... land exposed portion, 310a... outer edge, 320... over-resist region.

Claims

1. An electronic device comprising a circuit board on which a plurality of electronic components are mounted and a solder resist is provided on the surface, and terminals passing through through-holes of the circuit board are soldered to an annular land portion surrounding the through-holes, wherein the land portion has an over-resist region where the solder resist is overlapped including at least the peripheral edge of the land portion, and a land exposure portion located closer to the through-hole side than the over-resist region and where the land surface around the through-hole is exposed, the outer edge shape of the land exposure portion is formed so as not to be similar to the outer edge shape of the land portion by the over-resist region, a part in the circumferential direction of the land exposure portion becomes a heat-receiving position in the soldering process, the width dimension of the over-resist region is small in the direction of the heat-receiving position, and relatively large in other directions, An electronic device.

2. An electronic device comprising a circuit board on which a plurality of electronic components are mounted and a solder resist is provided on the surface, and terminals passing through through-holes of the circuit board are soldered to an annular land portion surrounding the through-holes, wherein the land portion has an over-resist region where the solder resist is overlapped including at least the peripheral edge of the land portion, and a land exposure portion located closer to the through-hole side than the over-resist region and where the land surface around the through-hole is exposed, the outer edge shape of the land exposure portion is formed so as not to be similar to the outer edge shape of the land portion by the over-resist region, the land exposure portion expands radially outward at one location in the circumferential direction that becomes a heat-receiving position in the soldering process, the width dimension of the over-resist region at a circumferential position on the opposite side of the through-hole with respect to the location is relatively large compared to the width dimension of the over-resist region at the location, An electronic device.

3. An electronic device comprising a circuit board on which a plurality of electronic components are mounted, and terminals passing through through-holes of the circuit board are soldered to an annular land portion surrounding the through-holes, wherein a solder resist provided on the surface of the circuit board is formed by overlapping the peripheral edge of the land portion leaving a land exposure portion around the through-hole, the outer edge of the land exposure portion has an elliptical shape with a relatively large flatness ratio, The outer edge of the above-mentioned land portion forms an elliptical or circular shape with a relatively small flatness ratio. Electronic device.

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