JP7706283B2 - electronic equipment - Google Patents

Description

This invention relates to an improvement to an electronic device that includes a circuit board on which multiple electronic components are mounted, and in which terminals that pass through through holes in the circuit board are soldered to annular lands that surround the through holes.

In the circuit boards of various electronic devices, terminals that pass through through holes in the circuit board are sometimes soldered to an annular land portion that surrounds the through hole. In such cases, there is a concern that the land portion may peel off or lift off from the board surface due to heating during soldering, etc.

Patent Document 1 discloses that in order to prevent the land from peeling off or lifting up, a solder resist is provided at a constant width (e.g., 0.15 mm width) around the periphery of the land. In other words, in Patent Document 1, a so-called over resist area where the solder resist overlaps the land is formed at a constant width around the entire periphery of the land.

JP 2006-332434 A

In a configuration with an over-resist area where the solder resist overlaps the land portion as described above, soldering the terminal generates stress in the board around the through-hole, which can cause cracks in the solder resist in the over-resist area. In particular, the closer the outer edge of the land portion, which forms the interface between the metal land portion and the solder resist material, is to the edge of the through-hole opening, the more likely it is that cracks will occur.

In one aspect, the present invention is an electronic device comprising a circuit board on which a plurality of electronic components are mounted and on whose surface a solder resist is provided, and a terminal passing through a through hole of the circuit board is soldered to an annular land portion surrounding the through hole, the land portion having an over resist area including at least the peripheral portion of the land portion and overlaid with the solder resist, and a land exposed portion located on the through hole side of the over resist area and exposing the land surface surrounding the through hole, the outer edge shape of the land exposed portion being formed by the over resist area so that it is not similar to the outer edge shape of the land portion.
For example, a part of the circumferential direction of the exposed land portion serves as 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 circumferential location that is a heat receiving location in a soldering process,
The width dimension of the over resist region at the relevant location is relatively larger than the width dimension of the over resist region at a circumferential position on the opposite side of the relevant location with the through hole interposed therebetween.
In another aspect of the present invention, there is provided an electronic device comprising 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,
a solder resist provided on a surface of the circuit board is formed to overlap a peripheral edge of the land portion, leaving an exposed land portion around the through hole;
The outer edge of the land exposed portion has an elliptical shape with a relatively large flattening ratio,
The outer edge of the land portion is elliptical or circular with a relatively small flattening ratio.

This invention makes it possible to keep the outer edge of the land away from the edge of the through-hole opening while still allowing the shape of the exposed land portion to be soldered as desired, thereby preventing cracks from occurring in the solder resist in the over-resist area.

1 is an exploded perspective view of an electric actuator device for a power steering apparatus according to an embodiment of the present invention; FIG. FIG. 4 is a plan view showing the configuration of a land portion according to the first embodiment. FIG. 2 is an explanatory diagram showing the dimensional relationship between the various parts of the first embodiment. FIG. 11 is a plan view showing the configuration of a land portion according to a second embodiment. FIG. 13 is a plan view showing the configuration of a land portion according to a third embodiment. FIG. 13 is a plan view showing the configuration of a land portion according to a fourth embodiment.

Below, one embodiment of the invention will be described in detail with reference to the drawings.

First, we will briefly explain the overall configuration of an electronic device according to one embodiment of the present invention. In one embodiment, the present invention is applied to an electric actuator device 101 of an electric power steering device for an automobile, as shown in FIG. 1. Note that the basic configuration of this electric actuator device 101 is disclosed in, for example, JP 2020-148639 A, so we will only explain it to the minimum extent necessary here.

Figure 1 is an exploded perspective view of an electric actuator device 101 that applies 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 section 1, an inverter/power module 2, a circuit board 3 made of a multi-layer circuit board bent into an approximately U-shape, a connector member 4 that is an integral assembly of multiple connectors, and a motor cover 5 that is attached to one end of the motor section 1 so as to cover the inverter/power module 2, the circuit board 3, and the connector member 4.

The motor section 1 is a three-phase AC motor housed inside a cylindrical housing 7, and has a gear or spline or other connecting part 6a at the tip of the rotating shaft 6 protruding from the tip surface of the housing 7, and is connected to the steering mechanism via this connecting part 6a. The motor is a three-phase permanent magnet type brushless motor, with a stator equipped with three-phase coils and permanent magnets arranged on the outer circumferential surface of the rotor. The motor also has two systems of coils and corresponding permanent magnets to provide redundancy.

One end of the housing 7 opposite the connecting portion 6a is configured as a bottom wall portion 7a having a horseshoe-shaped outline with a portion of the outer periphery extending in the radial direction, and a motor cover 5 having a horseshoe-shaped outline corresponding to the bottom wall portion 7a is attached so as to cover this bottom wall portion 7a. Then, in the space formed between the bottom wall portion 7a and the motor cover 5, the inverter power module 2, the circuit board 3, and the connector member 4 are housed in a stacked manner in the axial direction of the rotating shaft 6. Here, both ends of each coil of the motor penetrate the bottom wall portion 7a as coil terminal portions 9 and protrude toward the motor cover 5, and are connected to the corresponding terminals of the inverter power module 2 by TIG welding or the like.

The inverter power module 2 includes two inverter modules 2A that drive the motor and a relay module 2B that serves as a neutral relay for the coil, and these three are arranged to form an approximate U-shape surrounding the rotating shaft 6. The inverter modules 2A and relay module 2B are fixed to the end face of the motor section 1 via a pressing member 2C. The inverter modules 2A and relay module 2B also include a number 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 described below, are passed through through holes 11 in the circuit board 3 and are electrically connected to the wiring of the circuit board 3 by laser soldering.

The connector member 4 has three connectors that face in the same axial direction of the rotating shaft 6. More specifically, it has a power connector 4a located in the center, a sensor input connector 4b that receives signals from sensors (such as a steering angle sensor and a torque sensor) arranged on the steering mechanism side, and a communication connector 4c for communication (such as CAN communication) with other control devices inside the vehicle. These connectors 4a, 4b, and 4c protrude to the outside through an opening 8 in the motor cover 5.

The circuit board 3 is composed of a multi-layer printed wiring board, for example a so-called eight-layer printed wiring board with eight metal foil layers (e.g. copper foil layers). This multi-layer printed wiring board is constructed by laminating several layers of base material, for example made of glass epoxy, with metal foil layers on one or both sides, via prepregs (adhesive layers), and integrating them by heating and pressing. The desired circuit pattern is then constructed by etching each metal foil layer and forming vias that extend in the stacking direction.

The circuit board 3 is arranged between the bottom wall 7a of the housing 7 and the connector member 4 in a substantially U-shaped bent shape. FIG. 2 shows the circuit board 3 in an unfolded state. The circuit board 3 includes a first rigid part 21, which is a power system board mounting a group of electronic components through which a relatively large current flows to drive the motor via the inverter power module 2, a second rigid part 22, which is a control system board mounting a control system electronic component through which a relatively small current flows, and a flexible part 23 in which the number of layers of the substrate between the first rigid part 21 and the second rigid part 22 is reduced. The circuit board 3 is accommodated between the housing 7 and the motor cover 5, which is a case, with the flexible part 23 in a flexed and deformed state so that the first rigid part 21 and the second rigid part 22 overlap each other in the axial direction of the rotating shaft 6. The first rigid part 21 and the second rigid part 22 in the folded state are separated by a distance such that the electronic components mounted on each part do not come into contact with each other, and are supported in a parallel state while maintaining their respective planar states.

As shown in FIG. 2, the numerous 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 the inner surface when folded. That is, lands for connecting the electronic components 24 are formed in the metal foil layer on the surface of the circuit board 3, which is made of a multilayer printed circuit board, and after applying a solder resist, which will be described later, cream solder is printed on these lands by a printing technique using masking. Then, after mounting the electronic components 24 in their respective predetermined locations, the circuit board 3 is heated in an oven to melt the solder, thereby soldering them. Note that some electronic components are mounted on the second surface, which is the opposite surface to the first surface 3A, and these are also simultaneously reflow soldered.

Circular through-holes 11 are formed in the first rigid portion 21 of the circuit board 3, through which the pin-shaped motor drive terminals 10 extending from the inverter power module 2 described above pass, 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, rather than by reflow soldering. In the laser soldering process, the tip of the wire-shaped solder material sent onto the land portions 31 is heated and melted by irradiation with laser light, forming a fillet that covers the land portions 31 together with the terminals 10.

Next, the configuration of the land portion 31, which is a main part of the present invention, will be described with reference to FIG. 3 and FIG. 4. FIG. 3 and FIG. 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 of the multilayer circuit board. On the metal foil layer of the circuit board 3, a solder resist 32 is further provided as an insulating coating to prevent solder from adhering to unnecessary places and to protect the circuit pattern. The solder resist 32 is made of so-called solder resist ink, and is applied to substantially the entire surface of the circuit board 3 using a printing technique such as screen printing, except for the land portions such as the land portion 31 that require soldering and the outer periphery of the circuit board 3. In other words, the solder resist 32 is layered on the etched metal foil layer, and the substrate surface and the circuit pattern (circuit wiring) of the circuit board 3 are covered with the solder resist 32.

Here, in order to prevent the land portion 31 from peeling off or lifting up at the peripheral portion of the annular land portion 31 surrounding the through hole 11, the solder resist 32 is provided overlapping the land portion 31. In the present invention, the area of the solder resist 32 overlapping the land portion 31 is called the over resist area 320, and the central portion of the land portion 31 that is exposed and not covered by the solder resist 32 (but will eventually be covered by a solder fillet) 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 area 320. The outer edge of the land portion 31 is indicated by a dashed line with the reference symbol 31a. The outer edge 31a of the land portion 31 indicated by this dashed line is covered by the solder resist 32.

The dimensions of the land exposed portion 310 are set according to the size of the desired solder fillet formed by laser soldering, and in particular, the land exposed portion 310 is elliptical with the through hole 11 at the center, taking into consideration the workability in the laser soldering process. In the laser soldering process, a laser beam is irradiated along the long axis direction of the ellipse toward the heat receiving position shown by the circle with the reference numeral 33 in FIG. 4, and the tip of the wire-shaped solder material is sent to the vicinity of the heat receiving position 33 so as to receive the laser beam. As shown in FIG. 4, the heat receiving position 33 is set near the position where the long axis of the ellipse intersects with the opening edge of the through hole 11. The land exposed portion 310 is formed in an elliptical shape in order to ensure that the solder material is supplied to the land exposed portion 310 even if there is a product error or equipment error in the laser soldering process. In the present invention, the term "elliptical shape" is not limited to a narrow elliptical shape based on a strict mathematical definition, but means an elliptical shape in a broad sense that broadly includes so-called oval shapes and rugby ball shapes. The example shown is not an ellipse in the strict mathematical sense, but rather a shape that is included in the broader definition of an ellipse, consisting of a pair of semicircles connected by two parallel lines (a shape often called an oval).

The land portion 31 has a larger ellipse than the land exposed portion 310, and the directions of the major and minor axes of the land exposed portion 310 are the same. Therefore, between the outer edge 31a of the land portion 31 and the outer edge 310a of the land exposed portion 310, there is an over resist region 320 that is continuous in a ring shape around the entire circumference. Here, the outer edge 310a of the land exposed portion 310 has an ellipse with a relatively large flattening ratio, and the outer edge 31a of the land portion 31 has an ellipse with a relatively small flattening ratio. The flattening ratio is defined as "(major axis - minor axis) / major axis", and is 0 for a perfect circle. In the illustrated example, the outer edge 31a of the land portion 31 has a broad ellipse shape formed by connecting a pair of semicircles with two parallel straight lines. In this way, the outer edge 31a of the land portion 31 and the outer edge 310a of the land exposed portion 310 are not similar to each other, and therefore the width dimension L of the annular 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 a direction perpendicular to the tangent at each part of the outer edge 310a of the land exposed portion 310.

In the first embodiment, the width dimension L of the over resist region 320 is smallest along the major axis of the ellipse of the land exposed portion 310, and is largest along the minor axis.

Figure 4 is an explanatory diagram showing the dimensional relationship of each part in the first embodiment, in which the minimum width dimension L of the over resist area 320 along the major axis of the ellipse of the land exposed portion 310 is shown as L1, and the maximum width dimension L of the over resist area 320 along the minor axis is shown as L2. Where the outer edge 31a of the land portion 31 forms a straight line, the width dimension L is constant (maximum L2). Where the outer edge 31a of the land portion 31 forms an arc, the width dimension L changes gradually.

Compared to the radius of curvature R1 of the outer edge 31a of the land portion 31 where the outer edge 31a forms an arc, the radius of curvature R2 of the arc of the outer edge 310a of the land exposed portion 310 is relatively small. Therefore, the width dimension L increases from the part along the major axis of the ellipse that is the center of the semicircle toward both ends of the semicircle (the connection parts with the straight parts).

On the other hand, when we look at the distance D (the 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 exposed portion 310, the distance D is at its maximum D1 at a position along the major axis of the ellipse of the land exposed portion 310, and at its minimum D2 at a position along the minor axis of the ellipse. The width dimension L of the over resist region 320 is at its minimum L1 in the direction where the distance D is at its maximum D1, and at its maximum L2 in the direction where the distance D is at its minimum D2.

In other words, as shown in FIG. 4, the land exposed portion 310 has a pair of first regions 310b in which 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 in which 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. The width dimension L of the over resist region 320 is relatively small on the outer periphery side of the first regions 310b, and the width dimension L of the over resist region 320 is relatively large on the outer periphery side of the second regions 310c.

After the soldering process, 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, is close to the opening edge 11a of the through hole 11 as in the second region 310c, there is a concern that stress will act on the solder resist 32, which is the over resist region 320. However, in the above embodiment, the width dimension L of the over resist region 320 is large (for example, L2) 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, so that cracks in the solder resist 32 in the over resist region 320 are suppressed. In other words, the position of the interface between the land portion 31 and the solder resist 32 (i.e., the outer edge 31a of the land portion 31), which is likely to be the starting point of cracks, is away from the opening edge 11a of the through hole 11, making it difficult for cracks to occur.

In the first region 310b, the width dimension L of the over resist region 320 is small (e.g., 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 away 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 unlikely to occur.

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 exposed portion 310 is sufficiently separated from the through hole 11, thereby suppressing cracks. The width dimension L of the over resist region 320 in the direction of the heat receiving position 33 becomes relatively small in the circumferential direction, for example the minimum L1, because the outer edge 310a of the land exposed portion 310 is separated from the opening edge 11a of the through hole 11.

Therefore, in this first embodiment, the occurrence of cracks in the solder resist 32 in the over-resist region 320 can be effectively suppressed in each circumferential portion of the annularly continuous over-resist region 320.

If the outer edge 310a of the land exposed portion 310 and the outer edge 31a of the land portion 31 are configured to form similar ellipses to form an over resist region 320 of a constant width, cracks are likely to occur in the solder resist 32 in the over resist region 320 at the location along the minor axis of the ellipse where the outer edge 310a of the land exposed portion 310 is close to the through hole 11.

Next, FIG. 5 shows the configuration of the land portion 31 of the second embodiment. In this second embodiment, the land portion 31 is basically the same shape as the land portion 31 of the first embodiment, and the outer edge 31a is an ellipse centered on the through hole 11, more specifically, an ellipse formed by connecting a pair of semicircles with two parallel straight lines. The flattening ratio of this ellipse is relatively small. The peripheral edge of the land portion 31 is overlaid with solder resist 32 as an over resist area 320, leaving the land exposed portion 310.

Here, in the second embodiment, the land exposed portion 310 has an elliptical shape with its outer edge 310a biased to one side in the long diameter direction relative to the through hole 11. More specifically, it has a shape in which a pair of semicircles are connected by two parallel straight lines, and one of the semicircles 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 to one side in the long diameter direction relative to the through hole 11 in this way, the land exposed portion 310 is greatly expanded in the radial direction from the opening edge 11a of the through hole 11 only in one direction, which is the heat receiving position 33. In the area opposite the heat receiving position 33 across the through hole 11, the land exposed portion 310 is relatively small.

Furthermore, compared to the radius of curvature R1 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 to be relatively small. Here, in the second embodiment, on the side opposite the heat receiving position 33, the semicircle of the land portion 31 and the semicircle of the land exposed portion 310 have a relative relationship that is concentric or close to concentric.

Therefore, the width dimension L of the over resist region 320 is a relatively large (e.g., maximum L2) approximately constant dimension in the section between the concentric semicircular portion and the pair of straight portions of the land portion 31, and is relatively small (minimum L1) in the long diameter direction on the heat receiving position 33 side.

Therefore, in this second embodiment, the width dimension L of the over resist region 320 is set large where the outer edge 310a of the land exposed portion 310 is close to the opening edge 11a of the through hole 11, and where the width dimension L of the over resist region 320 is small, the outer edge 310a of the land exposed portion 310 is farther away from the opening edge 11a of the through hole 11. This suppresses the occurrence of cracks in the solder resist 32 that forms the over resist region 320 at each portion in the circumferential direction.

In addition, in this second embodiment, the land exposed portion 310 is larger in the radial direction only on one side where the laser light is irradiated and the solder material is supplied, so the total area of the land exposed portion 310 is smaller than in the first embodiment. Therefore, the solder fillet can be made smaller than in the first embodiment, and the amount of heat required in the soldering process is reduced.

Next, FIG. 6 shows the configuration of the land portion 31 in the third embodiment. In this third embodiment, the outer edge 310a of the land exposed portion 310 is elliptical with the through hole 11 at its center, as in the first embodiment. More specifically, it is shaped like a pair of semicircles connected by two parallel straight lines, and the heat receiving position 33 is set on one side of the long axis.

For the shape of the land exposed portion 310, the land portion 31 is configured so that its outer edge 31a forms a perfect circle with the through hole 11 at the center. 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 is maximum L3 at the portion along the minor axis of the ellipse of the land exposed portion 310, particularly at the portion along the radial line passing through the center of the through hole 11 (i.e., 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 perfect circular land portion 31 of the third embodiment corresponds to the elliptical land portion 31 of the first embodiment with the flattening ratio set to 0, and therefore the width dimension L of the over resist region 320 at each portion along the minor axis of the ellipse of the land exposed portion 310 is larger than the width dimension L in the first embodiment.

Even in this third embodiment, cracks in the solder resist 32 in the over resist region 320 are reliably suppressed at each portion in the circumferential direction.

As is clear from FIG. 6, the radius of the land portion 31, which is a perfect circle, is larger than the radius of curvature of the arc-shaped portion of the outer edge 310a of the land exposed portion 310.

The asymmetric land exposed 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.

The land portion 31 can have any suitable shape, in addition to the shapes of the first to third embodiments described above. FIG. 7 shows a fourth embodiment in which the land portion 31 is rectangular as an example. The outer edge 310a of the land exposed portion 310 is elliptical with the through hole 11 at its center, as in the first and third embodiments. The land portion 31 is square with the through hole 11 located at its center, and each side of the square is parallel to the long and short diameter directions of the land exposed portion 310.

Even in this fourth embodiment, the width dimension L of the over resist region 320 is large in the area where the distance D between the opening edge 11a of the through hole 11 and the land exposed portion 310 is small (the area along the minor axis of the ellipse), and 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 large in the area where the width dimension L of the over resist region 320 is small (the area along the major axis of the ellipse). Therefore, cracks in the solder resist 32 in the over resist region 320 are reliably suppressed at each part in the circumferential direction.

Although several embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and various modifications are possible. In the above embodiments, the land exposed portion 310 is shown as an ellipse, but the present invention is not limited to this and can be any shape suitable for soldering to a terminal that penetrates the through hole 11. If the outer edge 310a of the land exposed portion 310 has an irregular shape with an uneven distance from the opening edge 11a of the through hole 11, as in the above embodiments, the width dimension L of the over resist region 320 is relatively wide in the portion where the outer edge 310a of the land exposed portion 310 is close to the opening edge 11a of the through hole 11, thereby suppressing the occurrence of cracks in that portion.

Even if the land exposed portion 310 is a perfect circle concentric with the through hole 11, the shape of the land portion 31 is set so that the width dimension L of the over resist region 320 is partially increased in a specific direction where stress is high due to the soldering process, thereby making it possible to suppress the occurrence of cracks in the solder resist 32 in the over resist region 320.

In the above embodiment, the solder resist 32 is formed by printing solder resist ink, but the present invention can also be applied to cases where the solder resist 32 is formed by other methods, such as photography.

1...motor section, 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 section, 31a...outer edge, 310...land exposed section, 310a...outer edge, 320...over resist area.

Claims (3)

An electronic device comprising a circuit board on which a plurality of electronic components are mounted and on which a solder resist is provided on a surface, and a terminal passing through a through hole of the circuit board is soldered to an annular land portion surrounding the through hole,
the land portion has an over resist region including at least a peripheral portion of the land portion and overlaid with the solder resist, and a land exposed portion located closer to the through hole than the over resist region and exposing the land surface around the through hole;
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 due to the over resist region;
A circumferential portion of the exposed land portion serves as a heat receiving position during 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;
electronic equipment. An electronic device comprising a circuit board on which a plurality of electronic components are mounted and on which a solder resist is provided on a surface, and a terminal passing through a through hole of the circuit board is soldered to an annular land portion surrounding the through hole,
the land portion has an over resist region including at least a peripheral portion of the land portion and overlaid with the solder resist, and a land exposed portion located closer to the through hole than the over resist region and exposing the land surface around the through hole;
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 due to the over resist region;
The land exposed portion expands radially outward at one circumferential location that is a heat receiving location in a soldering process,
the width dimension of the over resist region at the location is relatively larger than the width dimension of the over resist region at a circumferential position on the opposite side of the location with the through hole interposed therebetween;
electronic equipment. An electronic device comprising 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,
a solder resist provided on a surface of the circuit board is formed to overlap a peripheral edge of the land portion, leaving an exposed land portion around the through hole;
The outer edge of the land exposed portion has an elliptical shape with a relatively large flattening ratio,
The outer edge of the land portion is an ellipse or a circle having a relatively small flattening ratio.
electronic equipment.

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