JP6300554B2 - Printed board - Google Patents

Description

  The present invention relates to a printed circuit board, and more particularly to a land of the printed circuit board.

  When mounting a surface mount component (such as an electronic component) having low heat resistance on a printed circuit board, a reflow method in which cream solder is printed on a land and then melted by heat is employed as a soldering method. Note that the reflow method has a smaller amount of solder than the flow method in which the lower surface of the printed circuit board is immersed in a molten solder bath. For this reason, when mounting a large surface-mounted component on a printed circuit board, it is necessary to pay attention to reflow execution conditions so that the surface-mounted component and the land can be soldered reliably.

  By the way, in recent years, lead-free soldering has been promoted in consideration of the environment. Since lead-free solder has a higher melting temperature than conventional eutectic solder, the reflow temperature and reflow time increase accordingly. Here, in the reflow method using lead-free solder, a temperature difference between the electrode of the surface mount component and the land of the printed circuit board tends to occur. When the temperature difference between the electrode and the land increases, the solder is attracted to the electrode side by the surface tension of the molten solder. As a result, the solder fillet formed by the solidification of the solder is biased toward the surface-mounted component, and there is a problem that the surface-mounted component and the land are not soldered well.

  Therefore, a technique has been proposed in which the electrode is formed so that the angle formed by the electrode surface and the land surface is an acute angle of less than 90 °, and the molten solder is prevented from being attracted to the electrode side (for example, a patent) Reference 1).

JP 2008-294390 A (see, for example, FIG. 2)

  The technique described in Patent Document 1 is based on the premise that a surface-mounted component obtained by custom processing an electrode into a preset shape is used. In other words, general-purpose components purchased from electrical and surface mount component manufacturers are based on the premise that surface mount components with electrodes formed so that the angle between the electrode surface and the land surface is an acute angle of less than 90 ° are mounted on a printed circuit board. By using, it is not possible to prevent the molten solder from being attracted to the electrode side.

  The electrode shape of general-purpose surface-mounted components is often a right angle of 90 ° between the electrode surface and the land surface. Therefore, a problem with general-purpose surface-mounted components is that a phenomenon in which molten solder is attracted to the electrode side (so-called solder suction) occurs.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a printed circuit board that can suppress solder sucking even when a general-purpose surface-mounted component is mounted.

The printed circuit board according to the present invention is a printed circuit board having lands to which the first surface-mounted component and the second surface-mounted component are soldered, and the land is provided with one electrode of the first surface-mounted component. First mounting portion, second mounting portion on which the other electrode of the first surface mounting component is placed, and third mounting on which one electrode of the second surface mounting component is placed , A fourth mounting portion on which the other electrode of the second surface mounting component is placed, a first protrusion extending from the edge of the first mounting portion, and a second extension extending from the second mounting portion and second protruding portions, and a third protrusion extending from the third mounting portion, and a fourth protrusion extending from the edge of the fourth mounting portion possess, first mounting portion, a second mounting Part, the third mounting part, and the fourth mounting part are the first mounting part, the second mounting part, the third mounting part, and the fourth mounting part in the order of the first mounting part. The second mounting portion has a first opposing edge that is an edge provided on the third mounting portion side, and the third mounting portion is the second mounting portion. A second opposing edge that is an edge provided on the side, and the second protrusion extends from the first opposing edge toward the second opposing edge, The protrusion extends from the second opposite edge toward the first opposite edge, and the second protrusion and the third protrusion are orthogonal to the first direction and a land is formed. Are arranged side by side in a second direction parallel to the substrate surface .

  Since the printed circuit board according to the present invention has the above-described configuration, it is possible to suppress solder sucking even when a general-purpose surface-mounted component is mounted.

It is a top view of the land formed in the printed circuit board concerning an embodiment of the invention. It is a side view of the printed circuit board concerning an embodiment of the invention. It is a top view of the state in which surface mount components were mounted on the land formed in the printed circuit board concerning an embodiment of the invention. It is a side view of the state in which the surface mount component is mounted on the land of the printed circuit board according to the embodiment of the present invention. It is modification 1 of the land of the printed circuit board which concerns on embodiment of this invention. It is the modification 2 of the land of the printed circuit board which concerns on embodiment of this invention. It is the modification 3 of the land of the printed circuit board which concerns on embodiment of this invention. It is the modification 4 of the land of the printed circuit board which concerns on embodiment of this invention.

  Hereinafter, embodiments of a printed circuit board 100 according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below. Moreover, in the following drawings including FIG. 1, the relationship of the size of each component may be different from the actual one.

Embodiment.
FIG. 1 is a plan view of a land 1 formed on a printed circuit board 100 according to the present embodiment. FIG. 2 is a side view of the printed circuit board 100 according to the present embodiment. The printed circuit board 100 will be described with reference to FIGS. 1 and 2.
The printed circuit board 100 according to the present embodiment is provided with an improvement that can suppress the sucking of the solder even when the general-purpose surface-mounted component 3 is mounted on the printed circuit board 100.

  The printed circuit board 100 is obtained by stacking, for example, a pattern wiring made of a metal such as copper and an insulating layer that insulates the pattern wiring. The printed circuit board 100 is formed with lands 1 on which the surface-mounted component 3 (see FIGS. 3 and 4) having the electrodes 4 on the opposing surface is mounted. An electrode 4 is formed on one surface side of the surface mount component 3. In the example of FIGS. 1 and 2, the electrodes 4 are formed on the two opposing surfaces. The surface-mounted component 3 is not a custom-processed electrode having a preset shape, but corresponds to a general-purpose electronic component.

  The land 1 is a conductor that is formed on the surface of the printed circuit board 100 and is electrically connected to a pattern wiring formed on the printed circuit board 100, and is made of a metal such as copper. A reflow cream solder layer 7 is formed on the upper surface of the land 1. For example, the cream solder layer 7 is formed on the upper surface of the land 1 by a printing method or the like. The cream solder layer 7 is made of, for example, lead-free cream solder.

  The land 1 is connected to one mounting portion 1a on which the electrode 4 provided on the end portion side of the surface mounting component 3 is placed, and an edge of the mounting portion 1a, and extends to the side away from the surface mounting component 3. It has a projection 1b. In the present embodiment, an example in which one surface mount component 3 is placed on a plurality of (two) lands 1 is shown. The mounting portion 1a has a rectangular shape with four sides when viewed from above. Here, the X direction shown in FIGS. 1 and 2 is a direction parallel to the short side of the mounting portion 1a, and the Y direction is a direction parallel to the long side of the mounting portion 1a. The mounting portion 1a has a first edge T1 and a second edge T2 parallel to the Y direction, and has a third edge T3 and a fourth edge T4 parallel to the X direction. .

  The first edge portion T <b> 1 is a portion facing the lower surface side of the surface mount component 3. The second edge portion T2 is a portion disposed at a position opposite to the first edge portion T1. The surface mount component 3 is not disposed on the upper side of the second edge T2. In the present embodiment, the first edge portion T <b> 1 and the second edge portion T <b> 2 are formed in parallel to the formation surface of the electrode 4 of the surface mount component 3. The third edge T3 is a part orthogonal to the first edge T1 and the second edge T2. Further, the fourth edge portion T4 is a portion disposed at a position opposite to the third edge portion T3.

  The protrusion 1b is formed so as to extend to the side away from the surface mount component 3. Specifically, the protruding portion 1b is connected to the second edge T2 of the mounting portion 1a and is formed to extend in the X direction from the first edge T1 side toward the second edge T2 side. It is what has been. A plurality of protrusions 1b are formed on the second edge T2 corresponding to one of the four sides of the mounting portion 1a. In other words, two mounting portions 1b are formed on the mounting portion 1a shown in FIGS.

  The protrusions 1b are formed at equal intervals on the second edge T2. That is, as shown in FIG. 1, when the distance between the protrusion 1b on the third edge T3 side and the protrusion 1b on the fourth edge T4 side is A, the protrusion on the third edge T3 side. The distance between the portion 1b and the third edge T3 and the distance between the protrusion 1b on the fourth edge T4 side and the fourth edge T4 are A.

  Here, one of the two mounting portions 1a shown in FIGS. 1 and 2 constitutes the first mounting portion 1a, and the other constitutes the second mounting portion 1a. The first mounting portion 1a is one on which one electrode 4 of the surface mounting component 3 is placed. The second mounting portion 1a is formed at a position facing the first mounting portion 1a, and the other electrode. 4 is placed. The first mounting portion 1a and the second mounting portion 1a are formed so that the first edge T1 faces each other, and the protrusion 1b is formed on the second edge T2 on the opposite side of the first edge T1. Is formed.

FIG. 3 is a plan view of a state in which the surface-mounted component 3 is mounted on the land 1 formed on the printed circuit board 100 according to the embodiment. FIG. 4 is a side view of the state in which the surface mount component 3 is mounted on the land 1 of the printed circuit board 100 according to the present embodiment.
The surface mount component 3 is installed on the printed circuit board 100 shown in FIG. 2, and is put into a reflow furnace. Thereby, the electrode 4 and the land 1 are electrically and physically connected. As shown in FIG. 4, the electrode 4 and the land 1 are electrically and physically connected by a solder fillet portion 5 formed by melting cream solder by reflow. Note that the angle formed by the surface of the electrode 4 and the surface of the land 1 is approximately 90 ° in the example shown in FIG.

  When the printed circuit board 100 is put into a reflow furnace in a state where the surface mounted component 3 is placed on the printed circuit board 100, the printed circuit board 100, the surface mounted component 3 and the cream solder layer 7 are heated. And the cream solder layer 7 melt | dissolves and the land 1 and the electrode 4 become familiar. When the melted cream solder is cooled, the land 1 and the electrode 4 are soldered by the solder fillet portion 5.

  Here, a temperature difference is generated between the land 1 and the electrode 4 in the process in which the solder fillet portion 5 is formed after being put into the reflow furnace. Therefore, force F1 sucked up to the electrode 4 side acts on the molten solder due to the surface tension generated in the molten solder. On the other hand, the printed circuit board 100 is formed with a protrusion 1b that protrudes away from the surface-mounted component 3. For this reason, force F2 pulled to the protrusion 1b side also acts on the molten solder. An extra force F2 that is pulled toward the protrusion 1b is generated as much as the protrusion 1b is formed. That is, in the process of forming the solder fillet portion 5, the printed circuit board 100 has a force F <b> 2 pulled toward the protruding portion 1 b as much as the protruding portion 1 b so as to reduce the force F <b> 1 sucked up to the electrode 4 side. Working extra.

  Here, when the width in the direction parallel to the X direction of the mounting portion 1a, that is, the length of the third edge portion T3 and the fourth edge portion T4 is L0, the protrusion portion 1b is parallel to the X direction. The width L may satisfy the relationship of L> 1 / 2L0. In this embodiment, L≈L0. Thus, if the width L in the direction parallel to the X direction of the protrusion 1b is set, the force F1 can be effectively reduced.

  For this reason, it is suppressed that the molten solder is sucked up to the upper part of the electrode 4 and solidifies as it is, and the solder fillet portion 5 formed by solidifying the molten solder is not easily biased toward the electrode 4 side. Specifically, as shown in FIG. 4, the solder fillet portion 5 formed by solidifying the solder is formed in a skirt shape from the lower side of the electrode 4 to the protruding portion 1 b side. If the protruding portion 1 b is not formed, the molten solder is sucked up to the upper side of the electrode 4, and a solder fillet is formed up to the upper portion of the electrode 4. On the other hand, the printed circuit board 100 is formed in a skirt shape from the lower side of the electrode 4 to the protruding portion 1 b side, and a balanced solder fillet portion 5 is formed between the electrode 4 and the land 1.

  In addition, since the bias of the solder fillet portion 5 varies depending on the size and shape of the electrode 4, the width, length, and number of the protruding portions 1b may be considered according to the application target. Furthermore, when optimizing the protrusion 1b, it is preferable to repeat the work of collecting data by performing reflow trials under several conditions and feeding back the results to the specifications of the protrusion 1b.

[Effects of printed circuit board 100 according to the present embodiment]
Since the printed circuit board 100 according to the present embodiment includes the land 1 that is connected to the edge of the mounting portion 1a and has a protrusion 1b that extends to the side away from the surface mounting component 3, a general-purpose surface mounting Even when the component 3 is mounted, solder sucking can be suppressed. For this reason, even the general-purpose surface-mounted component 3 can be satisfactorily soldered onto the land 1.

Here, the larger the width L (projection amount) in the direction parallel to the X direction of the protrusion 1b, the greater the force for pulling the molten solder toward the protrusion 1b. The width L can be increased with the same increased area by providing the protruding portion 1b that is partially protruded from the shape in which the area of the land 1 is entirely increased outward by the same area as the protruding portion 1b. Can do.
Since the printed circuit board 100 according to the present embodiment does not have a shape in which the area of the land 1 is increased to the outside as a whole, it is possible to further increase the force for pulling the formed solder fillet portion 5 to the outside while further increasing the partial area. Since it has a protruding shape, an increase in the amount of solder used can also be suppressed.

  Further, conventionally, it is difficult to suppress solder sucking unless a custom-processed product such as a discrete component is used as the surface mount component 3. However, in the printed circuit board 100 according to the present embodiment, it is possible to suppress the solder sucking even in the general-purpose surface-mounted component 3, and it is possible to realize a high-density design of the printed circuit board 100.

In the present embodiment, the mounting portion 1a has been described as having two protrusions 1b formed on the second edge T2, but the present invention is not limited to this, and the mounting portion 1a may be singular. Three or more may be formed.
Moreover, although the two projection parts 1b were formed in both the mounting parts 1a, it is not limited to it. That is, the mounting portions 1a do not have to be symmetrical, and for example, two mounting portions 1a may be formed on one mounting portion 1a and one mounting portion 1a may be formed.

  The mounting portion 1a has a rectangular shape, that is, the first edge portion T1, the second edge portion T2, the third edge portion T3, and the fourth edge portion T4 are linearly formed, and the first edge portion Although T1 and 2nd edge part T2, 3rd edge part T3, and 4th edge part T4 were demonstrated as orthogonally crossing, it is not limited to it. For example, the first edge portion T1, the second edge portion T2, the third edge portion T3, and the fourth edge portion T4 may be deviated from a straight line, for example, a part of which is formed in a curved shape. It may be.

  Although the shape on the tip side of the protrusion 1b has been described as being round (semicircular), it is not limited thereto. For example, the tip of the protrusion 1b may be rectangular, or the entire protrusion 1b may be rectangular. Further, the tip of the protrusion 1b may be triangular or trapezoidal. Alternatively, the entire protrusion 1b may be triangular or trapezoidal.

  In the present embodiment, the protrusion 1b having the same shape is formed, but the present invention is not limited to this. That is, in the case where a plurality of protrusions 1b are formed on one mounting part 1a, the protrusions 1b having different shapes may be formed.

In the present embodiment, it has been described that the protrusions 1b are formed on both the mounting parts 1a on which the same surface-mounted component 3 is mounted. However, the present invention is not limited to this. For example, the aspect by which the projection part 1b is formed in one mounting part 1a may be sufficient. The direction in which the protrusions 1b are formed on both the mounting portions 1a can more reliably suppress so-called solder suction, but the same effect can be obtained even with one of the mounting portions 1a.
For example, the shape of the electrode 4 of the surface mount component 3 installed in the mounting portion 1a may be different between one and the other. This embodiment can be used, for example, when one electrode 4 has a shape that is easy to absorb solder but the other electrode 4 has a shape that hardly absorbs solder.

  In the present embodiment, the cream solder layer 7 is formed so as to spread over the entire upper surface of the land 1. However, the present invention is not limited to this. For example, the cream solder layer 7 may be partially formed on the upper surface of the land 1. Moreover, since the soldering may be performed manually using a soldering iron instead of the reflow method, the cream solder layer 7 may not be formed.

  In the present embodiment, the mounting portion 1a used for mounting the surface mounting component 3 in which the electrodes 4 are formed on the two opposing surfaces is described as an example. However, the present invention is not limited to this. . For example, the surface mounting component 3 in which the electrode 4 is formed only on one surface side may be used.

  Further, when the protruding portion 1b is formed, the limited area of the printed circuit board 100 is divided by the protruding portion 1b, and there is a possibility of interference with surrounding parts, lands, pattern wirings, and the like. Therefore, the protrusion 1b may be formed so as not to interfere with surrounding parts, lands, pattern wirings, and the like. For example, when the protrusion 1b is formed on the second edge T2, if it interferes with surrounding parts, lands, pattern wiring, etc., as described in the following first to third modifications, as appropriate, The formation position of the protrusion 1b may be changed.

[Modification 1]
FIG. 5 shows a modification 1 (land 10) of the land 1 of the printed circuit board 100 according to the present embodiment. As shown in FIG. 5, the protrusions 1b do not have to be formed at equal intervals on the second edge T2. That is, as shown in FIG. 5, when the distance between the protrusion 1b on the third edge T3 side and the protrusion 1b on the fourth edge T4 side is B, the protrusion on the third edge T3 side. The interval between the portion 1b and the third edge T3 may be C, and the interval between the protrusion 1b on the fourth edge T4 side and the fourth edge T4 may be A. Note that the values of the intervals A, B, and C are all different values. Even in the land 10 of the first modification, it is possible to obtain the same effect as the printed circuit board 100 according to the present embodiment.

[Modification 2]
FIG. 6 is a modification 2 (land 11) of the land 1 of the printed circuit board 100 according to the present embodiment. In the present embodiment, the two protruding portions 1b are formed at the intermediate portion of the second edge T2 of the mounting portion 1a. However, as shown in FIG. 6, the protruding portion 1b is connected to the mounting portion 1a. You may form in the both ends of 2nd edge T2 corresponding to one of 4 sides, respectively. Even in the land 11 of the second modification, the same effect as that of the printed circuit board 100 according to the present embodiment can be obtained.

[Modification 3]
FIG. 7 is a third modification (land 12) of the land 1 of the printed circuit board 100 according to the present embodiment. In the present embodiment, the two protrusions 1b are formed on the second edge T2 of the mounting part 1a. However, as shown in FIG. 7, one protrusion 1b is connected to the third edge T3. The other protrusion 1b may be formed on the fourth edge T4. Even in the land 12 of the third modification, the same effect as that of the printed circuit board 100 according to the present embodiment can be obtained.

[Modification 4]
In addition, you may combine suitably the land 1 of the printed circuit board 100 which concerns on this Embodiment, and what was demonstrated in the modifications 1-3. FIG. 8 shows a modified example 4 of the land of the printed circuit board 100 according to the present embodiment. As shown in FIG. 8, for example, the land 1 of the printed circuit board 100 according to the present embodiment and the land 11 of the modification 2 can be combined.
Since land 1 of modification 2 has protrusions 1b formed at both ends of first edge portion T1, protrusions of land 1 of printed circuit board 100 according to the present embodiment are inserted between the protrusions 1b. By disposing the portion 1b, so-called solder sucking can be suppressed and high-density mounting of the surface-mounted component 3 can be realized.

  1 land, 1a mounting portion, 1b protrusion, 3 surface mount component, 4 electrode, 5 solder fillet portion, 7 cream solder layer, 10, 11, 12 lands, 100 printed circuit board, T1 first edge, T2 second Edge, T3 third edge, T4 fourth edge.

Claims (5)

In a printed circuit board having lands to which the first surface mount component and the second surface mount component are soldered,
The land is
A first mounting portion which one electrode of the first surface mount component is mounted,
A second mounting portion on which the other electrode of the first surface-mounted component is placed;
A third mounting portion on which one electrode of the second surface-mounted component is placed;
A fourth mounting portion on which the other electrode of the second surface-mounted component is placed;
A first protrusion extending from an edge of the first mounting portion ;
A second protrusion extending from the second mounting portion;
A third protrusion extending from the third mounting portion;
Possess a fourth protrusion extending from the edge of the fourth mounting portion,
The first mounting portion, the second mounting portion, the third mounting portion, and the fourth mounting portion are the first mounting portion, the second mounting portion, the third mounting portion, and Provided in the first direction in the order of the fourth mounting portion,
The second mounting part has a first opposing edge which is an edge provided on the third mounting part side, and the third mounting part is on the second mounting part side. A second opposing edge that is an edge provided;
The second protrusion extends from the first opposite edge toward the second opposite edge, and the third protrusion extends from the second opposite edge to the first opposite edge. Extending towards the opposite edge,
The second protrusion and the third protrusion are provided side by side in a second direction perpendicular to the first direction and parallel to the substrate surface on which the land is formed. A printed circuit board characterized by that. The second protrusion is formed on one end of the first opposing edge and the other end of the first opposing edge, respectively.
The printed circuit board according to claim 1. The second protrusion is formed at one end of the first opposing edge and the other end of the first opposing edge,
The third protrusion is formed at the second protrusion formed at one end of the first counter edge and the other end of the first counter edge. Provided between the second protrusions
The printed circuit board according to claim 1. Each of the first mounting portion , the second mounting portion, the third mounting portion, and the fourth mounting portion is formed in a rectangular shape having four sides,
The first protrusion is formed to extend to a side away from the first mounting portion ,
The fourth protrusions, the fourth printed circuit board according to any one of claims 1-3, characterized in that it is formed so as to extend on the side away from the mounting portion of the. The printed circuit board according to any one of claims 1 to 4 , wherein a lead-free cream solder layer is formed on the land.

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