Printed circuit board

Abstract

To provide a technique of suppressing the generation of a solder bridge in a jet type soldering step.SOLUTION: A substrate main body 10 of this printed wiring board 1 includes: a plurality of lead lands 30 extended from each side of a QFPIC 20; and intermediate soldering leading lands 41 and 42 that are arranged so as to be adjacent to a corner part of the QFPIC 20. A tip end of a first side 81 of the intermediate soldering leading lands 41 and 42 is arranged onto an extension line of a straight line connecting the tip end part of front side lead lands 31 and 32 along adjacent sides 21 and 22. A tip end of a second side 82 of the intermediate soldering leading lands 41 and 42 is arranged onto the extension line of the straight line connecting the tip end part of rear side lead lands 33 and 34 along adjacent rear sides 23 and 24. Thus, by returning from the intermediate soldering leading lands 41 and 42, the generation of the soldering bridge in the lead land 30 can be suppressed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0006] , , With the side that first approaches the nozzle of the jet soldering system during soldering being considered the front, the movement direction of the circuit board body on which the QFPIC is attached is the front-to-back direction, and the direction perpendicular to the front-to-back direction is the left-to-right direction. , ,

[0001] The present invention relates to a printed wiring board for mounting a QFPIC on its surface.

Background Art

[0002] Conventionally, a technique for mounting a quad flat package IC (QFPIC) on the surface of a printed wiring board by soldering has been known. As a soldering method for a printed wiring board, for example, a jet (flow) soldering method is used. The conventional jet soldering method for QFPIC is described in, for example, Patent Document 1. A QFPIC has a square shape, and a plurality of lead pins are provided on its four sides at a fine pitch. Therefore, when soldering is performed by the jet soldering method, there is a risk of solder bridging.

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, a solder pull-off land is provided at the corner of the QFPIC to attract excess solder to the solder pull-off land and suppress the accumulation of excess solder around the lead pins. However, there is a need for a technique to further suppress solder bridging.

[0005] An object of the present invention is to provide a technique for suppressing the occurrence of solder bridging when soldering a QFPIC to a printed wiring board using a jet soldering method.

Means for Solving the Problems

[0007] The second invention of this application is a printed circuit board according to the first invention, wherein a resist is placed between the intermediate soldering land and the adjacent lead land, and the upper end of the resist is positioned above the upper end surfaces of the intermediate soldering land and the lead land.

[0008] The third invention of this application is a printed circuit board according to the first or second invention, wherein the intermediate solder pad has two regions spaced apart in the front-to-back direction.

[0009] The fourth invention of this application is a printed circuit board according to the third invention, wherein a resist is placed between the two regions of the intermediate soldering land, and the upper end of the resist is positioned above the upper end surfaces of the intermediate soldering land and the lead land.

[0015] This application 5 The invention is, 1 Invention or the4 A printed circuit board according to any one of the inventions, wherein a resist is placed between the plurality of regions of the final tail soldering land, and the upper end of the resist is positioned above the upper end surface of the final tail soldering land and the lead land. [Effects of the Invention]

[0016] The first invention of this application 5 According to the invention, it is possible to suppress the backflow of solder from the intermediate soldering land to the adjacent lead land. Furthermore, it can suppress the backflow of solder from the final soldering land to the adjacent lead land. Therefore, it is possible to suppress the occurrence of solder bridges in the lead pads.

[0017] In particular, according to the second to fourth inventions of this application, the backflow of solder from the intermediate soldering land to the adjacent lead land can be further suppressed. Therefore, the occurrence of solder bridges in the lead land can be further suppressed. [Brief explanation of the drawing]

[0019] [Figure 1] This is a top view of a printed circuit board according to the first embodiment. [Figure 2] This is a partial top view of the double resist portion of the printed circuit board according to the first embodiment, with the illustration omitted. [Figure 3] This is a partial top view of a printed circuit board according to the first embodiment. [Figure 4] A partial cross-sectional view of a printed circuit board according to the first embodiment. [Figure 5] This is a top view of a portion of the printed circuit board used for comparison. [Figure 6] This is a partial top view of a printed circuit board with the double resist portion of a modified example omitted from illustration. [Figure 7] This is a partial top view of a printed circuit board relating to one modification. [Modes for carrying out the invention]

[0020] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. In the present application, among the directions in which the printed wiring board extends, the moving direction of the board during soldering is defined as the front-back direction, and the side closer to the nozzle of the jet-type solder is defined as the front side, and the shape and positional relationship of each part will be described. Also, the direction perpendicular to the front-back direction is referred to as the left-right direction. Further, among the printed wiring boards, the surface on which the QFPIC is mounted is defined as the upper surface (top surface), and the opposite surface is defined as the lower surface (bottom surface). However, this definition of direction is not intended to limit the orientation of the printed board during the manufacture and use of the present invention. Also, the up-down direction in the drawings is not intended to limit the orientation of the printed wiring board according to the present invention during manufacture and use.

[0021] <1. First Embodiment> <1-1. Configuration of Printed Wiring Board> The configuration of the printed wiring board 1 according to the first embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a plan view of the printed wiring board 1 according to the first embodiment of the present invention. FIGS. 2 and 3 are partial plan views of the printed wiring board 1. In FIG. 2, the display of the double resist portion 60 is omitted. Also, in FIG. 3, although it is not a cross section, for ease of understanding, the double resist portion 60 is hatched. FIG. 4 is a partial cross-sectional view of the printed wiring board 1.

[0022] As shown in FIG. 1, the printed wiring board 1 includes a board body 10 and a plurality of electronic elements mounted on the upper surface of the board body 10. The printed wiring board 1 includes at least the QFPIC 20 as an electronic element mounted on the board body 10.

[0023] The printed wiring board 1 of the present embodiment includes two circuit regions 100 including the QFPIC 20. At least one QFPIC 20 is included in one circuit region 100. The same pattern of circuits is formed in each of the two circuit regions 100. Note that the number of circuit regions 100 included in one printed wiring board 1 may be one, or may be three or more.

[0024] As shown in FIG. 2, the printed wiring board 1 has a board body 10 and a QFP IC 20 mounted on the upper surface (top surface) of the board body 10. On the upper surface of the board body 10, a plurality of lead lands 30, two intermediate solder extraction lands 41, 42, a final tail solder extraction land 50, and a double resist portion 60 are provided.

[0025] The lead lands 30, the intermediate solder extraction lands 41, 42, and the final tail solder extraction land 50 are copper foil regions exposed on the upper surface of the board body 10. The lead lands 30 are electrically connected to other parts such as electrodes through a pattern covered with solder resist. On the other hand, the intermediate solder extraction lands 41, 42 and the final tail solder extraction land 50 are not electrically connected to other parts.

[0026] This printed wiring board 1 connects a plurality of lead pins 200 of the QFP IC 20 and a plurality of lead lands 30 by jet (flow) soldering. At this time, by moving the printed wiring board 1 relative to the fixed solder discharge port, the solder is brought into contact with the surface of the printed wiring board 1 to perform soldering. When performing soldering on this printed wiring board 1, the printed wiring board 1 is moved forward in the front-rear direction.

[0027] The board body 10 is a plate-like member extending in the front-rear direction and the left-right direction. For the board body 10, for example, a glass polyimide board, a fluorine board, a glass PPO board, etc. are used.

[0028] The QFP IC 20 is a surface-mount type IC package called a quad flat package IC (QFP IC). The QFP IC 20 has a rectangular outer shape, and a plurality of lead pins 200 protrude from all four sides. Each lead pin 200 is inserted into a through hole provided in the corresponding lead land 30.

[0029] The QFPIC20 is mounted on the upper surface of the main board 10. When viewed from above, the QFPIC20 is a roughly square-shaped electronic element with two sides extending in a first direction and two sides extending in a second direction. The first and second directions are orthogonal to each other. In addition, the first and second directions are tilted at approximately 45° with respect to the front-to-back direction.

[0030] The QFPIC20 has four corners. The four corners of the QFPIC20 include a front corner 91, a rear corner 92, a first lateral corner 93, and a second lateral corner 94. The front corner 91 and the rear corner 92 face each other in the front-rear direction. The first lateral corner 93 and the second lateral corner 94 face each other in the left-right direction.

[0031] QFPIC20 has four sides. The four sides of QFPIC include a first front side 21, a second front side 22, a first rear side 23, and a second rear side 24. The first front side 21 connects the front corner 91 and the first lateral corner 93. The second front side 22 connects the front corner 91 and the second lateral corner 94. The first rear side 23 connects the first lateral corner 93 and the rear corner 92. The second rear side 24 connects the second lateral corner 94 and the rear corner 92.

[0032] Hereafter, the direction in which the first front edge 21 and the second rear edge 24 extend will be referred to as the first direction. The direction in which the second front edge 22 and the first rear edge 23 extend will be referred to as the second direction. The second direction is perpendicular to the first direction. The first and second directions are inclined at approximately 45° with respect to the front-rear direction and the left-right direction. Furthermore, in the following, for the first front edge 21 extending in the first direction, the side with the front corner 91 will be referred to as "one side of the first direction," and the side with the first lateral corner 93 will be referred to as "the other side of the first direction." For the second front edge 22 extending in the second direction, the side with the front corner 91 will be referred to as "one side of the second direction," and the side with the second lateral corner 94 will be referred to as "the other side of the second direction."

[0033] Through-holes are provided in multiple lead lands 30, and corresponding lead pins 200 are inserted into them. By soldering to the lead lands 30, the lead lands 30 and the lead pins 200 are electrically connected. The lead lands 30 are rectangular in shape when viewed from above, and their longitudinal direction extends approximately perpendicular to the sides of the QFPIC 20. In other words, the lead lands 30 extend approximately perpendicular to the sides of the QFPIC 20.

[0034] The multiple lead lands 30 include front lead lands 31 and 32 arranged along the front edges 21 and 22, and rear lead lands 33 and 34 arranged along the rear edges 23 and 24. More specifically, the multiple lead lands 30 arranged along the first front edge 21 are each referred to as the first front lead land 31. The multiple lead lands 30 arranged along the second front edge 22 are each referred to as the second front lead land 32. The multiple lead lands 30 arranged along the first rear edge 23 are each referred to as the first rear lead land 33. In addition, the multiple lead lands 30 arranged along the second rear edge 24 are each referred to as the second rear lead land 34.

[0035] Multiple first front lead lands 31 are arranged along the first front edge 21 at intervals in the first direction. Each first front lead land 31 extends from the first front edge 21 to one side in the second direction. That is, each first front lead land 31 extends approximately perpendicular to the first front edge 21. Hereafter, the end of the first front lead land 31 on one side in the second direction will be referred to as the "tip portion" of the first front lead land 31.

[0036] Multiple second front lead lands 32 are arranged along the second front edge 22, spaced apart in the second direction. Each second front lead land 32 extends from the second front edge 22 to one side in the first direction. That is, each second front lead land 32 extends approximately perpendicular to the second front edge 22. Hereafter, the end of the second front lead land 32 on one side in the first direction will be referred to as the "tip portion" of the second front lead land 32.

[0037] Multiple first rear lead lands 33 are arranged along the first rear edge 23, spaced apart in the second direction. Each first rear lead land 33 extends from the first rear edge 23 to the other side in the first direction. That is, each first rear lead land 33 extends approximately perpendicular to the first rear edge 23. Hereinafter, the end of the first rear lead land 33 on the other side in the first direction will be referred to as the "tip portion" of the first rear lead land 33.

[0038] Multiple second rear lead lands 34 are arranged along the second rear edge 24 at intervals in the first direction. Each second rear lead land 34 extends from the second rear edge 24 to the other side in the second direction. That is, each second rear lead land 34 extends approximately perpendicular to the second rear edge 24. Hereinafter, the end of the second rear lead land 34 on the other side in the second direction will be referred to as the "tip portion" of the second rear lead land 34.

[0039] The two intermediate soldering lands 41 and 42 include a first intermediate soldering land 41 positioned adjacent to the first lateral corner portion 93 and a second intermediate soldering land 42 positioned adjacent to the second lateral corner portion 94. Each of the intermediate soldering lands 41 and 42 is substantially square in shape, with two sides extending in a first direction and two sides extending in a second direction when viewed from above. Therefore, each of the intermediate soldering lands 41 and 42 has corners on the front, back, left, and right sides.

[0040] Each of the intermediate soldering lands 41 and 42 has a first side 81, a second side 82, a third side 83, a fourth side 84, and an adjacent corner 80.

[0041] The first side 81 extends from the adjacent lateral corners 93 and 94 along the adjacent front lead lands 31 and 32. The first side 81 is positioned with a gap between it and the adjacent front lead lands 31 and 32. The second side 82 extends from the adjacent lateral corners 93 and 94 along the adjacent rear lead lands 33 and 34. The second side 82 is positioned with a gap between it and the adjacent rear lead lands 33 and 34. The third side 83 is parallel to the second side 82 and connects the first side 81 and the fourth side 84. The fourth side 84 is parallel to the first side 81 and connects the second side 82 and the third side 83.

[0042] Specifically, the first side 81 of the first intermediate soldering land 41 extends from the first lateral corner portion 93 to one side in the second direction, along the first front lead land 31 on the far other side in the first direction. Hereinafter, the end of the first side 81 of the first intermediate soldering land 41 on one side in the second direction will be referred to as the tip of the first side 81 of the first intermediate soldering land 41.

[0043] The second side 82 of the first intermediate soldering land 41 extends from the first lateral corner portion 93 to the other side in the first direction, along the first rear lead land 33 on the far side in the second direction. Hereinafter, the end of the second side 82 of the first intermediate soldering land 41 on the other side in the first direction will be referred to as the tip of the second side 82 of the first intermediate soldering land 41.

[0044] The first side 81 of the second intermediate soldering land 42 extends from the second lateral corner portion 94 to one side in the first direction, along the second front lead land 32 on the far other side in the second direction. Hereinafter, the end of the first side 81 of the second intermediate soldering land 42 on one side in the first direction will be referred to as the tip of the first side 81 of the second intermediate soldering land 42.

[0045] The second side 82 of the second intermediate soldering land 42 extends from the second lateral corner portion 94 to the other side in the second direction, along the second rear lead land 34 on the side furthest to the first direction. Hereinafter, the end of the second side 82 of the second intermediate soldering land 42 on the other side in the second direction will be referred to as the tip of the second side 82 of the second intermediate soldering land 42.

[0046] The adjacent corner portion 80 is the corner portion connecting the first side 81 and the second side 82. The adjacent corner portion 80 is located near the lateral corner portions 93 and 94 of the QFPIC 20. In this embodiment, the adjacent corner portion 80 slightly overlaps the lateral corner portions 93 and 94 in the vertical direction, but it may also be located slightly outside the lateral corner portions 93 and 94. Specifically, the adjacent corner portion 80 of the first intermediate soldering land 41 is located near the first lateral corner portion 93. Also, the adjacent corner portion 80 of the second intermediate soldering land 42 is located near the second lateral corner portion 94.

[0047] The first side 81 of the first intermediate soldering land 41 is positioned on the extension of a straight line connecting the tips of multiple first front lead lands 31 along the adjacent first front side 21. In addition, the third side 83 of the first intermediate soldering land 41, which is connected to the tip of the first side 81, is positioned on the extension of a straight line connecting the tips of multiple first front lead lands 31 along the first front side 21.

[0048] The second side 82 of the first intermediate soldering land 41 is positioned on the extension of a straight line connecting the tips of multiple first rear lead lands 33 along the adjacent first rear side 23. In addition, the fourth side 84 of the first intermediate soldering land 41, which is connected to the tip of the second side 82, is positioned on the extension of a straight line connecting the tips of multiple first rear lead lands 33 along the first rear side 23.

[0049] The first side 81 of the second intermediate soldering land 42 is positioned on the extension of a straight line connecting the tips of multiple second front lead lands 32 along the adjacent second front side 22. In addition, the third side 83 of the first intermediate soldering land 41, which is connected to the tip of the first side 81, is positioned on the extension of a straight line connecting the tips of multiple second front lead lands 32 along the second front side 22.

[0050] The second side 82 of the second intermediate soldering land 42 is positioned on the extension of a straight line connecting the tips of multiple second rear lead lands 34 along the adjacent second rear side 24. In addition, the fourth side 84 of the second intermediate soldering land 42, which is connected to the tip of the second side 82, is positioned on the extension of a straight line connecting the tips of multiple second rear lead lands 34 along the second rear side 24.

[0051] The final tail soldering land 50 is positioned adjacent to the rear corner 92. That is, the final tail soldering land 50 is positioned adjacent to the first rear lead land 33, which is located furthest to the other side in the second direction, and the second rear lead land 34, which is also located furthest to the other side in the first direction. The final tail soldering land 50 has a fifth side 501 that extends in the first direction along the first rear lead land 33, which is located furthest to the other side in the second direction, and a sixth side 502 that extends in the second direction along the second rear lead land 34, which is located furthest to the other side in the first direction.

[0052] The final tail soldering land 50 has multiple regions 51 to 56 that are spaced apart from each other. When the area of ​​the final tail soldering land 50 is large, the height of the solder adhering to the final tail soldering land 50 increases due to surface tension, and the amount of solder adhering to the final tail soldering land 50 tends to increase. Therefore, by dividing the final tail soldering land 50 into multiple regions 51 to 56, the height of the solder adhering in each region 51 to 56 can be reduced. This suppresses the amount of solder held in the final tail soldering land 50, preventing solder from being swept back from the final tail soldering land 50 to the adjacent first rear lead land 33 and second rear lead land 34, and suppresses the occurrence of solder bridges in the first rear lead land 33 and second rear lead land 34.

[0053] In this embodiment, the final tail soldering land 50 has six regions 51 to 56 that are spaced apart in the front-to-back and left-to-right directions. Specifically, the final tail soldering land 50 has a first front region 51, a first intermediate region 52, a first rear region 53, a second front region 54, a second intermediate region 55, and a second rear region 56.

[0054] The first front region 51, the first intermediate region 52, and the first rear region 53 are positioned to the right of the second front region 54, the second intermediate region 55, and the second rear region 56.

[0055] The first front end region 51 includes the fifth side 501. The first front end region 51 is trapezoidal, having an upper and lower base extending in the front-to-back direction. The front leg of the trapezoidal first front end region 51 is the fifth side 501, which extends in the first direction. The rear leg extends in the left-to-right direction, perpendicular to the upper and lower bases. The first front end region 51 is positioned to the right of the second front end region 54, with a gap in the left-to-right direction between them.

[0056] The first intermediate region 52 is rectangular in shape, having two sides extending in the front-to-back direction and two sides extending in the left-to-right direction. The first intermediate region 52 is positioned behind the first front end region 51 and in front of the first rear end region 53. The first front end region 51 and the first intermediate region 52 are spaced apart in the front-to-back direction. The first intermediate region 52 is also spaced apart from the second intermediate region 55 in the left-to-right direction and is positioned to the right of the second intermediate region 55.

[0057] The first rear end region 53 is rectangular in shape, having two sides extending in the front-to-back direction and two sides extending in the left-to-right direction. The first rear end region 53 is positioned behind the first intermediate region 52. The first intermediate region 52 and the first rear end region 53 are spaced apart in the front-to-back direction. The first rear end region 53 is also spaced apart from the second rear end region 56 and is positioned to the right of the second rear end region 56.

[0058] The second front end region 54 includes the sixth side 502. The second front end region 54 is trapezoidal, having an upper and lower base extending in the front-to-back direction. The front leg of the trapezoidal second front end region 54 is the sixth side 502, which extends in the second direction. The rear leg extends in the left-to-right direction, perpendicular to the upper and lower bases. The second front end region 54 is positioned to the left of the first front end region 51, with a gap between them in the left-to-right direction.

[0059] The second intermediate region 55 is rectangular in shape, having two sides extending in the front-to-back direction and two sides extending in the left-to-right direction. The second intermediate region 55 is positioned behind the second front end region 54 and in front of the second rear end region 56. The second front end region 54 and the second intermediate region 55 are spaced apart in the front-to-back direction. The second intermediate region 55 is also spaced apart from the first intermediate region 52 in the left-to-right direction and is positioned to the left of the first intermediate region 52.

[0060] The second rear end region 56 is rectangular in shape, having two sides extending in the front-to-back direction and two sides extending in the left-to-right direction. The second rear end region 56 is positioned behind the second intermediate region 55. The second intermediate region 55 and the second rear end region 56 are spaced apart in the front-to-back direction. The second rear end region 56 is also spaced apart from the first rear end region 53 in the left-to-right direction and is positioned to the left of the first rear end region 53.

[0061] Figure 4 is a partial cross-sectional view of the printed circuit board 1 near the double resist section 60. Figure 4 shows a part of the first front lead land 31, the first intermediate soldering land 41, and the first boundary section 611 of the double resist section 60, which will be described later.

[0062] As shown in Figure 4, the double resist section 60 consists of a solder resist 601 and a silk screen printing section 602 laminated on the upper surface of the substrate body 10. The solder resist 601 covers most of the upper surface of the substrate body 10, excluding exposed copper foil areas such as lands 30, 41, 42, and 50. The silk screen printing section 602 is laminated on top of the solder resist 601. Generally, the thickness of the solder resist 601 is 10 to several tens of micrometers, and the thickness of the silk screen printing section 602 is several tens of micrometers.

[0063] In the printed circuit board 1 of this embodiment, the thickness of the copper foil constituting the lead lands 30, intermediate soldering lands 41, 42, and final tail soldering land 50 is approximately 35 μm. The thickness of the solder resist 601 is approximately 5 to 10 μm, and the thickness of the silk screen printing area 602 is approximately 10 to 20 μm.

[0064] Thus, the upper end of the double resist section 60 is positioned above the upper end surfaces of the lead lands 30, intermediate soldering lands 41, 42, and final tail soldering land 50. As a result, the double resist section 60 suppresses solder movement between two adjacent locations on either side of the double resist section 60 among the lead lands 30, intermediate soldering lands 41, 42, and final tail soldering land 50. Consequently, solder is swung back from the intermediate soldering lands 41, 42 or the final tail soldering land 50 to the lead lands 30, suppressing the formation of solder bridges on the lead lands 30. The effect of the double resist section 60 on suppressing solder bridge formation in each part will be described later.

[0065] <1-2. Effect of suppressing solder bridge formation in the soldering process> Next, we will explain how the occurrence of solder bridges is suppressed during the soldering process to the printed circuit board 1. Figure 5 shows an example of a printed circuit board 1X for comparison.

[0066] The lengths of the sides of the first intermediate soldering lands 41X and the second intermediate soldering lands 42X in the printed circuit board 1X of the example in Figure 5 are twice the lengths of the sides of the first intermediate soldering lands 41 and the second intermediate soldering lands 42 in the printed circuit board 1 of this embodiment. Thus, in the printed circuit board 1X of the example in Figure 5, like conventional printed circuit boards, the sides of the intermediate soldering lands adjacent to the lead lands are longer than the length of the adjacent lead lands.

[0067] Note that the other shapes of the printed circuit board 1X in the example of Figure 5 are the same as those of the printed circuit board 1 in this embodiment, so they are denoted by the same reference numerals and their description is omitted. For this reason, the printed circuit board 1X in the example of Figure 5 differs from conventional printed circuit boards in that it has a double resist section 60 and the shape of the final tail soldering land 50.

[0068] In the soldering process of this printed circuit board 1, the printed circuit board 1 is moved forward over the solder nozzles that eject solder upwards in the solder bath, with the upper surface on which the QFPIC 20 is mounted facing vertically downwards. As a result, the solder ejected from the nozzles contacts the upper surface of the printed circuit board 1 sequentially from the front end to the rear end. Consequently, solder adheres to the first front lead land 31 and the second front lead land 32, the first intermediate soldering land 41 and the second intermediate soldering land 42, the first rear lead land 33 and the second rear lead land 34, and finally the rear soldering land 50 in that order.

[0069] At this time, the solder flow near QFPIC20 is divided into two: a first flow in which solder adheres in the order of the first front lead land 31, the first intermediate soldering land 41, the first rear lead land 33, and the final tail soldering land 50; and a second flow in which solder adheres in the order of the second front lead land 32, the second intermediate soldering land 42, the second rear lead land 34, and the final tail soldering land 50. Since the area near QFPIC20 is symmetrical, only the first flow will be described below.

[0070] Conventionally, it was believed that by applying a large amount of solder to the intermediate solder pad, excess solder adhering to the adjacent lead pad could be attracted to the intermediate solder pad, thereby suppressing solder bridging in the adjacent lead pads. For this reason, conventionally, as shown in Figure 5, the first side 81X and the second side 82X of the first intermediate solder pad pad 41X were made longer than the lengths of the adjacent first front lead pad 31 and first rear lead pad 33.

[0071] In contrast, in the printed circuit board 1 of this embodiment, the tip of the first side 81 of the first intermediate soldering land 41 (the end on one side in the second direction) is positioned on the extension of the straight line connecting the tips of the multiple first front lead lands 31 (the ends on one side in the second direction). Therefore, the length of the first side 81 of the first intermediate soldering land 41 is approximately the same as that of the first front lead lands 31. As a result, when the contact point of the ejected solder moves from the first front lead lands 31 to the first intermediate soldering land 41, the width of the solder attachment point (length in the second direction) does not suddenly expand.

[0072] Furthermore, the third side 83 of the first intermediate soldering land 41 extends from the tip of the first side 81 to the other side in the first direction, and thus extends along the extension of the straight line connecting the tips (ends on one side in the second direction) of the multiple first front lead lands 31. For this reason, even after the contact point of the ejected solder shifts from the first front lead land 31 to the first intermediate soldering land 41, the width of the solder attachment point (length in the second direction) is maintained.

[0073] In this way, since the end of the first intermediate soldering land 41 on one side in the second direction extends along the extension of the straight line connecting the tips (ends on one side in the second direction) of the multiple first front lead lands 31, the width of the solder attachment area (length in the second direction) does not change, and therefore, an unnecessarily large amount of solder does not adhere to the first intermediate soldering land 41. As a result, the occurrence of solder bridging due to the backflow of solder from the first intermediate soldering land 41 to the first front lead lands 31 can be suppressed.

[0074] Furthermore, in the printed circuit board 1 of this embodiment, the tip of the second side 82 of the first intermediate soldering land 41 (the end on the other side in the first direction) is positioned on the extension of the straight line connecting the tips of the multiple first rear lead lands 33 (the ends on the other side in the first direction). Therefore, the length of the second side 82 of the first intermediate soldering land 41 is approximately the same as the length of the first rear lead land 33. As a result, when the contact point of the ejected solder moves from the first intermediate soldering land 41 to the first rear lead land 33, the width of the solder attachment point (length in the first direction) does not suddenly shrink.

[0075] Furthermore, the fourth side 84 of the first intermediate soldering land 41 extends from the tip of the third side 83 toward one side in the second direction, and thus extends along the extension of the straight line connecting the tips (ends on the other side in the first direction) of the multiple first rear lead lands 33. Therefore, when the contact point of the ejected solder moves from the first intermediate soldering land 41 to the first rear lead land 33, the width of the solder attachment point (length in the first direction) is maintained.

[0076] In this way, since the end of the first intermediate soldering land 41 on the other side in the first direction extends along the extension of the straight line connecting the tips (ends on the other side in the first direction) of the multiple first rear lead lands 33, the width of the solder attachment area (length in the first direction) does not change, and therefore, an unnecessarily large amount of solder does not adhere to the first intermediate soldering land 41. As a result, the occurrence of solder bridging due to the backflow of solder from the first intermediate soldering land 41 to the first rear lead lands 33 can be suppressed.

[0077] Next, the solder bridge suppression effect in the double resist section 60 will be explained. As shown in Figure 3, the double resist section 60 includes an intermediate resist section 61 and a final tail resist section 62. The intermediate resist section 61 includes a first boundary section 611, a second boundary section 612, a third boundary section 613, and a fourth boundary section 614.

[0078] The first boundary portion 611 is positioned between the first side 81 of the first intermediate soldering land 41 and the adjacent lead land 30. Specifically, the first boundary portion 611 extends in a second direction between the first side 81 of the first intermediate soldering land 41 and the first front lead land 31, which is located furthest to the other side in the first direction. The first boundary portion 611 prevents solder from being swung back from the first intermediate soldering land 41 to the first front lead land 31 during the soldering process, thereby preventing the formation of solder bridges in the first front lead land 31.

[0079] The second boundary portion 612 is positioned between the second side 82 of the first intermediate soldering land 41 and the adjacent lead land 30. Specifically, the second boundary portion 612 extends in the first direction between the second side 82 of the first intermediate soldering land 41 and the first rear lead land 33, which is positioned furthest to the second direction. The second boundary portion 612 prevents solder from being swung back from the first intermediate soldering land 41 to the first rear lead land 33 during the soldering process, thereby preventing the formation of solder bridges on the first rear lead land 33.

[0080] The third boundary portion 613 is positioned between the first side 81 of the second intermediate soldering land 42 and the adjacent lead land 30. Specifically, the third boundary portion 613 extends in the first direction between the first side 81 of the second intermediate soldering land 42 and the second front lead land 32, which is located furthest to the other side in the second direction. The third boundary portion 613 prevents solder from being swung back from the second intermediate soldering land 42 to the second front lead land 32 during the soldering process, thereby preventing the formation of solder bridges in the second front lead land 32.

[0081] The fourth boundary portion 614 is positioned between the second side 82 of the second intermediate soldering land 42 and the adjacent lead land 20. Specifically, the fourth boundary portion 614 extends in the second direction between the second side 82 of the second intermediate soldering land 42 and the second rear lead land 34, which is positioned furthest to the first direction. During the soldering process, the fourth boundary portion 614 prevents solder from being swung back from the second intermediate soldering land 42 to the second rear lead land 34, thereby suppressing the formation of solder bridges in the second rear lead land 34.

[0082] The final tail resist section 62 includes a fifth boundary section 621, a sixth boundary section 622, a seventh boundary section 623, an eighth boundary section 624, a first separation section 625, a second separation section 626, and a third separation section 627.

[0083] The fifth boundary portion 621 is positioned between the fifth edge 501 of the final tail soldering land 50 and the adjacent lead land 30. Specifically, the fifth boundary portion 621 extends in the first direction between the fifth edge 501 of the first front end region 51 and the first rear lead land 33, which is located furthest to the other side in the second direction. During the soldering process, the fifth boundary portion 621 prevents solder from being swung back from the first front end region 51 to the first rear lead land 33, thereby suppressing the formation of solder bridges in the first rear lead land 33.

[0084] The sixth boundary portion 622 is positioned between the sixth edge 502 of the final tail soldering land 50 and the adjacent lead land 30. Specifically, the sixth boundary portion 622 extends in the second direction between the sixth edge 502 of the second front end region 54 and the second rear lead land 34, which is located furthest to the other side in the first direction. The sixth boundary portion 622 prevents solder from being swung back from the second front end region 54 to the second rear lead land 34 during the soldering process, thereby preventing solder bridging from occurring in the second rear lead land 34.

[0085] The seventh boundary section 623 extends along the right edge of the final tail soldering land 50. Specifically, the seventh boundary section 623 extends in the front-rear direction along the right edge of the first front region 51, the first intermediate region 52, and the first rear region 53. The eighth boundary section 624 extends along the left edge of the final tail soldering land 50. Specifically, the eighth boundary section 624 extends in the front-rear direction along the left edge of the second front region 54, the second intermediate region 55, and the second rear region 56. The seventh boundary section 623 and the eighth boundary section 624 suppress the solder adhering to the final tail soldering land 50 from spreading in the left-right direction and adhering to other electronic components, etc.

[0086] The first separation section 625 extends in the front-rear direction between the first front end region 51, the first intermediate region 52, and the first rear end region 53 and the second front end region 54, the second intermediate region 55, and the second rear end region 56. The first separation section 625 separates the first flow of solder connecting the first front lead land 31, the first intermediate soldering land 41, and the first rear lead land 33 to the first front end region 51, and the second flow of solder connecting the second front lead land 32, the second intermediate soldering land 42, and the second rear lead land 34 to the second front end region 54. This prevents an increase in the amount of solder adhering to the final tail soldering land 50 due to the momentum of the first and second flows merging. As a result, solder is returned from the final tail soldering land 50 to the first rear lead land 33 and the second rear lead land 34, suppressing the occurrence of solder bridges in the first rear lead land 33 and the second rear lead land 34.

[0087] The second separation section 626 extends in the left-right direction between the first front end region 51 and the second front end region 54 and the first intermediate region 52 and the second intermediate region 55. The third separation section 627 extends in the left-right direction between the first intermediate region 52 and the second intermediate region 55 and the first rear end region 53 and the second rear end region 56. In this way, the final tail soldering land 50 is divided in the front-rear direction, and the double resist section 60 is placed between the divided regions, thereby ensuring that the solder is interrupted at the final tail soldering land 50 where the solder jet makes final contact, and suppressing the solder from swinging back from the rearward-positioned region to the front.

[0088] <1-3. Experiments concerning intermediate soldering lands> Next, we will explain the results of an experiment comparing the solder bridge occurrence rate of the printed circuit board 1X in the example of Figure 5 and the printed circuit board 1 of this embodiment. Under the following conditions 1 to 4, jet soldering was performed on 20 printed circuit boards 1,1X for each condition. [Experimental conditions] Type of wiring board / type of solder [Condition 1] Printed circuit board 1X / eutectic solder as shown in the example in Figure 5 [Condition 2] Printed circuit board 1 of the first embodiment / eutectic solder [Condition 3] Printed circuit board 1X / RoHS solder as shown in the example in Figure 5 [Condition 4] Printed circuit board 1 / RoHS solder of the first embodiment

[0089] Experiments conducted under each condition yielded the following results regarding the number of solder bridges and the bridge occurrence rate. [Experimental Results] Number of solder bridges / Bridge occurrence rate [Condition 1] 17 / 85% [Condition 2] 3 / 15% [Condition 3] 4 / 20% [Condition 4] 0 / 0%

[0090] Thus, in the printed circuit board 1 of this embodiment, the occurrence of solder bridges is suppressed more than in the printed circuit board example in Figure 5. From these experimental results, it can be seen that the occurrence of solder bridges can be suppressed by making the side of the intermediate soldering lands 41 and 42 adjacent to the lead land 30 the same length as the lead land 30.

[0091] <2. Variant> Although exemplary embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above.

[0092] Figure 6 is a partial top view of a printed circuit board 1A according to one modification, with the double resist portion 60A omitted from the illustration. Figure 7 is a partial top view of the printed circuit board 1A of the example in Figure 6. As with Figure 3, the double resist portion 60A is hatched, although it is not a cross-section.

[0093] In the printed circuit board 1A of the example in Figure 6, the first intermediate solder pad 41A and the second intermediate solder pad 42A are arranged in a first region 401A and a second region 402, respectively, with a gap between them in the front-to-back direction. The first region 401A is a triangular region including the first side 81A and the third side 83A. The second region 402 is a triangular region including the second side 82A and the fourth side 84A.

[0094] In this way, by dividing each intermediate soldering land 41A, 42A into two regions 401A, 402A, the amount of solder held in each intermediate soldering land 41A, 42A can be suppressed, and the backflow of solder from each intermediate soldering land 41A, 42A to the adjacent lead land 30A can be further suppressed.

[0095] Furthermore, in this printed circuit board 1A, as shown in Figure 7, a double resist section 60A is positioned between the first region 401A and the second region 402A. This allows for more reliable separation of solder between the first region 401A and the second region 402A. Consequently, the amount of solder held in each intermediate soldering land 41A, 42A can be more reliably suppressed. As a result, the backflow of solder from each intermediate soldering land 41A, 42A to the adjacent lead land 30A can be further suppressed.

[0096] Furthermore, the specific device configuration for realizing each part of the printed circuit board may differ from the configuration shown in the above embodiments and modifications. Also, the elements that appear in the above embodiments and modifications may be combined as appropriate, to the extent that no inconsistencies arise. [Explanation of Symbols]

[0097] 1,1A,1X Printed Wiring Board 10 Main board 20 Lead Lands 21 1st front side 22 2nd front side 23 First rear side 24 Second rear 30,30A lead land 31 Land for the first front lead 32 Land for the second front lead 33 Land for the first rear lead 34 Land for the second rear lead 41, 41A, 41X First Intermediate Soldering Land 42, 42A, 42X Second Intermediate Soldering Land 50 Final Handa Pull Land 51 1st front end area 52 1st intermediate area 53 1st rear end area 54 2nd front end area 55 Second intermediate area 56 Second rear end area 60,60A Double Resist Section 81,81A,81X First side 82, 82A, 82X Second side 91 Front corner 92 Rear corner 93 1st side corner 94 2nd side corner 200 lead pins

Claims

1. A printed circuit board on which a QFPIC is mounted on the upper surface, The main circuit board and A QFPIC with multiple lead pins, It has, With the side that first approaches the nozzle of the jet soldering system during soldering being considered the front, the direction of movement of the circuit board body on which the QFPIC is mounted is the front-to-back direction, and the direction perpendicular to the front-to-back direction is the left-to-right direction. The aforementioned QFPIC is The front corner and rear corner facing each other in the front-rear direction, The two lateral corner portions facing each other in the left-right direction, Two front edges connecting the aforementioned front corner and the aforementioned lateral corner, Two rear edges connecting the aforementioned lateral corner and the aforementioned rear corner, It has, The aforementioned substrate body has, on its upper surface, A plurality of lead lands are arranged along each side of the QFPIC, each electrically connected to one of the lead pins, An intermediate soldering land is arranged adjacent to the aforementioned lateral corner portion, A final tail soldering land is located adjacent to the aforementioned rear corner, It has, Multiple of the aforementioned lead lands are Multiple front lead lands extending from the aforementioned front edge, Multiple rear lead lands extending from the aforementioned rear edge, Includes, The aforementioned intermediate soldering pads are, A first side extending from the aforementioned lateral corner portion along the adjacent front lead land, A second side extends from the aforementioned lateral corner portion along the adjacent rear lead land, It has, The tip of the first side is positioned on the extension of a straight line connecting the tips of a plurality of front lead lands along the adjacent front side, The tip of the second side is positioned on the extension of a straight line connecting the tips of a plurality of rear lead lands along the adjacent rear side, The aforementioned final soldering land has multiple regions that are spaced apart from each other. The aforementioned multiple regions are, The first front end region adjacent to the aforementioned rear lead land on the right side, A first intermediate region is located behind the first front end region, A first rear end region positioned behind the first intermediate region, A second front end region adjacent to the aforementioned rear lead land on the left side, A second intermediate region located behind the second front end region, A second rear end region is located behind the second intermediate region, Printed circuit boards, including those mentioned above.

2. A printed circuit board according to claim 1, A resist is placed between the aforementioned intermediate soldering land and the adjacent lead land. A printed circuit board in which the upper end of the resist is positioned above the upper end surfaces of the intermediate soldering land and the lead land.

3. A printed circuit board according to claim 1, The aforementioned intermediate solder pads are located on a printed circuit board having two regions spaced apart in the front-to-back direction.

4. A printed circuit board according to claim 3, A resist is placed between the two regions of the intermediate soldering land. A printed circuit board in which the upper end of the resist is positioned above the upper end surfaces of the intermediate soldering land and the lead land.

5. A printed circuit board according to any one of claims 1 to 4, A resist is placed between the plurality of regions of the final tail soldering land. A printed circuit board in which the upper end of the resist is positioned above the upper end surface of the final tail soldering land and the lead land.

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