Manufacturing methods for printed circuit boards and mounted products

Abstract

A printed substrate (10) used in the mounting of a heat-dissipation member (12) comprises: a first pad (16); a second pad (18) connected to a portion of the periphery of the first pad (16); and a solder paste (20) coated on the second pad (18). The solder paste (20) has a protruding part (22) that protrudes from the second pad (18) towards the first pad (16) through the connected portion of the first pad (16) and the second pad (18). The protruding part (22) extends to the inside of a terminal arrangement region (16AR) of the first pad (16).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a printed circuit board and mounted components.

Background Art

[0002] Electronic components that require relatively large driving power may be mounted on a printed circuit board. In this case, a heat dissipation member may be mounted on the printed circuit board in order to suppress heat generation due to power consumption of the electronic component. When mounting a heat dissipation member or the like on a printed circuit board, generally, solder is used.

[0003] JP-A-2014-212276 discloses a printed circuit board in which a solder paste is divided into a plurality of sections and applied to pads. The solder paste is divided into a plurality of sections by dams of a grid-like solder resist provided on the pads of the printed circuit board. The dams of the solder resist act as escape paths for voids generated in the molten solder, which is the molten solder paste. Therefore, voids generated in the molten solder are reduced.

Summary of the Invention

[0004] However, when the solder paste is divided into a plurality of sections, the mounting area of the heat dissipation member mounted on the printed circuit board becomes smaller and the heat dissipation performance is reduced compared to the case where the solder paste is not divided. Therefore, suppressing voids without reducing the heat dissipation performance has been cited as an issue.

[0005] An object of the present invention is to solve the above-described problems.

[0006] A first aspect of the present invention is a printed circuit board used for mounting a heat dissipation member, comprising: a first pad for mounting the heat dissipation member; a second pad disposed around the first pad and connected to a part of the periphery of the first pad; and a solder paste applied on the second pad, wherein the solder paste has a projection that protrudes from the second pad to the first pad via the connecting portion between the first pad and the second pad, and the projection extends to the inside of the terminal arrangement area of ​​the first pad, which is the area where the terminals of the heat dissipation member are arranged.

[0007] A second aspect of the present invention is a method for manufacturing a mounted product in which a heat dissipation member is mounted on a printed circuit board, comprising a melting step of melting solder paste applied to the printed circuit board, wherein the printed circuit board comprises a first pad, a second pad connected to a part of the periphery of the first pad, and the solder paste applied on the second pad, the solder paste having a protruding portion that protrudes from the first pad through the connecting portion between the first pad and the second pad, the protruding portion extending to the inside of the terminal arrangement area of ​​the first pad which is the area in which the terminals of the heat dissipation member are arranged, and in the melting step, the molten solder, which is the molten solder paste, is moved from the second pad to the terminal arrangement area via the protruding portion by the wetting force of the molten solder.

[0008] According to an aspect of the present invention, voids can be suppressed without reducing heat dissipation performance. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a top view showing a printed circuit board according to an embodiment. [Figure 2] Figure 2 is a cross-sectional view taken along the line II-II in Figure 1. [Figure 3] Figure 3 is a flowchart showing the manufacturing method of the mounted product. [Figure 4] Figure 4 is a top view showing the flow of molten solder. [Figure 5] Figure 5 is a cross-sectional view taken along the VV line in Figure 4. [Figure 6] Figure 6 is a top view showing a printed circuit board according to Modification 1. [Figure 7] Figure 7 is a top view showing a printed circuit board according to Modification 2. [Figure 8] Figure 8 is a top view showing a printed circuit board according to Modification 3. [Modes for carrying out the invention]

[0010] [Embodiment] Figure 1 is a top view showing a printed circuit board 10 according to an embodiment. Figure 2 is a cross-sectional view taken along the line II-II in Figure 1. The printed circuit board 10 is a printed wiring board without the heat dissipation member 12 mounted on it. The printed circuit board 10 is used for mounting the heat dissipation member 12 (Figure 2). The printed circuit board 10 has a substrate 14, a first pad 16, a second pad 18, and solder paste 20.

[0011] The first pad 16 is a metal foil for mounting the heat dissipation member 12. The first pad 16 has a terminal placement area 16AR. The terminal placement area 16AR is the area where the terminals 12TL of the heat dissipation member 12 are placed. The terminals 12TL are the parts to be soldered and are located on the bottom surface of the heat dissipation member 12. The terminal placement area 16AR may be the same size as the terminals 12TL, or it may be larger than the terminals 12TL of the heat dissipation member 12. Figures 1 and 2 show examples where the terminal placement area 16AR is larger than the terminals 12TL of the heat dissipation member 12. In the case of Figures 1 and 2, the area of ​​the first pad 16 is approximately the same as the bottom surface of the heat dissipation member 12.

[0012] The second pad 18 is a metal foil for applying solder paste 20. No electronic components, including the heat dissipation member 12, are mounted on the second pad 18. The second pad 18 is connected to a portion of the periphery of the first pad 16. In this embodiment, the second pad 18 is connected to one side of the rectangular first pad 16. The side of the first pad 16 to which the second pad 18 is connected may be one of the long sides of the rectangular first pad 16. Also in this embodiment, the second pad 18 is rod-shaped and extends in one direction, and is arranged along the periphery of the printed circuit board 10 (substrate 14).

[0013] The solder paste 20 is applied onto the second pad 18. The solder paste 20 contains flux. The solder paste 20 is sometimes referred to as solder paste.

[0014] In this embodiment, there are multiple solder pastes 20. Some of the multiple solder pastes 20 have protrusions 22. The solder pastes 20 having protrusions 22 may be referred to as the first solder paste 20_1. The first solder paste 20_1 is placed near the connection between the first pad 16 and the second pad 18. The first solder paste 20_1 is larger in size than the solder pastes 20 that do not have protrusions 22. The solder pastes 20 that do not have protrusions 22 may be referred to as the second solder paste 20_2.

[0015] The protrusion 22 extends from the second pad 18 to the first pad 16 via the connecting portion between the first pad 16 and the second pad 18. The protrusion 22 extends inside the terminal arrangement area 16AR of the first pad 16.

[0016] Figure 3 is a flowchart showing the manufacturing method of a mounted product. The mounted product is a printed circuit board 10 on which at least a heat dissipation member 12 is mounted. The manufacturing method of the mounted product includes a coating step P1, a placement step P2, a melting step P3, and a cooling step P4.

[0017] The coating process P1 is a process of applying solder paste 20 onto the second pad 18. In the coating process P1, for example, a solder printing machine is used. The solder printing machine applies the paste-like solder supplied onto the metal mask to the second pad 18 as solder paste 20 through the holes in the metal mask using a squeegee.

[0018] The placement step P2 is the step of placing the terminals 12TL of the heat dissipation member 12 on the terminal placement area 16AR of the first pad 16. In this case, at least a portion of the protrusion 22 is placed between the terminals 12TL of the heat dissipation member 12 and the terminal placement area 16AR of the first pad 16. The surface of the protrusion 22 facing the terminal placement area 16AR is in contact with the first pad 16. At least a portion of the surface of the protrusion 22 facing the terminals 12TL is in contact with the terminals 12TL.

[0019] The melting step P3 is a step in which the solder paste 20 applied on the second pad 18 is melted. In the melting step P3, for example, a reflow apparatus is used. The reflow apparatus heats the solder paste 20 to a predetermined temperature. When the solder paste 20 is heated to the predetermined temperature, it melts. The melted solder paste 20 (molten solder) wets and flows (see Figures 4 and 5). In this case, the first molten solder, which is the melted first solder paste 20_1, starts from the protrusion 22 located between the terminal arrangement area 16AR of the first pad 16 and the terminal 12TL of the heat dissipation member 12 and flows into the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12. On the other hand, the second molten solder, which is the melted second solder paste 20_2, fuses with the first molten solder by wetting and spreading, and flows into the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12. If voids form in molten solder, the voids cannot follow the flow of the molten solder and will escape from it.

[0020] Thus, in the melting step P3, due to the wetting force of the molten solder, the molten solder is moved from the second pad 18 through the protrusion 22 to the terminal arrangement region 16AR of the first pad 16. Thereby, even if the area of the terminal arrangement region 16AR is large, the undivided molten solder can be arranged in the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12. In addition to this, voids in the molten solder arranged in the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12 can be reduced.

[0021] The cooling step P4 is a step of cooling the molten solder arranged in the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12. In the cooling step P4, for example, a reflow device is used. The reflow device cools the molten solder to a predetermined cooling temperature. By cooling, the molten solder hardens and becomes hardened solder.

[0022] [Modified Example] The above embodiment may be modified as follows. In the following, descriptions overlapping with the above embodiment will be omitted as appropriate. Also, in the following description, the same reference numerals are used for elements equivalent to the elements described in the above embodiment.

[0023] (Modified Example 1) FIG. 6 is a top view showing a printed circuit board 10 according to Modified Example 1. In the printed circuit board 10 according to this modified example, the shape of the second pad 18 is different from that of the above embodiment.

[0024] In the case of this modified example, the second pad 18 includes a central portion 18PT1 and two L-shaped portions 18PT2. The central portion 18PT1 is connected to one of the long sides of the rectangular first pad 16. The two L-shaped portions 18PT2 are arranged symmetrically with respect to a virtual line passing through the center of the central portion 18PT1. Each L-shaped portion 18PT2 has a portion extending along the short side of the rectangular first pad 16 and a gap GP between it and the first pad 16.

[0025] In this modified example, the first solder paste 20_1 is placed in the central part 18PT1 of the second pad 18. The second solder paste 20_2 is placed in one of the two L-shaped parts 18PT2 of the second pad 18.

[0026] In this modified example, during the melting process P3, the first molten solder, which is the molten first solder paste 20_1, flows into the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12, starting from the protruding portion 22. The second molten solder, which is the molten second solder paste 20_2, fuses with the first molten solder by wetting and spreading, and flows into the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12 from the L-shaped portion 18PT2 via the central portion 18PT1.

[0027] Thus, even in this modified example, during the melting process P3, the molten solder moves from the second pad 18 to the terminal placement area 16AR of the first pad 16 via the protrusion 22 due to the wetting force of the molten solder. Therefore, the same effects as in the embodiment can be obtained in this modified example as well.

[0028] (Modification 2) Figure 7 is a top view showing the printed circuit board 10 according to Modification 2. In this modified printed circuit board 10, the shape of the second pad 18 differs from that of the above embodiment.

[0029] In this modified example, the second pad 18 is formed in a "T" shape. The second pad 18 includes a base portion 18PT3 and a projection end portion 18PT4. The base portion 18PT3 is a portion that extends along the long side of the rectangular first pad 16 and is connected to one of the long sides of the first pad 16. The projection end portion 18PT4 protrudes from the portion of the base portion 18PT3 opposite to the connection portion of the base portion 18PT3 that is connected to the first pad 16.

[0030] In this modified example, the first solder paste 20_1 is placed on the base portion 18PT3. The second solder paste 20_2 is placed on the protruding end portion 18PT4 and on both ends of the base portion 18PT3. The second solder paste 20_2 is placed so as to surround the first solder paste 20_1.

[0031] In this modified example, during the melting process P3, the first molten solder, which is the molten first solder paste 20_1, flows into the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12, starting from the protruding portion 22. The second molten solder, which is the molten second solder paste 20_2, fuses with the first molten solder by wetting and spreading, and flows into the gap between the first pad 16 and the terminal 12TL of the heat dissipation member 12 from both ends of the protruding end portion 18PT4 and the base portion 18PT3.

[0032] Thus, even in this modified example, during the melting process P3, the molten solder moves from the second pad 18 to the terminal placement area 16AR of the first pad 16 via the protrusion 22 due to the wetting force of the molten solder. Therefore, the same effects as in the embodiment can be obtained in this modified example as well.

[0033] (Variation 3) Figure 8 is a top view showing the printed circuit board 10 according to Modification 3. In the printed circuit board 10 according to this modification, the size and shape of the solder paste 20 differ from those of the above embodiment.

[0034] In this modified example, there is one solder paste 20. Preferably, the application area of ​​this one solder paste 20 is the same as or close to the area of ​​the terminal placement area 16AR of the first pad 16.

[0035] Furthermore, if there are multiple solder pastes 20, as in Embodiment, Modification 1, or Modification 2, it is preferable that the total application area of ​​the multiple solder pastes 20 is the same as or close to the area of ​​the terminal arrangement area 16AR of the first pad 16.

[0036] The inventions that can be understood from the above embodiments and modifications are described below.

[0037] (1) The present invention relates to a printed circuit board (10) used for mounting a heat dissipation member (12), comprising: a first pad (16) for mounting the heat dissipation member; a second pad (18) arranged around the first pad and connected to a part of the periphery of the first pad; and a solder paste (20) applied on the second pad, wherein the solder paste has a protrusion (22) that protrudes from the second pad to the first pad via the connecting portion between the first pad and the second pad, and the protrusion extends to the inside of the terminal arrangement region (16AR) of the first pad, which is the region where the terminals (12TL) of the heat dissipation member are arranged.

[0038] In the printed circuit board of the present invention, the wetting force of the molten solder paste allows the molten solder to be moved from the second pad to the terminal placement area of ​​the first pad, starting from the protruding portion. Furthermore, if voids occur in the molten solder, the voids cannot follow the movement of the molten solder and will escape from the molten solder. Therefore, even if the area of ​​the terminal placement area is large, the molten solder can be placed between the terminal placement area and the terminals of the heat dissipation member in an undivided state and with reduced voids. Thus, the printed circuit board of the present invention can suppress voids without reducing heat dissipation performance.

[0039] (2) The present invention relates to a printed circuit board, wherein a portion of the second pad may be arranged along the periphery of the printed circuit board. This makes it possible to arrange the second pad while ensuring the wiring pattern.

[0040] (3) The present invention relates to a printed circuit board, wherein the second pad may be a rod-shaped object extending in one direction. This allows the second pad to be positioned along the periphery of the printed circuit board. As a result, it is easier to position the second pad while ensuring the wiring pattern.

[0041] (4) The present invention relates to a printed circuit board, wherein the second pad may include an L-shaped portion. This allows the second pad to be placed at the corner of the printed circuit board. As a result, it is easier to place the second pad while ensuring the wiring pattern is maintained.

[0042] (5) The present invention relates to a method for manufacturing a mounted product in which a heat dissipation member is mounted on a printed circuit board, comprising a melting step (P3) of melting solder paste applied to the printed circuit board, wherein the printed circuit board comprises a first pad, a second pad connected to a part of the periphery of the first pad, and the solder paste applied on the second pad, wherein the solder paste has a protruding portion that protrudes from the first pad through the connecting portion between the first pad and the second pad, the protruding portion extends to the inside of the terminal arrangement area of ​​the first pad which is the area in which the terminals of the heat dissipation member are arranged, and in the melting step, the molten solder is moved from the second pad to the terminal arrangement area via the protruding portion by the wetting force of the molten solder paste.

[0043] As a result, even if the area of ​​the terminal placement region is large, molten solder can be placed between the terminal placement region and the terminals of the heat dissipation member in a non-divided state. Furthermore, voids that form in the molten solder can be removed from the molten solder without following the movement of the molten solder. Thus, according to the manufacturing method of the mounted product of the present invention, voids can be suppressed without reducing the heat dissipation performance.

[0044] (6) The present invention is a method for manufacturing a mounted product, further comprising a placement step (P2) of placing the terminals of the heat dissipation member on the terminal placement area before the melting step, wherein the surface of the protrusion facing the terminals of the heat dissipation member may be in contact with the terminals of the heat dissipation member. This makes it easier for the molten solder to move through the gap between the terminals of the heat dissipation member and the first pad due to the surface tension of the molten solder. Therefore, the efficiency of movement of the molten solder between the terminals of the heat dissipation member and the first pad can be increased. [Explanation of symbols]

[0045] 10…Printed circuit board 12…Heat dissipation component 12TL... Terminals 14... Circuit board 16...First pad 16AR...Terminal placement area 18…Second pad 20…Solder paste 20_1…First solder paste 20_2…Second solder paste 22...Protruding part

Claims

1. A printed circuit board (10) used for mounting a heat dissipation component (12), A first pad (16) for mounting the heat dissipation member, A second pad (18) is positioned around the first pad and connected to a portion of the periphery of the first pad, The solder paste (20) applied to the second pad, Equipped with, The solder paste has a protruding portion (22) that extends from the second pad to the first pad via the connecting portion between the first pad and the second pad, The protruding portion extends to the inside of the terminal arrangement area (16AR) of the first pad, which is the area where the terminals (12TL) of the heat dissipation member are arranged, in a printed circuit board.

2. A printed circuit board according to claim 1, A printed circuit board in which a portion of the second pad is arranged along the periphery of the printed circuit board.

3. A printed circuit board according to claim 1 or 2, The second pad is a rod-shaped printed circuit board extending in one direction.

4. A printed circuit board according to claim 1 or 2, The second pad is a printed circuit board including an L-shaped portion.

5. A method for manufacturing a mounted product in which a heat dissipation component is mounted on a printed circuit board, The process includes a melting step (P3) for melting the solder paste applied to the printed circuit board, The printed circuit board comprises a first pad, a second pad connected to a part of the periphery of the first pad, and the solder paste applied on the second pad, wherein the solder paste has a projection that protrudes from the first pad through the connecting portion between the first pad and the second pad, and the projection extends to the inside of the terminal arrangement area of ​​the first pad, which is the area where the terminals of the heat dissipation member are arranged. A method for manufacturing a mounted product, wherein in the melting step, the molten solder paste is moved from the second pad to the terminal placement area via the protrusion by the wetting force of the molten solder.

6. A method for manufacturing a mounted product according to claim 5, Prior to the melting step, the process further includes a placement step (P2) of placing the terminals of the heat dissipation member on the terminal placement area, A method for manufacturing a mounted product, wherein the surface of the protrusion facing the terminal of the heat dissipation member contacts the terminal of the heat dissipation member.

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