Printed circuit board

Abstract

To provide a printed circuit board that can suppress the detachment of electronic components and reduce design constraints. [Solution] The printed circuit board 100 comprises a base material 1 having a first surface 1a and a second surface 1b, with a through hole H penetrating the first surface 1a and the second surface 1b; a through hole 2 having a conductive layer 2a disposed on the side of the through hole H; solder 5 supplied to the through hole 2 so as to be in contact with the conductive layer 2a; and an electronic component 3 having a lead 4 inserted into the through hole 2 into which the solder 5 is supplied. The lead 4 of the electronic component 3 includes a straight portion 10 and an intersecting portion 11. The straight portion 10 extends in the direction in which the through hole H penetrates the first surface 1a and the second surface 1b. The intersecting portion 11 is configured to intersect the straight portion 10. The lead 4 is located in the through hole 2 on the second surface 1b side of the base material 1.

Description

Technical Field

[0001] The present disclosure relates to a printed wiring board.

Background Art

[0002] As a soldering method for through-holes of a printed wiring board, there is a pin-in-paste method. In the pin-in-paste method, first, solder paste is supplied to through-holes by screen printing using a metal mask. Next, leads of an electronic component are inserted into the through-holes supplied with the solder paste. Further, the printed wiring board is heated in a reflow furnace, and the solder paste is melted to form a solder joint of the through-hole. For example, Japanese Patent Application Laid-Open No. 5-75245 describes a printed wiring board to which the pin-in-paste method is applied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the printed wiring board described in the above publication, the shape of the lead of the electronic component is a straight shape. Therefore, when a load is applied in the direction of the body of the electronic component after soldering, the lead may come out of the solder joint and the electronic component may fall off.

[0005] Also, on the surface opposite to the mounting surface of the electronic component, since the leads protrude from the through-holes, it is difficult to print solder paste on this surface. Therefore, design constraints increase.

[0006] This disclosure has been made in view of the above-mentioned problems, and its purpose is to provide a printed circuit board that can suppress the detachment of electronic components and reduce design constraints. [Means for solving the problem]

[0007] The printed circuit board of this disclosure comprises a substrate having a first surface and a second surface opposite to the first surface, with through holes penetrating the first and second surfaces; through holes having a conductive layer disposed on the side of the through holes provided in the substrate; solder supplied to the through holes so as to be in contact with the conductive layer; and an electronic component having leads inserted into the through holes from which the solder was supplied. The leads of the electronic component include a straight portion and an intersecting portion connected to the straight portion. The straight portion extends in the direction in which the through holes penetrate the first and second surfaces. The intersecting portion is configured to intersect the straight portion. The leads are housed within the through holes on the second surface of the substrate. [Effects of the Invention]

[0008] The printed circuit board of this disclosure can suppress the detachment of electronic components and reduce design constraints. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing a solder joint in a through-hole of a printed circuit board according to Embodiment 1. [Figure 2] This is a schematic cross-sectional view illustrating the solder paste printing method using a metal mask in the manufacturing method of a printed circuit board according to Embodiment 1. [Figure 3] This is a schematic cross-sectional view showing the state in which the leads of an electronic component are inserted into a through-hole in the method for manufacturing a printed circuit board according to Embodiment 1. [Figure 4] This is a schematic cross-sectional view showing the state of the solder joints of through-holes formed by the pin-in-paste soldering method in the printing circuit board manufacturing method according to Embodiment 1. [Figure 5] This is a schematic cross-sectional view showing the soldering state of surface mount components in the method for manufacturing a printed circuit board according to Embodiment 1. [Figure 6] This is a schematic cross-sectional view showing a solder joint in a through-hole of a printed circuit board according to Embodiment 2. [Figure 7] This is a schematic cross-sectional view showing a solder joint in a through-hole of a printed circuit board according to Embodiment 3. [Figure 8] This is a schematic cross-sectional view showing a solder joint in a through-hole of a modified example 1 of a printed circuit board according to Embodiment 3. [Figure 9] This is a schematic cross-sectional view showing the solder joint in a through-hole of a modified example 2 of the printed circuit board according to Embodiment 3. [Modes for carrying out the invention]

[0010] The embodiments will be described below with reference to the figures. In the following, the same or corresponding parts will be denoted by the same reference numerals, and redundant explanations will not be repeated.

[0011] Embodiment 1. Referring to Figure 1, the configuration of the printed circuit board 100 according to Embodiment 1 will be described. Figure 1 is a schematic cross-sectional view showing the solder joints in the through-holes 2 of the printed circuit board 100 according to Embodiment 1.

[0012] The printed circuit board 100 comprises a substrate 1, through-holes 2, electronic components 3, solder 5, and resist 6. The substrate 1 has a first surface 1a and a second surface 1b opposite to the first surface 1a. The first surface 1a is the mounting surface for the electronic components 3 on which the electronic components 3 are mounted. The second surface 1b is the opposite surface to the mounting surface for the electronic components 3. In other words, the second surface 1b is the surface opposite to the mounting surface for the electronic components 3. The substrate 1 is provided with through-holes H that penetrate the first surface 1a and the second surface 1b. The through-holes H are located at predetermined locations on the substrate 1. The substrate 1 is, for example, made of glass cloth containing epoxy resin.

[0013] The through-hole 2 has a conductive layer 2a positioned on the side surface of the through-hole H provided in the substrate 1. In other words, the conductive layer 2a is positioned on the inner wall surface of the through-hole H. The conductive layer 2a is, for example, copper plating. In this embodiment, the conductive layer 2a is positioned continuously on the side surface of the through-hole 2 and on the first surface 1a and second surface 1b surrounding the through-hole 2.

[0014] Electronic component 3 is an through-hole component. Electronic component 3 is, for example, a connector component or a capacitor. The connector component or capacitor is, for example, made of polyamide. Electronic component 3 has leads 4. The leads 4 protrude from the body 3a of electronic component 3. The leads 4 are inserted into the through-hole 2 from the first surface 1a side of the substrate 1. The body 3a of electronic component 3 is positioned on the first surface 1a side with the leads 4 inserted into the through-hole 2. The leads 4, which are external electrode terminals, are, for example, tin-plated copper electrode leads. The leads 4 are housed within the through-hole 2 on the second surface 1b side of the substrate 1. More specifically, the tip of the lead 4 on the second surface 1b side of the substrate 1 is housed within the through-hole 2. In other words, the leads 4 do not protrude from the through-hole 2 on the second surface 1b side of the substrate 1.

[0015] The lead 4 of the electronic component 3 includes a straight section 10 and an intersection 11 connected to the straight section 10. The straight section 10 extends in the direction in which the through hole H penetrates the first surface 1a and the second surface 1b. The straight section 10 extends in a straight line. In other words, the straight section 10 has a straight shape. The direction in which the through hole H penetrates the first surface 1a and the second surface 1b is the first direction D1 in which the first surface 1a and the second surface 1b face each other. The first direction D1 is the depth direction of the through hole H.

[0016] The intersection part 11 is configured to intersect the straight part 10. The intersection part 11 is disposed within the through-hole 2. That is, the intersection part 11 is provided so as to fit within the through-hole 2. The intersection part 11 extends in a second direction D2 that is orthogonal to the first direction D1. The second direction D2 is the radial direction of the through-hole H. The intersection part 11 may be provided at one or more locations of the lead 4.

[0017] In the present embodiment, the lead 4 is configured in a J shape. Here, the J shape means that the tip of the lead 4 is bent by 90 degrees or more. The tip of the lead 4 is bent by 90 degrees or more and is bent or curved at the intersection part 11.

[0018] In the present embodiment, the intersection part 11 is a bent part 11a formed by bending. The bent part 11a is provided so as to fit within the through-hole 2.

[0019] The solder 5 is supplied to the through-hole 2 so as to contact the conductive layer 2a. The through-hole 2 is filled with the solder 5. The lead 4 is inserted into the through-hole 2 supplied with the solder 5. The resist 6 is disposed on each of the first surface 1a and the second surface 1b of the base material 1. The resist 6 partially covers the first surface 1a and the second surface 1b of the base material 1.

[0020] Next, with reference to FIGS. 2 to 5, a method for manufacturing the printed wiring board 100 according to Embodiment 1 will be described. In the method for manufacturing the printed wiring board 100 according to Embodiment 1, the pin-in-paste method is used as the soldering method for the through-hole 2 of the printed wiring board 100.

[0021] First, as shown in Figure 2, solder paste 8 is supplied to the through-holes 2 by screen printing using a metal mask 7. Figure 2 is a schematic cross-sectional view showing the method of printing solder paste 8 using a metal mask 7. The metal mask 7 is a plate material with openings provided at predetermined locations. The material of the metal mask is, for example, SUS (stainless steel). The thickness of the metal mask 7 is, for example, 150 μm. The solder paste 8 is a mixture of solder balls and flux. The solder balls have an alloy composition of, for example, Sn-3.0Ag-0.5Cu, which is a common lead-free solder. The particle size of the solder balls is, for example, 30 μm. However, the above composition and particle size of the solder balls are examples only and are not limited to these. The main component of the flux is, for example, rosin.

[0022] Next, as shown in Figure 3, the metal mask 7 is removed and the leads 4 of the electronic component 3 are inserted into the through-holes 2. Figure 3 is a schematic cross-sectional view showing the state in which the leads 4 of the electronic component 3 are inserted into the through-holes 2.

[0023] Next, as shown in Figure 4, the printed circuit board 100 is heated in a reflow oven at, for example, 250°C, and the solder paste 8 is melted, forming the solder joints of the through-holes 2. During heating in the reflow oven, the molten solder balls aggregate, forming the solder joints in the through-holes 2. Figure 4 is a schematic cross-sectional view showing the state of the solder joints of the through-holes 2 formed by the pin-in-paste soldering method.

[0024] Next, as shown in Figure 5, the printed circuit board 100 is inverted, and soldering is performed on the side opposite to the mounting surface of the electronic component 3. Figure 5 is a schematic cross-sectional view showing the soldering state of the surface mount component 15. Solder paste 16 is supplied to the pads 17, which are copper electrodes, by screen printing using a metal mask 7. Then, the surface mount component 15 is attracted by a suction nozzle and mounted on the pads 17. The surface mount component 15 is, for example, a ceramic capacitor. In this state, the solder paste 16 is melted in a reflow oven to form the solder joint of the pad 17. At this time, the leads 4 do not protrude from the through-holes 2 on the side opposite to the mounting surface of the electronic component 3.

[0025] The effects and advantages of the printed circuit board 100 according to Embodiment 1 will be explained in comparison with a comparative example.

[0026] The comparative example printed circuit board 100 has the same configuration as the printed circuit board described in Patent Document 1. In other words, in the comparative example printed circuit board 100, the shape of the lead 4 of the electronic component 3 is straight. As a result, the contact area between the lead 4 and the solder 5 is small, so there is a possibility that the lead 4 may come loose from the solder joint and the electronic component 3 may fall off.

[0027] On the other hand, according to the printed circuit board 100 of Embodiment 1, the lead 4 of the electronic component 3 includes a straight portion 10 and an intersecting portion 11 connected to the straight portion 10, and the intersecting portion 11 is configured to intersect with the straight portion 10. Therefore, because the contact area between the lead 4 and the solder 5 is large, the detachment of the electronic component 3 can be suppressed.

[0028] After the electronic component 3 is mounted, the soldered printed circuit board 100 is mounted in the housing and put into operation. However, if the electronic component 3 is a connector, the connector will be inserted and removed many times. In this case, in the comparative example, because the contact area between the lead 4 of the electronic component 3 and the solder 5 is small, there is a possibility that the lead 4 may detach from the solder joint after a small number of insertions and removals.

[0029] On the other hand, in the printed circuit board 100 according to Embodiment 1, the contact area between the lead 4 and the solder 5 is large due to the intersection portion 11, so that the lead 4 does not fall off the solder joint even if the number of insertions and removals is large. For this reason, a highly reliable printed circuit board 100 and electronic equipment equipped with the printed circuit board 100 can be supplied.

[0030] Furthermore, in the comparative example printed circuit board 100, the leads 4 protrude from the through-holes 2 on the side opposite to the mounting surface of the electronic component 3. Therefore, it is difficult to print solder paste 8 on the side opposite to the mounting surface of the electronic component 3. This results in significant design constraints.

[0031] On the other hand, according to the printed circuit board 100 of Embodiment 1, the leads 4 are housed within the through-holes 2 on the second surface 1b side of the substrate 1. Therefore, the leads 4 do not protrude from the through-holes 2 on the second surface 1b side, which is the side opposite to the mounting surface of the electronic components 3. Consequently, solder paste 8 can be printed on the second surface 1b side of the substrate 1, thereby reducing design constraints.

[0032] Furthermore, in the comparative example printed circuit board 100, when screen printing using the metal mask 7 on the side opposite to the mounting surface of the electronic component 3, the leads 4 protrude from the through-holes 2, resulting in poor adhesion between the metal mask 7 and the printed circuit board 100. Therefore, it is difficult to supply the solder paste 8 according to the design specifications. As a result, after mounting the surface mount component 15, a difference in solder volume occurs between the left and right pads 17, which may lead to mounting defects such as chip protrusion. In addition, if the solder fillet volume differs between the left and right pads 17 after mounting the surface mount component 15, the strain generated by temperature cycling in the operating environment will be uneven, which may impair the reliability of the solder joint.

[0033] On the other hand, in the printed circuit board 100 according to Embodiment 1, since the leads 4 do not protrude from the through-holes 2 during screen printing, the adhesion between the metal mask 7 and the printed circuit board 100 is good. As a result, it is possible to supply solder paste 8 according to the design value. As a result, the volume of solder on the left and right pads 17 is constant after mounting the surface mount components 15, so mounting defects such as chip sticking can be prevented. Therefore, a printed circuit board 100 with excellent workability can be supplied. In addition, since it is possible to suppress differences in the volume of solder fillets on the left and right pads 17 after mounting the surface mount components 15, it is possible to suppress uneven strain caused by temperature cycles in the operating environment, so a printed circuit board 100 with high reliability of solder joints can be supplied.

[0034] According to the printed circuit board 100 of Embodiment 1, the intersection 11 is a bent portion 11a formed by bending. Therefore, the bent portion 11a allows for a larger surface area of ​​the lead 4 embedded in the solder 5, enabling joining over a larger area. Consequently, the contact area between the lead 4 and the solder 5 is large, which helps to prevent the electronic component 3 from falling off.

[0035] In this embodiment, the base material 1 is described as a base material containing epoxy resin in glass cloth, but it is not limited to this, and the same effect can be obtained by using an insulating material, such as a glass nonwoven fabric or a paper base material containing polyimide resin, phenolic resin, etc.

[0036] Furthermore, although this embodiment describes the supply of solder paste 8 using screen printing with a metal mask 7, it is not limited to this, and similar effects can be obtained by supplying it with a dispenser.

[0037] Furthermore, although this embodiment describes the case where a rosin-based flux is used, the effect is not limited to this, and similar effects can be obtained with a polymer-based flux.

[0038] Furthermore, the materials of both the main body 3a and the leads 4 of the electronic component 3 are not limited to those described above.

[0039] Furthermore, although this embodiment describes the case where the surface-mount component 15 is a ceramic capacitor, it is not limited to this.

[0040] Furthermore, although this embodiment describes the case where the solder ball is made of Sn-Ag-Cu solder, it is not limited to this, and the same effect can be obtained by using any of Sn-Cu, Sn-Bi, Sn-In, Sn-Sb, or Sn-Pb solder.

[0041] Embodiment 2. Embodiment 2 has the same configuration, manufacturing method, and effects as Embodiment 1 unless otherwise specified. Therefore, the same reference numerals are used for components identical to those in Embodiment 1, and the descriptions are not repeated.

[0042] Referring to Figure 6, the configuration of the printed circuit board 100 according to Embodiment 2 will be described. Figure 6 is a schematic cross-sectional view showing the solder joints in the through-holes 2 of the printed circuit board 100 according to Embodiment 2.

[0043] In the printed circuit board 100 according to Embodiment 2, the intersection 11 is a burring portion 11b formed by burring. The burring portion 11b is provided to fit within the through-hole 2. Here, the burring portion 11b is formed by a processing technique called burring, which creates a small flange or edge on the end of a metal by press working or turning. In other words, the burring portion 11b is a protrusion provided on a part of the lead 4 in a direction perpendicular to the extension direction by processing the lead 4 by press working or turning.

[0044] The effects and advantages of the printed circuit board 100 according to Embodiment 2 will be explained. According to the printed circuit board 100 of Embodiment 2, the intersection 11 is a burred portion 11b formed by burring. Therefore, the burred portion 11b allows for a larger surface area of ​​the lead 4 embedded in the solder 5, enabling joining over a larger area. Consequently, the contact area between the lead 4 and the solder 5 is large, which helps to prevent the electronic component 3 from falling off.

[0045] Furthermore, since the lead 4 is provided with a burring section 11b, the contact area between the lead 4 and the solder 5 can be increased. Therefore, even if the electronic component 3 is a connector and the connector is inserted and removed many times, it is possible to suppress the lead 4 from falling off the solder joint. As a result, it is possible to supply a highly reliable printed circuit board 100 and electronic equipment equipped with the printed circuit board 100.

[0046] Furthermore, even when bending is difficult due to the large thickness of the lead 4, the burring portion 11b formed by the burring process can provide the same effect as in Embodiment 1.

[0047] In this embodiment, the case where there is only one burring section 11b has been described, but it is not limited to this, and the same effect can be obtained even if multiple sections are provided.

[0048] Embodiment 3. Embodiment 3 has the same configuration, manufacturing method, and effects as Embodiment 1 unless otherwise specified. Therefore, the same reference numerals are used for components identical to those in Embodiment 1, and the descriptions are not repeated.

[0049] Referring to Figure 7, the configuration of the printed circuit board 100 according to Embodiment 3 will be described. Figure 7 is a schematic cross-sectional view showing the solder joints in the through-holes 2 of the printed circuit board 100 according to Embodiment 3.

[0050] In the printed circuit board 100 according to Embodiment 3, the intersection 11 is a bent portion 11a formed by bending and a burred portion 11b formed by burring. In this embodiment, the direction in which the burred portion 11b protrudes from the lead 4 is the same as the direction in which the bent portion 11a is bent. The bent portion 11a protrudes from the burred portion 11b in the second direction D2.

[0051] Referring to Figure 8, the configuration of Modified Example 1 of the printed circuit board 100 according to Embodiment 3 will be described. Figure 8 is a schematic cross-sectional view showing the solder joint in the through-hole 2 of Modified Example 1 of the printed circuit board 100 according to Embodiment 3.

[0052] In Modification 1 of the printed circuit board 100 according to Embodiment 3, the leads 4 of the electronic component 3 are provided on both sides of the electronic component 3 in the second direction D2. The leads 4 provided on both sides of the electronic component 3 each have a bent portion 11a and a burred portion 11b. The leads 4 of the electronic component 3 protrude from the main body 3a in the second direction D2, then bend toward the through-hole 2, extend in the first direction D1, and then curve in the second direction D2 within the through-hole 2. The direction of bending of the bent portion 11a is inward. The direction of burring of the burred portion 11b is inward. The bent portion 11a and the burred portion 11b overlap with at least one of the portions of the main body 3a and the leads 4 of the electronic component 3 that extend outward in the first direction D1.

[0053] Referring to Figure 9, the configuration of Modified Example 2 of the printed circuit board 100 according to Embodiment 3 will be described. Figure 9 is a schematic cross-sectional view showing the solder joint in the through-hole 2 of Modified Example 2 of the printed circuit board 100 according to Embodiment 3.

[0054] In the modified example 2 of the printed circuit board 100 according to Embodiment 3, the bending direction of the bent portion 11a is outward. The burring direction of the burring portion 11b is also outward. The bent portion 11a and the burring portion 11b do not overlap with the portions that extend outward in the first direction D1 toward the body 3a and lead 4 of the electronic component 3.

[0055] The effects and advantages of the printed circuit board 100 according to Embodiment 3 will be described below. According to the printed circuit board 100 of Embodiment 3, the intersection 11 is a bent portion 11a formed by bending and a burred portion 11b formed by burring. Therefore, both the bent portion 11a and the burred portion 11b can further increase the surface area of ​​the lead 4 embedded in the solder 5, thus providing a more reliable solder joint. In addition, since the contact area between the lead 4 and the solder 5 can be further increased, even if the electronic component 3 is a connector and the connector is inserted and removed many times, the detachment of the lead 4 from the solder joint can be further suppressed. For this reason, it is possible to supply a printed circuit board 100 and electronic equipment equipped with the printed circuit board 100 that are even more reliable.

[0056] In the printed circuit board 100 according to Embodiment 3, the direction in which the burring portion 11b protrudes from the lead 4 is the same as the direction in which the bending portion 11a is bent. Therefore, it becomes easy to insert the bending portion 11a and the burring portion 11b into the through-hole 2.

[0057] In the modified example 1 of the printed circuit board 100 according to Embodiment 3, the bending direction of the bent portion 11a and the burring direction of the burring portion 11b are inward, so the bent portion 11a and the burring portion 11b overlap with at least one of the portions of the body 3a and lead 4 of the electronic component 3 that extend outward in the first direction D1. Therefore, the substrate area of ​​the printed circuit board 100 can be reduced.

[0058] In the modified example 2 of the printed circuit board 100 according to Embodiment 3, the bending direction of the bent portion 11a and the burring direction of the burring portion 11b are outward, so the solder 5 in the bent portion 11a can be visually inspected from the outside of the electronic component 3. Therefore, it becomes easier to determine whether or not the solder 5 is wet during inspection after soldering, thereby improving inspectionability. As a result, a printed circuit board 100 with excellent workability can be provided.

[0059] The above embodiments can be combined as appropriate. The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended. [Explanation of Symbols]

[0060] 1 Substrate, 1a First surface, 1b Second surface, 2 Through-hole, 2a Conductive layer, 3 Electronic component, 4 Lead, 5 Solder, 6 Resist, 7 Metal mask, 8 Solder paste, 10 Straight section, 11 Intersection, 11a Bent section, 11b Burring section, 100 Printed circuit board, H Through hole.

Claims

1. A substrate having a first surface and a second surface opposite to the first surface, and having a through hole that penetrates the first surface and the second surface, A through-hole having a conductive layer disposed on the side surface of the through-hole provided in the substrate, Solder supplied to the through-hole so as to be in contact with the conductive layer, The electronic component comprises an electronic component having leads inserted into the through-hole into which the aforementioned solder is supplied, The lead of the electronic component includes a straight portion and an intersecting portion connected to the straight portion. The straight portion extends in a direction in which the through hole penetrates the first surface and the second surface. The aforementioned intersection is configured to intersect the aforementioned straight section, The lead is housed within the through-hole on the second surface side of the substrate, in a printed circuit board.

2. The printed circuit board according to claim 1, wherein the intersection is a bent portion formed by bending.

3. The printed circuit board according to claim 1, wherein the intersection is a burring-processed portion formed by burring.

4. The printed circuit board according to claim 1, wherein the intersection portion is a bent portion formed by bending and a burred portion formed by burring.

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