Printed wiring board, circuit board, and method for manufacturing circuit board

Abstract

This printed wiring board (100) has a through-hole (2) penetrating from a first surface (H1) to a second surface (H2) facing the first surface (H1), the inner wall of the through-hole (2) being formed of a conductive material to constitute a through-hole electrode (3) and an auxiliary hole (5) having an opening at the first surface (H1) and connected to the inner wall of the through-hole (2) in a direction along the first surface (H1), the inner wall of the auxiliary hole (5) being formed of a material having a lower solder wettability than the conductive material to constitute an auxiliary part (6).

Description

Printed Wiring Board, Circuit Board, and Method for Manufacturing Circuit Board

[0001] The present disclosure relates to a printed wiring board, a circuit board, and a method for manufacturing a circuit board.

[0002] There is a soldering method in which after printing solder paste on the through-holes of a printed wiring board, inserting the leads of electronic components into the through-holes, and heating in a reflow furnace for soldering.In this method, when the amount of solder paste filled in the through-holes is small, there is a problem that the solder joint becomes small and the joint reliability decreases.

[0003] In Patent Document 1, a printed wiring board has component through-holes with copper plating or the like applied to the inner walls of the holes and non-through-holes without copper plating or the like applied to the inner walls of the holes. On the solder side, which is one main surface of the printed wiring board, an extended land portion extended from the land portion of the component through-hole is provided in contact with the non-through-hole. On the solder side, solder paste is printed on the extended land portion and the non-through-hole, and by heating and cooling, solder pools are formed in the extended land portion and the non-through-hole.Next, on the component side, which is the other main surface of the printed wiring board, solder paste is printed on the component through-hole and the land portion, and after inserting the component terminals of the inserted component toward the component through-hole, reflow heat is applied to the component side.As a result, the solder pool on the solder side is remelted, and a solder fillet is formed on the component terminals protruding from the solder side.

[0004] Japanese Patent Application Laid-Open No. 2021-125552

[0005] In the method for manufacturing a printed circuit board in Patent Document 1, since the non-through-hole and the component through-hole are separated, there is a problem that only a part of the solder of the remelted solder pool spreads wet up to the component through-hole.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide a circuit board capable of improving joint reliability by increasing the solder volume of the solder joint.

[0007] The printed circuit board according to this disclosure is characterized by having through-hole electrodes that penetrate from a first surface to a second surface opposite the first surface, with the inner wall of the through-hole being made of a conductive material, and auxiliary holes that have an opening on the first surface and are connected in a direction along the inner wall of the through-hole and the first surface, with the material of the inner wall of the auxiliary hole being less solder-wettable than the conductive material.

[0008] Furthermore, the circuit board according to this disclosure is characterized by having a through-hole that penetrates from a first surface of the printed wiring board to a second surface opposite the first surface, and the inner wall of the through-hole is made of a conductive material, an auxiliary part that has an opening on the first surface and is connected in a direction along the inner wall of the through-hole and the first surface, and the material of the inner wall of the auxiliary part has lower solder wettability than the conductive material, and an electronic component that is inserted into the through-hole of the through-hole electrode and has a lead terminal that is joined to the inner wall of the through-hole via solder.

[0009] Furthermore, the present disclosure relates to a method for manufacturing a circuit board on which electronic components are mounted, and the printed wiring board comprises a through-hole electrode having a through-hole that penetrates from a first surface to a second surface opposite the first surface, the inner wall of which is made of a conductive material, and an auxiliary part having an opening on the first surface and connected in a direction along the inner wall of the through-hole to the first surface, the material of which is made of a material that has lower solder wettability than the conductive material, and the method for manufacturing a circuit board on which electronic components are mounted, comprising the steps of filling the through-hole and auxiliary hole with solder paste via a mask having openings corresponding to the through-hole and auxiliary hole, inserting lead terminals of electronic components into the solder paste filled in the through-hole, and reflow heating the solder paste filled in the through-hole and auxiliary hole.

[0010] The circuit board relating to this disclosure can improve the reliability of solder joints.

[0011] This is a plan view showing the printed circuit board 100 according to Embodiment 1. This is a cross-sectional view showing the A1-A1 cross-section in Figure 1. This is a cross-sectional view showing the B1-B1 cross-section in Figure 1. This is a cross-sectional view showing the state of the first step in the manufacturing method of the circuit board 200 according to Embodiment 1. This is a cross-sectional view showing the state of the second step in the manufacturing method of the circuit board 200 according to Embodiment 1. This is a cross-sectional view showing the state of the third step in the manufacturing method of the circuit board 200 according to Embodiment 1. This is a cross-sectional view showing the state of the fourth step in the manufacturing method of the circuit board 200 according to Embodiment 1. This is a cross-sectional view showing the state of the fifth step in the manufacturing method of the circuit board 200 according to Embodiment 1. This is a cross-sectional view showing the C1-C1 cross-section in Figure 4D. This is a cross-sectional view showing the C2-C2 cross-section in Figure 4E. This is a cross-sectional view showing the A2-A2 cross-section in Figure 6. This is a cross-sectional view showing the B2-B2 cross-section in Figure 6. This is a plan view showing the printed circuit board 100a according to Embodiment 2. This is a cross-sectional view showing the A3-A3 cross-section in Figure 9. This is a cross-sectional view showing the state of the first step in the manufacturing method of the circuit board 200a according to Embodiment 2. This is a cross-sectional view showing the state of the second step in the manufacturing method of the circuit board 200a according to Embodiment 2. This is a cross-sectional view showing the state of the third step in the manufacturing method of the circuit board 200a according to Embodiment 2. This is a cross-sectional view showing the state of the fourth step in the manufacturing method of the circuit board 200a according to Embodiment 2. This is a cross-sectional view showing the state of the fifth step in the manufacturing method of the circuit board 200a according to Embodiment 2. This is a cross-sectional view showing the A3-A3 cross section in Figure 9 of a modified example of the printed wiring board 100a according to Embodiment 2. This is a plan view showing the printed wiring board 100b according to Embodiment 3. This is a cross-sectional view showing the A4-A4 cross section in Figure 13. This is a cross-sectional view of the circuit board 200b according to Embodiment 4. This is a cross-sectional view showing the C3-C3 cross section in Figure 15 of a modified example of the circuit board 200b according to Embodiment 4. This is a plan view of the printed wiring board 100c according to Embodiment 5. This is a cross-sectional view showing the A5-A5 cross section in Figure 18. This is a cross-sectional view at the same position as the A5-A5 cross section of the circuit board 200c according to Embodiment 5. This is a plan view of the printed wiring board 100d according to Embodiment 6.This is a cross-sectional view showing the A6-A6 section shown in Figure 21. This is a cross-sectional view at the same position as the A6-A6 section of the circuit board 200d according to Embodiment 6.

[0012] The printed wiring board, circuit board, and method for manufacturing the circuit board according to the embodiment will be described in detail below with reference to the drawings. Embodiment 1. Figure 1 is a plan view of the printed wiring board 100 according to Embodiment 1, Figure 2 is a cross-sectional view showing the A1-A1 section of the printed wiring board 100, and Figure 3 is a cross-sectional view showing the B1-B1 section of the printed wiring board 100.

[0013] The printed circuit board 100 comprises a base material 1 made of glass cloth containing epoxy resin, through-hole electrodes 3 including through holes 2, and auxiliary parts 6 including auxiliary holes 5.

[0014] The through-hole 2 is a hole that penetrates from the first surface H1 to the second surface H2 of the base material 1, and its inner wall is made of a conductive material such as copper. The auxiliary hole 5 is connected to the inner wall of the through-hole 2 via a connecting part 4 in a direction along the first surface H1. The connecting part 4 is a plane that includes the two intersection lines of the inner wall of the through-hole 2 and the auxiliary hole 5, and the width X of the connecting part 4 is the distance between the two intersection lines on the first surface H1. The auxiliary hole 5 is also a hole that penetrates from the first surface H1 to the second surface H2 of the base material 1, and the inner wall of the auxiliary hole 5 is made of a material with lower solder wettability than the inner wall of the through-hole 2. The inner wall of the auxiliary hole 5 may be an auxiliary part 6 made of a processed surface of resin obtained by punching out the base material 1, or an auxiliary part 6 made by covering the processed surface with a material with lower solder wettability than the inner wall of the through-hole 2.

[0015] A manufacturing method for producing a circuit board 200, on which electronic components 14 are mounted on a printed wiring board 100, will be explained using Figures 4A to 4E. The manufacturing method for the circuit board 200 includes steps 1 to 5. Figure 4A is a cross-sectional view showing the state of the first step in the manufacturing method of the circuit board 200, and shows the same state as in Figure 2.

[0016] Figure 4B is a cross-sectional view showing the state of the second step in the manufacturing method of the circuit board 200. In the second step in the manufacturing method of the circuit board 200, the metal mask 10 is aligned with and placed on the first surface H1 of the substrate 1, and then the squeegee 11 is moved in the first direction, which is the direction of the through hole 2, to apply the solder paste 12 to the first surface H1. The metal mask 10 is made of, for example, a stainless steel plate with openings at predetermined locations, and its thickness can be 60 to 200 μm. The solder paste 12 is made by uniformly mixing solder balls with flux, organic solvents, etc., to form a paste. The solder balls are, for example, a common lead-free solder alloy Sn-3.0Ag-0.5Cu, with a particle size of about 30 μm. The flux is, for example, mainly composed of rosin.

[0017] Figure 4C is a cross-sectional view showing the state of the third step in the manufacturing method of the circuit board 200. The third step in the manufacturing method of the circuit board 200 shows the structure after the squeegee 11 has passed over the through holes 2 and auxiliary holes 5, and solder paste 13 is filled into a portion of the through holes 2 and auxiliary holes 5 on the first surface H1 side from the opening of the metal mask 10. If necessary, the entire through holes 2 and auxiliary holes 5 may be filled.

[0018] Figure 4D is a cross-sectional view showing the state of the fourth step in the manufacturing method of the circuit board 200. The fourth step in the manufacturing method of the circuit board 200 shows the structure after the lead terminals 15 of the electronic component 14 have been inserted into the through-hole 2. The electronic component 14 is, for example, a connector component, and the lead terminals 15 are, for example, tin-plated copper electrode leads. Figure 5 shows the cross-section (C1-C1 cross-section) on the first surface H1 at this time. Here, the lead terminals 15 are made of square wire, but other types such as round wire may also be used.

[0019] Figure 4E is a cross-sectional view showing the state of the fifth step in the manufacturing method of the circuit board 200. In the fifth step in the manufacturing method of the circuit board 200, the solder paste 13 in the through holes 2 and auxiliary holes 5 is melted by reflow heating. Specifically, the solder joints are formed by heating by transporting the components on a belt conveyor inside a reflow oven set to 230 degrees Celsius or higher. This completes the manufacturing of the circuit board 200. The temperature of the reflow oven can be set appropriately according to the type of solder.

[0020] Here, the solder paste 13 filled in the auxiliary hole 5 spreads outwards toward the inner wall of the through hole 2, which has higher solder wettability than the inner wall of the auxiliary hole 5, due to reflow heating. As a result, the solder volume of the solder joint 16 can be increased compared to the case where there is no auxiliary hole 5, or compared to the case where the solder wettability of the inner wall of the auxiliary hole 5 is higher than that of the inner wall of the through hole 2, due to the effect of the solder paste 13 filled in the auxiliary hole 5. Also, because the solder wettability of the inner wall of the auxiliary hole 5 is lower than that of the inner wall of the through hole 2, less molten solder paste 13 remains inside the auxiliary hole 5, and can be efficiently moved from the inside of the auxiliary hole 5 toward the through-hole electrode 3. The cross section (C2-C2 cross section) on the first surface H1 at this time is shown in Figure 6. A solder joint 16 can be formed between the through-hole electrode 3 and the lead terminal 15, which is filled in the thickness direction of the base material 1, and the reliability of the solder joint 16 can be improved.

[0021] From the above, in the manufacturing method of the circuit board 200, by making the solder wettability of the inner wall of the auxiliary hole 5 lower than that of the inner wall of the through hole 2, the solder can be efficiently moved from the inside of the auxiliary part 6 to the through-hole electrode 3 side in the fifth step of the manufacturing method of the circuit board 200. As a result, the solder volume of the solder joint 16 can be made larger compared to the case where there is no auxiliary hole 5, or compared to the case where the solder wettability of the inner wall of the auxiliary hole 5 is greater than or equal to that of the inner wall of the through hole 2, thereby improving the bonding reliability of the solder joint 16.

[0022] Furthermore, in the second step of the manufacturing method of the circuit board 200, the squeegee 11 is moved in the first direction, thereby sequentially filling the openings on the first surface H1 of the through holes 2 and auxiliary holes 5 in the longitudinal direction. As a result, the solder paste 13 can be easily filled, and the volume of solder paste 13 inside the through holes 2 and auxiliary holes 5 can be increased.

[0023] In the circuit board 200, by making the inner wall of the auxiliary hole 5 less solder-wettable than the inner wall of the through hole 2, the solder volume of the solder joint 16 can be increased compared to the case where there is no auxiliary hole 5, or compared to the case where the solder-wettability of the inner wall of the auxiliary hole 5 is greater than or equal to that of the inner wall of the through hole 2, thereby improving the reliability of the solder joint 16.

[0024] During heating and melting, flux and organic solvents contained in the solder paste 13 are scattered, so the volume of the solder joint 16 after melting is reduced compared to the initial solder paste 13. Therefore, the volume of the solder joint 16 is generally about 50% of the volume of the solder paste 13 before melting that filled the through hole 2 and auxiliary hole 5. Since the volume of the solder paste 13 before melting is about twice that of the solder joint 16 obtained after melting, the volume of the auxiliary hole 5 only needs to be at least once that of the volume of the through hole 2. In other words, by making the volume of the auxiliary hole 5 smaller than the volume of the through hole 2, the printed circuit board can be miniaturized.

[0025] By making the auxiliary hole 5 penetrate from the first surface to the second surface, it becomes unnecessary to control the depth when drilling holes in the base material 1, thus simplifying the manufacturing process.

[0026] Although the cross-sectional shape of the auxiliary hole 5 is circular, it may also be elliptical or polygonal. If the cross-sectional shape of the auxiliary hole 5 is circular or elliptical, there will be no discontinuous surface on the inner wall, which will promote the wetting and spreading of solder into the through hole 2 during reflow heating.

[0027] By making the inner wall of the auxiliary hole 5 the same material as the base material 1, i.e., resin, the solder wettability of the auxiliary hole 5 can be significantly reduced, thereby promoting the wetting and spreading of solder toward the inner wall of the through hole 2. At this time, Figure 7 shows a cross-sectional view of the A2-A2 section of the circuit board 200 on which the electronic component 14 is mounted, as shown in Figure 6, and Figure 8 shows a cross-sectional view of the B2-B2 section. The solder filled in the auxiliary hole 5 flows between the through-hole electrode 3, whose inner wall is made of a conductive material, and the solder joint 16, thereby improving the reliability of the solder joint 16.

[0028] Furthermore, the substrate 1 is not limited to glass cloth containing epoxy resin; similar effects can be obtained with insulating materials such as glass nonwoven fabric or paper substrate containing polyimide resin or phenolic resin. Although the solder paste 13 was supplied by screen printing using a metal mask 10, similar effects can be obtained by supplying it with a dispenser.

[0029] The flux contained in the solder paste 13 is not limited to rosin-based flux; the same effect can be obtained with polymer-based flux. The same effect can be obtained with other materials for the body of the mounted electronic component 14. Also, the same effect can be obtained with any material that has solder wettability for the lead terminals 15. The solder balls of the solder paste 13 are not limited to Sn-Ag-Cu-based solder; the same effect can be obtained using any of Sn-Cu-based solder, Sn-Bi-based solder, Sn-In-based solder, Sn-Sb-based solder, or Sn-Pb-based solder. Embodiment 2. Embodiment 1 described a structure having an auxiliary part 6 including an auxiliary hole 5 that penetrates the base material 1, but Embodiment 2 differs from Embodiment 1 in that it has an auxiliary part 6a including an auxiliary hole 5a that does not penetrate the base material 1. Embodiment 2 describes only the parts that differ in configuration from Embodiment 1. Also, the same figure numbers are used for configurations that are the same as or corresponding to Embodiment 1, and their descriptions are omitted.

[0030] The printed circuit board 100a comprises a base material 1 containing epoxy resin in glass cloth, through-hole electrodes 3 including through holes 2, and auxiliary parts 6a including auxiliary holes 5a.

[0031] Figure 9 is a plan view of the printed circuit board 100a according to Embodiment 2, and Figure 10 is a cross-sectional view showing the A3-A3 section of the printed circuit board 100a in Figure 9. The auxiliary hole 5a is connected to the inner wall of the through hole 2 in a part of the thickness direction of the base material 1 via a connecting portion 4a provided on the first surface H1 side in a direction along the first surface H1.

[0032] A manufacturing method for producing a circuit board 200a, on which electronic components 14 are mounted on a printed wiring board 100a, will be explained using Figures 11A to 11E. The manufacturing method for the circuit board 200a includes steps 1 to 5. Figure 11A is a cross-sectional view showing the state of the first step in the manufacturing method of the circuit board 200a, and shows the same state as in Figure 8.

[0033] Figure 11B is a cross-sectional view showing the state of the second step in the manufacturing method of the circuit board 200a. In the second step in the manufacturing method of the circuit board 200a, the metal mask 10 is aligned with the first surface H1 of the substrate 1 and placed on top, and then the squeegee 11 is moved in the first direction, which is the direction of the through hole 2, from the auxiliary hole 5a to apply the solder paste 12.

[0034] Figure 11C is a cross-sectional view showing the state of the third step in the manufacturing method of the circuit board 200a. In the third step of the manufacturing method of the circuit board 200a, the squeegee 11 passes over the through hole 2 and auxiliary hole 5a, and solder paste 13 is filled into the through hole 2 and auxiliary hole 5a from the opening of the metal mask 10.

[0035] Figure 11D is a cross-sectional view showing the state of the fourth step in the manufacturing method of the circuit board 200a. In the fourth step in the manufacturing method of the circuit board 200a, the lead terminals 15 of the electronic component 14 are inserted into the solder paste 13 of the through hole 2.

[0036] Figure 11E is a cross-sectional view showing the state of the fifth step in the manufacturing method of the circuit board 200a. Reflow heating melts the solder paste 13 in the through holes 2 and auxiliary holes 5a. This manufactures the circuit board 200a. Here, the solder filled in the auxiliary holes 5a spreads towards the inner wall of the through holes 2, which has higher solder wettability than the inner wall of the auxiliary holes 5a, and can form a solder joint 16 that is filled in the thickness direction of the substrate 1 of the through-hole electrode 3. Since the auxiliary holes 5a do not penetrate from the first surface to the second surface, the amount of solder paste 13 can be optimized by adjusting the depth of the holes according to the required amount of solder paste 13.

[0037] Here, the auxiliary hole 5a may be provided with an inclined portion 7, as shown in Figure 12, so that the solder paste 13 filled in the auxiliary hole 5a can easily wet and spread toward the inner wall of the through hole 2. The area of ​​the cross-section of the inclined portion 7 parallel to the first surface H1 decreases as it moves away from the first surface H1. Embodiment 3. Embodiment 2 described a structure having an auxiliary portion 6a including an auxiliary hole 5a which is a hole connected to the inner wall of the through hole 2 on the first surface H1. Embodiment 3 differs from Embodiment 2 in that it has an auxiliary portion 6b including an auxiliary hole 5b which is a hole connected to the inner wall of the through hole 2 midway between the first surface H1 and the second surface H2. Embodiment 3 will only describe the parts that differ in configuration from Embodiment 2. Also, the same figure numbers will be used for configurations that are the same as or corresponding to those in Embodiment 2, and their descriptions will be omitted.

[0038] The printed circuit board 100b comprises a base material 1 containing epoxy resin in glass cloth, through-hole electrodes 3 including through holes 2, and auxiliary parts 6b including auxiliary holes 5b.

[0039] Figure 13 is a plan view of the printed circuit board 100b according to Embodiment 3, which is provided with auxiliary holes 5b, and Figure 14 is a cross-sectional view showing the A4-A4 section of the printed circuit board 100b. The auxiliary holes 5b are connected midway between the first surface H1 and the second surface H2 of the inner wall of the through hole 2.

[0040] The auxiliary hole 5b is connected to the inner wall of the through hole 2 via the connecting portion 4b in a direction along the first surface H1. As a result, the solder filled in the auxiliary hole 5b spreads towards the inner wall of the through hole 2, which has higher solder wettability than the inner wall of the auxiliary hole 5b, and a solder joint 16 can be formed that is filled in the thickness direction of the substrate 1 of the through-hole electrode 3. In other words, the solder filled in the auxiliary hole 5b flows between the through-hole electrode, whose inner wall is made of a conductive material, and the solder joint 16, thereby improving the reliability of the solder joint. Embodiment 4. Embodiment 1 described a structure having an auxiliary portion 6 including an auxiliary hole 5 with no limit on the width X of the connecting portion 4. Embodiment 4 differs from Embodiment 1 in that the width X of the connecting portion 4c is smaller than the width Y of the cross-section of the lead terminal 15 of the electronic component 14, forming an auxiliary portion 6c including an auxiliary hole 5c. Embodiment 4 describes only the parts that differ in configuration from Embodiment 1. Also, the same figure numbers are used for configurations that are the same as or corresponding to those in Embodiment 1, and their descriptions are omitted.

[0041] Figure 15 is a cross-sectional view of the circuit board 200b according to Embodiment 4, corresponding to the A1-A1 cross-section in Figure 1 of Embodiment 1. Figure 16 is a cross-sectional view of the first surface H1 of the circuit board 200b (C3-C3 cross-section). If the width X of the connection portion 4c is wider than the width Y of the cross-section of the lead terminal 15, there is a concern that the lead terminal 15 may accidentally enter the auxiliary hole 5b. In the circuit board 200b, the width X of the connection portion 4c is set to be narrower than the width Y of the cross-section of the lead terminal 15 of the electronic component 14, so that the lead terminal 15 does not accidentally enter the auxiliary hole 5b.

[0042] Here, the width Y of the cross-section of the lead terminal 15 should be greater than the width X of the connection portion 4c. The width Y of the cross-section of the lead terminal 15 can be, for example, the length of the shorter side if the cross-section of the lead terminal 15 is rectangular, the length of the diameter if it is circular, or the length of the minor axis if it is elliptical.

[0043] FIG. 17 is a cross-sectional view showing a cross-section (C3 - C3 cross-section) of the first surface H1 of a modified example of the circuit board 200b. By expanding the width of the auxiliary hole 5c in the vertical direction of the drawing towards the connection portion 4c, the solder paste 13 filled in the auxiliary hole 5c can be made to spread easily towards the inner wall of the through-hole 2.

[0044] That is, in a cross-section parallel to the first surface, by making the width X of the connection portion 4c between the inner wall of the through-hole 2 and the auxiliary hole 5c smaller than the width Y of the cross-section of the lead terminal 15, it is possible to prevent accidentally entering the auxiliary hole 5b. As a result, the lead terminal 15 can be retained inside the through-hole 2, and a solder joint portion 16 filled in the thickness direction of the base material 1 can be formed between the through-hole electrode 3 and the lead terminal 15, and the bonding reliability of the solder joint portion 16 can be improved. Embodiment 5. In Embodiment 1, the circuit board 200 in which the electronic component 14 having the lead terminal 15 is mounted on the printed wiring board 100 has been described. However, in Embodiment 5, it is different from Embodiment 1 in that the electronic component 14a having the lead terminals 15a to 15e is mounted on the printed wiring board 100c to form the circuit board 200c. In Embodiment 5, only the parts different in configuration from Embodiment 1 will be described. Also, for the same or corresponding configurations as in Embodiment 1, the same reference numerals will be used and the description thereof will be omitted.

[0045] FIG. 18 is a plan view of the printed wiring board 100c according to Embodiment 5, and FIG. 19 is a cross-sectional view showing the A5 - A5 cross-section of the printed wiring board 100c. FIG. 20 is a cross-sectional view at the same position as the A5 - A5 cross-section of the circuit board 200c according to Embodiment 5 in the fifth step of the manufacturing method of the circuit board 200.

[0046] The printed wiring board 100c has through-hole electrodes 3a to 3e into which an electronic component 14a having lead terminals 15a to 15e is inserted. The electronic component 14a is, for example, a 5-pin type connector. The through-hole electrode 3a has a through-hole 2a, and the auxiliary portion 6d has an auxiliary hole 5d connected to the through-hole 2a via a connection portion 4d. The through-hole electrode 3e has a through-hole 2e, and the auxiliary portion 6e has an auxiliary hole 5e connected to the through-hole 2e via a connection portion 4e. The through-hole electrodes 3b to 3d each have through-holes 2b to 2d.

[0047] After filling the through-holes 2a to 2e of the through-hole electrodes 3a to 3e, the auxiliary hole 5d of the auxiliary portion 6d, and the auxiliary hole 5e of the auxiliary portion 6e with solder paste, the lead terminals 15a to 15e of the electronic component 14a are inserted into the through-holes 2a to 2e of the through-hole electrodes 3a to 3e, respectively, and reflow heating is performed to form solder joints 16a to 16e.

[0048] When using an electronic device equipped with the circuit board 200c, the electronic component 14a and the base material 1 expand due to the temperature rise caused by energization. Due to the difference in the linear expansion coefficients of the electronic component 14a and the base material 1, strain occurs in the solder joints 16a to 16e that connect the through-hole electrodes 3a to 3e and the lead terminals 15a to 15e, respectively. If the bonding reliability is insufficient with respect to the strain of the solder joint, there is a concern that cracks may progress. The strain in the solder joints 16a and 16e at the lead terminals 15a and 15e at both ends of the electronic component 14a is larger than that at the lead terminal 15c in the central portion.

[0049] According to the circuit board 200c of the fifth embodiment, by connecting the through-hole electrode 3a to the auxiliary portion 6d and the through-hole electrode 3e to the auxiliary portion 6e, the bonding reliability of the solder joints 16a and 16e can be improved, and the reliability of the circuit board 200c can be improved.

[0050] Although this explanation describes the case where the electronic component 14a is a 5-pin connector, even in the case of a 2-pin connector, it is possible to improve the reliability of the connection by having an auxiliary hole connected to the through-hole into which the end lead terminals are inserted, compared to when no auxiliary hole is provided. This is not limited to this case, and similar effects can be obtained with any multi-pin electronic component.

[0051] Furthermore, auxiliary holes 5d and 5e are provided, connected to the through holes 5a and 5e into which the lead terminals at both ends are inserted. By having auxiliary holes connected to the through holes into which the lead terminals at at least one end are inserted, it is possible to improve the reliability of the joints. Although auxiliary holes are not provided that connect to the inner walls of the through holes 2b to 2d, by having auxiliary holes connected to some or all of the through holes, the reliability of the solder joints can be further improved, and the reliability of the circuit board 200c can be improved.

[0052] From the above, it is possible to improve bonding reliability by having a circuit board in which the lead terminals of the electronic component are multiple, and auxiliary holes connected to through holes into which the lead terminals of at least one end of the electronic component are inserted. Embodiment 6. In Embodiment 5, auxiliary holes 5d and 5e were provided in the longitudinal direction of the electronic component 14a to be mounted, and a circuit board 200c in which the electronic component 14a was mounted was described. However, in Embodiment 6, auxiliary holes 5f and 5g were provided in the short direction of the electronic component 14a to be mounted, and the circuit board 200d was formed by mounting the electronic component 14a on a printed wiring board 100d. Embodiment 6 will only describe the parts that differ in configuration from Embodiment 5. Also, the same figure numbers will be used for configurations that are the same as or corresponding to those in Embodiment 5, and their descriptions will be omitted.

[0053] Figure 21 is a plan view of the printed circuit board 100d according to Embodiment 6, and Figure 22 is a cross-sectional view showing the A6-A6 cross section of the printed circuit board 100d. Figure 23 is a cross-sectional view at the same position as the A6-A6 cross section of the circuit board 200d according to Embodiment 6, in the fifth step of the manufacturing method of the circuit board 200d.

[0054] The auxiliary hole 5f of the auxiliary part 6f is connected to the through-hole 2a of the through-hole electrode 3a in the short-side direction of the electronic component 14a. The auxiliary hole 5g of the auxiliary part 6g is connected to the through-hole 2e of the through-hole electrode 3e in the short-side direction of the electronic component 14a.

[0055] After filling the through-holes 2a to 2e of the through-hole electrodes 3a to 3e, the auxiliary hole 5f of the auxiliary part 6f, and the auxiliary hole 5g of the auxiliary part 6g with solder paste, the lead terminals 15a to 15e of the electronic component 14a are inserted into the through-holes 2a to 2e of the through-hole electrodes 3a to 3e, respectively, and the solder joints 16a to 16e are formed by reflow heating.

[0056] Due to the difference in the coefficients of thermal expansion between the electronic component 14a and the substrate 1, the strain generated at the solder joint 16a to 16e increases in the longitudinal direction of the electronic component 14a. With the solder paste filled into the auxiliary holes 5f of the auxiliary part 6f and the auxiliary holes 5g of the auxiliary part 6g, according to the circuit board 200d of this embodiment 6, at the solder joint 16a, solder joints 16a with the through-hole electrodes 3a can be secured on both sides in the longitudinal direction of the electronic component 14a where the strain is greatest. Therefore, the reliability of the solder joint can be further improved compared to embodiment 5, and the reliability of the circuit board 200d can be improved. At the solder joint 16e, solder joints 16e with the through-hole electrodes 3e can be secured on both sides in the longitudinal direction of the electronic component 14a where the strain is greatest. Therefore, the reliability of the solder joint can be further improved compared to embodiment 5, and the reliability of the circuit board 200d can be improved.

[0057] Furthermore, auxiliary holes 5f and 5g are provided connected to the through holes 5a and 5e into which the lead terminals at both ends are inserted, respectively. By having auxiliary holes connected to the through holes into which the lead terminals at at least one end are inserted, it is possible to improve the reliability of the joints. Although auxiliary holes are not provided that connect to the inner walls of the through holes 2b to 2d, by having auxiliary holes connected to some or all of the through holes, the reliability of the solder joints can be further improved, and the reliability of the circuit board 200d can be improved.

[0058] Based on the above, it is possible to improve bonding reliability by having a circuit board in which the lead terminals of an electronic component are multiple, and auxiliary holes connected in the short direction of the electronic component to through holes into which the lead terminals of at least one end of the electronic component are inserted.

[0059] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0060] 1. Substrate, 2, 2a, 2b, 2c, 2d, 2e. Through-holes, 3, 3a, 3b, 3c, 3d, 3e. Through-hole electrodes, 4, 4a, 4b, 4c, 4d, 4e, 4f, 4g. Connection parts, 5, 5a, 5b, 5c, 5d, 5e, 5f, 5g. Auxiliary holes, 6, 6a, 6b, 6c, 6d, 6e, 6f, 6g. Auxiliary parts, 7. Inclined parts, 10. Metal mask, 11. Squeegee, 12, 13. Solder paste, 14, 14a. Electronic components, 15, 15a, 15b, 15c, 15d, 15e. Lead terminals, 16, 16a, 16b, 16c, 16d, 16e. Solder joints, 100, 100a, 100b, 100c, 100d Printed circuit boards, 200, 200a, 200b, 200c, 200d circuit boards.

Claims

1. A printed circuit board comprising: a through-hole electrode having a through-hole that penetrates from a first surface to a second surface opposite the first surface, the inner wall of the through-hole being made of a conductive material; and an auxiliary hole having an opening on the first surface and connected in a direction along the inner wall of the through-hole to the first surface, the material of the inner wall of the auxiliary hole being less solderable than the conductive material.

2. The printed circuit board according to claim 1, wherein the volume of the auxiliary hole is smaller than the volume of the through hole.

3. The printed circuit board according to claim 1 or 2, wherein the auxiliary hole penetrates from the first surface to the second surface.

4. The printed circuit board according to any one of claims 1 to 3, wherein the cross-section of the auxiliary hole parallel to the first surface is circular or elliptical.

5. The printed circuit board according to any one of claims 1 to 4, wherein the inner wall of the auxiliary hole is made of resin.

6. A circuit board comprising: a through-hole electrode having a through-hole that penetrates from a first surface of a printed wiring board to a second surface opposite the first surface, the inner wall of the through-hole being made of a conductive material; an auxiliary part having an opening on the first surface and connected in a direction along the inner wall of the through-hole to the first surface, the material of the inner wall of the auxiliary part being less solder-wettable than the conductive material; and an electronic component having a lead terminal inserted into the through-hole of the through-hole electrode and joined to the inner wall of the through-hole via solder.

7. The circuit board according to claim 6, wherein, in a cross-section parallel to the first surface, the width of the connection portion between the through hole and the auxiliary hole is smaller than the width of the lead terminal.

8. The circuit board according to claim 6 or 7, wherein the lead terminals of the electronic component are plurality, and the circuit board has auxiliary holes connected to the through holes into which the lead terminals of at least one end of the electronic component are inserted.

9. The circuit board according to claim 8, wherein the auxiliary holes are arranged in the short-side direction of the electronic component with respect to the connected through holes.

10. A method for manufacturing a circuit board on which electronic components are mounted, comprising: a through-hole electrode having a through-hole that penetrates from a first surface to a second surface opposite the first surface, the inner wall of the through-hole being made of a conductive material; and an auxiliary hole having an opening on the first surface and connected in a direction along the inner wall of the through-hole to the first surface, the material of the inner wall of the auxiliary hole being less solder-wettable than the conductive material, the method comprising: filling the through-hole and the auxiliary hole with solder paste via a mask having openings corresponding to the through-hole and the auxiliary hole; inserting the lead terminals of the electronic components into the solder paste filled in the through-hole; and reflow heating the solder paste filled in the through-hole and the auxiliary hole.

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