Printed circuit board manufacturing method

Abstract

To provide a manufacturing method of a print circuit board, in which a cream solder is easily pulled-off from a hole of a metal mask.SOLUTION: A manufacturing method of a print circuit board (1), includes steps of: generating a concave part (8) having copper foil parts (5D and 5E) in an open edge part by penetrating a first surface (1A) of the print circuit board 1 to an inner layer; housing a ceramic capacitor (9) into the concave part (8); establishing a state where the copper foil parts (5D and 5E) of the open edge part of the concave part (8) and the electrode parts (9A and 9B) of the ceramic capacitor (9) are located on the same flat surface, and printing a cream solder (10) onto electrode parts (9A and 9B) provided in the copper foil parts (5D and 5E) of the open end part of the concave part (8) and the ceramic capacitor (9); arranging and overlapping a ceramic capacitor (11) on the ceramic capacitor (9) housed in the concave part (8); melting the cream solder (10); and soldering the copper foil parts (5D and 5E) at the open edge part of the concave part (8), the electrode parts (9A and 9B) provided in the ceramic capacitor (9), and electrode parts (11A and 11B) provided in the ceramic capacitor (11).SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a printed circuit board on which electronic components are mounted. [Background technology]

[0002] Electronic components are generally mounted on a printed circuit board by soldering using a reflow method. For example, a multilayer board described in Patent Document 1 is provided with a recess that penetrates from the mounting surface to the inner layer, and electronic components housed in this recess are mounted on the multilayer board by soldering using a reflow method. In reflow soldering, cream solder is printed using a metal mask on the mounting portion where the electronic components are to be mounted.

[0003] Specifically, the holes in the metal mask are filled with solder paste while the metal mask is in close contact with the printed circuit board. The metal mask is then removed from the printed circuit board, and the solder paste passes through the holes in the metal mask and remains on the copper foil. The electrodes of the electronic components are placed in the solder paste remaining on the copper foil. The printed circuit board with the electronic components placed on it is passed through a reflow furnace to melt the solder paste and solder the electrodes of the electronic components to the copper foil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-311766 A Summary of the Invention [Problem to be solved by the invention]

[0005] When the metal mask is removed from the printed circuit board, whether the cream solder passes through the holes in the metal mask depends on the area of ​​the printed circuit board that the cream solder filled in the holes in the metal mask comes into contact with. For this reason, for example, when the area of ​​the copper foil portion is reduced in accordance with the miniaturization of electronic components, the area of ​​the copper foil portion that the cream solder comes into contact with also becomes smaller, which causes the cream solder to have difficulty passing through the holes in the metal mask.

[0006] This problem may also occur in the multilayer board described in Patent Document 1. For example, as electronic components become smaller, the recesses that house the electronic components become smaller, and the area of ​​the copper foil that solders the electrodes of the electronic components housed in the recesses becomes smaller, so the area with which the cream solder comes into contact also becomes smaller. This makes it difficult for the cream solder to fully escape through the holes in the metal mask. In particular, it is difficult to print the cream solder on the copper foil provided on the bottom surface of the recesses.

[0007] The present disclosure is devised to solve the above-mentioned problems, and aims to provide a method for manufacturing a printed circuit board that makes it easier for cream solder to pass through holes in a metal mask. [Means for solving the problem]

[0008] A method for manufacturing a printed circuit board according to the present disclosure includes the steps of: penetrating the first surface of a printed circuit board having a first surface and a second surface opposite to the first surface to an inner layer, thereby generating a recess having a copper foil portion at an opening edge portion; storing a first electronic component having an electrode portion in the recess, so that the copper foil portion at the opening edge portion of the recess and the electrode portion of the first electronic component are on the same plane; using a metal mask having a hole with an opening area including the area of ​​the copper foil portion at the opening edge of the recess and the area of ​​the upper surface side of the electrode portion of the first electronic component; The method includes the steps of printing cream solder on the copper foil portion on the opening edge of the recess and on the electrode portion of the first electronic component, placing a second electronic component having an electrode portion on top of the first electronic component housed in the recess, and melting the cream solder to solder the copper foil portion on the opening edge of the recess, the electrode portion of the first electronic component, and the electrode portion of the second electronic component. Effect of the Invention

[0009] According to the present disclosure, a first electronic component is accommodated in a recess provided in a printed circuit board, so that the copper foil portion of the opening edge of the recess and the electrode portion of the first electronic component are on the same plane, cream solder is printed on the copper foil portion of the opening edge of the recess and the electrode portion of the first electronic component, a second electronic component is placed on top of the first electronic component accommodated in the recess, and the cream solder is melted to solder the copper foil portion of the opening edge of the recess, the electrode portion of the first electronic component, and the electrode portion of the second electronic component. By printing the cream solder on the electrode portion of the first electronic component in addition to the copper foil portion provided on the printed circuit board, the surface area of ​​the printed circuit board side that comes into contact with the cream solder filled in the hole of the metal mask is increased. As a result, the method for manufacturing a printed circuit board according to the present disclosure can make it easier for the cream solder to come out of the hole of the metal mask. [Brief description of the drawings]

[0010] [Figure 1] FIG. 4 is a cross-sectional view showing a cross section of a printed circuit board in a state before a recess is formed. [Diagram 2] 1 is a cross-sectional view showing a cross section of a printed circuit board during laser processing to form a recess. [Diagram 3] FIG. 2 is a cross-sectional view showing a cross section of a printed circuit board on which a recess is formed. [Figure 4] 1 is a cross-sectional view showing a cross section of a printed circuit board in which a ceramic capacitor is housed in a recess. [Diagram 5] 10 is a cross-sectional view showing a cross section of a printed circuit board in which cream solder is printed on a copper foil portion at the opening edge of a recess and on an electrode portion of a ceramic capacitor housed in the recess. FIG. [Figure 6] 1 is a cross-sectional view showing a cross section of a printed circuit board in which a ceramic capacitor is arranged on top of another ceramic capacitor housed in a recess. [Figure 7] 1 is a cross-sectional view showing a cross section of a printed circuit board on which ceramic capacitors arranged above and below are soldered. [Figure 8]1 is an explanatory diagram showing a state in which cream solder flows between ceramic capacitors arranged above and below. [Figure 9] 1 is an explanatory diagram showing how electrode portions of ceramic capacitors arranged above and below are short-circuited with cream solder. FIG. [Figure 10] 1 is a cross-sectional view showing a cross section of a printed circuit board having a through-hole provided adjacent to a copper foil portion on which cream solder is printed. [Figure 11] 1 is a cross-sectional view showing a cross section of a printed circuit board on which a solder resist is applied except for the area around a copper foil portion on which cream solder is printed. [Figure 12] 12 is a top view showing the area around the copper foil portion in the printed circuit board of FIG. 11. FIG. [Figure 13] 1 is a top view showing the area surrounding the copper foil portion where the solder resist is not applied, and the path that guides the flux that has flowed out or leaked from the cream solder into the area and into the empty space on the first surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Embodiment 1 The method for manufacturing the printed circuit board 1 of embodiment 1 is a method for manufacturing a printed circuit board 1 on which electronic components are mounted and arranged vertically stacked, starting from the state shown in FIG. 1 described below, and passing through the states shown in FIGS. 2, 3, 4, 5, 6, and 7, respectively. Fig. 1 is a cross-sectional view showing a cross section of a printed circuit board 1 in a state before a recess is formed. In Fig. 1, the printed circuit board 1 is a multilayer printed circuit board in which a base material 2 and a prepreg 3 are alternately laminated, and has a first surface 1A and a second surface 1B opposite to the first surface 1A.

[0012] The substrate 2 is an insulating substrate. For example, a known substrate such as a glass epoxy substrate or a flexible substrate made of polyimide can be used as the substrate 2. The prepreg 3 is formed by thermally curing an insulating resin impregnated in a woven glass fabric or a nonwoven glass fabric. The through-hole 4 is configured to penetrate the printed circuit board 1 from the first surface 1A to the second surface 1B.

[0013] 1, a recess for accommodating electronic components is formed in the portion indicated by the symbol A. Copper foil portions 5A, 5B, and 5C are formed in the inner layer of the portion indicated by the symbol A, and copper foil portions 5D and 5E are formed on the first surface 1A side. In addition to these, copper foil portions 5 and 6 are formed on the first surface 1A of the printed circuit board 1, in the inner layer between the first surface 1A and the second surface 1B, and on the second surface 1B. The copper foil portion 5 is, for example, a pad made of copper foil, and the copper foil portion 6 is, for example, a wiring made of copper foil. The opening of the through hole 4 is provided near the copper foil portion 5D and the copper foil portion 5E on the first surface 1A.

[0014] Fig. 2 is a cross-sectional view showing a cross section of the printed circuit board 1 during laser processing to form a recess 8. Fig. 3 is a cross-sectional view showing a cross section of the printed circuit board 1 with a recess 8 formed therein. Fig. 4 is a cross-sectional view showing a cross section of the printed circuit board 1 with a ceramic capacitor 9 housed in the recess 8. As shown in Fig. 4, the ceramic capacitor 9 is a surface-mount type first electronic component having an electrode portion 9A and an electrode portion 9B. In addition, in the manufacturing method of printed circuit board 1 according to embodiment 1, the first electronic component to be stored in recess 8 is not limited to a ceramic capacitor, but may be any surface-mount electronic component having two electrodes.

[0015] A laser processing machine 7 shown in FIG. 2 removes the base material 2 and the prepreg 3 by irradiating the printed circuit board 1 with laser light B, thereby performing countersinking on the printed circuit board 1. The countersink portion formed by the laser processing machine 7 is a recess 8 formed in the portion indicated by reference symbol C in FIG. 3. The laser light B is totally reflected by the copper foil portions 5A, 5B, and 5C in the inner layers of the printed circuit board 1. Therefore, the copper foil portions 5A, 5B, and 5C are not removed by the laser light B. In the method for manufacturing the printed circuit board 1 according to the first embodiment, this characteristic is utilized to form the recess 8.

[0016] The copper foil portions 5A and 5B are formed in an inner layer at a depth substantially equal to the height of the ceramic capacitor 9, with a distance substantially equal to the distance between the electrode portions 9A and 9B of the ceramic capacitor 9. The copper foil portion 5C is formed in an inner layer at a position deeper than the height of the ceramic capacitor 9, at a position corresponding to the gap between the copper foil portions 5A and 5B. The copper foil portions 5D and 5E are formed on the first surface 1A with a distance equivalent to the width including the electrode portions 9A and 9B of the ceramic capacitor 9.

[0017] 2 is a depth at which the height of the ceramic capacitor 9 housed in the recess 8 is flush with the first surface 1A including the copper foil portion 5D and the copper foil portion 5E, as indicated by the symbol D in Fig. 4. For example, the copper foil portion 5A and the copper foil portion 5B are provided on the same inner layer surface at the position of the countersinking depth D1 in the inner layer of the printed circuit board 1 so that the upper surface of the ceramic capacitor 9 housed in the recess 8 is horizontal.

[0018] Note that the countersink depth D1 includes a deviation within an allowable range that takes into consideration the allowable processing error of the laser processing machine 7 and the individual difference of the ceramic capacitor 9. In other words, it is sufficient that the upper surfaces of the copper foil portions 5D and 5E and the upper surface of the ceramic capacitor 9 are approximately on the same plane.

[0019] Ceramic capacitor 9 is a surface-mount electronic component with electrode portion 9A and electrode portion 9B formed on both sides of the component body. By storing ceramic capacitor 9 in recess 8, electrode portion 9A and electrode portion 9B are exposed from first surface 1A of printed circuit board 1 as shown in Fig. 4, with electrode portion 9A in contact with copper foil portion 5A and electrode portion 9B in contact with copper foil portion 5B. Although the manufacturing method for the printed circuit board 1 according to the first embodiment does not particularly specify the potentials of the copper foil portions 5A and 5B, the copper foil portions 5A and 5B are in contact with the electrode portions 9A and 9B, respectively. For this reason, it is preferable that the potentials of the copper foil portions 5A and 5B are set to the same potential as those of the electrode portions 9A and 9B.

[0020] 2 may be deeper than the inner layer in which the copper foil portion 5A and the copper foil portion 5B are formed. That is, the area between the copper foil portion 5A and the copper foil portion 5B is further countersunk to the countersink depth D2. As a result, as shown in FIG. 3, a part of the recess 8 is formed between the copper foil portion 5A and the copper foil portion 5B. When the ceramic capacitor 9 is stored in the recess 8, the electrode portion 9A contacts the copper foil portion 5A, and the electrode portion 9B contacts the copper foil portion 5B. Therefore, by having a part of the recess 8 between the copper foil portion 5A and the copper foil portion 5B, it is possible to prevent the electrode portion 9A and the electrode portion 9B from being short-circuited.

[0021] After the ceramic capacitor 9 is placed in the recess 8, solder paste printing is performed. In the conventional technology, in order to solder a copper foil portion formed on a printed circuit board to an electrode portion of an electronic component, cream solder is printed only on the copper foil portion. Therefore, when the area of ​​the copper foil portion is reduced as the electronic component becomes smaller, the cream solder that is in contact only with the copper foil portion cannot escape through the holes in the metal mask.

[0022] For example, when the electronic component to be mounted is a ceramic capacitor, small ceramic capacitors include extremely small components such as 0603 chip (0.6 mm×0.3 mm) or 0402 chip (0.4 mm×0.2 mm). In the conventional technology described in Patent Document 1, in order to mount an electronic component in a recess provided in a multilayer printed circuit board, cream solder is printed on a copper foil portion formed on the opening edge and bottom of the recess. However, when the electronic component to be mounted in the recess is an extremely small component as described above, a recess and copper foil portion of a size that matches the extremely small component are formed in the printed circuit board, and a hole in the metal mask is also formed according to the size of the copper foil portion. As a result, the cream solder may not pass through the hole in the metal mask, making it impossible to print the cream solder on the copper foil portion.

[0023] Therefore, the manufacturing method of the printed circuit board 1 of embodiment 1 uses the printed circuit board 1 having the copper foil portions 5A-5E formed thereon as described above, and prints cream solder not only on the copper foil portion 5D and the copper foil portion 5E formed on the first surface 1A, but also on the electrode portions 9A and 9B exposed from the first surface 1A. Even if the areas of copper foil portions 5D and 5E are reduced as ceramic capacitor 9 is made smaller, the metal mask has holes whose opening areas include the area of ​​copper foil portion 5D and the area of ​​the upper surface side of electrode portion 9A, and holes whose opening areas include the area of ​​copper foil portion 5E and the area of ​​the upper surface side of electrode portion 9B. This ensures an area for the cream solder to contact the printed circuit board 1, so the manufacturing method for printed circuit board 1 according to embodiment 1 makes it easier for the cream solder to pass through the holes in the metal mask.

[0024] Fig. 5 is a cross-sectional view showing a cross section of the printed circuit board 1 on which cream solder 10 is printed on copper foil parts 5D and 5E at the opening edge part of the recess 8 and on electrode parts 9A and 9B of the ceramic capacitor 9 housed in the recess 8. The copper foil parts 5D and 5E shown in Fig. 5 are copper foil parts for soldering the electrode parts of the ceramic capacitor 11, which will be described later with reference to Fig. 6, to the printed circuit board 1 side. The metal mask (not shown in Fig. 5) used for printing the cream solder 10 is usually made of stainless steel and has a variety of thicknesses, but is generally any of 130 μm, 120 μm, 100 μm, and 80 μm.

[0025] The metal mask has holes of a wide variety of shapes for printing the cream solder 10 on the side of the printed circuit board 1. The amount of cream solder 10 printed on the side of the printed circuit board 1 can be adjusted by changing the thickness of the metal mask, the shape of the holes, and the opening area of ​​the holes. In printing the cream solder 10, the metal mask is brought into close contact with the first surface 1A of the printed circuit board 1, and the cream solder 10 is filled into the holes in the metal mask using a special squeegee.

[0026] In the manufacturing method of the printed circuit board 1 according to the first embodiment, the metal mask has holes with an opening area equal to the sum of the areas of the upper surfaces of the copper foil portion 5D and the electrode portion 9A, and the sum of the areas of the upper surfaces of the copper foil portion 5E and the electrode portion 9B. By using this metal mask, the cream solder 10 contacts the upper surfaces of the copper foil portion 5D and the electrode portion 9A through the holes in the metal mask, and contacts the upper surfaces of the copper foil portion 5E and the electrode portion 9B, so that the contact area of ​​the cream solder 10 is sufficiently secured. Therefore, even if the metal mask is removed from the first surface 1A, the cream solder 10 passes through the holes in the metal mask and remains on the upper surfaces of the copper foil portion 5D and the electrode portion 9A, as shown in FIG. 5, and further remains on the upper surfaces of the copper foil portion 5E and the electrode portion 9B.

[0027] Fig. 6 is a cross-sectional view showing a cross section of printed circuit board 1 in which ceramic capacitor 11 is arranged overlapping ceramic capacitor 9 housed in recess 8. In Fig. 6, ceramic capacitor 11 is a second electronic component arranged overlapping on the upper surface of ceramic capacitor 9 housed in recess 8. When cream solder 10 is printed, ceramic capacitor 11 is arranged on the upper surface of ceramic capacitor 9 housed in recess 8 with electrode portions overlapping each other.

[0028] 6, for example, electrode portion 11A of ceramic capacitor 11 is disposed above electrode portion 9A of ceramic capacitor 9, with cream solder 10 interposed therebetween. Similarly, electrode portion 11B of ceramic capacitor 11 is disposed above electrode portion 9B of ceramic capacitor 9, with cream solder 10 interposed therebetween. In this way, ceramic capacitor 11 is disposed in a state overlapping ceramic capacitor 9. The printed circuit board 1 with ceramic capacitor 11 disposed above ceramic capacitor 9 is carried into a reflow furnace.

[0029] 7 is a cross-sectional view showing a cross section of the printed circuit board 1 on which the ceramic capacitor 9 and the ceramic capacitor 11 arranged above and below are soldered. The printed circuit board 1 in the state shown in FIG. 6 is carried into a reflow furnace (not shown in FIG. 7) and heated to melt the cream solder 10. Thereafter, the printed circuit board 1 is carried out of the reflow furnace. As the molten solder solidifies, the copper foil portion 5D is soldered to the electrode portion 9A and the electrode portion 11A, and the copper foil portion 5E is soldered to the electrode portion 9B and the electrode portion 11B, as shown in FIG. 7.

[0030] The solder paste 10 is a mixture of solder powder and flux in approximately half. When the solder paste 10 is melted, the flux liquefies before the solder powder. The liquefied flux removes the oxide film on the surfaces of the copper foil and electrodes, and also reduces the surface tension of the liquefied solder caused by the melting of the solder powder.

[0031] When the cream solder 10 melts and the ceramic capacitor 11 sinks toward the ceramic capacitor 9 under its own weight, the solder powder melts and the liquefied solder overflows from between the electrodes. The solder that overflows from between the electrodes flows into the copper foil portion 5D, the electrode portion 9A, and the electrode portion 11A, as well as into the side portion of the electrode portion 9A, and into the copper foil portion 5E, the electrode portion 9B, and the electrode portion 11B, as well as into the side portion of the electrode portion 9B.

[0032] When the liquefied solder cools and solidifies, the solder joint 10A between the copper foil portion 5D and the electrode portion 9A and the electrode portion 11A becomes a fillet shape, as shown by the symbol E in Fig. 7. Similarly, the solder joint 10B between the copper foil portion 5E and the electrode portion 9B and the electrode portion 11B also becomes a fillet shape.

[0033] When the solder joints 10A and 10B have a fillet shape, the solder, the copper foil, and the electrodes are sufficiently melted, and the metal materials that make them up are intermetallic bonded. Therefore, in the manufacturing method for printed circuit board 1 according to the first embodiment, in a visual inspection after soldering, it is determined whether the solder joints 10A and 10B have an appropriate fillet shape.

[0034] For example, a laser beam is irradiated onto the outer surface of the solder joint, and the angle of reflection of the laser beam from the outer surface of the solder joint is analyzed to determine whether or not the fillet shape is properly formed. Note that the solder joints 10A and 10B are exposed from the first surface 1A of the printed circuit board 1. Therefore, in the method for manufacturing the printed circuit board 1 according to the first embodiment, it is possible to determine the presence or absence of the fillet shape of the solder joint by visual inspection.

[0035] Fig. 8 is an explanatory diagram showing how cream solder 10 flows between ceramic capacitors 9 and 11 arranged vertically. Fig. 9 is an explanatory diagram showing how the electrodes of ceramic capacitors 9 and 11 arranged vertically are short-circuited by cream solder 10. As described above, cream solder 10 exists between ceramic capacitors 9 and 11 arranged vertically one above the other.

[0036] When the cream solder 10 melts, as described above, the flux contained in the cream solder 10 liquefies. If there is no area through which the liquefied flux flows in the area around the copper foil parts 5D and 5E on which the cream solder 10 is printed, the liquefied flux will remain on the upper surfaces of the copper foil parts 5D and 5E.

[0037] When the solder powder contained in the solder cream 10 melts, liquefied solders 10a and 10b are generated. The flux reduces the surface tension of the solders 10a and 10b, improving their fluidity, and the solders 10a and 10b flow from the upper surfaces of the copper foil portions 5D and 5E in the directions indicated by arrows F in FIG.

[0038] The solder 10a and the solder 10b that flow between the ceramic capacitor 9 and the ceramic capacitor 11 are cooled and solidified to form the solder joint 10c shown in Fig. 9. The solder joint 10c electrically connects the electrode portion 9A, the electrode portion 9B, the electrode portion 11A, and the electrode portion 11B, and therefore shorts out the electrode where the electrode portion 9A and the electrode portion 11A are connected and the electrode where the electrode portion 9B and the electrode portion 11B are connected.

[0039] Therefore, the method for manufacturing the printed circuit board 1 according to the first embodiment uses the printed circuit board 1 provided with a structure for flowing the flux generated from the cream solder 10 printed on the copper foil parts 5D and 5E to a target part. The structure for flowing the flux to a target part is, for example, a structure in which a through-hole is provided adjacent to the copper foil part on which the cream solder is printed.

[0040] Fig. 10 is a cross-sectional view showing a cross section of a printed circuit board 1 having a through-hole 4 provided adjacent to a copper foil portion 5E on which cream solder 10 is printed. When the printed circuit board 1 in the state shown in Fig. 10 is carried into a reflow furnace and heated, the flux contained in the cream solder 10 liquefies. The liquefied flux flows from the upper surface of the copper foil portion 5E in the direction shown by arrow G in Fig. 10, and flows into the opening of the through-hole 4 provided adjacent to the copper foil portion 5E.

[0041] The solder powder contained in the solder paste 10 melts and becomes liquid, but the liquid solder does not flow between the ceramic capacitors 9 and 11, but is guided to the path along which the flux flowed. The liquid solder cools and solidifies to form a solder joint 10B that connects the copper foil portion 5E and the electrode portion 9B and the electrode portion 11B.

[0042] 10, an area where the base material 2 is exposed is provided between the copper foil portion 5D and the adjacent copper foil portion 5, and the flux generated by melting the cream solder 10 printed on the copper foil portion 5D flows into that area. However, in the printed circuit board 1, a through hole adjacent to the copper foil portion 5D may be provided, similar to the copper foil portion 5E. Even with the printed circuit board 1 configured in this manner, it is possible to prevent the formation of a solder joint that shorts out the electrode connecting electrode portion 9A and electrode portion 11A and the electrode connecting electrode portion 9B and electrode portion 11B.

[0043] The structure for flowing flux to a target portion may be, for example, a structure in which the area around copper foil portion 5D and copper foil portion 5E is made an area where base material 2 of printed circuit board 1 is exposed, and solder resist is provided around this area. Solder resist is usually applied to printed circuit board 1 for the purpose of preventing oxidation of the copper foil portion. 11 is a cross-sectional view showing a cross section of the printed circuit board 1 on which the solder resist 12 is applied except for the areas around the copper foil portion 5D and the copper foil portion 5E on which the cream solder 10 is printed. The areas around the copper foil portion 5D and the copper foil portion 5E are not coated with the solder resist 12, and the base material 2 of the printed circuit board 1 is exposed.

[0044] The flux that has been liquefied by melting the cream solder 10 flows in the direction indicated by the symbol H in Fig. 11 and flows into the area where the base material 2 of the printed circuit board 1 is exposed. Fig. 12 is a top view showing area I around the copper foil portion 5D and the copper foil portion 5E in the printed circuit board 1 of Fig. 11. The through-holes 4 are not shown in Fig. 12. Area I around the copper foil portion 5D and the copper foil portion 5E is the area into which the flux that has been liquefied by melting the cream solder 10 flows. 12, the area I around the copper foil portion 5D and the copper foil portion 5E is an area where the distance between the copper foil portion 5D and the copper foil portion 5E on which the cream solder 10 is printed and the solder resist 12 is D0, and the base material 2 of the printed circuit board 1 is exposed. In general, when applying a solder resist around a copper foil portion on which an electronic component is mounted, the copper foil portion and the solder resist are separated by a distance D0 of, for example, 50 μm to 100 μm, rather than being brought into contact with the copper foil portion. In the printed circuit board 1 used in the manufacturing method of the printed circuit board 1 according to the first embodiment, this distance D0 is further increased to form an area for storing liquefied flux.

[0045] The solder powder contained in the solder cream 10 melts and becomes liquid, but the liquid solder does not flow between the ceramic capacitors 9 and 11, but is guided to the region I into which the flux has flowed. The liquid solder cools and solidifies to form a solder joint 10B that connects the copper foil portion 5E and the electrode portion 9B and the electrode portion 11B.

[0046] 13 is a top view showing an area I around the copper foil portion 5D and the copper foil portion 5E where the solder resist 12 is not applied, and a path 12A connected to the area I, and shows the area around the through-hole 4 which is omitted in FIG. 12. As shown in FIG. 13, the path 12A is connected to the area I around the copper foil portion 5D and the copper foil portion 5E where the cream solder 10 is printed. A copper foil portion 4A is provided on the opening edge of the through-hole 4. The opening of the through-hole 4 functions as an empty space for the outflow of liquefied flux that has flowed out or leaked from the cream solder 10.

[0047] When the cream solder 10 printed on the copper foil portion 5D and the copper foil portion 5E melts, liquefied flux is generated. The liquefied flux flows into the region I around the copper foil portion 5D and the copper foil portion 5E, and further flows along the path 12A in the direction indicated by the arrow J in FIG. 13. The flux then flows through the copper foil portion 4A and out of the opening of the through hole 4 toward the second surface 1B. As a result, the solder powder contained in the cream solder 10 melts and the liquefied solder does not flow between the ceramic capacitor 9 and the ceramic capacitor 11, but is guided to the region I into which the flux has flowed. The liquefied solder is cooled and solidified to form a solder joint 10B that connects the copper foil portion 5E to the electrode portion 9B and the electrode portion 11B.

[0048] As described above, the manufacturing method of printed circuit board 1 according to embodiment 1 involves storing ceramic capacitor 9 in recess 8 provided in printed circuit board 1, so that copper foil portions 5D and 5E at the opening edge of recess 8 and electrode portions 9A and 9B of ceramic capacitor 11 are on the same plane, printing cream solder 10 on copper foil portions 5D and 5E at the opening edge of recess 8 and electrode portions 9A and 9B of ceramic capacitor 9, placing ceramic capacitor 11 on top of ceramic capacitor 9 stored in recess 8, and melting cream solder 10 to solder copper foil portions 5D and 5E at the opening edge of recess 8, electrode portions 9A and 9B of ceramic capacitor 9, and electrode portions 11A and 11B of ceramic capacitor 11. By printing cream solder 10 on electrode portion 9A and electrode portion 9B of ceramic capacitor 9, in addition to copper foil portion 5D and copper foil portion 5E provided on printed circuit board 1, the surface area of ​​the printed circuit board 1 with which cream solder 10 comes into contact is increased. This makes it easier for cream solder 10 to pass through holes in the metal mask in the manufacturing method for printed circuit board 1 according to embodiment 1.

[0049] In the manufacturing method of the printed circuit board 1 according to the first embodiment, the solder joint 10A between the copper foil part 5D at the opening edge of the recess 8, the electrode part 9A of the ceramic capacitor 9, and the electrode part 11A of the ceramic capacitor 11 is in a fillet shape. The solder joint 10B between the copper foil part 5E at the opening edge of the recess 8, the electrode part 9B of the ceramic capacitor 9, and the electrode part 11B of the ceramic capacitor 11 is in a fillet shape. By visually inspecting whether the solder joint 10A and the solder joint 10B are in a fillet shape, it can be determined whether the solder joint 10A and the solder joint 10B are appropriately formed.

[0050] In the method for manufacturing printed circuit board 1 according to the first embodiment, through-hole 4 is provided adjacent to at least one of copper foil portion 5D or copper foil portion 5E on which cream solder 10 is printed, penetrating printed circuit board 1 from first surface 1A to second surface 1B. This makes it possible to prevent the formation of a solder joint that shorts out an electrode where electrode portion 9A and electrode portion 11A are connected and an electrode where electrode portion 9B and electrode portion 11B are connected.

[0051] In the method for manufacturing the printed circuit board 1 according to the first embodiment, the solder resist 12 is applied except for the area I around the copper foil portion 5D and the copper foil portion 5E on which the cream solder 10 is printed, and the base material 2 of the printed circuit board 1 is exposed in the area I around the copper foil portion 5D and the copper foil portion 5E on which the solder resist 12 is not applied. The liquefied flux flows into the area I, thereby preventing the formation of a solder joint that shorts out the electrode where the electrode portion 9A and the electrode portion 11A are connected and the electrode where the electrode portion 9B and the electrode portion 11B are connected.

[0052] In the method for manufacturing printed circuit board 1 according to the first embodiment, a path 12A that guides flux to the opening of through-hole 4, which is an empty space on first surface 1A, is connected to area I around copper foil portion 5D and copper foil portion 5E where solder resist 12 is not applied. When liquefied flux flows into the opening of through-hole 4, it is possible to prevent the formation of a solder joint that shorts out the electrode where electrode portion 9A and electrode portion 11A are connected and the electrode where electrode portion 9B and electrode portion 11B are connected.

[0053] Any of the components of the embodiments may be modified or omitted. [Explanation of symbols]

[0054] 1 printed circuit board, 1A first surface, 1B second surface, 2 base material, 3 prepreg, 4 through hole, 4A, 5, 5A to 5E, 6 copper foil portion, 7 laser processing machine, 8 recess, 9, 11 ceramic capacitor, 9A, 9B, 11A, 11B electrode portion, 10 cream solder, 10A, 10B, 10c solder joint portion, 10a, 10b solder, 12 solder resist, 12A path.

Claims

1. a step of forming a recess having a copper foil portion on an opening edge portion by penetrating the first surface of a printed circuit board to an inner layer, the printed circuit board having a first surface and a second surface opposite to the first surface; a step of housing a first electronic component having an electrode portion in the recess so that a copper foil portion on an edge of an opening of the recess and the electrode portion of the first electronic component are on the same plane; printing cream solder onto the copper foil portion of the opening edge of the recess and onto the electrode portion of the first electronic component using a metal mask having a hole with an opening area including an area of ​​the copper foil portion of the opening edge of the recess and an area of ​​an upper surface side of the electrode portion of the first electronic component; placing a second electronic component having an electrode portion on the first electronic component housed in the recess; and a step of melting the cream solder to solder the copper foil portion at the opening edge of the recess, the electrode portion of the first electronic component, and the electrode portion of the second electronic component. A method for manufacturing a printed circuit board comprising the steps of:

2. The solder joints between the copper foil portion at the opening edge of the recess, the electrode portion of the first electronic component, and the electrode portion of the second electronic component have a fillet shape.

2. The method for manufacturing a printed circuit board according to claim 1.

3. a through hole provided adjacent to the copper foil portion on which the cream solder is printed and configured to penetrate the printed circuit board from the first surface to the second surface; 3. The method for manufacturing a printed circuit board according to claim 1 or 2.

4. applying a solder resist to an area other than the area surrounding the copper foil portion on which the cream solder is printed; In the area around the copper foil portion where the solder resist is not applied, the base material of the printed circuit board is exposed. The method for manufacturing a printed circuit board according to any one of claims 1 to 3.

5. A path for conducting flux to an empty space on the first surface is connected to the area surrounding the copper foil portion on which the solder resist is not applied.

5. The method for manufacturing a printed circuit board according to claim 4.

6. The first electronic component and the second electronic component are surface-mount ceramic capacitors. The method for manufacturing a printed circuit board according to any one of claims 1 to 4.

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