JP2019102480A - Printed wiring board manufacturing method - Google Patents

Abstract

To provide a printed wiring board manufacturing method which can more successfully inhibit outflow of a solder paste supplied to the inside of a through hole.SOLUTION: A printed wiring board manufacturing method comprises the steps of: forming a step-like part 7a on a substrate 1 where a through hole 2 is formed; arranging a solder paste 9b inside the through hole 2; inserting a lead 10b of an insertion mounting component 10 in the through hole 2 where the solder paste 9b is arranged; and melting the solder paste 9b by heat application to fix the lead 10b to the substrate 1. In the step of inserting the lead 10b, the lead 10b is inserted from an upper principal surface 1a side in a vertical direction of the substrate 1 toward a lower principal surface 1b side in the vertical direction opposite to the upper principal surface 1a. The step-like part 7a is formed in a region adjacent to the through hole 2 on the lower principal surface 1b of the substrate 1 so as to extend downward from the lower principal surface 1b.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a method of manufacturing a printed wiring board, and more particularly, to a method of manufacturing a printed wiring board mounted by heating a solder paste inserted into a through hole after inserting solder paste into the through hole. It is.

  A technique for filling a through hole with a solder paste, inserting a lead of an insertion mounting component into the through hole, and thermally mounting it is disclosed, for example, in Japanese Patent Laid-Open No. 5-75245 (Patent Document 1). In Japanese Patent Application Laid-Open No. 5-75245, an insulating sheet is attached to a region adjacent to a through hole in one of the main surfaces of a printed wiring board. The insulating sheet blocks the outflow of the solder paste. Thereby, the bridge failure due to the solder paste flowing out of the through hole is suppressed.

Unexamined-Japanese-Patent No. 5-75245

  The lead 22 on the left side of FIG. 2 of JP-A-5-75245 is inserted from the lower side to the upper side in the vertical direction. In such a case, even if the insulating sheet 24 is not disposed around the upper through hole which is the side to be inserted, the outflow of the solder paste is suppressed to some extent. However, the lead 16 on the right side of FIG. 2 of JP-A-5-75245 is inserted from the upper side to the lower side in the vertical direction. In this case, it is feared that the amount of solder paste flowing out on the lower main surface of the printed wiring board will be larger than when the leads are inserted from the lower side to the upper side. The reason is that downward gravity is applied to the solder paste. However, in Japanese Patent Application Laid-Open No. 5-75245, the insulating sheet is not attached on the lower main surface of the printed wiring board. That is, no member is provided to block the flow of solder paste from the through hole to the outside. Therefore, when inserting the lead 16, a large amount of solder paste may flow downward due to gravity and may flow out onto the lower major surface of the printed wiring board.

  The present invention has been made in view of the above problems. An object of the present invention is to provide a method of manufacturing a printed wiring board capable of more reliably suppressing the outflow of solder paste supplied into through holes.

  The method for producing a printed wiring board of the present invention comprises the following steps. A stepped portion is formed on the substrate in which the through hole is formed. Solder paste is placed in the through holes. The lead of the insertion mounting part is inserted into the through hole in which the solder paste is arranged. The solder paste is melted by heating to fix the leads to the substrate. In the step of inserting the leads, the leads are inserted from the upper main surface side in the vertical direction of the substrate toward the lower main surface side in the vertical direction opposite to the upper main surface. The stepped portion is formed to extend downward from the lower main surface in a region adjacent to the through hole on the lower main surface of the substrate.

  According to the present invention, the stepped portion is formed in the region adjacent to the through hole on the lower main surface in the vertical direction of the substrate. The stepped portion blocks the outflow of the solder paste. For this reason, the outflow of the solder paste in the through hole can be more reliably suppressed because the lead is inserted from the upper side to the lower side in the through hole.

FIG. 7 is a schematic cross-sectional view showing a first step of a method of manufacturing a printed wiring board in Embodiment 1. FIG. 7 is a schematic cross-sectional view showing a second step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 7 is a schematic cross-sectional view showing a third step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 14 is a schematic cross-sectional view showing a fourth step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 14 is a schematic cross-sectional view showing a fifth step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 14 is a schematic cross-sectional view showing a sixth step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 14 is a schematic cross-sectional view showing a seventh step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 14 is a schematic cross-sectional view showing an eighth step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 14 is a schematic cross-sectional view showing a ninth step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 16 is a schematic cross-sectional view showing a tenth step of the method of manufacturing a printed wiring board in the first embodiment. FIG. 2 is a schematic cross-sectional view showing the main part of the finished product of the printed wiring board in Embodiment 1. FIG. 12 is a schematic plan view of the structure shown in FIG. 11 in the first embodiment as viewed from the direction indicated by arrow A. It is a schematic sectional drawing corresponding to FIG. 7 of the manufacturing method of the printed wiring board in a comparative example. It is a schematic sectional drawing corresponding to FIG. 8 of the manufacturing method of the printed wiring board in a comparative example. It is a schematic sectional drawing which shows the principal part of the finished product of the printed wiring board in a comparative example. FIG. 14 is a schematic plan view of the structure shown in FIG. 11 in Embodiment 2 as seen from the direction indicated by arrow A. FIG. 16 is a schematic plan view showing an outflow aspect of the solder paste in the through hole in the second embodiment. FIG. 18 is a schematic cross-sectional view showing the main part of the finished product of the printed wiring board in Embodiment 3. FIG. 19 is a schematic plan view of the structure shown in FIG. 18 in Embodiment 3 as seen from the direction indicated by arrow B.

Hereinafter, embodiments will be described based on the drawings.
Embodiment 1
The manufacturing method of the printed wiring board of this Embodiment is demonstrated using FIGS. 1-10. Referring to FIG. 1, first, a substrate 1 as a base of a printed wiring board is prepared. The substrate 1 has, for example, an upper major surface 1a rectangular in plan view and a lower major surface 1b opposite thereto. Here, the upper main surface 1a means the upper main surface in the vertical direction of the substrate 1, and in particular means the main surface disposed on the upper side in the step of inserting the lead into the through hole described later. Here, the lower main surface 1b means the lower main surface in the vertical direction of the substrate 1, and in particular means the lower main surface disposed in the step of inserting the lead into the through hole described later. The thickness of the substrate 1 can be defined by the distance between the upper major surface 1a and the lower major surface 1b. The thickness of the substrate 1 is substantially constant throughout.

  The substrate 1 is made of, for example, a material in which a glass cloth contains an epoxy resin. However, the substrate 1 is not limited to this, and the substrate 1 may be formed of a material in which a glass nonwoven fabric or a paper substrate is impregnated with a polyimide resin or a phenol resin.

  First, processing is performed to form the through hole 2 at a desired position of the substrate 1. The through hole 2 is a hole formed to penetrate the substrate 1. The through holes 2 are formed to extend from the upper major surface 1a to the lower major surface 1b in a direction substantially orthogonal to the upper major surface 1a and the lower major surface 1b.

  Referring to FIG. 2, conductive layer 3 is formed on the inner wall surface of through hole 2. The conductive layer 3 is, for example, a thin film of copper and is preferably formed by plating. As shown in FIG. 2, conductive layer 3 may extend from the inner wall surface of through hole 2 so as to run on portions of upper main surface 1 a and lower main surface 1 b adjacent to through hole 2. Further, on the upper main surface 1a and the lower main surface 1b of the substrate 1, a resist 4 as a generally known photosensitive agent is applied. However, as shown in FIG. 2, when the conductive layer 3 rides on the upper main surface 1a and the lower main surface 1b, the resist 4 is applied to the region adjacent to the conductive layer 3 (the region outside the conductive layer 3). Is preferred.

  Referring to FIG. 3, the upper and lower sides of substrate 1 are inverted, and lower main surface 1b is arranged above the upper main surface 1a in the vertical direction. Next, a mask, that is, a metal mask 5 is placed on the lower major surface 1b of the substrate 1. A metal mask 5 may be placed on the resist 4 covering the lower main surface 1b.

  The metal mask 5 is a member having, for example, a rectangular planar shape having one main surface and the other main surface opposite thereto. The metal mask 5 has an opening 6a formed to penetrate therethrough. The opening 6 a is formed to extend from the one main surface of the metal mask 5 to the other main surface in a direction substantially orthogonal to the one main surface and the other main surface. The metal mask 5 is disposed such that the opening 6 a is disposed in an area other than the area overlapping the through hole 2 in plan view. It is preferable that the opening 6 a of the metal mask 5 be disposed so as to overlap the area adjacent to the outside of the through hole 2 in particular. However, as shown in FIG. 3, when conductive layer 3 is formed in the region adjacent to the outside of through hole 2 of upper main surface 1a and lower main surface 1b, the region adjacent to the outside of conductive layer 3 (resist 4 Preferably, the metal mask 5 is disposed such that the opening 6a is disposed in the area overlapping the above.

  Referring to FIG. 4, the printing material is supplied to fill opening 6a of metal mask 5 (mask). Specifically, ink 7 containing a thermosetting resin such as epoxy resin, for example, as a printing material is applied on the main surface of metal mask 5 in the vertical direction upper side (opposite to the side on which substrate 1 is disposed) Ru. An ink 7 containing an acrylic resin or a silicone resin may be used instead of the epoxy resin. In this state, the squeegee 8 is moved in the direction M indicated by the arrow in the figure with the squeegee 8 partially in contact with the main surface of the metal mask 5. Thereby, the squeegee 8 spreads the applied ink 7 on the surface of the metal mask 5. At this time, the ink 7 is filled in the opening 6 a of the metal mask 5.

  Thereafter, metal mask 5 is removed from lower main surface 1b. Thereby, the ink 7 is formed as a pattern in a partial region on the resist 4. Next, the substrate 1 is put into a high temperature furnace such as a reflow furnace and heated to 250 ° C. Thus, the ink 7 is cured as a pattern of silk 7a made of a material containing an epoxy resin. The silk 7a is formed on the lower main surface 1b or the resist 4 thereon, and extends from the lower main surface 1b of the substrate 1 to the lower side (the upper side because it is reversed in FIG. 4) It is formed. The pattern of silk 7a is formed in the area adjacent to (the outside of) the through hole 2. However, as shown in FIG. 4, silk 7 a may be formed in the area adjacent to the outside of conductive layer 3 in the area adjacent to through hole 2 on lower main surface 1 b of substrate 1. Here, the region adjacent to the through hole 2 includes not only the region immediately outside the through hole 2 itself but also the region adjacent to the outer side of the conductive layer 3 outside the through hole 2. The pattern of silk 7a as the step portion is formed by the silk screen printing method described above. As described above, a pattern of silk 7 a as a stepped portion is formed on the substrate 1 in which the through holes 2 are formed.

  Although not shown, in the present embodiment, the silk 7a is preferably formed so as to surround the entire region adjacent to the through hole 2 in a plan view.

  Referring to FIG. 5, the upper and lower sides of substrate 1 are inverted, and upper main surface 1a is again disposed above the lower main surface 1b in the vertical direction. Next, a mask, that is, a metal mask 5 is placed on the upper major surface 1 a of the substrate 1. A metal mask 5 may be placed on the resist 4 covering the upper main surface 1a.

  The metal mask 5 here is also a member having, for example, a rectangular planar shape having one main surface and the other main surface on the opposite side, as the metal mask 5 described above. The metal mask 5 has an opening 6b formed to penetrate therethrough. The opening 6 b is formed to extend from the one main surface of the metal mask 5 to the other main surface in a direction substantially orthogonal to the one main surface and the other main surface. The metal mask 5 is disposed such that the opening 6 b is disposed in a region overlapping with the through hole 2 in plan view. The opening 6b may be arranged to overlap in a planar manner both the through hole 2 and the region where the conductive layer 3 has climbed over the outer upper main surface 1a and the lower main surface 1b.

  The metal mask 5 of FIG. 5 is formed of, for example, SUS, and has a thickness of, for example, 150 μm. It is preferable that the said thickness is 100 micrometers or more and 200 micrometers or less.

  Referring to FIGS. 6 and 7, solder paste 9 a is printed in through hole 2. Specifically, the solder paste 9a having viscosity is applied on the main surface of the metal mask 5 in the vertical direction upper side (the side opposite to the side on which the substrate 1 is disposed). The solder paste 9a is preferably, for example, a mixture of solder balls and a flux.

  For example, solder balls have an alloy composition of Sn-3.0Ag-0.5Cu, which is a general lead-free solder. However, the solder ball is not limited to this, and is, for example, any one selected from the group consisting of Sn-Cu solder, Sn-Bi solder, Sn-In solder, Sn-Sb solder, and Sn-Pb solder. May be The size of the solder ball is approximately 30 μm in particle size when it approximates to a spherical shape. The flux is, for example, mainly composed of rosin. However, not limited to this, for example, a polymer-based flux may be used.

  With the solder paste 9 a applied, the squeegee 8 is moved in the direction M indicated by the arrow in the drawing while the squeegee 8 is in partial contact with the main surface of the metal mask 5. Thereby, the squeegee 8 spreads the applied solder paste 9 a on the surface of the metal mask 5. At this time, the solder paste 9 a is filled in the opening 6 b of the metal mask 5. Since the opening 6 b of the metal mask 5 is disposed to overlap the through hole 2 in plan view, the solder paste 9 a in the opening 6 b is accommodated in the through hole 2 immediately below.

  As described above, the solder paste 9a is supplied into the through holes 2 using the screen printing method. However, the supply of the solder paste 9a is not limited to the screen printing method, and may be performed by, for example, a dispenser.

  The solder paste 9 a may be stored so as to be entirely filled in the through holes 2. However, as shown in FIG. 7, solder paste 9a may be stored so as to fill only a part of through hole 2, for example, about a half area on the side of upper main surface 1a.

  Referring to FIG. 8, next, metal mask 5 is removed from upper main surface 1a (on resist 4). Thereby, the solder paste 9 a is formed as a pattern in the through hole 2. Next, the insertion mounting component 10 is prepared. The insertion mounting component 10 has an insertion mounting component body 10a and a lead 10b extending therefrom. The lead 10 b of the insertion mounting component 10 is inserted into the through hole 2 on which the solder paste 9 a is printed.

  The insertion mounting component body 10a is, for example, a connector component made of nylon, and the lead 10b which is an external electrode terminal is, for example, a copper electrode lead whose surface is tin-plated.

  The lead 10b of the prepared insertion mounting part 10 is inserted into the through hole 2 from the upper main surface 1a side toward the lower main surface 1b side. Thereby, the insertion mounting component body 10 a is disposed on the upper main surface 1 a side of the substrate 1.

  Next, the solder paste 9 a is melted by heating to fix the lead 10 b to the substrate 1. Thereby, the lead 10b is fixed to the substrate 1 via the solder paste 9a. Specifically, the substrate 1 is placed in a high temperature furnace such as a reflow furnace and heated to 250 ° C. Thereby, the solder paste 9 a is melted and diffused throughout the through hole 2.

  Referring to FIG. 9, the solder balls contained in melted solder paste 9a aggregate and are accommodated inside through hole 2 as aggregated solder 9b. Flocculating solder 9 b adheres so that the surface of conductive layer 3 of through hole 2 and lead 10 b are electrically connected. That is, the agglomerated solder 9 b forms a solder joint with the lead 10 b in the through hole 2. On the other hand, the flux contained in the solder paste 9 a is pushed out from the aggregation solder 9 b at the time of heating and tends to flow out of the through hole 2. In particular, here, since the lead 10b is inserted from the upper main surface 1a to the lower main surface 1b, the flux 11 flows out to the lower main surface 1b. The flux 11 flowing out of the through hole 2 is prevented from flowing out further outward by the silk 7 a adjacent to the outside of the through hole 2. It is because silk 7a functions like a bank. As described above, the lead 10b is bonded to the through hole 2 of the substrate 1 through the aggregation solder 9b of the solder paste 9a.

  Next, the upper and lower sides of the substrate 1 are reversed, and the lower main surface 1b is again placed above the upper main surface 1a in the vertical direction. Next, conductive pads 12 are formed on resist 4 on lower main surface 1b or lower main surface 1b of substrate 1 by using a generally known film forming method, a normal photolithographic technique, or the like. It is formed. At this time, as shown in FIG. 9, the substrate 1 is supported by the back plate 13 from the lower side, that is, the upper main surface 1a side.

  The back plate 13 is a member for supporting from the lower side in order to prevent the substrate 1 from being warped in the direction along the upper main surface 1 a or the like when the solder paste 9 a is supplied by the screen printing method. Usually, a flat plate is used as the back plate 13. However, in the present embodiment, it is preferable to use the back plate 13 in which a part of the upper surface is provided with a recess. Thereby, when the upper main surface 1a is disposed lower than the lower main surface 1b, the portion of the insertion mounting component main body 10a protruding below the upper main surface 1a interferes with the back plate 13 Can be suppressed. More specifically, as shown in FIG. 9, the resist 4 on the upper main surface 1 a side of the substrate 1 is placed on the back plate 13. As a result, the insertion mounting component body 10 a protruding from the upper main surface 1 a to the upper side (the lower side in FIG. 9) is housed inside the recess formed in the back plate 13.

  The pad 12 is formed on the resist 4 on or on the lower main surface 1 b in an optional area outside the through hole 2. The pad 12 is a pattern made of, for example, a copper thin film. Next, solder paste 9 a is supplied onto the pad 12.

  Specifically, as in the steps shown in FIGS. 6 and 7, first, a mask, that is, metal mask 5 is provided on lower main surface 1b of substrate 1 (and on resist 4). The metal mask 5 has an opening 6c formed to penetrate from one main surface to the other main surface in a direction substantially orthogonal to the main surface. The metal mask 5 is disposed such that the opening 6 c is disposed at a position overlapping the pad 12 in plan view. In this state, solder paste 9a having the same viscosity as the process of FIG. 6 is applied by screen printing onto the main surface of metal mask 5 in the vertical direction above (the side opposite to the side on which substrate 1 is disposed). Ru. That is, with the solder paste 9 a applied, the squeegee 8 is moved in the direction M indicated by the arrow in the drawing. Thereby, the solder paste 9 a is filled in the opening 6 c of the metal mask 5.

  Referring to FIG. 10, after solder paste 9a is supplied on pad 12, metal mask 5 is removed, and surface mount component 14 is mounted on pad 12 as shown in FIG. Next, the surface mounting component 14 is bonded onto the pad 12 through the solder paste 9 a by heating. Thus, the surface mounted component 14 is mounted on the substrate 1. Specifically, the substrate 1 is placed in a high temperature furnace such as a reflow furnace and heated to 250 ° C. As a result, as shown in FIG. 10, the solder paste 9a is melted to form agglomerated solder 9b, and the pad 12 and the surface mounted component 14 are bonded by the agglomerated solder 9b. At this time, the agglomerated solder 9b in the through hole 2 previously used for bonding the lead 10b is melted again by heating. However, surface tension acts on the solder. For this reason, a defect such as the lead 10b of the insertion mounting component 10 not being bonded to the through hole 2 again can be avoided.

  The surface mount component 14 to be bonded is preferably any one selected from the group consisting of, for example, ceramic capacitors, chip resistors, SOP (Small Outline Package), and QFP (Quad Flat Package). The printed wiring board of the present embodiment is formed by the above steps.

  FIG. 11 is a schematic cross-sectional view of the finished printed wiring board formed by the steps of FIGS. 1 to 10, with the portion XI surrounded by the dotted line in FIG. 10 inverted vertically. 12 is a schematic plan view of the structure shown in FIG. 11 in the first embodiment as viewed from the direction indicated by arrow A. FIG. Referring to FIGS. 11 and 12, in the finished product of the printed wiring board according to the present embodiment, lead 10b of insertion mounting component 10 is bonded in through hole 2 by pin-in-paste soldering. . As described above, in the present embodiment, the silk 7a is formed so as to surround the entire region adjacent to the through hole 2 in a plan view (see FIG. 12). In FIG. 12, the silk 7 a is formed in a region adjacent to the through hole 2 so as to have a circular planar outer peripheral shape. However, not only this but silk 7a can be formed, for example so that it may have arbitrary plane perimeter shape, such as square shape.

  As shown in FIG. 11, it is preferable that the flux 11 be disposed so as not to protrude from the silk 7a. Further, as shown in FIG. 11, on the upper main surface 1a side, the edge of the aggregation solder 9b extends in a direction inclined to both the direction along the main surface 1a and the vertical direction in which the through hole 2 extends. preferable.

Next, the operation and effect of the present embodiment will be described with reference to a comparative example.
13 to 15 are schematic cross sectional views showing a method of manufacturing a printed wiring board as a comparative example of the present embodiment and a finished product. Specifically, FIG. 13 corresponds to the process of FIG. 7 of the present embodiment. FIG. 14 corresponds to the process of FIG. 8 of the present embodiment. FIG. 15 is a part of a finished product corresponding to FIG. 11 of the present embodiment.

  13 to 15, the printed wiring board of the comparative example and the method of manufacturing the same are basically the same as the printed wiring board of the present embodiment and the method of manufacturing the same. Therefore, the same components are denoted by the same reference numerals and the description thereof will not be repeated. However, in FIG. 13 to FIG. 15, the silk 7 a as the stepped portion is not formed on the lower main surface 1 b (the resist 4 on the upper side). The comparative example is different from this embodiment in this point.

  Also in the comparative example, solder paste 9a is heated in a state where lead 10b is inserted from the upper side to the lower side in the vertical direction into through hole 2 to which solder paste 9a is supplied, for example, in the process of FIG. At this time, when the solder paste 9a is melted, the solder balls are aggregated to form aggregated solder 9b as a solder joint portion. On the other hand, the flux in the solder paste 9 a flows out of the lower main surface 1 b of the substrate 1 to the outside of the through hole 2. This is because a step such as silk 7a that blocks this outflow is not formed. The flux leaks to the lower main surface 1b side of the substrate 1 by gravity and wets and spreads on the lower main surface 1b. The flux that has flowed out to the lower main surface 1b side of the substrate 1 adheres to the soldered parts of other electronic components arranged in the periphery. As a result, for example, printing defects of the solder paste 9a at the time of implementation of the process shown in FIG.

  As described above, particularly when the lead 10 b is inserted from the upper side to the lower side of the through hole 2, leakage of molten solder in the through hole 2 becomes a problem. The molten solder is to be easily lowered by gravity.

  Therefore, in the present embodiment, as described above, the silk 7a as a stepped portion is formed in the region adjacent to the through hole 2 on the lower main surface 1b (or on the resist 4 thereon). As a result, when heating solder paste 9a, flux 11 (see FIG. 9) which has flowed downward from through hole 2 by gravity flows out of through hole 2 and suppresses the problem of wetting and spreading on lower main surface 1b. can do. It is because silk 7a has a role of a bank.

  In addition, the formation of the silk 7 a reduces the possibility that the solder paste 9 a supplied on the pad 12 formed on the outside of the silk 7 a as viewed from the through hole 2 flows into the through hole 2. Can. In addition, since the possibility of flux or the like leaked from the through hole 2 adhering to the pad 12 can be reduced by the silk 7 a, a short circuit failure or the like in the pad 12 can be suppressed.

  The silk 7a as the stepped portion is formed by silk screen printing. Moreover, the silk 7a as a level | step-difference part is formed with the material containing an epoxy resin. By these, silk 7a as a level difference part which has desired thickness and desired intensity can be formed stably.

  Further, the silk 7a as the step portion is formed by forming the printing material so as to fill the inside of the opening of the metal mask and curing it. For this reason, the level | step-difference part of silk 7a which has desired thickness and desired intensity | strength can be formed stably.

  In the present embodiment, the silk 7 a is formed so as to surround the entire through hole 2. For this reason, the outflow of the flux contained in the solder paste supplied into the through hole 2 can be blocked all around the through hole 2. For this reason, the outflow control effect of the flux by silk 7a is heightened.

  The silk 7a is formed to have a thickness of, for example, 20 μm in a direction along the direction from the upper main surface 1a to the lower main surface 1b. It is preferable that the said thickness of silk 7a is 10 micrometers or more and 50 micrometers or less. If the thickness of the silk 7a is less than 10 μm, the effect of suppressing the outflow of the flux 11 from the through hole 2 is weakened. When the thickness of the silk 7a exceeds 50 μm, the silk 7a may fall off the substrate 1 when packing or transporting the printed wiring board. When the thickness of silk 7a exceeds 100 μm, such as 0.4 mm, metal mask 5 is placed in contact with the surface of silk 7a in the process of FIG. 9, for example. In this case, the thickness of the silk 7 a is large, and a gap is formed between the pad 12 and the lowermost surface of the metal mask 5. As a result, it becomes difficult to fill the solder paste 9a only in the opening 6c, and it becomes difficult to supply the solder paste 9a only on the pad 12.

  In addition, in the present embodiment, in the state where lead 10b is inserted from the side of upper main surface 1a to the side of lower main surface 1b in through hole 2, the tip of lead 10b is accommodated in through hole 2 Is preferred. In other words, the lead 10b inserted into the through hole 2 does not protrude outward from the lower main surface 1b, and the conductive layer 3 and the aggregation solder 9b are disposed with the tip end portion thereof disposed inside the through hole 2 It is preferable that they be joined via This is due to the following reasons. That is, as shown in FIG. 9, the screen printing method in which the substrate 1 is turned upside down and the solder mask 9a is supplied using the metal mask 5 may be applied after the step of inserting and joining the leads 10b. . In this case, if the leading end of the lead 10b protrudes from the lower main surface 1b to the outside, a problem may occur in the printing process.

Second Embodiment
FIG. 16 is a schematic plan view of the structure shown in FIG. 11 in the second embodiment as viewed from the direction indicated by arrow A. In the present embodiment, a printed wiring board as a finished product having the same configuration as that of FIG. 11 is formed basically by the same steps as those of FIGS. 1 to 10 of the first embodiment. Therefore, in the present embodiment, the description of the manufacturing process shown in FIGS. 1 to 11 and the schematic cross sectional view of the finished product will not be repeated.

  Referring to FIG. 16, in the present embodiment as well as silk 7a of FIG. 12 of the first embodiment, silk 7b is formed to surround a region adjacent to through hole 2 in plan view. However, in the present embodiment, the silk 7 b is formed only in a part of the region adjacent to the through hole 2 in a plan view. That is, the silk 7 b is formed in a part of the region adjacent to the through hole 2 so as to have the cutaway portion 15 which is missing. The silk 7 b of FIG. 16 is also formed to have a circular arc-like plane shape, similarly to the silk 7 a of FIG. 12. However, the present invention is not limited to this, and the silk 7 b can be formed to have an arbitrary planar outer peripheral shape such as, for example, a square shape, as long as it has the partially lost notch portion 15.

  As described above, in the present embodiment, the silk 7 b as the stepped portion is formed in a region adjacent to the through hole 2 so as to surround only a part of the through hole 2. In this point, the present embodiment is different in configuration from the silk 7 a of the first embodiment formed so as to surround the entire through hole 2.

Next, the function and effect of the present embodiment will be described with reference to FIG.
FIG. 17 is a schematic plan view showing an outflow aspect of the flux 11 in the through hole 2 in the configuration having the silk 7 b of FIG. 16. FIG. 17 shows an aspect viewed from the same direction as FIG. Referring to FIG. 17, for example, when a large amount of flux 11 is contained in the solder paste supplied into through hole 2, flux 11 may overflow and flow from silk 7 b which is a step portion around it. . As a result, the flux 11 may adhere to the soldered parts such as electronic parts around it. As a result, printing defects, component mounting defects, soldering defects, and the like of the solder paste 9a may be affected.

  However, from the viewpoint of suppressing such outflow, if the silk 7b has a thickness exceeding 50 μm, for example, the silk 7b may fall off the substrate 1 at the time of transportation as described above, or the metal mask 5 may be placed thereon. Problems may occur when performing the printing process. In the first place, if the silk 7b is formed thick, the cost of manufacturing the printed wiring board will rise because the material cost will rise.

  Therefore, as in the silk 7 b of the present embodiment, the notch portion 15 is provided and formed so as to surround only a part of the through hole 2. Thereby, the flux 11 from the through hole 2 can be made to flow preferentially out of the notch portion 15. For this reason, the flux 11 flowing out of the through hole 2 can be spread only in the region adjacent to the outside of the notch portion 15 on the lower main surface 1 b. As a result, it is possible to suppress the flux 11 from spreading in all directions around the through holes 2 in the lower main surface 1b. Therefore, when the lower main surface 1b is viewed in plan, as long as the notched portion of the electronic component is not present in a region adjacent to the outer side of the notched portion 15 when viewed from the through hole 2, The problem caused by the adhesion of the flux 11 to the soldered portion can be avoided. Even if the flux 11 flows onto the lower main surface 1b, no problem occurs if there is no soldered part of the electronic component or the like.

  That is, when the silk 7 b has the notch 15, the possibility of the flux 11 overflowing from the portion of the silk 7 b other than the notch 15 can be reduced. For this reason, it can suppress that the flux 11 spreads over the whole surface of the lower main surface 1b.

  In the present embodiment, it is preferable that the electronic component and the associated soldering portion not be disposed particularly in a region facing the notch 15 in the direction away from the through hole 2. That is, it is preferable that the electronic component and the soldering part associated therewith be disposed on the lower main surface 1 b in a region other than the region facing the notch 15 in the direction away from the through hole 2.

Third Embodiment
FIG. 18 is a part of a finished product corresponding to FIG. 11 of the present embodiment. FIG. 19 is a schematic plan view of the structure shown in FIG. 18 in the third embodiment as viewed from the direction indicated by arrow B. In the present embodiment, a printed wiring board as a finished product of the configuration shown in FIG. 18 is formed basically by the same steps as in FIGS. 1 to 10 of the first embodiment. Therefore, in the present embodiment, the description of the manufacturing process shown in FIGS. 1 to 10 will not be repeated.

  Referring to FIGS. 18 and 19, in the printed wiring board according to the present embodiment, insertion is performed in which insertion mounted component 10 to be mounted is connected commonly to three leads 10b and these three leads 10b. And a mounting component body 10c. As described above, in the present embodiment, the insertion mounting component 10 has the leads 10 b as a plurality of external electrode terminals. The insertion mounting part 10 of FIG. 18 and FIG. 19 is a 3-pin type which has three leads 10b as an example. However, the present invention is not limited to this, the number of leads 10b included in a single insertion mounting component 10 is arbitrary, and may be two or four or more. The three leads 10 b included in the insertion mounting component 10 are the same as the leads 10 b of the first embodiment. The insertion mounting component body 10c is, for example, a connector component made of nylon.

  Each of the three leads 10b is inserted into different through holes 2 of the substrate 1 and is joined to the conductive layer 3 through the joint of the solder paste 9a (aggregated solder 9b). Moreover, silk 7c as a level | step-difference part is formed of the material and process similar to silk 7a, 7b. The silk 7 c is formed in a region adjacent to the plurality of through holes 2 so as to surround all the through holes 2 into which the respective leads 10 b included in one insertion mounting component 10 are inserted. In FIG. 19, the silk 7 c has a rectangular planar outer peripheral shape. However, the shape is not limited to this, and may have an elliptical shape, for example. Alternatively, each of the four corner portions of the silk 7 c in FIG. 19 may be formed in an arc shape. Further, in FIG. 19, the silk 7 c has a planar shape surrounding the whole of the three through holes 2. However, silk 7 c may have a planar shape that partially has notches 15 as in the second embodiment, for example, and surrounds only a part of three through holes 2.

  As in the present embodiment, the insertion mounting component 10 also has the plurality of leads 10 b and the silk 7 c formed so as to collectively surround the plurality of through holes 2 into which they are inserted. Similar to 1 and 2, the effect of suppressing the outflow of the flux 11 is exerted.

  The features described in the above-described embodiments (each example included in the embodiments) may be applied as appropriate in a technically consistent range.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all the modifications within the meaning and scope equivalent to the claims.

  Reference Signs List 1 substrate, 1a upper main surface, 1b lower main surface, 2 through holes, 3 conductive layers, 4 resists, 5 metal masks, 6a, 6b, 6c openings, 7 ink, 7a, 7b, 7c silk, 8 squeegees, 9a Solder paste, 9b cohesive solder, 10 insertion mounting parts, 10a, 10c insertion mounting parts body, 10b leads, 11 flux, 12 pads, 13 back plates, 14 surface mounting parts, 15 notches.

Claims (6)

Forming a stepped portion on the substrate in which the through hole is formed;
Placing a solder paste in the through hole;
Inserting a lead of an insertion mounting component into the through hole in which the solder paste is disposed;
Melting the solder paste by heating to fix the leads to the substrate;
In the step of inserting the lead, the lead is inserted from the upper main surface side with respect to the vertical direction of the substrate toward the lower main surface side with respect to the vertical direction opposite to the upper main surface,
The method for manufacturing a printed wiring board, wherein the stepped portion is formed to extend downward from the lower main surface in a region adjacent to the through hole on the lower main surface of the substrate. .   The method for manufacturing a printed wiring board according to claim 1, wherein the stepped portion is formed by silk screen printing.   The method for manufacturing a printed wiring board according to claim 1, wherein the stepped portion is made of a material containing an epoxy resin.   The method for manufacturing a printed wiring board according to any one of claims 1 to 3, wherein the stepped portion is formed to surround only a part of the through hole in a region adjacent to the through hole.   The method for manufacturing a printed wiring board according to any one of claims 1 to 3, wherein the stepped portion is formed to surround the entire through hole in a region adjacent to the through hole. The stepped portion includes a step of installing a mask having an opening on the lower main surface, a step of supplying a printing material to fill the opening of the mask, and a step of curing the printing material And forming the printed wiring board according to any one of claims 1 to 5.

Images