JPH0736473U - Printed wiring board - Google Patents

Abstract

(57) [Abstract] [Purpose] In a printed wiring board where components are mounted on both sides by pins, when the components are mounted on one side by the flow soldering method, lands formed on the surface opposite to the flow soldering surface. It is an object of the present invention to sufficiently prevent solder wicking to the surface without newly providing a process. When a component is mounted on one surface of a printed wiring board 1 by a flow soldering method, a land 8 on a surface 1b opposite to a surface contacting molten solder has an inner diameter S of which is a diameter of a lead insertion hole 6. It was formed to be larger than K.
Further, the solder resist layer 10 was formed on the surface 9 of the insulating substrate 2 between the opening end 6a of the lead insertion hole 6 and the inner peripheral end surface 8a of the land 8.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a printed wiring board, and more specifically, in a case where components are mounted on both sides by pins, when the components are mounted on one side by a flow soldering method, the surface on the opposite side to the flow-stuck side is mounted. The present invention relates to a printed wiring board in which molten solder is prevented from rising to a land formed on a substrate through a through hole.

[0002]

[Prior art]

 In general, some printed wiring boards having conductor patterns formed on both sides have through holes having a copper plating layer or through holes for mounting a plurality of components having leads on both sides. For example, in the printed wiring board 1 shown in FIG. 9, two lead insertion holes (through holes) 5 and 6 of the components 3 and 4 are formed through the insulating substrate 2 as a set. Further, on the surface side of the lead insertion holes 5 and 6 opposite to the mounting surface of each component of the insulating substrate 2, on the peripheral surface of the lead insertion holes 5 and 6, there are land 7 and 8 made of copper foil, respectively. Has been formed.

Then, first, with the lead 3a of the component 3 being inserted into the lead insertion hole 5, one surface 1a of the printed wiring board 1 is brought into contact with the molten solder in the solder bath to make the land 7 and the lead 3a. Soldering (flow soldering) and is performed on one side. That is, this flow soldering is performed on one surface 1a of the printed wiring board 1, and the component 4 on the other surface 1b is mounted by inserting the leads 4a into the lead insertion holes 6 after the flow soldering. In this state, the lead 4a and the land 8 are manually soldered.

However, when mounting one side of the component 3 by the flow soldering, the molten solder passes through the lead insertion hole 6 to the land 8 of the surface 1b opposite to the surface 1a on which the flow soldering is performed. It may go up. Then, even if the molten solder adheres to the land 8 and the flow soldering is completed and the printed wiring board 1 is separated from the solder bath, the molten solder remains without being separated from the lead insertion hole 6 and the lead insertion hole is formed. There was a problem that 6 was sealed. The through hole T is also sealed by this solder rise, but since it is not a hole for mounting components, there is no particular problem if it is sealed.

Therefore, in order to prevent the solder from rising onto the land 8 as described above, a resist R 2 is formed at the opening portion of the lead insertion hole 6 of the surface 1a which comes into contact with the molten solder H, as shown in FIG. A method of temporarily sealing the opening to prevent the molten solder H from entering has been proposed.

Further, as shown in FIG. 11, a method of forming the land 8 on the surface 1 b of the printed wiring board 1 so that the inner diameter thereof is larger than the diameter of the lead insertion hole 6 without providing the resist R is also proposed. Has been done. By forming the land 8 in this manner, the molten solder H rises to the surface 9 between the open end of the lead insertion hole 6 and the inner peripheral end surface of the land 8, and thus it is difficult to rise to the land 8.

[0007]

[Problems to be solved by the device]

 However, in the former method of preventing solder rising, it is necessary to newly provide a step for forming the resist R, and there is a problem that the number of steps is increased and the cost is increased.

Further, in the latter method, even when the molten solder is raised to the surface 9 through the lead insertion hole 6 during the flow soldering, the width of the surface 9 is narrow, so that the molten solder reaches the land 8. However, there is a problem in that it is difficult to prevent solder from rising onto the land 8.

The present invention has been made to solve the above problems, and in a printed wiring board in which components are pin-mounted on both sides, when the components are mounted on one side by flow soldering, The purpose is to sufficiently prevent the rising to the land formed on the surface opposite to the flow soldering surface, without adding a new step.

[0010]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention provides a through hole for pin-mounting a plurality of components having leads on both sides of an insulating substrate, and at the same time, the mounting surface of each component on the insulating substrate. In a printed wiring board with lands formed on the peripheral surface of the through-hole on the opposite side to the side opposite to the surface that comes into contact with molten solder when component mounting on one side of the printed wiring board is performed by the flow soldering method. The land on the surface of the insulating substrate between the open end of the through hole and the inner peripheral end face of the land, while forming the land on the surface of the land so that its inner diameter is larger than the diameter of the through hole. One of the insulating resist layer and the printing ink layer was formed.

[0011]

[Action]

 According to the present invention, the component and the lead are inserted into the through hole having the land in which the insulating resist layer or the like of the insulating substrate is not formed, and the land and the lead are soldered by the flow soldering to form the printed wiring. Mounting on one side of the board is performed. At this time, the molten solder rises from the remaining through-holes in which the leads of the component are not inserted, but one of the insulating resist layer and the printing ink layer serves as a wall and is blocked. Therefore, unlike the conventional case, the molten solder is less likely to reach the land, so that the solder rising onto the land is sufficiently prevented and the through hole is prevented from being sealed due to the adhesion of the molten solder to the land.

Since the insulating resist layer is the same as the resist used when insulating the conductor circuits formed on both surfaces of the insulating substrate, the insulating resist layer can be formed at the same time, so that it is possible to prevent solder rising onto the land. It is not necessary to provide a new process for Further, since the printing ink layer is formed simultaneously with the same ink used when printing the part number, characters, etc. on the printed wiring board, it is not necessary to newly provide a step as in the above case.

[0013]

【Example】

 (First Embodiment) A first embodiment embodying the present invention will be described below with reference to FIGS.

It should be noted that the same configurations as those of the above-mentioned conventional technique are designated by the same reference numerals and the description thereof will be omitted. As shown in FIGS. 1 and 2, the land 8 on the surface 1b opposite to the surface 1a that contacts the molten solder of the printed wiring board 1 has a dimension of the inner diameter S (1.6 mm in this case) of the lead insertion. The hole 6 is formed in a substantially elliptical shape in a plane larger than the size of the aperture K (1.5 mm in this case). Further, a solder resist layer 10 used for insulation is formed on the surface 9 of the insulating substrate 2 between the opening end 6a of the lead insertion hole 6 and the inner peripheral end surface 8a of the land 8.

The solder resist layer 10 has a plane annular shape and is formed higher than the land 8 (in this case, 60 μm to 80 μm), and its width dimension (in this case, 0.3 mm) is the width of the surface 9. Is shorter than the dimension (in this case, 0.5 mm). The inner peripheral end surface of the solder resist layer 10 is flush with the inner wall surface of the lead insertion hole 6, and a groove 11 is formed between the outer peripheral end surface and the inner peripheral end surface 8a of the land 8. There is. Further, the solder resist layer 10 is the same heat-resistant resin as the solder resist covering the conductor circuits (not shown) formed on both surfaces of the insulating substrate 2, and with respect to the temperature of the molten solder (240 ° C to 260 ° C). Has sufficient heat resistance.

When the printed wiring board 1 configured as described above is mounted on one side by flow soldering, as shown in FIG. 3, the printed wiring board 1 has its surface 1 a in contact with the molten solder H. It is conveyed in the direction of arrow Y.

At this time, the molten solder H rises to the opposite surface 1b side through the lead insertion hole 6, but the solder resist layer 10 becomes a wall and is blocked, and it becomes difficult to reach the land 8. Further, even if the molten solder H exceeds the solder resist layer 10, the molten solder H is repelled by the solder resist layer 10 and divided, and a part thereof flows into the groove 11.

When the printed wiring board 1 is transported and separated from the solder bath, the molten solder H in the lead insertion hole 6 descends and is separated. At this time, since the molten solder H is not attached to the land 8, the lead insertion hole 6 is not sealed.

As described above, in the first embodiment, the molten solder H 2 is blocked by the solder resist layer 10, so that the molten solder H 2 does not easily reach the land 8 and the solder rise to the land 8 is prevented. It can be sufficiently prevented. Therefore, after the completion of the flow soldering, the molten solder does not adhere to the land 8 and is separated from the lead insertion hole 6, so that the lead through hole 6 can be prevented from being sealed by the solder. Further, it is possible to solder only the necessary portions of the land and the lead of the surface 1a of the printed wiring board 1 which comes into contact with the molten solder.

Further, since the groove 11 is formed between the outer peripheral end surface of the solder resist layer 10 and the inner peripheral end surface 8a of the land 8, a part of the molten solder that is peeled off by the solder resist layer 10 is divided. Since the solder flows in, it is possible to more reliably prevent the solder from rising onto the land 8.

Further, since the solder resist layer 10 is formed only on the land 8 formed on the surface opposite to the flow soldering surface, the surface for performing the flow soldering of the printed wiring board 1 and the manual soldering The surface to be processed can be easily distinguished.

The above-mentioned solder resist layer 10 is formed on the surface 9 at the same time as the step of coating the conductor circuits (not shown) on both surfaces of the insulating substrate 2 with the solder resist by a conventional method. Therefore, it is not necessary to provide a new process for preventing the solder from rising onto the land 8, and it is possible to suppress an increase in cost.

Second Embodiment Next, a second embodiment will be described. In this embodiment, the shape of the solder resist layer 10 is different from that of the first embodiment, and another layer is formed on a part of the land 8.

As shown in FIGS. 4 and 5, the land 8 on the surface 1 b of the printed wiring board 1 has a dimension of the inner diameter S (in this case, 1.6 mm) of the diameter K of the lead insertion hole 6 (this dimension). In this case, it is formed in a substantially elliptical plane slightly larger than 1, 5 mm. Further, a solder resist layer 12 is formed on the surface 9 of the insulating substrate 2 between the opening end 6a of the lead insertion hole 6 and the inner peripheral end surface 8a of the land 8 and on the inner peripheral edge of the land 8. Therefore, although the surface area of the solder resist layer 12 is larger than that of the solder resist layer 10 of the first embodiment, it is smaller than the surface area of the land 8 and there is no problem in soldering the leads of the component. It has become an area. Further, a silk ink layer 13 as a printing ink is provided in a front portion of the land 8 in the transport direction of the printed wiring board 1 shown by an arrow Y with a predetermined width from the outer peripheral end face of the solder resist layer 12 to the outer periphery of the land 8. It is formed continuously over the edges.

The silk ink layer 13 is made of vinyl resin and is the same as the silk ink used when printing a component number, characters, etc. on the printed wiring board 1. Further, the silk ink layer 13 has heat resistance to the temperature of the molten solder (240 ° C to 260 ° C), but it melts at the temperature of the manual soldering (about 300 ° C). There is. The thickness of the silk ink layer 13 and the solder resist layer 12 on the land 8 is 40 to 60 μm. The silk ink layer 13 is formed by the impact when the printed wiring board 1 is transported on the solder bath when it collides with another printed wiring board transported forward, as shown in FIG. This is because the molten solder H that spreads in the same direction as the transport direction is not attached to the land 8.

When the printed wiring board 1 configured as described above is mounted on one side by flow soldering, as shown in FIG. 6, the printed wiring board 1 has its surface 1 a in contact with the molten solder H. It is conveyed in the direction of arrow Y.

At this time, the molten solder H rises to the opposite surface 1 b side through the lead insertion hole 6, but the solder resist layer 12 becomes a wall and is blocked, and it becomes difficult to reach the land 8. Further, the rising molten solder H wets and spreads on the surface of the solder resist layer 12, and the upper surface thereof has a relatively flat shape.

Then, when the printed wiring board 1 is transported and separated from the solder bath, the molten solder H in the lead insertion hole 6 descends. At this time, since the upper surface of the molten solder H has a flat shape, the molten solder H does not rise in a dome shape and can easily descend.

Next, after the component mounting on one surface of the printed wiring board 1 is completed, the component mounting on the opposite surface is performed by manual soldering. At this time, the heat of soldering melts the silk ink layer 13 to expose the land 8, and the entire surface of the land 8 and the lead are soldered.

As described above, in the second embodiment, since the solder resist layer 12 is formed so as to cover the surface 9 and the inner peripheral edge of the land 8, it becomes difficult for the molten solder H to reach the land 8. It is possible to sufficiently prevent the solder from rising onto the land 8.

Further, the molten solder H wets and spreads on the surface of the solder resist layer 12, and the upper surface thereof has a relatively flat shape. As a result, when the printed wiring board 1 is separated from the solder bath, the molten solder H does not swell in a dome shape, so that the solder easily falls and the clogging of the lead insertion hole 6 due to the solder can be prevented as much as possible.

Further, by forming the silk ink layer 13 on the front part of the land 8 in the conveyance direction of the printed wiring board 1, when the printed wiring board 1 collides with another printed wiring board during flow soldering. It is possible to prevent the molten solder H, which spreads by impact, from adhering to the land 8.

Further, after the flow soldering, when the components on the opposite side are mounted by soldering manually, the heat melts the silk ink layer 13, so that the entire surface of the land 8 is used. Can be attached.

The above-described solder resist layer 12 is formed at the same time as the step of covering and insulating a conductor circuit (not shown) with a solder resist as in the first embodiment. Further, the silk ink layer 13 is formed on the printed wiring board 1 at the same time as the step of printing the part number, characters, etc. by silk printing. Therefore, in the second embodiment as well, it is not necessary to provide a new process for preventing the land 8 from rising.

The present invention is not limited to the above-mentioned respective embodiments, and may be carried out as follows, for example, within a range not departing from the gist of the present invention. (1) In the first embodiment, the solder resist layer 10 is formed on the surface 9 of the insulating substrate 2 between the opening end 6a of the lead insertion hole 6 and the inner peripheral end surface 8a of the land 8. However, instead of this, Alternatively, a silk ink layer may be formed. Also, a silk ink layer may be laminated on the solder resist layer 10 to form a two-layer structure.

(2) As shown in FIG. 7, the inner peripheral end surface of the solder resist layer 10 may be located on the surface 9 instead of being flush with the inner wall surface of the lead insertion hole 6. By doing so, a new surface 14 is provided between the inner peripheral end surface of the solder resist layer 10 and the opening end 6a, and a slight distance is secured until the molten solder reaches the solder resist layer 10. Therefore, the solder is hard to rise. Focusing on this point, a plurality of solder resist layers 10 are formed concentrically on the surface 9 at a predetermined interval so that the reaching distance of the molten solder to the inner peripheral end surface 8a of the land 8 is increased. Good.

(3) As shown in FIG. 8, only the solder resist layer 12 may be used without forming the silk ink layer 13 in the second embodiment. Further, instead of the solder resist layer 12, a silk ink layer 13 may be formed, or a silk ink layer may be laminated on the solder resist layer 12 to form a two-layer structure.

(4) The present invention may be applied not only to the printed wiring board 1 having conductor circuits formed only on both sides but also to a multilayer printed wiring board having conductor circuits formed on inner layers. (5) Oil-based, cellulose-based, and asphalt-based resins other than vinyl-based resins may be used for the printing ink layer. When the above-mentioned resin is used, it is required that it has heat resistance during flow soldering and has the property of being melted by the heat of manual soldering.

[0039]

[Effect of device]

 As described above in detail, according to the present invention, in the printed wiring board in which the components are pin-mounted on both sides, when the components are mounted on one side by the flow soldering method, the components are mounted on the surface opposite to the flow soldering surface. This has an excellent effect that solder rising onto the land to be formed can be sufficiently prevented without newly providing a process.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a main part of a printed wiring board according to a first embodiment of the present invention.

FIG. 2 is likewise a schematic cross-sectional view of an essential part showing a printed wiring board.

FIG. 3 is likewise a schematic cross-sectional view of an essential part showing a state where a printed wiring board is subjected to flow soldering.

FIG. 4 is a schematic plan view of a main portion of a printed wiring board according to a second embodiment.

FIG. 5 is likewise a schematic cross-sectional view of an essential part showing a printed wiring board.

FIG. 6 is likewise a schematic cross-sectional view of an essential part showing a state where a printed wiring board is subjected to flow soldering.

FIG. 7 is a main part schematic plan view showing a printed wiring board of another embodiment.

FIG. 8 is a schematic plan view of a main portion showing a printed wiring board according to another embodiment.

FIG. 9 is a schematic cross-sectional view of essential parts showing a state where components are mounted on both sides of a printed wiring board.

FIG. 10 is a schematic cross-sectional view of essential parts showing a conventional printed wiring board.

FIG. 11 is a schematic cross-sectional view of a main part showing another conventional printed wiring board.

[Explanation of symbols]

1 ... Printed wiring board, 1a, 1b ... Surface, 2 ... Insulating substrate,
3, 4 ... Component, 3a, 4a ... Lead, 5, 6 ... Lead insertion hole as through hole, 6a ... Open end, 7, 8 ... Land,
9 ... Surface, 10, 12 ... Solder resist layer as insulating resist layer, 13 ... Silk ink layer as printing ink layer, K ... Bore, S ... Inner diameter, H ... Molten solder.

Claims (1)

[Scope of utility model registration request] 1. A through hole for pin-mounting a plurality of components having leads on both surfaces of an insulating substrate is formed in the insulating substrate, and a through hole on the opposite side of the insulating substrate from the mounting surface of each component. In a printed wiring board with lands formed on its peripheral surface, when the components are mounted on one side of the printed wiring board by the flow soldering method, the land on the side opposite to the side that contacts molten solder While being formed to be larger than the diameter of the through hole, at least on the surface of the insulating substrate between the opening end of the through hole and the inner peripheral end surface of the land,
A printed wiring board having one of an insulating resist layer and a printing ink layer formed thereon.