JP7462502B2 - Component mounting board and manufacturing method thereof - Google Patents

Description

The present invention relates to a component mounting board and a manufacturing method thereof, and in particular to a component mounting board in which electronic components are surface-mounted on a printed circuit board, and a manufacturing method thereof.

As electronic device modules and the component mounting boards on which they are mounted become smaller and lighter, the individual electronic components, such as semiconductor elements and electronic components, are becoming smaller. In order to achieve high-density mounting that matches the miniaturization of the modules and electronic components mounted on these types of component mounting boards, technology is being adopted to surface-mount electronic components on both sides of the printed circuit board.

Electronic components mounted on component mounting boards, such as integrated circuits, capacitive elements, resistive elements, light-emitting elements, connectors, and various filters, come in a variety of sizes depending on their electrical characteristics. Among these, large and heavy components that are difficult to hold in place using only the surface tension of the molten solder during the reflow process have generally been inserted and mounted. However, in order to promote the high density of component mounting boards, there is a demand for surface mounting of even large and heavy components.

For example, such components include right-angle pin headers and pin sockets. In order to surface mount these pin headers, their housings must be fixed to the printed circuit board with a resin adhesive to support their weight. One method for doing this is to use a technology in which a thermosetting resin adhesive is hardened during the heat treatment of solder reflow to fix the housing to the printed circuit board.

In this way, in order to perform both the curing of the resin adhesive and the solder reflow during a single heat treatment, the uncured resin adhesive must be applied to a specified position on the printed circuit board, and solder paste must be printed on the lands to which the lead terminals are soldered. The housing must then spread the uncured resin adhesive and attach it to the lands, and the pin header must then be placed on the printed circuit board so that the lead terminals are immersed in the solder paste that covers the lands.

A pin header has a structure in which, for example, pin terminals for connecting to an external device are arranged on one side of a rectangular parallelepiped housing, and lead terminals for soldering to a printed circuit board are arranged on the other opposite side. When the housing of this pin header is sucked and held by a mounter and placed on the printed circuit board, first the housing comes into contact with the uncured resin adhesive, and the lead terminals come into contact with the solder paste. Then, from this state, the housing is further pressed down to place it on the board.

At this time, if the surface of the printed circuit board on which the pin header housing is placed is flat, as shown in FIG. 14, for example, the side surface on the pin terminal side will tilt downward before the lead terminal is fully immersed in the solder paste, and the pressure will stop when the bottom end of the pin terminal side housing abuts against the surface of the printed circuit board, causing the pin header to be placed in an inclined state.

If solder reflow is performed while the pin header is placed at an angle, the resin adhesive heats and hardens while the solder melts, fixing the pin header at an angle. On the other hand, if the lead terminal is not sufficiently immersed in the solder, the solder may separate from the lead terminal as it melts, causing a defect in which the lead terminal is not electrically connected to the land on the printed circuit board.

In consideration of these problems, the present invention aims to provide a component mounting board and a manufacturing method thereof that adheres and fixes a large electronic component having asymmetrically arranged lead terminals, such as a right-angle pin header, to a printed circuit board and securely connects the lead terminals to lands for surface mounting.

One embodiment of the component mounting board is characterized in that it comprises an electronic component having a housing including a bottom surface and sides and lead terminals protruding from the side surfaces of the housing, and a printed circuit board on which the electronic component is mounted, the printed circuit board having an insulating substrate, a first land arranged on the surface of the insulating substrate, and a base layer arranged on the surface of the insulating substrate and spaced apart from the first land, a step region having a step with the upper surface of the base layer is arranged adjacent to the first land side of the base layer, the bottom surface of the housing is fixed by a resin adhesive arranged in the step region, the tip of the lead terminal is fixed by solder in contact with the first land, and only a portion of the bottom surface of the housing on the far end side located farther from the lead terminal, excluding the majority of the bottom surface of the housing, is arranged on the base layer.

Another aspect of the method for manufacturing a component-mounted board is a method for surface-mounting an electronic component having a housing including a bottom surface and sides and lead terminals protruding from the side surfaces of the housing on a printed circuit board, and is characterized in that the method includes the steps of: preparing a printed circuit board having a first land and a second land spaced from the first land on its surface before applying solder resist; forming a solder resist covering the second land and forming a step on the printed circuit board; applying solder paste covering the first land; applying thermosetting resin between the first land and the second land at a position adjacent to the second land on the surface of the printed circuit board; pressing the housing of the electronic component so that the bottom surface of the housing abuts against the solder resist covering the second land and adheres to the thermosetting resin and the lead terminals are immersed in the solder paste, thereby placing the electronic component on the printed circuit board; and performing a heat treatment to harden the thermosetting resin and reflow the solder paste.

The component mounting board and manufacturing method thereof disclosed herein can provide an effect of providing a component mounting board and manufacturing method thereof that can adhere and fix a large electronic component having asymmetrically arranged lead terminals, such as a right-angle pin header, to a printed circuit board and can reliably connect the lead terminals to lands for surface mounting.

FIG. 1 is a plan view of an embodiment of a component mounting board. FIG. 2 is a cross-sectional view taken along line AA' in FIG. FIG. 3 is a plan view of an electronic component of one embodiment of a component mounting board. FIG. 4 is a cross-sectional view of an electronic component of an embodiment of a component mounting board. FIG. 5 is a plan view of a printed circuit board according to an embodiment of the component mounting board. 6A to 6C are cross-sectional views showing the manufacturing process of the component mounting board manufacturing method. 7A to 7C are cross-sectional views showing the manufacturing process of the component mounting board manufacturing method. 8A to 8C are cross-sectional views showing the manufacturing process of the component mounting board manufacturing method. 9A to 9C are cross-sectional views showing the manufacturing process of the component mounting board manufacturing method. 10A to 10C are cross-sectional views showing the manufacturing process of the component mounting board manufacturing method. 11A to 11C are cross-sectional views showing the manufacturing process of a component mounting board in sequence. 12A to 12C are cross-sectional views showing the manufacturing process of the component mounting board manufacturing method. 13A to 13C are cross-sectional views showing the manufacturing process of the component mounting board manufacturing method. FIG. 14 is a plan view of a conventional component mounting board.

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 shows a plan view of a component mounting board 1 of one embodiment. Figure 2 is a cross-sectional view taken along line A-A' in Figure 1. The component mounting board 1 is constructed by mounting electronic components 10 on the surface of a printed circuit board 20.

The electronic component 10 has a housing 12. The housing 12 includes a bottom surface 12a and a side surface 12b, and a lead terminal 14 protrudes from the side surface 12b. The printed circuit board 20 has an insulating substrate 21 as a base, on whose surface a first land 23 and a base layer 24 are disposed. The first land 23 and the base layer 24 are spaced apart from each other. Between the first land 23 and the base layer 24, adjacent to the first land 23 side, a step region 27b having a step x with respect to the upper surface of the base layer 24 is disposed.

The lead terminals 14 of the electronic component 10 are electrically connected and mechanically fixed to each of the first lands arranged on the printed circuit board 20 via solder 19. Power can be supplied and signals can be transmitted between the electronic component 10 and the printed circuit board 20 through these lead terminals 14.

The housing 12 of the electronic component 10 is placed in contact with the base layer 24, with only a small portion 12a1 of the bottom surface 12a on the far end side located farther from the lead terminals 14. Most of the bottom surface 12a covers the upper part of the step region 27b, and the bottom surface 12a is separated from the step region 27b and does not contact it. In addition, the far end side of the bottom surface 12a also contacts the base layer 24, but is not fixed thereto.

The bottom surface 12a and the step region 27b are fixed to each other by a resin adhesive 17. Although the tip of the lead terminal 14 extending from the side surface 12b of the housing 12 is fixed to the first land 23 by solder 19, in order to support the overall weight of the electronic component 10, it is preferable to fix the housing 12 directly to the printed circuit board 20 (step region 27b) with the resin adhesive 17. In particular, in a board in which components are surface-mounted on both sides, the solder 19 may be remelted, in which case it is essential to fix the housing 12 to the printed circuit board 20 in advance with the resin adhesive 17. The resin adhesive 17 may be a thermosetting resin.

Figure 3 is a plan view of electronic component 10. Figure 4 is a cross-sectional view taken along line A-A' in Figure 3.

The electronic component 10 may be, for example, a pin header. Its housing 12 is made of molded resin having a roughly rectangular parallelepiped shape. The lead terminals 14 protruding from the side surface 12b of the housing 12 extend while bending. The tip of the lead terminal 14 has a straight-line portion of a certain length. By making it straight, the contact length with the first land 23 is increased, the variation in electrical resistance between the lead terminals 14 and the first land 23 is reduced, and the mechanical fixing strength by the solder 19 can also be stabilized.

The lead terminals 14 protrude in only one direction from the housing 12. A pin terminal 15 protrudes and extends from a side surface 12c different from the side surface 12b from which the lead terminals 14 protrude. The pin terminal 15 is, for example, a terminal that connects to a socket for establishing an electrical connection with the outside of the component mounting board 1, and is entirely separated from the printed circuit board 20 and does not come into direct contact with it. Depending on the specifications of the electronic component 10, the pin terminal 15 may protrude outward from the edge of the printed circuit board 20.

Figure 5 is a plan view of the printed circuit board 20, and the printed circuit board 20 will be described below with reference to Figure 2, which is a cross-sectional view of the component mounting board 1. The printed circuit board 20 has an insulating substrate 21 and a first land 23 arranged on its surface 21a. The surface of the printed circuit board 20 is generally covered with an insulating solder resist 27. For example, part or all of the first land 23 is exposed by providing an opening 27a in the solder resist.

The base layer 24 can be constructed by arranging a second land 26 on the surface 21a of the insulating substrate 21, spaced apart from the first land 23, and covering the second land 26 with solder resist 27. The step region 27b can be constructed by providing an opening in a part of the solder resist 27. At this time, the surface 21a of the insulating substrate 21 is exposed in the step region 27b. In addition, the region in which the step region 27b is arranged can be defined by providing an opening in the large-area second land 26. At that time, a dummy portion 25, which is a part of the second land 26, may remain between the step region 27b formed by the opening in the solder resist 27 and the first land 23.

Generally, the bottom surface 12a of the housing 12 of the electronic component 10 and the straight portion of the tip of the lead terminal 14 are on the same plane. Therefore, if the height (thickness) of the base layer 24 and the first land 23 from the surface 21a of the insulating substrate 21 is the same, the electronic component 10 can be mounted on the printed circuit board 20 so that the bottom surface 12a of the housing 12 and the surface 21a of the insulating substrate 21 are parallel to each other.

In addition, it is ideal for the entire straight portion of the tip of the lead terminal 14 of the electronic component 10 to be in contact with the first land 23, but depending on the shape of the lead terminal 14, it is unavoidable that some solder will be sandwiched between the tip of the lead terminal 14 and the first land 23. Taking this into consideration, it is preferable that the thickness of the base layer 24 is greater than the thickness of the first land 23.

Figures 6 to 13 are cross-sectional views showing the process steps of an embodiment of a method for manufacturing a component mounting board.

First, prepare a printed circuit board 20 before forming the solder resist shown in FIG. 6. This printed circuit board 20 has an insulating substrate 21 as a base, and a first land 23 and a second land 26 are arranged at a distance from each other on the surface 21a of the insulating substrate 21. The first land 23 and the second land 26 can be formed by plating the entire surface 21a of the insulating substrate 21 with copper and removing unnecessary portions.

Figure 7 is a cross-sectional view of the printed circuit board 20 after the solder resist 27 has been formed. The solder resist 27 is applied to cover the surface 21a of the insulating substrate 21, the first land 23, and the second land 26. Then, the solder resist 27 is provided with an opening that constitutes a land opening 27a that exposes part or all of the first land 23, and a step region 27b that exposes the surface 21a of the insulating substrate 21 between the first land 23 and the second land 26.

The solder resist 27 may be formed by applying solder resist to the entire printed circuit board 20 using a photolithography method, and then removing the solder resist in predetermined positions to remove the solder resist in the land openings 27a and step regions 27b. Alternatively, a method may be used in which a screen mask having a pattern formed to open the land openings 27a and step regions 27b is used to selectively apply solder resist to the areas excluding the land openings 27a and step regions 27b. Note that the steps up to this point are carried out during the manufacturing process of the printed circuit board.

Next, solder paste 18 is applied. FIG. 8 is a cross-sectional view of the printed circuit board 20 after solder paste 18 has been applied to the first land 23. Solder paste 18 can be selectively applied to a predetermined portion of the first land 23. For example, a metal mask having openings at positions corresponding to the first land 23 is placed on the printed circuit board 20, and solder paste is supplied onto the metal mask, and the solder paste can be selectively applied by sliding a squeegee to fill the openings in the metal mask.

Next, the resin adhesive 17 is applied. FIG. 9 is a cross-sectional view of the printed circuit board 20 after the resin adhesive 17 has been applied. The resin adhesive 17, for example, a thermosetting resin, is formed in the step region 27b between the first land 23 and the second land 26.

The resin adhesive 17 can be formed by discharging a predetermined amount from the outlet of a dispenser at a predetermined position on the surface 21a of the insulating substrate 21 in the step region 27b, for example, at a position adjacent to the base layer 24. When discharged from the dispenser, the resin adhesive 17 has a hemispherical cross-sectional shape that protrudes upward from the surface 21a of the insulating substrate 21. This hemispherical resin adhesive 17 may be formed at multiple locations in the step region 27b. The resin adhesive 17 is preferably thermosetting, which solidifies through a chemical reaction when heated.

Here, it is necessary to apply the resin adhesive 17 so that it protrudes above the upper surface of the solder resist 27. In other words, the protruding height must be sufficiently higher than the depth of the step region 27b, i.e., the sum of the film thickness of the second land 26 and the film thickness of the solder resist 27 that covers it. The reason for this is as follows.

As explained with reference to FIG. 2, the electronic component 10 has the distal end 12a1 of its bottom surface 12a in contact with the surface of the solder resist 27 that covers the second land 26. The remaining part of the bottom surface 12a is placed so as to cover the upper part of the step region 27b from the part in contact with the surface of the solder resist 27. In this state, the part of the bottom surface 12a that covers the upper part of the step region 27b and the surface 21a of the insulating substrate 21 must be fixed with the resin adhesive 17.

Next, the steps of placing the electronic component 10 on the printed circuit board 20 will be described with reference to Figures 10 to 13. The electronic component 10 is placed on the printed circuit board 20 using a mounter. First, the electronic component 10 is held by vacuum suction to the housing 12 with the mounter nozzle 30 of the mounter. Then, the electronic component 10 is moved to a predetermined position above the printed circuit board 20. This state is shown in Figure 10.

Next, the electronic component 10, which has been moved to a specified position, is lowered toward the printed circuit board 20 while being held by the mounter nozzle 30. As a result, the tip of the lead terminal 14 first comes into contact with the solder paste 18. As it is lowered further, the electronic component 10 tilts with the tip of the lead terminal 14 still resting on the solder paste 18, and the far end 12a1 of the bottom surface 12a of the housing 12 comes into contact with the surface of the solder resist 27 covering the second land 26. This state is shown in Figure 11.

Before the contact, it is preferable that the bottom surface 12a and the resin adhesive 17 come into contact, and then the bottom surface 12a spreads the resin adhesive 17 and adheres to it. In addition, temporary tilting of the electronic component 10 is acceptable to the extent that it does not cause problems with the vacuum suction of the housing 12 by the mounter nozzle 30.

The solder paste 18 has a viscosity that can temporarily hold the surface-mounted components. Therefore, when only the lead terminals 14 are in contact with the solder paste 18 and there is no other structure to hold the electronic component 10, it is difficult to overcome the viscosity of the solder paste 18 and lower the lead terminals 14 while maintaining the parallelism of the electronic component 10 and immersing them inside the solder paste 18. As a result, the electronic component 10 is temporarily tilted.

However, as shown in FIG. 11, only the distal end 12a1, which is a small part of the bottom surface 12a of the housing 12, is in contact with the surface of the solder resist 27 that covers the second land 26. Meanwhile, most of the bottom surface 12a is located above and away from the step region 27b. Therefore, as shown in FIG. 12, by further pressing down the housing 12 with the mounter nozzle 30, the electronic component 10 can be rotated in the direction in which the lead terminals 14 move downward in the drawing, centered on the position where the distal end 12a1 of the bottom surface 12a is in contact with the surface of the solder resist 27, and the lead terminals 14 can be sufficiently immersed in the solder paste 18. It is preferable that the position pressed down by the mounter nozzle 30 is in an area of the printed circuit board 20 that is not covered with the solder resist 27 in a plan view.

Here, it is preferable that the viscosity of the resin adhesive 17, for example, a thermosetting resin, is in a range that allows the lead terminals 14 to be spread with a force that is sufficiently smaller than the pressing force required to immerse them in the solder paste 18.

Figure 13 is a cross-sectional view of the component mounting board 1 after the electronic component 10 is placed on the printed circuit board 20 and solder reflow is performed. A cross-sectional view of the component mounting board 1. From the state of Figure 11, a heat treatment is performed to reflow the solder paste 18 to form solder 19, and the lead terminal 14 is mechanically fixed to the first land 23 in an electrically conductive state. At the same time, the resin adhesive 17 made of a thermosetting resin is hardened, and the housing 12 of the electronic component 10 is fixed to the surface 21a of the insulating substrate 21, i.e., the printed circuit board 20.

The resin adhesive 17 may be a thermosetting resin that hardens at a temperature lower than the melting temperature of the solder paste 18. The solder reflow process can be performed using a thermal sequence in which the housing 12 of the electronic component 10 is first fixed to the printed circuit board 20 in advance by maintaining the temperature at which the thermosetting resin hardens, and then the temperature is raised to melt the solder paste 18.

As described above, the component mounting board and manufacturing method of the present invention provide a component mounting board and manufacturing method that adheres and fixes a large electronic component with asymmetrically arranged lead terminals, such as a right-angle pin header, to a printed circuit board and securely connects the lead terminals to the lands for surface mounting.

REFERENCE SIGNS LIST 1 component mounting board 10 electronic component 12 housing 12a bottom surface 12a1 far end 12a2 near end 12b, 12c side surface 14 lead terminal 15 pin terminal 17 resin adhesive 18 solder paste 19 solder 20 printed circuit board 20a end of printed circuit board 21 insulating substrate 21a surface 23 first land 24 base layer 25 dummy portion 26 second land 27 solder resist 27a land opening 27b step region

Claims (13)

an electronic component having a housing including a bottom surface and a side surface, and a lead terminal protruding from the side surface of the housing;
a printed circuit board on which the electronic component is mounted, the printed circuit board having an insulating substrate, a first land arranged on a surface of the insulating substrate, and a base layer arranged on the surface at a distance from the first land;
Equipped with
a step region having a step with an upper surface of the base layer is disposed adjacent to the first land side of the base layer,
the bottom surface of the housing is fixed by a resin adhesive disposed in the step region, and the tip end of the lead terminal is in contact with the first land and fixed by solder,
A component mounting board, in which only a portion of the bottom surface of the housing, excluding most of the bottom surface of the housing on the far end side located away from the lead terminals, is disposed on the base layer. The component mounting board according to claim 1, wherein the base layer is made of a second land arranged on the surface of the insulating substrate and a solder resist that covers the second land. The component mounting board according to claim 2, wherein the thickness of the base layer is greater than the thickness of the first land. The component mounting board according to claim 2 or 3, wherein the step region is an opening in the solder resist, and the surface of the insulating substrate is exposed in the step region. The component mounting board according to any one of claims 1 to 4, wherein the bottom surface of the housing and the surface of the insulating substrate are generally parallel. The component mounting board according to claim 4 or 5, wherein the resin adhesive is disposed on the surface of the insulating substrate in the step region. The component mounting board according to any one of claims 1 to 6, wherein the resin adhesive is made of a thermosetting resin. The component mounting board according to any one of claims 1 to 7, wherein the lead terminals protrude in only one direction from the side surface of the housing. The component mounting board according to any one of claims 1 to 8, wherein the electronic component further has a pin terminal that protrudes from the housing in a direction different from the direction in which the lead terminal protrudes and does not directly contact the printed circuit board. The component mounting board according to claim 9, wherein the pin terminals of the electronic components protrude outside the edge of the printed circuit board. 1. A method for manufacturing a component mounting board, comprising surface-mounting an electronic component having a housing including a bottom surface and a side surface and a lead terminal protruding from the side surface of the housing, on a printed circuit board, the method comprising the steps of:
preparing a printed circuit board having a first land and a second land spaced apart from the first land on a surface thereof, the printed circuit board being prior to application of a solder resist;
forming a solder resist covering the second lands and forming a step on the printed circuit board;
Applying a solder paste covering the first lands;
applying a thermosetting resin to a position adjacent to the second land on the front surface of the printed circuit board between the first land and the second land;
pressing the housing of the electronic component so that the bottom surface of the housing abuts against the solder resist covering the second lands and is attached to the thermosetting resin, and the lead terminals are immersed in the solder paste, thereby mounting the electronic component on the printed circuit board;
and performing a heat treatment to harden the thermosetting resin and reflow the solder paste. The method for manufacturing a component mounting board according to claim 11, wherein the position at which the housing of the electronic component is pressed is in an area of the printed circuit board that is not covered by the solder resist in a plan view. The method for manufacturing a component mounting board according to claim 12, wherein when the housing of the electronic component is pressed, the electronic component is rotatable about a position where the bottom surface of the housing abuts against the solder resist.

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