JP2010080667A - Mounting board and mounting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mounting board on which circuit components can be mounted appropriately by a reflow method and which can reduce a required amount of solder. <P>SOLUTION: In the mounting board 1, a land 12 is formed around a through-hole 11. A resist layer 13 is formed on a mount surface and a rear surface of the mounting board so as to cover an outer peripheral part of the land 12. The land 12 has such a size that the land 12 is not connected to lands 12 formed around another adjacent through-holes 11. Furthermore, cream solder is applied on not only the exposed land 12 but also the resist layer 13 covering the land 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mounting substrate on which circuit components are mounted by soldering, and a mounting method for mounting circuit components on the mounting substrate.

  Conventionally, a mounting substrate on which circuit components (lead components) are mounted by soldering has been widely used (see Patent Document 1). A through hole (through hole) is formed on the mounting substrate, and a metal layer (land) for solder connection is formed around the through hole. The circuit component is mounted by inserting a lead into the through hole and soldering the lead to the land. There is a reflow method as a method of mounting circuit components. In this reflow method, a mounting substrate in which cream solder is applied to a land is used. First, for each circuit component to be mounted, the lead of the circuit component is inserted into the corresponding through hole and placed on the mounting substrate. Next, the mounting substrate on which each circuit component to be mounted is placed is placed in a heating furnace, the cream solder applied to the lands is melted, and the leads are soldered to the lands.

  The mounting board needs to form a through hole having a diameter corresponding to the thickness of the lead of the circuit component to be mounted. For this reason, as the lead has a thicker circuit component, the diameter of the through hole becomes larger and the amount of solder necessary for mounting also increases. Therefore, when a circuit component such as a connector having a thick lead is mounted by the above-described reflow method, since the land area to which the cream solder is applied is limited, connection failure due to insufficient solder tends to occur. Therefore, circuit components with thick leads have been soldered by a flow method in which the leads are soldered manually or by supplying molten solder from the back surface of the mounting substrate. As described above, in addition to the reflow method, the circuit component is mounted by performing a manual operation or a flow method, so that the mounting process for mounting the circuit component is complicated, resulting in an increase in cost.

  Note that it is conceivable to increase the land area in order to increase the amount of cream solder to be applied. However, if the land area is increased, the mounting efficiency of the circuit components decreases. Moreover, the general mounting board | substrate has formed the resist layer in parts other than a land. In order to increase the amount of solder for fixing the lead, it is conceivable to apply cream solder on the resist layer around the land. However, the resist layer has a lower thermal conductivity than a land that is a metal. For this reason, in order to increase the amount of solder, if the solder is spread not only on the land but also applied to the peripheral resist layer, the solder applied to the resist layer cannot be properly melted by the reflow method. In addition, a defect such as a short circuit between adjacent through holes caused by unmelted solder may occur.

  Therefore, in the mounting of circuit components by the reflow method, a proposal has been made to use a tine plate for supplying solder to the through hole in order to prevent the above-described connection failure due to insufficient solder (see Patent Document 2). . The tine plate has a hole corresponding to a through hole for supplying solder, and is a substrate different from the mounting substrate in which the solder supplied to the through hole is attached to the periphery of the hole. The circuit component is mounted by the reflow method in a state where the hole of the tine plate is aligned with the through hole of the mounting substrate and the lead of the circuit component is inserted from the tine plate side. In this reflow method, the solder adhered around the hole in the tine plate is melted and supplied to the through hole. Therefore, occurrence of poor connection of circuit components due to insufficient solder can be suppressed.

There has also been proposed a method in which a conductive pattern extending radially from the land is formed around the land, and solder is applied in a circle including the conductive pattern (see Patent Document 3). Furthermore, a proposal has been made that a cream solder printing land for applying solder to be supplied to the through hole is provided continuously to the land, and a resist or the like is provided as a non-soldering portion inside the cream solder printing land ( (See Patent Document 4).
JP-A-8-181424 JP 2007-173342 A Japanese Utility Model Publication No. 5-41184 JP 2002-26497 A

  However, since Patent Document 2 uses a tine plate separately from the mounting substrate, there is a problem of an increase in cost due to an increase in the number of components.

  In Patent Document 3, it is necessary to increase the outer shape of the conductive pattern extending radially from the land as the amount of necessary solder increases. The interval between adjacent conductive patterns becomes wider toward the outside. Therefore, when the outer shape of the conductive pattern exceeds a certain size, the reflow method cannot properly melt the solder, and a defect such as a short circuit between adjacent through holes caused by unmelted solder may occur. is there.

  Further, in Patent Document 4, since a cream solder printing land for applying solder to be supplied to the through hole is provided continuously to the land, a space for providing the cream solder printing land must be secured. It cannot handle circuit parts such as connectors with a narrow interval.

  Further, in Patent Document 3, solder melted by the reflow method adheres to the conductive pattern, and in Patent Document 4, solder melted by the reflow method adheres to the land for cream solder printing. That is, there is a problem that extra solder is required for the conductive pattern and the solder land for cream solder printing.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a mounting board that can properly mount circuit components by a reflow method and can suppress the amount of necessary solder.

  Another object of the present invention is to provide a mounting method for mounting circuit components on the mounting substrate.

  The mounting board of the present invention has the following configuration in order to solve the above-described problems and achieve the object.

  The mounting board is formed with a plurality of through holes into which leads of circuit components to be mounted are inserted. The circuit component is, for example, a connector, a resistor, a capacitor, or a coil. The through hole is a so-called through hole. Further, on the mounting surface side of the circuit component, a metal layer and a resist layer covering the outer periphery of the metal layer are formed around the through hole. That is, the resist layer is not formed so as to be in contact with the outer periphery of the metal layer formed around the through hole, but is formed so as to cover the outer periphery of the metal layer. Therefore, although the outer shape of the metal layer formed around the through-hole is increased, the mounting efficiency of the circuit component is not substantially reduced. Furthermore, solder is applied not only on the metal layer not covered with the resist layer but also on the resist layer covering the metal layer.

  For this reason, when the reflow method of inserting the circuit component lead to be inserted into the through-hole and placing it in the heating furnace to mount the circuit component is performed, the portion of the resist layer covering the metal layer, that is, solder is applied. The portion that is present is sufficiently heated by the heat transferred from the metal layer. Therefore, the solder applied on the resist layer can be properly melted, and the occurrence of poor connection due to insufficient solder can be suppressed.

  Further, since the area of the metal layer not covered with the resist layer is not increased, the amount of molten solder adhering to the metal layer is not increased. That is, the amount of solder necessary for mounting circuit components can be suppressed.

  In addition, the metal layer may be continuously formed on the back surface that is the opposite surface of the mounting surface through the through hole. If it does in this way, the heat applied from the back surface of the mounting substrate can be used efficiently by the reflow method, and the solder applied to the resist layer can be more reliably melted.

  Also on this back side, a metal layer and a resist layer covering the outer periphery of the metal layer may be formed around the through hole. In this way, even if the melted cream solder flows to the back surface, it does not spread over the entire metal layer on the back surface side and can be fixed in the vicinity of the lead. Furthermore, the heat applied by the reflow method can be used more efficiently if the outer shape of the metal layer formed on the back surface side is made larger than the mounting surface side on which the circuit components are mounted.

  Moreover, what is necessary is just to divide | segment the metal layer currently formed in the periphery of an adjacent through-hole with the member whose heat conductivity is lower than this metal layer.

  Furthermore, the outer shape of the metal layer may be any shape such as a circle or a rectangle, but is preferably a rectangle from the viewpoint of circuit component mounting efficiency.

  According to the present invention, circuit components can be properly mounted by the reflow method, and the necessary amount of solder can be suppressed.

  Hereinafter, a mounting substrate according to an embodiment of the present invention will be described.

  FIG. 1 is a schematic view showing a state in which circuit components are mounted on a mounting board. FIG. 1A is a top view of the mounting substrate. FIG. 1B is a side view of the mounting substrate. Circuit components (lead components) are mounted on the mounting substrate 1 by soldering. In FIG. 1, a connector 5, a resistor 6, and a capacitor 7 are shown as mounted circuit components. The circuit component is mounted on the mounting substrate 1 by a reflow method described later.

  The mounting substrate 1 has a through hole 11 (through hole 11) for inserting a lead of each circuit component to be mounted. 2 and 3 are enlarged views of this through-hole portion. FIG. 2 shows a state before the cream solder is applied to the mounting surface, and FIG. 3 shows a state after the cream solder is applied to the mounting surface. 2A and 3A are plan views of the mounting surface. 2B and 3B are side cross-sectional views. FIG. 2C is a plan view of the back surface (the surface opposite to the mounting surface). 2 and 3 show two adjacent through holes 11. The outer shape of the through hole 11 is slightly larger than the thickness of the lead of the circuit component to be mounted.

  Around the through hole 11, a metal layer 12 (land 12) for solder-connecting leads of circuit components to be mounted is formed. The land 12 is electrically connected to the lead of the soldered circuit component. The land 12 is formed from the mounting surface to the back surface through the through hole 11. The external shape of the land 12 on the mounting surface and the back surface is rectangular. Here, the area of the land 12 is larger on the back surface than on the mounting surface.

  In FIG. 2, the lands 12 formed around the two adjacent through holes 11 are not connected. However, when the leads of the circuit components inserted into the two through holes 11 are electrically connected. The lands 12 formed around these two through holes 11 may be connected.

  Further, the mounting substrate 1 has a resist layer 13 covering the outer periphery of the land 12 formed on the mounting surface and the back surface. 2A, 2C, and 3A, the outer shape of the formed metal layer is indicated by a broken line. Further, in order to illustrate the area where the land 12 and the resist layer 13 are formed, the outer shape of the mounting substrate 1 is shown for convenience. Here, the mounting substrate 1 in which the land 12 and the region where the resist layer 13 is not formed is illustrated, but the resist layer 13 is formed in the region where the land 12 and the resist layer 13 are not formed. You may keep it.

Most of the lands 12 are covered with the resist layer 13 on the mounting surface and the back surface, and only a part of the periphery of the through hole 11 is exposed. The resist layer 13 is also formed in a region where no land 12 or circuit pattern (not shown) is formed. For example, as shown in FIG. 2B, the resist layer 13 is also formed between lands 12 formed around two adjacent through holes 11. The thickness of the resist layer 13 formed on the mounting surface and the back surface is substantially uniform.

As shown in FIG. 3, the mounting substrate 1 has cream solder 14 applied to the mounting surface. The cream solder 14 is applied not only on the exposed lands 12 but also on the through holes 11 and on the resist layer 13 covering the lands 12. That is, the cream solder 14 is applied to the area where the land 12 is formed on the mounting surface. In FIG. 3A, the land 12 located below the applied cream solder 14 and the resist layer 13 are also indicated by broken lines.

The area where the cream solder 14 is applied is slightly larger than the area where the land 12 is formed in FIG. 3A, but may be the same as the area where the land 12 is formed. Moreover, it may be slightly smaller than the range in which the lands 12 are formed. Further, the cream solder 14 is not applied to the back surface of the mounting substrate 1. However, when the cream solder 14 is applied to the mounting surface, a part thereof may pass through the through hole 11 and reach the back surface. 3B shows an example in which the cream solder 14 is applied so that the inside of the through hole 11 is filled about half, but the cream solder 14 may be applied so that the entire inside of the through hole 11 is filled. .

  Thus, the mounting substrate 1 has the resist layer 13 formed so as to cover the outer peripheral portion of the land 12 formed around the through hole 11. Moreover, the land 12 should just be a magnitude | size which does not connect with the land 12 formed in the circumference | surroundings of another through hole 11 adjacent. For this reason, although the outer shape of the land 12 formed around the through hole 11 is increased, the mounting efficiency of the circuit component is not substantially lowered. However, when the leads of the circuit components inserted into the two adjacent through holes 11 are electrically connected, the lands 12 formed around these two through holes 11 may be connected. Further, the cream solder 14 is applied not only on the exposed land 12 but also on the resist layer 13 covering the land 12.

  Next, a method for mounting circuit components on the mounting substrate 1 will be described. The circuit components are mounted by a reflow method. 4 and 5 are diagrams illustrating a process of mounting circuit components. FIG. 4A shows a state where cream solder is not applied, and the cream solder 14 is applied to the mounting substrate 1 as shown in FIG. 4B. Then, the circuit component to be mounted is placed on the mounting substrate 1. Specifically, for each circuit component to be mounted, the lead of the circuit component is inserted into the corresponding through hole 11 from the mounting surface side (see FIG. 4C).

  The mounting substrate 1 on which circuit components are placed is placed in a heating furnace. In the mounting substrate 1 placed in the heating furnace, the cream solder 14 directly applied to the lands 12 having high thermal conductivity is sufficiently heated and melted and flows into the through holes 11 (see FIG. 5A). Further, with a slight delay in time, the cream solder 14 applied to the resist layer 13 covering the land 12 is sufficiently heated and melted by the heat transmitted from the covering land 12. The cream solder 14 applied to the resist layer 13 covering the lands 12 is pulled to the cream solder 14 (the cream solder 14 applied directly to the lands 12) that has started to flow into the through holes 11 previously. And flows into the through hole 11 (see FIG. 5B).

  Circuit components such as a connector 5 to be mounted, a resistor 6 and a capacitor 7 are mounted on the mounting surface. For this reason, in the mounting substrate 1, the loss on the amount of heat applied is larger on the mounting surface side. As described above, the mounting substrate 1 has an area of the land 12 larger on the back surface than on the mounting surface. That is, it is possible to efficiently use the heat from the back surface side of the mounting substrate 1 and melt the cream solder 14 applied to the resist layer 13.

  After that, when the mounting substrate 1 is taken out from the heating furnace, the temperature of the melted cream solder 14 decreases, and adheres to and hardens in the surrounding metal (land 12 and circuit component leads) and through holes (FIG. 5). (See (C)). As a result, the lead of the circuit component is soldered to the through hole 11. That is, the circuit component is mounted on the mounting substrate 1.

  Thus, since the resist layer 13 is formed so as to cover the outer periphery of the land 12 on the circuit component mounting surface, the cream solder applied on the resist layer 13 covering the land 12 is sufficiently heated. Can be melted. Therefore, even in the case of a circuit component such as a connector having a thick lead, it is possible to suppress a connection failure due to insufficient solder. Moreover, since the land 12 can suppress the exposed portions on the mounting surface and the back surface, excess solder adhering to the land 12 by the reflow method can be suppressed. That is, the amount of solder necessary for mounting circuit components can be suppressed. Furthermore, since the land 12 and the resist layer 13 covering the outer periphery of the land 12 are formed around the through hole 11 on the back surface side, even if the melted cream solder 14 flows to the back surface, It is possible to prevent the entire land 12 from spreading.

  Further, the outer shape of the land 12 formed on the mounting surface or the back surface is not limited to a rectangle, but may be an ellipse shown in FIG. 6 or a perfect circle shown in FIG. Moreover, as shown to FIG. 6 (A) and FIG. 7 (A), the area | region which applies the cream hand 14 is good also as the rectangular shape circumscribed to the land 12, or FIG. 6 (B) or FIG. 7 (B). As shown in the figure, the corners may have a rectangular shape inscribed in the land 12. Furthermore, the same ellipse or perfect circle as the land 12 may be used. In addition, the area where the cream solder 14 is applied may be slightly smaller than or larger than the area where the land 12 is formed.

  Further, as shown in FIG. 8A, the thickness of the resist layer 13 between the lands 12 of two adjacent through holes 11 is the thickness of the land 12 and the thickness of the resist layer 13 covering the lands 12. The thickness may be the same as the sum of the two or a little thicker as shown in FIG. In this way, it is possible to more reliably prevent the adjacent two through holes 11 from being short-circuited by the solder melted by the reflow method.

It is the schematic which shows the state which mounted the circuit component on the mounting board | substrate. It is an enlarged view of the through-hole part of a mounting substrate. It is an enlarged view of the through-hole part of a mounting substrate. It is a figure explaining the process of mounting a circuit component. It is a figure explaining the process of mounting a circuit component. It is an enlarged view of the through-hole part of another mounting board. It is an enlarged view of the through-hole part of another mounting board. It is an enlarged view of the through-hole part of another mounting board.

Explanation of symbols

1-Mounting board 11-Through hole (through hole)
12-land (metal layer)
13-resist layer 14-cream solder

Claims (7)

In a mounting board that has a plurality of through holes into which leads of circuit components to be mounted are inserted,
On the mounting surface side of the circuit component, a metal layer is formed around the through hole, and a resist layer covering the outer peripheral portion of the metal layer is formed,
Furthermore, the mounting board | substrate which apply | coated the solder not only on the said metal layer not covered with the said resist layer but on the said resist layer covering the said metal layer. The metal layer is formed continuously from the mounting surface to the back surface that is the opposite surface through the through hole,
The mounting substrate according to claim 1, wherein a metal layer is also formed around the through hole on the back surface side.   The mounting substrate according to claim 2, wherein an area of a metal layer formed around the through hole is larger on the back surface side than on the mounting surface side. The mounting substrate according to claim 2, wherein the metal layer on the back surface side also covers an outer peripheral portion with a resist layer.   The mounting substrate according to any one of claims 1 to 4, wherein the metal layer formed around the adjacent through hole is divided by a member having a lower thermal conductivity than the metal layer.   The external shape of the said metal layer is a mounting substrate in any one of Claims 1-5 which is a rectangle. A mounting method for mounting a circuit component on the mounting board according to claim 1,
For each circuit component to be mounted on this mounting substrate, insert the lead of the circuit component into the corresponding through hole, and place it on the mounting substrate.
A mounting method in which the mounting substrate on which the circuit component to be mounted is placed is placed in a heating furnace, and the circuit component placed on the mounting substrate is soldered by a reflow method.

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