JP2000151085A - Electronic circuit device and electronic part wiring board mounting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electronic circuit device and a wiring board mounting method for electronic parts in which the electronic parts are mounted on a wiring board with a high density and generation of failures during the mounting on the wiring board is less. SOLUTION: An electronic part 2 is mounted on lands 6 on a wiring board 4. Junction electrodes 8 of the electronic part 2 are junctioned with the lands 6 via bumps 10. The bumps 10 are constituted of solder fusing parts 12 which junction the junction electrodes 8 with the lands 6 and supporting parts 14 which support the electronic part 2 on the lands 6. A melting point of the supporting parts 14 is higher than one of the solder fusing parts 12, and even the solder fusing parts 12 fuse by the reflow method the supporting parts 14 do not fuse. Therefore, the electronic part 2 can be supported by the supporting parts 14, a rolling phenomenon can be prevented and a generation of failures can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic circuit device in which an electronic component and a wiring board are connected via bumps, and a method for mounting the electronic component on a wiring board.

[0002]

2. Description of the Related Art In recent years, electronic devices have been rapidly reduced in size. In order to reduce the size of electronic devices, it is required to mount electronic components on a wiring board at high density.

At present, as a general high-density mounting method of electronic components, there is a bump mounting of electronic components. FIG. 3 shows this bump mounting. The electronic component 2 is connected to the land 6 of the wiring board 4.
On top, it is mounted with solder bumps 30. The connection electrode 8 of the electronic component 2 is coated on its side surface with a material 32 that does not wet with solder. The connection electrodes 8 are connected to the lands 6 by the solder bumps 30, and the electronic components 2 are mounted on the wiring board 4. In bump mounting, the occupied area of the electronic component when mounting the wiring board can be reduced to about the size of the electronic component, and high-density mounting of the electronic component on the wiring board is possible. In such bump mounting, a reflow method using a solder paste is generally used.

In the reflow method, a solder paste called cream solder in which a solder powder and a flux are mixed is printed and applied on a land of a wiring board, and an electronic component is mounted on a target position on the printed and applied solder paste. Thereafter, a method of directly or indirectly melting the solder paste to mount the electronic component on the wiring board.

[0005]

In the bump mounting using the reflow method, as described above, high-density mounting of electronic components on a substrate becomes possible. However, the solder bump 30
If the balance of the surface tension of the solder bumps 30 is lost when is melted, the electronic component 2 may tilt. This phenomenon is called a rolling phenomenon. FIG. 4 is a side view of FIG. 3 and shows how electronic components are mounted when a rolling phenomenon occurs. When the rolling phenomenon occurs, a high portion and a low portion of the bump are generated in the electronic circuit device. In electronic circuit devices, electronic components 2
A thermal cycle occurs when the internal switch is repeatedly turned on and off. At this time, a thermal stress is applied to the solder bumps 30 due to a difference in thermal expansion coefficient between the electronic component 2 and the wiring board 4. Thermal stress is particularly concentrated on a low portion of the solder bump 30 generated by the rolling phenomenon, so that the solder bump 30 is cracked. As described above, when the rolling phenomenon occurs, a defect occurs in the electronic circuit device.

As a method for preventing such a rolling phenomenon, a spacer 50 is provided between the electronic component 2 and the wiring board 4.
Are disclosed. This method is shown in FIG. The spacer 50 serves as a pedestal for the electronic component 2 and prevents the electronic component 2 from tilting during reflow.

However, in the method of forming the spacer 50, when the height of the solder bump 30 is not sufficiently higher than the height of the spacer 50, the connection electrode 8 of the electronic component 2 does not come into contact with the solder bump 30. Even after the solder bumps 30 are melted, the solder bumps 30 and the connection electrodes 8 are not joined. Therefore, it is necessary to make the height of the solder bump 30 sufficiently higher than the height of the spacer 50. However, if the height of the solder bumps 30 is made sufficiently high, when the electronic component 2 is placed on the solder bumps 30, the solder of the solder bumps 30 pushed out by the electronic component 2 will not be used.
Short circuit with the surrounding components, and a defect occurs in the electronic circuit device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an electronic circuit device and an electronic circuit device in which electronic components are mounted on a wiring board at high density and in which the occurrence of defects during mounting on the wiring board is small. An object of the present invention is to provide a method for mounting a component on a wiring board.

[0009]

SUMMARY OF THE INVENTION The present invention provides a wiring board having a component mounting land, an electronic component mounted on the land and having an electrode for connection to the land, A bump electrically and physically connecting the land to the land, wherein the bump has a fused portion and a column having a melting point higher than the fused portion, and the electronic portion is formed by the column. The component is supported on the land.

As described above, the electronic circuit device of the present invention has a melted portion and a pillar having a melting point higher than the melted portion in the bump. In this electronic circuit device, since the connection electrodes and the lands are connected by bumps, the area occupied by the electronic component on the wiring board may be as large as the electronic component, and the electronic component can be mounted on the wiring board at a high density. It is possible. Further, since the electronic components are supported by the pillars of the bumps, the rolling phenomenon can be prevented, and the occurrence of defects during mounting on the wiring board is small.

The present invention also relates to a method for mounting a wiring board on an electronic component, the method comprising forming a bump having a melting portion and a pillar having a melting point higher than the melting portion on a land of the wiring board having a component mounting land. An electronic component having an electrode for connection to the land is placed on the bump, and the electronic component is supported on the land by a pillar portion of the bump.

As described above, in the method of mounting an electronic component on a wiring board according to the present invention, the rolling phenomenon is prevented and the occurrence of defects is reduced by supporting the electronic component on the land with the pillar portion of the bump. Is possible.

[0013]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1A is a plan view of the electronic circuit device 1 according to the present embodiment, and FIG. Electronic component 2
Are mounted on the lands 6 of the wiring board 4. The electronic component 2 has a connection electrode 8 and is connected to the land 6 via the bump 10. The bump 10 is composed of a solder melting part 12 and a support part 14. As will be described later, the solder fusion portion 12 connects the connection electrode 8 and the land 6, and the support portion 14 supports the electronic component 2 on the land 6.

As described above, the electronic circuit device 1 of the present embodiment
Connects the electronic component 2 and the land 6 with bumps 10. Therefore, the area occupied by the electronic component 2 on the wiring board 4 may be approximately the same as the electronic component 2. Therefore, the electronic components 2 can be mounted on the wiring board 4 with high density.

Next, a method for mounting the electronic component of the present embodiment on a wiring board will be described with reference to FIG.

First, the bump 1 is formed on the land 6 of the wiring board 4.
Then, the column portions 14 of 0 are formed (FIG. 2A). Post 14
Is formed by a wire bonder device or a bump bonder device. The height of the support portion 14 may be about the distance between the wiring board 4 and the electronic component 2 necessary for mounting the electronic component 2 on the wiring board 4, and in this embodiment, it is about 80 μm. Post 14
May be a material having a melting point higher than that of the solder melting portion 12 and usable in a wire bonder or a bump bonder, such as gold or copper. Further, either a conductive material or a non-conductive material may be used, and solder having a higher melting point than the solder melting portion 12 may be used. Note that the support 14 may be formed by a printing device. In the present embodiment, gold is used as the material of the support portion 14.
Further, in the electronic circuit device of the present embodiment, one bump has two pillar portions, respectively, but the number of pillar portions for one bump may be appropriately determined according to the size of the electronic component and the like. .

After forming the support portion 14, the electronic component 2 is mounted on the land 6 by a reflow method. First, a solder paste is applied to the land 6 by a screen printing method to form a solder melting portion 12 of the bump 10 (FIG. 2B). The thickness of the screen mask may be arbitrary as long as it is thicker than the above-described support portion 14. In this embodiment, a screen mask having a thickness of about 300 μm is used. The material of the solder paste is
It is a mixture of a conductive material having a lower melting point than the above-described support portion 14 and flux. As conductive materials, tin, lead,
Simple substances such as silver and alloys are used. In the present embodiment, an alloy of silver and tin was used as the conductive material. Next, so that the connection electrode 8 is in contact with the solder melting portion 12,
The electronic component 2 is placed on the solder fusion part 12 (FIG. 2).
(C)). Thereafter, the solder melting portion 12 is heated to melt the solder melting portion 12, connect the connection electrode 8 and the land 6, and press the electronic component 2 in the direction of the land 6, thereby fixing the electronic component 2 on the land 6 (FIG. 2 ( d)). In the heating, the solder melting portion 12 may be locally heated, or the entire wiring board 4 may be heated. The heating is performed at a temperature higher than the melting point of the solder melting part 12 and lower than the melting point of the support part 14. By heating at such a temperature, even when the solder melting portion 12 is melted, the support portion 14 made of a material having a higher melting point than the solder melting portion 12 does not melt. Since the support 14 does not melt, the support 14 can support the electronic component 2.

As described above, when the electronic component 2 is mounted on the wiring board 4, the electronic component 2 is supported by the pillar 14 of the bump 10. Therefore, when the electronic component 2 is mounted on the wiring board 4 by using the reflow method, it is possible to reduce the occurrence of the rolling phenomenon in which the electronic component 2 tilts.

When fixing the electronic component 2 on the land 6 by melting the solder melting portion 12, the electronic component 2 is
Through the land 6. However, since the support 14 is provided, the electronic component 2 cannot be pressed below the height of the support 14. Therefore, it is possible to reduce the amount of solder in the solder melting portion 12 pushed to the periphery of the electronic component 2, and it is possible to prevent the occurrence of a failure due to a short circuit between the electronic component 2 and the surrounding components.

[0021]

As described above, in the present invention, since the connection electrodes and the lands are connected by bumps, it is possible to mount electronic components on the wiring board with high density. In addition, since the electronic components are supported by the pillars of the bumps during reflow, the rolling phenomenon can be prevented, and the occurrence of defects during mounting on the wiring board can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an electronic circuit device according to an embodiment.

FIG. 2 is a process diagram showing a process of mounting the electronic component of the embodiment on a wiring board.

FIG. 3 is a schematic view of a conventional bump mounting.

FIG. 4 is a schematic diagram showing a rolling phenomenon.

FIG. 5 is a schematic view of bump mounting using a conventional spacer.

[Explanation of symbols]

Reference Signs List 1 electronic circuit device, 2 electronic components, 6 lands, 8 connection electrodes, 10 bumps, 12 solder fusion parts, 14 support columns, 30 solder bumps, 32 materials that do not get wet with solder,
50 Spacer.

Claims (2)

[Claims] A wiring board having a component mounting land; an electronic component mounted on the land and having a connection electrode with the land; and an electrical and physical connection between the connection electrode and the land. And a bump having a melting point and a supporting portion having a melting point higher than the melting portion, and the supporting portion supports the electronic component on the land. An electronic circuit device characterized by the above-mentioned. 2. A bump having a melting portion and a pillar having a melting point higher than the melting portion is formed on a land of a wiring board having a component mounting land, and an electronic component having an electrode for connection with the land is bumped. And mounting the electronic component on the land with a support portion of the bump.