JPH1065285A - Mounting structure for electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To approximately uniformize the heights of electronic components, mounted on both sides of a printed wiring board, by forming protrusions and recessions or curved surfaces beforehand, so that the height of each component on both the board surfaces are the same after their mounting. SOLUTION: A flux is applied beforehand onto a printed wiring board 1 having protrusions and recessions, and solder ribbons are punched out by a punch, and are mounted on the pads of the board and reflowed by using a μ-press method. This μ-press method enables supplying solder, even if the printed wiring board 1 has protrusions and recessions. After mounting electronic components 21-23 on a printed wiring board 1 after supplying the solder, reflowing is performed and soldering is completed. When component mounting on one surface is finished, mounting on the other surface is performed. By doing this way, it becomes possible to approximately uniformize the heights of the electronic components after having been mounted.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mounting structure for electronic components, and more particularly to a mounting structure for electronic components on a printed wiring board.

[0001]

2. Description of the Related Art As a method for mounting an electronic component on a printed circuit board, as shown in FIG.
There is a method described in JP-A-89-89.

FIGS. 3 (a) and 3 (b) are an external perspective view and a cross-sectional view taken along the line BB, respectively, showing a surface mounting method of an electronic component described in the publication.

In FIG. 3, a connector 101 (electronic component) in which a number of connection pins are arranged is formed by a housing 102, and a lead 10 is provided on the back of the housing 102.
3 is provided, and a hole 105 is formed in a portion in contact with the printed circuit board 104. On the printed circuit board 104, a projection 106 and a pad 108 connected to a circuit conductor 107 are formed.

A hole 105 of the housing 102 is fitted into a projection 106 of the
Is fixed to the printed circuit board 104, and the leads 102 are soldered to the pads 108, so that the external force applied to the electronic component is received by the projections of the printed circuit board, so that no external force is applied to the soldered portions between the leads and the pads.

In Japanese Patent Laid-Open Publication No. 3-101188, as shown in FIG. 4, a concave portion 203 is provided below a semiconductor integrated circuit 202 mounting region of a printed wiring board 201, and a chip component 204 is mounted in the concave portion 203. It describes a method of mounting electronic circuit components.

The leads 205 of the semiconductor integrated circuit 202 are fixed to the printed wiring board 201 by solder 206.

As described above, the mounting method shown in FIG. 4 achieves high density without increasing the component height after mounting electronic circuit components.

Further, a functional module using a multilayer printed wiring board has an uppermost layer pattern 301 and a lowermost layer pattern 302 which are stacked as shown in FIG. In addition, there is a method of mounting the surface mount component 306 on the interior pattern 305 of the lowermost layer pattern 302 exposed at the concave portion 304 of the uppermost layer pattern 301.

Such a mounting method is disclosed in, for example,
No. 165677.

[0010]

However, in the method shown in FIG. 3, since a flat printed board is used except for the projections for fixing the electronic components, unevenness in the height of the components after mounting occurs. However, there is a problem that a dead space occurs.

In the method shown in FIG. 4, a special method for forming a concave portion for mounting a chip component on a printed wiring board is used, so that there is a problem that the manufacturing cost of a printed circuit board is increased.

Further, when changing constants or repairing chip components, it is necessary to remove the semiconductor integrated circuit mounted thereon. Further, during the reflow, heat is hardly transmitted to the parts below the semiconductor integrated circuit, and a soldering failure occurs.

In the method shown in FIG. 5, in the case of a multilayer printed circuit board, it is possible to eliminate the unevenness of the height of the component after mounting, but it is not applied to the mounting method of an electronic component using a single-layer printed circuit board. Can not.

Also, in order to expose the inner layer pattern of the multilayer printed wiring board, the printed wiring board is cut out by a router, or a hole is formed in the board before lamination, and the protrusion of the adhesive at the time of lamination is considered. Need to be stacked. Therefore, the wiring density decreases. Further, when the shaving is multi-layered, unevenness of the copper foil occurs due to undulation of the copper foil after lamination and thermal shrinkage of the equipment, and the production stop is deteriorated. In addition, the cost rises due to the deterioration of the yield.

Furthermore, the above-described mounting method is not suitable for application to portable devices and the like, which are rapidly becoming smaller and thinner.

An object of the present invention is to provide a mounting structure of an electronic component capable of making the height of an electronic component mounted on a printed wiring board substantially uniform with a simple structure.

[0017]

SUMMARY OF THE INVENTION According to the present invention, there is provided a mounting structure of an electronic component in a structure in which an electronic component such as a semiconductor integrated circuit is mounted on a printed wiring board. Have the same irregularities or curved surfaces on both sides.

Preferably, the irregularities are formed by a press method in the final step of manufacturing the substrate.

With such a configuration, in the present invention, high yield and low cost can be achieved without lowering the wiring density.

Further, the dead space can be minimized, and the device can be reduced in size and thickness.

[0021]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIGS. 1 (a) and 1 (b) are a plan view and an AA sectional view, respectively, showing an embodiment of the present invention.

In FIG. 1, the upper surface and the lower surface of a printed wiring board 1 made by a subtractive method, an additive method, a build-up method or the like are provided with surface mount components (SMD: Surface Mo) such as a semiconductor integrated circuit.
unt Device (hereinafter referred to as “electronic component”) 21
To 23 are implemented. The electronic components 21 to 23 are fixed to the printed wiring board 1 by a bonding material 3 such as a solder or an adhesive.

In FIG. 1, the electronic component 21 is, for example, Qu
Although an LSI package such as ad Flat Package, 22 indicates a tantalum capacitor, and 23 indicates a chip component such as a resistor and a capacitor, it is apparent that other components such as a transistor, a diode, and a crystal may be used.

The printed wiring board 1 is formed with irregularities so that the height after mounting electronic components is substantially constant.

The flow of forming the unevenness of the printed wiring board 1 is as follows.
First, at the time of circuit design, the unevenness of the printed wiring board 1 is designed based on the component information and the circuit information so that the height after mounting is constant, and is formed by using a pressing method with a mold in the final step of substrate manufacturing. .

Next, a method for mounting electronic components on the printed wiring board 1 will be described.

The solder is supplied to the printed wiring board 1 having the unevenness. Preferably, the solder is supplied by applying a flux to the printed wiring board 1, punching a solder ribbon with a punch, mounting the solder ribbon on a pad (not shown) of a board, and performing a reflow μ press method. By this μ-press method, solder can be supplied even if the printed wiring board 1 has irregularities.

After supplying the solder, the printed wiring board 1 is washed and flux is applied again. Thereafter, the electronic component is mounted on the printed wiring board 1 by a normal component mounting apparatus.

In mounting the electronic components, the printed wiring board 1 is formed with irregularities. Therefore, it is desirable to prepare a backup plate that sits at a predetermined position so as to match the irregularities.

After the components are mounted, reflow is performed to complete the soldering.

When component mounting on one surface is completed, mounting on the other surface is performed.

In this way, the height after mounting the electronic components is substantially constant.

FIG. 2 is a sectional view showing another embodiment of the present invention.

In FIG. 2, the difference from the embodiment shown in FIG. 1 is that the electronic component 21 is not the bare chip 4. That is, among the electronic components to be mounted, LSI
Is not a normal packaged product.

In this embodiment, since the bare chip 4 is used, it is preferable to mount the bare chip before mounting other electronic components in consideration of the contamination of the substrate electrode and the like in the manufacturing flow.

The other points are the same as those of the embodiment of FIG. 1, and the description thereof will be omitted to avoid redundancy.

[0038]

As described above, according to the present invention, since the heights of the electronic components mounted on both sides can be made substantially constant, the dead space can be minimized. Moreover, it is particularly effective when a single printed wiring board is applied.

Further, it is possible to reduce the size and thickness of portable devices such as an electronic organizer, a mobile phone, a PHS, a pager, a handy word processor, and a composite terminal thereof.

Further, the structural design becomes very easy.

In the present invention, since the press method is used as the method for forming the unevenness of the printed wiring board, a higher yield can be obtained and the manufacturing cost can be reduced as compared with a manufacturing method such as spot facing or pasting. Can be

[Brief description of the drawings]

FIG. 1 is a plan view and an AA plane cross-sectional view showing one embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

FIG. 3 is an external perspective view and a sectional view showing a first mounting method of a conventional electronic component.

FIG. 4 is a sectional view showing a second mounting method of a conventional electronic component.

FIG. 5 is a sectional view showing a third method for mounting an electronic component in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed wiring board 3 Joining material 4 Bare chip 21-23 Electronic component

Claims (3)

[Claims] In a mounting structure of an electronic component such as a semiconductor integrated circuit on a printed wiring board, the printed wiring board has unevenness or a curved surface such that the height of each component after mounting the electronic component is substantially constant on both sides. An electronic component mounting structure, characterized in that: 2. The electronic component mounting structure according to claim 1, wherein the unevenness or the curved surface of the printed wiring board is formed by a press method. 3. The mounting structure according to claim 1, wherein the electronic component of the printed wiring board is a bare chip.