JPH06218534A - Laser beam heating equipment - Google Patents

Abstract

PURPOSE:To perform soldering and to remove electronic parts which are soldered without giving thermal stress to a printed wiring board and the electronic parts. CONSTITUTION:The laser beam heating equipment includes a laser beam oscillator 1 to output a laser beam, an optical fiber member 2 to lead the outputted laser beam from the laser beam oscillator 1 to an object member 4 to be heated and an optical system 3 to condense the laser beam led by the optical fiber member 2 on an object part of the object member to be heated and the cross-sectional shape of an object part side end of the optical fiber member is conformed to the desired shape to be heated of the object member 4 to be heated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device using a laser beam as a heat source, and more particularly to a laser beam heating device suitable for reflow soldering high density surface mount components to a printed wiring board.

[0002]

2. Description of the Related Art In response to recent demands for miniaturization and high performance of electronic equipment, there is a remarkable improvement in the packaging density of electronic equipment. As the integration degree of semiconductor integrated circuits is improved, LS
The number of terminals in the I package tends to increase and the terminal pitch tends to decrease. In the current custom LSI, the number of terminals around 250 pins and the QFP having a terminal pitch of 0.5 mm are used.
(Four-way terminal type flat package; quad fla
t package) type ICs are becoming mainstream.

Chip components are also frequently used in passive circuit components such as resistors and capacitors, and their size is 1.6 mm × 0.8 mm or 1.25 mm ×.
0.6 mm products (so-called 1608 parts and 1206 parts) are beginning to be used. The printed wiring boards on which these components are mounted are also being multi-layered in layers, surface-mounted, and densified in wiring patterns in response to high-density mounting.

In the case of soldering an electronic component having such a fine terminal pitch to a printed wiring board, a conventional flow soldering method using a solder bath is preferable because a solder bridge is formed between the terminals. Absent. For this reason, there is a reflow soldering method in which cream solder is screen-printed on the soldering points of the printed wiring board in advance, the electronic parts are temporarily fixed with an adhesive, and then the solder is heated to melt and solder the solder. Has been adopted.

Heating methods used in this reflow soldering method include a collective connection in which the entire printed wiring board is heated and soldered, and an individual connection in which each electronic component is soldered. As the heating method for batch connection, infrared reflow that heats using infrared rays emitted from an infrared lamp or the like, vapor phase reflow that heats through the printed wiring board in the saturated vapor phase of the inert liquid, or hot air to the printed wiring board. There is hot-air reflow to blow. In addition, as a heating method for individual connection, there are laser reflow using laser light, pulse heating in which a heater is applied to the connection portion, and pulse current is applied.

In order to repair a conventional printed wiring board, when removing an electronic component, hot air is blown to heat it, or a soldering iron with a special iron tip attached to the shape of the electronic component to be removed is attached. The method of heating was taken.

[0007]

However, in the conventional reflow soldering method for collective connection, since the electronic parts to be soldered and the entire printed wiring board are heated, thermal stress is applied to the electronic parts and the board. It was being done. This thermal stress becomes mechanical stress due to the difference in the coefficient of thermal expansion of various members that make up electronic components and printed wiring boards,
There is a problem in that the reliability of these electrical connection points is reduced, and in some cases, electronic components may fail or the printed wiring board may be broken.

Further, in response to the reduction of the terminal pitch, the soldering land pitch and the land width of the printed wiring board are also reduced. As a result, in order to prevent the bridge between the lands, the thickness of the solder printing is thinner than before. Will be done. As described above, when the amount of solder in one soldering portion is reduced, the height of swelling of the molten solder from the land is also reduced. For this reason, the height of the component terminal rising from the plane due to the warp of the printed wiring board due to the heat applied during soldering becomes higher than the height of the molten solder from the land, and the terminal is not soldered. There is a problem that such a defect occurs.

In addition, when the defective electronic component is removed from the printed wiring board and replaced with a new electronic component, the same portion of the printed wiring board remains in the same position for a long time during the removal and the mounting. Since it is heated, there has been a problem that pattern peeling due to thermal stress and failure of surrounding electronic components are likely to occur.

Laser heating, pulse heating, etc., which are heating methods that can be individually connected, do not cause thermal stress, but laser irradiation and / or laser irradiation can be performed for each terminal of the electronic component to be soldered. Since the pulse current is applied, there is a problem that the soldering takes too much time and productivity is extremely deteriorated. Further, there is a problem that the failed electronic component cannot be removed by laser reflow or pulse heat.

In view of the above problems, the main object of the present invention is to reduce the thermal stress applied to electronic parts and printed wiring boards, to perform soldering with high reliability, and to improve the yield of products. Is. Another object of the present invention is to reduce the thermal stress applied to the printed wiring board and other electronic components and remove the defective electronic component from the printed wiring board.

[0012]

According to the present invention, there is provided a laser oscillator for outputting a laser beam, an optical fiber member for guiding the output laser beam from the laser oscillator to a member to be heated, and a laser guided by the optical fiber member. An optical system for condensing light to a target portion of a target member to be heated, the cross-sectional shape of the end portion of the target portion of the optical fiber member, by adjusting the target member to be heated shape desired to solve the above problems. It is a solution. Further, in the present invention, the member to be heated may be the member to be soldered, and the portion to be heated may be the portion to be soldered.

[0013]

In the laser light heating apparatus of the present invention, the laser light from the laser oscillator is used as a heat source to guide the laser light to the soldering point of the component to be soldered by the optical fiber member and the end of the optical fiber member at the soldering point side. It is possible to selectively heat only the terminal portion of the component to be soldered by molding the shape of the part according to the terminal arrangement shape of the component to be soldered. This makes it possible to solder other electronic components without applying thermal stress. Also, when removing a defective electronic component from the printed wiring board, the defective component can be removed without applying thermal stress to other electronic components.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1A is a schematic configuration diagram of a first embodiment in which the laser light heating device of the present invention is applied to a soldering device. In the figure, from the laser oscillator 1 which is a heat source for soldering,
Laser light is guided to the electronic component 4 which is the soldering target member using the optical fiber bundle 2 which is the optical fiber member. An optical system 3 including a condenser lens is provided at the end of the optical fiber bundle 2 on the side to be soldered so that the energy of the laser light can be concentrated at the soldering location. Since the laser oscillator 1 uses the laser light output as a heat source, stabilization of the oscillation frequency and control of the oscillation mode can be simplified.

A cross section AA of the optical fiber bundle 2 on the laser oscillator 1 side in FIG. 1A is shown in FIG. 1B, and a cross section BB on the electronic component 4 side to be soldered is shown in FIG. 1C. ).
In the present embodiment, the cross-sectional shape of the optical fiber bundle 2 on the laser oscillator side is circular, but the shape is not limited to this and may be matched with the shape of the optical output terminal of the laser oscillator 1.

Although the cross-sectional shape of the optical fiber bundle 2 on the electronic component 4 side is rectangular, the optical fiber bundle 2 has a structure in which a large number of extremely thin optical fibers are bundled, so that the electronic component 4 to be soldered is used. It is possible to change into various shapes (for example, circle, square, etc.) according to the terminal shape of.

FIG. 2 is a diagram showing a soldering state by laser light. In the optical system 3, the focus of the laser light guided by the optical fiber bundle 2 is set at the soldering portion of the terminal of the electronic component 4. A focus device 6 for adjusting the focus and a focus knob 7 thereof are provided. By rotating the focus knob 7 to the left and right, the height from the surface of the printed wiring board can be adjusted up and down while keeping the entire optical system 3 horizontal.

Next, a soldering method using the laser light heating apparatus of the present invention will be described. On a printed wiring board on which a required wiring pattern has been formed and a required lamination process has been performed, a resist is screen-printed on portions other than the land portion to be soldered. Next, cream solder is screen-printed on the land portion to be soldered. Next, the electronic component having the terminal portion preliminarily solder-plated is temporarily fixed to the printed wiring board with an adhesive. Up to this point, the process is the same as in normal reflow soldering.

On the other hand, in the soldering apparatus, the shape of the end of the optical fiber is matched with the shape of the electronic component to be soldered. Next, the optical system 3 of this device is set on the printed wiring board to which the electronic component 4 is temporarily fixed. At this time, the focus knob 7 is adjusted so that the focus of the laser light is aligned with the soldering point. This focusing may be performed in conjunction with a mechanism for recognizing the position of the electronic component 4 to be soldered and adjusting the mutual positions of the optical system 3 of the present apparatus or the printed wiring board.

Next, the laser oscillator 1 is oscillated to irradiate the soldering points of the electronic component 4 with laser light. Then,
The heat of the laser light melts the screen-printed solder, and the terminals of the electronic component 4 are collectively soldered. At this time, since the laser light is applied only to the soldered portion, it does not give thermal stress to other electronic components and the printed wiring board.

Even when the electronic component is removed from the printed wiring board for the purpose of repairing the faulty printed wiring board, the same procedure can be performed according to the shape of the end portion of the optical fiber of the present device to the electronic component. .

FIG. 3 is a schematic configuration diagram of a nameplate stamping machine according to the second embodiment of the present invention. The laser oscillator 1, the optical fiber bundle 2 and the optical system 3 are the same as those in the first embodiment. The nameplate stamping machine of the second embodiment is replaced by soldering,
By irradiating the plastic plate 10 with laser light,
The purpose is to give a desired marking. For this purpose, the end of the optical fiber bundle 2 on the side of the optical system is made into a character pattern or a graphic pattern for which marking is desired. When the marking is performed using this device, the expensive mold used for the conventional marking of the nameplate becomes unnecessary.

While the preferred embodiment has been described above, this is not meant to limit the scope of the invention. Those skilled in the art can devise various modifications based on the spirit of the present invention. For example, in the above embodiment, the optical fiber bundle was used for the optical fiber member of the present invention, but the present invention is applicable to this type of optical fiber bundle as long as the cross-sectional shape of the target site side end can be adjusted to the heated shape. There is no limitation, and an optical fiber member integrally or divided is also within the technical scope of the present invention.

[0024]

As described above, according to the present invention, only the heating target portion can be heated by matching the shape of the optical fiber bundle for guiding the laser light with the shape of the object to be heated. Therefore, there is an effect that the portion other than the heating target portion can be heated without applying thermal stress. Further, by applying the laser light heating apparatus of the present invention to soldering, there is an effect that soldering can be performed without applying thermal stress to the printed wiring board and electronic components.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a soldering device according to a first embodiment of the present invention.

FIG. 2 is a detailed view of an optical system of the soldering device.

FIG. 3 is a schematic configuration diagram of a marking device that is a second embodiment of the present invention.

FIG. 4 is a schematic view of a conventional laser soldering device.

[Explanation of symbols]

 1 Laser oscillator 2 Optical fiber member 3 Optical system 4 Heated member (soldered member) 5 Printed wiring board 6 Focus device 7 Focus knob 10 Plastic plate

Claims (2)

[Claims] 1. A laser oscillator that outputs a laser beam, an optical fiber member that guides the output laser beam from the laser oscillator to a heating target member, and a laser beam that is guided by the optical fiber member to a target portion of the heating target member. An optical system for illuminating, wherein the cross-sectional shape of the end portion of the optical fiber member on the side of the target portion is matched with a desired heated shape of the target member. 2. The laser light heating device according to claim 1, wherein the heating target member is a soldering target member and the heated region is a soldering target region.