JPH03204171A - Light beam soldering device - Google Patents

Abstract

PURPOSE:To miniaturize the device and to allow the efficient melting of solder by executing soldering by using a metal vapor discharge lamp of a short arc type having the strong emission spectra of UV rays. CONSTITUTION:The light from a visible ray region to a UV region is radiated much from the metal vapor discharge lamp 1 and the solder 10 is efficiently heated up by the absorption of the light from the visible ray region to the UV region. Since the inter-electrode distance of the metal vapor discharge lamp 1 is short, the light is condensed to an extremely small illuminating diameter by condenser mirrors 3, 7 so as to have the high energy density on the surface to be irradiated. The high-efficiency treatment is thus executed with an extremely small light source.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light beam soldering device that performs various types of soldering including mounting of electronic components.

[Prior Art] For example, in the field of mounting electronic components onto printed wiring boards, various soldering techniques have been developed. Among these methods, from the perspective of eliminating thermal damage to electronic components, conventional methods have been used to irradiate the solder with a light beam to heat only the solder in a non-contact and short time period, causing reflow soldering. .

The light source of such a light beam soldering device includes:
A laser such as a YAG laser is used because it can focus light on an extremely small spot. However, since YAG laser oscillation devices are expensive, light beam soldering devices using discharge lamps have also been developed.

The discharge lamp used as a light source for this light beam soldering device has a small light emitting part, so it can focus light on a minute spot.

■Equipped with a high-brightness light source, the illuminance at the focal point is high.

■As a thermal light source, it has a strong emission spectrum in the near-infrared region.

For these reasons, xenon short arc lamps are used (see, for example, the magazine "Electronic Materials J, September 1986 issue, pages 71 to 75)".

[Problems to be Solved by the Invention] Needless to say, the process of soldering involves reflowing solder and then cooling it to join parts to be joined. Taking this into consideration, it is thought that xenon short arc lamps, which have a strong emission spectrum in the near-infrared region as mentioned above, are advantageous as discharge lamps as light sources for conventional light beam soldering equipment. Many light beam soldering devices using arc lamps have been commercialized.

Although light beam soldering equipment using xenon short arc lamps has become relatively inexpensive, it takes longer to melt the solder than light beam soldering equipment using YAG lasers. The disadvantage was that it took a long time to process. In order to compensate for this drawback, there is a recent tendency to use lamps with large power consumption of about 1 to 5 KW, but using lamps with such high power consumption requires large-scale optical and cooling systems. However, there is a problem in that the device becomes quite large.

The present invention has been made in consideration of such problems,
The purpose of the present invention is to provide a light beam soldering device that is inexpensive, has a short processing time, and can be made more compact.

[Means for Solving the Problems] In order to achieve the above object, the light beam soldering device of the present invention includes a short-arc type metal vapor discharge lamp and a concentrator for condensing light from the metal vapor discharge lamp. It is equipped with an optical system including a light mirror, and means for positioning a workpiece covered with solder.

[Function] A metal vapor discharge lamp emits a large amount of light in the visible to ultraviolet range, and the temperature of the solder is efficiently raised by absorbing this light in the visible to ultraviolet range. Furthermore, since the distance between the poles of the metal vapor discharge lamp is short, the light is focused by the condenser mirror into an extremely small irradiation diameter, resulting in high energy density on the irradiated surface.

[Embodiment] FIG. 1 is an explanatory diagram showing a schematic configuration of a light beam soldering apparatus which is an embodiment of the present invention, and 4 is a metal vapor discharge lamp l;
A lamp house 5 housing the elliptical condensing mirror 2 and a plane mirror 3 is a lens barrel connected to the lamp house 4, and a lens 6, a plane mirror 7, and a lens 8 are housed in the lens barrel 5. In addition, the distance between the electrodes of the metal vapor discharge lamp l is preferably 5□ or less in order to reduce the irradiation diameter of the workpiece. 9 is a flat workpiece that is soldered by the light from this light beam soldering device. Shows a package IC, lO
1 is a solder for joining this flat package IC 9 and a printed circuit board 11, and 12 is a conveyor belt for conveying a workpiece.

In the apparatus shown in FIG. 1, light emitted from a metal vapor discharge lamp 1 is collected by an elliptical condenser mirror 2, reflected by a plane mirror 3, and then reflected by a lens 6.
The light that passes through the lens 6 is focused on the plane mirror 7.
It is reflected from the lens 8 and irradiated onto the solder lO of the workpiece.

In this example, an ultra-high pressure mercury lamp is used as the metal vapor discharge lamp l. ,,(B)
As a result of processing the solder material on the workpiece shown in Figure 1 using two conditions: output power 200 W and interelectrode distance 11111, the time required for the solder to melt is (
In case of a), 4 to 5 seconds, in case of (b), 2 to 3 seconds
It was c. Other examples of metal vapor discharge lamps include:
Also suitable are xenon mercury lamps and metal octane lamps in which metals such as iron are turned into pallite and sealed. In any case, a metal vapor discharge lamp that is a short arc type and emits a large amount of light in the ultraviolet region necessary for soldering may be used.

The main feature of this invention is that when solder is melted by light, the reflectance of light on the surface of the metal solder is a major factor.

Figure 2 shows the results of spectral reflectance measurements of melted and solidified cream solder, where the horizontal axis shows the wavelength of light [nm];
The vertical axis shows the reflectance [%] of the solder surface. The case with solid wire solder is almost the same.

As is clear from FIG. 2, the reflectance of the solder (metal) surface is high for light with wavelengths in the infrared region, and most of the light is reflected. On the contrary, since the reflectance of light in the ultraviolet region is low and the solder is well absorbed, it was decided in the present invention to irradiate the solder with light in this wavelength region. Therefore, as the light source, we chose an ultra-high pressure mercury lamp, which emits a large amount of light in the wavelength range where solder has low reflectivity.

This ultra-high pressure mercury lamp mainly uses 365 mm as shown in Figure 3.
, 405, 436, 546, and 578 nm, making it suitable for soldering.

FIG. 3 is a diagram showing the relationship between wavelength and intensity of a lamp, where the solid line is a 200W ultra-high pressure mercury lamp, and the dotted line is a 200W characteristic estimated from the characteristics of a 150W Canon lamp. On the other hand, lamps conventionally used for soldering mainly use light in the infrared wavelength range, where the solder surface has a high reflectance.For example, in the case of a xenon lamp, as shown in Figure 3, As is clear, the output is 200W (dotted line)
In the case of Mercury lamps are smaller overall;
In addition, since the wavelength range of the light used is a part of the solder with low surface reflectance, and because metal vapor discharge lamps such as ultra-high pressure mercury lamps strongly output light with wavelengths in this ultraviolet range, Compared to conventional optical soldering equipment, it is possible to perform highly efficient processing with a small light source.

[Effects of the Invention] As explained above, the light beam soldering device of the present invention performs soldering using a light source that strongly outputs light in a wavelength range where the surface reflectance of the solder is low, so compared to a conventional xenon lamp. As a result, a low-power light source can be used, the device can be made compact, and the solder can be melted efficiently.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the schematic configuration of a light beam soldering apparatus which is an embodiment of the present invention, FIG. 2 is a diagram showing the results of spectral reflectance measurement of cream solder, and FIG. 3 is a diagram showing the wavelength of the lamp. FIG. 3 is a diagram showing the relationship between strengths. In the figure. l: Metal vapor discharge lamp 2: Elliptical condenser mirror 3.7; Plane mirror 4: Lamp house 5: Lens barrel 6.8: Lens 10: Solder 11: Conveyor belt

Claims (1)

[Claims] A short-arc metal vapor discharge lamp with a strong emission spectrum in the ultraviolet region, such as an ultra-high pressure mercury lamp or a xenon mercury lamp, an optical system including a condensing mirror that collects the light from this metal vapor discharge lamp, and solder. 1. A light beam soldering apparatus comprising: means for positioning a stacked workpiece.