JP2787034B2 - heating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating furnace used for soldering using a heating source such as infrared rays.

[0002]

2. Description of the Related Art Conventionally, a device to be soldered using far-infrared rays (a target component) is heated as a whole to distribute heat to the entire target component and reflow, or The near-infrared ray emitted from the near-infrared heater (halogen lamp) is focused by a hyperboloid reflector for focusing.
There is a method in which a soldering position of a target component is locally heated at a focusing focal position and reflowed. In this case, heat is uniformly distributed throughout the target component and stabilized, so if there are soldering locations at multiple locations, all are reflowed uniformly, which is advantageous for improving quality. If low melting point substances such as resin are mixed in the parts,
There is a problem that a part which is weak to heat is melted by the whole heating. In addition, in the case of using near-infrared light, energy loss is small because local heating is performed, but when a metal having high heat conduction efficiency such as a hybrid lead frame is used as a target component, heat diffusion increases, High energy is required to obtain the predetermined heat required for reflow. In addition, when the absolute value of the energy is increased, there is a problem in that the variation in heat increases, and the quality also varies.

The applicant of the present invention has proposed a configuration in which, in addition to the local heating, the entire heating limited to the vicinity of the local heating is taken into consideration to reduce the energy loss and reduce the variation in heat. No. 3,2658 proposes disposing a reflector on the opposite side of the heat source of the target component.
As the reflector, a mirror-polished metal material such as a copper material or a glass substrate coated with gold is used.

[0004]

As described above, when a metal material is mirror-polished as a reflector, a lapping method of a high-purity metal plate is usually used. It will be very expensive. Also,
The use of copper as the metal material reduces the cost somewhat, but has a problem in terms of corrosion resistance. Further, a material coated with gold on a glass substrate is also expensive because gold is used as a material. Further, in the case of metallic materials, there is a problem that the surface is gradually oxidized by long-term infrared rays, and the reflection efficiency is reduced.

Accordingly, an object of the present invention is to provide a low-cost heating furnace which has a small energy loss, a small variation in heat, an excellent reflection efficiency, and a reduction in the reflection efficiency even after long-term use. To provide.

[0006]

To achieve the above object, a heating furnace according to the present invention comprises a heating source located on one side of a target component for heating a heating section of the target component, and a heating source for heating the heating section of the target component. And a reflector located on the side, the reflector being a glass substrate coated with copper and a low-refractive material coated thereon as a protective film. Is characterized in that the heat that has passed through is reflected by the reflector and reheats the vicinity of the heating part of the target component.

In the above-mentioned reflector, SiO 2 is preferably used as a protective film.

[0008]

The reflecting plate disposed at a position facing the heating source with the target component interposed therebetween reflects the heat passing through the target component again, irradiates the back surface of the target component and heats it to uniformly distribute the heat. I do.
The reflection plate has high reflection efficiency and can withstand long-term use.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. A near-infrared line heater such as a halogen lamp is used as the heating source 1 and is arranged at the focal point of a concave reflector 2 for condensing light (in this embodiment, a hyperboloid reflector). As the near infrared rays, those having a wavelength of 0.5 to 3.5 μm are used. The near-infrared ray L emitted from the halogen lamp 1 is focused at a predetermined focusing focus O. The soldering position on the target component 3 is set so as to coincide with the focal point O.
This causes local heating sufficient to reflow the solder.

The target component 3 is transported by a transport device 4 on a support 8 in a direction perpendicular to the paper surface. As an example of the transport device 4, an endless belt 5 that receives both ends of the target component 3 is driven to rotate by a rotating unit (not shown), and the target component 3 is moved by the rotation of the belt 5.
A magnet 6 is provided in a space surrounded by the belt 5, and when the target component 3 is made of a magnetic material, the target component 3 is attracted to the belt 5 by the magnetic attraction of the magnet 6. And hold that position.

A reflector 7 is disposed at a position facing the concave reflector 2 with the target part 3 interposed therebetween. The near-infrared ray L leaking from the focal point O and passing through the target part 3 is reflected by the reflector 7. The light is reflected again by the plate 7 and irradiates the back surface of the target component 3 to heat the entire vicinity of the focal point. This structure not only locally heats the focal point of the target component 3 to heat sufficient for reflow, but also
Since the vicinity thereof is also entirely heated by the reflected light, even in the case of a target component such as a metal having a large heat diffusion, the diffusion of the heat is supplemented by the heat due to the reflected light, and reflow without energy loss becomes possible.

Next, the reflection plate 7 will be described in detail. First, in order to reduce the cost of the reflection plate, it is desirable to employ a configuration in which wrapping, which is a factor that increases the cost, is not required. For this reason, a configuration is employed in which metal is deposited on a glass substrate. This is because the glass surface is sufficiently smooth, and if a metal is deposited thereon, a sufficiently smooth metal surface can be obtained without the need for a lapping operation. In addition, since the deposited metal surface needs to have excellent reflection efficiency, aluminum, silver, gold, copper, and rhodium are deposited on a glass substrate to determine the metal. Wavelength 850nm, 5000nm, 10000nm on the surface
Were irradiated with infrared rays, their reflectances were examined, and their corrosion resistance and cost were evaluated. Table 1 shows the results.

[0013]

[Table 1]

As shown in Table 1, copper is the most excellent metal to be deposited when the reflectance, corrosion resistance and cost are comprehensively evaluated as an infrared reflector. Therefore, in order to improve the corrosion resistance, which is slightly inferior to copper, a low refractive material is provided as a protective film on copper.

Embodiment 1 FIG. 2 is a partially enlarged cross-sectional view showing an embodiment of the reflection plate 7, and a chromium film having a thickness of 0.02 μm is formed on a surface of a glass substrate 7a as a bonding layer 7b by a sputtering method. Then, a copper layer having a thickness of 0.25 μm is continuously coated thereon as a reflective layer 7c in the same manner, and a low-refractive material is formed on the copper layer as a protective film 7d by applying SiO2 having a thickness of 1.0 μm. Coating in a similar manner.

Depending on the thickness of the protective film 7d, interference of reflected light in the visible light range occurs. Therefore, observation was performed while changing the thickness variously. As a result, no interference color appears up to a film thickness of 0.1 μm, but at a film thickness of 0.15 μm, an interference peak appears at 420 nm, and as a result, purple is confirmed as an interference color,
Not preferred. At a film thickness of 0.3 μm, an interference peak appears at 440 nm, and as a result, purple is confirmed as an interference color. When the film thickness is 0.6 μm, interference peaks appear at 410 nm and 510 nm, and as a result, the interference color becomes lighter, but it is confirmed as uneven color.

FIGS. 3A and 3B show a protective film 7d having a film thickness of 1.degree.
The wavelength-reflectance characteristics at 0 μm and 1.5 μm are shown. When the film thickness is reached, the peak of interference gradually becomes small, and as a result, no interference color is confirmed.

Further, in order to examine the relationship between the film thickness of the protective film 7d and the corrosion rate, the film thickness was set to 0.1 μm, 0.15 μm,
A plurality of reflectors having a thickness of 0.3 μm, 0.45 μm, and 1.5 μm were formed, and each was subjected to a corrosion test in which each was immersed in a ferric chloride etching solution for 5 minutes. The result is shown by a solid line in FIG. The corrosion rate is the ratio of the corrosion area in the present invention when the corrosion area without the protective film 7d is 100. That is, the film thickness is 0.1 μm
Corrosion rate 23.5%, 0.15 μm corrosion rate 6.5
%, The corrosion rate is 1.8% at 0.3 μm, the corrosion rate is 0.9% at 0.45 μm, and the corrosion rate is 0.1% at 1.5 μm. 1.0 μm
Shows about 200 times the corrosion resistance.

Therefore, it is desirable that the film thickness is 1.0 μm or more as a film having no interference color and having good corrosion resistance. However, it was found that when the film thickness was 5.0 μm or more, the internal stress of the protective film 7d became stronger than the bonding strength of the bonding layer 7b, and the peeling between the copper 7c and the glass substrate 7a was likely to occur. From this, the film thickness is 1.
0 μm to 5.0 μm is desirable. The reflectance in the infrared region is hardly affected by the thickness of the protective film 7d of SiO2.

Example 2 In Example 1, each of the reflectors on which protective films 7d having various thicknesses similar to those used in the corrosion test were formed was subjected to a heat treatment at 300 ° C. for 1 hour. As a result, as shown by a dotted line in FIG.
At 5 μm, the corrosion rate is 0.6%, and at 0.3 μm, the corrosion rate is 0.3%.
At 3% and 0.45 μm or more, the corrosion rate was 0.1%.
That is, the heat treatment significantly improved the corrosion resistance by about 10 times. However, if the heating temperature exceeds 400 ° C., the Cr of the bonding layer 7b between the copper 7c and the glass substrate 7a
Was diffused into the copper 7c, the adhesion to the glass substrate 7a was rapidly reduced, and the reflectance was also lowered because Cr was diffused into the copper 7c. From this, the heating temperature is 25
0 ° C to 400 ° C is suitable.

As another example, any one of Ni, Ni-Cr, Si and the like can be used as the bonding layer 7b instead of Cr.

By adjusting the material of the reflection plate 7, the distance between the target component 3 and the reflection plate 7, the reflection efficiency, and the like, a free heat distribution can be easily formed.

[0023]

According to the heating furnace of the present invention having the above-described structure,
Since the reflection plate is provided, the heat passing through the target component is reflected again by the reflection plate, and the back surface of the target component can be irradiated to heat the vicinity of the heating portion again. Therefore, not only can the target part be sufficiently heated locally, but also its surroundings can be fully heated by the reflected heat, and even in the case of a target part such as a metal with a large heat diffusion, the heat diffusion must compensate for the heat diffusion. Energy loss can be reduced. In addition, since the entire heating is limited to the vicinity of the heating section, there is no problem such that the heat-sensitive portion is melted. Further, since the reflection plate is formed by coating copper on the glass substrate, lapping work is not required, the reflection plate can be manufactured at low cost, and the reflection efficiency is excellent. Also, since a low refractive material is coated as a protective film on copper,
Excellent corrosion resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of a reflection plate.

FIG. 3 is a wavelength-reflectance characteristic diagram.

FIG. 4 is a relationship diagram between the thickness of a protective film and the corrosion rate of copper.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heat source 3 Target part 7 Reflector 7a Glass substrate 7c Copper 7d Protective film

Claims (2)

(57) [Claims] 1. A heating source located on one side of a target component for heating a heating section of the target component, and a reflector located on the other side of the target component, wherein the reflector is made of glass A substrate is coated with copper, and a low-refractive material is coated thereon as a protective film. The heat that has passed near the heating part of the target component is reflected by the reflector and is again reflected in the target component. A heating furnace for heating the vicinity of the heating section. 2. A heating furnace according to claim 1, wherein said reflection plate uses SiO2 as a protective film.