JPH0335876A - Reflowing device - Google Patents

Abstract

PURPOSE:To reduce variance of the temperature in a substrate and to improve soldering efficiency by providing a heating element capable of controlling the radiant surface temperature arbitrarily in a heating chamber. CONSTITUTION:The substrate 4 mounted with chip parts on which solder for reflow is applied is placed on an endless conveyor 3 and made to travel in the direction shown by the arrow A and carried in the tunnellike heating chamber 2. At this time, radiant heating by an infrared heater 5 is allowed to correspond to packaging density of the parts mounted on the substrate and radiant heat of the heating element is controlled and the solder for reflow is heated above the eutectic temperature and molten and reflow soldering is performed. The radiant surface temperature of the heating element is detected by a temperature detector and based on a signal from the temperature detector, a control part controls it. By this method, preheating of material to be heated and heating of the solder for reflow are speeded up and the temperature difference caused by the size and quantity in number (density) of the material to be heated is reduced and efficiency of heating and reflow soldering is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a reflow apparatus for soldering various electrical and electronic components to a printed circuit board or the like (hereinafter referred to as a board).

2. Description of the Related Art In recent years, as electronic and electrical devices have become smaller, the substrates on which various components used in these devices are mounted have also become smaller and more dense. In manufacturing such a mounting board, desired components are soldered onto the board using a reflow device.

In a conventional reflow apparatus, cream solder for reflow is applied onto a board, and after each component is mounted, the solder is continuously heated and reflowed.

The heating method of such reflow equipment includes atmospheric heating.

Hot air heating, infrared radiation heating 0M air submarine #! :″f!: There is heating etc. that were used.

Among these heating methods, atmospheric 770 heat has the advantage that an inert gas can be used as a measure to prevent oxidation of the substrate, but has the disadvantage that the heating rate of the components and substrate, which are 1xi heated substances, is slow. There is. Although hot air heating can increase the temperature of the object to be heated faster than the above-mentioned atmospheric heating, it has the disadvantage of poor heating uniformity and poor heat transfer. Another drawback is that when the wind speed is increased to increase heating efficiency, the position of components on the board may shift. Next, infrared radiant heating has the advantage of high radiation efficiency and easy temperature control, but there are differences in infrared absorption rate depending on the type of object to be heated, so the temperature increase rate changes depending on the object to be heated. Each has the disadvantage of causing temperature variations. Next, heating using steam latent heat,
By boiling a fluorine-based organic solvent and performing soldering with its saturated steam, uniform heating characteristics can be obtained, but there are problems in terms of running costs and working environment. It has not yet become widespread.

Therefore, in recent years, as an improvement to the above-mentioned auxiliary method, attention has been paid to a reflow apparatus that uses a heating method that uses a combination of radiation and convection, in which the object to be heated is heated by infrared radiation and hot air. For example, there is a reflow apparatus that uses a combination of hot air heating from above over the entire heating section of the reflow apparatus and local infrared radiation heating. An example of this is shown in FIG.

Referring to FIG. 4, 11 and 12 are heaters for heating the atmosphere in the heating chamber of the reflow apparatus, and 13 is a fan that creates wind 9 that blows the heated atmosphere downward, thereby causing the heated atmosphere to flow onto the conveyor 3. heating the heated object 4,
Further, the infrared heaters 16 and 17 are used to supplementally heat the beams, thereby achieving a circular alignment.

Furthermore, as another example, there is a reflow apparatus using a forced circulation heating method of hot air from above and below over the entire heating section of the reflow apparatus. An example of this is shown in FIG.

The button 18 in FIG. 6 is a blower, which forcibly circulates air at a considerable wind speed, and the circulating air is energized by a heater 19 to substrates of objects to be heated that are conveyed on the conveyor 3. The soldering process involves spraying hot air onto the board to preheat it, and then using the same method to circulate and heat the board.

Problems to be Solved by the Invention However, in the conventional reflow apparatus shown in FIG. 4, compared to a simple radiant heating type reflow apparatus, heating is relatively uniform, and there is little variation in temperature within the same substrate. However, if the heat capacity of the object to be heated is extremely large and there is a significant difference in the density of each component mounted on the board, the temperature will vary within the same board and the difference will occur. growing. As a result, there are areas where the solder is insufficiently melted, which also causes defective products.

In addition, in the conventional reflow apparatus shown in Fig. 5, heating is performed by forcibly blowing hot air, which requires preheating of the object to be heated, an increase in the degree of reflow soldering, and the size and number of objects to be heated. Although it is possible to reduce the temperature difference caused by the degree of density (or density), since hot air is forcibly blown onto the heated object, the chip components on the board may become misaligned, which may also lead to defective products. was the cause of the outbreak.

Therefore, an object of the present invention is to achieve relatively uniform heating with little temperature variation within the board, unaffected by the size of the object to be heated, the type of parts placed on it, and the mounting density on the board. It is an object of the present invention to provide a reflow device that can be used in a variety of ways, and that also causes less misalignment of parts.

Means for Solving the Problems In order to solve the above-mentioned problems, the reflow apparatus of the present invention is provided with a plurality of heating elements in the heating chamber and means for controlling the temperature of the radiation surface of the heating elements. It is.

Function The present invention applies the reflow solder while continuously conveying the board coated with reflow solder and on which components are mounted by a conveyor into a tunnel-shaped heating chamber equipped with a plurality of heating elements that can arbitrarily control the temperature. After melting, the component is soldered to the board by cooling and solidifying. In particular, in the reflow apparatus of the present invention, the object to be heated, that is, the component mounting board on the conveyor can be heated by the radiant heat from the plurality of heating elements. As a result, the temperature raising efficiency and uniform heating characteristics of the object to be heated are improved, regardless of how close or dense the parts are placed.
Temperature variations within the same board are reduced, and reflow soldering can improve quality and stability.

EXAMPLE An example of the reflow apparatus of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of an embodiment of the reflow apparatus of the present invention, 2 is a tunnel-shaped heating chamber of the reflow apparatus 1, and 3 is an endless conveyor, which is used to apply reflow solder. , the substrate 4 on which the chip components are mounted is transported into the heating chamber. Reference numeral 6 denotes an infrared heater that heats the chip component mounting board 4 with far infrared rays, which heats the conveyor 3 passing through the heating chamber 2 downward and upward from above and below, respectively, and also heats the atmosphere within the heating chamber 2. A cooling fan 6 cools and solidifies the molten reflow solder. Inside 7 is a thermal insulator provided around the heating chamber 2, and is provided to prevent a rise in temperature outside the heating chamber 2.

The operation of the reflow apparatus configured as described above will be described below. First, the chip component mounting board 4 coated with reflow solder is placed on the endless conveyor 3.
It is made to travel in the direction shown by the arrow mark and is carried into the tunnel-shaped heating chamber 2. At this time, the radiant heat from the infrared heater 6, which is a heat source, heats the chip component mounting board 4 placed on the heat conveyor a and being transported, heats and melts the reflow solder on the board, and 2, it is cooled and solidified, and the chip components are mounted on the board.

The heating temperature of the radiant heat from the infrared heater 6 according to the above embodiment is controlled by the controller μ section 1o in accordance with the mounting density of the components placed on the board, and the temperature is increased when the chip component mounting board 4 is heated. A specific example of the state in which the speed increases and the temperature inside the substrate becomes uniform will be shown below.

A single 3KW infrared heater 6 consisting of a 30W heating element 8 whose radiation surface temperature can be controlled arbitrarily is installed in the heating chamber 2.
Install 6 pieces each on the top and bottom surfaces with Tranbear 3 in between,
A chip component mounting board 4 coated with Sn/Pb (e a/37) eutectic reflow solder is placed on a conveyor 3 in a reflow apparatus 1 equipped with a heating chamber 2 with a length of 2 m.
It was placed on the conveyor and run at a conveyor conveyance speed of 1.0ry15+. Then, the radiation heating by the infrared heater 6 is controlled according to the mounting density of the components placed on the board, and the radiation heat of the heating element 8 is controlled to heat the reflow solder to a temperature higher than the eutectic temperature, melt it, and reflow the solder. I did some soldering. inside,
The temperature of the radiation surface of the heating element 8 is detected by a temperature detector 9,
Based on the signal from this temperature sensor 9, it is controlled by a control section.

FIG. 3 shows the temperature profile of the chip components and the substrate surface when reflow soldering is performed as described above. An aluminum electrolytic capacitor was used as the chip component, and the electrode part was soldered to the board.

In FIG. 3, P indicates the substrate surface temperature in a portion where the packaging density is sparse, and q represents the temperature of the aluminum electrolytic capacitor electrode portion in a portion where the packaging density is dense. There is almost no temperature difference between the two.

On the other hand, in the conventional reflow apparatus shown in FIGS. 4 and 6, the temperature difference between the substrate surface and the aluminum electrolytic capacitor electrodes mounted at high density is 30 to 60 degrees.
℃, making reflow soldering insufficient or impossible.

Effects of the Invention In the reflow apparatus of the present invention, a heating element that can arbitrarily control the temperature of the radiant surface is installed in the heating chamber, so that radiation heating of the heating element and convection of the atmosphere in the heating chamber can cause
Preheating of objects to be heated, increasing the heating speed of solder for reflow,
Size of heated object.

It is possible to reduce the temperature difference caused by the number (or density), and it is possible to improve the efficiency of heated reflow soldering.

[Brief explanation of drawings]

Fig. 1 is a schematic cross-sectional view of one embodiment of the reflow apparatus of the present invention, Fig. 2 is an explanatory diagram showing an embodiment of an infrared heater, and Fig. 3
This figure shows a temperature profile in the embodiment of FIG. 1, and FIGS. 4 and 6 are schematic cross-sectional views of a conventional reflow apparatus. 1., , reflow device, 2..--heating chamber,
3... Transfer conveyor, 4... Chip component mounting board, 6... Infrared heater, 6...
-Cooling fan % 7--thermal insulator, 8--heating element, 9--temperature detector, 10--control section. r-1-rif〇-device 2-711 m 1f 3- lead 4- + wap button product loading W 5- infrared anti-heater 6- iδ fan 7-- F disconnected body No. Figure Figure Time (Collar) Figure Δ Figure Figure

Claims (1)

[Claims] a conveyor section that transfers a board on which reflow solder is applied and electronic components are placed; a heating section that is provided between the conveyor section and heats and melts the reflow solder of the board;
In the reflow apparatus, the heating section includes a cooling section that is located behind the heating section and cools and solidifies the molten solder for reflow, and the heating section is composed of a plurality of heating elements whose temperature can be controlled arbitrarily, and the heating section is composed of a plurality of heating elements that can be arbitrarily controlled in temperature. Attach a temperature sensor to
A reflow apparatus comprising means for controlling the temperature of the radiation surface of the heating element using the temperature detector.