JP3191415B2 - Chisso reflow device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen reflow apparatus, and more particularly, to a nitrogen reflow apparatus capable of preventing a chip mounted on a lower surface of a double-sided mounting substrate from being reheated and damaged by heat.

[0002]

2. Description of the Related Art After a chip is mounted on a substrate by a chip mounter or the like, the substrate is sent to a heating chamber of a reflow device.
The electrodes of the chip are soldered to the electrodes of the substrate by heating and melting the solder and then cooling and solidifying the solder.

[0003] Reflow devices are roughly classified into an air reflow device that heats air in a heating chamber with a heater and a nitrogen reflow device that sends nitrogen gas to the heating chamber and heats the nitrogen gas with the heater. The air reflow device has an advantage of a simple structure and low cost, but has a disadvantage that a metal part such as a circuit pattern formed on a substrate is easily oxidized. In contrast, the Chisso reflow device heats the substrate in an inert gas atmosphere, which has the advantage that circuit patterns and the like are not easily oxidized.However, the cost, including running costs, is quite high, so it is not yet widely used. It is in. However, in recent years, high quality substrates have been increasingly required, and therefore, Chisso reflow apparatuses have been attracting attention.

[0004]

By the way, in order to achieve high integration of a substrate, a double-sided mounting substrate in which chips are mounted on both upper and lower surfaces of the substrate is often used. On a double-sided mounting board,
First, the chip is mounted on one side of the substrate and sent to the reflow device, the solder is heated and the chip is soldered, then the substrate is turned upside down, the chip is mounted on the other surface, and sent to the reflow device again. Then, the solder is heated and the chip is soldered. Therefore, the chip previously mounted on one surface of the substrate and the solder for soldering the chip are heated twice by the reflow device.

However, since the chip has low heat resistance, it is susceptible to thermal damage by being heated twice, and during the second reflow, the solder that has been soldered to the lower surface of the substrate is reheated and re-melted. However, there is a problem that the chip easily falls from the substrate. Therefore, in the conventional air reflow device, external air is introduced into the heating chamber, and low-temperature air is blown on the lower surface of the substrate conveyed to the conveyor, thereby preventing the chips and solder on the lower surface from being excessively heated. Had avoided. However, in a nitrogen reflow apparatus, when external air is introduced into the heating chamber, the nitrogen gas concentration is significantly reduced, and thus such means cannot be adopted due to its characteristics.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a nitrogen reflow apparatus capable of preventing a chip on the lower surface of a substrate from being thermally damaged or remelting solder during a second heating.

[0007]

SUMMARY OF THE INVENTION The present invention To this end, disposed within the heating chamber arranged to heat exchange pipe below the conveyor for conveying the double-sided mounting board, and a heat exchange < A refrigerant distribution means for distributing a refrigerant through a pipe is provided.

[0008]

According to the above construction, by circulating the refrigerant through the heat exchange pipe, the lower space of the conveyor is kept at a low temperature, and the chip on the lower surface of the substrate is prevented from being thermally damaged and the solder is re-melted. it can.

[0009]

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

FIG. 1 is a side view showing the inside of a nitrogen reflow apparatus. Inside the heating chamber 1, there is provided a conveyor 4 for transporting a substrate 10 on which chips 9 are mounted from the inlet 2 to the outlet 3. Above the conveyor 4, a heater 5 and a fan 6 are provided. . Reference numeral 8 denotes a driving motor for the conveyor 4, and reference numeral 7 denotes a driving motor for the fan 6. The interior of the heating chamber 1 is divided by a partition wall 15 into a preheating zone T1 on the inlet 2 side, a soaking zone T2 in the central part, and a reflow zone T3 on the outlet 3 side, and each zone T1, T2, T3 has:
A pipe 12 from a nitrogen gas supply unit 11 such as a liquid nitrogen cylinder storing liquid nitrogen or a nitrogen gas generator for separating nitrogen and oxygen in the air to generate nitrogen gas.
The nitrogen gas is supplied through. 13 is a valve. A shutter 35 is provided at the entrance 2 and the exit 3. The shutter 35 is connected to a rod of a cylinder 36.
Moves up and down to open and close inlet 2 and outlet 3. Normally, the shutter 35 closes the inlet 2 and the outlet 3 so that the nitrogen gas in the heating chamber 1 does not flow outside, and opens the inlet 2 and the outlet 3 when the substrate 10 enters and exits.

In FIG. 1, a lower part of a heating chamber 1 is a partition wall 2.
In the lower space divided by the partition wall 21, a heat exchange pipe 22 as cooling means is disposed in a direction crossing the heating chamber 1.
A plate 23 as shutter means is provided between the conveyor 4 and the pipe 22, and dampers 24 as opening and closing means are provided on both sides of the plate 23.
As shown in FIG. 4, the damper 24 is mounted on a pin 25, and rotates around the pin 25 to open and close. Damper 24
May be manually opened or closed, or may be opened and closed by a power means such as a motor, a cylinder, or a solenoid.

As shown in FIGS. 2 and 3, both sides of the pipe 22 are provided with hoods 26 (26) provided on the wall surface of the heating chamber 1.
A, 26B). One hood 26A is connected to a blower 27 having a built-in fan as an air supply means, and the other hood 26B is connected to an exhaust duct 28. Therefore, when the blower 27 is driven,
The outside air flows through the inside of the pipe 22 and is discharged from the duct 28 (see a broken line arrow). Of course, the refrigerant may be other than air.

In FIG. 1, a fan case 29 is provided at a lower portion of the heating chamber 1, and a sirocco fan 30 is provided therein. As shown in FIG. 3, the fan 30 is driven and rotated by a motor 31 provided on a side wall of the heating chamber 1. When the fan 30 rotates, the nitrogen gas in the lower space of the conveyor 4 circulates in the arrow N direction. FIG.
In the figure, 19 is a heat insulating material provided at the boundary between the upper part and the lower part of the heating chamber 1. The heat insulating material 19 prevents the heat of the upper part of the heating chamber 1 heated by the heater 5 from being transmitted to the lower part. Reference numeral 14 denotes solder for bonding the chip 9 to the substrate 10.

This Chisso reflow apparatus has the above-described configuration, and the operation will be described next. In FIG. 1, a substrate 10 on which a chip 9 is mounted is transported rightward by a conveyor 4. Meanwhile, nitrogen gas heated by the heater 5 is blown onto the substrate 10 by the fan 6,
The substrate 10 is heated. Generally, in the preheating zone T1, the substrate 10 is heated from room temperature to about 150 ° C.
Next, it is heated to about 170 ° C. in the soaking zone T2, and then heated to 220 ° C. or more in the reflow zone T3. The melting temperature of the solder 14 is about 183 ° C., and when the substrate 10 is heated to 220 ° C. or higher, the solder 14 is melted. Next, the substrate 10 is carried out of the heating chamber 1 and cooled, the solder 14 is solidified, and the electrodes of the chip 9 are soldered to the electrodes of the substrate 10.

Next, the substrate 10 is turned upside down, and the chip 9 is mounted on the other surface, sent to the heating chamber 1 again, and subjected to the same heat treatment as described above. In this case, as shown in FIG. 2, the chip 9 previously soldered is
Is glued. When the chip 9 and the solder 14 are reheated, the chip 9 is thermally damaged as described above,
Alternatively, the solder 14 is re-melted and the chip 9 easily falls off the substrate 10. So, during this second reflow,
By driving the blower 27, external normal-temperature air is passed through the heat exchange pipe 22 so that the temperature of the lower space of the heating chamber 1 does not excessively increase. At this time, the damper 24 is opened as shown by the solid line in FIG. By the way, the temperature of the preheating zone T1 is reduced to about 100 ° C., the temperature of the soaking zone T2 is reduced to about 110 ° C., and the temperature of the reflow zone T3 is reduced to about 160 ° C. due to the heat exchange action of the pipe 22. Can be prevented from remelting.

In the case of single-sided mounting, the upper and lower portions of the heating chamber 1 are shut off by stopping the driving of the lower surface cooling block 27, the fan 30 and the like and closing the damper 24, thereby increasing the thermal efficiency of the heating chamber 1. . During double-sided mounting, the damper 24 opens and cools the lower surface of the substrate 10.

FIGS. 5 and 6 show another embodiment of the present invention. As shown in FIG. 5, a blowing nozzle 41 and a suction nozzle 42 are provided on the inner wall of the heating chamber 1 immediately below the conveyor 4. The blowing nozzle 41 is connected to a nitrogen gas supply unit 44 via a tube 43, and the suction nozzle 42 is connected to a nitrogen gas supply unit 4 via a tube 45.
4 is connected. The nitrogen gas supply unit 44 separates nitrogen and oxygen in the air to generate nitrogen gas and sends it to the heating chamber 1. Therefore, the nitrogen gas sent from the nitrogen gas supply unit 44 is blown out from the blow-out nozzle 41 and is sucked into the suction nozzle 42 (see the broken line arrow N), and the upper space and the lower space of the heating chamber 1 are shut off by the flow of the nitrogen gas. That is, this constitutes an air shutter means using nitrogen gas instead of the plate 23. Other configurations such as the pipe 22 and the fan 30 are the same as those of the first embodiment, and the same operation and effects as those of the first embodiment can be obtained. The nitrogen gas supply unit 11 for supplying nitrogen gas to the heating chamber 1 may also be used as the nitrogen gas supply unit of the air shutter means.

[0018]

As described above, according to the present invention, the lower space of the conveyor is maintained at a low temperature, the chip on the lower surface of the double-sided mounting board which has been soldered earlier is thermally damaged, Remelting can be avoided. Again
The invention according to claim 2 opens and closes between the conveyor and the heat exchange pipe.
Shutter means is provided for
Open the shutter means if it is a single-sided mounting board.
Closing the shutter means, etc.
Reflow processing can be performed according to the mounting substrate. Also
In the invention of claim 3, the nitrogen gas in the lower space of the conveyor is used.
Since a fan for circulation is provided, the heat exchange pipe
Increase the heat exchange efficiency and increase the temperature in the lower space of the conveyor.
It can be more effectively deterred.

[Brief description of the drawings]

FIG. 1 is a side view of a nitrogen reflow device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a nitrogen reflow device according to one embodiment of the present invention.

FIG. 3 is a partial plan view of a nitrogen reflow device according to one embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a nitrogen reflow device according to one embodiment of the present invention.

FIG. 5 is a sectional view of a nitrogen reflow apparatus according to another embodiment of the present invention.

FIG. 6 is a partial side view of a nitrogen reflow device according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating chamber 4 Conveyor 5 Heater 11 Nitrogen gas supply part 22 Heat exchange pipe 23 Shutter means 27 Air supply means (blower) 41 Shutter means 42 Shutter means

Claims (3)

(57) [Claims] 1. A heating chamber, a conveyor for transporting a double-sided mounting substrate in the heating chamber, a heater disposed above the conveyor, a nitrogen gas supply unit for supplying nitrogen gas to the heating chamber, A heat exchange pipe disposed below and a refrigerant for flowing a refrigerant through the heat exchange pipe
A chisso reflow device characterized by comprising a distribution means. 2. A space between the conveyor and the heat exchange pipe.
Claims wherein shutter means for opening and closing are provided.
Item 6. The nitrogen reflow device according to Item 1. 3. A system for circulating nitrogen gas in a space below the conveyor.
2. The method according to claim 1, further comprising the step of:
Is the Chisso reflow apparatus described in 2.