JPH07212029A - Chisso reflow device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a chisso reflow device capable of quick start-up and highly accurate adjustment of the nitrogen gas concentration in the furnace body. [Constitution] A furnace body 1, a conveyor 2 for carrying a substrate 4 from an inlet 1c to an outlet 1d of the furnace body 1, and a conveyor 2 arranged in the furnace body 1 and carried along a predetermined temperature profile to the conveyor 2. Heaters H1, H2, H for heating the substrate 4
3, H4, and a concentration sensor S4 for detecting the concentration in the furnace body 1, and a predetermined conduit for discharging the rising flow rate in the furnace body 1 at the time of start-up or a specified flow rate of less than this rising flow rate of nitrogen gas. The flow rate of L1 and the adjustment pipeline L2 for discharging the nitrogen gas at a variable flow rate into the furnace body 1 and the regulation pipeline L1 are switched, and the output of the concentration sensor S4 is input to control the flow rate of the adjustment pipeline L2. It has a control circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitrogen reflow device which can accurately adjust the nitrogen gas concentration in a furnace.

[0002]

2. Description of the Related Art A chip reflow device is used to solder an electronic component surface-mounted on a substrate and a circuit pattern on the substrate and to prevent oxidation due to heating in a furnace. In such a nitrogen reflow apparatus, it is necessary to maintain the nitrogen gas concentration in the furnace body (particularly at a high temperature portion) at a predetermined concentration. Since oxygen-containing air exists outside the Chisso reflow equipment, a large amount of Chisso gas can be sent to the furnace body from the Chisso gas supply unit such as a Chisso cylinder when the Chisso reflow equipment is started up, so that the concentration of Nitrogen is as short as possible. In order to reach a predetermined concentration and then maintain the predetermined concentration, it is necessary to supply nitrogen into the furnace while controlling the flow rate.

However, in the conventional chisso reflow device,
A single conduit that can change the flow rate is connected to the inside of the furnace, and this single conduit supplies a large amount of nitrogen gas to the furnace when the Chisso reflow equipment is started up, and the flow rate for maintaining a predetermined concentration is maintained. I was making adjustments.

[0004]

However, in such a structure, the range of flow rate to be controlled by a single conduit is
It will be in a wide range from zero to more than a large amount of flow at startup. Therefore, there is a problem that the flow rate adjustment is rough and the control accuracy is not sufficient.

Therefore, an object of the present invention is to provide a chisso reflow apparatus which can supply a large amount of nitrogen gas into the furnace body at the time of start-up and can adjust the concentration with high accuracy.

[0006]

A chisso reflow apparatus according to the present invention comprises a furnace body, a conveyor for carrying a substrate from an inlet to an outlet of the furnace body, a conveyor arranged in the furnace body, and having a predetermined temperature profile. Concentration sensor that detects the concentration inside the furnace, and a conduit that discharges nitrogen gas at a specified flow rate at startup or below this startup flow rate, with a heater that heats the substrate conveyed to the conveyor And a control circuit for controlling the flow rate of the adjusting pipeline by inputting the output of the concentration sensor while switching the flow rate of the regulating pipeline for discharging a variable flow of nitrogen gas into the furnace body and the regulated pipeline.

[0007]

With the above structure, the control circuit opens the specified pipe line at the time of start-up, and the rising flow rate or more of nitrogen gas is supplied into the furnace body from the specified pipe line to increase the concentration of nitrogen gas in the furnace body. To do. When the sensor detects that the nitrogen gas in the furnace has reached a predetermined concentration (or the oxygen in the furnace has dropped below a predetermined value), the control circuit sets the flow rate in the specified pipeline to the specified flow rate, and outputs the sensor output. While inputting, the flow rate of the adjusting pipeline is controlled so that the inside of the furnace body has a predetermined flow rate. Here, since the constant specified flow rate discharged from the specified conduit is superimposed on the flow rate discharged from the adjusted conduit, the range of the flow rate to be controlled by the adjusted conduit is made much smaller than that of the conventional means. Therefore, it is possible to easily improve the accuracy of control relating to the nitrogen gas concentration in the furnace body.

[0008]

【Example】

(Embodiment 1) Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view of a chisso reflow device according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a furnace body. By providing partition walls 1a and 1b in the furnace body 1, a preheating zone T1 for raising the upper surface of the substrate 4 from room temperature to about 150 ° C., and a uniform heating zone for maintaining this temperature are provided. Thermal zone T2,
Reflow zone T to further raise the temperature to about 220 ° C
It is divided into three. Further, 1c is an inlet of the furnace body 1, 1d is an outlet, and 2 is from the inlet 1c to the outlet 1d.
A conveyer 2a for conveying the substrate 4 from left to right is a support plate of the conveyer 2, and 3 is a drive motor of the conveyer 2.
Further, H1 is a heater for the preheating zone T1, F1 is a fan for the preheating zone T1, M1 is a motor for rotating the fan F1, and S1 is a temperature sensor for detecting the ambient temperature of the preheating zone T1. Is the heater H2,
A fan F2, a motor M2, and a temperature sensor S2 are provided,
The reflow zone T3 has heaters H3, H4 and a fan F.
3, a motor M3, and a temperature sensor S3 are provided. Further, P is an electronic component mounted on the substrate 4, and S4 is a concentration sensor that indirectly detects the concentration of nitrogen gas by detecting the concentration of oxygen in the reflow zone T3 where the temperature is highest.

L1 is a reflow zone T3 of the furnace body 1.
Is a regulated pipeline that discharges the maximum flow rate at startup or a regulated flow rate below this maximum flow rate, L2 is a regulation pipeline that discharges a variable flow rate of nitrogen gas to the reflow zone T3, and 10 is a nitrogen gas supply such as a nitrogen gas cylinder. It is a department. In the first embodiment, the specified pipeline L1 is the first pipeline a and the second pipeline
It is formed by connecting the pipe line b in parallel. In the first pipeline a, 1
Reference numeral 1 is a pressure regulator having a discharge pressure of 3 kg / cm ² and a flow rate of 350 l / min, and V1 is a first opening / closing valve such as a solenoid valve, which are connected in series along the discharge direction indicated by the arrow. Similarly for the second pipeline b, the discharge pressure is 2 kg / cm ² ,
A pressure regulator having a flow rate of 80 l / min and a second opening / closing valve V2 are connected in series. The adjusting line L2 is composed of a third line c and has a discharge pressure of 3 kg / cm ² and a flow rate of 200 l / m.
An in pressure regulator 13, a third on-off valve V3, and a control valve V4 are connected in series.

FIG. 2 is a block diagram of a chisso reflow apparatus according to the first embodiment of the present invention, in which 14 is a control circuit including a CPU and the like, and the control circuit 14 is a prescribed pipeline L1.
The flow rate is switched and the output of the concentration sensor S4 is input to control the flow rate of the adjustment conduit L2. Reference numeral 15 is a temperature detection circuit that converts the outputs of the temperature sensors S1, S2, S3 into a data format that the control circuit 14 can recognize, and 16 is an oxygen concentration detection circuit that converts the output of the concentration sensor S4 into a data format that the control circuit 14 can recognize. Is. In this embodiment, the control circuit 14 has a post-startup oxygen concentration of 2000 p
When it reaches pm, it is determined that the nitrogen gas concentration in the reflow zone T3 has reached a predetermined concentration.

Reference numeral 17 denotes a first opening / closing valve V1, a second opening / closing valve V2, and a third opening / closing valve V3 in response to a command from the control circuit 14.
An open / close valve drive circuit for opening and closing the control valve 18, a control valve drive circuit 18 for adjusting the opening of the control valve V4 in accordance with a command from the control circuit 14 and varying the flow rate of the adjusting pipe L2.
The heaters H1, H2, H3, and H4 generate currents such that the control circuit 14 sets the preheating zone T1, the soaking zone T2, and the reflow zone T3 to the ambient temperature according to a predetermined temperature profile in accordance with the output of the temperature detection circuit 15. It is a heater drive circuit for supplying to.

The chisso reflow apparatus according to the first embodiment has the above-mentioned structure, and its operation will be described with reference to FIG. FIG. 3 is a graph showing changes over time in the flow rate in each of the first pipeline a, the second pipeline b, and the third pipeline c of the chisso reflow device in the first embodiment. First, start-up is started at time Ta. At this time, the control circuit 14 instructs the on-off valve drive circuit 17 and the control valve drive circuit 18 to control the first, second, and third on-off valves V
1, V2, V3 and control valve V4 are commanded to be fully opened, and as a result, 350 l / min in the first pipeline a,
80 l / min in the second pipeline b (ie 43 in the regulated pipeline L1
0 l / min (rising flow rate), 3rd pipeline c (adjustment pipeline L)
In 2), a large amount of nitrogen gas of 200 l / min, a total of 630 l / min, is discharged into the reflow zone T3, and the oxygen concentration detected by the concentration sensor S4 rapidly decreases.

At time Tb, the density sensor S4 has a predetermined value (2
000 ppm) is detected, the control circuit 14 completes the start-up and shifts to the state of adjusting the concentration. That is, the opening / closing valve drive circuit 17 is instructed to close the first opening / closing valve V1, and the control valve drive circuit 18 outputs the opening information such that the concentration sensor S4 has a predetermined value, and the control is performed according to this. The opening degree of the valve V4 increases and decreases, and the flow rate of the adjustment pipeline L2 changes.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 4, in the second embodiment, the prescribed pipeline L1 is not composed of two pipelines, but is composed of a fourth pipeline d1.
By switching the pressure of the pressure regulator 20 between high and low stages, the flow rate of the regulated pipeline L1 is increased to the start-up flow rate (430 l).
/ Min) and the specified flow rate (80 l / min). Therefore, the fifth on-off valve V5 is kept open even after the time Tb when the start-up is completed. Since the other points are the same as those in the first embodiment, description thereof will be omitted.

[0015]

The chisso reflow apparatus of the present invention is provided with a furnace body, a conveyor for carrying a substrate from the entrance to the exit of the furnace body, a furnace arranged in the furnace body, and carried to the conveyor along a predetermined temperature profile. A concentration sensor for detecting the concentration in the furnace body, and a prescribed flow path that discharges a rising flow rate at startup or a specified flow rate of nitrogen gas below this rising flow rate to the furnace body, At the time of start-up, there is a control circuit that controls the flow rate of the adjusting pipeline by inputting the output of the concentration sensor while switching the flow rate of the regulating pipeline and the regulated pipeline that discharges a variable flow of nitrogen gas into the furnace. It is possible to rapidly increase the nitrogen gas concentration in the furnace body and accurately control the nitrogen gas concentration in the furnace body after startup.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a chisso reflow device according to the first embodiment of the present invention.

FIG. 3 is a graph showing the change over time in the flow rate in each of the pipelines of the chisso reflow device according to the first embodiment of the present invention.

FIG. 4 is a partial side view of a chisso reflow device according to a second embodiment of the present invention.

FIG. 5 is a graph showing a change over time in the flow rate in each pipe of the chisso reflow device according to the second embodiment of the present invention.

[Explanation of symbols]

 1 Furnace Body 1c Inlet 1d Outlet 2 Conveyor 4 Substrate 14 Control Circuit H1, H2, H3, H4 Heater S4 Concentration Sensor L1 Specified Pipeline L2 Adjustment Pipeline

Claims (1)

[Claims] 1. A furnace body, a conveyor for transporting a substrate from an inlet to an outlet of the furnace body, and a furnace arranged in the furnace body,
And a heater for heating the substrate conveyed to the conveyor along a predetermined temperature profile, a concentration sensor for detecting the concentration in the furnace body, and a startup flow rate at the time of startup in the furnace body or this startup A specified pipeline for discharging nitrogen gas at a specified flow rate below the flow rate, an adjusting conduit for discharging nitrogen gas at a variable flow rate into the furnace body, and a flow rate switching of the specified pipeline, while inputting the output of the concentration sensor. And a control circuit for controlling the flow rate of the adjusting pipe.