JPH04322878A - Inert gas atmosphere reflow soldering device - Google Patents

Abstract

PURPOSE:To curtail the nitrogen gas quantity for preventing oxidation, injected into a reflow furnace. CONSTITUTION:Nitrogen gas is injected into a reflow furnace 11 from a nitrogen gas injecting part 17, and by a heater 12 and a stirring machine 13, a nitrogen gas atmosphere of a high temperature is formed in the furnace. A work W is carried into the atmosphere by a conveyor 14 and reflow soldering is executed. In a work carrying-in part 15 of the reflow furnace 11, and infrared-ray lamp 31 and an infrared-ray sensor 32 for detecting a work are provided. In a gas injection duct line 24 connected to the nitrogen gas injecting part 17, a solenoid valve 33 is provided. This solenoid valve 33 is switched and operated through an amplifier 34 by a work existence/advance signal from the sensor 32, and executes increase/decrease control of the nitrogen gas flow rate. While the sensor 32 is detecting the work W within a prescribed time, a state that the solenoid valve 33 is fully opened is held by a signal from the sensor 32, and a large quantity of nitrogen gas is injected into the furnace. When a state that there is no work W is continued, the solenoid valve 33 constricts the gas injection duct line 24, and limits the injection flow rate of nitrogen gas injected into the furnace.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Industrial Application Field] The present invention relates to an inert gas atmosphere reflow soldering apparatus for carrying workpieces by a conveyor into a high temperature inert gas atmosphere formed inside a reflow oven and performing reflow soldering thereon. be.

0003

2. Description of the Related Art As shown in FIG. 2, a conventional inert gas atmosphere reflow soldering apparatus injects an inert gas such as nitrogen gas into a reflow oven 11 and uses a heater 12 and a stirrer 13 to A high-temperature inert gas atmosphere is formed, and a work W (on which electronic components are mounted via solder paste printed on a board) is transported by a conveyor 14 into the high-temperature inert gas atmosphere and heated. Therefore, soldering is performed by reflowing the solder paste.

It is known that the lower the oxygen concentration in the reflow furnace 11 by injecting an inert gas, the better the reflow solder will spread and the more solder balls will be generated.

The reflow oven 11 includes a workpiece loading section 15 and a workpiece unloading section 16, and is provided from the workpiece loading section 15 to the workpiece unloading section 16, passing through the conveyor 14 for conveying the workpiece. An inert gas injection section 17 is provided at the lower part of the reflow oven 11, and an inert gas such as nitrogen gas is injected into the oven from here.

[0006]

[Problem to be Solved by the Invention] Conventionally, a large amount of inert gas is always injected into the furnace from the inert gas injection part 17 regardless of the presence or absence of the workpiece W, so this inert gas is consumed. The amount is large and running costs are high.

The present invention was developed in view of the above points, and by controlling the flow rate of inert gas injected into the reflow oven depending on the presence or absence of a workpiece, consumption can be reduced within a range that does not interfere with reflow soldering. The purpose is to reduce the amount of inert gas used.

[Configuration of the invention]

[0009]

[Means for Solving the Problems] The present invention provides a reflow oven 1
Inert gas is injected into the furnace from the inert gas injection part 17 provided in 1, and the work W is carried by the conveyor 14 into the high-temperature inert gas atmosphere formed in the furnace to perform reflow soldering. In the inert gas atmosphere reflow soldering device, the workpiece loading section 15 of the reflow oven 11 is
A sensor 32 for detecting the work W is provided, and a valve 33 is provided in the gas injection pipe 24 connected to the inert gas injection section 17 for controlling the inert gas flow rate to increase or decrease based on the work presence signal from the sensor 32. This is an inert gas atmosphere reflow soldering device.

0010

[Operation] According to the present invention, the workpieces W sequentially carried into the reflow oven 11 within a predetermined time are detected by the sensor 3 of the workpiece carrying section 15.
If detected, the valve 33 of the gas injection pipe 24 is kept sufficiently open by the signal from this sensor 32, and a large amount of inert gas is injected into the furnace from the inert gas injection part 17. . Furthermore, if the workpiece W is not detected by the sensor 32 for a predetermined period of time, the valve 33 throttles the gas injection pipe 24 to limit the flow rate of the inert gas injected into the furnace.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to an embodiment shown in FIG. Note that the same reference numerals are used for the same parts as in the conventional example shown in FIG.

The inside of the reflow oven 11 is divided into two parts by a partition wall 21.
It is divided to form a preheat chamber 22 on the workpiece carry-in side and a reflow chamber 23 on the workpiece carry-out side.

[0013] At the bottom of the reflow oven 11, a preheat chamber 2 is provided.
An inert gas injection section 17 for injecting an inert gas such as nitrogen gas into the reflow chamber 2 and the reflow chamber 23 is provided, respectively, and a gas injection pipe line 24 is connected to the inert gas injection section 17. Furthermore, it is conventional to provide a heater 12 for heating an inert gas atmosphere and a stirrer 13 for stirring the inert gas atmosphere to obtain a uniform temperature distribution inside the preheat chamber 22 and the reflow chamber 23, respectively. It is similar to The preheat chamber 22 is maintained at a relatively low preheat temperature, and the reflow chamber 23 is maintained at a high reflow temperature.

A duct-shaped workpiece loading section 15 is provided for the preheating chamber 22, a duct-shaped workpiece loading section 16 is provided for the reflow chamber 23, and a conveyor 14 for transporting the workpieces is provided from the workpiece loading section 15 to the workpiece unloading section 16. It is also the same as the conventional method.

The workpiece W transported by the conveyor 14 is printed with solder paste on a printed wiring board, and
Electronic components are mounted via this solder paste.

The work loading section 15 of the reflow oven 11 is provided with an infrared lamp 31 and an infrared sensor 32 facing the infrared lamp 31 for detecting the work W based on the presence or absence of infrared rays. Further, a valve 33 is provided in the gas injection pipe 24 connected to the inert gas injection part 17 of the reflow oven 11. This valve 3
3 switches the reflow oven 11 between the fully open state and the throttle resistance state based on the work presence signal from the infrared sensor 32.
This is a solenoid valve that controls the increase/decrease of the flow rate of inert gas injected into the inert gas, and its solenoid is connected to an infrared sensor 32 via an amplifier 34.

Next, the operation of this embodiment will be explained.

The workpiece W is conveyed by the conveyor 14 to a workpiece loading section 15, a preheating chamber 22, a reflow chamber 23, and a workpiece unloading section 16 in this order. And preheat chamber 2
2, the workpiece W is preheated, and the solder paste on the workpiece W is reflowed in a high-temperature inert gas atmosphere in the reflow chamber 23 to solder the board and the components.

Since such soldering is performed in an inert gas atmosphere, when the conveyor 14 carries the workpiece W into the workpiece loading section 15, the infrared sensor 32 automatically detects the loading of the workpiece W and turns on the amplifier 34. Then, the valve 33 is switched to the fully open state, and the flow rate of the inert gas injected into the furnace is increased to a predetermined amount. This state is maintained as long as there is a workpiece W passing through the workpiece loading section 15 within a predetermined period of time.

On the other hand, when this reflow soldering apparatus is idling, the next workpiece is not carried into the workpiece loading section W even after the predetermined workpiece passage time has elapsed, so that the valve 33 is closed to the inert gas The flow rate is automatically reduced, and only the minimum amount of inert gas necessary to maintain an inert gas atmosphere inside the furnace is injected.

[0021]

According to the present invention, a sensor for detecting a workpiece is provided in the workpiece loading section of a reflow oven, and a gas injection line connected to an inert gas injection section into the reflow oven is provided with a sensor for detecting the workpiece. We have installed a valve that increases or decreases the inert gas flow rate based on the workpiece presence signal, so when the workpiece is not carried into the furnace, such as when the workpiece is idling, the sensor does not detect the workpiece, so the valve is automatically throttled and the flow rate inside the furnace is reduced. Only the minimum amount of inert gas necessary to maintain an inert gas atmosphere can be injected, reducing the amount of inert gas consumed compared to conventional methods, and has the effect of reducing running costs.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of an inert gas atmosphere reflow soldering apparatus of the present invention.

FIG. 2 is a sectional view showing a conventional inert gas atmosphere reflow soldering apparatus.

[Explanation of symbols]

W Work 11 Reflow oven 14 Conveyor 15 Work loading section 17 Inert gas injection part 24 Gas injection pipe 32 Sensor 33 Valve

Claims (1)

[Claims] Claim 1: Inert gas is injected into the furnace from an inert gas injection part provided in the reflow furnace, and the workpiece is carried by a conveyor into the high-temperature inert gas atmosphere formed in the furnace to perform reflow soldering. In an inert gas atmosphere reflow soldering apparatus that performs soldering, a sensor for detecting a workpiece is installed in the workpiece loading section of the reflow oven, and the workpiece from the sensor is connected to the gas injection pipe connected to the inert gas injection section. An inert gas atmosphere reflow soldering device characterized by being provided with a valve that controls increasing/decreasing of an inert gas flow rate based on a presence/absence signal.