JP3420283B2 - Method and apparatus for controlling oxygen concentration in soldering apparatus for inert atmosphere - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, in order to improve soldering characteristics, uses an inert gas in a reflow furnace or a jet chamber for soldering to create a soldering atmosphere having an oxygen concentration lower than that of the atmosphere. The present invention relates to a method and apparatus for controlling oxygen concentration in an inert atmosphere soldering apparatus that operates by injection.

[0002]

2. Description of the Related Art FIG. 4 shows a reflow furnace for soldering, in which an atmosphere circulation system is formed inside a furnace body 11 by a blower 12 and a guide plate 13, and a catalyst such as platinum 1 is formed in this atmosphere circulation system.
4, the heater 15 and the work (surface-mounted substrate W) transfer line are arranged, the substrate W is carried into the furnace, and reflow soldering is performed in a high temperature atmosphere.

By operating by injecting an inert gas such as nitrogen gas in such a reflow furnace, a soldering atmosphere having an oxygen concentration lower than that of the atmosphere as shown in FIG. We are trying to improve

In FIG. 5, A is the time required to start up the apparatus until a constant low oxygen concentration atmosphere is formed in the furnace, and this time A is when nitrogen gas is fully opened and injected into the furnace. Further, B is the time during which the substrate W is put into the furnace and soldering is performed. During this time, the flow rate of nitrogen gas is controlled to control the oxygen concentration within a certain range.

Generally, only nitrogen gas is injected as an inert gas into the reflow furnace, and if the injection flow rate is increased, the result shown in FIG.
As indicated by b1, the oxygen concentration in the atmosphere further decreases, and conversely, if the injection flow rate of nitrogen gas is reduced, the oxygen concentration increases as indicated by b2 in FIG.

Due to the intermittent supply of the substrate W to be soldered into the reflow furnace and the change in the supply amount, the amount of air brought into the soldering atmosphere from the outside by the substrate W also changes, and the oxygen concentration in the atmosphere fluctuates. However, this will lead to changes in soldering quality.

If the oxygen concentration is low, the soldering quality can be improved, but the nitrogen gas consumption is increased and the running cost is increased. Further, generally, when liquid nitrogen is vaporized and supplied as high-purity gas to a soldering apparatus, nitrogen gas needs to have a concentration of several hundred ppm or less to stabilize the oxygen concentration.

[0008]

The conventional method of injecting only nitrogen gas into the reflow furnace and changing the injection amount of only nitrogen gas to control the oxygen concentration is controlled to increase the oxygen concentration. At this time, since the nitrogen gas injection flow rate is reduced, the nitrogen gas consumption can be saved. However, if the injection flow rate is extremely reduced, the overshoot when the oxygen concentration rises becomes large and the stability of the oxygen concentration decreases.

Particularly, for the purpose of combining isopropyl alcohol generated from the soldering flux with oxygen in the atmosphere to decompose into carbon dioxide and water, a catalyst such as platinum 14 is provided in the atmosphere circulation system as shown in FIG. In the case where the catalyst is provided, if the substrate is not charged as shown by C in FIG. 5, the above-described action of the catalyst 14 may lower the oxygen concentration more than necessary as shown by the curves c1 and c2.

In this case, although the nitrogen gas injection flow rate is extremely reduced and the oxygen concentration rises and returns, it is difficult to recover the oxygen concentration to a desired value unless the substrate is charged. Further, once the nitrogen gas injection flow rate is extremely reduced, there is a problem that the overshoot when the oxygen concentration rises becomes large and the control accuracy deteriorates.

The present invention has been made in view of the above circumstances, and improves the stability and responsiveness when controlling the oxygen concentration within a limited range when soldering in an inert atmosphere. This is intended to be achieved.

[0012]

According to a first aspect of the present invention, in an inert atmosphere soldering apparatus for soldering in a low oxygen concentration atmosphere into which an inert gas is injected, the oxygen concentration in the atmosphere is measured. However, the oxygen concentration in the inert atmosphere soldering device is configured to control the injection flow rate of the inert gas in order to approach the desired oxygen concentration and forcibly supply the air whose flow rate is adjusted into the atmosphere as necessary. It is a control method.

The invention according to claim 2 is the method for controlling oxygen concentration according to claim 1, wherein air is directly supplied into the atmosphere.

According to a third aspect of the present invention, in the oxygen concentration control method according to the first aspect, air is mixed in the inert gas supplied into the atmosphere.

According to a fourth aspect of the present invention, in an inert atmosphere soldering apparatus for soldering in a low oxygen concentration atmosphere formed by injecting an inert gas, the inert gas is forcibly injected into the atmosphere. Inert gas injection circuit, an air mix circuit for forcibly mixing air into the atmosphere, flow control valves provided in the inert gas injection circuit and the air mix circuit, respectively An oxygen concentration meter that measures the oxygen concentration, and each flow rate control valve of the inert gas injection circuit and the air mix circuit to bring the oxygen concentration in the atmosphere closer to the desired oxygen concentration based on the measurement values obtained from this oxygen concentration meter. Is an oxygen concentration control device in an inert atmosphere soldering device having a configuration for controlling the temperature.

[0016]

According to the invention described in claim 1, when the oxygen concentration is increased more than necessary, the flow rate of the inert gas is increased, and when the oxygen concentration is decreased more than necessary, the flow rate of air is adjusted. By adding, the oxygen concentration is raised and returned without extremely reducing the flow rate of the inert gas, and the oxygen concentration is stabilized within a certain range. In addition, the flow rate of the inert gas
By adjusting both the flow rate of air and the flow rate of air, the oxygen concentration setting
Quickly respond to fixed setting changes.

According to the second aspect of the present invention, air is directly supplied into the atmosphere to raise and return the oxygen concentration in the atmosphere within a certain range.

According to the third aspect of the present invention, air is mixed into the inert gas supplied into the atmosphere to raise and restore the oxygen concentration in the atmosphere within a certain range.

According to a fourth aspect of the present invention, when the oxygen concentration rises more than necessary, the controller which detects it by the oxygen concentration meter controls the flow control valve of the inert gas injection circuit in the opening direction so that it is not activated. If the flow rate of the active gas is increased and the oxygen concentration drops more than necessary, the controller that detects it with an oxygen concentration meter adjusts the flow rate of the inert gas injection circuit and the flow rate of the air mix circuit. By controlling the valve and adding air while controlling the flow rate of the inert gas without extremely restricting the flow rate of the inert gas, the oxygen concentration is increased and returned to be stabilized within a certain range. In addition, the inert gas injection circuit
Adjust the flow rate of the inert gas with the flow control valve
Together with the air flow rate control valve
This enables quick response to changes in oxygen concentration settings.
It

[0020]

The present invention will be described in detail below with reference to a reflow type embodiment shown in FIG. 1, an oxygen concentration control example shown in FIG. 2 and a jet flow type embodiment shown in FIG.

FIG. 1A shows an example in which the present invention is applied to a reflow type soldering apparatus. The inside of the furnace body 11 is partitioned by a partition plate 16 to form a plurality of preheat chambers and reflow chambers.

The structure of the preheat chamber or reflow chamber is
As in FIG. 4, an atmosphere circulation system is formed inside the furnace body 11 by a blower 12 and a guide plate (not shown), and a catalyst line 14 of platinum or the like, a heater 15, and a work (surface-mounted substrate W) transfer line are formed in this atmosphere circulation system. To place.

As shown in FIG. 1A, an oxygen concentration control device for controlling the oxygen concentration in the furnace is provided at least in the reflow chamber.

This oxygen concentration control device comprises an inert gas injection circuit 21 for forcibly injecting an inert gas (nitrogen gas) into the atmosphere and an air mix circuit 22 for forcibly mixing air into the atmosphere. Have.

The inert gas injection circuit 21 is composed of a tank 31 containing liquid nitrogen, an evaporator 32, a pressure reducing valve 33, a flow rate adjusting valve 34, a nitrogen supply pipe 35 and a nitrogen injection nozzle 36, and is taken out from the tank 31. The liquid nitrogen is vaporized by the evaporator 32,
The pressure reducing valve 33 controls the set pressure, the flow rate adjusting valve 34 controls the flow rate, and the nitrogen injection nozzle 36 injects the nitrogen into the furnace body 11.

The air mix circuit 22 is composed of an air pressure source 41 such as a compressor, a pressure reducing valve 42, a flow rate adjusting valve 43, an air supply pipe line 44 and an air injection nozzle 45, and compressed air supplied from the air pressure source 41. Is controlled by the pressure reducing valve 42 to the set pressure, and the flow rate is controlled by the flow rate adjusting valve 43.
It is injected into the furnace body 11 by 45.

A tube 51 for sampling the atmosphere in the furnace is inserted into the furnace body 11, and a zirconia type oxygen concentration meter 53 for measuring the oxygen concentration in the atmosphere is connected to the tube 51 via a sampling gas suction pipe line 52. To do.

The output line of the oxygen concentration meter 53 is connected to a controller 54 for controlling the oxygen concentration in the furnace atmosphere within a desired oxygen concentration range.

The nitrogen gas flow rate control line 55 drawn from the regulator 54 is connected to a control motor provided in the flow rate adjusting valve 34 of the inert gas injection circuit 21. Also the regulator
An air flow rate control line 56 drawn from 54 is connected to a control motor provided in the flow rate adjusting valve 43 of the air mix circuit 22.

In the embodiment shown in FIG. 1 (A),
Although the air is directly supplied into the atmosphere by inserting the air injection nozzle 45 together with the nitrogen injection nozzle 36 into the furnace, as shown in FIG. 1 (B), the nitrogen injection nozzle 36 is inserted into the furnace. By inserting only, by connecting the air supply line 44 in the middle of the pipe to the nitrogen injection nozzle 36,
Air may be mixed in the nitrogen gas supplied into the atmosphere.

Next, the operation of the embodiment shown in FIG. 1 will be described. While measuring the oxygen concentration in the atmosphere in the furnace by the oxygen concentration meter 53, the controller 54 is arranged so as to approach the desired oxygen concentration.
The flow rate of nitrogen gas and air injected into the furnace is controlled by, and basically, reflow soldering is performed in a low oxygen concentration atmosphere in the furnace where nitrogen gas is injected.

For example, when the oxygen concentration in the atmosphere rises more than necessary, the controller 54 which detects it by the oxygen concentration meter 53 controls the flow rate adjusting valve 34 of the inert gas injection circuit 21 in the opening direction. Increase the nitrogen gas injection flow rate into the atmosphere.

On the other hand, when the oxygen concentration in the atmosphere has dropped more than necessary, the controller 54, which detects it by the oxygen concentration meter 53, controls the flow rate adjusting valve 34 of the inert gas injection circuit 21.
And the flow control valve 43 of the air mix circuit 22 are both controlled to increase the oxygen concentration in the atmosphere by forcibly adding the air whose flow rate is adjusted to the atmosphere in the furnace without extremely narrowing the nitrogen gas flow rate. Restore and stabilize within a certain range.

FIG. 2 shows an example of oxygen concentration control in the reflow soldering apparatus shown in FIG. 1. The first half shows the case where the oxygen concentration is set to 300 ppm, and the second half sets the oxygen concentration to 1000 ppm. This is the case.

In FIG. 2, A is the time required to start up the apparatus until a constant low oxygen concentration atmosphere is formed in the furnace, and during this period, t1 to t3 are injected into the furnace while gradually squeezing the nitrogen gas from full opening. To do.

In FIG. 2, B is the time during which the substrate W is put into the furnace for soldering, and during this time, the substrate W is
When the oxygen concentration rises due to the air brought into the furnace, there is t4. At that time, the oxygen concentration is reduced by controlling the flow rate of nitrogen gas to temporarily increase.

In FIG. 2C, since the substrate W is not charged into the furnace, the action of the catalyst 14 such as platinum promotes the combination of isopropyl alcohol and oxygen in the furnace, and the oxygen concentration is higher than necessary. In this case, air is forcibly supplied into the furnace to raise the oxygen concentration.

In FIG. 2, D indicates the oxygen concentration setting, for example.
This is an example of control when changing to 1000ppm, and air can be forcibly supplied into the furnace to rapidly raise the oxygen concentration to the set value, enabling quick response to setting changes.

The flow rates of nitrogen gas and air supplied into the furnace at the respective times shown in FIG. 2 are as shown in Table 1 below.

[0040]

[Table 1]

As described above, when the soldering quality can be kept constant as a result, the amount of oxygen concentration increase per substrate (for example, 30
(ppm) can be kept small as a fluctuation rate, and it is possible to easily manage the condition of work.

FIG. 3 is an example in which the present invention is applied to a jet type soldering apparatus. A preheater 62 and a jet solder bath 63 are arranged along a transfer line 61 of a substrate W, and the preheater 62 and the jet solder bath 63 are arranged. Is covered with a chamber 64, and a nitrogen injection nozzle 36 for injecting nitrogen gas and an air injection nozzle 45 for injecting air are provided on the solder bath in the chamber 64. Also, the chamber 64
A tube 51 is inserted therein for sampling the soldering atmosphere. The oxygen concentration control device shown in FIG. 1A is connected to the nozzles 36 and 45 and the tube 51.

[0043]

According to the invention described in claim 1, when the oxygen concentration is increased, the flow rate of the inert gas is increased, and
If the oxygen concentration drops more than necessary, air can be added while adjusting the flow rate to rapidly increase and restore the oxygen concentration in the atmosphere without extremely reducing the flow rate of the inert gas, and keep the oxygen concentration constant. It can be stabilized within the range. Furthermore, the flow rate of the inert gas and the flow rate of the air are both
By adjusting the flow rate, it is easy to change the oxygen concentration setting.
Can handle speed.

According to the second aspect of the present invention, it is possible to supply air directly into the atmosphere to control the return of the increase in oxygen concentration when the oxygen concentration is too low.

According to the third aspect of the invention, by mixing air into the inert gas supplied into the atmosphere, it is possible to control the return of the increase in oxygen concentration when the oxygen concentration is too low.

According to the invention of claim 4, claim 1
It is possible to provide an oxygen concentration control device that can effectively implement the control method described in 1. In addition, adjust the flow rate of the inert gas injection circuit.
Adjusting the flow rate of inert gas by adjusting valve and air mix circuit
Together with the air flow rate adjustment valve
Thus, it is possible to quickly respond to changes in oxygen concentration settings.

[Brief description of drawings]

FIG. 1A is a sectional view of a reflow furnace showing a reflow type embodiment of the present invention and a circuit diagram of an oxygen concentration control system. B is a sectional view showing a modified example of the air injection portion.

FIG. 2 is a graph of oxygen concentration over time showing an example of controlling the oxygen concentration of the above-mentioned embodiment.

FIG. 3 is a cross-sectional view showing a jet type embodiment according to the present invention.

FIG. 4 is a cross-sectional view of a general reflow furnace.

FIG. 5 is a graph of oxygen concentration over time showing an example of conventional oxygen concentration control.

[Explanation of symbols]

21 Inert gas injection circuit 22 Air mix circuit 34, 43 Flow control valve 53 Oxygen analyzer 54 Controller

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minoru Adachi, Minoru Adachi, 11 Samura Plant, Sayama City, 591, Higashikubo, Higashikubo, Tamura Seisakusho Co., Ltd. (56) Reference JP-A-4-356349 (JP, A) 5-13949 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 31/02 B23K 1/00-1/08

Claims (4)

(57) [Claims] 1. An inert atmosphere soldering apparatus for soldering in an atmosphere of low oxygen concentration in which an inert gas is injected, in order to bring the oxygen concentration close to a desired oxygen concentration while measuring the oxygen concentration in the atmosphere. A method of controlling oxygen concentration in an inert atmosphere soldering device, characterized in that the injection flow rate of is controlled and the air whose flow rate is adjusted is forcibly supplied into the atmosphere as necessary. 2. The oxygen concentration control method in an inert atmosphere soldering device according to claim 1, wherein air is directly supplied into the atmosphere. 3. The oxygen concentration control method in an inert atmosphere soldering device according to claim 1, wherein air is mixed in an inert gas supplied into the atmosphere. 4. In an inert atmosphere soldering device for soldering in an atmosphere of low oxygen concentration formed by injecting an inert gas, an inert gas injection circuit for forcibly injecting an inert gas into the atmosphere. The air mix circuit for forcibly mixing air into the atmosphere, the flow control valves provided in the inert gas injection circuit and the air mix circuit, and the oxygen concentration for measuring the oxygen concentration in the atmosphere by sampling the atmosphere Meter and a controller that controls each flow rate adjusting valve of the inert gas injection circuit and the air mix circuit in order to bring the oxygen concentration in the atmosphere closer to the desired oxygen concentration based on the measurement value obtained from this oxygen concentration meter. An oxygen concentration control device in an inert atmosphere soldering device, comprising: