JPH0377774A - Method and device for brazing - Google Patents

Abstract

PURPOSE:To make uniform the heating temperature and to improve reliability of soldering by changing the moving speed of material to be soldered from the low speed to the high speed while being into contact with a jet stream of molten solder. CONSTITUTION:A speed controller 12 drives a motor 10 so as to move a hanger at the specified speed. The hanger is moved up to the position where a sensor sensing piece 7A is sensed by a sensor 8 and when its positional signal is outputted from a position detection circuit 11, the speed controller 12 decelerates the motor 10 so as to attain the specified moving speed. A printed board 6 starts to come into contact with solder waves 2 from the tip at this speed. When the tip of the printed board 6 comes into contact with the solder waves in this way, the moving speed is made to the lowest speed and then, the moving speed is increased gradually, by which the printed board is heated and brazed at the almost uniform temperature from the tip to a rear end. By this method, characteristic deterioration of a packaging component can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a soldering method and apparatus for printed circuit boards, etc., and particularly to a soldering method and apparatus for moving a printed circuit board, etc. while bringing it into contact with a jet of molten solder. Regarding.

[Conventional technology]

To solder electronic components mounted in the through-holes of a printed circuit board, the printed circuit board is moved while a jet (wave) of molten solder is brought into contact with the back surface of the printed circuit board. So-called wave soldering methods and equipment have been widely adopted.

Conventionally, this type of soldering device was disclosed in Japanese Patent Application Laid-Open No. 49-984.
As shown in Publication No. 22, a printed circuit board (object to be soldered) is held in a holder.

After applying Franks and preheating with a preheater,
Soldering of the connecting portions of the printed circuit board is carried out by moving the printed circuit board in contact with the solder wave, but the moving speed during the period of contact between the printed circuit board and the solder wave is kept approximately constant.

That is, conventionally, the period of contact between the printed circuit board and the solder wave was approximately constant from the far end to the rear end of the printed circuit board.

[Problem to be solved by the invention]

When the tip of the printed circuit board comes into contact with the solder wave, the board temperature is still low, so the heat from the solder spreads from the tip to other parts, making it difficult for the temperature of the tip to rise. At the rear end, the temperature has already increased due to heat conduction within the board before contacting the solder wave, so even if it is in contact with the solder wave for the same amount of time.

If the printed circuit board is moved at a constant speed as in the conventional method, the heating temperature of the printed circuit board will be uneven. Such a heating temperature difference within the printed circuit board was tolerable for a small, low-density circuit board.

However, in recent years with large, high-density printed circuit boards, the heating temperature difference within the board has increased, and the impact on bonding quality and the characteristics of mounted electronic components can no longer be ignored.

In other words, as printed circuit boards become larger and more dense, the board thickness and heat capacity increase, so if you try to heat the tip of the printed circuit board, where the temperature is least likely to rise during soldering, to the required temperature, The speed at which the printed circuit board moves must be considerably slowed down, but this will significantly increase the temperature at the rear edge of the printed circuit board, increasing the heating temperature difference within the board to an unacceptably high degree, leading to poor bonding reliability and damage to the mounted components. This may lead to deterioration of the characteristics.

An object of the present invention is to provide a method and apparatus that reduce the difference in heating temperature of objects to be soldered and enable highly reliable soldering even on large, high-density printed circuit boards.

[Means to solve the problem]

In order to achieve the above object, the present invention controls the moving speed of the soldering object from low speed to high speed during the contact period between the soldering object and the solder wave, and also controls the moving speed of the soldering object from low to high speed. This is done by detecting the relative position of the soldering object to the solder wave, or by detecting the temperature difference between the part of the soldering object that is in contact with the solder wave and the non-contact part behind it. It is done by doing this.

[For production]

As the object to be soldered moves, its tip comes into contact with the solder wave, and the temperature of the contact area rises. At the same time, heat escapes to the rear end by heat conduction of the object to be soldered, causing damage to other parts. temperature also increases. In other words, the contact time with the solder wave required to heat the object to be soldered to a certain temperature decreases as it goes from the tip to the rear end.

Therefore, according to the method of the present invention, by appropriately changing the moving speed of the soldering object from low speed to high speed during the period of contact with the solder wave, the period of contact with the solder wave can be changed. The heating temperature can be appropriately decreased from the tip to the rear end, and the heating temperature of the soldered object can be made uniform.1 For example, the reliability of soldering large, high-density printed circuit boards can be improved, and excessive It is possible to prevent the characteristics of mounted components from deteriorating due to heating.

Further, according to the soldering device of the present invention, the relative position of the soldering object to the solder wave is detected, and the moving speed is controlled as described above based on the result, thereby achieving highly reliable soldering. It is possible to do this.

Furthermore, the temperature difference between the part of the object to be soldered that is in contact with the solder wave and the part that is not in contact with the solder wave becomes maximum when the tip of the object to be soldered comes into contact with the solder wave. The temperature difference decreases as the contact portion with the wave moves toward the rear end. Therefore, according to the soldering apparatus of the present invention, the moving speed of the soldering object can be appropriately controlled as described above so as to be substantially inversely proportional to this temperature difference, and highly reliable soldering can be performed.

〔Example〕

FIG. 1 is a schematic plan view of a soldering apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing changes in the moving speed of a printed circuit board (object to be soldered) in this embodiment.

In FIG. 1, a solder bath 1 is filled with molten solder, and a screw (not shown) is provided inside the bath 1 for generating a jet or wave 2 of molten solder. This screw is driven by a motor 3. 5 is a hanger that moves on the conveyor rail 4 while holding the printed circuit board 6;
It is driven by a motor 10 via.

In order to detect the relative position of the printed circuit board 6 with the solder wave 2, sensor sensing pieces 7A, 7B, 7G, and 7D are provided at appropriate positions on one side of the hanger 5, and a sensor is provided to reduce the approach thereof. The 0 position detection circuit 11, in which sensor 8 is provided at a proper position, detects the positions A, B, and C in FIG. 2 based on the output of this sensor 8.

This is to detect each relative position of D. The speed controller 12 responds to the detection output of the position detection circuit 11,
The motor 10 is driven to move the printed circuit board 6 at a speed as shown in FIG.

Next, the operation will be explained. Initially, the speed controller 12 moves the hanger 5 at the speed A shown in FIG.
drives the motor 10.

When the hanger 5 moves to the position where the sensor sensing piece 7A is sensed by the sensor 8 (position A in FIG. 2) and the position detection signal is output from the position detection circuit 11, the speed controller 12 The motor 10 is decelerated so as to achieve the moving speed of the mouth shown in the figure.

At this speed, the printed circuit board 6 starts to come into contact with the solder wave 2 from the tip. When the hanger 5 advances further and the sensor sensing piece 7B is sensed by the sensor 8, that is, when it reaches the relative position B in FIG. To accelerate.

Further, proceed to the relative position C in Fig. 2, and the sensor sensing piece 7
When the sensing signal C is output from the sensor 8, the speed controller 12 controls the motor 10 so that the speed is as shown in FIG.
accelerate again.

Thereafter, when the hanger 5 moves to a position where the sensor sensing piece 7D is sensed by the sensor 8, the speed controller 1
2 accelerates the motor 10 again and returns the moving speed to the speed A in FIG.

In this way, the moving speed is set to be the slowest when the leading end of the printed circuit board 6 comes into contact with the solder wave, and then the moving speed is gradually increased to maintain a substantially uniform temperature from the leading end to the rear end of the printed circuit board 5. Can be heated and soldered. Note that FIG. 2 only conceptually shows how the speed changes.

FIG. 3 is a schematic plan view of a soldering apparatus according to another embodiment of the present invention, FIG. 4 is a diagram schematically showing changes in the moving speed of the printed circuit board in this embodiment, and FIG. It is a figure showing the relationship between temperature difference and movement speed.

In FIG. 3, the hanger 5 is provided with two sensor sensing pieces 7E and 7F at the positions shown. Also, the surface temperature (T
A temperature measuring device 13A for measuring 1) without contact and a temperature measuring device 13B for measuring the surface temperature (T2) of the printed circuit board 6 from above at a position rearward from this without contact are provided. . As these temperature measuring devices L3A and 13B, for example, infrared temperature measuring devices are used.

15A and 15B are circuits that convert the detection signals of the temperature measuring devices 13A and 13B into signals suitable for calculation; 16 is a circuit that calculates the temperature difference ΔT (=Tl-T2) from the converted signals;
17 is a fourth sensor according to the temperature difference and the detection signal from the sensor 8.
This is a speed controller h roller that performs speed control as shown in the figure.

Other than this, this embodiment is the same as the embodiment described above.

Next, the operation will be explained. The speed controller 17 controls the motor 10 so that the hanger 5 is moved at the speed shown in FIG.
to drive.

When the hanger 5 moves to a position where the tip of the printed circuit board 6 contacts the solder wave 2, the sensor 8 outputs a sensing signal from the sensor sensing piece 7E.

The speed controller 17 switches to the variable speed mode, and drives the motor 10 to move the printed circuit board 6 at a speed C that is approximately inversely proportional to the temperature difference ΔT, according to the temperature difference function f(ΔT) as shown in FIG. control.

When the tip of the printed circuit board 6 comes into contact with the solder wave, the temperature of the portion behind it is low and the temperature difference ΔT is large, so the moving speed is slow.Then, as the contact portion moves toward the rear end, the Since the temperature difference ΔT decreases, the moving speed gradually increases.

When the hanger 5 moves to a position where the sensing signal of the sensor sensing piece 7F is output from the sensor 8, the speed controller 1
7 returns to constant speed mode, and the hanger 5 moves at the speed of A in Figure 4.
The motor 10 is driven to move the .

By adjusting the movement speed as described above, the heating temperature of the printed circuit board 6 is approximately equalized, and highly reliable soldering becomes possible.

Since the purpose of controlling the movement speed of the printed circuit board is to equalize the heating temperature of the printed circuit board, the method of directly monitoring the temperature of the printed circuit board as in this example makes it possible to uniformize the heating temperature with high precision. It is achievable.

Note that the mechanism for moving the printed circuit board, etc. may be changed as necessary.

〔Effect of the invention〕

As explained above, according to the present invention, during the period of contact with the solder wave of the object to be soldered.

By appropriately controlling the moving speed of the soldering object and making the heating temperature uniform, it improves the reliability of soldering large, high-density printed circuit boards, etc., and also prevents the deterioration of the characteristics of the components mounted on printed circuit boards. Effects such as prevention can be obtained.

[Brief explanation of drawings]

FIGS. 1 and 2 are a schematic plan view of a soldering device and a diagram showing the moving speed of a printed circuit board according to an embodiment of the present invention, respectively, and FIGS. 3 to 5 are diagrams showing other embodiments of the present invention. FIG. 1 is a schematic plan view of a soldering apparatus according to an example, a diagram showing a moving speed of a printed circuit board, and a diagram showing a speed function. 1...Solder bath, 2...Solder wave. 3...Screw drive motor, 4...Conveyor rail, 5...Hanger 6...
Printed board. 7A to 7F...Sensor sensing piece, 8...Sensor, 9
...Chain, 10...Hanger drive motor. 11...Position detection position, 12.17...Speed controller. 13A, 13B...Temperature measuring device, 15A, 15B...Temperature detection circuit, Fig. 1 Fig. 2 B QD Wood grain nuchoi vertical crush → -Baisei

Claims (3)

[Claims] (1) In a soldering method in which the object to be soldered is moved while being in contact with a jet of molten solder, the moving speed of the object to be soldered is changed from low to high speed during the period in which the object is in contact with the jet of molten solder. A soldering method characterized by: (2) means for moving the object to be soldered along a certain path, and means for generating a jet of molten solder to bring it into contact with the object to be soldered in the middle of the path; means for detecting the relative position of the object to be soldered with respect to the molten solder jet; and depending on the detection result by the detecting means,
A soldering apparatus characterized by comprising means for controlling the moving speed of the moving means from low speed to high speed during the period of contact between the object to be soldered and the molten solder jet. (3) Means for moving the object to be soldered along a certain path, means for generating a jet of molten solder to bring the object to be soldered into contact with the object to be soldered in the middle of the path, and means for moving the object to be soldered along a certain path; , a means for detecting the temperature of a portion in contact with the molten solder jet and a temperature of a portion downstream thereof that is not in contact with the molten solder jet; and a moving speed of the moving means, which is detected by the temperature detecting means. 1. A soldering device comprising means for controlling the temperature so that the temperature difference is substantially inversely proportional to the difference in temperature.