JPH0832226A - Method and apparatus for laser reflow - Google Patents

Abstract

PURPOSE:To realize good soldering by a method wherein the soldering is effected under same temperature conditions at the points of different thermal capacity in order to prevent defective soldering due to overheating or underheating. CONSTITUTION:In the preset stage, an infrared temperature sensor 9 measures the heated temperature of a mounting pad 12 irradiated with laser light from a laser irradiation head 5. The intensity of laser for main process is set based on the heating temperature measured depending on the positional information of the laser irradiation head and the set laser intensity is stored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser reflow apparatus and method for melting a solder previously applied to an object for soldering with a laser, and more particularly to soldering a multi-terminal, multi-lead surface mount component to a substrate. The present invention relates to a laser reflow device for attaching.

[0002]

2. Description of the Related Art In soldering by laser reflow, a lead is aligned with a mounting pad on a printed circuit board to form an IC.
A surface mounting component such as the above is placed, the surface of the lead is irradiated with laser light and heated, and the solder previously applied to the mounting pad is melted to solder the mounting pad of the printed circuit board and the lead of the surface mounting component.

FIG. 5 is a block diagram of the conventional laser reflow apparatus of FIG. In the figure, a laser beam emitted from a laser device 6 driven by a laser driving unit 7 is transmitted to a laser irradiation head 5 via a photochemical system including a lens, a mirror, an optical fiber, etc., and is printed from the laser irradiation head 5. A single point on the substrate 8 is irradiated. The laser irradiation head 5 moves at a constant speed in the XY directions (in the direction of the plane parallel to the substrate 8) by the XY drive unit 4, and the irradiation point of the laser beam is the pad on the substrate 8 and the lead of the component mounted on the substrate 8. They were soldered by moving them along the row of connection points with. There is also a device that moves the table on which the printed circuit board 8 is placed in the XY directions instead of moving the laser irradiation head 5 by the XY drive unit 4.

The intensity of the laser beam emitted from the laser irradiation head 5 to the printed circuit board 8 can be set by an operator's input from the input / output unit 1 connected to the control unit 3. Further, the operator inputs in advance the XY coordinate values of the locus of movement of the laser irradiation head 5, the moving speed, the XY coordinate values of the portion for irradiating the laser beam, etc. from the input / output unit 1, and these information are input to the control unit 3. Storage unit 2 connected to
To be stored.

At the time of automatic operation of this laser reflow device, the control unit 3 follows the information stored in the storage unit 2 in the XY direction.
The drive unit 4 and the laser drive unit 7 are controlled to perform laser reflow soldering on the substrate 8 with a laser beam having a preset intensity according to the movement locus of the laser irradiation head 5 preset by the operator.

[0006]

In the conventional laser reflow soldering apparatus, the total reflow is performed at the preset laser irradiation head speed and laser irradiation intensity set at the preset time. Since the mounting pads on the printed circuit board on which the leads of the components are reflow-soldered have a constant width, the amount of heat supplied to each mounting pad by the laser beam becomes uniform. However, the heat capacity of the mounting pad differs depending on the presence or absence of the conductor pattern to be connected, the width, and the amount of solder applied in advance. Therefore, the molten solder temperature at the time of reflow is different for each mounting pad, which causes excess and deficiency of heating, resulting in problems regarding soldering quality such as thermal damage and unmelted solder.

[0007]

In the laser reflow apparatus of the present invention, a laser irradiation head for irradiating an object with a laser beam is moved relative to the object and pre-coated on the object. A laser reflow device for reflowing solder is provided with an infrared temperature sensor that moves with the laser irradiation head with respect to the object and measures the temperature of a point immediately after the irradiation point of the laser beam on the object moves. .

The laser reflow method of the present invention is a laser reflow method in which the irradiation point of a laser beam on an object is moved to reflow solder previously coated on the object. By moving the irradiation point of the intense laser beam while drawing a locus at a constant speed and simultaneously measuring the temperature of the point immediately after the movement of the irradiation point on the test object, The temperature increased by the irradiation of the laser beam is measured, and the intensity of the laser beam is adjusted so that each point on the locus is heated to the target temperature based on the measured temperature, and then the test beam is used. The object of the same type is characterized in that the trajectory is drawn by moving the irradiation point at the constant speed by the laser beam having the intensity adjusted for each of the trajectory points. To.

Alternatively, the moving speed of the irradiation point is adjusted so that each point on the locus is heated to the target temperature on the basis of the above-mentioned measured temperature, and thereafter, an object of the same type as that for the test is adjusted. In addition, the irradiation point of the laser beam having the constant intensity is moved at each speed on the locus at the adjusted speed to draw the locus.

[0010]

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

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a perspective view showing a laser irradiation head 5, an infrared temperature sensor 9 and a substrate 8 of this embodiment.

As shown in FIG. 2, a plurality of mounting pads 12 having a constant width are arranged on the printed circuit board 8.
Various conductor patterns 13 are connected to a part of the. The laser irradiation head 5 and the infrared temperature sensor 9 are arranged side by side on the upper side of the printed circuit board 8, and the temperature of the point immediately after the laser irradiation point of the laser irradiation head 5 of the printed circuit board 8 (in the movement of the laser irradiation head 5) is measured. The infrared temperature sensor 9 measures. For this purpose, the infrared temperature sensor 9 is swung so that it is always located on the opposite side of the traveling direction of the laser irradiation head 5 with the laser irradiation head 5 as the center.

In FIG. 1, the infrared temperature sensor 9 is supplied with power from the temperature measuring section 10, and the output signal of the infrared temperature sensor 9 is amplified by the temperature measuring section 10 and sent to the control section 3. The infrared temperature sensor 9 is swung around the laser irradiation head 5 by the swivel drive unit 11, and the swivel drive unit 1 is rotated.
1 is controlled by the control unit 3 together with the XY drive unit 4.

In the present embodiment, the intensity of the laser beam irradiated from the laser irradiation head 5 to the printed circuit board 8 is preset by inputting from the input / output unit 1, and the control unit 3 is also operated during the automatic operation of the laser reflow. It can be changed at any time by a command from.

In this embodiment, in order to set the optimum laser beam intensity for each mounting pad during reflow at the time of presetting, a printed circuit board 8 for testing is used to measure the temperature rise of each mounting pad due to laser beam irradiation. To do. In this measurement, laser reflow is performed by automatic operation according to the information stored in the storage unit 2. The laser irradiation head 5 is moved so that the irradiation point of the laser beam draws a locus along the row of the mounting pads on the printed circuit board 8. While moving at a constant speed, while the irradiation point passes over the mounting pad, a laser beam is irradiated with a preset constant intensity, and the elevated temperature of the heated point immediately after the irradiation is measured by the infrared temperature sensor 9. The temperature measured together with the XY coordinates of the measurement point is stored in the storage unit 2.

Next, the intensity of the laser beam is adjusted and set so that the mounting pads have the same elevated temperature based on the temperature of the measurement result. For example, for mounting pads whose measured temperature was within the target temperature range, set the same strength as that set at the time of measurement, and for mounting pads outside the target and temperature range, subtract the target temperature from the measured temperature. The value obtained by multiplying the calculated value by a proportional constant is subtracted from the previously set intensity, and is set as the adjusted laser beam intensity. The intensity of the laser beam set in this way is stored in the storage unit 3 in correspondence with the XY coordinates of the mounting pad.

After the above preset, the laser irradiation head 5 is moved by the automatic operation according to the information stored in the storage unit 2 and the laser beam having the optimum intensity set for each mounting pad is irradiated to the printed board 8 for the product. Laser reflow.

It should be noted that, as described above, the intensity of the laser beam is not determined by measuring the temperature only once, and the intensity of the laser beam after adjustment is different from that of the previous one as shown in FIG. The temperature rise of each mounting pad may be measured again by using, and temperature measurement and strength adjustment may be repeated until the temperature rise of all the mounting pads falls within the target range.

Instead of adjusting the intensity of the laser beam, the moving speed of the laser irradiation head 5 may be adjusted for each mounting pad. That is, the laser irradiation head 5 is moved at a higher speed for a mounting pad whose measured temperature on the test printed circuit board is too high, and is moved at a lower speed for a mounting pad whose temperature is too low.

In this embodiment, the infrared temperature sensor 9
Was rotated around the laser irradiation head 5, but the laser irradiation head was ± X to perform the solder reflow.
Direction and ± Y direction only,
4 around the laser irradiation head in the ± X and ± Y directions
If four infrared temperature sensors are installed at the location and one of the infrared temperature sensors is selected according to the moving direction of the laser irradiation head to measure the temperature of the point immediately after moving the laser beam irradiation point, the infrared temperature sensor can be used. No need to turn.

The intensity of the adjusted laser beam or the moving speed of the laser irradiation head 5 is measured on the basis of the temperature measured by the infrared temperature sensor 9 so that the controller 3 mechanically calculates it according to a predetermined program. It is also possible to display the measurement result on the input / output unit 1, a person looks at it and determines the adjusted value, and the adjusted value is input / output unit 1
Alternatively, a person may intervene so that the data is input from and stored in the storage unit 2.

[0022]

As described above, in the laser reflow apparatus and method of the present invention, all the soldering points (each point on the moving locus of the laser beam irradiation point of the object) having different heat capacities are the same in the laser reflow. Since solder reflow can be performed under temperature conditions, heat damage due to insufficient heating,
Good soldering is possible without unmelted solder, and it is extremely effective in ensuring reliability.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a perspective view showing the relationship between the laser irradiation head 5, the infrared temperature sensor 9 and the printed circuit board 8 shown in FIG.

FIG. 3 is a flowchart showing a procedure for repeating temperature measurement by the infrared temperature sensor 9 in the embodiment of FIG.

FIG. 4 is a block diagram of a conventional laser reflow soldering device.

[Explanation of symbols]

 1 Input / output 2 Storage part 3 Control part 4 XY drive part 5 Laser irradiation head 6 Laser device 7 Laser drive part 8 Printed circuit board 9 Infrared temperature sensor 10 Temperature measurement part 11 Swiveling drive part 12 Pad 13 pattern

Claims (3)

[Claims] 1. A laser reflow apparatus for moving a laser irradiation head for irradiating a target object with a laser beam relative to the target object to reflow solder previously coated on the target object. A laser reflow apparatus comprising an infrared temperature sensor that moves with the head with respect to the target object and measures the temperature of a point immediately after the irradiation point of the laser beam on the target object moves. 2. A laser reflow method in which a laser beam irradiation point on an object is moved to reflow solder previously coated on the object, the irradiation of the laser beam having a constant intensity on the object to be tested. By radiating the laser beam at each point on the locus by measuring the temperature of the point immediately after the movement of the irradiation point on the test object while moving the point while drawing a locus at a constant speed. The increased temperature is measured, and the intensity of the laser beam is adjusted so that each point on the locus is heated to the target temperature based on the measured temperature, and then the same type of object as that for the test is used. The laser reflow method characterized in that the irradiation point is moved at the constant speed by the laser beam having the intensity adjusted for each of the locus points to draw the locus. 3. A laser reflow method in which a laser beam irradiation point on an object is moved to reflow solder previously coated on the object, wherein a laser beam having a constant intensity is applied on the object to be tested. Laser beam irradiation of each point on the trajectory by measuring the temperature of the irradiation point on the test object immediately after the irradiation point is moved while moving the irradiation point along a trajectory at a constant speed. Measured the temperature increased by, and adjust the moving speed of the irradiation point so as to heat up to the target temperature for each point on the locus based on this measured temperature, and then the same type of object as the one for the test. A laser reflow method, characterized in that an irradiation point of the laser beam of the constant intensity is moved on an object at each speed on the trajectory at an adjusted speed to draw the trajectory.