JP6902778B2 - Laser soldering method and laser soldering equipment - Google Patents

Description

The present invention relates to a laser-type soldering method for soldering using laser light and a laser-type soldering apparatus used for carrying out the method.

Conventionally, a technique of soldering a part (soldering point) to be soldered between a printed circuit board and an electronic component by using a laser beam has been known. For example, Patent Document 1 describes a laser oscillator for outputting a laser beam, an irradiation head for irradiating a soldering point with a laser beam output from the laser oscillator, and a solder supply for supplying linear solder to the soldering point. A laser soldering apparatus having an apparatus and a controller for controlling the output of a laser oscillator is disclosed. This laser-type soldering device heats the soldering point by outputting a laser beam of intensity corresponding to the control signal from the controller from the laser oscillator, and at the same time, the linear solder supplied to the soldering point is the laser. It is melted by light and soldered.

At this time, the laser soldering apparatus is provided with a non-contact temperature sensor (radiation thermometer) that measures the temperature by infrared rays, and the radiation thermometer receives infrared rays radiated from the soldering point. Then, the temperature of the soldering point is measured in real time from the amount of infrared rays received, and based on the measured temperature, the output of the laser beam is output so that the temperature of the soldering point is always the optimum temperature (target temperature). Increase / decrease control.

By the way, when measuring the temperature of a soldering point with the radiation thermometer, the emissivity of infrared rays at the soldering point is set in advance in the controller, and the temperature is measured based on the emissivity. However, the emissivity of an object has a unique value for each material, and the emissivity differs depending on the surface condition of the object. Therefore, when the soldering point contains a plurality of metals, the emissivity of any metal should be set. It is very difficult to select the metal, and if the selection is incorrect, accurate temperature measurement cannot be performed, so that the output of the laser beam cannot be controlled accurately.

For example, when the soldering points are a terminal formed on a printed circuit board and a lead of an electronic component, both are formed of different metal materials (for example, copper, silver, gold, tin, etc.) and are mutually formed. Since the radiation rates are different, it is necessary to set the radiation rate of one of the metal materials, but even if one of the radiation rates is set, the positions of the terminals and leads are still in the plurality of soldering points. If there is any deviation, the object to be measured by the radiation thermometer changes from the terminal to the lead or from the lead to the terminal at the soldering point, which tends to cause a measurement error. Further, when linear solder is supplied to the soldering point and the linear solder is melted by the laser beam and diffused to the soldering point, the terminal or lead is covered with the diffused solder, so that the emissivity thermometer at that point. Since the object to be measured is changed to solder and the emissivity of the solder containing tin as a main component is different from the emissivity of the terminals and leads, the measurement temperature varies. Even if the emissivity is set to tin, the flux vaporized from the solder covers the soldering points, which also makes the measured temperature liable to vary.

In this way, in the past, the temperature of the soldering point was measured in real time with a radiation thermometer, and the output of the laser beam was controlled so that the measured temperature reached the target temperature. Since variations occur, it is difficult to control the output of the laser beam with high accuracy according to the target temperature, and there are many cases where solder defects occur because the soldering points are not heated to an appropriate temperature.

Japanese Unexamined Patent Publication No. 2010-26093

The present invention has been made in view of the above circumstances, and it is possible to accurately control the output of the laser beam so that the soldering point is heated to the target temperature, thereby performing high-quality soldering. The technical issue is to be able to do it.

In order to solve the above problems, the present invention includes a first step of irradiating a laser beam to preheat the soldering point, and a second step of melting the supplied solder with the laser beam and diffusing it to the soldering point. In a laser-type soldering method including a third step of post-heating the solder diffused to the soldering point with a laser beam, the soldering points are described for the first, second, and third steps before soldering. Based on the laser beam output and irradiation time required to heat to the target temperature, which is the preferred temperature for soldering, a control waveform for controlling the laser beam output and irradiation time is set, and a control waveform is set. wherein the target temperature is set from the higher-rather and first step constant over a third step size of the upper limit temperature, when performing soldering the first, along a second, a third step, the laser beam The output and irradiation time of the laser are controlled based on the control waveform, and the temperature of the soldering point is measured by a radiation thermometer and compared with the upper limit temperature. If the measured temperature is lower than the upper limit temperature, the waveform control is performed as it is. When the measurement temperature exceeds the upper limit temperature, the waveform control is released to reduce the output of the laser beam.

In the present invention, when the measured temperature exceeds the upper limit temperature during any of the first to third steps, the control of reducing the output of the laser beam is continued until the step is completed, and in the next step. The control of the laser light may be returned to the waveform control, or when the measurement temperature falls below the upper limit temperature due to the control of reducing the output of the laser light, the control of the laser light is returned to the waveform control when the temperature falls below the upper limit temperature. It may be that.

Further, in order to solve the above problems, according to the present invention, a laser oscillator that outputs a laser beam, an irradiation head that irradiates a laser beam from the laser oscillator toward a soldering point, and a temperature of the soldering point. the has a radiation thermometer for measuring a solder supply apparatus that supplies solder to the soldering point, and a control device for controlling according to a control program of the entire soldering apparatus, wherein the control device, soldering the soldering point preferred with output and irradiation time of the laser beam required to heat the target temperature is a temperature is input as the control waveform when, with the upper limit temperature of the target temperature higher rather and more certain size has not been entered At the time of soldering, the laser beam is waveform-controlled based on the output and irradiation time set by the control waveform, and the temperature of the soldering point measured by the radiation thermometer is compared with the upper limit temperature for measurement. When the temperature is lower than the upper limit temperature, the laser beam is controlled in waveform as it is, and when the measurement temperature exceeds the upper limit temperature, the waveform control is canceled and the output of the laser beam is reduced. A laser type soldering apparatus is provided.

In the present invention, the output of the laser beam and the irradiation time are controlled according to a preset control waveform, so that the output of the laser beam is accurately controlled so that the soldering point is heated to the target temperature. , It enables high quality soldering. In addition, the upper limit temperature is set, and when the temperature measured by the radiation thermometer exceeds this upper limit temperature, the waveform control is canceled and the temperature control that reduces the output of the laser beam is performed, so the soldering point It is possible to prevent damage to the board and electronic components, defective solder, etc. due to an abnormal rise in the temperature of the

It is a schematic diagram which shows the 1st Embodiment of the laser type soldering apparatus which concerns on this invention. (A) is a plan view of the soldering point, and (b) is a cross-sectional view of the same. (A) is a cross-sectional view showing the first step of soldering, (b) is a cross-sectional view showing the second step, and (c) is a cross-sectional view showing the third step. It is a diagram which shows the control waveform which controls a laser beam. It is a diagram showing the relationship between the output and irradiation time of the laser beam at the time of soldering, the temperature measured by the radiation thermometer, and the upper limit temperature, and is a control example when the measurement temperature is lower than the upper limit temperature. FIG. 5 is a control example in the same diagram as in FIG. 5 when the measured temperature exceeds the upper limit temperature. It is a schematic diagram which shows the 2nd Embodiment of the laser type soldering apparatus which concerns on this invention.

Hereinafter, the laser soldering method and the laser soldering apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a first embodiment of a soldering device 1. In this soldering device 1, a laser oscillator 2 that outputs a laser beam B and a laser beam B output from the laser oscillator 2 are printed on a printed substrate. An irradiation head 3 that irradiates the soldering point P on the 20 in a condensed state, a laser controller 4 for controlling the laser oscillator 2, and a solder supply for supplying the linear solder 15 to the soldering point P. According to the device 5, the radiation thermometer 6 that receives infrared rays (radiated infrared rays) radiated from the soldering point P and measures the temperature of the point P in a non-contact manner, and the entire soldering device 1 according to a set program. It has a control device 7 that automatically controls.

As shown in FIGS. 2A and 2B, the soldering point P is an annular terminal 21 formed on the printed circuit board 20 and a lead 22 extending from the electronic component 23, and the lead 22 is a lead 22 extending from the electronic component 23. , It is inserted into the terminal 21 from the bottom upward.

The irradiation head 3 has a substantially cylindrical outer shape, and a first optical fiber 8 communicating with the laser oscillator 2 is connected to a side surface thereof, and a laser beam B output from the laser oscillator 2 transmits the optical fiber 8. It is configured to pass through and be guided to the inside of the irradiation head 3. Then, inside the irradiation head 3, optical components (illustrated) such as a semitransparent mirror that changes the direction of the introduced laser light B and an optical lens that condenses the laser light B to a predetermined diameter at a soldering point P. Omitted) is built-in. Further, an irradiation port 3a is provided at the tip of the irradiation head 3 facing the soldering point P, and the laser beam B passing through the optical component is directed from the irradiation port 3a toward the soldering point P. It is designed to be irradiated.

Further, a second optical fiber 12 leading to the radiation thermometer 6 is connected to a position on the side surface of the irradiation head 3 different from the portion to which the first optical fiber 8 is connected, from the soldering point P. The radiated infrared rays are received by the radiation thermometer 6 through the second optical fiber 12. That is, the radiated infrared rays from the soldering point reach the inside of the irradiation head 3 through the irradiation unit 3a of the irradiation head 3, pass through the optical component through which the laser beam B passes, and the base end of the irradiation head 3. After advancing to the side, it is guided into the second optical fiber 12 through an optical unit 13 composed of a lens, a semitransparent mirror, or the like, and is transmitted to the radiation thermometer 6 via the optical fiber 12.

Then, in the radiation thermometer 6, the temperature H1 of the soldering point P is obtained based on the amount of energy of the received radiated infrared rays, and the measurement temperature signal (temperature data) proportional to the obtained measurement temperature H1 is the laser controller 4. It is sent to the control device 7 via. The temperature data obtained by the radiation thermometer 6 may be sent to the control device 7 as it is without passing through the laser controller 4.

Further, a CCD camera 10 is attached to the base end portion of the irradiation head 3 so that the laser beam B and the optical axis L are aligned with each other, and the CCD camera 10 can image the soldering point P through the irradiation port 3a. It has become like. The image of the soldering point P captured by the CCD camera 10 is displayed on the monitor 11 via the control device 7, and before soldering, the image displayed on the monitor 11 is viewed with respect to the soldering point P. It can be used to adjust the aim of the laser beam B, and the state of the soldering point P can be observed during the soldering operation.

The solder supply device 5 is for feeding, for example, the required amount of the linear solder 15 wound around the pulley toward the soldering point P. The solder supply device 5 has a solder guide 16 arranged near the soldering point P, and receives a control command such as a supply timing and a supply amount of the solder 15 from the control device 7 during the soldering operation. Solder 15 is supplied from the solder guide 16 to the soldering point P according to the control command. Then, the laser oscillator 2 that receives the oscillation control command from the laser controller 4 outputs the laser light B at a predetermined output and irradiation time, and supplies the solder 15 to the laser light B, so that the solder 15 is generated by the laser light B. It is configured to be heated and melted for soldering.

Next, a method of soldering the soldering point P using the soldering device 1 having the above configuration will be described.

As shown in FIG. 3A, the soldering steps carried out in the present invention include the first step S1 in which the soldering point P is irradiated with laser light B to preheat the soldering point P, and FIG. As shown in (b), the linear solder 15 is supplied from the solder supply device 5 to the soldering point P, and the linear solder 15 is heated and melted by the laser beam B and diffused to the soldering point P ( The second step S2 to be wetted) and the solder 15 diffused to the soldering point P are post-heated by the laser beam B as shown in FIG. 3C so that the metal processed product required for soldering is produced. It is divided into three steps, the third step S3 to finish the soldering.

In the present invention, in order to control the output (W) and irradiation time (seconds) of the laser beam B with respect to the control device 7 as a preliminary step prior to performing the soldering in the first to third steps. The setting of the control waveform C for inputting the control waveform C (see FIG. 4), the setting of the measurement target for measuring the temperature with the radiation thermometer 6, the setting of the emissivity according to the material of the measurement target, and the like. Will be done. In the present embodiment, since the temperature measurement target by the radiation thermometer 6 is set to the solder 15, the emissivity is set to tin, which is the main component of the solder 15. Further, when the upper limit temperature H2 (see FIGS. 5 and 6) of the soldering point P is set in the control device 7, and the temperature H1 measured by the radiation thermometer 6 exceeds the upper limit temperature H2 (see FIG. 6 and FIG. 6). (See FIG. 6), a control program is set so as to reduce the output of the laser beam B apart from the control by the control waveform C.

The control waveform C is, each first to third step, the heating target temperature of the soldering point P, the output and irradiation time of the laser beam B required to heat the soldering point P of this to the target temperature It is decided by asking for.

The heating target temperature is set to a preferable target temperature based on numerical simulations performed in advance, past empirical rules, etc., depending on the material, shape, size, surface condition, etc. of the terminals 21 and leads 22 forming the soldering point P. It is required in advance. For example, when the soldering point P is composed of the normal terminals 21 and the leads 22 as in the present embodiment, the preferable heating target temperature in the first step S1 before the solder 15 is supplied is 150-250 ° C. In the second step S2 of melting and diffusing the supplied solder 15, the soldering point P including the solder 15 needs to be kept at 200-300 ° C. Therefore, the preferable heating target temperature is 200-300 ° C. Further, in the third step S3 in which the soldering point P is post-heated, it is necessary to keep the soldering point P at 250-300 ° C. so that the metal compound necessary for soldering is generated, which is a preferable heating target. The temperature is 250-300 ° C.

Then, for each of the first to third steps, the output and irradiation time of the laser beam B required to heat the soldering point P to the heating target temperature are obtained by experiments, calculations, etc., and are shown in FIG. As described above, the control waveform C for controlling the output of the laser beam B and the irradiation time is determined throughout the first to third steps, and this control waveform C is input to the control device 7.
In the example shown in FIG. 4, in the first step S1, the laser beam B having an output of 20 W is irradiated for 0.3 seconds, and in the next second step S2, the laser beam having an output of 35 W is irradiated for 0.5 seconds, and the final step. In the third step S3, a laser beam having an output of 30 W is set to be irradiated for 0.3 seconds.

Then, as described above, the setting of the control waveform C and the like for the control device 7 is completed, the irradiation position of the laser beam B with respect to the soldering point P by teaching, the order in which the plurality of soldering points P are soldered, and the like. After the start button is pressed, laser light is applied to each of the plurality of soldering points P based on the control waveform C for each of the first step S1, the second step S2, and the third step S3. Soldering is performed by controlling the output of B and the irradiation time. Further, at the same time as the start of soldering, the temperature measurement of the soldering point P by the radiation thermometer 6 is also started, and the measurement temperature H1 is compared with the upper limit temperature H2. The upper limit temperature H2 is set to a temperature higher than the maximum value of the target temperature.

5 and 6 show the relationship between the output and irradiation time of the laser beam B in the case of soldering, the temperature H1 measured by the radiation thermometer 6, and the upper limit temperature H2. Of these, FIG. 5 is a control example when the measurement temperature H1 is lower than the upper limit temperature H2, and FIG. 6 is a control example when the measurement temperature H1 exceeds the upper limit temperature H2 for some reason.

In the control example of FIG. 5, when the laser beam B having an output of 20 W is irradiated in the first step S1 (FIG. 3 (a)), the measured temperature H1 of the soldering point P including the terminal 21 and the lead 22 gradually rises. Then, immediately before the end of the first step S1, the temperature rises to about 220 ° C., which exceeds the target temperature of 150-200 ° C.

When the process proceeds to the second step S2 (FIG. 3B), the output of the laser light B rises to 35 W, and the laser light B is irradiated for 0.5 seconds while maintaining the 35 W. Further, substantially at the same time as the start of the second step S2, a fixed amount of the linear solder 15 is supplied to the soldering point P, and the supplied solder 15 is melted by the laser beam B and diffused over the entire soldering point P. To do. At this time, since the thermal energy of the laser beam B is consumed to melt the solder 15, the measurement temperature H1 at the soldering point P temporarily drops a little, but immediately after that, it picks up and continues to rise, and the second step. Near the end of S2, the temperature reaches about 320 ° C, which exceeds the target temperature of 200-300 ° C, and the temperature is settled.

Subsequently, when the process proceeds to the third step S3 (FIG. 3 (c)), the output of the laser beam B drops to 30 W, and the laser beam B is irradiated for 0.3 seconds at 30 W to perform post-heating. In the meantime, the metalwork required for soldering is produced. At this time, the measurement temperature H1 is slightly lower than that in the second step S2, but is maintained at about 290 ° C., which satisfies the target temperature of 250-300 ° C.

Then, since the output of the laser beam B becomes zero at the end of the third step S3, the soldering point P is naturally cooled, whereby the measurement temperature H1 drops sharply and finally settles at a constant temperature.
In the actual soldering step, when the third step S3 is completed, the irradiation of the laser beam B is stopped, the temperature measurement by the radiation thermometer 6 is also stopped, and the irradiation head 3 moves to the next soldering point P. Then, when the same operation is performed, the soldering point P is soldered, and the same operation is repeated for all the soldering points P.

On the other hand, the control example of FIG. 6 is a case where the measurement temperature H1 rises for some reason and exceeds the upper limit temperature H2 in the middle of the second step S2. At this time, when the measurement temperature H1 exceeds the upper limit temperature H2 (t1), the control (waveform control) of the output of the laser beam B by the control waveform C is canceled, and the laser beam B is irrelevant to the control waveform C. Control (temperature control) is performed to reduce the output of the laser. The amount of reduction in the output of the laser beam B at this time is usually 10 to 20% of the output (35W) set in the control waveform C, and in the illustrated embodiment, the reduction is about 6W. Therefore, the output of the laser beam B is maintained at around 29 W. As a result, the heating temperature of the soldering point P is lowered, so that the measured temperature H1 is also lowered.

Even if the measurement temperature H1 falls below the upper limit temperature H2 during the second step S2, the state of reduced output of the laser beam B is maintained until the second step S2 is completed, and the laser is maintained from the third step S3. The control of the light B is returned to the waveform control. However, when the measurement temperature H1 falls below the upper limit temperature H2, the output control of the laser beam B may be returned from the temperature control to the waveform control.
Further, if the measured temperature H1 does not fall below the upper limit temperature H2 during the second step S2 and falls below the upper limit temperature H2 after shifting to the third step S3, the control of the laser beam B is performed when the temperature falls below the upper limit temperature H2. The temperature control may be returned to the waveform control, but the temperature control may be maintained until the third step S3 is completed.

By performing such control, it is possible to prevent damage to the substrate and electronic components, defective solder, and the like due to an abnormal rise in the measured temperature H1 at the soldering point P.

The abnormal rise in the measurement temperature H1 is not limited to the second step S2, but may occur during the first step S1 or the third step S3. In that case, the laser beam B is described above. The temperature is controlled to reduce the output of the solder, but the emissivity, which is the reference for temperature measurement by the radiation thermometer 6, is set to the emissivity of tin, which is the main component of the solder 15, so that the accuracy is improved. Therefore, it is desirable that the temperature control is performed for the second step S2 and the third step S3 after the solder 15 is supplied.

As described in detail above, according to the present invention, the output and irradiation time of the laser beam B to be irradiated to the soldering point P at the time of soldering are the laser required to heat the soldering point P to the target temperature. Since the control is performed based on the control waveform C obtained from the output of the light B and the irradiation time, the soldering point P is accurately and reliably set to the target temperature during the first to third steps. It is possible to be affected by the variation of the measurement temperature H1 as in the conventional method of controlling the output of the laser beam B so that the measurement temperature H1 measured by the radiation thermometer 6 becomes the target temperature. Therefore, the output of the laser beam B can be controlled with high accuracy to maintain the target temperature at the soldering point P.

Moreover, in the present invention, the upper limit temperature H2 is set, and when the temperature H1 measured by the radiation thermometer 6 exceeds the upper limit temperature H2, the waveform control is canceled and the temperature control for lowering the output of the laser beam B is performed. Therefore, it is possible to prevent damage to the substrate and electronic components, defective solder, and the like due to an abnormal rise in the temperature of the soldering point P.

The soldering apparatus of the present invention is not limited to the above-described embodiment, and various design changes can be made without departing from the scope of the claims.
For example, in the example shown in FIG. 1, the radiated infrared rays radiated from the soldering point P are transmitted from the inside of the irradiation head 3 to the radiation thermometer 6 via the second optical fiber 12, but FIG. 7 shows. As in the second embodiment shown, it is also possible to directly receive the infrared rays emitted from the soldering point P by the light receiving portion 6a of the radiation thermometer 6 and measure the temperature of the soldering point P. ..
Since the configurations other than the above in the second embodiment are substantially the same as those in the first embodiment, the same reference numerals as those in the case of the first embodiment are attached to the main same components of both, and the description thereof will be described. Is omitted.

Further, the control waveform C of the laser beam B and the upper limit temperature H2 shown in the above embodiment are merely examples. For example, the material and shape of the terminal 21 and the lead 22 forming the soldering point P, and the solder material. It is also possible to change as appropriate according to various conditions such as. The control waveform C shown as an example in FIG. 4 has a flat linear shape so as to output the laser beam B at a constant intensity in each of the first to third steps. For example, the laser beam B is formed. The output of the above may be an inclined linear or curved waveform that changes with time, or may be a waveform that is a combination of these straight lines and curves.

1 Soldering device 2 Laser oscillator 3 Irradiation head 5 Soldering supply device 6 Radiation thermometer 7 Control device 15 Solder B Laser light C Control waveform H1 Measurement temperature H2 Upper limit temperature P Soldering point

Claims (4)

The first step of irradiating the soldering point with laser light to preheat the soldering point, the second step of melting the supplied solder with the laser beam and diffusing it to the soldering point, and the second step of diffusing the solder diffused to the soldering point with laser light. In a laser soldering method having a third step of post-heating,
Before soldering, for the first, second, and third steps, the output and irradiation time of the laser beam required to heat the soldering point to the target temperature, which is the preferred temperature for soldering, based on, it sets the control waveform for controlling the output and irradiation time of the laser beam, to set the fixed size of the upper limit temperature for the third step from the high rather and first step than the target temperature,
When soldering is performed according to the first, second, and third steps, the output and irradiation time of the laser beam are waveform-controlled based on the control waveform, and the temperature of the soldering point is measured by a radiation thermometer. When the measured temperature is lower than the upper limit temperature, the waveform control is performed as it is, and when the measurement temperature exceeds the upper limit temperature, the waveform control is canceled and the output of the laser beam is reduced. Control to make
A laser soldering method characterized by this. When the measured temperature exceeds the upper limit temperature during any of the first to third steps, the control of reducing the output of the laser beam is continued until the step is completed, and the control of the laser beam is performed in the next step. The laser soldering method according to claim 1, wherein the method returns to waveform control. The laser soldering method according to claim 1, wherein when the measurement temperature falls below the upper limit temperature due to the control of reducing the output of the laser light, the control of the laser light is returned to the waveform control when the temperature falls below the upper limit temperature. .. A laser oscillator that outputs laser light, an irradiation head that irradiates the laser light from the laser oscillator toward the soldering point, a radiation thermometer that measures the temperature of the soldering point, and solder at the soldering point. It has a solder supply device to supply and a control device that controls the entire soldering device according to a control program.
The control device, the output and irradiation time of the laser beam required to heat the target temperature is the preferred temperature when soldering the soldering point is input as a control waveform, higher rather and than the target temperature constant The upper limit temperature of the magnitude of is input, and at the time of soldering, the laser beam is waveform-controlled based on the output and irradiation time set by the control waveform, and the soldering point measured by a radiation thermometer. When the measured temperature is lower than the upper limit temperature, the waveform control of the laser beam is performed as it is, and when the measurement temperature exceeds the upper limit temperature, the waveform control is canceled and the laser beam is output. Is configured to provide control to reduce the temperature,
A laser-type soldering device that is characterized by this.

Images