JP2024048115A - Laser soldering equipment - Google Patents

Abstract

[Problem] To provide a simple, low-power laser soldering method and device that can efficiently solder a board and an electronic component while reliably preventing the board from being burned by laser light. [Solution] In a laser soldering method in which a joint 34 between an electrode land 32 of a board 30 and a terminal 33 of an electronic component 31 mounted on the board 30 is soldered by irradiating the board with laser light 15, 18, the joint 34 is heated to a soldering temperature by irradiating the front and back surfaces of the board 30 with the laser light 15 and 18, and soldering is performed by melting solder 21 that has been supplied to the joint 34 in advance or that is supplied in conjunction with heating. [Selected Figure] Figure 2

Description

The present invention relates to a laser soldering method and device that uses laser light to solder the joints between the electrode lands of a substrate and the terminals of electronic components mounted on the substrate.

2. Description of the Related Art A laser soldering apparatus that solders joints between electrode lands of a substrate and terminals of electronic components mounted on the substrate by irradiating the substrate with laser light is publicly known, as disclosed in Japanese Patent Application Laid-Open No. 2003-233996.
When a conventional laser soldering device is used to solder a joint 54 between an annular electrode land 51 formed on a substrate 50 and a pin-shaped terminal 53 of an electronic component 52 mounted on the substrate 50, as shown in FIG. 8, the joint 54 is irradiated with laser light 56 from an irradiation head 55 to heat the electrode land 51 and the terminal 53, and linear solder 58 is supplied from a solder supply nozzle 57 to the heated electrode land 51 or terminal 53 to melt 59, thereby soldering the joint 54.

However, since the electrode land 51 and the terminal 53 are made of different metal materials (for example, the electrode land 51 is made of tin-plated copper, and the terminal 53 is made of gold-plated copper), they have different absorption rates of the laser light 56 and cannot be heated to the target temperature simultaneously. For this reason, if the intensity and irradiation time of the laser light are set to raise the temperature of the terminal 53, which has a low absorption rate of the laser light 56, to the target temperature, the electrode land 51 and the substrate 50 will become overheated, and in some cases the electrode land 51 and the substrate 50 may even be burned.

When soldering the electrode lands of a substrate to the terminals of an electronic component mounted on the substrate by the reflow method, a reflow furnace is used, the substrate is placed in the furnace, and the entire furnace is heated by hot air or a far-infrared heater or the like to heat the entire substrate, and the solder material interposed between the electrode lands and the terminals as solder cream or solder balls is melted to solder them. However, this method requires not only very large equipment, but also poses problems such as complicated temperature control in the reflow path and very high power consumption.

JP 2001-198670 A

The technical objective of the present invention is to provide a simple, low-power laser soldering method and device that can efficiently solder a board and electronic components while reliably preventing the board from being burned by laser light.

To solve the above problems, the present invention provides a laser soldering method for soldering a joint between an electrode land of a substrate and a terminal of an electronic component mounted on the substrate by irradiating the electrode land with a laser beam, characterized in that the joint is heated to a soldering temperature by irradiating the front and back surfaces of the substrate with a laser beam, and soldering is performed by melting solder that is supplied to the joint in advance or supplied with heating.

In the present invention, the first laser light irradiated to the front surface of the board is a laser light for main heating that heats the joint to the soldering temperature, and the second laser light irradiated to the back surface of the board is a laser light for preheating that preliminarily heats the joint to a preheat temperature lower than the soldering temperature, and the first laser and the second laser light are irradiated simultaneously or with a time lag between them, and then the second laser light is stopped before the temperature of the joint reaches the soldering temperature, and the first laser is irradiated until the temperature of the joint reaches the soldering temperature.
In this case, it is desirable that the irradiation area of the second laser light is equal to or larger than the irradiation area of the first laser light.

In one embodiment of the present invention, the joint comprises an electrode land formed on the surface of the substrate and a terminal on the underside of an electronic component mounted on the surface of the substrate, with a solder material interposed in advance between the electrode land and the terminal, and the joint is preheated by the second laser light through the substrate and is actually heated by the first laser light through the electronic component.

According to another embodiment of the present invention, the joint comprises an annular electrode land formed on the substrate and a pin-shaped terminal of an electronic component mounted on the back surface of the substrate, the terminal being inserted into a through hole of the electrode land, and the first laser light directly heats the joint from the front surface side of the substrate, and the second laser light directly heats the joint from the back surface side of the substrate or indirectly heats the joint via the electronic component.

The present invention also provides a laser soldering device that solders the joint between the electrode land of a substrate and the terminal of an electronic component mounted on the substrate by irradiating the substrate with laser light, the laser soldering device being characterized in having a first irradiation head that irradiates the front surface of the substrate with a first laser light, and a second irradiation head that irradiates the rear surface of the substrate with a second laser light.

In the present invention, the first laser light is a laser light for main heating that heats the joint to the soldering temperature, and the second laser light is a laser light for preheating that preliminarily heats the joint to a preheat temperature lower than the soldering temperature, and the first laser and the second laser light are irradiated simultaneously or with a time lag, and then the second laser light is stopped before the temperature of the joint reaches the soldering temperature, and the first laser is irradiated until the temperature of the joint reaches the soldering temperature.
It is desirable that the irradiation area of the second laser light be equal to or larger than the irradiation area of the first laser light.

In one embodiment of the present invention, the joint comprises an electrode land formed on the surface of the substrate and a terminal on the underside of an electronic component mounted on the surface of the substrate, with a solder material interposed in advance between the electrode land and the terminal, and the joint is preheated by the second laser light through the substrate and is actually heated by the first laser light through the electronic component.

In another embodiment of the present invention, the joint comprises an annular electrode land formed on the substrate and a pin-shaped terminal of an electronic component mounted on the back surface of the substrate, the terminal being inserted into a through hole of the electrode land from the back surface of the substrate, the first irradiation head irradiates the first laser light directly onto the joint, and the second irradiation head irradiates the second laser light onto the joint on the back surface of the substrate and an area surrounding the joint.

In the present invention, it is preferable that the first irradiation head has a solder supply nozzle for supplying linear solder to the joint and a non-contact thermometer for measuring the temperature of the joint, and the second irradiation head has a non-contact thermometer for measuring the temperature of the joint.

According to the present invention, by irradiating the joints between the electrode lands of the substrate and the terminals of the electronic components mounted on the substrate with laser light from both the front and back sides of the substrate to heat them, it is possible to heat the substrate more efficiently and quickly than when laser light is irradiated from only one side of the substrate, and it is also possible to prevent burning of the substrate, electronic components, etc., compared to when high-power laser light is irradiated in a concentrated manner from only one side of the substrate.

1 is a front view showing a schematic diagram of a laser soldering apparatus according to the present invention; 2 is an enlarged view of a main portion when a substrate and an electronic component are soldered by a reflow method using the laser soldering apparatus of FIG. 1 . FIG. 3 is a plan view of a main portion of the substrate in FIG. 2 . FIG. 3 is a bottom view of a main part of the substrate in FIG. 2 . 1 is an enlarged view of a main portion when multiple electronic components are soldered to a substrate at the same time. 2 is an enlarged cross-sectional view of a main portion when a substrate and an electronic component are soldered by the laser soldering apparatus of FIG. 1 using a solder supply system; FIG. 7 is a cross-sectional view of a main part showing a state of a joint after soldering in FIG. 6. FIG. 1 is an enlarged cross-sectional view of a main portion for explaining a conventional soldering method.

One embodiment of the laser soldering device according to the present invention will be described in detail below with reference to the drawings. The soldering device 1 shown in FIG. 1 is configured to solder a board 30 and an electronic component 31 mounted on the board 30 by irradiating laser light from both the front and back sides of the board 30, and as described below, can be used for both reflow soldering and solder supply soldering, in which linear solder is supplied for soldering.

In FIG. 1, the body of the soldering device 1 has a base 2, left and right side walls 3a, 3b that rise vertically from the left and right side ends of the base 2, a top plate 4 that spans between the upper ends of the left and right side walls 3a, 3b, and an intermediate wall 5 that is provided near the middle of the height direction of the left and right side walls 3a, 3b.

The intermediate wall portion 5 is formed with a board support portion 6 for supporting the board 30 to be soldered, and a first slide member 7 is attached to the top plate portion 4 so as to be displaceable in the left-right direction (X direction) and the front-back direction (Y direction) of the figure along a guide (not shown) formed on the top plate portion 4, and a first irradiation head 8 for irradiating the front side of the board 30 with a first laser beam 15 is attached to the first slide member 7 so as to be displaceable in the up-down direction (Z direction) of the figure by a first support arm 9.

The second slide member 10 is attached to the base portion 2 so as to be displaceable in the left-right direction (X direction) and the front-back direction (Y direction) of the figure along a guide (not shown) formed on the base portion 2, and a second irradiation head 11 for irradiating the back side of the substrate 30 with a second laser beam 18 is attached to the second slide member 10 so as to be displaceable in the up-down direction (Z direction) of the figure by a second support arm 12.

The first optical fiber 14 from the first laser oscillator 13 is connected to the first slide member 7, and the first optical fiber 14 is connected to the first irradiation head 8 via an optical fiber (not shown) provided in the first slide member 7 and the first support arm 9. The laser light from the first laser oscillator 13 is introduced from the first optical fiber 14 through the first slide member 7 and the first support arm 9 to the first irradiation head 8, and is irradiated from the first irradiation head 8 as the first laser light 15 in a state where the irradiation shape and irradiation area are adjusted to match the irradiation target by an optical mechanism built into the first irradiation head 8.

On the other hand, a second optical fiber 17 from a second laser oscillator 16 is connected to the second slide member 10, and the second optical fiber 17 is connected to the second irradiation head 11 via an optical fiber (not shown) provided in the second slide member 10 and the second support arm 12. The laser light from the second laser oscillator 16 is introduced from the second optical fiber 17 through the second slide member 10 and the second support arm 12 to the second irradiation head 11, and is irradiated as the second laser light 18 from the second irradiation head 11 in a state where the irradiation shape and irradiation area are adjusted to match the irradiation target by an optical mechanism built into the second irradiation head 11.

The first laser light 15 irradiated from the first irradiation head 8 to the surface of the substrate 30 is a laser light for main heating that heats the joint 34 between the substrate 30 and the electronic component 31 to the soldering temperature (e.g., 300-350°C), and the second laser light 18 irradiated from the second irradiation head 11 to the back surface of the substrate 30 is a laser light for preheating that preheats the substrate 30 to a preheating temperature (e.g., 240-260°C) lower than the soldering temperature. By preheating the substrate 30 from the back side with this second laser light 18, it is possible to prevent the substrate 30 from absorbing and diffusing heat when the first laser light 15 is irradiated to the surface of the substrate 30, and to efficiently heat the joint 34 from both the front and back sides of the substrate 30, thereby accelerating the temperature rise of the joint 34. It is also possible to prevent the substrate 30 and electronic components 31 from burning when high-power laser light is irradiated intensively only from the front side of the substrate 30.

The first laser light 15 and the second laser light 18 may have the same wavelength and output, but the output of the second laser light 18 may be slightly lower than the output of the first laser light 15 to prevent burning of the substrate 30.

The first irradiation head 8 and the second irradiation head 11 are also fitted with a non-contact thermometer 19, such as a radiation thermometer or a thermograph, which can measure the temperature of the substrate 30, the electronic component 31, the joint 34, etc. The thermometer 19 is connected to a control device 20 together with the first laser oscillator 13 and the second laser oscillator 16, and the control device 20 controls the first laser oscillator 13 and the second laser oscillator 16 based on the measurement signal from the thermometer 19, thereby controlling the intensity of the laser light from the first irradiation head 8 and the second irradiation head 11, and the start and stop of the irradiation.

Furthermore, the first irradiation head 8 is provided with a solder supply nozzle 22 for supplying linear solder 21 to the joint 34 when soldering by the solder supply method is performed, and the solder supply nozzle 22 is connected to a solder supply device 24 via a solder feed tube 23. The solder supply device 24 and the solder supply nozzle 22 are not used when soldering by the reflow method. The first irradiation head 8 is also provided with a lamp for illuminating the part to be soldered with visible light, but the illustration thereof is omitted. In contrast, the second irradiation head 11 is not provided with the solder supply nozzle 22 and lamp, but it can be provided with the solder supply nozzle 22 and lamp as with the first irradiation head 8, in which case soldering by the solder supply method can be performed on the joint on the back side of the board 30.

The substrate 30 is a substrate 30 for performing reflow soldering, and as shown in FIG. 2, has a joint 34 consisting of an electrode land 32 formed on the surface of the substrate 30 and a terminal 33 on the underside of an electronic component 31 such as a semiconductor package mounted on the surface of the substrate 30, and this joint 34 is to be soldered. For this reason, a solder material is interposed in advance between the electrode land 32 and the terminal 33 of the electronic component 31. In detail, cream solder is applied to the surface of the electrode land 32, and a solder ball 35 is attached to the terminal 33 of the electronic component 31.

When the board 30 is soldered by the soldering laser soldering device 1 having the above configuration, as shown in Figures 2, 3, and 4, first, the second laser light 18 is irradiated from the second irradiation head 11 toward the part on the back side of the board 30 where the electronic component 31 is mounted, and then the first laser light 15 is irradiated from the first irradiation head 8 toward the electronic component 31 on the front side of the board 30 and the board surface around the electronic component 31. At this time, the area B (irradiation area) where the second laser light 18 is irradiated on the back side of the board 30 is wider than the area A (irradiation area) where the first laser light 15 is irradiated on the front side of the board 30. By widening the irradiation area B of the second laser light 18 in this way and reducing the energy density, it is possible to prevent the board 30 and electronic components 31 from being burned due to irradiation of laser light from both the front and back sides.

In this case, the first laser light 15 and the second laser light 18 do not necessarily need to be irradiated concentrically, and the second laser light 18 may be irradiated eccentrically with respect to the first laser light 15. The irradiation shape of the first laser light 15 and the second laser light 18 can be formed into any shape, such as a circle, an ellipse, a ring, or a rectangle, according to the shapes of the electronic component 31 and the joint 34, etc. For example, the irradiation shape of the first laser light 15 can be rectangular according to the shape of the electronic component, and the irradiation shape of the second laser light 18 can be circular or elliptical, etc.

The timing for irradiating the first laser light 15 after irradiating the second laser light 18 is the timing when the temperature of the substrate 30 reaches, for example, about 150-160°C due to irradiation of the second laser light 18. The timing may be set by measuring the rear surface temperature of the substrate 30 with a thermometer 19 attached to the second irradiation head 11 and irradiating the first laser light 15 when the measured temperature reaches 150-160°C, but it is also possible to obtain data on the relationship between the irradiation time of the second laser light 18 and the temperature rise of the substrate 30 by performing experiments or simulations in advance, and based on that data, set the irradiation of the first laser light 15 after irradiating the second laser light 18 and after a time when the temperature of the substrate 30 reaches about 150-160°C.

In this way, by irradiating the substrate 30 with laser light from both sides, the joint 34 between the substrate 30 and the electronic component 31 is indirectly heated via the substrate 30 and the electronic component 31, and the temperature rises toward the soldering temperature. Then, when the temperature of the substrate 30 reaches the preheating temperature, the irradiation of the second laser light 18 is stopped and the preheating ends, and thereafter, only the first laser light 15 is irradiated onto the surface of the substrate 30. Then, when the temperature of the joint 34 reaches the soldering temperature, the solder material interposed between the electrode land 32 and the terminal 33 of the electronic component 31 melts, and the electronic component 31 is soldered to the substrate 30, and at the same time, the irradiation of the first laser light 15 is stopped.

In the above example, the second laser light 18 is irradiated before the first laser light 15, but the first laser light 15 and the second laser light 18 can be irradiated simultaneously, or the first laser light 15 can be irradiated first, and then the second laser light 18 can be irradiated after a slight time difference.
Moreover, the irradiation area A of the first laser beam 15 and the irradiation area B of the second laser beam 18 can be made the same size, and the energy density of the second laser beam 18 can be made equal to or greater than the energy density of the first laser beam 15 depending on the materials of the board and electronic components, etc. Thus, it is also possible to solder the electronic components mounted on the front side of the board by irradiation with the first laser beam 15, and solder the electronic components mounted on the back side of the board by irradiation with the second laser beam 15.

The example shown in FIG. 2 shows a case where one electronic component 31 is soldered to the substrate 30, but if multiple electronic components 31 are mounted on the substrate 30, multiple electronic components 31 can be soldered by performing the same process on each electronic component. Alternatively, as shown in FIG. 5, multiple electronic components 31 can be soldered to the substrate 30 simultaneously by irradiating an area including multiple electronic components 31 with the first laser light 15 and the second laser light 18.

When soldering of one board 30 is completed, the board 30 is removed from the board support section 6 and a new board is brought in and subjected to the same process.

Next, a case will be described in which soldering is performed by the solder supply method in which the linear solder 21 is supplied to the joint 34 by the laser soldering apparatus 1.
6, the joint 34 in this case is composed of an annular electrode land 32 formed on the substrate 30 and a pin-shaped terminal 33 of an electronic component 31 mounted on the back surface of the substrate 30, and the terminal 33 is inserted into a through hole 32a of the electrode land 32 from the back surface of the substrate 30. Therefore, the electrode land 32 is exposed on both the front and back surfaces of the substrate 30, a tip portion of the terminal 33 is exposed on the front surface side of the substrate 30, and a base end portion of the terminal 33 is exposed on the back surface side of the substrate 30.

When soldering the joint 34, as shown in FIG. 6, the first laser light 15 for main heating is irradiated from the first irradiation head 8 toward the electrode land 32 and the pin-shaped terminal 33 that constitute the joint 34 on the front surface of the substrate 30, and at the same time, the second laser light 18 for preheating is irradiated from the second irradiation head 11 to a wide area including the joint 34 on the rear surface of the substrate 30 and a part of the substrate 30 and the electronic component 31 around the joint 34.

As a result, the temperature of the joint 34 rises to the soldering temperature more quickly than when the laser light is irradiated only from the front side of the board 30. Then, when the temperature of the joint 34 reaches the preheating temperature, the irradiation of the second laser light 18 is stopped, and the solder supply nozzle 22 attached to the first irradiation head 8 supplies the linear solder 21 to the electrode land 32 or the terminal 33 of the heated joint 34 and melts it. As shown in FIG. 7, the molten solder 21a diffuses through the inside of the through hole 32a to the back side of the electrode land 32, soldering the joint 34. At the same time, the irradiation of the first laser light 15 is stopped, or the output of the first laser light 15 is gradually reduced, so that the joint 34 is gradually cooled.

In this case, since the temperature of the joint 34 rises very quickly, the supply of the linear solder 21 may be performed almost simultaneously with the irradiation of the first laser light 15 or slightly after the irradiation.

In the illustrated embodiment of the laser soldering device, the first irradiation head 8 and the second irradiation head 11 are each connected to an individual laser oscillator 13 or 16, but it is also possible to use a single laser oscillator, split one laser beam output from this single laser oscillator into two beams using a spectrometer, and supply the split laser beams to the first irradiation head 8 and the second irradiation head 11. In this case, the power distribution between the laser beam supplied to the first irradiation head 8 and the laser beam supplied to the second irradiation head 11 can be set to, for example, 50:50 or 60:40.

In addition, in the above embodiment, the first laser light 15 is used for main heating and the second laser light 18 is used for preheating, but both laser lights can be used for main heating. In this way, it becomes possible to solder the electronic components 31 mounted on the front side of the substrate 30 by irradiating the first laser light 15, and solder the electronic components 31 mounted on the back side of the substrate 30 by irradiating the second laser light 18.

In addition, in the illustrated embodiment, the board 30 is supported horizontally and the front and back surfaces of the board 30 are irradiated with laser light from above and below the board 30, but the board 30 can also be supported vertically and the front and back surfaces of the board 30 are irradiated with laser light from the left and right sides of the board. In this case, the laser soldering device has a structure that is, for example, the laser soldering device in FIG. 1 rotated 90 degrees, and a first irradiation head and a second irradiation head are disposed on both the left and right sides of the vertically oriented board.

REFERENCE SIGNS LIST 1 soldering device 8 first irradiation head 11 second irradiation head 15 first laser light 18 second laser light 19 thermometer 21 solder line 22 solder supply nozzle 30 substrate 31 electronic component 32a through hole 33 terminal 34 joint 35 solder ball

Claims (11)

A laser soldering method for soldering a joint between an electrode land of a substrate and a terminal of an electronic component mounted on the substrate by irradiating the electrode land with a laser beam, comprising:
The front and back surfaces of the substrate are irradiated with laser light, respectively, to heat the joints to a soldering temperature, and solder is melted by melting solder that is supplied to the joints in advance or is supplied with the heat.
A laser soldering method comprising the steps of: the first laser light irradiated onto the surface of the substrate is a laser light for main heating that heats the joint to the soldering temperature,
the second laser light irradiated to the rear surface of the substrate is a preheating laser light for preheating the joint to a preheating temperature lower than the soldering temperature,
The first laser and the second laser light are irradiated simultaneously or with a time lag therebetween, and then the second laser light is stopped before the temperature of the joint reaches the soldering temperature, and the first laser is irradiated until the temperature of the joint reaches the soldering temperature.
2. The laser soldering method according to claim 1, The laser soldering method according to claim 2, characterized in that the irradiation area of the second laser light is equal to or larger than the irradiation area of the first laser light. the joint portion is composed of an electrode land formed on the surface of the substrate and a terminal on the lower surface of the electronic component mounted on the surface of the substrate, and a solder material is interposed in advance between the electrode land and the terminal;
the joint is preliminarily heated by the second laser light through the substrate, and is fully heated by the first laser light through the electronic component;
4. The laser soldering method according to claim 2 or 3. the joint portion comprises an annular electrode land formed on the substrate and a pin-shaped terminal of an electronic component mounted on the rear surface of the substrate, the terminal being inserted into a through hole of the electrode land;
The first laser light directly heats the joint from the front surface side of the substrate, and the second laser light directly heats the joint from the back surface side of the substrate or indirectly heats the joint via an electronic component.
4. The laser soldering method according to claim 2 or 3. A laser soldering apparatus for soldering a joint between an electrode land of a substrate and a terminal of an electronic component mounted on the substrate by irradiating the electrode land with a laser beam, comprising:
the laser soldering device has a first irradiation head that irradiates a first laser beam onto a front surface of the board, and a second irradiation head that irradiates a second laser beam onto a rear surface of the board;
A laser soldering apparatus comprising: the first laser light is a laser light for main heating that heats the joint portion to the soldering temperature,
the second laser light is a preheating laser light for preheating the joint to a preheating temperature lower than the soldering temperature,
The first laser and the second laser light are irradiated simultaneously or with a time lag therebetween, and then the second laser light is stopped before the temperature of the joint reaches the soldering temperature, and the first laser is irradiated until the temperature of the joint reaches the soldering temperature.
7. The laser soldering apparatus according to claim 6. The irradiation area of the second laser light is equal to or larger than the irradiation area of the first laser light.
8. The laser soldering apparatus according to claim 7. the joint portion is composed of an electrode land formed on the surface of the substrate and a terminal on the lower surface of the electronic component mounted on the surface of the substrate, and a solder material is interposed in advance between the electrode land and the terminal;
the joint is preliminarily heated by the second laser light through the substrate, and is fully heated by the first laser light through the electronic component;
9. The laser soldering apparatus according to claim 7 or 8. the joint portion is composed of an annular electrode land formed on the substrate and a pin-shaped terminal of an electronic component mounted on the rear surface of the substrate, the terminal being inserted into a through hole of the electrode land from the rear surface side of the substrate,
The laser soldering apparatus according to claim 7 or 8, characterized in that the first irradiation head irradiates the first laser light directly onto the joint, and the second irradiation head irradiates the second laser light onto the joint on the back surface of the board and an area surrounding the joint. The laser soldering device according to claim 6, characterized in that the first irradiation head has a solder supply nozzle for supplying linear solder to the joint and a non-contact thermometer for measuring the temperature of the joint, and the second irradiation head has a non-contact thermometer for measuring the temperature of the joint.

Images