JP2017131926A - Soldering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soldering method that can readily provide quality soldering for a wide range of usage.SOLUTION: The soldering method includes: a setting step of setting a second work (4) having a hole part (5) opening along a thickness direction on an upper layer side of a first work (2) via a solder layer (6); and a melting step of melting the solder layer by emitting a laser beam to the solder layer exposed from the hole part.SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to a soldering method that can be used, for example, for soldering used for attachment or correction of electronic components.

  Conventionally, soldering is known as a joining method used for mounting and correcting electronic components. Various methods have been devised so far as the soldering method, for example, by bringing a soldering iron having a high temperature tip into contact with the workpiece to be joined, and melting the solder interposed between the workpieces by heat transfer, There is what joins between workpieces. For example, Patent Document 1 discloses a technique for performing solder bonding by melting a solder by heating a workpiece by laser light irradiation in such a soldering method.

Here, an example of a soldering method using laser light will be briefly described with reference to FIG. FIG. 9 is a schematic diagram schematically showing an example of a soldering method using laser light.
In the soldering method according to this typical example, a soldering apparatus 50 including a laser oscillation unit 52, an optical fiber 54, and an emission unit 56 is used. The laser oscillation unit 52 includes a laser oscillation medium such as a YAG laser and a laser power source unit, and outputs laser light having a predetermined output value. The optical fiber 54 has an arbitrary length and is configured to guide the laser light from the laser oscillation unit 52 to the distal end portion 62 of the emission unit 56. A conductor pattern is disposed on the printed circuit board 57 to be joined, and lead terminals 60 of the IC 58 are installed on the conductor pattern via solder (not shown). The emission unit 56 irradiates the surface of the lead terminal 60 with laser light from the tip end portion 62, thereby heating the lead terminal 60 with the energy of the laser light and melting the solder in the vicinity thereof. When the irradiation of the laser beam is completed, the molten solder near the lead terminal 60 is cooled and solidified, and an electrical and physical solder joint is formed between the lead terminal 60 and the conductor pattern on the printed circuit board 57.

Japanese Patent Laid-Open No. 6-23529

In Patent Document 1, YAG laser light, which is a solid-state laser most widely used in the manufacturing field, is used as laser light for heating solder. A YAG laser is a YAG (Y ₃ Al ₅ O ₁₂ ) crystal as a base material doped with rare earth active ions (Nd ³⁺ , Yb ^3+, etc.), and the fundamental wavelength of a typical Nd: YAG laser is 1064 nm. is there.

  By the way, in order to heat a predetermined object by the energy of the laser beam, the optical connectivity between the object and the laser beam is important. If the optical coupling property is low, the energy absorption efficiency is lowered due to an increase in the reflectance of the laser beam, and the time required for heating is increased. In the case of the above-mentioned YAG laser, since the optical coupling with materials such as copper, gold, platinum and aluminum is low, it takes time to heat the workpiece containing these materials. However, such a method has a problem that productivity is lowered. In particular, when the laser output is suppressed so as not to heat the solder excessively, if the material having low optical connectivity is heated as described above, the working time tends to be long, and the above problems are more remarkable. It will be something.

  At least one embodiment of the present invention has been made in view of the above-described problems, and an object thereof is to provide a soldering method capable of rapid and high-quality solder bonding in a wide range of applications.

(1) In order to solve the above problems, a solder bonding method according to at least one embodiment of the present invention has a hole that opens along the thickness direction through the solder layer on the upper layer side of the first workpiece. An installation step of installing the second workpiece having the second workpiece, and a melting step of melting the solder layer by irradiating the solder layer exposed from the hole with a laser beam.

  According to the configuration of (1) above, since the hole is formed in the second workpiece arranged on the upper layer side with respect to the first workpiece via the solder layer, the solder layer is formed via the hole. Can be directly irradiated with laser light. Therefore, it is difficult to be affected by the laser beam used and the optical connectivity of the workpiece, and good soldering is possible in a wide range of applications regardless of the specifications of the laser beam and the components of the first workpiece and the second workpiece. It becomes possible. Further, since the energy of the laser beam can be efficiently supplied to the solder layer, the solder layer can be heated quickly, and an improvement in productivity can be expected.

(2) In some embodiments, in the configuration of the above (1), the first work and the second work include a material having low optical coupling with the laser beam as compared with the solder layer. .

  According to the configuration of (2) above, even when the optical coupling between the workpiece and the laser beam is low, the laser beam can be directly applied to the solder layer through the hole, so that suitable solder is used. Applicable.

(3) In some embodiments, in the configuration of the above (1), the second workpiece includes a material having lower optical coupling with the laser beam than the solder layer.

  According to the configuration of (3) above, even if the second workpiece on the laser beam irradiation side of the two workpieces has a low optical coupling property with the laser beam, the laser beam is passed through the hole. Therefore, the solder layer can be directly irradiated, so that suitable soldering can be performed.

(4) In some embodiments, in any one of the above configurations (1) to (3), the laser beam is a diffusion plate disposed on the second workpiece so as to cover the hole. It penetrates and is irradiated with respect to the said solder layer.

  According to the configuration of (4) above, the intensity can be easily adjusted by transmitting the laser beam through the diffusion plate, and the workpiece can be processed even when the molten solder layer is scattered by the hole being covered by the diffusion plate. The surface can be prevented from becoming dirty.

(5) In some embodiments, in any one of the above configurations (1) to (4), the laser beam is irradiated with a beam diameter expanded by a beam expander installed on the channel.

  According to the configuration (5), since the laser beam can be irradiated over a relatively wide range of the solder layer, a wide bonding region can be obtained and solder bonding excellent in reliability can be achieved.

(6) In some embodiments, in any one of the above configurations (1) to (5), the laser beam includes at least one of a YAG laser fundamental wave, a semiconductor laser, a fiber laser, a YAG laser harmonic, and a disk laser. The first workpiece and the second workpiece include copper, gold, platinum, or aluminum.

  According to the configuration of (6) above, the work including materials such as copper, gold, platinum, and aluminum and these lasers have low optical coupling properties. Suitable soldering is possible.

  According to at least one embodiment of the present invention, it is possible to provide a soldering method capable of rapid and high-quality solder bonding in a wide range of applications.

It is a flowchart which shows the soldering method which concerns on at least 1 embodiment of this invention for every process. It is a schematic diagram which shows a mode that the 2nd workpiece | work in which the hole part was formed by FIG.1 S1 is installed on a 1st workpiece | work through a solder layer by step S2. It is a schematic diagram which shows a mode that a laser beam is irradiated by step S3 of FIG. It is sectional drawing which expands and shows the vertical cross-section structure of the hole vicinity of FIG. It is sectional drawing which shows the structure after the laser beam irradiation of FIG. It is sectional drawing which shows the modification of FIG. It is sectional drawing which shows the modification of FIG. It is sectional drawing which shows the modification of FIG. It is a schematic diagram which shows roughly an example of the soldering method using a laser beam.

Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.
FIG. 1 is a flowchart showing, for each process, a soldering method according to at least one embodiment of the present invention. FIG. 2 shows a second work in which holes are formed in step S1 of FIG. 1, and a solder layer in step S2. FIG. 3 is a schematic view showing a state of being placed on the first workpiece via the wire, FIG. 3 is a schematic view showing a state of irradiating the laser beam in step S3 of FIG. 1, and FIG. 4 is the vicinity of the hole of FIG. FIG. 5 is a sectional view showing the configuration after the laser beam irradiation of FIG. 4, and FIGS. 6 and 7 are sectional views showing a modification of FIG. 4. .

In the present embodiment, a case where the first workpiece 2 and the second workpiece 4 made of a base material including materials such as copper, gold, platinum, and aluminum are used as an object to be joined by soldering will be described as an example. For example, a Ni plating layer or an Au plating layer may be formed on the base or the surface of the first workpiece 2 and the second workpiece 4.
In the present embodiment, an example is shown in which the present invention is applied to a joining method using soldering, but the present invention can also be applied to a joining method using brazing based on the same technical idea.

First, in step S1, pretreatment for forming the hole 5 that opens along the thickness direction is performed on the second workpiece 4 of the two workpieces to be joined. The hole 5 is formed at a position corresponding to a soldered point to which laser light is irradiated in a melting process described later. The hole 5 is formed by, for example, punching (for example, the second workpiece 4 to be processed is fixed on a predetermined die with a stripper, and a punch corresponding to the diameter shape of the hole 5 is used. Formed by punching). As will be described later, since the hole 5 is irradiated with laser light for melting the solder layer, it is set to have a larger diameter than the laser light.
When the work to be soldered is a finer semiconductor circuit or the like, for example, the hole 5 may be formed by patterning by resist processing. In this case, the hole 5 is formed on the second workpiece 4 that is stacked on the first workpiece 2 via the solder layer 6 by performing step S2 described later before the step S1. May be.

In step S2, as shown in FIG. 2, the second workpiece 4 in which the hole 5 is formed in step S1 is placed on the first workpiece 2 via the solder layer 6 (installation step). Here, the solder forming the solder layer 6 is an alloy mainly composed of lead and tin, including eutectic solder, lead-free solder, cream solder, copper / silver solder, and acoustic solder. Any of various solders can be used.
Depending on the output of the laser beam used for soldering, solder having a relatively high melting point (as a guide, a melting point higher than that of general eutectic solder (tin content is about 63%)) may be used. The solder may contain a flux.

  In step S3, the solder layer 6 is melted by irradiating the solder layer 6 with laser light through the hole 5 formed in the second workpiece 4 (melting step). In this embodiment, as shown in FIG. 3 and FIG. 4, the laser irradiation unit 10 that can irradiate laser light is installed so as to face the second workpiece 4. On the other hand, since the hole 5 is formed in the second workpiece 4, a part (exposed region 7) of the solder layer 6 is exposed to the outside through the hole 5. The laser beam emitted from the laser irradiation unit 10 is irradiated to the exposed region 7 of the solder layer 6 through the hole 5.

  As a result, as shown in FIG. 5, the solder layer 6 in the vicinity of the exposed region 7 is heated and melted by the energy of the laser beam to form a melted portion 8. As described above, since the hole 5 is provided in the second workpiece 4, the laser light emitted from the laser irradiation unit 10 is directly irradiated onto the solder layer 6 through the hole 5. The solder layer 6 is effectively heated.

  In the present embodiment, a laser generator (not shown) incorporating a laser oscillation medium (YAG laser) and a laser power supply unit is connected to the laser irradiation unit 10 via an optical fiber 12, and is generated by the laser generator. The laser beam having the YAG laser fundamental wave (wavelength: 1064 nm) is guided to the laser irradiation unit 10 via the optical fiber 12. Here, as described above, the YAG laser fundamental wave has optical connectivity to the first work 2 and the second work 4 made of a base material containing materials such as copper, gold, platinum, and aluminum. Since it is low, it takes time to solder when trying to heat the base material itself. In that respect, in this embodiment, even when the optical connectivity between the workpiece and the laser beam is low, the solder layer 6 is directly irradiated and melted through the hole 5 to melt the laser beam. It is not easily affected by optical connectivity, and can be soldered well in a wide range of applications regardless of the laser specifications and the components of the workpiece.

  The output value of the laser light emitted from the laser irradiation unit 10 may be arbitrary, but it is preferable that the output is adjusted so that the solder layer 6 is not excessively heated (for example, the solder layer 6 is melted by the laser light). The output should be adjusted to the extent that it does not scatter around it). Such laser beam output adjustment may be performed on the side of the laser transmitter that generates the laser beam, or may be performed by performing predetermined processing on the laser beam output from the laser transmitter. Good. In the latter case, for example, as shown in FIG. 6, by setting the convergence position (focal position) of the laser light output from the laser irradiation unit 10 to the front side of the solder layer 6, the laser light can be perforated 5. The inner wall 14 may be irradiated. In this case, at least a part of the laser light is reflected by the inner wall 14 and is applied to the solder layer 6, so that the intensity of the laser light reaching the solder layer 6 is reduced considerably (in this case, copper, gold, The laser beam can be effectively reflected by the inner wall 14 by daringly selecting a YAG laser fundamental wave having low optical connectivity with the second workpiece 4 containing platinum or aluminum).

  Further, as shown in FIG. 7, by arranging a diffusion plate (frosted glass) 15 so as to cover the hole 5 on the surface of the second workpiece 4 in the optical path of the laser light, the diffusion plate 15. The output of the laser beam irradiated onto the solder layer 6 may be adjusted by lowering the intensity of the laser beam that passes through the electrode. In this case, in addition to preventing excessive heating of the solder layer 6 by adjusting the output of the laser beam, it is possible to effectively prevent the workpiece surface from being soiled by scattered matter when the solder layer 6 is melted.

  In addition to the above-described YAG laser fundamental wave, for example, a semiconductor laser, a fiber laser, a YAG laser harmonic, and a disk laser can be used depending on the application. For example, when the base material is allowed to melt during soldering, a YAG laser harmonic having high optical connectivity with a base material containing materials such as copper, gold, platinum and aluminum may be used. Conversely, when avoiding melting of the base material during soldering, a laser light source other than the YAG laser harmonics may be used. In the present embodiment, the YAG laser fundamental wave is used as the laser light, and the solder layer 6 can be heated accurately while avoiding melting of the base material, so that high-quality soldering is possible.

  Further, the laser irradiation unit 10 may be configured so that the irradiation area of the laser beam is widened with respect to the solder layer 6. For example, in FIG. 8, a beam expander 16 for expanding the beam diameter of the laser light is provided on the optical path of the laser light emitted from the laser irradiation unit 10. As a result, a laser beam whose beam diameter is adjusted to be slightly smaller than the hole 5 is output from the beam expander 16 to the solder layer 6. Thereby, a laser beam can be irradiated over a relatively wide range of the solder layer 6 exposed from the hole 5. As a result, the solder layer 6 can be melted over a wide range as compared with the case of irradiating a laser beam to an extremely narrow region as shown in FIGS. 3 and 4, for example, so that highly reliable solder bonding is possible. .

  When the beam diameter of the laser beam irradiated onto the solder layer 6 is small, the laser beam irradiation area is scanned (scanned) on the surface of the solder layer 6 exposed from the hole 5 to widen the range. The solder layer 6 may be melted to obtain a strong bond.

  Subsequently, when the laser irradiation from the laser irradiation unit 10 is finished, the molten solder is cooled and solidified (step S4). Thereby, the first workpiece 2 and the second workpiece 4 are electrically and physically joined via the solder layer 6.

  As described above, according to the present embodiment, by directly irradiating the solder layer 6 with the laser beam through the hole 5 formed in the second workpiece 4, the laser specifications and the workpiece material can be applied. Regardless, the solder layer 6 can be effectively heated and melted. Therefore, high-quality soldering can be performed in a wide range of applications, and excellent productivity can be obtained.

  Such a soldering method is not only the bonding of various electronic components to a conductor pattern on a printed circuit board as in Patent Document 1, but also, for example, wire bonding at an external lead terminal of a semiconductor package or an electrode pad of a semiconductor chip. In addition, it can be widely applied as a joint application for electronic parts. In such fields, materials such as copper and gold are being used frequently with the recent high integration and high speed. For example, as the material of the external lead terminal (lead) of the package, the use of a Cu alloy system excellent in electric conductivity and thermal conductivity is increasing in place of the conventionally used Fe—Ni alloy system. In addition, materials for wiring and electrode pads used in semiconductor packages are also increasing in the use of Cu, which has a lower specific resistance than conventional Al and hardly causes electromigration. Therefore, when a YAG laser is used when bonding such objects, it takes time to heat the workpiece itself because of its low optical connectivity. However, by heating the solder layer 6 directly through the hole 5 without heating the workpiece itself as in the above-described embodiment, good soldering can be achieved without being affected by optical connectivity. It becomes possible.

  At least 1 embodiment of this invention can be utilized for the soldering method which can be used for the soldering used, for example for attachment or correction of an electronic component.

2 First Work 4 Second Work 5 Hole 6 Solder Layer 7 Exposed Area 8 Melting Part 10 Laser Irradiation Part 12 Optical Fiber 14 Inner Wall 16 Beam Expander

Claims (6)

An installation step of installing a second workpiece having a hole opening along the thickness direction on the upper layer side of the first workpiece via a solder layer;
A melting step of melting the solder layer by irradiating the solder layer exposed from the hole with a laser beam;
A soldering method comprising the steps of:   2. The soldering method according to claim 1, wherein the first workpiece and the second workpiece include a material having lower optical coupling with the laser beam than the solder layer.   2. The soldering method according to claim 1, wherein the second workpiece includes a material having lower optical coupling with the laser beam than the solder layer.   4. The laser beam is applied to the solder layer through the diffusion plate disposed on the second workpiece so as to cover the hole. 5. The soldering method according to claim 1.   The soldering method according to any one of claims 1 to 4, wherein the laser beam is irradiated with a beam diameter expanded by a beam expander installed on a channel. The laser beam includes at least one of a YAG laser fundamental wave, a semiconductor laser, a fiber laser, a YAG laser harmonic, and a disk laser,
The soldering method according to any one of claims 1 to 5, wherein the first workpiece and the second workpiece include copper, gold, platinum, or aluminum.

Images