WO2019065065A1

WO2019065065A1 - Soldering system and soldering method

Info

Publication number: WO2019065065A1
Application number: PCT/JP2018/032135
Authority: WO
Inventors: 利輝藤島; 茂田玉; 広宣小林
Original assignee: 株式会社堀内電機製作所
Priority date: 2017-09-27
Filing date: 2018-08-30
Publication date: 2019-04-04
Also published as: JP6785512B2; JPWO2019065065A1

Abstract

Provided are a soldering system and a soldering method, whereby solder can be uniformly spread on a to-be-soldered part without damaging a fine soldering target article, and an excellent solder can be achieved. Even after molten solder attaches to the to-be-soldered part, the molten solder is continuously heated by continuously irradiating the molten solder with a semiconductor laser. As a result of the above treatment, an alloy of the to-be-soldered part and the molten solder is formed, the molten solder sufficiently wets the to-be-soldered part, and the molten solder flows to the to-be-soldered part by means of a capillary action.

Description

Soldering system and method

The present invention relates to a soldering system and method using a laser.

2. Description of the Related Art In recent years, with the miniaturization of electronic devices, surface mount devices (SMDs) have been widely used for many electronic circuit components. When soldering an SMD to a printed circuit board, the reflow method has become mainstream. The substrate on which the SMD is mounted has a printed pattern formed of copper foil on the front side, and the SMD is mounted on the printed pattern. Then, after the cream solder is applied to the contact portion between the SMD and the print pattern, it is heated in a reflow furnace. By raising the temperature to a temperature at which the solder melts in a short time, the solder paste is melted by melting the cream solder.

In the reflow method soldering by the reflow furnace, since the SMD is placed flatly on the surface of the printed circuit board, the place to be soldered is also flat. Therefore, when the solder is heated, the solder spreads in a plane with respect to the portion to be soldered. However, depending on the shape of parts, modules, etc., the reflow method may not be able to be used because the place to be soldered is not flat.

FIG. 14 is an external perspective view schematically showing a CMOS image sensor 1401 incorporated in a mobile phone, a smartphone or the like.
In the CMOS image sensor 1401 also called a camera module, a voice coil motor (not shown) is incorporated in the objective lens 1402, and focus control is performed by drive control of the voice coil motor. The control current applied to the voice coil motor causes noise to other electronic circuits and adversely affects electromagnetic interference (EMI). For this reason, it is necessary to cover parts, such as a lens including a voice coil motor, with a metal cover 1403 and connect the cover 1403 to a ground node.

As shown in FIG. 14, the metal cover 1403 is soldered to the ground node terminal 1405 of the flexible printed circuit 1404. However, the contact portion between the metal cover 1403 and the flexible printed circuit 1404 has an angle of approximately 90 °, and has a three-dimensional positional relationship. Also, it is necessary to solder between the signal terminal 1406 of the circuit formed inside the cover 1403 and the signal terminal 1407 of the flexible printed circuit 1404 to form a signal line, and the location of this soldering is also approximately 90. An angle of ° is formed.
As described above, when steep angles are formed between the members to be soldered and the three-dimensional positional relationship is established, the molten solder does not spread evenly to the portions to be soldered, so the soldering using the reflow furnace is It is almost impossible. Also, even if the location to be soldered is not angled as in the CMOS image sensor 1401, if a material susceptible to high temperature is used for a part such as a part or module to be soldered, a reflow furnace When using the material, the material is destroyed by high heat, and it is not possible to create the intended part or module.
A laser soldering apparatus is used to solder parts and modules to which the reflow method can not be applied.

Patent documents 1 and 2 disclose prior art documents in which a technique considered to be close to the present invention is disclosed.
Patent Document 1 discloses the technology of a solder ball bonding apparatus (laser soldering apparatus) using a laser. In this solder ball bonding apparatus, in order to bond two members to be soldered in a substantially vertical position by solder ball bonding, the solder balls are first accurately positioned, and the members to be soldered are positioned substantially in a vertical relation to each other. Place the solder ball in a stable condition. Thereafter, the solder balls are melted by laser irradiation and soldered.
Patent Document 2 discloses the technology of a laser irradiation type solder bonding apparatus (laser soldering apparatus). This laser irradiation type solder bonding apparatus supplies a wire solder from the solder supply apparatus to the optical path of the laser beam to form a melted solder ball. Then, compressed gas is supplied from the compressor into the head, and molten solder balls are sprayed from the small holes. The laser beam emitted from the small hole is irradiated to the solder ball sprayed to the joint portion.

JP, 2002-45962, A Japanese Patent Application Laid-Open No. 06-23530

However, when the technique described in Patent Document 1 is applied to a minimal part or the like, it has been found that the following phenomenon occurs. When the solder balls are melted by a laser, the solder melted by the laser cools and solidifies in a state of being dropped in the space portion of the member to be soldered. For this reason, the problem that the supply of the solder to a soldering object member is not enough, and a concern remains in a reliable connection arises.
Also, solid-state lasers such as YAG lasers used in prior art laser welding devices have too much thermal energy when used in solder. Furthermore, solid lasers are extremely difficult to control power. For this reason, there is a high possibility of damaging parts and printed circuit boards which are objects to be minutely soldered.

The present invention has been made in view of such a situation, and a soldering system and a soldering method which can spread fine areas to be soldered without damaging the minute object to be soldered and can achieve good soldering. Intended to be provided.

In order to solve the above-mentioned subject, a soldering system of the present invention has a soldering device and a control device.
The soldering apparatus comprises a solder holder, a solder supply apparatus for supplying solder to the solder holder, and laser light of a first intensity intermittently for a predetermined time to melt the solder in proximity to the object to be soldered for a predetermined time. A semiconductor laser light source for irradiating, a gas valve for controlling injection of pressure gas for injecting molten solder from the solder holder to the solder holder, and a pressure sensor for detecting pressure of pressure gas in the solder holder .
After the solder reaches the solder holder, the control device detects from the pressure sensor that the pressure inside the soldering device has reached a predetermined value, performs on control of the semiconductor laser light source, and performs control of closing the gas valve. After being ejected from the solder holder, the solder is continuously irradiated with laser light of a second intensity which is weaker than the first intensity for a predetermined time, and then the semiconductor laser light source is turned off and the gas valve is opened.

According to the present invention, it is possible to provide a soldering apparatus and a soldering method that can complete soldering with good wettability without damaging minute objects to be soldered.
Problems, configurations, and effects other than those described above will be apparent from the description of the embodiments below.

1 is a schematic front view of a laser soldering apparatus according to an embodiment of the present invention. It is an enlarged view of a solder roller. It is a schematic cross section which shows the structure of the front-end | tip part of a solder holder. It is a block diagram which shows the whole structure of a soldering system, and the structure of the hardware of the control apparatus which controls a laser soldering apparatus. It is a block diagram which shows the function of the software of a control apparatus. It is a time chart which shows various states of a laser soldering device controlled by a control device. A schematic cross-sectional view enlarging a part of the solder holder and the object to be soldered, showing a state immediately after the semiconductor ball is irradiated with the semiconductor laser and a state immediately after the solder ball is melted by the semiconductor laser and discharged from the discharge port. FIG. The section of the solder holder and part of the object to be soldered is enlarged, in which the irradiation of the semiconductor laser is continued to the molten solder and the molten solder fully wets the soldering portion of the object to be soldered FIG. Solder that shows a state immediately after the semiconductor ball is irradiated to the solder ball and a state immediately after the solder ball is melted by the semiconductor laser and changed to molten solder by using the laser soldering apparatus according to the modification of the present invention It is a schematic cross section which expanded a holder and a part of soldering object. The section of the solder holder and part of the object to be soldered is enlarged, in which the irradiation of the semiconductor laser is continued to the molten solder and the molten solder fully wets the soldering portion of the object to be soldered FIG. It is a block diagram which shows the functional block added to the control apparatus of the laser soldering apparatus based on the 2nd modification of this invention. It is a block diagram and circuit diagram of a gate control part and a laser drive part of laser soldering device concerning the 2nd modification of the present invention. FIG. 7 is a diagram showing a time chart of a control signal output by a laser control unit, a reference voltage switching signal output by a gate control unit, a voltage waveform of a gate control signal, and a waveform of current flowing in a semiconductor laser light source. It is an appearance perspective view showing roughly a CMOS image sensor built in a mobile phone, a smart phone, etc.

[Appearance of laser soldering apparatus]
FIG. 1 is a schematic front view of a laser soldering apparatus 101 according to an embodiment of the present invention.
As shown in FIG. 1, the laser soldering apparatus 101 has a laser barrel 103 to which a semiconductor laser light source 102 is attached. A first reflecting mirror 104 is incorporated at the tip of the laser barrel 103 at an inclination of 45 ° with respect to the longitudinal direction of the laser barrel 103. Furthermore, in the main body portion 105, the second reflecting mirror 106 is incorporated at the same inclination as the first reflecting mirror 104, and the solder holder 107 at the tip of the main body portion 105 has the laser light reflected by the first reflecting mirror 104. It is comprised so that it may irradiate to the solder ball 201 (refer FIG. 2) to hold | maintain. The laser soldering apparatus 101 employs solder balls 201 having a uniform particle size to provide a uniform amount of solder to the object to be soldered 415 (see FIG. 4).
A laser soldering apparatus 101 according to an embodiment of the present invention is a blue semiconductor laser that emits visible light with a wavelength of 500 nm or less, which has a lower output and is suitable for soldering, instead of a high-output solid laser of the prior art. It is adopted.

A substantially conical solder holder 107 is provided at the tip of the main body portion 105 of the laser soldering apparatus 101. The solder holder 107 is hollow and its tip has a hole for discharging the molten solder ball 201. Details of the solder holder 107 will be described in detail with reference to FIG.
The solder holder 107 is attached to the holder holding portion 108. The holder holder 108 is also generally conical in shape, to which a conduit 110 extending from the solder feeder 109 is connected. Further, a gas inlet 111 to which compressed nitrogen gas (pressure gas) is supplied is provided, and a compressed gas introduction mechanism (not shown) is connected through a nitrogen gas valve (see FIG. 4). Further, a pressure sensor 412 (see FIG. 4) (not shown) is enclosed in the solder holder 107, measures the pressure of nitrogen gas, and outputs digital data indicating the pressure of nitrogen gas.
Nitrogen gas is used to provide pressure for discharging the molten solder ball 201 from the solder holder 107 and to prevent oxidation of the molten solder.

The laser soldering apparatus 101 is provided with a vertical driving mechanism (not shown). In the upper and lower drive mechanism, when the soldering point 415a (see FIG. 7) of the object 415 to be soldered reaches a position directly below the solder holder 107 by a transfer mechanism such as a belt conveyor (not shown) The laser soldering apparatus 101 is driven downward to bring the solder holder 107 close to the soldering target portion of the soldering object 415. Then, when the soldering process is completed, the laser soldering apparatus 101 is driven upward to separate the solder holder 107 from the object 415 to be soldered.

[Structure of Solder Roller 113]
The solder supply device 109 includes a solder ball tank 112, a solder roller 113, and a conduit 110. In addition, a solder passage sensor 114 configured of a metal detection sensor is installed in the middle of the conduit 110, and the solder passage sensor 114 detects that the solder ball 201 has passed through the conduit 110.
FIG. 2 is an enlarged view of the solder roller 113. The solder ball 201 is also shown for reference.
In the solder roller 113, depressions 113a slightly larger than the size of the solder balls 201 are provided at four positions of 90 ° on the circumference of the disk. The solder roller 113 is rotationally driven by a stepping motor (not shown). Then, one solder ball 201 fits into the recess 113 a, and when the recess 113 a reaches directly below, the solder ball 201 falls and is led to the conduit 110. The number of depressions 113 a provided in the solder roller 113 is not necessarily four, and is arbitrary.

[Structure of Solder Holder 107]
FIG. 3 is a schematic cross-sectional view showing the structure of the tip portion of the solder holder 107. As shown in FIG. The solder holder 107 is a material such as aluminum alloy, stainless steel, nickel, brass, brass or chrome plated metal, ceramic or the like, which has low solder wettability, is less likely to adhere to solder, and can withstand high temperature of molten solder. It is formed by
Inside the substantially conical solder holder 107, a tapered space 107a which is tapered toward the tip is formed. The inner wall of the tapered space 107 a in this space reliably guides the solder ball 201 to the tip of the solder holder 107.
The tip end of the tapered space 107a is formed with a cylindrical space 107b having a fixed thickness. Further, the tip of the cylindrical space 107 b is formed with a solder retaining portion 107 c that abuts on the solder ball 201. A discharge port 107d which is a cylindrical hole is opened in the solder retaining portion 107c, and the melted solder is discharged from the discharge port 107d.

Assuming that the diameter of the solder ball 201 is SR, the diameter of the discharge port 107d is D1, and the diameter of the cylindrical space 107b is D2, the relationship shown by the following inequality is satisfied.
D1 <SR <D2
Therefore, the solder ball 201 dropped into the solder holder 107 through the conduit 110 is fitted into the cylindrical space 107b so as to slide in the inner wall in the tapered space 107a in the solder holder 107, and the solder locking portion 107c At the solder holder 107. When the solder ball 201 reaches the solder locking portion 107 c, the discharge port 107 d is closed by the solder ball 201.

[Overall Configuration of Soldering System 401 and Hardware Configuration of Control Device]
FIG. 4 is a block diagram showing the overall configuration of the soldering system 401 and the hardware configuration of the control unit 402 that controls the laser soldering apparatus 101. As shown in FIG.
The soldering system 401 comprises a laser soldering apparatus 101 and a controller 402.
The control device 402, which is a well-known microcomputer, includes a CPU 404, a ROM 405, a RAM 406, a non-volatile storage 407 such as an electrically rewritable flash memory, an input port 408, an output port 409, and a timer 410 connected to a bus 403. Prepare. The non-volatile storage 407 stores a control program for operating the microcomputer as the control device 402. Note that the flash memory may be used as the ROM 405 and the non-volatile storage 407.
Further, the control device 402 is not limited to a microcomputer, and may be a personal computer provided with an appropriate interface.

The input port 408 is provided in the vicinity of the laser soldering apparatus 101, and includes an object sensor 411 constituted by a photo interrupter or the like, a solder passage sensor 114 detecting that the solder ball 201 has passed through the conduit 110, and a laser A pressure sensor 412 is connected to measure the pressure of nitrogen gas inside the soldering apparatus 101.
The output port 409 includes a stepping motor 413 for rotationally driving the solder roller 113, a nitrogen gas valve 414 (gas valve) for controlling the injection of nitrogen gas into the laser soldering apparatus 101, and a semiconductor incorporated in the laser lens barrel 103. A laser light source 102 is connected.
That is, the control device 402 detects the presence of the soldering object 415 by the object sensor 411, detects the normal supply of the solder ball 201 by the solder passage sensor 114, and measures the pressure of nitrogen gas by the pressure sensor 412. Do.
Further, the control device 402 rotationally drives the stepping motor 413 to supply the solder balls 201 to the solder holder 107, controls the nitrogen gas valve 414, injects nitrogen gas into the laser soldering apparatus 101 at an appropriate timing, and The light source 102 is controlled to melt the solder ball 201 at an appropriate timing.

[Software Function of Controller 402]
FIG. 5 is a block diagram showing the function of software of the control device 402. As shown in FIG.
The logic signal output from the object sensor 411 is supplied to the Cp input terminal of a D flip flop (hereinafter, abbreviated as “D-FF” and the same as FIG. 5).
The logic signal output from the solder passage sensor 114 is supplied to the R input terminal of the D-FF 501.
The D input terminal of the D-FF 501 is connected to the logic signal node indicating the logic true, and is always in the logic true state.
That is, the D-FF 501 converts the up edge of the output signal of the object sensor 411 into a logic true logic signal and outputs it, and the solder passage sensor 114 outputs a logic true logic signal, thereby causing the logic false. Output logic signal. The up edge of the output signal of the object sensor 411 indicates that the object sensor 411 has detected the arrival of a new soldering object 415.

The logic signal output from the Q output terminal of the D-FF 501 is connected to the input of the AND gate 502 together with the logic signal of the timer 410.
The timer 410 starts clocking from an output signal of a comparator 503 described later, and outputs a logic signal for turning off a laser control unit 504 described later when a predetermined time is counted. Therefore, the output signal of the AND gate 502 is detected when the object sensor 411 detects that the new soldering object 415 has arrived immediately below the solder holder 107 while the semiconductor laser light source 102 is controlled to be off. Output a signal indicating the logic true.
The output signal of the AND gate 502 is input to the motor control unit 505 together with the logic signal output from the solder passage sensor 114.

In response to the output signal of the AND gate 502 becoming logical true, the motor control unit 505 outputs a stepping pulse for rotating the stepping motor 413 by 90 °. Then, when the output signal of the solder passage sensor 114 becomes logic true within the time defined by the timer built in the motor control unit 505, the operation is stopped.
If the output signal of the solder passage sensor 114 does not become logic true within the time specified by the timer built in the motor control unit 505, it means that the solder roller 113 has failed to put the solder ball 201. Show. Therefore, a stepping pulse for rotating the stepping motor 413 by 90 ° is output again.

Data indicative of the pressure of the pressure sensor 412 is input to the digital comparator 503 together with data indicative of the pressure threshold. The comparator 503 outputs logic true when the pressure of nitrogen gas detected by the pressure sensor 412 exceeds the pressure threshold 506.
The output signal of the timer 410 is input to the valve control unit 507 together with the logic signal output from the comparator 503.
The valve control unit 507 outputs a control signal for opening the nitrogen gas valve 414 in response to the output signal of the timer 410 becoming logic true. Then, in response to the output signal of the comparator 503 becoming logic true, a control signal for closing the nitrogen gas valve 414 is output.

The output signal of the comparator 503 is supplied to the timer 410. The timer 410 starts counting a predetermined time in response to the output signal of the comparator 503 becoming logic true. Then, when a predetermined time has elapsed, an output signal indicating the logic true is output.
Further, since the output signal of the solder passage sensor 114 is supplied to the reset terminal of the timer 410, the timer 410 is reset when the output signal of the solder passage sensor 114 becomes logical true after measuring a predetermined time.

The output signal of the comparator 503 is input to the laser control unit 504 together with the logic signal output from the timer 410.
The laser control unit 504 outputs a control signal to turn on the semiconductor laser light source 102 in response to the output signal of the comparator 503 becoming logic true. Then, in response to the output signal of the timer 410 becoming logic true, a control signal for controlling the semiconductor laser light source 102 to turn off is output.

The valve control unit 507 opens the nitrogen gas valve 414 when the output signal of the timer 410 becomes logic true and closes the nitrogen gas valve 414 when the output signal of the comparator 503 becomes logic true.
The laser control unit 504 turns on the semiconductor laser light source 102 when the output signal of the comparator 503 becomes logic true, and turns off the semiconductor laser light source 102 when the output signal of the timer 410 becomes logic true.
That is, the control signals output from the valve control unit 507 to the nitrogen gas valve 414 and the control signals output from the laser control unit 504 to the semiconductor laser light source 102 are in reverse logic.

The software functional block diagram shown in FIG. 5 is an example, and for example, instead of resetting the timer 410 by the solder ball 201 detection sensor, using the output signal of the timer 410 itself, the input of the AND gate 502 or the timer 410 is Various variations are conceivable, such as using a latch function for output and the like.

FIG. 6 is a time chart showing various states of the laser soldering apparatus 101 controlled by the controller 402. As shown in FIG. The inventors conducted an experiment with the laser soldering apparatus 101 and recorded a time chart when good soldering could be realized. The diameter of the solder ball 201 used in this experiment is 0.5 mm, and the output of the blue semiconductor laser is 6.8 W.
A waveform L601 in FIG. 6 is the rotational speed of the solder roller 113.
A waveform L602 is a control signal of the stepping motor 413 for rotating the solder roller 113.
A waveform L603 is a detection signal of the solder passage sensor 114.
A waveform L604 is a waveform indicating the flow rate of nitrogen gas.
A waveform L605 is an output signal of the pressure sensor 412 indicating the pressure of nitrogen gas.
A waveform L606 is a control signal for on / off controlling the semiconductor laser light source 102.
A waveform L 607 is a control signal of the nitrogen gas valve 414 which controls opening and closing of the injection of nitrogen gas.

At time T611, the nitrogen gas valve 414 is open, and the semiconductor laser light source 102 is off.
At time T612, in response to the AND gate 502 outputting logic true, the stepping motor 413 is rotationally driven and the solder roller 113 is rotated.
At time T 613, the solder passage sensor 114 detects that the solder ball 201 has passed through the conduit 110.
At time T614, the solder ball 201 fits into the solder retaining portion 107c of the solder holder 107, and the nitrogen gas does not leak from the discharge port 107d. Then, the pressure of nitrogen gas inside the laser soldering apparatus 101 starts to rise. At this time, the flow rate of nitrogen gas is slightly smaller than that before time T614 because the discharge port 107d is blocked by the solder ball 201.

At time T615, when the comparator 503 detects that the pressure of nitrogen gas in the laser soldering apparatus 101 exceeds the pressure threshold 506, the valve control unit 507 performs control to close the nitrogen gas valve 414. Then, the injection of nitrogen gas into the laser soldering apparatus 101 is stopped. At the same time, the laser control unit 504 turns on the semiconductor laser light source 102. At time T615, the timer 410 is started and counts a predetermined time.
At time T616, the solder ball 201 is melted by the laser beam emitted by the semiconductor laser light source 102. Then, the melted solder is discharged from the discharge port 107 d by the pressure of the nitrogen gas inside the laser soldering apparatus 101. At that moment, the pressure of nitrogen gas inside the laser soldering apparatus 101 rapidly decreases. However, at time T616, the semiconductor laser continues to be irradiated.
At time T617, when the timer 410 detects that the predetermined time has elapsed, the laser control unit 504 performs off control of the semiconductor laser light source 102 in response to the output signal of the timer 410. Then, at the same time as the off control of the semiconductor laser light source 102, the valve control unit 507 performs control to open the nitrogen gas valve 414.

[Soldering behavior]
The flow of the soldering operation in the laser soldering apparatus 101 according to the embodiment of the present invention will now be described.
FIG. 7A is a schematic cross-sectional view showing a part of the solder holder 107 and the object 415 to be soldered, showing a state immediately after the laser light B 701 is irradiated to the solder ball 201. It is the state of the solder holder 107 and the soldering object 415 in time T615 of FIG.
The solder holder 107 is in close proximity to the soldering point 415 a of the object to be soldered 415 by a predetermined distance by a vertical drive mechanism (not shown), and the tip of the solder holder 107 is the object to be soldered Not in touch. The distance between the solder holder 107 and the soldering portion 415a of the object 415 to be soldered is, for example, about 0.5 mm to 3 mm.

FIG. 7B is a schematic sectional view enlarging a part of the solder holder 107 and the object to be soldered 415, showing a state immediately after the solder ball 201 is melted by the laser beam B701 and discharged from the discharge port 107d. The state of the solder holder 107 and the object 415 to be soldered at time T616 in FIG.
The solder ball 201 melts to form a molten solder 702, and adheres to the soldering point 415 a of the object 415 to be soldered. However, in this state, the molten solder 702 is only in contact with the metal of the soldering point 415a, and the molten solder 702 has not reached the state of forming (wetting) an alloy with the surface of the metal.

FIG. 8 shows that the molten solder 702 continues to be irradiated with the laser beam B 701, and the molten solder 702 is soldered with the solder holder 107, which shows a state in which the molten solder 702 is sufficiently wetted to the soldering portion 415a of the object 415 to be soldered. FIG. 16 is a schematic cross-sectional view in which a part of an object 415 is enlarged. It is the state of the solder holder 107 and the soldering object 415 in time T617 of FIG.
That is, the laser soldering apparatus 101 and the controller 402 according to the embodiment of the present invention continue to irradiate the laser beam B 701 even after the molten solder 702 adheres to the soldering portion 415 a. This operation is equivalent to a process step of continuing heating with the soldering iron even after the solder melts so that when the soldering is performed using a soldering iron, the soldering is well adapted to the portion to be soldered.
As long as the solder balls 201 are only melted, it is possible only between time T615 and time T616 in FIG. However, even if the molten solder 702 adheres to the soldering point 415a, an alloy of the soldering point 415a and the molten solder 702 is not formed. An alloy of the soldering point 415a and the molten solder 702 is formed, the molten solder 702 is sufficiently wetted to the soldering point 415a, and the molten solder 702 flows to the soldering point 415a by capillary action to stabilize the electrical characteristics. For this purpose, it is necessary to continue heating the molten solder 702 and the soldering portion 415a for a predetermined time or more for a predetermined temperature or more. The continuation of this heating is a period from time T616 to time T617.

The time for which the heating is continued varies depending on the type of semiconductor laser, the output of the semiconductor laser, the size of the solder ball 201, the size of the soldering portion 415a, etc. On the other hand, the conventional solid-state laser is not suitable for the soldering system 401 according to the embodiment of the present invention because the output of heating is too strong. In particular, it is difficult to continue heating.
In particular, it has been found by experiments of the inventors that a blue semiconductor laser is preferable as the type of semiconductor laser. The blue semiconductor laser has a higher heat absorbing property to the solder than semiconductor lasers of other colors such as red. Therefore, good soldering can be realized.

The following modifications can be made to the embodiment described above.
(1) The laser soldering apparatus 101 according to the embodiment of the present invention described above uses the solder holder 107 that holds the solder ball 201 inside. Since the diameter of the discharge port 107 d is smaller than the solder ball 201, the solder ball 201 can not come out of the solder holder 107 unless the solder ball 201 is melted.
Soldering using a semiconductor laser can be realized even if a solder holder having a simpler structure is used for the solder holder 107 described above.
FIG. 9A shows a state immediately after the laser beam B 701 is irradiated to the solder ball 201 using the laser soldering apparatus 101 according to the first modified example of the present invention. It is a schematic cross section which expanded a part. The state of the solder holder and the object to be soldered 415 at time T615 in FIG. 6 corresponds to FIG. 7A.

The laser soldering apparatus 101 according to the first modification differs from the laser soldering apparatus 101 according to the embodiment described with reference to FIGS. 1 to 8 only in the structure of the solder holder 901, and the other parts, mechanism parts, and functions Since all the blocks and the like are substantially the same, detailed description will be omitted.
In the solder holder 901 shown in FIG. 9A, FIG. 9B and FIG. 10, the cylindrical space 107b becomes the discharge port 107d as it is, so there is no part where the solder ball 201 is locked. That is, if nothing is applied to the tip end portion, the solder ball 201 guided to the solder holder 901 through the conduit 110 will jump out from the discharge port 107 d of the tip end portion as it is.
Therefore, as shown in FIG. 9A, the solder holder 901 is brought into contact with the soldering portion 415a of the object 415 to be soldered. Then, the solder ball 201 is fixed so as to be surrounded by the discharge port 107 d of the solder holder 901 and the soldering portion 415 a.

FIG. 9B is a schematic cross-sectional view enlarging a part of the solder holder 901 and the object 415 to be soldered, showing a state immediately after the solder ball 201 is melted by the laser light B 701 and changed to the molten solder 702. The state of the solder holder 901 and the object to be soldered 415 at time T616 in FIG. 6 corresponds to FIG. 7B.
In FIG. 9A, the solder ball 201 is fixed so as to be surrounded by the discharge port 107 d of the solder holder 901 and the soldering portion 415 a. In this state, when the solder ball 201 is irradiated with the laser beam B701, the solder ball 201 is melted to be changed into the molten solder 702, and adheres to the soldering point 415a. At this time, since the molten solder adheres to the soldering portion 415a by its own weight, it is not necessary to apply a pressure with nitrogen gas.

FIG. 10 shows that the molten solder 702 continues to be irradiated with the laser beam B 701, and the molten solder 702 is soldered with the solder holder 901, which shows that the soldered portion 415a of the object to be soldered 415 is sufficiently wetted. FIG. 16 is a schematic cross-sectional view in which a part of an object 415 is enlarged. The state of the solder holder 901 and the object to be soldered 415 are on the way from time T616 to time T617 in FIG.
In FIG. 9B, by irradiating the solder ball 201 with the laser beam B701, the solder ball 201 is melted and changed to the molten solder 702, and adheres to the soldering point 415a. As soon as the solder balls 201 melt, the laser soldering apparatus 101 is pulled up to separate the solder holder 901 from the soldering point 415a. Meanwhile, the laser beam B 701 continues to irradiate the molten solder 702 attached to the soldering point 415 a.
As described above, even with the configuration in which the solder holder 901 is in contact with the soldering portion 415a, it is possible to realize the laser soldering apparatus 101 according to the present invention.

(2) In the laser soldering apparatus 101 in which the solder holder 901 described above passes through the solder ball 201, instead of the solder ball 201, a solder chip obtained by finely cutting a wire solder may be used. When using the solder holder 901 configured to pass through the solder ball 201, the discharge port 107d is not blocked by the solder ball 201 in the solder holder 901, so that the solder having a uniform shape like the solder ball 201 is not necessarily used. May be

(3) Ideally, the step of melting the solder ball 201 (between time T615 and time T616 in FIG. 6) and the step of heating after the melted solder ball 201 adheres to the soldering portion 415a (FIG. 6) From time T616 to time T617), it is desirable that the heat quantity of heating for the solder ball 201 and the soldering point 415a be different. Such control is impossible with a soldering iron, but with the laser soldering device 101, control of the power applied to the semiconductor laser light source 102 facilitates control of heating of the solder balls 201 and the soldering point 415a. it can.

FIG. 11 is a block diagram showing a functional block added to the control device 402 of the laser soldering apparatus 101 according to the second modified example of the present invention.
In FIG. 5, the control signal that the laser control unit 504 outputs to the semiconductor laser light source 102 is on / off control of the simple laser light B701.
In FIG. 11, a gate control unit 1101 and a laser drive unit 1102 are added to the control signal output from the laser control unit 504.
The gate control unit 1101 receives the control signal of the laser control unit 504 and the output signal of the pressure sensor 412 to control the laser drive unit 1102.
The laser drive unit 1102 performs drive control on the semiconductor laser light source 102 by constant current control.

FIG. 12 is a block diagram and a circuit diagram of a gate control unit 1101 and a laser driving unit 1102 of a laser soldering apparatus 101 according to a second modified example of the present invention.
The gate control unit 1101 is realized as a software function of the control device 402 which is a general microcomputer, and therefore the description of the hardware configuration is omitted.
An output signal of the pressure sensor 412 is input to the differential operation unit 1201. The differential operation unit 1201 performs a differential operation on the output signal of the pressure sensor 412, thereby converting a sharp decrease of the signal occurring at time T616 in FIG. 6 into a pulse signal and outputting it.
The control signal of the laser control unit 504 is input to the sequencer 1202. The sequencer 1202 also receives a pulse signal output from the differential operation unit 1201 and generates a gate control signal of a Pch MOSFET 1203 included in a laser drive unit 1102 described later.
The control signal of the laser control unit 504 is also input to the latch 1204. The latch 1204 also receives a pulse signal output from the differential operation unit 1201 and generates a control signal of a changeover switch 1205 included in a laser drive unit 1102 described later.

The laser drive unit 1102 is configured by a known buck converter that performs constant current control on a DC power supply V 1206 that supplies power to the semiconductor laser light source 102.
The PNP transistor 1207 is a high side switch of the buck converter. The transistor 1207, the diode D1208, and the choke coil L1209 constitute a buck converter.
The high side switch of the Pch MOSFET 1203 is connected between the output terminal side of the choke coil L 1209 and the semiconductor laser light source 102. The description of the gate drive circuit of the Pch MOSFET 1203 is omitted.
Between the cathode of the semiconductor laser light source 102 and the ground node, a shunt resistor R1210 for detecting the current flowing to the semiconductor laser light source 102 is connected.
The connection point between the cathode of the semiconductor laser light source 102 and the shunt resistor R1210 is connected to the positive terminal of the comparator 1211. On the other hand, the first reference voltage source V1212 and the second reference voltage source V1213 are selectively connected to the negative terminal of the comparator 1211 via the changeover switch 1205. The first reference voltage source V1212 outputs a higher voltage than the second reference voltage source V1213. The output of the comparator 1211 is an open collector and is connected to the base of the transistor 1207 via a base resistor R1214. The resistor R1215 is a resistor for ensuring the switching of the transistor 1207. That is, when the open collector of the comparator 1211 is turned off, the transistor 1207 is turned off, and when the open collector of the comparator 1211 is turned on, the transistor 1207 is turned on.

The voltage across terminals of the shunt resistor R 1210 is proportional to the current flowing to the semiconductor laser light source 102.
When the voltage of the shunt resistor R1210 becomes lower than the voltage of the first reference voltage source V1212, the open collector of the comparator 1211 is turned on, and the transistor 1207 is turned on.
When the voltage of the shunt resistor R1210 becomes higher than the voltage of the first reference voltage source V1212, the open collector of the comparator 1211 is turned off, and the transistor 1207 is turned off.
The intermittent flow of current due to the on / off of the high side switch is smoothed (limited) by the choke coil L1209 and the diode D1208. Therefore, the semiconductor laser light source 102 is controlled at constant current.
If the reference voltage is increased, the current flowing to the semiconductor laser light source 102 can be increased. Therefore, two reference voltage sources are provided and selectively supplied to the comparator 1211 by the changeover switch 1205.
If a switch is provided on the output side of the choke coil L1209, on / off control of the current flowing through the semiconductor laser light source 102 can be realized. Therefore, the high side switch of the Pch MOSFET 1203 is provided.

FIG. 13 shows a time chart of a control signal output from the laser control unit 504, a reference voltage switching signal output from the gate control unit 1101, a voltage waveform of the gate control signal, and a waveform of current flowing through the semiconductor laser light source 102. FIG. The horizontal axis is time, the vertical axes are (a) and (b) logical values, (c) gate voltage, and (d) current.
(A) of FIG. 13 is a control signal which the laser control unit 504 outputs. At time T615, the logic becomes true, and at time T617, the logic returns to false.
(B) of FIG. 13 is a reference voltage switching signal output from the latch 1204 of the gate control unit 1101. Since the differential operation unit 1201 converts the change in the output signal of the pressure sensor 412 into a pulse signal, the control signal from the latch 1204 becomes logic true at time T615 and returns to logic false at time T616 to the changeover switch 1205 It is output.
(C) of FIG. 13 is a gate control signal which the sequencer 1202 of the gate control unit 1101 outputs. The Pch MOSFET 1203 has such a waveform because the source-drain is turned on when the gate voltage is lowered. Note that due to the restriction of the gate-source voltage of the Pch MOSFET 1203, the voltage when the gate voltage is low is not necessarily 0V. A gate control signal having a short on time (irradiation time T1302) is repeatedly output to the Pch MOSFET 1203 from time T615 until time T616 when the pulse signal output from the differential operation unit 1201 is input. From time T616, until the time T617 at which the control signal output from the laser control unit 504 returns to logic false, a continuous gate control signal (irradiation time T1305) is output to the Pch MOSFET 1203 via the laser light pause interval T1304.

FIG. 13D is a waveform diagram of the current flowing to the semiconductor laser light source 102. Further, this waveform diagram is also a waveform diagram of the power supplied to the semiconductor laser light source 102.
By switching the reference voltage and generating a gate control signal for the Pch MOSFET 1203, as shown in (d) of FIG. 13, the semiconductor laser light source 102 has a current I1301 in the semiconductor laser light source 102 from time T615 to time T616. The flowing, intense laser light is applied to the solder ball 201 in a pulsed manner.
When the solder ball 201 is melted, the melted solder is discharged from the discharge port 107 d by the pressure of nitrogen gas in the laser soldering apparatus 101. At that moment, that is, at time T616, the pressure of the nitrogen gas inside the laser soldering apparatus 101 sharply decreases.

When the gate control unit 1101 detects a change in pressure of nitrogen gas from the signal of the pressure sensor 412 by the differential operation unit 1201, the gate control unit 1101 controls the changeover switch 1205 to connect the reference voltage source connected to the negative terminal of the comparator 1211 Switching from one reference voltage source V1212 to a second reference voltage source V1213. The sequencer 1202 receives the pulse signal input from the differential operation unit 1201 at time T616, and switches the gate control signal from the intermittent gate control signal to the continuous gate control signal. Therefore, the Pch MOSFET 1203 is supplied with a continuous gate control signal. As a result, after time T616, a current I1306 smaller than the current I1301 flowing from time T615 to time T616 flows in the semiconductor laser light source 102, and the melted solder and the soldering portion 415a are heated.

In the step of melting the solder balls 201 (between time T615 and time T616), it is necessary to provide the solder balls 201 with a heat quantity necessary for the solder balls 201 cooled to room temperature to become liquid. However, when a strong laser beam is continuously irradiated to the solder ball 201, unevenness occurs in heat transfer, and a state occurs in which a part of the solder ball 201 is melted but a part is not melted. sell. Therefore, in order to uniformly transmit the heat of the laser beam to the entire solder ball 201, the pulse-like strong laser beam is intermittently (intermittently) applied to the solder ball 201. For example, the irradiation time T1302 of the pulsed laser light is set to 10-50 mmsec, the time interval T1303 between pulses and pulses is set to 10-20 mmsec, and the intensity of the pulsed laser light is set to 15-25 W.
The above-mentioned pulse interval, the number of pulses, and the intensity of the pulsed laser light are one example, and may be changed according to various conditions such as the material characteristics of the used solder, the flying distance of the melted solder, and the used laser. For example, the irradiation time T1302 can be narrowed to increase the number of pulses, or the pulse number can be reduced to increase the irradiation time T1302, or the pulse time interval T1303 can be changed accordingly or independently. is there.

In the step of heating after the molten solder adheres to the soldering point 415a (between time T616 and time T617), an alloy of the soldering point 415a and the molten solder is formed, and the molten solder 702 goes to the soldering point 415a. It is necessary to keep the molten solder 702 and the soldering point 415a heated for a predetermined time or more for a predetermined time, in order to stabilize the electrical characteristics by sufficiently wetting and flowing the molten solder to the soldering point 415a by capillary action. is there. However, the melted solder already has a corresponding amount of heat. For this reason, if the molten solder and the soldering point 415a are heated with a strong laser beam used in the step of melting the solder ball 201, the heating may be excessive and the printed pattern of the printed circuit board may be damaged. . In order to form an alloy of the soldering portion 415a and the molten solder, it is desirable to continuously irradiate a laser beam which is weaker than in the step of melting the solder ball 201.

In the present embodiment, a soldering system 401 comprising a laser soldering apparatus 101 and a controller 402 has been disclosed.
The soldering system 401 according to the embodiment of the present invention continues heating the molten solder 702 by continuing to irradiate the molten solder 702 with the laser beam B 701 even after the molten solder 702 adheres to the soldering point 415 a. . By this treatment, an alloy of the soldering point 415a and the molten solder 702 is formed, the molten solder 702 is sufficiently wetted to the soldering point 415a, and the molten solder 702 flows to the soldering point 415a by capillary action. And strong and stable soldering is completed.

As mentioned above, although the embodiment of the present invention was described, the present invention is not limited to the above-mentioned embodiment, and other modifications and applications can be made without departing from the gist of the present invention described in the claims. Includes an example.

101 ... laser soldering apparatus, 102 ... semiconductor laser light source, 103 ... laser lens barrel, 104 ... first reflecting mirror, 105 ... main body, 106 ... second reflecting mirror, 107 ... solder holder, 108 ... holder holding section, 109 ... Solder supply device, 110 ... Conduit, 111 ... Gas inlet, 112 ... Solder ball tank, 113 ... Solder roller, 114 ... Solder passage sensor, 201 ... Solder ball, 401 ... Soldering system, 402 ... Control device, 403 ... Bus, 404, CPU, 405, ROM, 406, RAM, 407, non-volatile storage, 408, input port, 409, output port, 410, timer, 411, object sensor, 412, pressure sensor, 413, stepping motor, 414: Nitrogen gas valve, 415: object to be soldered, 415a: soldering Reference numeral 501 ... D flip flop, 502 ... AND gate, 503 ... comparator, 504 ... laser control unit, 505 ... motor control unit, 506 ... pressure threshold, 507 ... valve control unit, 901 ... solder holder, 1101 ... gate control unit 1102 Laser drive unit 1201 Differential operation unit 1202 Sequencer 1203 Pch MOSFET 1204 Latch 1205 Selector switch 1207 Transistor 1211 Comparator D1208 Diode L1209 Choke coil R1210 Shunt Resistance, R1214: Base resistance, R1215: Resistance, V1206: DC power supply, V1212: First reference voltage source, V1213: Second reference voltage source, 1401: CMOS image sensor, 1402: Objective lens, 1403: Cover 1404 ... flexible printed circuit board, 1405 ... ground node terminal, 1406 ... signal terminals, 1407 ... signal terminal

Claims

Solder holder,
A solder supply device for supplying solder to the solder holder;
A semiconductor laser light source which intermittently irradiates a laser beam of a first intensity for a predetermined time to the solder for melting the solder held by the solder holder which is separated by a predetermined distance from the object to be soldered;
A gas valve for controlling the injection of pressure gas into the solder holder for injecting molten solder from the solder holder;
A soldering apparatus comprising: a pressure sensor for detecting the pressure of the pressure gas in the solder holder;
After the solder reaches the solder holder, the pressure sensor detects that the pressure in the soldering apparatus has reached a predetermined value, and turns on the semiconductor laser light source and controls the gas valve to close. After the solder is ejected from the solder holder, the solder is continuously irradiated with laser light of a second intensity which is weaker than the first intensity for a predetermined time, and then the semiconductor laser light source is controlled to be off. A control system for controlling the opening of the gas valve.
The semiconductor laser light source emits a blue laser.
The soldering system according to claim 1.
The solder is a solder ball,
The soldering system according to claim 2.
Supplying solder to the solder holder;
Injecting a pressure gas into the solder holder for injecting molten solder from the solder holder;
A laser beam of a first intensity is intermittently applied to the solder for a predetermined time from a semiconductor laser light source to melt the solder and change it into molten solder, thereby discharging the molten solder from the solder holder Attaching to the object to be soldered;
A step of continuously irradiating a laser beam of a second intensity weaker than the first intensity from the semiconductor laser light source continuously for a predetermined time to the molten solder attached to the object to be soldered .
The semiconductor laser is a blue laser.
The soldering method according to claim 4.
The solder is a solder ball,
The soldering method according to claim 5.