JP4974382B2 - Reflow soldering method and apparatus - Google Patents

Description

  The present invention relates to a reflow soldering method and a reflow soldering apparatus for mounting components on a flexible printed wiring board using a synthetic resin as a base material by irradiating a solder with a laser.

  Conventionally, when a component is mounted on a flexible printed wiring board (hereinafter referred to as FPC), the component is mounted via a lead-free solder paste, and reflow soldering is performed through a reflow furnace. However, lead-free solder has a melting temperature higher than that of lead-containing solder such as Sn—Pb eutectic solder. Therefore, in order to perform reflow soldering appropriately, the temperature of the reflow furnace must be increased. In the reflow soldering method used in the reflow furnace, the entire FPC using a synthetic resin such as PET as the base material is heated at an ambient temperature higher than the melting temperature of the solder, so that the base material may be damaged. is there.

  For example, the solder heat resistance of CCL (Copper clad laminate) using PET (Polyethylene terephthalate), which is a low heat resistant base material, is 210 degrees for 30 seconds, and in the case of 235 degrees, it does not take 1 second. When reflow soldering is performed on this PET-CCL using a reflow furnace, the temperature of the reflow part of the reflow furnace exceeds 230 degrees at the maximum. When such reflow soldering is performed, the PET of the substrate is damaged. Thus, in the method using the reflow furnace, the base material of synthetic resin such as PET may be damaged during reflow soldering.

  As another method for performing reflow soldering, there is a reflow soldering method in which solder is melted by irradiating a solder paste with a laser such as a semiconductor laser. (See Patent Document 1).

  However, in the reflow soldering method in which the solder is melted by irradiating a laser, if the laser irradiation time is too long or the output is too strong, the temperature of the solder exceeds the melting temperature. And when the base material using synthetic resins, such as PET, exceeds heat-resistant temperature by heat conduction, the base material may be damaged.

  For example, in the case of a chip resistor of 3225, reflow soldering can be performed by performing 5 W semiconductor laser irradiation for about 1 second. However, in this case, the heat of the solder is transmitted to the base material, and the base material of the synthetic resin such as PET is damaged. For this reason, in the reflow soldering method in which the solder is melted by irradiating the laser, the irradiation output and the irradiation time must be limited, and the selection range of appropriate manufacturing conditions is narrowed.

  Therefore, the applicant of the present application does not damage the base material even in the case of performing reflow soldering in which the solder is melted by irradiating a laser in the FPC using a synthetic resin such as PET as the base material. A reflow soldering method and a reflow soldering apparatus capable of mounting components have been filed earlier.

  The invention according to the prior application of the applicant of the present application is arranged on the flexible printed wiring board in a reflow soldering method in which a component is mounted on a flexible printed wiring board using a synthetic resin as a base material by irradiating the solder with a laser. This is a method of irradiating the solder with a laser after preheating the solder. The apparatus is as shown in FIGS.

  The apparatus of the prior application shown in FIG. 2 includes a laser beam irradiation unit 11 that irradiates the solder disposed on the FPC 1 with a laser beam, and a heating device 12 for preheating the solder disposed on the FPC. The heating device 12 is configured so that the FPC 1 can be placed thereon, and is configured to heat the placed FPC 1 to about 100 degrees to about 130 degrees. The laser beam irradiation unit 11 is configured such that the irradiation position and irradiation time are controlled by a control device (not shown). Reflow soldering is performed on the FPC 1. Here, the FPC 1 includes a base material 1A and a circuit 1B printed thereon. A synthetic resin such as PET is used for the substrate 1A. The heat resistance temperature of the synthetic resin PET is 230 degrees, and damage is caused when heat exceeding this temperature is applied. A solder paste 2 is disposed on the FPC 1. The solder paste 2 used is lead-free solder, and its melting point is about 220 degrees. On the solder paste 2, terminals 3 of components 4 mounted on the circuit 1B are installed. In this state, when the heating device 12 is heated, the base material 1A, the circuit 1B, the solder paste 2, the terminal 3, and the component 4 using a synthetic resin such as PET are preheated. Thereafter, reflow soldering is performed by directly irradiating the solder paste 2 with laser light. This laser scanning is performed on each solder paste 2 to perform reflow soldering of the entire FPC 1.

The apparatus according to the prior application of FIG. 3 differs from the reflow soldering apparatus (shown in FIG. 2) in that it has a flexible printed wiring board heating unit 13. The flexible printed wiring board heat dissipating part 13 includes a plate 14 made of a porous material, for example, porous aluminum, a housing 15 that holds the plate 14, and a vacuum pump 16 connected to the housing 15. ing. The plate 14 is configured such that the FPC 1 can be placed on the surface. The housing 15 has an opening on the upper surface, and is fixed by the plate 14 so that the opening on the upper surface is closed. A space X is formed in the housing 15 to which the plate 14 is fixed. The housing 15 has a hole 17 communicating with the space X on the side wall thereof, and a vacuum pump 16 is connected to the hole 17. Further, three heaters 18 are provided in parallel in the plate 14 as heating means. The heater 18 is configured to heat the mounted FPC 1 from about 100 degrees to about 130 degrees. Further, a thermocouple 19 for temperature measurement is provided between the heaters 18 arranged in parallel in the plate 14 and in the vicinity of the FPC 1. The thermocouple 19 measures the temperature in the plate 14, and the heater 18 adjusts the temperature based on the measured temperature so that the solder paste 2 on the FPC 1 is heated to about 100 to 130 degrees. Is done. With this reflow soldering apparatus, reflow soldering is performed on the FPC 1. The component mounting portion of the FPC 1 that is laser-scanned is preheated by the heater 18 in the plate 14 provided on the back surface, and the temperature of the solder paste 2 is also increased. Also reach the melting temperature in a short time. For this reason, laser irradiation is completed in a short time, and laser irradiation is completed before the base material 1A on which the synthetic resin such as PET on the back side of the component mounting portion of the FPC 1 is used due to the heat conduction of the solder exceeds the heat resistance temperature. .
Japanese Patent Laid-Open No. 4-91492

  Also in the heating device 12 of the prior application apparatus shown in FIG. 2, the back side of the substrate 1A (for example, PET) is sucked in the same manner as in FIG. 3, and a part of the heat generated by the laser irradiation is wasted. In this method, the entire FPC 1 is preheated (for example, 130 ° C.) and laser irradiation is performed for a certain period of time (for example, 0.1 to 2 seconds), so that the solder temperature is kept at a melting point of 217 ° C. The PET is prevented from reaching 230 ° C. or higher, thereby avoiding damage to the PET. When laser irradiation is actually performed, it is necessary to bring the FPC into close contact with the heat retaining device, so that a suction / heat retaining device as shown in FIG. 3 is necessary. However, in the plate 14 (porous plate) shown in FIG. 3, the temperature variation depending on the location occurs about 20 degrees, so the appropriate reflow condition range is narrowed. Further, the laser irradiation output and irradiation time are greatly affected by the ambient temperature because the object to be soldered is open.

  Accordingly, an object of the present invention is to provide a reflow soldering method and apparatus capable of stabilizing the reflow conditions by controlling the ambient temperature and performing laser irradiation at a constant temperature.

In order to achieve the above-described object, the present invention provides a laser beam in a reflow soldering method in which a component is mounted on a flexible printed wiring board using a synthetic resin having low heat resistance as a base material by irradiating the solder with a laser. the porous plate is arranged at a predetermined height position in the chamber of the small chamber that having a transmitting surface, a step of dividing the small chamber into an upper chamber and a lower chamber by the porous plate, a flexible printed wiring board on the porous plate a step of placing a factory and as you preheat the solder disposed on the flexible printed wiring board in temperature controlled the small chamber, after preheating, through the laser beam transmitting surface from the small outside the solder a melting monkey step solder by irradiating laser, and a step of sucking the air in the lower chamber, when irradiating a laser the solder, the negative pressure of the lower chamber, The serial flexible printed wiring board is fixed to the porous plate, in which through the porous plate to radiate the flexible printed wiring board.
Further, in a reflow soldering apparatus for mounting a component on a flexible printed wiring board using a synthetic resin as a base material by irradiating a laser to the solder , a small chamber in which the laser light transmission plate is attached, and a predetermined chamber in the small chamber A pre-heating for preheating the porous plate on which the flexible printed wiring board is mounted and the porous plate on which the flexible printed wiring board is placed, and the small chamber is divided into an upper chamber portion and a lower chamber portion. A means for irradiating the solder from outside the small chamber through the laser light transmission plate, and a suction means for sucking the air in the lower chamber. In addition, the flexible printed wiring board is fixed to the porous plate by the negative pressure in the lower chamber, and the flexible printed wiring Plate is configured to be dissipated through the porous plate.

According to the method of the present invention eliminates the need to embed a heater port over lath plate, porous plate to provide an inexpensive and preheated at ambient temperature which is managing the solder, since the laser irradiation, the flexible printed wiring board of the group Reliable soldering can be performed quickly without damaging the material.

According to the apparatus of the present invention, equipment also becomes as simple, temperature control is also easy, also improved soldering reliability.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG.

  A flexible printed wiring board (FPC) 1 in FIG. 1 is obtained by printing a circuit 1B on a base material 1A in the same manner as the previous application (FIG. 2). As the substrate 1A, a low heat resistant material such as PET or PEN is used. It is used. When the component 4 is mounted on such an FPC 1, the solder paste 2 is disposed between the terminal 3 and the circuit 1 </ b> B, and the laser light is irradiated from the laser light irradiation unit 11 to the solder paste 2. In FIG. 1, a laser light transmitting plate 21 is detachably attached to the upper surface of a box-shaped housing 20 having an open upper surface made of aluminum to constitute a small chamber that is not easily influenced by the external temperature. A porous plate 22 is provided at a predetermined height in the small chamber, and the FPC 1 is placed on the porous plate 22.

  The porous plate 22 provided in the small chamber was made of aluminum, and had a porous diameter of 15 μm, a size of 200 × 200 (mn) in length and width, and a thickness of 15 mm. The porous plate 22 divides the small chamber into an upper chamber R1 and a lower chamber R2. The upper chamber R1 is provided with an intake port 23 for taking in temperature-controlled hot air, and the lower chamber R2 is provided with a suction port 24 for sucking heat of the upper chamber through the porous plate 22, and the suction port 24 has a vacuum. A pump 25 is connected.

  When the FPC 1 is placed on the porous plate 22 of the housing 20 shown in FIG. 1, hot air is sent from the intake port 23 to the upper chamber R1 to preheat the solder paste 2. The preheated solder paste 2 reaches the melting temperature in a shorter time than when it is not preheated. For this reason, laser irradiation can be completed in a short time, and the laser irradiation is completed before the base material 1A on which the synthetic resin such as PET on the back side of the FPC component mounting portion is used due to the heat conduction of the solder exceeds the heat resistant temperature. . For example, when the entire FPC is preheated to about 120 degrees, the laser irradiation time may be about 0.1 seconds. At this time, although the solder paste 2 melts at a temperature exceeding the melting point, the laser irradiation is finished before the heat is transmitted to the base material 1A using a synthetic resin such as PET, and the base material 1A has a heat resistant temperature. Never exceed. Therefore, reflow soldering can be performed without damaging the substrate 1A using a synthetic resin such as PET.

  The preheating temperature was 130 to 150 ° C., the component 4 was a chip resistor 3225 and an LED 3228, and the suction pressure by the vacuum pump 25 was 20 kpa. The solder paste used was Sn-Ag-Cu.

  When the air in the lower chamber R2 is sucked and becomes negative pressure, the FPC 1 is securely fixed at a predetermined position on the porous plate 22, and in this positioned state, the laser beam is accurately positioned (location of the solder paste 2). ) And reflow soldering can be performed stably. Moreover, heat dissipation (waste heat) can also be performed by the negative pressure in the lower chamber R2. The suction by the vacuum pump 25 is for simultaneously performing positioning of the FPC 1 and heat radiation of the upper chamber R1.

  When positioning the FPC 1 on the porous plate 22, adjustment can be performed while monitoring with a CCD camera, and the accuracy of laser irradiation can be increased.

It is a side conceptual diagram showing the reflow soldering device concerning the form of the embodiment of the present invention. It is a side surface conceptual diagram which shows the reflow soldering apparatus of a prior application. It is a side surface conceptual diagram which shows the reflow soldering apparatus of a prior application.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flexible printed wiring board 1A Board | substrate 1B Circuit 2 Solder paste 3 Terminal 4 Parts 11 Laser beam irradiation part 20 Housing 21 Laser beam transmission board 22 Porous plate R1 Upper chamber R2 Lower chamber

Claims (2)

In the reflow soldering method of mounting a component on a flexible printed wiring board using a low-heat-resistant synthetic resin as a base material by irradiating the solder with a laser,
A step of the porous plate is disposed at a predetermined height position in the chamber of the small chambers that have a laser beam transmitting surface, dividing the small chamber by the porous plate into an upper chamber and a lower chamber,
A step of mounting a flexible printed wiring board on the porous plate,
Engineering and as you preheat the solder disposed on the flexible printed wiring board in temperature controlled the small chamber,
After preheating, melting the solder by irradiating the solder from outside the small chamber through the laser light transmitting surface ;
Sucking air in the lower chamber,
When irradiating the solder with a laser, the flexible printed wiring board is fixed to the porous plate by the negative pressure of the lower chamber, and the flexible printed wiring board is radiated through the porous plate. Reflow soldering method. In reflow soldering equipment that mounts components on a flexible printed wiring board using synthetic resin as a base material by irradiating the solder with a laser,
A chamber to which a laser beam transmitting plate is attached;
A porous plate disposed at a predetermined height in the small chamber, dividing the small chamber into an upper chamber portion and a lower chamber portion, and a porous plate on which the flexible printed wiring board is placed;
Preheating means for preheating the solder of the flexible printed wiring board;
A laser beam irradiation unit that irradiates the solder from outside the small chamber through the laser beam transmitting plate;
A suction means for sucking air in the lower chamber,
When irradiating a laser to the solder, the flexible printed wiring board is fixed to the porous plate by the negative pressure in the lower chamber, and the flexible printed wiring board is radiated through the porous plate. A reflow soldering apparatus characterized by comprising.

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