JP2011151220A - Flow soldering method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein, for a liquid flux reduced in the amount of a VOC or not using the same, the conventional actual soldering achievement can not be applied to it, because it uses water difficult to evaporate relative to alcohol, and the water content cannot be perfectly removed before input to a jet-flow solder tank, under the pre-heating temperature of the conventional flux. <P>SOLUTION: This flow soldering method is performed as follows. A land 12b of a through-hole of a board 8 and a land 12a of a component mounting surface 10 are irradiated with plasma 1; a metal mask 14 is installed on a soldering surface 11 of the through-hole 9; solder paste 15 is applied through the metal mask 14 by a solder dispenser 16; thereafter an insertion component 17 is mounted from the component mounting surface 10 being a surface opposite to the soldering surface 11 of the board 8; and the board 8 is soldered in a jet-flow solder tank 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention shows a flow soldering method for an electronic circuit board in which molten solder is brought into contact with the electronic circuit board for soldering. In particular, a VOC free flux and a low VOC flux are applied by applying a low VOC solder paste (VOC: Volatile Organic Compounds volatile organic compound) having a volatile organic compound content of 5% by weight or less to the soldering surface of the electronic circuit board. The present invention relates to a method of performing flow soldering of an electronic circuit board at least.

  VOC free flux or low VOC flux is used for flow soldering of electronic circuit boards. However, in the current flow soldering apparatus, it has been difficult to completely remove the moisture of these fluxes applied to the electronic circuit board before the injection of the jet solder bath. The present applicant has already proposed in Japanese Patent Application No. 2008-277950, an unpublished in-house application, for solving the problem that it is difficult to completely remove the moisture of the VOC free flux or the low VOC flux. It is a method of installing a metal mask on the soldering surface of a substrate provided with a through hole, applying a solder paste through the metal mask, mounting an insertion component from the component mounting surface of the substrate, and jetting the substrate This is a flow soldering method in which soldering is performed in a solder bath.

  However, in the flow soldering method described in Japanese Patent Application No. 2008-277950 filed unpublished in-house, soldering is possible without using VOC free flux or low VOC flux. It was also observed that wetting and spreading deficiencies occurred on the lands on the component mounting surface side through the wall surface. However, in consideration of the reliability of solder bonding, it is desirable that the solder paste needs to spread over the entire land on the component mounting surface side.

  This invention solves the said subject, and it aims at providing the flow soldering method in which a solder paste spreads to the land of a component mounting surface.

  In order to achieve the above object, the flow soldering method of the present invention irradiates plasma to the wall land of the through hole of the substrate and the land of the component mounting surface of the substrate, and installs a metal mask on the soldering surface of the substrate. A soldering method in which a solder paste is applied via a metal dispenser with a solder dispenser, an insertion component is mounted from a component mounting surface of the substrate, and the substrate is soldered in a jet solder bath. The solder paste contains 0% by weight <M ≦ 5% by weight of M, which is a volatile organic compound (VOC) having a boiling point of 200 to 300 ° C., and a lead-free solder eutectic alloy and the VOC. The mixed viscosity is 80 to 250 Pa · s.

  Note that the solder paste used here is a solder paste containing VOC greater than 0% by weight and 5% by weight or less, and hereinafter referred to as “low VOC solder paste”.

  As described above, according to the flow soldering method of the present invention, the low VOC solder paste slightly swells on the component mounting surface due to the ballistic effect peculiar to the non-Newtonian fluid and appears on the component mounting surface. Although it is generated, we perform surface modification and surface cleaning by plasma on the land of 0.5 to 2.0 mmΦ through-hole part and the land of the component mounting surface of the board, so that wetting spread and wetting without unevenness are achieved. This enables soldering with good bonding properties.

The flowchart which showed the flow soldering method in Embodiment 1 of this invention Schematic diagram of the plasma generator in Embodiment 1 of the present invention Sectional view showing the configuration in which the plasma generator is installed on the electronic circuit board Figure with metal mask installed on electronic circuit board The figure for demonstrating the solder supply method which dispenses a low VOC solder paste to a through hole The flowchart which showed the flow soldering method in Embodiment 2 of this invention The figure which showed the ultrasonic device which vibrates ultrasonic vibration to a substrate The figure which showed the state where the ultrasonic device is in contact with the substrate The figure which showed an example of the mask shape of a metal mask The figure which showed an example of the mask shape of a metal mask The figure which showed an example of the mask shape of a metal mask The figure which showed an example of the mask shape of a metal mask

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a flowchart showing a flow soldering method according to Embodiment 1 of the present invention.

  First, the overall steps 1 to 5 are outlined, and then described in detail later. Step 1 is a process of irradiating the land of the substrate with plasma. Step 2 is a step of installing a metal mask on the soldering surface of the substrate. Step 3 is a process of applying a low VOC solder paste to the soldering surface of the substrate with a solder dispenser. Step 4 is a process in which the board is turned over so that the component mounting surface of the board is on the upper side and the soldering surface is on the lower side, and the insertion component is mounted on the through hole from the component mounting surface of the board. Step 5 is a process of pre-heating the substrate and performing flow soldering to contact the molten solder in a jet solder bath.

  Next, each step will be described in detail. Step 1 is a process of irradiating the land of the substrate with plasma. The substrate is a substrate used for flow soldering, and has a through hole diameter of 0.5 to 2.0 mmΦ. The plasma irradiates the land on the component insertion surface (hereinafter referred to as “component mounting surface”) of this substrate and the wall surface land of the through hole portion. Details will be described later with reference to the drawings.

  Next, FIG. 2 shows a schematic diagram of the plasma generator according to Embodiment 1 of the present invention. As an example of the plasma generator, the following configuration was used. The dielectric 2 made of ceramic is sandwiched between the dielectric electrodes 3, and an AC voltage of 13.56 MHZ is applied to the dielectric electrodes 3 using the AC generation power supply 4. When the mixed gas 5 having a flow rate ratio of 4:96 of hydrogen and argon is introduced into the flow path in the dielectric 2 by the gas pipe 6, the plasma 1 is obtained from the plasma nozzle port 7.

  FIG. 3 is a cross-sectional view showing a configuration in which the plasma generator is installed on an electronic circuit board. The electronic circuit board 8 (hereinafter referred to as “board 8”) used here has a component mounting surface 10 and a soldering surface 11 through which a through hole 9 is provided. This is a substrate 8 through which a land 12 (a part mounting surface land 12a, a through-hole wall surface land 12b, and a soldering surface land 12c are combined) passes through the surface 11. The substrate 1 is irradiated with plasma 1. Here, the plasma 1 forms a region 13 where the surface of the land 12 is normalized and surface-modified. This region 13 is a portion that occupies an area of at least 1/3 to 1/2 with respect to the entire land 12a on the component mounting surface and the entire through hole wall surface land 12b. The surface modification of the through-hole wall surface land 12b is intended to improve the solder wetting on the land 12a on the component mounting surface when a solder paste is supplied in a subsequent process. If the plasma is applied to a portion occupying at least 1/3 of the entire area of the through-hole wall land 12b from the component mounting surface, the solder can be wetted, and 1/2 of the area of the through-hole wall land 12b can be reduced. Even if plasma irradiation is performed on a larger area than the occupied area, there is no significant change in the solder wet-up state. In other words, the plasma irradiation region was determined because it was in a good state.

  Step 2 is a step of installing a metal mask on the soldering surface of the electronic circuit board. FIG. 4 is a diagram in which a metal mask is installed on the electronic circuit board for explaining the flow soldering method according to the first embodiment of the present invention.

  As shown in a cross-sectional view showing a configuration in which a metal mask is installed on the electronic circuit board of FIG. 4B, the metal mask 14 used here will be described later. An opening shape including the center and covering at least a part of the through hole 9 is shown (as an example, FIG. 4A shows a view showing the opening shape of the metal mask. The white portion A is the opening portion) It is installed on the soldering surface 11 side of the substrate 8.

  In the next step 3, a solder paste is used. Note that the solder paste used here is a solder paste containing VOC greater than 0% by weight and 5% by weight or less, and hereinafter referred to as “low VOC solder paste”.

  Step 3 is a step of applying the low VOC solder paste 15 to the soldering surface 11 of the substrate 8 with the solder dispenser 16. FIG. 5 is a diagram for explaining a solder supply method for dispensing the low VOC solder paste into the through hole, and FIG. 5B shows the state of the applied low VOC solder paste 15.

  The low VOC solder paste 15 used here is a solder paste having a viscosity of 80 to 250 Pa · s containing 5% by weight or less of VOC having a boiling point of 200 to 300 ° C. and a lead-free solder eutectic alloy mixed with VOC. The lead-free solder eutectic alloy in the entire low VOC solder paste 15 is about 90% by weight. By applying this low viscosity VOC solder paste 15 to the soldering surface 11 of the substrate 8, the low VOC solder paste 15 spreads on the land 12 a of the component mounting surface through the wall surface land 12 b of the through hole 9 of the substrate 8. It was. This is due to the ballast effect peculiar to the non-Newtonian fluid, and is because the low VOC solder paste 15 appears on the component mounting surface 10 by slightly swelling from the through hole 9 which is a thin tube.

  Here, in response to the explanation of the ballast effect and the above-described plasma irradiation, the size of the diameter of the through hole 9 of the substrate 8 used this time will be described. In a substrate having a diameter of the through hole 9 smaller than 0.5 mmΦ, even when the plasma is irradiated, the low VOC solder paste 15 passes through the wall surface of the through hole 9 of the substrate 8 and hardly spreads on the land 12a of the component mounting surface 10. It was. When the diameter is larger than 2.0 mmΦ, the low VOC solder paste 15 tends to spread easily through the wall surface of the through hole 9 of the substrate 8 and onto the land 12a of the component mounting surface 10 due to the ballistic effect unique to the non-Newtonian fluid. There was a tendency that there was no effect of surface cleaning and surface modification of plasma 1.

  In general, when the boiling point of VOC generally used for a low VOC solder paste is less than 250 ° C., the escape of VOC becomes intense due to the high heat of the soldering bath for flow soldering, which is a subsequent process. Therefore, the low VOC solder paste 15 passes through the wall surface of the through hole 9 of the substrate 8, and the spread of the component mounting surface 10 on the land 12 a due to the ballast effect becomes insufficient. However, processing to the lands 12a of the component mounting surface 10 with the plasma 1 enables the spread of the lands 12a up to 200 ° C. even if the VOC escapes. If the temperature is lower than 200 ° C., the VOC escape becomes severe as described above, so that the low VOC solder paste 15 is insufficiently spread on the through hole 9 of the substrate 8. Next, when the boiling point is higher than 300 ° C., although the escape of VOC is small, the printed shape of the low VOC solder paste 15 applied to the substrate 8 due to the high heat of the solder bath sags to form bridges and wiggles.

  Further, when the viscosity of the material of the low VOC solder paste is less than 80 Pa · s, the viscosity is too low to obtain a normal printed shape.

  Next, in general, when the viscosity exceeds 200 Pa · s, the viscosity is too high when the lead of the insertion component 17 is inserted from the component mounting surface 10 of the substrate 8 in the next step, and the lead solders the soldering surface 11. The result will be pushed to the side. However, since the interface treatment is performed by plasma 1 to the lands 12a of the component mounting surface 10 and the wall lands 12b of the through holes 9, the low VOC solder paste 15 has good adhesion to the plasma treatment through hole wall lands 12b. It becomes. For this reason, the viscosity of the low VOC solder paste 15 can be increased up to 250 Pa · s with almost no extrusion by the lead. If the viscosity is higher than this, the viscosity is too high when the lead of the insertion component 17 is inserted from the component mounting surface 10 of the substrate 8 which is the next process, and the lead pushes the solder to the soldering surface 11 side. became.

  Similarly, when the thixo ratio, which is an index of the ease of removal from the metal mask of the applied low VOC solder paste, is 0.4 or less, the low VOC solder paste remains on the metal mask 14 and is 0.6 or more. This time, the viscosity of the material did not become 80 Pa · s or more and 200 Pa · s or less.

  Step 4 is a process of turning the substrate 8 upside down so that the component mounting surface 10 of the substrate 8 is on the upper side and the soldering surface 11 on the lower side and mounting the insertion component 17 from the component mounting surface 10 of the substrate 8 to the through hole 9. .

  Step 5 is a process of pre-heating the substrate 8 and performing flow soldering in which the substrate 8 is brought into contact with the molten solder in the jet solder bath 20.

  A specific example of the flow soldering method using the low VOC solder paste according to this flow will be described.

  In the plasma 1, an AC voltage of 13.56 MHZ was applied to the dielectric electrode 3 made of ceramic using an AC generating power source 4. A mixed gas 5 having a flow rate ratio of 4:96 of hydrogen and argon was introduced into the flow path in the dielectric body by the gas pipe 6, and plasma 1 was generated from the plasma nozzle port 7. The plasma nozzle port 7 was installed at a distance of 2 mm from the substrate 8, and the plasma 1 was irradiated for 10 seconds to the land 12 a of the component mounting surface 10 of the substrate 8 and the land 12 b of the through hole 9 having a through hole diameter of 0.8 mmΦ. . Here, the land 1 b of the through hole 9 was irradiated with the plasma 1 in a region slightly larger than 1/3 from the component mounting surface 10. With this plasma 1, the surface 13 of the land 12a and the land 12b was subjected to normalization and surface modification to form a plasma-treated region 13.

  Next, the low VOC solder paste 15 used here was prepared by using 0.5% by weight of glycol ether which is a high boiling point solvent having a boiling point of 270 ° C. as a flux solvent. As an alloy component of the solder, Sn-0.7 wt% Cu eutectic alloy having an average particle size of 28 μm and a distribution of 20 μm to 40 μm was used. These materials were adjusted and kneaded, and those having a paste viscosity of 187 Pa · s and a thixo ratio of 0.47 were used.

  Next, as the metal mask 14, a metal mask 14 that was laser-processed with a thickness of 140 microns was prepared. Here, the mask opening shape of the metal mask 14 is narrower from the back surface (soldering surface) to the front surface (component mounting surface) when the solder paste is applied to the substrate with respect to the cross-sectional area S of one corresponding through hole. The center of the through hole is covered so that a hole is formed, and 30 to 50% of the cross-sectional area S of one through hole is covered. In addition, the opening shape of the metal mask may be one in which the cross-sectional area S of the through hole is equally divided into two so that it wets and spreads over the land of the substrate when the low VOC solder paste is applied, or divided into two. Can be evenly opened. However, when the through-hole diameter of the soldering surface 11 is less than 1 mm, the entire cross-section of the through-hole is covered so as to form a pore, and when the through-hole diameter of the soldering surface 11 is 1 mm or more, the solder filling In the subsequent through hole 9, a mask-shaped one as shown in FIG. 4A was prepared so that pores were formed from the soldering surface 11 to the component mounting surface 10.

  Next, the metal mask 14 was placed on the soldering surface 11 of the substrate 8, and the low VOC solder paste 15 was printed by a printing machine. In any of the above-mentioned diameters, the low VOC solder paste 15 that has flowed out to the component mounting surface 10 side spread on the lands 12a of the component mounting surface 10 due to the ballast effect unique to the non-Newtonian fluid. This cross-sectional state is shown in FIG. Next, the substrate 8 is turned over so that the component mounting surface 10 of the substrate 8 is located on the upper side and the soldering surface 11 is disposed on the lower side. The insertion part 17 was installed in the hole 9.

  Next, the substrate 8 on which the insertion component 17 was mounted was heated, and flow soldering was performed so as to contact the molten solder in a jet solder bath.

  The molten solder used here may be a lead-free solder material. However, if the component of the molten solder in the jet solder bath is made the same as that of the lead-free solder eutectic alloy contained in the low VOC solder paste, the component is mounted because the low VOC solder paste has already been applied to the soldering surface of the board. Good wetting to the surface. Here, the molten solder in the jet solder bath was Sn-0.7 wt% Cu.

  As described above, a low VOC solder paste containing 5% by weight or less of VOC having a boiling point of 200 to 300 ° C. and having a viscosity of 80 to 250 Pa · s mixed with lead-free solder eutectic alloy with VOC is applied to the soldering surface of the substrate. By applying, soldering with good bondability using low VOC became possible.

(Embodiment 2)
FIG. 6 is a flowchart showing a flow soldering method according to Embodiment 2 of the present invention. The flow soldering method according to the second embodiment of the present invention is obtained by adding a step (step A) of applying ultrasonic vibration to the substrate to the above-described flow soldering method according to the first embodiment of the present invention. .

  FIG. 7 is a diagram showing an ultrasonic apparatus for exciting this ultrasonic vibration to the substrate. In FIG. 7, the substrate 8 on which the insertion component 17 is mounted passes through the ultrasonic device 18, the substrate 8 is heated by the preheater 19, contacts the molten solder in the jet solder bath 20, and is cooled by the cooling device 21. It is cooled and soldering is completed.

  First, the plasma 1 is irradiated to the land 12a of the component mounting surface 10 and the wall surface land 12b of the through hole as in the first embodiment (step 1), and then the soldering surface 11 of the substrate 8 is subjected to the metal mask 14. After the step (step 2), the low VOC (volatile organic compound) solder paste 15 is applied to the soldering surface 11 of the substrate 8 with the solder dispenser 16 (step 3), and then the substrate 8 is A step (step 4) is performed in which the substrate 8 is turned over so that the component mounting surface 10 and the soldering surface 11 are located below, and the insertion component 17 is mounted from the component mounting surface 10 of the substrate 8 to the through hole 9.

  The low VOC solder paste 15 used here is a solder paste having a viscosity of 80 to 250 Pa · s containing 5% by weight or less of VOC having a boiling point of 200 to 300 ° C. and a lead-free solder eutectic alloy mixed with VOC. By applying the low VOC solder paste 15 to the soldering surface 11 of the substrate 8, the low VOC solder paste 15 spreads on the land 12 a of the component mounting surface 10 through the wall surface of the through hole 9 of the substrate 8. This is because of the ballast effect peculiar to the non-Newtonian fluid, and the low VOC solder paste 15 comes out on the component mounting surface 10 by slightly expanding from the diameter of the through hole 9 which is a thin tube.

  However, the extra low VOC solder paste 15 applied to the soldering surface 11 may partially hang down from the soldering surface 11. This extra low VOC solder paste 15 deteriorates the wettability of soldering and makes it impossible to obtain a good soldering substrate. Therefore, the ultrasonic device 18 is installed at the inlet of the preheater zone where the substrate 8 is preheated before being introduced into the jet solder bath 20. 8A and 8B are diagrams showing a state in which the ultrasonic apparatus is in contact with the substrate. FIG. 8A is a cross-sectional view, and FIG. 8B is a top view. As shown in FIG. 8, the horn terminal tip 22 of the ultrasonic device 18 is in contact with the component mounting surface 10 side of the center line of the substrate 8 on which the warpage prevention bar is installed on the soldering surface 11 side.

  At this time, the horn terminal tip portion 22 was in contact with the component mounting surface 10 side center line, and was vibrated with ultrasonic waves having a frequency of 2 to 5 kHz and an amplitude of 1 to 10 μm. This makes it possible to remove excess low VOC solder paste 15 by the ultrasonic device 18.

  Here, when the frequency of the ultrasonic vibration is less than 2 kHz, the extra low VOC solder paste 15 cannot be removed from the substrate 8, and when it is greater than 5 kHz, the low VOC applied to the substrate 8. Not only the solder paste 15 is peeled off, but also the inserted inserted component 17 becomes unstable with respect to the substrate 8, and the quality after soldering is lowered.

  A specific example of the flow soldering method using the low VOC solder paste according to the above flow will be described.

  The low VOC solder paste 15 used here was prepared by using 0.4% by weight of dipropylene glycol which is a high boiling point solvent having a boiling point of 280 ° C. as VOC. As an alloy component of the solder, Sn-0.7 wt% Cu eutectic alloy having an average particle size of 29 μ and a distribution of 22 μ to 39 μ was used. These materials were adjusted and kneaded, and those having a paste viscosity of 180 Pa · s and a thixo ratio of 0.52 were used.

  Next, as the metal mask 14, a metal mask 14 that was laser-processed with a thickness of 140 microns was prepared. The metal mask 14 used here was prepared in a mask shape as shown in FIG. 4A used in the first embodiment.

  Next, the metal mask 14 was placed on the soldering surface 11 of the flow substrate, and the low VOC solder paste 15 was applied by a solder dispenser 16. Due to the ballistic effect peculiar to the non-Newtonian fluid, the solder that has flowed out toward the component mounting surface 10 spread on the lands 12a of the component mounting surface 10. The state of this cross section is shown in FIG. Next, the substrate 8 is turned over so that the component mounting surface 10 of the substrate 8 is located on the upper side and the soldering surface 11 is disposed on the lower side. The insertion part 17 was installed in the hole 9.

  When the insertion component 17 was inserted into the through hole 9 from the component mounting surface 10, a part of the excessive low VOC solder paste 15 applied to the soldering surface 11 hanged down from the soldering surface 11. In order to remove this extra low VOC solder paste 15, an ultrasonic device 18 is installed at the inlet of the preheater zone, and the tip of the oscillator horn terminal is in contact with the component mounting surface 10 side of the center line of the substrate 8. Thus, it was vibrated with a frequency of 4 kHz and an amplitude of 2 μm. Due to this vibration, the excessive low VOC solder paste 15 dripping on the soldering surface 11 of the substrate 8 was removed. This board | substrate 8 was immersed in the jet solder tank 20, and the flow soldering was performed.

  As described above, a low VOC solder paste 15 containing VOC having a boiling point of 200 to 300 ° C. and containing 5% by weight or less and having a viscosity of 80 to 250 Pa · s mixed with a lead-free solder eutectic alloy with VOC is soldered to the substrate 8. Applying to the surface 11 and removing the extra low VOC solder paste 15 when the insert 17 is inserted into the through hole 9 from the component mounting surface 10 by applying ultrasonic waves, a good low VOC is used. It was possible to solder.

(Embodiment 3)
A flow soldering method according to Embodiment 3 of the present invention will be described. In the above-described flow soldering methods according to the first and second embodiments of the present invention, the low VOC solder paste 15 is applied after the metal mask 14 is placed on the soldering surface 11 of the substrate 8.

  The metal mask 14 used in the flow soldering method according to Embodiment 3 of the present invention is such that the mask opening shape of the metal mask 14 is such that the solder paste is applied to the substrate with respect to the cross-sectional area S of one corresponding through hole. Cover the center of the through hole and cover 30 to 50% of the cross-sectional area S of one through hole so that pores are formed from the back surface (soldering surface) to the front surface (component mounting surface) when applied. It is characterized by that. When the substrate has a plurality of through holes, the metal mask is provided so as to have the above-described opening shape for all the through holes corresponding to the metal mask 14.

  Further, the opening shape of the metal mask may be one in which the cross-sectional area S of the through hole is equally opened by dividing into four so that the land 12 of the substrate 8 is wet spread when the low VOC solder paste 15 is applied, What divided into 2 and opened equally may be used. However, when the through-hole diameter of the soldering surface 11 is less than 1 mm, the entire cross-section of the through-hole is covered so as to form a pore, and when the through-hole diameter of the soldering surface 11 is 1 mm or more, the solder filling In the subsequent through hole 9, pores are formed from the soldering surface 11 to the component mounting surface 10.

  In addition, the metal mask 14 preferably has an opening shape so that the solder paste 15 can be applied to the land 12, but at least a part of the land 12 covers the center of the through hole. Examples of the mask shape of the metal mask 14 include the shapes shown in FIGS.

  Regardless of the shape, the low VOC solder paste 15 could be raised on the land 12 of the component mounting surface 10 due to the ballast effect.

  Further, the central portion of the through hole 9 that does not supply the low VOC solder paste 15 is formed in the center of the opening of the metal mask 14 to form a pore from the soldering surface 11 to the component mounting surface 10 in the through hole 9. If the mask area is less than 30%, the pores into which the leads of the insertion component 17 can be inserted cannot be formed. If the mask area is greater than 50%, the low VOC solder paste 15 swells on the land 12a of the component mounting surface 10 due to the ballast effect. I could not.

  From this, it can be seen that the optimal size of the metal mask 14 as the mask shape is an opening shape covering 30 to 50% of the cross-sectional area S of the through hole 9, and sufficient wetting after soldering is possible.

  The flow soldering method of the present invention uses a low VOC solder paste, irradiates the substrate with plasma, mounts a metal mask on the soldering surface of the flow substrate, prints the low VOC solder paste, and then mounts the insert part. However, it is a method of soldering in a jet solder bath, and can be applied to a soldered single-sided board, double-sided board, and reflow / flow mixed board. The present invention can be applied not only to the above-mentioned flow board but also to all devices used for soldering by soaking in a so-called solder melting tank, such as a device flow board or a partial dip board using ceramic as a material. .

DESCRIPTION OF SYMBOLS 1 Plasma 2 Dielectric 3 Dielectric electrode 4 AC generating power supply 5 Mixed gas 6 Gas pipe 7 Plasma nozzle port 8 Board | substrate 9 Through hole 10 Component mounting surface 11 Soldering surface 12 Land 13 Area | region 14 Metal mask 15 Low VOC solder paste 16 Solder Dispenser 17 Insertion part 18 Ultrasonic device 19 Pre-heater 20 Jet solder bath 21 Cooling device 22 Horn terminal tip

Claims (4)

After irradiating the wall surface land of the substrate through-hole and the land of the component mounting surface of the substrate with a plasma, setting a metal mask on the soldering surface of the substrate, and applying a solder paste through the metal mask with a solder dispenser ,
A flow soldering method of mounting an insertion part from a component mounting surface of the substrate and soldering the substrate in a jet solder bath,
The solder paste is
Volatile organic compounds (VOC) having a boiling point of 200 to 300 ° C. containing 0 wt% <M ≦ 5 wt%, and a viscosity of 80 to 250 Pa · in which a lead-free solder eutectic alloy is mixed with the VOC s, a flow soldering method. The lead-free solder eutectic alloy contained in the solder paste is
A Sn-0.7 wt% Cu eutectic alloy having a particle size of 10 μm to 40 μm,
The flow soldering method according to claim 1, wherein the solder material of the jet solder bath is Sn—Cu solder. After mounting the insertion component from the component mounting surface of the board,
2. The flow soldering method according to claim 1, wherein after the substrate is vibrated with an ultrasonic wave having a frequency of 2 to 5 kHz and an amplitude of 1 to 10 μm, the substrate is soldered in a jet solder bath. . Metal mask
The opening shape covers the center of one through hole and covers 30 to 50% of the cross-sectional area S of the through hole, and the opening shape for all the through holes of the substrate corresponding to the metal mask. The flow soldering method according to claim 1, wherein:

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