JPH06216516A - Soldering method for electronic part - Google Patents

Abstract

PURPOSE:To perform soldering securely preventing it from being a batch type and preventing external forces from being applied to leads, at the time of performing soldering without flux. CONSTITUTION:Parts of the wiring pattern 32 of a board 31 to be the vicinities of lead tips are heated hotter than the melting temperature of solder. Temperatures in the vicinities of the boundaries between the tips of external leads 34 and the wiring pattern 32 become higher than the solder melting temperature, and the surface oxide films between the external leads 34 and the wiring pattern 32 are removed. Accordingly, it becomes possible to perform soldering removing oxide films on surfaces to be joined without using flux.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of soldering an electronic component in which an external lead of the electronic component is joined to a circuit pattern on a board.

[0002]

2. Description of the Related Art Conventionally, in order to solder an external lead of an electronic component to a circuit pattern on a board, oxides generated on the bonding surface, adhering water, oils and fats, etc. are activated to activate the bonding surface. It was removed by using flux to clean the joint surface.

However, since the residual flux after soldering may corrode and damage the parts, the residual flux must be removed by cleaning the board after soldering. Since this cleaning must use a CFC-based cleaning solution, it is desired to avoid it as much as possible.

Therefore, in order to meet the above-mentioned demands by performing soldering without using flux, a method shown in FIGS. 6 to 9 has been proposed. FIG. 6 shows Japanese Patent Laid-Open No. 4-2201.
It is a schematic block diagram for demonstrating the conventional soldering method shown by the 69th publication. In this example, an ion beam was used to activate the bonded surface.

In FIG. 6, reference numeral 1 is a Si chip, 2 is a Pb-Sn alloy solder bump formed in large numbers on the Si chip 1, 3 is a ceramic substrate to which the Si chip 1 is soldered, and 4 is this ceramic. A large number of Au electrodes are formed on the substrate 3. An atom source 5 irradiates the silicon chip 1 and the ceramic substrate 3 with the ion beam 6. That is, by irradiating the Pb—Sn alloy solder bump 2 and the Au electrode 4 with the ion beam 6, their surfaces are activated.

FIG. 7 is an enlarged cross-sectional view of an apparatus used when carrying out the conventional soldering method disclosed in Japanese Patent Laid-Open No. 2-41772. In FIG. 7, reference numeral 7 is a substrate, 8 is a beam lead soldered to the substrate 7, and a chip 9 is bonded to the beam lead 8 in advance. Reference numeral 10 denotes a bonding head, which has a structure for adsorbing and holding the chip 9 and is configured so that hot air is supplied from above to a cavity 11 located at the outer peripheral portion and opening downward. ing.

To solder the beam lead 8 to the substrate 7, hot air is blown out from the cavity 11 while the beam lead 8 is in contact with the solder mound 12 on the substrate 7. The hot air is blown out at a flow velocity and a flow rate that are sufficient to scatter the oxide film on the surfaces to be joined, and at a temperature at which the solder mound 12 can be melted, activation and joining of the surfaces to be joined are performed simultaneously. I was going.

FIG. 8 is a schematic configuration diagram of an apparatus used when carrying out the conventional soldering method disclosed in Japanese Patent Laid-Open No. 62-144871. In the figure, 13 is a printed circuit board, and 14 is a chip component soldered to the printed circuit board 13. Reference numeral 15 is a cover for covering the chip component 14 to keep the soldered portion in an inert gas atmosphere. Argon gas mixed with hydrogen gas is introduced into the cover 15. Reference numeral 16 is a laser oscillator, and 17 is a converging lens for converging the laser beam 18 and irradiating the soldered portion 19 with it. And
In this example, by irradiating the soldered portion 19 with the laser beam 18, the solder (not shown) is heated and melted to be soldered. Further, in activating the surfaces to be joined, the reducibility of hydrogen was utilized.

FIG. 9 is a schematic block diagram of an apparatus used for carrying out the conventional soldering method disclosed in Japanese Patent Laid-Open No. 3-145192. In the figure, 20 is a printed circuit board, 21 is an electronic component to be soldered on the printed circuit board 20, and 22 is a lead terminal of the electronic component 21.
Reference numeral 23 is a chamber in which the printed circuit board 20 and electronic components 21 are loaded, and a non-oxidizing gas 24 is introduced into the chamber 23. 25 is irradiated to the soldering portion (the lead terminal 22) and soldered (not shown)
Is a nozzle for supplying a laser beam for heating and melting, and a reducing liquid 27 such as glycerin to the soldering portion 26.

In this example, the reducing liquid 27 is used instead of the flux for soldering. That is, by irradiating the soldering portion with the laser beam 25, the solder is heated and melted to perform soldering,
The surfaces to be joined were activated by supplying the reducing liquid 27 during soldering.

[0011]

[Problems to be Solved by the Invention] The reason why soldering is performed without flux cleaning is not only for the purpose of not using a CFC-based cleaning liquid, but also for electronic components having fine leads by soldering. This is so that it can be implemented in the etc. That is, the leads used in the TCP (chip carrier package) are made of electrolytic copper foil and have a lead pitch of 250 μm and a lead width of 100 μm. Are likely to remain, and will be cut off if washed strongly.

However, when soldering is performed without using flux, if the method shown in FIG. 6 is adopted, there is a problem that the apparatus is of batch type, which is not suitable for mass production. Further, if the method shown in FIG. 7 is adopted, the usable beam leads 8 are limited. That is, when the thin and narrow beam lead 8 is used as described above, the beam lead 8 is cut by the hot air.

Further, as shown in FIG. 8, if only the reducing property of hydrogen is used for activating the surfaces to be joined, the activating power is weak and the soldering cannot always be performed reliably. Since the method shown in FIG. 9 uses the reducing liquid 27 instead of the flux, cleaning after soldering is required.

The present invention has been made to solve the above problems, and when soldering without using a flux or the like, there is no need to use a batch system or apply an external force to the leads. Moreover, it is an object of the present invention to obtain a soldering method capable of surely soldering.

[0015]

According to a first aspect of the invention, there is provided a method of soldering an electronic component, which heats a portion of a pad portion of a substrate near a tip of a lead to a temperature higher than a solder melting temperature.

A soldering method for an electronic component according to a second aspect of the present invention is the same as the first aspect, wherein the light beam has an energy density with which the irradiated portion is heated to a temperature higher than the solder melting temperature,
This light beam is first irradiated to a portion in the vicinity of the tip of the lead in the pad portion, and then scanned toward the base side of the lead.

A third aspect of the invention is a method of soldering an electronic component according to the first aspect of the invention, wherein the light beam has a low energy beam having an energy density that melts the solder and is irradiated to substantially the entire soldered portion. , A high energy beam having an energy density set higher than that of the low energy beam by irradiating a portion of the pad portion near the tip of the lead together with the low energy beam.

[0018]

The temperature near the boundary between the lead tip and the pad becomes higher than the solder melting temperature, and the surface oxide film of the solder interposed between the lead and the pad is removed.

[0019]

EXAMPLES Example 1. An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a state in which an electronic component soldering method according to the present invention is being carried out, and FIG. 2 is a sectional view of the same. In these figures,
Reference numeral 31 is a substrate, and a wiring pattern 32 as a pad portion for soldering an electronic component is formed on the upper surface of the substrate 31. The wiring pattern 32 has a pattern width of 15
The thickness is 0 micron, and the surface thereof is plated with solder having a thickness of 15 microns.

Reference numeral 33 is an electronic component mounted on the substrate 31. The electronic component 33 is a 576-pin TCP in this embodiment, and a large number of external leads 34 are provided on two sides. The lead pitch of the external leads 34 is 25
0 micron, lead width 100 micron, lead thickness 3
It has a thickness of 5 μm and is plated with a solder having a thickness of 7 μm. The external lead 34 has a cross-sectional shape as shown in FIG. 2, and is inclined from the base end portion 34a pulled out from the package of the electronic component 33 and the base end portion 34a via the shoulder bend portion 34b. It is formed of a hanging portion 34c and a tip portion 34e extending from the hanging portion 34c in a substantially horizontal direction via a foot curved portion 34d.

Reference numeral 35 is a collet for making the soldering part a mixed atmosphere of nitrogen gas and hydrogen gas, and is a box-shaped main body 35a for covering the package part of the electronic component 33 from above.
And the external lead 3 attached to the side of the main body 35a.
4 and a lead cover 35b that covers the upper part of the wiring 4. The lead cover 35 is made of quartz glass that can transmit a laser beam.

Reference numeral 36 denotes a gas supply pipe for introducing a mixed gas of nitrogen gas and hydrogen gas into the main body 35a of the collet 35, and the end portion where the gas outlet 36a is opened is the main body 3
It is fixed to the upper surface of 5a substantially at the center thereof. The mixed gas supplied to the gas supply pipe 36 is a mixed gas of 95% concentration nitrogen and 5% concentration hydrogen.

Reference numeral 37 denotes a laser beam. This laser beam 37 is a laser oscillator, for example, a YAG laser with a Q switch (output: 12 W, condensing diameter 100 μm, scanning method:
Galvano scanner) oscillates. Then, in the present embodiment, the scanning start is delayed with respect to the laser irradiation start so that the stationary beam is used in the initial irradiation and the scanning beam is used thereafter. Further, the energy density of the laser beam 37 is set to a value at which the temperature of the irradiated portion is heated to a temperature higher than the solder melting temperature.

Next, the procedure for soldering will be described. First, the external leads 34 of the electronic component 33 are positioned and placed on the solder-plated wiring pattern 32. Then, as shown in FIG.
5 and the mixed gas from the gas supply pipe 36 to the collet 35.
Introduce inside. At this time, the mixed gas flows into the gas outlet 36a.
From the collet 35 into the main body 35a,
Since it flows from the inside to the space below the lead cover 35b, almost the entire area surrounding the electronic component 33 becomes a mixed atmosphere of nitrogen gas and hydrogen gas.

After this, the laser beam 37 is focused to a width of the lead and is irradiated onto a portion on the upper surface of the wiring pattern 32, which is 0.1 mm away from the tip of the lead. The irradiation position (initial irradiation position) at this time is indicated by A in FIG.
At this time, the laser beam 37 emits the collet 35.
The lead cover 35b is transmitted from above.

After irradiating the above-mentioned irradiation initial position for 10 ms, the laser beam 37 is scanned from the front end 34e of the external lead 34 toward the base end 34a with the position as a starting point. The scanning of the laser beam 37 is performed at a scanning start timing of the galvano scanner 10 times from the start of laser oscillation.
The delay is set by ms and the scanning speed by the galvano scanner is set to about 10 cm per second.
That is, with the lead tip 0.1 mm before as the starting point, the scanning speed by the galvano scanner is set to about 10 cm per second, and the scanning start by the galvano scanner is set to 1
When the laser is oscillated for 10 ms with a delay of 0 ms, the laser beam 37 is irradiated to the position indicated by A in the figure, and 1 is emitted at that position.
After resting for 0 ms, scanning is performed along the external lead 34 as shown by the arrow in the figure.

By keeping the laser beam 37 stationary at the irradiation initial position A for a predetermined time (10 ms in this embodiment) as described above, that portion is heated to a temperature higher than the solder melting temperature. Then, by scanning the laser beam 37 up to the base end portion 34a of the external lead 34, the solder (not shown) interposed between the wiring pattern 32 and the external lead 34 is heated and melted. At this time, since the laser beam 37 moves at a relatively high speed, the amount of heat input to the irradiated portion is small and the temperature is lower than when the laser beam 37 is stationary. The laser oscillation is the laser beam 3
7 is scanned to the base end portion 34a and then stopped. As a result, the melted solder is solidified.

Further, since the solder is heated and melted in the mixed atmosphere of nitrogen gas and hydrogen gas, the solder is not oxidized due to the extremely low oxygen concentration. The oxide film on the surface is reduced.

After soldering one of the external leads 34 in this manner, the substrate 31 is translated by one pitch of the external leads 34. Then, the external lead 34 located next to the external lead 34 previously soldered is soldered by the procedure described above. By repeating this operation, the 576-pin external lead 34 is sequentially soldered.

Therefore, the portion of the wiring pattern 32 near the tips of the external leads 34 is heated to a temperature higher than the solder melting temperature, and the wiring pattern 32 and the external leads 3 are heated.
The solder is heated and melted in a state in which the surface oxide film of the solder interposed between the solder and 4 is removed by the heat.

In the above embodiment, a single laser beam 37 is used and the laser beam 37 is scanned for each external lead 34. However, a plurality of laser beams 37 are simultaneously oscillated and the external leads 34 are oscillated simultaneously. It is also possible to solder a plurality of 34 at the same time. Even in this case, the same effect as that of the above embodiment can be obtained. In any case, a mask can be used to limit the irradiation portion of the laser beam 37.

Example 2. In the first embodiment, the external leads are soldered one by one with the laser beam focused to the width of the external leads. However, as shown in FIG. 3, the external leads are focused in a slender linear shape in the juxtaposed direction. You can also let it.

FIG. 3 is a perspective view showing another embodiment in which a laser beam is scanned for soldering. In FIG. 3, the same or equivalent members as those described in FIGS. 1 and 2 are designated by the same reference numerals. The detailed description is omitted. Figure 3
In FIG. 3, the atmosphere forming collet and the like are omitted. In FIG. 3, reference numeral 41 is a linear beam formed by shaping the laser beam into a slender linear shape in the direction in which the external leads 34 are arranged.
The linear beam 41 is configured such that a plurality of (three in the embodiment) external leads 34 are simultaneously irradiated.
The irradiation initial position of this linear beam 41 is shown by hatching in FIG.

In the present embodiment, the linear beam 41 is scanned and soldered in the same manner as in the example shown in FIGS. That is, this embodiment is effective when the substrate 31 is made of ceramic or the like and the damage to the substrate due to the laser beam does not pose a problem, and a plurality of external leads 34 can be soldered at the same time. The soldering efficiency can be improved.

Also in this embodiment, it is possible to heat only the external leads 34 using a mask (not shown).

Example 3. In each of the above-described embodiments, the laser beam is scanned along the external lead, but soldering may be performed without scanning as shown in FIGS. 4 and 5. FIG. 4 is a perspective view showing another embodiment in which soldering is performed in the longitudinal direction of the external lead without using the elongated linear beam for scanning, and FIG. 5 is a strip beam with a wide width in the longitudinal direction and the juxtaposed direction of the external lead. FIG. 11 is a perspective view showing another embodiment in which soldering is performed without scanning using. In these figures, the same or equivalent members as those described in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted. The atmosphere forming collet and the like are omitted in FIGS. 4 and 5.

In FIG. 4, reference numeral 51 is a linear beam,
This linear beam 51 converts the laser beam into the external lead 34.
Is shaped to be elongated in the longitudinal direction, and a portion from the portion of the wiring pattern 32 in the vicinity of the tip of the lead to the hanging portion 34c of the external lead 34 is simultaneously illuminated. Then, the linear beam 51 is applied to the wiring pattern 32.
In the portion near the tip of the lead (the portion shown by hatching in FIG. 4), the irradiated portion has an energy density at which it is heated to a temperature higher than the solder melting temperature, and in other portions, the energy density is lower than the energy density. It is considered as density. The lower energy density is set to a value sufficient to melt the solder.

That is, the linear beam 51 has a low energy beam having an energy density that melts the solder and is applied to almost the entire soldered portion, and the low energy beam is provided at a portion near the lead tip of the wiring pattern 32. And a high energy beam having an energy density set higher than that of the low energy beam.

When the linear beam 51 thus constructed is used, soldering is performed without scanning. That is, the portion of the wiring pattern 32 near the tips of the external leads 34 is heated to a temperature higher than the solder melting temperature, and at the same time, the solder interposed between the wiring pattern 32 and the external leads 34 is heated and fused. Therefore, the same effect as that of the embodiment shown in FIGS. 1 and 2 can be obtained.

In FIG. 5, reference numeral 61 is a strip beam,
The band-shaped beam 61 is a laser beam that is emitted from the external lead 34.
Is shaped so as to be wide in the longitudinal direction and the juxtaposed direction. The band-shaped beam 61 is also set to have an energy density that melts the solder, and the low-energy beam that irradiates almost the entire soldered portion and the wiring pattern 32.
And a high energy beam having an energy density set to be higher than that of the low energy beam. The area irradiated with this high energy beam is shown by hatching in FIG.

With this structure, a plurality of external leads 34 can be soldered simultaneously as compared with the embodiment shown in FIG. 4, so that the soldering efficiency can be improved. As the substrate 31, a substrate formed of ceramic or the like, which does not cause a problem of substrate damage due to a laser beam, is used.

In the embodiments shown in FIGS. 4 and 5, a mask (not shown) can be used to limit the irradiation part.

Example 4. In the third embodiment, the vicinity of the tip of the lead of the wiring pattern 32 is heated by partially increasing the energy density without scanning the laser beam, but the energy density of the laser beam is set low enough to melt the solder. The vicinity of the tip of the lead in the wiring pattern 32 may be colored black. In this way, the laser beam is easily absorbed by the black colored portion, the amount of heat input at that portion increases, and the portion is heated to a higher temperature than other portions. Therefore, the same effect as that of the third embodiment can be obtained.

Example 5. In each of the embodiments described above, the mixed gas of nitrogen gas and hydrogen gas was used to form the low-concentration oxygen atmosphere, but the present invention is not limited to such a limitation, and other gas may be used. You may make it form a non-oxidizing atmosphere.

[0045]

As described above, the method for soldering an electronic component according to the first aspect of the present invention heats a portion of the board pad portion in the vicinity of the lead tip to a temperature higher than the solder melting temperature. In the soldering method for an electronic component according to a second aspect of the present invention, in the first aspect of the present invention, the light beam has an energy density at which the irradiated portion is heated to a temperature higher than the solder melting temperature, and the light beam is first applied to the pad portion. In the first aspect of the invention, the electronic component soldering method according to the third aspect of the invention is to irradiate a portion of the lead near the tip of the lead, and then scan toward the base side of the lead. The beam is a low-energy beam that has an energy density that melts the solder and is applied to almost the entire soldering portion.
Since the portion of the pad portion near the lead tip is irradiated with the low energy beam and is composed of a high energy beam whose energy density is set higher than that of the low energy beam, the vicinity of the boundary between the lead tip and the pad Becomes higher than the melting temperature of the solder, and the surface oxide film of the solder interposed between the lead and the pad is removed.

Therefore, since the soldering can be performed while removing the oxide film on the surfaces to be joined without using the flux, the cleaning step after the soldering can be omitted. Since no external force is applied to the leads of the electronic component, even if the leads are fine electronic components, the leads can be reliably soldered without being cut.

Further, since the electronic parts can be surrounded by a collet or the like for soldering, a mixed atmosphere of an inert gas and a hydrogen gas can be obtained without using a batch system.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which a method for soldering an electronic component according to the present invention is being performed.

FIG. 2 is a cross-sectional view showing a state in which an electronic component soldering method according to the present invention is being performed.

FIG. 3 is a perspective view showing another embodiment in which soldering is performed by scanning a laser beam.

FIG. 4 is a perspective view showing another embodiment in which soldering is performed without scanning by using an elongated linear beam in the longitudinal direction of the external lead.

FIG. 5 is a perspective view showing another embodiment in which soldering is performed without scanning by using a wide band-shaped beam in the longitudinal direction and the juxtaposed direction of the external leads.

FIG. 6 is a schematic configuration diagram for explaining a conventional soldering method disclosed in Japanese Patent Laid-Open No. 4-220169.

FIG. 7 is an enlarged cross-sectional view of an apparatus used when performing the conventional soldering method disclosed in Japanese Patent Laid-Open No. 2-41772.

FIG. 8 is a schematic configuration diagram of an apparatus used when performing a conventional soldering method disclosed in Japanese Patent Laid-Open No. 62-144871.

FIG. 9 is a schematic configuration diagram of an apparatus used when performing a conventional soldering method disclosed in Japanese Patent Laid-Open No. 3-145192.

[Explanation of symbols]

 31 substrate 32 wiring pattern 33 electronic component 34 external lead 35 collet 37 laser beam 41 linear beam 51 linear beam 61 strip beam

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[Procedure amendment]

[Submission date] September 29, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Soldering method for electronic components

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of soldering an electronic component for joining an external lead of the electronic component to a circuit pattern on a board.

[0002]

2. Description of the Related Art Conventionally, in order to solder an external lead of an electronic component to a circuit pattern on a substrate, oxides generated on the bonding surface, adhering water, oils and fats, etc. are activated to activate the bonding surface. It was removed by using flux to clean the joint surface.

[0003] However, since there is a danger that parts by flux residue after soldering is corroded and damaged, solder
After application , the substrate must be washed to remove the residual flux. Since this cleaning must use a CFC-based cleaning solution, it is desired to avoid it as much as possible.

Therefore, in order to meet the above-mentioned demand by performing soldering without using flux, the method shown in FIGS. 6 to 9 has been proposed. FIG. 6 shows Japanese Patent Laid-Open No. 4-2201.
It is a schematic block diagram for demonstrating the conventional soldering method shown by the 69th publication. In this example, an ion beam was used to activate the bonded surface.

[0005] In FIG 6, reference numeral 1 is Si chip, 2 is Pb-Sn alloy solder bumps formed a number on the Si chip 1, the ceramic substrate on which the Si chip 1 is soldered 3, the ceramic 4 A large number of Au electrodes are formed on the substrate 3. An atom source 5 irradiates the silicon chip 1 and the ceramic substrate 3 with the ion beam 6. That is, by irradiating the Pb—Sn alloy solder bump 2 and the Au electrode 4 with the ion beam 6, their surfaces are activated.

FIG. 7 is an enlarged cross-sectional view of an apparatus used when carrying out the conventional soldering method disclosed in Japanese Patent Laid-Open No. 2-41772. 7, reference numeral 7 denotes a substrate, 8 is a beam leads that are soldered to the substrate 7, chip 9 is previously bonded to the beam leads 8. Reference numeral 10 denotes a bonding head, which has a structure for adsorbing and holding the chip 9 and is configured so that hot air is supplied from above to a cavity 11 located at the outer peripheral portion and opening downward. ing.

Then, the beam leads 8 are soldered to the substrate 7.
To biasing it had done blown hot air from the cavity 11 while being Taise' beam leads 8 to the solder mounds 12 on the substrate 7. The hot air is blown out at a flow velocity and a flow rate that are sufficient to scatter the oxide film on the surfaces to be joined, and at a temperature at which the solder mound 12 can be melted, activation and joining of the surfaces to be joined are performed simultaneously. I was going.

FIG. 8 is a schematic configuration diagram of an apparatus used for carrying out the conventional soldering method disclosed in Japanese Patent Laid-Open No. 62-144871. In the figure, 13 is a printed circuit board, 14 is a chip component to be soldered to the printed circuit board 13. Reference numeral 15 is a cover for covering the chip component 14 to keep the soldered portion in an inert gas atmosphere. Argon gas mixed with hydrogen gas is introduced into the cover 15. Reference numeral 16 is a laser oscillator, and 17 is a laser beam 18 which is focused to be soldered.
It is a converging lens for irradiating the attachment part 19. And
In this example, by irradiating the soldered portion 19 with the laser beam 18, the solder (not shown) is heated and melted to be soldered . Further, in activating the surfaces to be joined, the reducibility of hydrogen was utilized.

FIG. 9 is a schematic configuration diagram of an apparatus used for carrying out the conventional soldering method disclosed in Japanese Patent Laid-Open No. 3-145192. In the figure, 20 is a printed circuit board, 21 is an electronic component to be soldered on the printed circuit board 20, 22 denotes a lead terminal of the electronic component 21.
Reference numeral 23 is a chamber in which the printed circuit board 20 and electronic components 21 are loaded, and a non-oxidizing gas 24 is introduced into the chamber 23. 25 is a laser beam for irradiating the soldering part (the lead terminal 22) to heat and melt the solder (not shown), and 26 is a nozzle for supplying a reducing liquid 27 such as glycerin to the soldering part. Is.

In this example, the reducing liquid 27 is used instead of the flux for soldering . That performs soldering by heating and melting the solder by a laser beam 25 to the soldering portion, had to activate the joining surface by supplying the reducing solution 27 at soldering.

[0011]

[Problems to be Solved by the Invention] The reason why soldering is carried out without flux cleaning is not only for the purpose of not using a CFC-based cleaning liquid, but also for electronic parts with fine leads by soldering. This is so that it can be implemented in the etc. That is, the leads used in the TCP (chip carrier package) are made of electrolytic copper foil and have a lead pitch of 250 μm and a lead width of 100 μm. Are likely to remain, and will be cut off if washed strongly.

However, when soldering is carried out without using flux, the method shown in FIG. 6 is not suitable for mass production because the apparatus is of batch type. Further, if the method shown in FIG. 7 is adopted, the usable beam leads 8 are limited. That is, when the thin and narrow beam lead 8 is used as described above, the beam lead 8 is cut by the hot air.

Further, as shown in FIG. 8, if only the reducing property of hydrogen is used for activating the surfaces to be joined, the activating force is weak and the soldering cannot always be performed reliably. Since the method shown in FIG. 9 uses the reducing liquid 27 instead of the flux, cleaning after soldering is required.

The present invention has been made to solve the above problems, and when soldering without using a flux or the like, there is no need to use a batch system or to apply an external force to the leads. in addition, ensure that solder
The purpose is to obtain a soldering method that can be applied.

[0015]

According to a first aspect of the present invention, there is provided a method of soldering an electronic component, which heats a portion of a pad portion of a substrate near a tip of a lead to a temperature higher than a solder melting temperature.

The soldering method of an electronic component according to the second invention, in the first invention, the light beam irradiated portion is the
The energy density is set to a temperature higher than the melting temperature, and this light beam is first irradiated to a portion of the pad portion in the vicinity of the tip of the lead, and then scanned toward the base side of the lead. .

According to a third aspect of the invention, there is provided a method for soldering an electronic component according to the first aspect, wherein the light beam is used to melt the solder.
Irradiate the whole area of the soldering part with the energy density to melt,
Irradiate the part of the pad near the tip of the lead.
The energy density of the light beam
It is a higher price.

[0018]

[Action] temperature of the vicinity of the boundary between the lead tip and the pad solder
Since the temperature is higher than the melting temperature, the surface oxide film of the solder interposed between the lead and the pad is removed.

[0019]

EXAMPLES Example 1. An embodiment of the present invention will be described in detail below with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing a state in which a method for soldering an electronic component according to the present invention is being carried out, and FIG. 2 is a sectional view of the same. In these figures,
Reference numeral 31 is a substrate, and the substrate 31 has an electronic component on its upper surface.
A wiring pattern 32 is formed as a soldering pad portion. The wiring pattern 32 has a pattern width of 15
It is 0 microns, on the surface of thickness 15 microns
Do I plating is applied.

Reference numeral 33 is an electronic component mounted on the substrate 31. The electronic component 33 is a 576-pin TCP in this embodiment, and a large number of external leads 34 are provided on two sides. The lead pitch of the external leads 34 is 25
0 micron, lead width 100 micron, lead thickness 3
It has a thickness of 5 microns and is plated with a solder having a thickness of 7 microns. The external lead 34 has a cross-sectional shape as shown in FIG. 2, and has a base end portion 34a pulled out from the package of the electronic component 33 and the base end portion 34a.
Is formed from a sloping portion 34c that inclines via a shoulder curved portion 34b and a tip end portion 34e that extends substantially horizontally from the sloping portion 34c via a foot curved portion 34d.

Reference numeral 35 denotes a collet for making the soldering part a mixed atmosphere of nitrogen gas and hydrogen gas, and a box-shaped main body 35a for covering the package part of the electronic component 33 from above.
And the external lead 3 attached to the side of the main body 35a.
4 and a lead cover 35b that covers the upper part of the wiring 4. The lead cover 35 is made of quartz glass that can transmit a laser beam.

Reference numeral 36 denotes a gas supply pipe for introducing a mixed gas of nitrogen gas and hydrogen gas into the main body 35a of the collet 35, and the end portion where the gas outlet 36a is opened is the main body 3
It is fixed to the upper surface of 5a substantially at the center thereof. The mixed gas supplied to the gas supply pipe 36 is a mixed gas of 95% concentration nitrogen and 5% concentration hydrogen.

Reference numeral 37 denotes a laser beam. This laser beam 37 is a laser oscillator, for example, a YAG laser with a Q switch (output: 12 W, condensing diameter 100 μm, scanning method:
Galvano scanner) oscillates. Then, in the present embodiment, the scanning start is delayed with respect to the laser irradiation start so that the stationary beam is used in the initial irradiation and the scanning beam is used thereafter. The energy density of the laser beam 37 is set to a value at which the temperature of the irradiated portion is heated to a temperature higher than the solder melting temperature.

Next, the procedure for soldering will be described. First, the external leads 34 of the electronic component 33, positioned on the solder Me <br/> Kkisa the wiring pattern 32, is placed. Then, as shown in FIG.
5 and the mixed gas from the gas supply pipe 36 to the collet 35.
Introduce inside. At this time, the mixed gas flows into the gas outlet 36a.
From the collet 35 into the main body 35a,
Since it flows from the inside to the space below the lead cover 35b, almost the entire area surrounding the electronic component 33 becomes a mixed atmosphere of nitrogen gas and hydrogen gas.

After this, the laser beam 37 is focused to a width of the lead and is irradiated onto a portion on the upper surface of the wiring pattern 32, which is 0.1 mm away from the tip of the lead. The irradiation position (initial irradiation position) at this time is indicated by A in FIG.
At this time, the laser beam 37 emits the collet 35.
The lead cover 35b is transmitted from above.

After irradiating the above-mentioned irradiation initial position for 10 ms, the laser beam 37 is scanned from the front end 34e of the external lead 34 toward the base end 34a with the position as a starting point. The scanning of the laser beam 37 is performed at a scanning start timing of the galvano scanner 10 times from the start of laser oscillation.
The delay is set by ms and the scanning speed by the galvano scanner is set to about 10 cm per second.
That is, with the lead tip 0.1 mm before as the starting point, the scanning speed by the galvano scanner is set to about 10 cm per second, and the scanning start by the galvano scanner is set to 1
When the laser is oscillated for 10 ms with a delay of 0 ms, the laser beam 37 is applied to the position indicated by A in the figure and 1
After resting for 0 ms, scanning is performed along the external lead 34 as shown by the arrow in the figure.

By keeping the laser beam 37 stationary at the irradiation initial position A for a predetermined time (10 ms in this embodiment) as described above, that portion is heated to a temperature higher than the solder melting temperature. Then, by scanning the laser beam 37 up to the base end portion 34 a of the outer lead 34, the solder (not shown) interposed between the wiring pattern 32 and the outer lead 34 is heated and melted. At this time,
Since the laser beam 37 moves at a relatively high speed, the amount of heat input to the irradiated portion is small and the temperature is lower than when the laser beam 37 is stationary. The laser oscillation is stopped after the laser beam 37 is scanned up to the base end portion 34a.
As a result, the melted solder is solidified.

Further, since the solder is heated and melted is a mixed atmosphere of nitrogen gas and hydrogen gas, not the oxygen concentration solder is oxidized to extremely low, moreover, the solder by reduction of the hydrogen The oxide film on the surface is reduced.

As described above, one of the external leads 34 is soldered.
After attached, the substrate 31 is translated by one pitch of the outer leads 34. The external lead 34 is located next to the external leads 34 soldered above is soldered by the procedure described above. By repeating this operation, the 576 pins of the external lead 34 are sequentially soldering.

[0030] Therefore, the site to be near the distal end of the external lead 34 is heated above the solder melting temperature on the wiring pattern 32, the surface of the solder oxide film interposed between the wiring pattern 32 and the external lead 34 is the The solder is heated and melted while being removed by heat.

In the above embodiment, a single laser beam 37 is used and the laser beam 37 is scanned for each external lead 34. However, a plurality of laser beams 37 are simultaneously oscillated and the external leads 34 are oscillated simultaneously. It is also possible to solder a plurality of 34 at the same time. Even in this case, the same effect as that of the above embodiment can be obtained. In any case, a mask can be used to limit the irradiation portion of the laser beam 37.

Example 2. In the first embodiment, has been soldered one by one to an external read laser beam is focused to a width of approximately external lead condenses in an elongated linear shape in the arrangement direction of the outer lead 3 You can also let it.

FIG. 3 is a perspective view showing another embodiment in which soldering is performed by scanning with a laser beam. In FIG. 3, members which are the same as or equivalent to those described in FIGS. , The same reference numerals are given and detailed description is omitted. Figure 3
In FIG. 3, the atmosphere forming collet and the like are omitted. In FIG. 3, reference numeral 41 is a linear beam formed by shaping the laser beam into a slender linear shape in the direction in which the external leads 34 are arranged.
The linear beam 41 is configured such that a plurality of (three in the embodiment) external leads 34 are simultaneously irradiated.
The irradiation initial position of this linear beam 41 is shown by hatching in FIG.

In this embodiment, the linear beam 41 is scanned in the same manner as in the example shown in FIGS. 1 and 2 to perform soldering . That is, this embodiment is effective when the substrate 31 is made of ceramic or the like and the damage to the substrate due to the laser beam does not pose a problem, and a plurality of external leads 34 can be soldered at the same time . The soldering efficiency can be improved.

Also in this embodiment, it is possible to heat only the external leads 34 using a mask (not shown).

Example 3. In each of the above-described embodiments, the laser beam is scanned along the external lead, but soldering may be performed without scanning as shown in FIGS. 4 and 5. FIG. 4 is a perspective view showing another embodiment in which soldering is performed without scanning by using an elongated linear beam in the longitudinal direction of the outer lead, and FIG. 5 is a band-shaped beam wide in the longitudinal direction and the juxtaposed direction of the outer lead. FIG. 9 is a perspective view showing another embodiment in which soldering is performed without scanning using. In these figures, the same or equivalent members as those described in FIGS. 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted. The atmosphere forming collet and the like are omitted in FIGS. 4 and 5.

In FIG. 4, reference numeral 51 is a linear beam,
This linear beam 51 converts the laser beam into the external lead 34.
Is shaped to be elongated in the longitudinal direction, and a portion from the portion of the wiring pattern 32 in the vicinity of the tip of the lead to the hanging portion 34c of the external lead 34 is simultaneously illuminated. Then, the linear beam 51 is applied to the wiring pattern 32.
The energy density at which the irradiated portion is heated to a temperature higher than the melting temperature of the solder is set at a portion in the vicinity of the tip of the lead (a portion shown by hatching in FIG. 4), and at other portions, energy lower than the energy density is set. It is considered as density. The lower energy density is set to a value sufficient to melt the solder .

That is, the linear beam 51 has a low energy beam having an energy density that melts the solder and is applied to almost the entire soldered portion, and the low energy beam is provided at a portion in the vicinity of the lead tip of the wiring pattern 32. And a high energy beam having an energy density set higher than that of the low energy beam.

When the linear beam 51 thus constructed is used, soldering is performed without scanning. That is, the portion of the wiring pattern 32 near the tips of the external leads 34 is heated to a temperature higher than the solder melting temperature, and at the same time, the solder interposed between the wiring pattern 32 and the external leads 34 is heated and fused. Therefore, the same effect as that of the embodiment shown in FIGS. 1 and 2 can be obtained.

In FIG. 5, reference numeral 61 is a strip beam,
The band-shaped beam 61 is a laser beam that is emitted from the external lead 34.
Is shaped so as to be wide in the longitudinal direction and the juxtaposed direction. Then, a low-energy beam irradiated on substantially the entire area of the ribbon beam 61 is also an energy density to melt the solder <br/> soldering portion, the wiring pattern 3
And a high energy beam whose energy density is set to be higher than that of the low energy beam. The area irradiated with this high energy beam is shown by hatching in FIG.

[0041] With this configuration, it is possible to simultaneously <br/> soldering a plurality of external leads 34 as compared with the embodiment shown in FIG. 4, it is possible to improve the efficiency soldering. As the substrate 31, a substrate formed of ceramic or the like, which does not cause a problem of substrate damage due to a laser beam, is used.

In the embodiments shown in FIGS. 4 and 5, a mask (not shown) can be used to limit the irradiation part.

Example 4. In the third embodiment, the vicinity of the tip of the lead of the wiring pattern 32 is heated by partially increasing the energy density without scanning the laser beam, but the energy density of the laser beam is set low enough to melt the solder. The vicinity of the tip of the lead in the wiring pattern 32 may be colored black. In this way, the laser beam is easily absorbed by the black colored portion, the amount of heat input at that portion increases, and the portion is heated to a higher temperature than other portions. Therefore, the same effect as that of the third embodiment can be obtained.

Example 5. In each of the embodiments described above, the mixed gas of nitrogen gas and hydrogen gas was used to form the low-concentration oxygen atmosphere, but the present invention is not limited to such a limitation, and other gas may be used. You may make it form a non-oxidizing atmosphere.

[0045]

As described above, the electronic component soldering method according to the first aspect of the present invention heats a portion of the pad portion of the substrate near the lead tips to a temperature higher than the solder melting temperature. solder the electronic component according to a second aspect of the present invention
Method with it, in the first aspect of the present invention, a light beam with an energy density of the irradiated portion is heated above the solder melting temperature, the light beam, first, the portion which becomes the vicinity of the lead tip in the pad portion Irradiation is performed, and then scanning is performed toward the base side of the lead. The soldering method for an electronic component according to a third aspect of the invention is the soldering portion according to the first aspect of the invention, with an energy density for melting the solder. of
Irradiate the entire area and keep it in the vicinity of the lead tip in the pad area.
The energy density of the light beam applied to the
Since the temperature is higher than the energy density, the temperature near the boundary between the lead tip and the pad becomes higher than the solder melting temperature,
The surface oxide film of the solder interposed between the lead and the pad is removed.

[0046] Thus, since it is possible to perform soldering while removing the oxide film on the surface to be bonded without using a flux, it is possible to omit the cleaning step after soldering. Since no external force is applied to the leads of the electronic component, even if the leads are fine electronic components, the leads can be reliably soldered without being cut.

[0047] In addition, solder around the electronic components in the collet, etc.
Since addition can be performed, a mixed atmosphere of an inert gas and hydrogen gas can be obtained without using a batch method.

[Brief description of drawings]

FIG. 1 is a perspective view showing a state in which an electronic component soldering method according to the present invention is being performed.

FIG. 2 is a cross-sectional view showing a state in which a method for soldering an electronic component according to the present invention is being performed.

FIG. 3 is a perspective view showing another embodiment in which soldering is performed by scanning a laser beam.

FIG. 4 is a perspective view showing another embodiment in which soldering is performed without scanning using an elongated linear beam in the longitudinal direction of the external lead.

FIG. 5 is a perspective view showing another embodiment in which soldering is performed without using a wide band-shaped beam in the longitudinal direction of the external leads and a direction in which the external leads are arranged, without scanning.

FIG. 6 is a schematic configuration diagram for explaining a conventional soldering method disclosed in Japanese Patent Laid-Open No. 4-220169.

FIG. 7 is a diagram showing a conventional structure disclosed in Japanese Patent Application Laid-Open No. 2-41772.
It is an expanded sectional view of the apparatus used when implementing a soldering method.

FIG. 8 is a schematic configuration diagram of an apparatus used when performing a conventional soldering method disclosed in Japanese Patent Laid-Open No. 62-144871.

FIG. 9 is a schematic configuration diagram of an apparatus used when performing a conventional soldering method disclosed in Japanese Patent Laid-Open No. 3-145192.

[Explanation of Codes] 31 Substrate 32 Wiring Pattern 33 Electronic Component 34 External Lead 35 Collet 37 Laser Beam 41 Linear Beam 51 Linear Beam 61 Strip Beam

Front page continuation (72) Inventor Shoji Yoshida 1-1-1, Imajuku Higashi, Nishi-ku, Fukuoka City, Fukuoka Prefecture Mitsubishi Electric Corporation Fukuoka Factory (72) Inventor Mitsuya Hashii 4-1-1 Mizuhara, Itami City, Hyogo Mitsubishi Electric Corporation Company Kita Itami Works

Claims (3)

[Claims] 1. A method of soldering an electronic component, wherein a lead of an electronic component is placed on a pad portion of a substrate, and a solder interposed between the two is heated and melted by a light beam. A method for soldering an electronic component, comprising: heating a solder to a temperature higher than a melting temperature of the solder. 2. The electronic component soldering method according to claim 1, wherein the light beam has an energy density at which the irradiated portion is heated to a temperature higher than the melting temperature of the solder, and the light beam is first applied to the leads in the pad portion. A method of soldering an electronic component, which comprises irradiating a portion near a tip for a predetermined time, and then scanning along a lead toward a base side of the lead. 3. The electronic component soldering method according to claim 1, wherein the light beam has a low energy beam having an energy density that melts the solder and is irradiated to substantially the entire soldering portion, and a tip of the lead in the pad portion. And a high energy beam having an energy density set to be higher than that of the low energy beam.