JP5962123B2 - Component mounting method and component mounting apparatus - Google Patents

Description

  The present invention relates to a component mounting method and a component mounting apparatus.

  In recent years, with the enhancement and miniaturization of electronic devices such as mobile phones and digital cameras, semiconductor devices mounted on electronic devices are required to have higher functionality and higher integration.

  And the dimension of the semiconductor device is reduced, and the space | interval between the terminals of a semiconductor device is also narrowed. Further, the distance between the semiconductor device mounted on the substrate and the substrate is also narrowed.

  Furthermore, the mounting density when electronic components such as semiconductor devices are mounted on a substrate is high, and the interval between electronic components is also narrowed.

  As a method for mounting such an electronic component on a substrate, for example, a surface mounting method is used.

  In the surface mounting method, first, paste solder containing a flux component is applied onto an electrode of a substrate. Next, after an electronic component such as a semiconductor device is bonded onto the substrate via paste solder, the solder is melted and soldered to the electrode of the substrate. Thereafter, the substrate on which the electronic component is mounted is washed with an organic solvent to remove the flux residue from the substrate.

  However, as described above, since the distance between the terminals of the semiconductor device, or between the semiconductor device and the substrate, or between the electronic components is narrow, it is difficult to remove the flux residue attached to these gaps. There is a case.

  Therefore, a method of mounting electronic components using solder that does not contain a flux component by reducing and removing the oxide film formed on the surface of the solder or electrode with formic acid before melting the solder is proposed. ing.

JP 2008-246563 A

  However, in this method of removing the oxide film using formic acid, in order to remove the remaining formic acid from the substrate, air is supplied to the substrate, and the supplied air and formic acid are recovered and burned. . Therefore, since the substrate is in an oxygen atmosphere when the solder is melted, the solder or the electrode may be oxidized again.

  Therefore, an object of the present specification is to provide a component mounting method capable of mounting components on a substrate while suppressing oxidation of electrodes and the like.

  It is another object of the present specification to provide a component mounting apparatus that can mount components on a substrate while suppressing oxidation of electrodes and the like.

  According to one aspect of the component mounting method disclosed in the present specification, a first step of exposing a substrate on which a component is disposed via a solder paste containing solder powder to a reducing atmosphere; A second step of heating, a third step of exposing the substrate to a radical atmosphere, and a fourth step of lowering the temperature of the substrate below the melting point of the solder powder.

  Further, according to one aspect of the component mounting apparatus disclosed in the present specification, a chamber in which a substrate on which a component is disposed via a solder paste containing solder powder is placed, and a temperature for adjusting the temperature in the chamber A regulator, a reducing agent supply unit that supplies a reducing agent into the chamber, a radical supply unit that supplies radicals into the chamber, and controls the reducing agent supply unit to expose the substrate to a reducing atmosphere. In addition, the temperature adjusting unit is controlled so as to heat the substrate to a melting point or higher of the solder powder, the radical supplying unit is controlled so that the substrate is exposed to a radical atmosphere, and the temperature of the substrate is set to solder. A control unit that controls the temperature adjusting unit to lower the temperature below the melting point of the powder.

  According to the component mounting method disclosed in the present specification described above, components can be mounted on a substrate while suppressing oxidation of electrodes and the like.

  Moreover, according to the component mounting apparatus disclosed in the present specification described above, components can be mounted on a substrate while suppressing oxidation of electrodes and the like.

  The objects and advantages of the invention will be realized and obtained by means of the elements and combinations particularly pointed out in the appended claims.

  Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention as claimed.

It is a figure which shows one Embodiment of the component mounting apparatus disclosed to this specification. It is a figure which shows the board | substrate with which the electronic component has been arrange | positioned through solder paste. It is a figure which shows the flowchart of one Embodiment of the component mounting method disclosed in this specification. It is a figure which shows the temperature profile of the reflow temperature used with the component mounting method disclosed in this specification. It is a figure explaining the reduction reaction of formic acid. It is a figure explaining the decomposition reaction by the radical of a reducing agent, an organic material, and the metal salt of a reducing agent. It is a figure explaining the solder joint part of Example 1. FIG. It is a figure explaining the solder joint part of the comparative example 1. FIG. It is a figure explaining the solder joint part of the comparative example 2. FIG.

  Hereinafter, a preferred embodiment of a component mounting apparatus disclosed in this specification will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

  FIG. 1 is a diagram illustrating an embodiment of a component mounting apparatus disclosed in this specification. FIG. 2 is a diagram showing a substrate on which electronic components are arranged via solder paste.

  In the component mounting apparatus 10 (hereinafter also simply referred to as the apparatus 10) of the present embodiment, the substrate 20 on which the electronic components 22 and 23 are arranged via the solder paste 24 is transported inside, and the electronic components 22 and 23 are mounted on the substrate. 20 is an apparatus for reflow soldering.

  The apparatus 10 includes a heating chamber 10a, a melting chamber 10b, and a cooling chamber 10c along the direction in which the substrate 20 is conveyed. The heating chamber 10a having the substrate carry-in port, the melting chamber 10b, and the cooling chamber 10c having the substrate carry-out port form a substrate carrying path through which the substrate 20 is carried. The substrate 20 placed on the substrate transport plate 18 is transported through a substrate transport path in the apparatus 10 by a transport unit (not shown).

  A shutter 17a is attached between the heating chamber 10a and the melting chamber 10b, and a shutter 17b is attached between the melting chamber 10b and the cooling chamber 10c, so that the melting chamber 10b can be hermetically sealed. Further, shutters 17c and 17d are disposed at the substrate carry-in port of the heating chamber 10a and the substrate carry-out port of the cooling chamber 10c, respectively. The apparatus 10 includes a control unit 15 that controls operations of the shutters 17a to 17d.

  The apparatus 10 also supplies an inert gas supply unit 12 that supplies an inert gas into the substrate transfer path, a reducing agent supply unit 13 that supplies a reducing agent into the substrate transfer path, and supplies radicals into the substrate transfer path. And a radical supply unit 14. Operations of the inert gas supply unit 12, the reducing agent supply unit 13, and the radical supply unit 14 are controlled by the control unit 15.

  The heating chamber 10a includes a first temperature adjusting unit 11a surrounding the substrate transfer path. The first temperature adjusting unit 11a adjusts the temperature in the heating chamber 10a. The operation of the first temperature adjustment unit 11a is controlled by the control unit 15. Moreover, the heating chamber 10a has an inert gas supply pipe 12a for supplying nitrogen gas therein. The inert gas is supplied from the inert gas supply unit 12 to the inert gas supply pipe 12a. For example, nitrogen can be used as the inert gas. Moreover, the heating chamber 10a may have an exhaust pipe for exhausting the internal gas.

  The melting chamber 10b has a second temperature adjusting unit 11b surrounding the substrate transfer path. The second temperature adjusting unit 11b adjusts the temperature in the melting chamber 10b. The operation of the second temperature adjustment unit 11b is controlled by the control unit 15.

  The melting chamber 10b has an inert gas supply pipe 12b for supplying nitrogen gas therein, a reducing agent supply pipe 13a for supplying a reducing agent, and a radical supply pipe 14a for supplying radicals. The inert gas is supplied from the inert gas supply unit 12 to the inert gas supply pipe 12b. A gas phase reducing agent is supplied from the reducing agent supply unit 13 to the reducing agent supply pipe 13a. Radicals are supplied from the radical supply unit 14 to the radical supply pipe 14a. The reducing agent supply pipe 13a is located downstream of the substrate transport path with respect to the inert gas supply pipe 12b. The radical supply pipe 14a is located downstream of the substrate transport path with respect to the reducing agent supply pipe 13a.

  The reducing agent supply unit 13 supplies a gas phase reducing agent into the melting chamber 10b through the reducing agent supply pipe 13a. The gas phase reducing agent introduced into the melting chamber 10b diffuses into the melting chamber 10b, and the substrate 20 is exposed to a reducing atmosphere.

  Examples of the reducing agent include carboxylic acids such as formic acid, acetic acid, and propionic acid, carboxylic acid esters such as methyl formate and ethyl formate, carboxylates such as ammonium formate, hydrogen, and the like.

  The radical supply unit 14 supplies radicals into the melting chamber 10b through the radical supply pipe 14a. The radicals introduced into the melting chamber 10b diffuse into the melting chamber 10b, and the substrate 20 is exposed to the radical atmosphere.

The radical that forms the radical atmosphere preferably has atoms other than oxygen from the viewpoint of preventing oxidation of solder or electrodes. Specifically, the radical supply unit 14 can generate a radical that forms a radical atmosphere using at least one gas of H ₂ O, CO, CO ₂ , N ₂ , NO, and NO _2. .

  In addition, the radical supply unit 14 may recover the reducing agent that has formed the reducing atmosphere from the melting chamber 10b using, for example, the first exhaust pipe 16a, and generate radicals using the recovered reducing agent.

  The radical supply unit 14 may generate a radical by, for example, heating a raw material gas using a heating means such as a filament. As another means for generating radicals, for example, there is a radical generation method in which a high-frequency power source such as a parallel plate, an ion beam, or ECR is applied. However, this method requires a sealed chamber having a complicated structure. On the other hand, in the case where radicals are generated by heating the raw material gas using a heating means such as a filament, such a sealed chamber is not required and can be attached to a conveyor reflow furnace having a simple structure.

  The melting chamber 10b has a first exhaust pipe 16a and a second exhaust pipe 16b for exhausting the internal gas. The first exhaust pipe 16a is located between the reducing agent supply pipe 13a and the radical supply pipe 14a. The second exhaust pipe 16b is located downstream of the first transport pipe 16a in the substrate transport path. Each of the first exhaust pipe 16a and the second exhaust pipe 16b can be independently adjusted in exhaust amount, and is connected to an exhaust unit (not shown). The operation of the exhaust unit is controlled by the control unit 15.

  The cooling chamber 10c has a third temperature adjusting unit 11c surrounding the substrate transfer path. The third temperature adjusting unit 11c adjusts the temperature in the cooling chamber 10c. The operation of the third temperature adjusting unit 11c is controlled by the control unit 15. The cooling chamber 10c has a radical supply pipe 14b for supplying radicals therein. Radicals are supplied from the radical supply unit 14 to the radical supply pipe 14b.

  The cooling chamber 10c has a third exhaust pipe 16c for exhausting the internal gas. The third exhaust pipe 16c is located downstream of the substrate transport path with respect to the radical supply pipe 14b. The third exhaust pipe 16c is connected to an exhaust unit (not shown). The operation of the exhaust unit is controlled by the control unit 15.

  In the above description, the device 10 includes the heating chamber 10a, the melting chamber 10b, and the cooling chamber 10c separately. However, the device 10 may include a single chamber having these functions.

  Next, the board | substrate 20 conveyed by the board | substrate conveyance path in the apparatus 10 is demonstrated below with reference to FIG.

  On the substrate 20, electronic components 22 and 23 are arranged via a solder paste 24. Electrodes 21 a and 21 b are formed on the substrate 20. As for the electronic component 22, the terminal 22a is adhere | attached on the electrode 21a using the solder paste 24. FIG. The terminal 23 a of the electronic component 23 is bonded onto the electrode 21 b using the solder paste 24.

  As the solder paste 24, a known one can be used, but in the present embodiment, the solder paste described below is used.

In the solder paste 24, two or more kinds of polybutenes (polybutene: chemical formula (C ₄ -H ₈ ) _n ) having different molecular weights as a binder resin are added to the solder fine powder at an arbitrary ratio, kneaded and defoamed. It was produced by kneading fine solder powder and polybutene. The fine solder powder is, for example, tin-zinc (SnZn) having a particle size of about 10 to 38 μm and containing 9% by mass of zinc, and its melting point is 199 ° C.

Polybutene is a low polymer mainly composed of isobutylene and is a liquid polymer obtained by copolymerization of butene-1, for example, a first polybutene ((C ₄ -H ₈ ) _n1 ) having an average molecular weight of 300 or less. A material in which second polybutene ((C ₄ -H ₈ ) _n2 ) having an average molecular weight of about 500 was mixed at a ratio of about 5 to 1 was used. The viscosity after adding polybutene to the fine powder of solder, kneading and defoaming was set to 100 Pa · s to 250 Pa · s, for example. In this case, the fine solder powder and the polybutene are mixed at a ratio of about 90% by mass and about 10% by mass, or are mixed at a ratio of about 50% by volume.

  In the solder paste manufacturing process described above, the decomposition temperature has been widened by forming polybuden mixed with the solder fine powder melted at the first temperature with two or more organic materials having different average molecular weights. However, the organic material is a material that is liquid at room temperature, starts to volatilize and decompose at a second temperature lower than the first temperature, and finishes decomposition by holding the third temperature higher than the first temperature for a predetermined time. It ’s fine. The organic material does not need to be a plurality of types, and is not limited to polybutene, and may contain at least one of hydrocarbon, alcohol, and silicone.

  Next, a preferred embodiment of the component mounting method disclosed in this specification will be described below with reference to the drawings. The component mounting method of this embodiment uses the component mounting apparatus described above.

  FIG. 3 is a diagram illustrating a flowchart of an embodiment of the component mounting method disclosed in this specification. FIG. 4 is a diagram showing a temperature profile of the reflow temperature used in the component mounting method disclosed in this specification.

  First, in step S10, the shutter 17c is opened, and the substrate transport plate 18 on which the substrate 20 on which the electronic components 22 and 23 are placed is filled with an inert gas from the substrate carry-in port of the heating chamber 10a. It is carried into the heating chamber 10a. It is carried into the heating chamber 10a. The temperature of the substrate 20 carried into the heating chamber 10a is room temperature.

  As the substrate 20 is transported in the heating chamber 10a by the substrate transport plate 18, the first temperature adjusting unit rises from room temperature to a temperature T1 lower than the melting point of the solder, for example, 160 ° C., as shown in FIG. It is heated by 11a (heating process).

  Next, in step S12, on the heated substrate 20, the polybudene having an average molecular weight of about 300 in the solder paste 24 starts to decompose and volatilize when the temperature reaches T1, for example, 160 ° C. (start of the volatile decomposition process). ).

  Then, the shutter 17a is opened by the control unit 15, and the substrate transport plate 18 on which the substrate 20 is placed is carried into the melting chamber 10b. The substrate 20 carried into the melting chamber 10b is heated by the second temperature adjusting unit 11b.

  Next, in step S14, the substrate 20 carried into the melting chamber 10b is first exposed to the inert gas introduced from the inert gas supply pipe 12b. Thereafter, the substrate 20 is exposed to a reducing atmosphere by a gas phase reducing agent introduced from the reducing agent supply pipe 13a (reducing step).

  In this embodiment, formic acid gas is used as the reducing agent. Thereby, the formic acid gas starts to reduce the solder paste 24 on the substrate 20 heated to the temperature T1 and the oxide films on the surfaces of the electrodes 21a and 21b. The concentration of formic acid gas in the melting chamber 10b can be, for example, several tens of ppm to several thousand ppm.

  FIG. 5 is a diagram for explaining the reduction reaction of formic acid.

  As shown in FIG. 5, formic acid (HCOOH) reduces the oxide film (CuO) on the surface of the electrode formed of the Cu material, exposes the Cu material forming the electrode, and has good solder wettability. To express.

  Further, in the melting chamber 10b, the polybudene having an average molecular weight of 300 continues to decompose and volatilize while the temperature of the substrate 20 reaches the temperature T2 from the temperature T1, for example, 221 ° C. Then, the formic acid gas introduced from the reducing agent supply pipe 13a penetrates into the gaps between the solder fine powders caused by the volatilization of the polybuden, and reduces the oxide film on the surface of the solder fine powders. To express sex.

  Subsequently, when the temperature of the substrate 20 is heated to a temperature T2, for example, 221 ° C., the polybudene having an average molecular weight of about 300 is further volatilized and almost disappears. Thus, the exposure amount of the solder fine powder increases as the volatilization amount of the polybudene having an average molecular weight of 300 increases.

  When the temperature of the substrate 20 reaches the melting point of the solder, the solder fine powder melts and starts to be connected to each other.

  In the reduction process of the present embodiment, in order to sufficiently melt the solder fine powder, the substrate 20 is subjected to the second temperature adjustment until the temperature of the substrate 20 reaches a temperature T3 higher than the melting point of the solder, for example, 250 ° C. It is heated by the part 11b.

  Further, while the temperature of the substrate 20 rises from the temperature T2 to the temperature T3, for example, 250 ° C., the polybuden having an average molecular weight of about 500 starts to decompose and volatilize. As the powder is further reduced, the amount linked by melting increases. Then, the temperature of the substrate 20 reaches the temperature T3, and polybuden having an average molecular weight of about 500 is decomposed and volatilized in a predetermined time thereafter, and almost disappears (end of the volatile decomposition step).

  In this way, polybutene, which is an organic material, is gradually volatilized or decomposed until reaching a temperature T3 equal to or higher than the melting point of the solder fine powder. As a result, the solder fine powder is gradually exposed and gradually reduced and integrated, so that rapid integration of the solder fine powder is avoided, thereby preventing the so-called Manhattan phenomenon.

  That is, when polybutene volatilizes rapidly during the heating in the melting chamber 10b, the timing at which the solder spreads between the two terminals of the electronic component may be slightly different. For example, when the solder wetting spreads faster at both ends of the chip capacitor than at the other, the surface tension of the solder of the previously wetted terminal may cause a Manhattan phenomenon and the electronic component may stand upright.

  Therefore, in this embodiment, in order to suppress this time difference in surface tension, polybutene having a large molecular weight, a high volatilization temperature, and a long decomposition time is used. Of course, it is possible to cover any temperature and time profile with a single molecular weight polybutene.

  In addition, as shown in FIG. 4, in this embodiment, the volatile decomposition process is started before the reduction process, so that the formic acid gas penetrates into the gaps between the fine powders of solder generated by the volatilization or decomposition of polybuden. It is easy. Further, by performing the volatile decomposition process until after the reduction process is completed, the solder fine powder and the oxide film on the surface of the electrode are sufficiently reduced.

  By the way, formic acid is gasified at 110 ° C. or higher, and when gasified, it exhibits reducing properties even at a low temperature of about 150 ° C. Therefore, even if the substrate 20 is formed of an organic material, the substrate 20 is not burned or decomposed by the reducing atmosphere. Thereby, it is possible to use formic acid as a reducing gas at a temperature of 300 ° C. or lower.

  The control unit 15 controls the flow rate of formic acid gas introduced from the reducing agent supply pipe 13a and the exhaust amount exhausted from the first exhaust pipe 16a, so that the formic acid gas in the melting chamber 10b is more than in the first exhaust pipe 16a. Do not diffuse downstream. For this control, the device 10 may have a larger number of exhaust pipes as required. Moreover, it is preferable to design the length of the substrate transport path in the melting chamber 10b so that the formic acid gas in the melting chamber 10b does not diffuse downstream from the first exhaust pipe 16a.

  Next, in step S16, the temperature of the substrate 20 is heated to a temperature T3 equal to or higher than the melting point of the fine solder powder, for example, 250 ° C., and the fine solder powder is sufficiently melted (melting step). The electrodes 21a and 21b whose surfaces are sufficiently reduced by the formic acid gas are electrically connected to the terminals 22a and 23a of the electronic components 22 and 23 by molten solder. In this melting step, the state where the temperature of the substrate 20 is at the temperature T3 is maintained for a predetermined time, and the electrodes 21a and 21b and the terminals 22a and 23a are sufficiently connected by the molten solder.

  Next, in step S18, the substrate 20 is exposed to a radical atmosphere by radicals introduced from the radical supply pipe 14a (radical process). In this radical process, the temperature of the substrate 20 is maintained at a temperature T3, for example, 250 ° C., equal to or higher than the melting point of the solder fine powder. In the present embodiment, OH radicals are generated using water vapor as a source gas.

  In the radical process, formic acid, which is a reducing agent attached to the substrate 20 or the electronic components 22 and 23, is decomposed and removed by radicals. The formic acid used in the reduction process adheres to the surface of the substrate 20 or the electronic components 22, 23, or between the electronic components 22, 23 and the substrate 20, or to the gaps such as the terminals 22a, 23a of the electronic components 22, 23. May have. Since these adhering formic acids may corrode the electrodes and the like, they are removed in the radical process.

  Further, in the reduction process, Sn in the solder and formic acid as a reducing agent may react to produce a metal salt of formic acid. When the substrate to which the metal salt is attached is used in a high-temperature and high-humidity state, the metal salt and Sn in the solder are ionized to generate a potential difference between them, and the Sn ion moves to the metal salt of formic acid. There is a risk of ion migration in which metal precipitates. Therefore, in the radical process, the metal salt of formic acid is removed.

  Furthermore, an organic material such as polybutene in the solder paste may remain on the substrate 20 after the melting step. Therefore, in the radical process, this organic material is removed.

  The radicals introduced from the radical supply pipe 14 a diffuse into the melting chamber 10 b and form a radical atmosphere around the substrate 20. The radicals sufficiently permeate the surface of the substrate 20 or the electronic components 22, 23, the space between the electronic components 22, 23 and the substrate 20, or the gaps such as the terminals 22 a, 23 a of the electronic components 22, 23.

  Here, as another method of exposing the substrate to radicals, for example, there is a method of generating radicals locally using ultraviolet rays and irradiating the substrate. However, with such a method of locally irradiating radicals, the radicals cannot be sufficiently penetrated into a gap between the electronic component and the substrate.

  FIG. 6 is a diagram illustrating a decomposition reaction by radicals of a reducing agent, an organic material, and a metal salt of the reducing agent.

  FIG. 6A illustrates a reaction in which carboxylic acid as a reducing agent is decomposed by OH radicals. Here, R represents an alkyl group. Similarly, formic acid is also decomposed by OH radicals.

FIG. 6B illustrates a reaction in which C ₄ H ₈ that is an organic material is decomposed by OH radicals.

FIG. 6C illustrates a reaction in which (HCOO) ₂ M, which is a metal salt of formic acid, is decomposed by OH radicals. Here, M represents a metal atom.

  In the radical step, the radical forming the radical atmosphere preferably has an atom other than oxygen from the viewpoint of preventing oxidation of the electrode or the terminal. From this viewpoint, it is particularly preferable that the radical forming the radical atmosphere does not contain oxygen.

  Further, exposing the substrate 20 to a radical atmosphere at a temperature equal to or higher than the boiling point of the reducing agent forming the reducing atmosphere promotes the decomposition reaction of the reducing agent by radicals, and decomposes and removes the reducing agent by radicals. preferable.

The radical concentration in the melting chamber 10b can be, for example, 10E6 to 10E10 cm ⁻³ . The radical concentration is adjusted by the control unit 15 controlling the radical supply amount from the radical supply pipe 14a and the exhaust amount exhausted from the first exhaust pipe 16a and the second exhaust pipe 16b.

  The pressure in the melting chamber in the radical process can be set to, for example, 200 to 101325 Pa (1.5 to 760 Torr). This pressure is adjusted by the control unit 15 controlling the radical supply amount from the radical supply pipe 14a and the exhaust amount exhausted from the first exhaust pipe 16a and the second exhaust pipe 16b.

  Moreover, as temperature in the melting chamber in a radical process, it can be set as 140-260 degreeC, for example. This temperature is adjusted by the control unit 15 controlling the second temperature adjustment unit 11b.

  The control unit 15 controls the flow rate of radicals introduced from the radical supply pipe 14a and the exhaust amount exhausted from the first exhaust pipe 16a and the second exhaust pipe 16b, so that the radicals in the melting chamber 10b are transferred to the first exhaust pipe. It is prevented from diffusing upstream from 16a. For this control, the device 10 may have a larger number of exhaust pipes as required. Further, it is preferable to design the length of the substrate transfer path in the melting chamber 10b so that radicals in the melting chamber 10b do not diffuse upstream from the first exhaust pipe 16a.

  In the apparatus 10, the radical process is continuously performed also in the next cooling chamber 10c.

  Next, in step S20, the shutter 17b is opened by the control unit 15, and the substrate transport plate 18 on which the substrate 20 is placed is carried into the cooling chamber 10c (cooling step). In the cooling step, the substrate 20 carried into the cooling chamber 10c is cooled by the third temperature adjusting unit 11c so that the temperature of the substrate is lower than the melting point of the fine solder powder.

  In the cooling chamber 10c, the temperature of the substrate 20 is lowered below the melting point of the solder fine powder, so that the solder that is melted and integrated into a substantially ball shape by the surface tension is lowered to a solid. Specifically, as shown in FIG. 4, the substrate 20 carried into the cooling chamber 10c is cooled from the temperature T3 by the third temperature adjusting unit 11c, rapidly cooled after passing through the freezing point, and gradually cooled to the temperature. Is reduced. By such a reflow process, the electronic components 22 and 23 and the electrodes 21a and 21b are soldered.

  Also in the cooling chamber 10c, the substrate 20 is cooled and exposed to a radical atmosphere by radicals introduced from the radical supply pipe 14b. In the cooling chamber 10c, the reducing agent, organic material, or metal salt of the reducing agent that has not been removed in the melting chamber 10b is decomposed and removed by radicals. As shown in FIG. 4, since the radical process is performed also in the cooling chamber 10c, a part of the radical process is performed overlapping the cooling process.

The radical concentration in the cooling chamber 10c can be, for example, 10E6 to 10E10 cm ⁻³ . The radical concentration is adjusted by the control unit 15 controlling the radical supply amount from the radical supply pipe 14b and the exhaust amount exhausted from the third exhaust pipe 16c.

  Moreover, as a pressure of the cooling chamber 10c in a radical process, it can be set as 200-101325Pa (1.5-760Torr), for example. This pressure is adjusted by the control unit 15 controlling the radical supply amount from the radical supply pipe 14b and the exhaust amount exhausted from the third exhaust pipe 16c.

  Moreover, as temperature in the cooling chamber 10c in a radical process, it can be 20-100 degreeC, for example. This temperature is adjusted by the control unit 15 controlling the third temperature adjustment unit 11c.

  The control unit 15 controls the flow rate of radicals introduced from the radical supply pipe 14b and the exhaust amount exhausted from the third exhaust pipe 16c, so that the radicals in the cooling chamber 10c diffuse downstream from the third exhaust pipe 16c. I try not to. For this control, the device 10 may have a larger number of exhaust pipes as required. In addition, it is preferable to design the length of the substrate transfer path in the cooling chamber 10c so that radicals in the cooling chamber 10c do not diffuse downstream from the third exhaust pipe 16c. Further, an inert gas may be supplied to the cooling chamber 10c.

  In step S22, the shutter 17d is opened by the control unit 15, and the substrate transport plate 18 on which the substrate 20 is placed is unloaded from the apparatus 10 through the substrate unloading port of the cooling chamber 10c.

  According to the component mounting method using the component mounting apparatus of the present embodiment described above, since the reducing agent is decomposed and removed by radicals, it is possible to mount the electronic component on the substrate while suppressing oxidation of solder and electrodes. Moreover, in the component mounting method of this embodiment, the organic material and the metal salt of the reducing agent can be decomposed and removed by radicals. Therefore, the board manufactured using the component mounting method of this embodiment has high reliability and yield.

  In the present invention, the component mounting method and component mounting apparatus of the above-described embodiment can be modified as appropriate without departing from the spirit of the present invention. In addition, the configuration requirements of one embodiment can be applied to other embodiments as appropriate.

For example, in the radical process, a radical atmosphere may be formed using a plurality of radicals. For example, in the radical process, radicals that form a radical atmosphere may be generated using a plurality of gases of H ₂ O, CO, CO ₂ , N ₂ , NO, and NO ₂ .

  Further, in the embodiment of the component mounting method described above, the volatile decomposition step is performed overlapping the reduction step and the melting step, but the volatile decomposition step may be arranged only between the heating step and the reduction step. good.

  Hereinafter, a component mounting method using the component mounting apparatus disclosed in this specification will be further described with reference to examples. However, the scope of the present invention is not limited to such examples.

[Example 1]
The electronic component and the electrode on the substrate were soldered using the component mounting method of the present embodiment described above. Then, EPMA analysis was performed on the cross section of the solder joint portion of the electrode soldered according to Example 1. The results of EPMA analysis are shown in FIG. FIG. 7 shows an electrode 30, which is a Cu material, solder 32, and a Zn distribution region 31 derived from the solder. In the region 31, a thin layer having a certain thickness is formed between the electrode 30 and the solder 32. Since the region 31 is a bonding layer formed of an alloy of Cu forming the electrode 30 and Zn derived from solder, the soldering according to the first embodiment can provide good solder wettability in the electrode. confirmed. Further, on the substrate soldered according to Example 1, oxidation of solder and electrodes and organic material residues were not observed.

[Example 2]
Soldering of Example 2 was performed in the same manner as Example 1 except that radicals using CO gas as a raw material instead of OH radicals were used. Also in the soldering of Example 2, the same result as in FIG. 7 was obtained, so it was confirmed that the soldering according to Example 2 provides good solder wettability in the electrode. Moreover, the oxidation of the solder and the electrodes and the residue of the organic material were not observed on the substrate soldered according to Example 2.

[Example 3]
Soldering of Example 3 was performed in the same manner as Example 1 except that radicals using CO ₂ gas as a raw material instead of OH radicals were used. Also in the soldering of Example 3, the same result as in FIG. 7 was obtained, so it was confirmed that the soldering according to Example 3 provides good solder wettability in the electrode. Moreover, the oxidation of the solder and the electrodes and the residue of the organic material were not observed on the substrate soldered according to Example 3.

[Example 4]
Soldering of Example 4 was performed in the same manner as Example 1 except that radicals using NO gas as a raw material instead of OH radicals were used. Also in the soldering of Example 4, the same results as in FIG. 7 were obtained. Therefore, it was confirmed that the soldering according to Example 4 provides good solder wettability in the electrodes. Moreover, the oxidation of the solder and the electrodes and the residue of the organic material were not observed on the substrate soldered according to Example 4.

[Example 5]
Soldering of Example 5 was performed in the same manner as Example 1 except that radicals using NO ₂ gas as a raw material instead of OH radicals were used. Also in the soldering of Example 5, the same results as in FIG. 7 were obtained. Therefore, it was confirmed that the soldering according to Example 5 provides good solder wettability in the electrodes. Further, no solder and electrode oxidation and organic material residues were observed on the substrate soldered according to Example 5.

[Comparative Example 1]
Comparative Example 1 was soldered in the same manner as Example 1 except that the radical process was not performed. Then, EPMA analysis was performed on the cross section of the solder joint portion of the electrode soldered in Comparative Example 1. The results of EPMA analysis are shown in FIG. In the region 31, a layer having a non-uniform thickness is formed between the electrode 30 and the solder 32, and it was confirmed that the solder wettability is poor in the soldering according to the comparative example 1. Further, in the joint portion soldered by Comparative Example 1, a resistance value 10 times or more that of Example 1 was measured.

[Comparative Example 2]
Comparative Example 2 was soldered in the same manner as Example 1 except that the reduction step was not performed. Then, EPMA analysis was performed on the cross section of the solder joint portion of the electrode soldered in Comparative Example 2. The results of EPMA analysis are shown in FIG. In the region 31, a wide layer was formed between the electrode 30 and the solder 32, and it was confirmed that the solder wettability was worse than that in Comparative Example 1 in the soldering according to Comparative Example 2. Further, at the joint portion soldered in Comparative Example 2, a resistance value more than 50 times that in Example 1 was measured.

  All examples and conditional words mentioned herein are intended for educational purposes to help the reader deepen and understand the inventions and concepts contributed by the inventor. All examples and conditional words mentioned herein are to be construed without limitation to such specifically stated examples and conditions. Also, such exemplary mechanisms in the specification are not related to showing the superiority and inferiority of the present invention. While embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions or modifications can be made without departing from the spirit and scope of the invention.

  Regarding the above-described embodiments, the following additional notes are disclosed.

(Appendix 1)
A first step in which a component is exposed to a reducing atmosphere through a solder paste including a solder paste containing solder powder;
A second step of heating the substrate above the melting point of the solder powder;
A third step of exposing the substrate to a radical atmosphere;
A fourth step of lowering the temperature of the substrate below the melting point of the solder powder;
A component mounting method comprising:

(Appendix 2)
The component mounting method according to appendix 1, wherein the radical that forms the radical atmosphere has an atom other than oxygen.

(Appendix 3)
The component mounting method according to appendix 2, wherein the radical that forms the radical atmosphere is generated using at least one gas of H ₂ O, CO, CO ₂ , N ₂ , NO, and NO 2.

(Appendix 4)
The component mounting method according to any one of appendices 1 to 3, wherein a radical that forms the radical atmosphere is generated using a reducing agent that forms the reducing atmosphere.

(Appendix 5)
The component mounting method according to any one of appendices 1 to 4, wherein, in the third step, the substrate is exposed to the radical atmosphere at a temperature equal to or higher than a boiling point of a reducing agent that forms the reducing atmosphere.

(Appendix 6)
The component mounting method according to any one of appendices 1 to 5, wherein a radical that forms the radical atmosphere is generated by heating a raw material gas.

(Appendix 7)
The solder paste has solder powder and organic material,
Before the first step,
The component mounting method according to any one of appendices 1 to 6, further comprising a fifth step of heating the substrate to volatilize or decompose the organic material in the solder paste.

(Appendix 8)
Solder paste
Solder powder that melts at a first temperature;
The organic material that is liquid at room temperature, starts to volatilize and decompose at a second temperature lower than the first temperature, and finishes decomposition by maintaining a third temperature higher than the first temperature for a predetermined time. The component mounting method according to any one of appendices 1 to 7.

(Appendix 9)
The component mounting method according to appendix 8, wherein the organic material includes a plurality of materials having different decomposition temperatures.

(Appendix 10)
A chamber in which a substrate on which a component is placed via a solder paste containing solder powder is placed;
A temperature adjusting unit for adjusting the temperature in the chamber;
A reducing agent supply unit for supplying a reducing agent into the chamber;
A radical supply unit for supplying radicals into the chamber;
The reducing agent supply unit is controlled to expose the substrate to a reducing atmosphere, the temperature adjusting unit is controlled to heat the substrate to a melting point or higher of the solder powder, and the substrate is exposed to a radical atmosphere. A control unit for controlling the radical supply unit and controlling the temperature adjustment unit to lower the temperature of the substrate below the melting point of the solder powder;
A component mounting device equipped with

10 Component mounting apparatus 10a Heating chamber (heating chamber)
10b Melting chamber (melting chamber)
10c Cooling chamber (cooling chamber)
11a 1st temperature control part 11b 2nd temperature control part 11c 3rd temperature control part 12 Inert gas supply part 12a, 12b Inert gas supply pipe 13 Reductant supply part 13a Reductant supply pipe 14 Radical supply part 14a, 14b Radical Supply pipe 15 Control section 16a First exhaust pipe 16b Second exhaust pipe 17a, 17b, 17c, 17d Shutter 18 Substrate transport plate 20 Substrate 21a, 21b Electrode 22 Electronic component 22a Terminal 23 Electronic component 23a Terminal 24 Solder paste 30 Electrode 31 Zn Distribution area of 32 solder

Claims (7)

A first step of reducing a surface of the electrode and an oxide film on the surface of the solder powder by exposing a substrate on which a component having an electrode is disposed via a solder paste containing a solder powder to a reducing atmosphere containing a reducing agent ; ,
A second step of heating the substrate above the melting point of the solder powder;
A third step of exposing the substrate to a radical atmosphere to decompose the reducing agent adhering to the component or the substrate ;
A fourth step of lowering the temperature of the substrate below the melting point of the solder powder;
A component mounting method comprising: The solder paste includes the solder powder and an organic material,
The component mounting method according to claim 1, wherein in the third step, the substrate is exposed to a radical atmosphere to decompose the reducing agent and the organic material adhering to the component or the substrate . Radicals which form the radical atmosphere, component mounting method according to claim 1 or 2 having an atom other than oxygen. The component mounting method according to claim 3 , wherein the radical that forms the radical atmosphere is generated using at least one gas of H ₂ O, CO, CO ₂ , N ₂ , NO, and NO ₂ . The component mounting method according to any one of claims 1 to 4 , wherein a radical that forms the radical atmosphere is generated using a reducing agent that forms the reducing atmosphere. Wherein in the third step, at a temperature higher than the boiling point of the reducing agent to form the reducing atmosphere, the component mounting method according to any one of claim 1 to 5, exposing the substrate to the radical atmosphere. A chamber in which a substrate on which a component having electrodes is arranged via a solder paste containing solder powder is placed;
A temperature adjusting unit for adjusting the temperature in the chamber;
A reducing agent supply unit for supplying a reducing agent into the chamber;
A radical supply unit for supplying radicals into the chamber;
Exposing the substrate to a reducing atmosphere, controlling the reducing agent supply unit so as to reduce the oxide film on the surface of the electrode and the surface of the solder powder , and heating the substrate to a temperature equal to or higher than the melting point of the solder powder. Controlling the temperature adjusting unit, exposing the substrate to a radical atmosphere, controlling the radical supply unit to decompose the reducing agent attached to the component or the substrate , and the substrate A control unit for controlling the temperature adjusting unit so as to lower the temperature of the solder powder below the melting point of the solder powder;
A component mounting device equipped with

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