JP4818181B2 - Solder paste, component mounting method and component mounting apparatus - Google Patents

Description

  The present invention relates to a solder paste, a component mounting method, and a component mounting apparatus, and in particular, a solder paste used for mounting components such as chip components, LSI packages, and LSIs by solder (solder) bonding, and the solder paste. The present invention relates to a component mounting method to be used and a component mounting apparatus for performing the component mounting method.

  In the surface mounting method, which is a general component mounting method, a surface mount component (SMD: Surface Mount Device) such as a chip component or LSI package is mounted. First, paste solder containing flux components is padded or connected. A printed circuit board coated on a conductive portion called a terminal is prepared, and chip components and the like are mounted using a dedicated device called a chip mounter. Thereafter, according to the melting point of the solder, for example, the solder is melted by heating to about 250 ° C. in a high-temperature furnace, and the chip component or the like is solder-connected on the printed board. The substrate on which the components are soldered is cleaned with an organic solvent to remove flux residues such as organic acids and organic acid salts.

  By using such a surface mounting technology method, the through hole of the substrate that was necessary in the pin insertion method is no longer necessary, and it is possible to reduce the size of components, increase the mounting density, and reduce the size of the substrate. In addition, the degree of freedom of wiring has increased in the multilayer substrate.

  However, when the component becomes smaller and the gap between the connecting portions by solder becomes narrower, it becomes difficult to remove the gap between the component and the substrate and the flux residue adhering between the components by cleaning.

  If flux residue remains between the metal terminals of the component, there is a risk that metal will precipitate from the organic acid salt of the metal contained in the flux residue due to conditions such as moisture, temperature, bias, etc., causing a short circuit between the terminals. is there. Further, the organic acid contained in the flux residue elutes the metal of the solder connection portion and the metal of the substrate, and there is a risk that the terminals are electrically short-circuited.

  If the solder paste does not generate a flux residue after reflow, the problem of short circuit can be solved. However, if the solder paste does not contain a flux component, the oxide film on the solder surface and the oxide film on the copper surface of the substrate cannot be removed, and the components cannot be soldered.

  Reducing, for example, using hydrogen gas instead of flux, reducing the surface oxide film of solder or copper, and melting the solder, can be connected by solder without flux. However, since reduction with hydrogen requires a high temperature of 300 ° C. or higher, an organic material having poor heat resistance such as a printed circuit board cannot be used because the organic material burns or decomposes.

  On the other hand, a method for removing the surface oxide film of solder at a temperature lower than 300 ° C. using formic acid as a reducing gas is disclosed in the following Patent Documents 1 to 3 and the like.

JP 2001-244618 A JP 2002-270609 A Special table 2003-533880 gazette

  Incidentally, the Manhattan phenomenon is a problem that occurs when a small component is surface-mounted by solder. The Manhattan phenomenon is a phenomenon in which when two terminals are soldered to a substrate, such as a resistance element and a capacitor element, the other terminal is lifted from the substrate by the surface tension of the molten solder on one terminal side. This is caused by unevenness in the amount of each solder.

  An object of the present invention is to provide a solder paste, a component mounting method, and a component mounting apparatus capable of improving the reliability when soldering a portion having a small interval.

  According to an aspect of the present invention, the solder paste is a fine powder of solder that melts at a first temperature and a liquid at room temperature, and begins to volatilize and decompose at a second temperature lower than the first temperature. It is characterized by being mixed with an organic material that can be decomposed by maintaining a high third temperature for a first time. In this case, the organic material may be composed of a plurality of materials having different decomposition temperatures.

  By using the present invention, when solder paste is used to mount a component on a substrate, the organic material is gradually removed from the solder paste so that the solder fine powder in the solder paste is not rapidly integrated. In addition, the so-called Manhattan phenomenon can be prevented and flux cleaning can be completely removed from the surface mounting technology. In particular, by applying to small parts and parts having a small electrode pitch, it is possible to improve connection reliability, which has been difficult in the past.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view showing an example of a solder paste production method.

In FIG. 1, in the container 1, two or more kinds of polybutenes (polybuten: chemical formula (C ₄ -H ₈ ) _n ) 4 having different molecular weights are added to the solder fine powder 3 in an arbitrary ratio, kneaded, defoamed, Thus, a solder paste 2 in which the solder fine powder 3 and the polybutene 4 are kneaded is prepared.

  The solder fine powder 3 is, for example, silver tin (SnAg) formed with a particle size of about 10 to 38 μm and containing 2.5% by mass of silver, and its melting point (first temperature) is 221 ° C. .

The polybutene 4 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. And a second polybutene ((C ₄ -H ₈ ) _n2 ) having an average molecular weight of about 500 and a ratio of about 5 to 1 is used.

The polybutene 4 formed by mixing the two types starts to decompose at a second temperature T ₂ (T ₂ <T ₁ ) lower than the first temperature T _1, which is the melting point of the solder, and higher than the room temperature T ₀ , Further, while the temperature is raised from the second temperature T ₂ to the third temperature T ₃ (T ₃ > T ₁ ) higher than the first temperature T ₁ , decomposition and volatilization occur and at the same time the third temperature T ₃ is reached. , or a third temperature T ₃ and so terminate the volatilization after holding for a predetermined time, the total volatile content of the organic material between as shown in FIG. 2, rising from at least a second temperature T ₂ to the third temperature T ₃ Is increased, that is, the organic material continues to volatilize.

  The polybutene 4 is added to the solder fine powder 3, kneaded and defoamed, and its viscosity is, for example, 100 Pa · s to 250 Pa · s. In this case, the solder fine powder 3 and the polybutene 4 are mixed at a ratio of about 90 wt% and about 10 wt%, or are mixed at a ratio of about 50 vol%.

In the above solder paste 2 production process, the decomposition temperature is widened by forming the polybuden 4 mixed with the solder fine powder 3 with two or more organic materials having different average molecular weights. In addition, it is not necessary to use multiple types of liquid organic materials as long as they gradually decompose in the process of increasing the solder reflow temperature from the second temperature T ₂ to the third temperature T ₃ above the melting point of the solder. Is not to be done.

  The solder paste 2 formed by the above steps is patterned by the following method to join components. Note that the components include various components that can be mounted on a substrate (base) by a semiconductor chip, an LSI package, an electronic component, or other solder.

  FIGS. 3A to 3F show a process until a component is mounted on a substrate via solder in the component mounting method according to the embodiment of the present invention.

  First, as shown in FIG. 3A, a substrate 11 on which metal patterns 12a to 12d such as wirings and conductive pads are formed is placed on a mounting table 10 for solder paste printing.

  Subsequently, as shown in FIG. 3B, a metal mask 14 having windows 13a to 13d at positions corresponding to the component connection regions of the metal patterns 12a to 12d on the substrate 11 is prepared. And the metal mask 14 and the board | substrate 11 are aligned so that the component connection area | region of the windows 13a-13d and the metal patterns 12a-12d may correspond.

  Subsequently, as shown in FIG. 3C, the solder paste 2 described above is supplied onto the metal mask 14, and then the squeegee 15 is slid along the upper surface of the metal mask 14 in an ambient temperature. Thereby, the solder paste 2 on the metal mask 14 is transferred onto the metal patterns 12a to 12d through the windows 13a to 13d by the extrusion of the squeegee 15.

  Thereafter, as shown in FIGS. 3D and 3E, when the metal mask 14 is removed from the substrate 11, the solder paste 2 becomes a plurality of solder paste layers 2a to 2d having the same shape as the windows 13a to 13d. Are left on each of the metal patterns 12a to 12d.

  After that, as shown in FIG. 3F, for example, the first terminal 16a (17a) and the second terminal 16b (17b) of the component 16 (17) such as a resistance element and a capacitance element are respectively connected to different solders. It is placed on the paste layers 2a, 2b (2c, 2d). In this case, the component 16 (17) is mounted due to the adhesiveness of the solder paste 2.

  The solder paste layers 2a to 2d on which the components 16 and 17 are placed as described above are joined using the reflow apparatus illustrated in FIG.

  In the reflow apparatus, a heating chamber 21, a melting chamber 22, and a cooling chamber 23 are disposed along the direction in which the substrate 11 is transported by the substrate transport plate 20, and shutters 24 a and 24 b are disposed between the substrate transport paths inside them. Is attached so that the melting chamber 22 can be hermetically sealed. Further, shutters 24c and 24d are disposed at the substrate carry-in port of the heating chamber 21 and the substrate carry-out port of the cooling chamber 23, respectively, but these are not essential.

  The heating chamber 21 is provided with a first heater 25 surrounding the substrate transfer path and a first nitrogen gas supply pipe 26 for supplying nitrogen gas therein. The first heater 25 is controlled by the control unit 40 so as to heat the substrate 11 being transported from room temperature to near the volatilization temperature of polybutene.

  The melting chamber 22 is supplied with a second heater 27 surrounding the substrate transfer path, a second nitrogen gas supply pipe 28 for supplying nitrogen gas therein, and a formic acid gas at several tens to several thousand ppm. A formic acid supply pipe 29, an air supply pipe 30 that is disposed closer to the substrate carry-out side than the formic acid supply pipe 29 and supplies oxygen to the interior at several ppm to several percent, and a substrate carry-out side closer to the air supply pipe 30 And a first formic acid gas absorption pipe 32 that introduces the formic acid gas into the formic acid gas combustion device 31. A mechanism for depressurizing the melting chamber 22 may be provided.

  The first nitrogen gas supply pipe 26 and the second nitrogen gas supply pipe 28 are connected to an inert gas supply unit 39.

  Outside the melting chamber 22, the flow rate of formic acid gas supplied from the formic acid gas generator 33 to the formic acid supply pipe 29, the flow rate of air supplied from the air blowing part 34 to the air supply pipe 30, and the second heater 27 The control unit 40 controls the temperature and the amount of formic acid absorbed by the formic acid gas fuel device 31 through the first formic acid gas absorption pipe 32.

  Further, the cooling chamber 23 is provided with a cooling temperature adjuster (heater) 35 surrounding the substrate transport path and a second formic acid gas absorption pipe 36 for recovering formic acid generated from the substrate 11 in a region near the melting chamber 22. ing. The second formic acid gas absorption pipe 36 is connected to the formic acid gas combustion device 31, and the formic acid absorption amount is controlled by the control unit 40. Further, the temperature of the cooling temperature adjuster 35 is adjusted by the control unit 40. Note that nitrogen gas may be introduced into the cooling chamber 23 as an inert gas.

  In addition, although the heating chamber 21, the melting chamber 22, and the cooling chamber 23 are comprised separately from three chambers, you may comprise one chamber which has those functions together.

  In such a solder reflow apparatus, the temperature of the substrate 11 is controlled by the control unit 40 according to the temperature distribution and gas introduction sequence as shown in FIG.

  First, after the substrate 11 on which the components 16 and 17 are mounted on the solder paste layers 2a to 2d as described above is placed on the substrate transport plate 20, the heating chamber 21 filled with nitrogen gas which is an inert gas. The shutter 24c is opened from the substrate carry-in port, and the substrate carrying plate 20 is carried in.

Although the substrate 11 is at room temperature at the substrate carry-in port, the temperature rises by the first heater 25 as it is carried inside by the substrate carrying plate 20, and a second temperature T ₂ lower than the melting point T _{1 of} the solder, For example, it is heated to 160 ° C.

Thereafter, the shutter 24 a is opened by the control unit 40, and the substrate 11 is transferred into the melting chamber 22 by the substrate transfer plate 20. In the melting chamber 22 into which nitrogen gas is introduced, the formic acid gas is further introduced from the formic acid supply pipe 29 and the substrate 11 is exposed to the formic acid gas-containing atmosphere. Thus, the solder paste layer 2a~2d and the metal pattern 12a~12d on the substrate 11 heated to a second temperature T ₂ is reduced on the surface due to the formic acid is started.

Further, when the substrate transport plate 20 advances in the melting chamber 22, the temperature of the substrate 11 gradually increases due to the heat of the second heater 27, and the substrate temperature is reached when, for example, 4 minutes elapse from the start of loading into the melting chamber 22. Reaches the melting point (first temperature) T ₁ of the solder, for example, 221 ° C. Further, the second heater 27 rapidly raises the internal temperature from the melting point T ₁ of the solder, raises the substrate temperature to a third temperature T ₃ higher than the melting point, for example, 250 ° C., and holds this for about 1 minute. Then, before the substrate 11 reaches the substrate carry-out port of the melting chamber 22, the introduction of formic acid gas is stopped, oxygen is further introduced from the air introduction supply pipe 30 into the melting chamber 22, and then the cooling chamber 23. The shutter 24b is opened, and the substrate 11 is carried into the cooling chamber 23. In the meantime, the concentration of formic acid in the melting chamber 22 is set to several tens ppm to several thousand ppm.

  By performing the temperature control by the first and second heaters 25 and 27 in the heating chamber 21 and the melting chamber 22 as described above and the gas control of the atmosphere, the solder fine powder 3 in the solder paste layers 2a to 2d and The polybutene 4 changes as shown in FIG. 6 to reflow the solder fine powder 3.

That is, in FIG. 6, first, decomposition and volatilization of polybudene having an average molecular weight of about 300 in the solder paste layers 2a-2d by heating in the heating chamber 21 starts when the temperature reaches a second temperature T ₂ , for example, 160 ° C. . Further, in the adjacent melting chamber 22, the polybden having an average molecular weight of 30 continues to decompose and volatilize during 4 minutes when the temperature of the substrate 11 reaches the first temperature T ₁ . In the initial period of 4 minutes, formic acid gas is sprayed into the melting chamber 22 from the formic acid supply pipe 29, and the formic acid is permeated into the gaps between the fine solder powders 3 caused by the volatilization of the polybuden to reduce.

Subsequently, when the temperature of the substrate 11 is heated to the first temperature T ₁ , the polybuden having an average molecular weight of about 300 is further volatilized and almost disappears.

  Thus, the exposure amount of the fine solder powder 3 increases as the volatilization amount of the polybudene having an average molecular weight of 300 increases.

When the temperature of the substrate 11 reaches the first temperature T ₁ , that is, the melting point of the solder, the fine powder 3 of the solder starts to melt and connect to each other. Further, the temperature of the substrate 11 changes from the first temperature T ₁ to the third temperature T _3. This time, polybuden having an average molecular weight of about 500 starts to decompose and volatilize, and as the amount increases, the fine powder 3 of solder is further reduced by formic acid gas and the amount linked by melting finally increases. After the temperature of the substrate 11 reaches the third temperature T ₃ , polybden having an average molecular weight of about 500 is decomposed and volatilized for a predetermined time, for example, 1 minute, and almost disappears.

Further, at the end of the time for holding the third temperature T ₃ for 1 minute, oxygen is introduced from the air supply pipe 30 to accelerate the volatilization and subsequent decomposition of the remaining polybutene.

Thereafter, clean air or the like is further blown from the air supply pipe 30 to the substrate 11 to cool the substrate 11 and to disperse the formic acid gas.
Thereafter, the shutter 24 b at the substrate exit of the melting chamber 22 is opened, and the substrate transport plate 20 is moved to the cooling chamber 23. Again, the formic acid gas left on the substrate 11 on the substrate transport plate 20 is removed by the second formic acid gas absorption tube 36. Again, clean gas may be sprayed from the air supply pipe 30 onto the substrate 11.

  The molten solder fine particles 3 are cooled by the cooling temperature adjuster 35, pass through the freezing point, and further drop in temperature to be integrated into a substantially ball shape. Thereafter, the shutter 24 d on the substrate carry-out side of the cooling chamber 23 is opened, and the substrate 11 is carried out by the movement of the substrate carrying plate 20.

  By the way, formic acid gasifies 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 11 is made of an organic material, the substrate 11 does not burn or decompose due to the formation of a reducing atmosphere. Thereby, it is possible to use as reducing gas at the temperature of 300 degrees C or less.

  Further, the chip parts 6, 7 and the like are mounted on the substrate 11 using the adhesive solder paste 2 kneaded with the solder fine powder 3 by the polybden 4 which is an organic material having no flux property as described above. By reflowing the solder fine powder 3 in a reducing formic acid gas, the components 16 and 17 are connected to the metal patterns 12a to 12d on the substrate 11 within the heat resistance range of the substrate 11 without flux residue. Is possible.

  In addition, since the solder paste 2 according to the present embodiment uses polybutene that starts to decompose and volatilize below the melting point of the solder, that is, an organic material, the organic paste can be maintained at a temperature above the melting point of the solder for an arbitrary time. The material will be completely decomposed and no residue will remain on the solder joints.

As described above, the formic acid gas serves as a gaseous flux, and the solder paste serves to temporarily fix the solder while supplying the solder to the connection part of the chip component. The formic acid gas is sprayed in the vicinity of the first temperature T ₁ at which the organic material decomposes, and the formic acid gas is gradually infiltrated through the gap where the organic material polybutene is partially volatilized to form the solder fine powder 3 and the metal pattern of the substrate 11. A good solder wettability can be realized by bringing the formic acid gas into contact with the surface of the metal and reducing the oxide film of both.

Further, when oxygen is introduced into the melting chamber 22 from the air supply pipe 30 before the shutter 24 b is opened and the substrate 11 heated to the third temperature T ₃ is transferred from the melting chamber 22 to the cooling chamber 21, the substrate 11. The decomposition of the remaining organic material, polybuden, is further accelerated.

The substrate 11 carried into the cooling chamber 23 is lowered from the third temperature T ₃ by the temperature regulator 35, passes through the solidification temperature, is rapidly cooled to about 120 ° C., and is further gradually lowered to 110 ° C. The The parts 16 and 17 and the metal patterns 12a to 12d are joined by soldering by such reflow processing.

In solder reflow process as described above, gradually exposing the solder particles 3 by gradually volatilizing the polybutene is an organic material from the solder paste layer 12a~12d to reach the third temperature T ₃ higher than the melting point Since the reduction and integration are gradually performed, rapid integration of the solder fine powder 3 is avoided, thereby preventing the Manhattan phenomenon.

  That is, if the polybutene volatilizes rapidly during the heating using the furnace, the timing at which the solder spreads between the terminals of the components may be slightly different. For example, when the solder wetting and spreading of one end of the chip capacitor is faster than that of the other end, the so-called Manhattan phenomenon may occur due to the surface tension of the solder of the previously wetted terminal, and the component may be vertically stacked.

  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, the solder paste 2 according to this embodiment uses an organic material that decomposes below the melting point of the solder and starts to volatilize, and the organic material is completely decomposed by holding it at a temperature above the melting point of the solder for an arbitrary time. As a result, no residue remains on the solder connection.

  The pattern of the solder paste 2 may be formed on the metal patterns 12a to 12d by a dispensing method in addition to printing as shown in FIG.

By the way, as shown in FIG. 7, the substrate 11 is carried from the heating chamber 21 to the melting chamber 22, and after spraying formic acid, the temperature of the substrate 11 is continuously and rapidly increased to a third temperature T ₃ , for example, 250 ° C. or more. The third temperature T ₃ may be maintained for a long time. This also prevents the occurrence of the Manhattan phenomenon and cleans the solder joints as described above.

  Next, features of the embodiment of the present invention will be added.

(Supplementary Note 1) Solder fine powder that melts at a first temperature and liquid at room temperature, starts to volatilize and decompose at a second temperature lower than the first temperature, and a third temperature higher than the first temperature is set to the first temperature. Solder paste characterized by being mixed with an organic material that can be decomposed by holding for a period of time.
(Supplementary note 2) The solder paste according to supplementary note 1, wherein the organic material comprises a plurality of materials having different decomposition temperatures.
(Supplementary note 3) The solder paste according to supplementary note 1, wherein the second temperature is higher than normal temperature.
(Appendix 4) The substrate on which the component is mounted via the solder paste according to any one of Appendix 1 to Appendix 3 is heated to the second temperature in an inert gas-containing atmosphere into which an inert gas is introduced. A step of decomposing the organic material in the solder paste; a step of placing the substrate at the second temperature in a formic acid-containing atmosphere containing formic acid vapor; and a step of moving the substrate in the formic acid-containing atmosphere from the third temperature. Raising the temperature to a higher temperature and holding for at least the first time to decompose to remove the organic material and melt and integrate the fine powder of the solder; and the base to the first And a step of cooling the solder by lowering the temperature to 2 or lower.
(Supplementary Note 5) The temperature at which the base is cooled from the third temperature to the second temperature or lower is equal to or higher than the boiling point of formic acid, and the atmosphere for cooling the solder is a cooling atmosphere for removing the formic acid from the base. The component mounting method according to Supplementary Note 4, wherein:
(Supplementary note 6) The component mounting method according to supplementary note 5, wherein clean air is introduced into the cooling atmosphere.
(Supplementary note 7) The component mounting method according to any one of supplementary notes 4 to 6, wherein an inert gas is introduced into the formic acid-containing atmosphere.
(Supplementary note 8) The component mounting method according to any one of supplementary notes 4 to 7, wherein the formic acid-containing atmosphere is decompressed.
(Supplementary Note 9) The step of lowering the substrate to the second temperature or lower includes a step of removing formic acid from the substrate in a range lower than the second temperature and not lower than the boiling point of the formic acid. Or the component mounting method according to any one of appendix 7.
(Supplementary note 10) The component mounting method according to any one of supplementary notes 4 to 7, wherein the step of lowering the substrate to the second temperature or less includes a step of removing formic acid from the substrate in a reduced pressure atmosphere. .
(Supplementary note 11) The component mounting according to any one of supplementary notes 4 to 10, wherein the substrate is exposed to an oxygen-containing atmosphere after the substrate is held at the third temperature for the first time or longer. Method.
(Supplementary note 12) The component according to any one of Supplementary notes 4 to 11, wherein the temperature of the base is changed continuously over time while the base is raised from the second temperature to the third temperature. Mounting method.
(Supplementary note 13) The component mounting method according to any one of supplementary notes 4 to 11, wherein the temperature of the base is changed stepwise while the base is raised from the second temperature to the third temperature.
(Supplementary Note 14) A first heater having a first heater that raises the substrate, to which the solder paste according to any one of Supplementary Notes 1 to 3 is supplied to the component connection region, to the second temperature and in which an inert gas is introduced. A region, and the substrate is transported from the first region and the substrate is exposed to a formic acid-containing atmosphere containing formic acid vapor, and the substrate is raised to a temperature higher than the third temperature for a time equal to or longer than the first time. A component mounting apparatus comprising: a second region having a second heater held by the second region; and a third region having a temperature controller that cools the solder by lowering the base body to the second temperature or less.
(Supplementary note 15) The component mounting apparatus according to supplementary note 14, wherein the first region, the second region, and the third region are arranged in the same room.
(Supplementary note 16) The component mounting apparatus according to supplementary note 14, wherein the second region is disposed so as to be able to be sealed from the first region and the third region.
(Supplementary note 17) The component mounting apparatus according to any one of supplementary notes 14 to 16, wherein the second region is provided with an air introduction means closer to the third region.
(Supplementary note 18) The component mounting apparatus according to any one of supplementary notes 14 to 17, wherein formic acid absorbing means is connected to the second region near the third region.
(Supplementary note 19) The component mounting apparatus according to any one of supplementary note 14 to supplementary note 18, wherein formic acid absorbing means is connected to the third region.

FIG. 1 is a perspective view showing a solder paste producing method according to an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the temperature rise time of the solder paste and the amount of volatilization of the polybutene according to the embodiment of the present invention. FIG. 3 is a side view showing a process of mounting a component on a substrate using the solder paste according to the embodiment of the present invention. FIG. 4 is a configuration diagram showing the component mounting apparatus according to the embodiment of the present invention. FIG. 5 is a first sequence showing the relationship between the reflow temperature profile and the introduction of formic acid gas and oxygen gas in the component mounting method according to the embodiment of the present invention. FIG. 6 is a first sequence showing the relationship between the reflow temperature profile and the introduction of formic acid gas and oxygen gas in the component mounting method according to the embodiment of the present invention. FIG. 7 is a diagram showing the decomposition of the organic material and the introduced gas in relation to the reflow temperature profile in the component mounting method according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container 2 Solder paste 2a-2d Solder paste layer 3 Fine solder powder 4 Polybutene (organic material)
11 Substrate 12a to 12d Metal pattern 16, 17 Component 20 Substrate transport plate 21 Heating chamber 22 Melting chamber 23 Cooling chamber 31 Formic acid gas combustion device 34 Air blowing portion 33 Formic acid gas generating portion 39 Inert gas supplying portion 40 Control portion

Claims (5)

A fine solder powder that melts at a first temperature;
It is mixed with an organic material that is liquid at normal 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 first time. Solder paste characterized by   The solder paste according to claim 1, wherein the organic material is made of a plurality of materials having different decomposition temperatures. A substrate on which a component is mounted via the solder paste according to claim 1 or 2 is heated to the second temperature in an inert gas-containing atmosphere into which an inert gas is introduced, and A step of proceeding decomposition of the organic material;
Placing the substrate at the second temperature in a formic acid-containing atmosphere containing formic acid vapor;
In the formic acid-containing atmosphere, the base is raised to a temperature higher than the third temperature and held for a time equal to or longer than the first time to decompose to remove the organic material and melt the fine powder of the solder And integrating them,
And cooling the solder by lowering the substrate to the second temperature or lower.   4. The component mounting method according to claim 3, wherein the substrate is exposed to an oxygen-containing atmosphere after the substrate is held at the third temperature for the first time or longer. A first region having a first heater for raising the substrate to which the solder paste according to claim 1 or 2 is supplied to the component connection region to the second temperature and into which an inert gas is introduced;
The substrate is transported from the first region and the substrate is exposed to a formic acid-containing atmosphere containing formic acid vapor, and the substrate is raised to a temperature higher than the third temperature and held for a time equal to or longer than the first time. A second region having a second heater;
And a third region having a temperature regulator for cooling the solder by lowering the substrate to the second temperature or lower.

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