JP2001320163A - Reflow device and its board heating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To collectively reflow-solder parts large in heat capacity, too, at the same time, while protecting electronic parts low in heat resistance temperature. SOLUTION: This reflow device is so arranged as to heat the whole face to be heated of a substrate 1 by blowing hot blast to it in roughly equal condition, and also to supply the specified section of the substrate 1 with more hot blast energy than other section by blowing hot blast partially to it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating a substrate of a reflow apparatus for soldering electronic components to a printed circuit board and its structure.

[0002]

2. Description of the Related Art Conventionally, a substrate heating method of a reflow apparatus for soldering and mounting electronic components on a printed circuit board includes a heating furnace while continuously transporting a substrate at a constant speed from an entrance to an exit of the reflow apparatus. The method of heating the entire board by passing through the body part, or the method of directly and locally blowing hot air in the post-attachment step for post-installation of parts that are difficult to raise the temperature by heating the entire board, for example, QF having a large heat capacity
There is known a method in which a component such as P, which cannot be reflowed collectively by heating the entire board at the same time as other surface-mounted components, is locally retrofitted using hot air.

FIG. 5 shows a method of retrofitting a component which cannot be reflowed at one time, 1 is a printed circuit board, 1a
Denotes various electronic components mounted on the substrate 1 and 1c denotes a retrofit electronic component (for example, QF
P), 2a are hot air blowing nozzles for locally blowing hot air to the retrofit electronic component 1c, and 3 is a heater provided in the middle of the path 2 for sending air to the hot air blowing nozzle 2a.

[0004] In such a configuration, the lead portion 1 of the retrofit electronic component 1c on the substrate 1 that cannot be reflowed collectively.
b is locally heated by hot air from the hot air blowing nozzle 2a and soldered.

[0005]

However, the above-described conventional hot air local heating method has a problem in that the number of steps increases due to the retrofitting operation, and energy loss increases due to reheating of room temperature air by a heater.

[0006] In the usual method of heating the whole substrate, various electronic components are mounted on the mounting substrate, and a difference in heat capacity occurs due to the disposition of the components on the substrate. Since the time is specified, it is necessary to minimize the temperature variation on the substrate within a certain period of time. There is a problem that a substrate that cannot be accommodated within a predetermined range comes out.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a reflow apparatus and a substrate heating method for protecting an electronic component having a low heat-resistant temperature and simultaneously reflow soldering an electronic component having a large heat capacity. The purpose is to provide.

[0008]

In order to achieve the above object, a substrate heating method for a reflow apparatus according to the present invention comprises the steps of: (a) mounting a printed circuit board on which electronic components are mounted and cream solder is applied to joints; In the substrate heating method of the reflow apparatus, in which the substrate is heated by blowing hot air while being held at a predetermined position in the furnace body portion, the entire heated surface of the substrate is heated by blowing hot air in a substantially uniform state,
It is characterized in that hot air is blown locally to a specific portion of the substrate to supply more hot air energy than other portions.

Further, the reflow apparatus of the present invention has a transfer section for transferring a printed circuit board on which electronic components are mounted and cream solder is applied to a joint, a furnace section for heating the board, and a heating section. A substrate holding portion for holding the substrate at a predetermined location, a hot air blowing component for heating the entire heated surface of the substrate held at the predetermined location by blowing hot air in a substantially uniform state, and a hot air blowing component And a nozzle component configured to locally blow hot air to a specific portion of the substrate disposed between the held substrate and to supply more hot air energy to other portions. I have.

[0010] In such a method and apparatus, hot air is blown over the entire heated area of the substrate in a substantially uniform state, so that the heating of the entire substrate is matched with the temperature rise of the electronic component having a low heat-resistant temperature, and the heat capacity is reduced. For electronic components such as large QFPs, by supplying hot air more locally than by other parts, heating is performed by blowing hot air locally so as to compensate for insufficient heating temperature by heating the entire substrate. Can be promoted. In this way, by increasing the hot air energy applied to a heated part of an electronic component such as a QFP having a large heat capacity, an electronic component having a large heat capacity while protecting a weak heat-resistant electronic component having a small heat capacity and a low heat resistance temperature (for example, an aluminum electrolytic capacitor). In addition, simultaneous reflow soldering can be performed by heating the entire unit, eliminating the need for a post-installation process, simplifying the soldering process, and eliminating the need for reheating during post-installation. Is done.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some preferred embodiments of the present invention will be described below with reference to FIGS. 1 to 4 to provide an understanding of the present invention.

In the reflow apparatus shown in FIG. 1, a printed circuit board 1 on which electronic components 1a are mounted and cream solder is applied to joints, a transfer section 4 for transferring the board 1, and a transferred board 1 And a furnace body 5 for heating the substrate 1. The furnace body 5 for heating the substrate 1 is provided with a first preheating section 5
a, a second preheating section 5b, and a reflow section 5c.

The substrate 1 transferred to the furnace body 5 is
After being preheated by the preheating section 5a and the second preheating section 5b, the preheating is performed by the reflow section 5c to perform reflow soldering.
In the reflow section 5c shown in FIG.
A stopper 6 is provided as a substrate holding unit for holding the substrate 6 in a predetermined place. The substrate 1 preheated by the second preheating section 5b is stopped by the stopper 6 at a predetermined position in the furnace inside the reflow section 5c for a predetermined time.

The reflow unit 5 c reaches a predetermined temperature between the hot air blow-out component A for blowing hot air in a substantially uniform state over the entire heated area of the substrate 1 and the substrate 1 held by the stopper 6. And a nozzle component B configured to blow hot air locally onto a specific portion of the substrate 1 not to supply more hot air energy than other portions.

The hot air blow-out component A is provided with an infrared heater 9 as a heat source, a fan 8 disposed above the infrared heater 9 and rotated by a drive motor 7, and disposed below the infrared heater 9. Hot air blowing chamber 10
And a mask plate 12 held in the hot air blowing chamber 10 and having a large number of hot air outlets 11, and a temperature detection sensor 13 for keeping the hot air at a constant temperature.

In the reflow section 5c, the fan 8
The air blown from the heater 9 is heated by the heater 9 to become hot air, and this hot air is blown out from the hot air blowing port 11 in a substantially uniform state toward the entire heated area of the substrate 1 and thereafter circulates in the furnace.

As shown in FIG. 2, the hot air blow-out components A are disposed above and below the substrate 1, respectively.
By blowing hot air substantially uniformly over the area equal to or larger than the area of the substrate 1 from above and below the substrate 1,
Can be uniformly heated to a predetermined temperature in a short time.

As shown in FIGS. 2 and 3, the nozzle structure B is provided with a pipe 14 for receiving the pressure-fed air between the upper hot-air blow-out component A and the substrate 1. A plurality of blowout holes 15 for blowing hot air are provided at positions corresponding to positions immediately above a specific portion of the substrate 1 which does not reach a predetermined temperature.

The pipe 14 in the example shown in FIG. 3 is an electronic component (for example, QFP) 1c having a large heat capacity that is unlikely to rise in temperature.
The pipe 14 is formed by being bent into a square shape so as to face the lead portions 1b provided on the four sides, and the outlet hole 15 is formed on the lower surface of the pipe 14 so as to blow hot air toward the lead portion 1b.

The temperature of the hot air blown from the outlet 15 is set to a temperature substantially equal to or slightly higher than the ambient temperature in the furnace, and the wind speed is higher than the speed of the hot air blown from the hot air outlet 11. It is set to high speed. As means for raising the temperature of the hot air blown out from the blowout holes 15 as described above, the air inside the furnace is received and circulated for use (in this case, it is preferable to arrange a heater in the circulation path). And means for increasing the length of the pipe or heating the air introduced from another location with a heater, as described later.

Accordingly, the air blown out from the blowout holes 15 is heated at a higher speed than the hot air blown from the hot air blowout component A, which heats the entire heated area of the substrate 1 in a substantially uniform state. Of the electronic component 1c having a large heat capacity, the heat transfer efficiency of the lead 1b is increased, and a predetermined temperature rise is secured. As described above, the temperature rise is promoted for the electronic component 1c having a large heat capacity by utilizing the difference in the heat transfer efficiency, and the temperature rise is determined by heating the entire weakly heat-resistant component 1a having a small heat capacity.

In another embodiment of the present invention shown in FIG. 4, the pipe 14 is formed so that its pipe path becomes longer in the furnace of the reflow section 5c, and the air in the pipe 14 is It is designed to be heated in an atmosphere.

A heater 3 is provided in the introduction path 2 for introducing air into the pipe 14, and a temperature detection sensor 16 is provided downstream of the heater 3 so that the temperature of air blown out of the pipe 14 can be controlled by a predetermined value. It is controlled so that it becomes temperature.

An aluminum electrolytic capacitor and a QFP are obtained by a heating method using the reflow apparatus configured as shown in FIG. 2 (the method of the present invention) and a conventional overall heating method (the conventional method).
The substrate on which was mounted was heated, and its temperature profile was measured. The results shown in (Table 1) were obtained.

[0025]

[Table 1] As is clear from Table 1, the temperature difference of the reflow peak value was 35 ° C. in the conventional method, but the temperature difference could be reduced to 11 ° C. in the method of the present invention.

The present invention can be configured in various modes in addition to the embodiments described above. For example, if a plurality of types of pipes 14 having hot air blowing holes 15 formed in accordance with the arrangement of a specific portion of the substrate 1 are provided, and these are configured to be replaceable, various types of printed circuit boards 1 may be provided. Can be handled. The configuration for heating the substrate in the first preheating section 5a and the second preheating section 5b can be the same as the configuration for heating the substrate in the reflow section 5c described in the above embodiment.

[0027]

According to the present invention, a QFP having a large heat capacity is provided.
By increasing the heat transfer coefficient of specific parts of electronic components such as, it protects weak heat-resistant electronic components with small heat capacity and low heat resistance (for example, aluminum electrolytic capacitors), and also simultaneously heats components with large heat capacity simultaneously by whole heating and batch reflow soldering Since it can be attached, a post-attachment step is not required, and the soldering step is simplified. In addition, reheating at the time of post-attachment is not required, and energy saving is achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a reflow device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a reflow unit.

FIGS. 3A and 3B show a main part of a nozzle constituting part, wherein FIG. 3A is a plan view and FIG.

FIG. 4 is a plan view showing another example of the nozzle component.

FIG. 5 is a schematic diagram showing a conventional hot air local heating configuration in the past.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 1a Electronic component 1b Lead part 1c Electronic component with large heat capacity 2 Introduction path 3 Heater 4 Transport part 5 Furnace part 5a First preheating part 5b Second preheating part 5c Reflow part 6 Substrate stopper 7 Drive motor 8 Fan 9 Heater 11 Hot air outlet 13 Temperature detection sensor 14 Pipe 15 Air outlet 16 Temperature detection sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B23K 101: 42 B23K 101: 42 (72) Inventor Masato Hirano 1006 Kazuma Kazuma, Kadoma City, Osaka Matsushita Electric Within Sangyo Co., Ltd. (72) Inventor Atsushi Yamaguchi 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 5E319 AC01 BB05 CC36 CC49 CC58 CD29 CD31 CD35 GG15

Claims (7)

[Claims] 1. A substrate heating method for a reflow apparatus in which a printed circuit board on which electronic components are mounted and cream solder is applied to a joint portion is heated at a predetermined position in a furnace body by blowing hot air. In the method, the entire heated surface of the substrate is heated by blowing hot air in a substantially uniform state, and at the same time, more hot air energy is supplied to other portions by locally blowing hot air to a specific portion of the substrate. A method for heating a substrate in a reflow apparatus, comprising: 2. A transport section for transporting a printed circuit board on which electronic components are mounted and cream solder is applied to a joint portion, a furnace body section for heating the board, and a substrate to be heated held at a predetermined location. A substrate holding portion to be heated, a hot air blowing component for heating the entire heated surface of the substrate held in a predetermined location by blowing hot air in a substantially uniform state, and a substrate holding the hot air blowing component and the hot air blowing component. A reflow device comprising: a nozzle component configured to locally blow hot air to a specific portion of the substrate disposed therebetween to supply hot air energy more than other portions. 3. The reflow apparatus according to claim 2, wherein said hot-air blowing component is provided above and below the substrate. 4. A nozzle comprising a pipe having a plurality of blowout holes for blowing hot air at a position corresponding to a position substantially immediately above a specific portion of a substrate which does not reach a predetermined temperature. The reflow apparatus according to claim 2. 5. The reflow apparatus according to claim 4, comprising a plurality of types of pipes in which the blowout holes are formed in accordance with the arrangement of a specific portion of the substrate, and these are configured to be replaceable. . 6. The reflow apparatus according to claim 4, wherein the pipe has a long pipe path formed in the furnace body, and heats the inside of the pipe at an ambient temperature in the furnace body. . 7. The reflow apparatus according to claim 4, wherein a heater is provided in an introduction path for introducing air into the pipe.