JPH1051130A - Reflow method and equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To collectively solder electronic components mounted on the whole surface of a printed circuit board, with high reliability, without thermal damaging. SOLUTION: One surface of a printed circuit board 1 wherein electronic components are mounted and cream solder is applied to bonding parts is subjected to radiation heating by a panel heater 22. At the same time, from an air outlet 27 of a mask plate 26 installed in a hot air header 25 of a hot air heating means 23, hot air is locally blown against the bonding parts on the one surface of the printed wiring board 1, almost vertically. Thereby reflow soldering is performed. By commonly using the radiation heating, sure soldering is enabled when the temperature of the hot air is made not to exceed the heat resisting temperature of electronic components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow method and apparatus for heating a printed circuit board on which electronic components are mounted and to which cream solder is applied at a joint, remelting the solder and soldering the electronic components. Things.

[0002]

2. Description of the Related Art There are various types of reflow soldering techniques for mounting electronic components on a printed circuit board. For example,
A method of batch soldering surface mount components by reflow,
There are a method in which the surface-mounted components are collectively soldered by reflow and then the insertion-mounted components are locally soldered, and a method in which the surface-mounted components and the insertion-mounted components are locally reflowed and soldered.

A conventional general reflow apparatus for soldering surface mount components collectively by reflow is a method of uniformly heating the entire printed circuit board by hot air heated to a predetermined temperature or radiation heat of a panel heater. Is re-melted and the electronic component is soldered.

As a reflow apparatus for locally heating and reflowing a surface mount component and an insertion mount component, a reflow apparatus as shown in FIG. 6 is known. In FIG. 6, a reflow device 40 is provided with a hot air box 42 for storing gas heated to a temperature at which cream solder is melted at a lower portion of a transfer path 41 of a printed circuit board 51, and a transfer path 41 for the hot air box 42. A plurality of hot air blowing holes 4 are provided so that hot air 46 can be selectively blown only to a necessary portion of the printed circuit board 51 in the opening 43 facing the hot air.
An upper plate 44 on which the printed circuit board 51 is formed is disposed, and a transport means 47 for supplying and discharging the printed circuit board 51 to and from the reflow device 40 is provided.

In the reflow device 40, since the heating is performed locally, partial soldering, soldering of heat-sensitive components, a lead component 52 and a chip component 53 whose lead tips project below the substrate are performed. Can be soldered simultaneously.

[0006]

However, in the configuration of the above-mentioned conventional general reflow apparatus, when a low heat-resistant electronic component is mixedly mounted on the printed circuit board, the printed circuit board is reflowed. Cannot be soldered by batch reflow through soldering, and it is necessary to separately solder weak heat-resistant electronic components, and thus there is a problem that productivity in a mounting process is reduced.

On the other hand, in the reflow apparatus shown in FIG. 6, even the above-mentioned printed circuit board can be soldered in a lump because it is in principle blown locally by hot air and soldered. However, there is a problem that electronic components mounted on the entire surface of the printed circuit board cannot be actually soldered together. That is, in order to perform reflow soldering of an electronic component such as a lead component 52 or a chip component 53 with a reflow apparatus, it takes 2 to 30 seconds.
It is necessary to raise the temperature to around 30 ° C., but in order to secure the necessary amount of heat therefor, approximately 350 ° C.
Hot air of the above temperature is required. As a result, where the temperature of the printed circuit board easily rises even at the soldering point, the temperature of the printed circuit board approaches this hot air temperature, and even if it is a heat-resistant component (for example, the heat-resistant temperature of QFP is 250 ° C.), it exceeds the heat-resistant temperature. If the hot air temperature is lowered to the heat-resistant temperature of 250 ° C. in order to avoid this, the place where the temperature of the printed circuit board hardly rises is not heated to the temperature required for soldering within a predetermined time, and the reliability is high. There is a problem that soldering may not be possible.

The present invention has been made in view of the above-mentioned conventional problems, and provides a reflow method and apparatus which can solder electronic components mounted on the entire surface of a printed circuit board with high reliability without causing thermal damage. It is intended to be.

[0009]

According to the reflow method of the present invention, one surface of a printed circuit board on which electronic components are mounted and cream solder is applied to a joint is radiated and simultaneously heated on one side of the printed circuit board. Hot air is blown locally and almost perpendicularly to the joints on the surface, and reflow soldering is performed. Even if the temperature of the hot air does not exceed the heat resistance temperature of electronic components by using radiant heating, In addition to being able to attach to the joints, it is possible to selectively heat only those joints by blowing hot air locally substantially perpendicularly to the joints, thereby preventing thermal damage to parts other than the joints. Is surely re-melted and soldered.

Further, when the cooling air is blown to a required portion on the other surface of the printed circuit board, the surface on which the weak heat-resistant electronic component is mounted is used as the other surface, and the cooling air is blown to the weak heat-resistant electronic component. Accordingly, the printed circuit board on which the weak heat-resistant electronic components are mounted can be collectively soldered. In addition, even when surface-mounted electronic components are mounted on both sides of the printed circuit board, there is no danger that the bonding solder of the electronic components will be melted by cooling the joints of the electronic components on the lower surface side during reflow, and the lower surface side will be used. Even if the electronic component is not fixed with an adhesive, there is no danger that the electronic component will fall. Therefore, it is possible to eliminate the step of applying the adhesive when mounting the surface mount electronic component.

Further, the reflow apparatus of the present invention includes a radiant heating means for radiantly heating one side of a printed circuit board on which electronic parts are mounted and a solder paste is applied to a joint, and a radiant heating means. And a hot air heating means for locally blowing hot air toward a joint portion on one surface of the printed circuit board which is radiantly heated. By supplying, the reflow method can be implemented.

The hot air heating means forms a flat space in contact with the surface of the radiant heating means on the printed circuit board side, and a blow-out opening is formed on the surface facing the printed circuit board so as to correspond to the junction. A hot air header in which the mask plate is disposed and a hot air supply means for supplying hot air from the side toward the inside of the hot air header, so that the radiant heat by the radiant heating means is applied to the printed circuit board through the hot air header. Radiation can be reliably emitted, and hot air can be reliably blown from the mask plate to the joint locally in a substantially vertical manner.

In the hot air header, a dispersing plate having a large number of ventilation holes dispersed therein is disposed at an interval from the mask plate, and hot air is supplied between the radiant heating means and the dispersing plate from the hot air supply means. By doing so, the flow of hot air in the hot air header can be made uniform by the dispersion plate, and the hot air can be blown uniformly and substantially vertically toward each joint. Further, by applying a black body coating to the mask plate, the amount of radiant heat can be improved.

[0014] Further, by providing a cool air cooling means for blowing a cooling air to a required portion of the other surface of the printed circuit board whose one surface is heated by the radiant heating means and the hot air heating means, the action by the cooling air blowing is provided. Can be played.

[0015] Further, a conveying means for conveying the printed circuit board to the heating section, and a board elevating means for lifting the printed circuit board to a predetermined heating position in the heating section are provided. It is possible to heat the printed circuit board properly at the required position on the other surface of the printed circuit board by disposing the cool air cooling means on the board elevating means. By providing a shut-off plate surrounding the lifted printed circuit board to shut off the heating atmosphere and the cooling atmosphere, the cooling air and the hot air do not interfere with each other, so that the heating and cooling can be performed efficiently and accurately.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the reflow method and apparatus according to the present invention will be described below with reference to FIGS.

In FIG. 1, reference numeral 1 denotes a printed circuit board,
After being pre-heated by the pre-heating unit 4, it is supplied to the main heating unit 5, subjected to reflow soldering, and then carried out by the carry-out conveyor 6. As shown in FIG. 2, the printed circuit board 1
A surface mounting component 2 such as an FP 2A or a chip component 2B and an insertion mounting component 3 such as an aluminum electrolytic capacitor 3A or a switch component 3B are mixed and mounted. The printed circuit board 1 is supplied to the reflow device in a posture in which the body of the insertion mounting component 3 is located on the lower surface side.

Conveyors 7 and 8 as conveying means are provided through the preheating unit 4 and the main heating unit 5, respectively. The conveyor 7 is configured to pass the printed circuit board 1 through the pre-heating unit 4 at a predetermined speed, and the conveyor 8 is fed at a high speed to a predetermined position of the main heating unit 5 and sent out from the predetermined position. Is provided with board pushing means 9 for pushing the printed circuit board 1 at the end of the conveyor 7 into the conveyor 8.

A board stopper 10 for stopping the printed circuit board 1 is provided at a predetermined position of the board conveying path of the main heating section 5, and a printed circuit board 1 is provided below the printed circuit board 1 stopped at the predetermined position. Board raising / lowering means 11 for lifting the printed circuit board to a predetermined heating position, and a cool air cooling means 12 for supporting the printed circuit board 1 at its upper end and blowing cooling air to a required portion to cool the printed circuit board 1 are provided. Reference numeral 13 denotes a blower fan that supplies cooling air to the cool air cooling unit 12.

At the end of the conveyor 8 downstream of the main heating section 5, cooling fans 14 and 15 are provided to blow and cool the printed circuit board 1 from below and above. An exhaust duct 16 is provided between the pre-heating unit 4 and the main heating unit 5 and before and after the pre-heating unit 4.

As shown in FIG. 3, the preheating unit 4 preheats the printed circuit board 1 by flowing hot air from one side of the printed circuit board 1 along the upper surface thereof. A hot-air circulating fan 18 for circulating the hot air, a catalyst 19 provided in the middle of the hot-air circulating path, for burning and purifying a solvent or flux vapor generated from cream solder or the like during heating of the printed circuit board 1, and
A panel heater 20 disposed above the board transfer path by the conveyor 7 for radiantly heating the upper surface of the printed circuit board 1
And an atmosphere exhaust duct 21 disposed below the transport path.

As shown in FIG. 4, the main heating section 5 includes a panel heater 22 as a radiant heating means for the surface of the printed circuit board 1 and a local heater substantially locally directed to a joint of the surface of the printed circuit board 1. A hot air heating means 23 for blowing hot air vertically is provided. The hot air heating means 23
A hot air header 25 forming a flat space 24 in contact with the lower surface of the panel heater 22, and an outlet 27 provided on the surface of the hot air header 25 facing the printed circuit board 1 and corresponding to the joint portion, It is composed of a mask plate 26 formed and further coated with a black body paint, and a hot air supply duct 28 for supplying hot air into the hot air header 25 from one side thereof.

In the hot air header 25, a large number of ventilation holes 29 are provided.
A dispersion plate 30 on which a dispersion is formed is arranged with a space between the mask plate 26 and a hot air supply duct 28 supplies hot air between the dispersion plate 30 and the panel heater 22. The hot air supply duct 28 is provided with a hot air nozzle tube 31 that communicates with a hot air source (not shown) such as a hot air heater and a hot air blower fan, and that blows out hot air substantially uniformly from the entire length.

When the printed circuit board 1 is lifted as indicated by arrow B by the board lifting / lowering means 11 and is positioned at a predetermined heating position indicated by a solid line, the printed circuit board 1
And a cut-off plate 32 for preventing the heating atmosphere in the upper part of the printed circuit board 1 from interfering with the cooling atmosphere caused by the cooling air from the lower cooling air cooling means 12 as indicated by the dashed arrow C. I have.

In the example shown in FIG.
The hot-air supply duct 28 is disposed on one side of the hot-air header 25, but is not limited thereto. For example, as shown in FIG. May be arranged so that hot air from a hot air source is supplied to an appropriate place thereof, so that a more uniform hot air flow can be formed and hot air heating with high accuracy can be achieved. It can be performed.

The operation of the reflow apparatus having the above configuration will be described. The printed circuit board 1 on which the surface mounting components 2 and the insertion mounting components 3 are mounted in a mixed manner is carried into the preheating unit 4 at a constant speed by the conveyor 7, and the upper surface of the printed circuit board 1 is radiated heat from the panel heater 20. The whole is heated to a temperature of around 150 ° C. by the hot air of the side flow. The constant temperature hot air keeps the ambient temperature in the preheating unit 4 constant and circulates the hot air to reduce the load on the hot air heater 17. Although the temperature of the body of the insertion mounting component 3 on the lower surface side of the printed circuit board 1 rises due to heat conduction from the leads on the upper surface of the printed circuit board 1, the atmosphere on the lower surface of the printed circuit board 1 is sucked by the atmosphere exhaust duct 21. Thereby, the room temperature atmosphere is guided to the lower surface side of the printed circuit board 1, and the temperature rise of the body portion is suppressed.

When the pre-heated printed circuit board 1 reaches the end of the conveyer 7, the rear end thereof is pushed by the board pushing means 9 and smoothly moves onto the conveyer 8. The reason that the board pushing means 9 is provided in this way is that the pre-heating unit 4 on which the conveyor 7 runs heats the printed circuit board 1 while continuously transporting the printed circuit board 1.
In the main heating unit 5 where the conveyor 8 runs, the printed circuit board 1 is stopped at a predetermined position by the substrate stopper 10 and is heated to a predetermined heating position by the substrate lifting / lowering means 11 for heating. This is because it is necessary to transport the printed circuit board 1 promptly.

The printed circuit board 1 sent to the main heating section 5 is stopped at a predetermined position by a board stopper 10, and the conveyor 8 is also stopped. Then, the cool air cooling means 12 is raised by the board lifting / lowering means 11, and the printed circuit board 1 is held at its upper end.
Is supported and lifted to a predetermined heating position.

In this state, the upper surface of the printed circuit board 1 is heated through the hot air header 25 by the radiant heating by the panel heater 22, and at the same time, the surface mounting components 2 and Since hot air is locally blown toward the joints such as the lead portions of the insertion-mounted component 3 and is heated substantially vertically, the hot-air having a temperature not exceeding the heat-resistant temperature of the surface-mounted component 2 causes only the joints to have a predetermined temperature. It can be quickly and accurately heated to the temperature, and the cream solder at the joint is re-melted and reflow soldering is performed. As described above, by simultaneously using the radiant heating and the hot air heating, the soldering can be surely performed even if the temperature of the hot air does not exceed the heat resistant temperature of the electronic component. By blowing hot air almost vertically and selectively heating only the joints, the solder at the joints can be reliably re-melted and soldered while preventing thermal damage to the parts other than the joints, Reliable soldering is ensured.

Further, since the cooling air is blown from the cool air cooling means 12 to the body of the insertion mounting component 3 on the lower surface of the printed circuit board 1, the insertion electronic component 3, which is a weak heat-resistant electronic component, is thermally damaged. This is not the case, and the printed circuit board 1 can be collectively soldered.

In the heating, the hot air header 25
By homogenizing the flow of the hot air in the interior by the dispersion plate 30, the hot air can be blown uniformly and substantially vertically toward each joint. Further, by applying a black body paint coating to the mask plate 26, the amount of radiant heat can be improved.
Further, since the printed circuit board 1 is lifted to a predetermined heating position and heated by the substrate lifting / lowering means 11, the printed circuit board 1 can be quickly and accurately heated, and further, the periphery of the printed circuit board 1 raised to the predetermined heating position Since the heating atmosphere and the cooling atmosphere are shut off by the shut-off plate 32 surrounding the cooling air, the cooling air and the hot air do not interfere with each other, so that heating and cooling can be performed efficiently and accurately.

When the predetermined heating is completed, the printed circuit board 1 is lowered to the position of the conveyer 8 and the cool air cooling means 1
2 descends further. The printed circuit board 1 is a conveyor 8
And is cooled out by the cooling fans 14 and 15. Then, the sheet is transferred from the conveyor 8 to the unloading conveyor 9 and transported to the outlet of the reflow device.

[0033]

According to the reflow method of the present invention, as is apparent from the above description, soldering can be reliably performed even when the temperature of the hot air does not exceed the heat resistance temperature of the electronic component by the combined use with the radiation heating. At the same time, by blowing hot air locally and almost vertically toward the joint, only the joint is selectively heated, thereby preventing solder damage at the joint other than the joint while securely soldering the joint. It can be re-melted and soldered.

Further, by blowing cooling air to a required portion on the other surface of the printed circuit board, the printed circuit board with the weak heat-resistant electronic components mounted thereon can be collectively soldered. Even when surface mounted electronic components are mounted on both sides of the printed circuit board,
By cooling the joint of the electronic component on the lower surface side during reflow, there is no danger of falling even if the electronic component is not fixed with an adhesive, thus eliminating the adhesive application step when mounting the surface mount electronic component. You can also.

According to the reflow apparatus of the present invention, the radiant heating means for radiantly heating one surface of the printed circuit board on which the electronic component is mounted and the soldering portion is provided with the cream solder; And a hot air heating means for blowing hot air locally substantially perpendicularly to a joint on one surface of the printed circuit board which is radiantly heated by the means. The reflow method can be performed by supplying a substrate.

In addition, a hot air heating means forms a flat space in contact with the surface of the radiation heating means on the printed circuit board side, and an outlet is formed on the surface facing the printed circuit board so as to correspond to the joint. Hot air header in which the mask plate is disposed, and hot air supply means for supplying hot air from the side toward the inside of the hot air header,
The radiant heat from the radiant heating means can be reliably radiated to the printed circuit board through the hot-air header, and the hot air can be surely blown from the mask plate toward the joint locally substantially vertically.

In the hot air header, a dispersion plate having a large number of ventilation holes dispersed therein is arranged at a distance from the mask plate, and hot air is supplied from the hot air supply means between the radiation heating means and the dispersion plate. By doing so, the flow of the hot air in the hot air header can be made uniform by the dispersion plate, and the hot air can be reliably and substantially perpendicularly and uniformly and appropriately blown toward the joint.

Further, by applying a black body paint coating to the mask plate, the amount of radiant heat can be improved.

Further, by providing a cooling air cooling means for blowing a cooling air to a required portion of the other surface of the printed circuit board whose one surface is heated by the radiant heating means and the hot air heating means, the action of the cooling air blowing is provided. Can be played.

Further, a conveying means for conveying the printed circuit board to the heating section, and a board elevating means for lifting the printed circuit board to a predetermined heating position in the heating section are provided, and the printed circuit board is quickly raised by heating the printed circuit board to the heating position. Heating can be performed accurately.

By arranging the cool air cooling means on the board lifting / lowering means, it is possible to appropriately cool a required portion on the other surface of the printed circuit board.

Furthermore, if a shut-off plate is provided to surround the periphery of the printed circuit board raised to a predetermined heating position by the board elevating means and shut off the heating atmosphere and the cooling atmosphere, the cold air and the hot air do not interfere with each other, so that the cooling air and the hot air do not interfere. Heating and cooling can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an overall schematic configuration of a reflow apparatus according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of the printed circuit board according to the embodiment.

FIG. 3 is a longitudinal sectional view of a preheating unit of the embodiment.

FIG. 4 is a longitudinal sectional view of a main part of a main heating unit of the embodiment.

FIG. 5 shows another configuration example of the main heating unit of the embodiment,
(A) is a longitudinal sectional view of a main part, and (b) is a cross-sectional plan view taken along the line AA of (a).

FIG. 6 is a longitudinal sectional view showing a schematic configuration of a conventional reflow apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 2 Surface mounting component (electronic component) 3 Insertion mounting component (electronic component) 5 Main heating part 8 Conveyor (conveying means) 11 Substrate elevating means 12 Cold air cooling means 22 Panel heater (radiant heating means) 23 Hot air heating means 24 flat space 25 hot air header 26 mask plate 27 outlet 28 hot air supply duct (hot air supply means) 29 ventilation hole 30 dispersing plate 32 cutoff plate 33 hot air supply duct

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Koichi Nagai 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Osamu Matsushima 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Kazuhiro Uji 1006 Odaka Kazuma Kadoma City, Osaka Pref. Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A printed circuit board on which an electronic component is mounted and cream solder is applied to a joint is radiantly heated on one side of the printed circuit board, and is locally directed toward the joint on one side of the printed circuit board. A reflow method characterized by blowing hot air substantially vertically to perform reflow soldering. 2. The reflow method according to claim 1, wherein cooling air is blown to a required portion on the other surface of the printed circuit board. 3. A radiant heating means for radiantly heating one surface of a printed circuit board on which electronic parts are mounted and a solder paste is applied to a joint, and a print radiantly heated by the radiant heating means. A reflow apparatus characterized in that hot air heating means for blowing hot air locally substantially perpendicularly to a joint portion on one surface of a circuit board is provided in parallel with the heating section. 4. The hot air heating means forms a flat space in contact with the surface of the radiant heating means on the printed circuit board side, and the outlet is formed on the surface opposed to the printed circuit board so as to correspond to the joining position and correspond to the joint. 4. The reflow apparatus according to claim 3, further comprising a hot-air header provided with the provided mask plate, and hot-air supply means for supplying hot air into the hot-air header from a side portion thereof. 5. A dispersing plate in which a number of ventilation holes are dispersedly formed in a hot-air header is disposed at an interval from a mask plate so that hot air is supplied from a hot-air supplying unit between the radiant heating unit and the dispersing plate. The reflow apparatus according to claim 4, wherein 6. The reflow apparatus according to claim 4, wherein a black body paint coating is applied to the mask plate. 7. A cooling air cooling means for blowing a cooling air to a required portion on the other surface of the printed circuit board, one surface of which is heated by the radiant heating means and the hot air heating means. 7. The reflow apparatus according to any one of claims 6 to 6. 8. The apparatus according to claim 3, further comprising a transporting unit for transporting the printed circuit board to the heating unit, and a board elevating unit for lifting the printed circuit board to a predetermined heating position by the heating unit. A reflow device according to any one of the above. 9. The reflow apparatus according to claim 8, wherein a cool air cooling means is provided in the substrate elevating means. 10. A shielding plate surrounding a printed circuit board lifted to a predetermined heating position by a board lifting / lowering means to shut off a heating atmosphere and a cooling atmosphere. Reflow equipment.