JPH1051133A - 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 damage. SOLUTION: On one surface of a printed wiring board 1, electronic componenets are mounted, and cream solder is applied to bonding parts. From a hot air head 22, hot air is locally blown against the bonding parts, almost vertically, through hot air nozzles 28. Thereby reflow soldering is performed. At the same time, from a cold air head 23, cold air is locally blown against a necessary part on the one surface of the printed circuit board 1, almost vertically, through a cold air nozzle 29. Thereby solder of the bonding parts is surely refused, and soldering is performed. Thermally weak parts are cooled, and thermal damage is prevented.

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]

SUMMARY OF THE INVENTION A reflow method according to the present invention locally and substantially vertically extends toward a joint on one surface of a printed circuit board on which an electronic component is mounted and cream solder is applied to the joint. Hot air is blown and reflow soldering is performed.At the same time, cold air is blown locally and almost vertically to a required part on one side of the printed circuit board, and the solder is reliably re-melted by blowing hot air to the joint. Soldering, and at the same time, blowing cold air toward heat-sensitive parts other than the joints to prevent the heat damage.

In addition, when the cool 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 which is particularly susceptible to heat is mounted is the other surface, and the cool air is blown to the electronic component. Accordingly, the printed circuit board on which the weak heat-resistant electronic component is 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 is a reflow apparatus provided with a transport unit for transporting a printed circuit board, and a heating unit for heating one surface of the printed circuit board at a predetermined position of a transport path by the transport unit. A hot air header and a cold air header are arranged in a layered manner so as to face the printed circuit board in the heating section, and hot air is locally blown from the hot air header to a joining portion on one surface of the printed circuit board substantially vertically. A hot-air nozzle and a cold-air nozzle that blows cold air from the cold-air header to a desired portion of one surface of the printed circuit board locally and vertically are provided. By supplying the hot air nozzle and the cold air nozzle to a required portion of the printed circuit board from the hot air nozzle and the cool air nozzle, the hot air nozzle and the cool air nozzle are appropriately blown to perform the reflow method. Door can be.

[0012] Further, it is possible to provide a substrate elevating means for lifting the printed circuit board to a predetermined heating position by the heating unit, and to heat the printed circuit board to the heating position quickly and accurately without interfering with the conveying means. By making the lengths of the hot air nozzle and the cold air nozzle different according to the shape and height of the electronic components on the printed circuit board, hot air or cold air can be blown accurately to required locations, and heating or cooling can be performed accurately. Can be cooled.

Further, the surface of the hot air header and the cold air header facing the printed circuit board is formed by a plate having a large number of openings, and hot air nozzles or cold air nozzles are penetrated through the openings at required locations. When the opening is closed with a blind plug, it is possible to easily cope with a change in the type of the printed circuit board by arranging each nozzle in a required opening of the plate.

[0014] Further, by providing an open / close valve in a hot air / cold air supply passage for the hot air header and the cold air header, the opening / closing of the open / close valve controls the hot air and the cool air blowing to perform appropriate heating / cooling. In addition, a desired temperature profile can be obtained by providing an opening / closing control means for programmably controlling the opening of the opening / closing valve.

Further, by providing a cool air cooling means for blowing cool air to a required portion on the other surface of the printed circuit board, it is possible to exert an effect of blowing the cool air to the required portion on the other surface.

[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
Surface mount components 2 such as FP and aluminum electrolytic capacitors 3
A and insertion mounting parts 3 such as switch parts 3B are mixed and mounted. The printed circuit board 1 is supplied to the reflow device in a posture in which the body portion 3a 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 is provided, and a cool air cooling means 12 for supporting the printed circuit board 1 at the upper end thereof and blowing cool air to a required portion for cooling. Reference numeral 13 denotes a fan for supplying cool air to the cool air cooling means 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 pre-heating unit 4 includes a heater 17 for generating hot air and a hot air flowing from one side of the printed circuit board 1 along the upper surface thereof.
A hot air circulation fan 18 for preheating and circulating the hot air, and a catalyst provided in the middle of the hot air circulation path for burning and purifying a solvent or a flux of a flux generated from cream solder or the like during heating of the printed circuit board 1. 19, a panel heater 20 disposed above the board transfer path by the conveyor 7 and radiantly heating the upper surface of the printed circuit board 1;
And an exhaust duct 21 disposed below the transport path.

As shown in FIG. 4, the main heating section 5 has a hot-air header 22 disposed above the printed circuit board 1 which is stopped by the board stopper 10 on the transport path. The cold air headers 23 are arranged in layers. The surface of the hot-air header 22 facing the printed circuit board 1 is formed by a plate 24 having a large number of openings 25 formed thereon, and the surface of the cold-air header 23 facing the printed circuit board 1, that is, the partition wall from the hot-air header 22. Is plate 2
4 is formed of a plate 26 in which an opening 27 is formed so as to coincide with the opening 25. Both plates 2
The openings 25 and 27 of the printed circuit boards 4 and 26 are formed so as to correspond to the solder joint portions of the plurality of types of printed circuit boards 1 and the heat-sensitive portions of the electronic components. The openings 25, 27
May be formed on the entire surface of the plates 24 and 26 so as to be compatible with any type of printed circuit board 1.

Hot air is locally blown from the hot air header 22 to the joint on the upper surface of the printed circuit board 1, in the illustrated example, to the lead joint of the surface mount component 2 and the lead of the insert mount component 3. A hot air nozzle 28 is attached to the plate 24 so as to penetrate the opening 25 corresponding to the above-mentioned joint. Further, the plate 26 of the cool air header 23 and the hot air header are so blown from the cool air header 23 to the body part 2a of the surface mount component 2 on the upper surface of the printed circuit board 1 that is relatively weak to heat that the air is locally blown substantially vertically. A cool air nozzle 29 is mounted through the openings 27 and 25 of the plate 22. These hot air nozzles 2
The length of the cold air nozzles 8 and the cold air nozzles 29 is varied according to the shape and height of the electronic components on the printed circuit board 1 so that hot air or cold air can be blown to the joints and the cooling locations accurately and locally. . A blind plug 30 is attached to the openings 25 and 27 through which the hot air nozzle 28 and the cold air nozzle 29 do not penetrate. Further, the hot air nozzle 28, the cold air nozzle 29 and the blind plug 30 are provided on the outer periphery of the upper end portion thereof with the engagement flange 2 for preventing slipping out.
8a, 29a and 30a are protrudingly provided, and a sealing material 31 is provided at a lower portion thereof to prevent hot air or cold air from leaking.

The cool air cooling means 12 disposed above the board lifting / lowering means 11 also includes a cool air header 32, and the inserted and mounted components 3 on the lower surface side of the printed circuit board 1 are provided from the cool air header 32.
The cold air nozzle 33 is mounted so as to blow the cool air locally substantially vertically toward the body portion 3a.

As shown in FIG. 1, when the printed circuit board 1 is lifted by the board lifting / lowering means 11 and located at a predetermined heating position, the printed circuit board 1 surrounds the printed circuit board 1 and A blocking plate 34 is provided to prevent interference between the upper heating atmosphere and the cooling atmosphere caused by the cool air from the lower cool air cooling means 12.

Further, as shown in FIG.
And a fan 35 for blowing air to the cool air header 23, respectively.
a, 35b are provided, and a hot air generating heater 36 for heating the air supplied to the hot air header 22 is provided. Opening / closing valves 37a and 37b are provided in the hot air supply passage and the cold air supply passage, respectively, and an opening / closing control means 38 for controlling the degree of opening of these on / off valves 37a and 37b in a programmable manner is provided.

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 heater 17. The temperature of the body portion 3a 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, but the atmosphere of the lower surface of the printed circuit board 1 is sucked by the exhaust duct 21. Thus, 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 3a 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, hot air is blown from the hot air header 22 through the hot air nozzle 28 to the surface mounting component 2 and the lead mounting portion of the insertion mounting component 3 on the upper surface of the printed circuit board 1 and substantially vertically. Then, the solder is reliably re-melted and reflow soldered. At the same time, the cold air is locally blown substantially vertically onto the body portion 2a of the surface-mounted component 2 on the upper surface of the printed circuit board 1, so that the surface-mounted component 2 does not exceed the heat-resistant temperature and thermal damage is prevented. Thus, reliable soldering is ensured while preventing heat damage to relatively heat-sensitive components.

At this time, since the printed circuit board 1 is lifted to a predetermined heating position by the board lifting / lowering means 11, the printed circuit board 1 can be quickly and accurately heated, and furthermore, the printed circuit board raised to the predetermined heating position can be heated. Since the heating atmosphere and the cooling atmosphere are cut off by the cutoff plate 34 surrounding the periphery of the substrate 1, the heating and cooling can be performed efficiently and accurately without interference between the cold and hot air.
Further, since the length of the hot air nozzle 28 and the length of the cold air nozzle 29 are made different according to the shape and height of the electronic components on the printed circuit board 1, it is possible to blow hot air or cold air to required portions accurately, and to achieve accuracy. Good temperature control.

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

When the predetermined heating is completed, the printed circuit board 1 is lowered to the position of the conveyor 8, and the cooling 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.

According to the above-described embodiment, the surfaces of the hot air header 22 and the cold air header 23 facing the printed circuit board 1 are connected to the plates 24 and 26 in which a number of openings 25 and 27 are formed.
The hot air nozzle 28 or the cold air nozzle 29 is penetrated through the openings 25 and 27 at the required locations, and the remaining openings 2
Since plates 5 and 27 are closed with blind plugs 30, plates 24 and 27
25 is all kinds or plural kinds of printed circuit boards 1
And the hot air nozzles 2 are provided in the openings 25 and 27 at required locations according to the type of the printed circuit board 1.
By disposing the nozzle 8 or the cool air nozzle 29, it is possible to easily cope with a change in the type of the printed circuit board 1.

The hot air header 22 and the cold air header 23
Opening and closing valves 37a, 37
b, these on-off valves 37a, 37b
The heating and cooling can be appropriately performed by controlling the blowing of the hot air and the cold air by opening and closing. Further, by controlling the opening degree of the opening / closing valves 37a and 37b by the opening / closing control means 38 in a programmable manner, a desired temperature profile can be obtained, and highly reliable reflow soldering can be realized.

[0036]

According to the reflow method of the present invention, as is apparent from the above description, the reflow soldering is performed by blowing hot air locally substantially perpendicularly to the joint on one surface of the printed circuit board. At the same time, cold air is blown locally and almost vertically toward the required part on one side of the printed circuit board, so that the solder at the joint can be reliably re-melted and soldered. Thermal damage can be reliably prevented.

Further, when a cool 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 particularly weak to heat is mounted is set as the other surface, and the cool air is blown to the electronic component. Accordingly, the printed circuit board on which the weak heat-resistant electronic component is mounted can be collectively soldered.

Further, according to the reflow apparatus of the present invention, the hot air header and the cold air header are arranged in the heating section in a multilayer manner so as to face the printed circuit board, and the hot air header is joined to one surface of the printed circuit board. Since a hot air nozzle that blows hot air locally substantially vertically toward a location and a cool air nozzle that blows cold air locally substantially vertically from a cold air header to a desired location on one surface of a printed circuit board are provided. The reflow method can be implemented by appropriately blowing hot air or cold air from a hot air nozzle and a cold air nozzle to a required portion of a printed circuit board.

Further, by providing the board raising / lowering means for lifting the printed circuit board to a predetermined heating position by the heating unit, the printed circuit board can be heated quickly and accurately by lifting the printed circuit board to the heating position. In addition, by making the length of the hot air nozzle and the length of the cold air nozzle different according to the shape and height of the electronic components on the printed circuit board,
Hot and cold air can be blown precisely to the required places,
Temperature control can be performed accurately.

Also, the surface of the hot air header and the cold air header facing the printed circuit board is formed by a plate having a large number of openings, and hot air nozzles or cold air nozzles are arranged through necessary openings, and the remaining nozzles are provided. By closing the opening with the blind plug, it is possible to easily cope with a change in the type of the printed circuit board.

Further, by providing an open / close valve in a hot air / cold air supply passage for the hot air header and the cold air header, the opening / closing of the open / close valve controls the blowing of the hot air and the cold air to perform appropriate heating / cooling. In addition, a desired temperature profile can be obtained by providing an opening / closing control means for programmably controlling the opening of the opening / closing valve.

Further, by providing a cool air cooling means for blowing cool air to a required portion on the other surface of the printed circuit board, it is possible to exert an effect of blowing the cool air to the required portion on the other surface.

[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 is a schematic configuration diagram of hot air and cold air supply means of the same embodiment.

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 Insert mounting component (electronic component) 5 Main heating part 8 Conveyor (conveying means) 11 Substrate lifting / lowering means 12 Cold air cooling means 22 Hot air header 23 Cold air header 24 Plate 25 Opening 26 Plate 27 Opening 28 Hot air nozzle 29 Cold air nozzle 30 Blind plug 37a Open / close valve 37b Open / close valve 38 Open / close control means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichi Nagai 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. A printed circuit board, on which electronic components are mounted and to which a solder paste is applied at a joint portion, is reflow soldered by blowing hot air locally substantially toward a joint portion on one surface of the printed circuit board. A reflow method characterized in that cold air is locally blown substantially vertically toward a required portion of one surface of a substrate. 2. The reflow method according to claim 1, wherein cool air is blown to a required portion on the other surface of the printed circuit board. 3. A transport means for transporting a printed circuit board on which electronic components are mounted and cream solder is applied to a joint, and heating for heating one surface of the printed circuit board at a predetermined position of a transport path by the transport means. In the reflow device in which the hot air header and the cold air header are arranged in the heating section so as to face the printed circuit board, the hot air header and the cold air header are locally directed from the hot air header to the joint of one surface of the printed circuit board. A hot air nozzle that blows hot air substantially vertically,
A reflow device, comprising: a cold air nozzle for blowing cold air locally substantially vertically from a cold air header to a required portion on one surface of a printed circuit board. 4. The reflow apparatus according to claim 3, wherein the heating unit is provided with a board elevating means for lifting the printed circuit board from the transport path to a predetermined heating position. 5. The reflow apparatus according to claim 3, wherein the length of the hot air nozzle and the length of the cold air nozzle are varied according to the shape and height of the electronic component on the printed circuit board. 6. A hot air header and a cold air header, each of which faces the printed circuit board, are formed of a plate having a large number of openings, and hot air nozzles or cold air nozzles are arranged through openings at required locations. The reflow apparatus according to any one of claims 3 to 5, wherein the opening is closed with a blind plug. 7. The reflow device according to claim 3, wherein an on-off valve is provided in a supply passage of hot air and cold air for the hot air header and the cold air header. 8. The reflow apparatus according to claim 7, further comprising an opening / closing control means for programmably controlling the opening of the on-off valve. 9. The reflow apparatus according to claim 3, wherein a cool air cooling means for blowing cool air to a required portion on the other surface of the printed circuit board is provided.