JPH088529A - Reflow furnace - Google Patents

Abstract

(57) [Abstract] [Purpose] Regarding a reflow furnace for soldering mounted components to the substrate by passing the substrate on which the mounted components are placed in the paste solder printing section through the preheating section and main heating section by the feeding mechanism. The optimum heating should be performed for each mounted component. [Structure] A measuring means is provided in front of the preheating unit to measure the size and position of each mounted component on the board, and when the board passes through the main heating unit, the main heating unit is corresponding to the size and position. Each mounting component is heated by the spot heating unit provided in the unit, or an infrared spectrometer is provided between the preheating unit and the main heating unit instead of providing the above measuring means, and the temperature obtained from this infrared spectrometer By similarly extracting the size information and the position information of the same mounted component based on the difference information, each mounted component is similarly heated by spot heating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow furnace, and more particularly to a reflow furnace as a heating device for reflow soldering after mounting a mounting component such as an electronic component on a printed circuit board (hereinafter simply referred to as a substrate). Is.

In order to solder a mounting component to a board, it is necessary to heat the board in a reflow furnace to melt the solder. In recent years, SMT (Surface Mount Tec) has been adopted.
SMD with various forms of mounted parts with the progress of hnology)
Since (Surface Mount Device) has been developed and its size has become extremely large and small, it is necessary to set the temperature inside the reflow furnace according to the mounted components.

[0003]

2. Description of the Related Art FIG. 11 is a side view schematically showing the structure of a conventionally known reflow furnace. In FIG. 1 (1), the reflow furnace 1 is a substrate transfer conveyor (chain) as a feeding mechanism. ) 2, a front conveyor 4 and a rear conveyor 5 are installed on both sides of the substrate transfer conveyor 2.

The substrate carrying conveyor 2 is a mechanism for intermittently feeding the substrate 20 from the left side to the right side in the figure in a fixed size unit by a control system which will be described later, which receives the detection result of the substrate carry-in sensor 6 for stopping the constant size feeding. Has become.

Further, two preheating portions PH1 and PH2 covered by a cover 10 and a main heating portion MH are provided on the substrate feed conveyor 2, and these preheating portions P are further provided.
Each of H1, PH2 and MH2 is equipped with a sheath heater 11 having a length substantially equal to the length of the substrate 20 in the feed direction, and the substrate 20 passing through these heating parts is cooled by a fan 13. .

A mounting component 21 is prepared on the substrate 20, and a paste solder printing section 22 is interposed between the mounting component 21 and the substrate 20.

In such a reflow furnace 1, the substrate 20
Is passed through the preheating parts PH1 and PH2 and the main heating part MH by the constant size feeding mechanism 2, the paste solder 22
Will be melted and the board 20 and the mounting component 21 will be soldered.

In such soldering of the substrate 20, since the heater temperature is important, the preheating portion PH
1, PH2 and the temperature sensor (not shown) provided in the main heating unit MH respectively detect the temperature of the location,
As shown in FIG. 2, a time-temperature profile for the substrate 20 is generated.

If the temperatures detected by these temperature sensors do not match the desired profile, the preset temperatures of the preheating parts PH1 and PH2 and the sheath heater 11 of the main heating part MH are changed, and the substrate 20 is reflowed again. The same operation is repeated until the desired temperature profile is obtained by introducing the furnace 1.

[0010]

However, even if an attempt is made to obtain the desired temperature profile as described above, it is difficult to obtain a good temperature profile. This is because the mounted parts have various forms as described above, and the small parts and the large parts have different heat capacities, so that a temperature difference occurs in the soldering part of each part. As a result, the desired temperature profile cannot be obtained, and the solder in the soldering portion of the large component has a problem of poor melting.

FIG. 13 shows such a problem. As shown in FIG. 1A, when a large component 211, a medium component 212 and a small component 213 are mixedly mounted on one substrate 20, An example of the temperature difference between the respective components is shown in FIG. 2 (2), and it can be seen that the temperature of the large component 211 is lower than that of the small component 213.

On the other hand, JP-A-2-96394 and JP-A-2-137667
No. 4,288,967, etc., a technique for controlling the heating temperature according to the heat capacity of each substrate has been proposed, but all of them are for controlling the heating temperature for the entire substrate. There is a problem in that it is not possible to control various types of mounted components.

Therefore, according to the present invention, in a reflow furnace for soldering a mounting component to the substrate by passing the substrate on which the mounting component is mounted on the paste solder printing section through the preheating section and the main heating section by a feeding mechanism, The purpose is to perform optimal heating corresponding to each mounted component.

[0014]

[Means for Solving the Problems]

[1] In order to achieve the above object, the reflow furnace according to the present invention (No. 1) includes a means for measuring the size and position of a mounted component provided in a preceding stage of a preheating unit in a predetermined area unit, and a main heating unit. A spot heating unit that is provided and is capable of heating in a predetermined area unit, and controls the spot heating unit in accordance with the size and position obtained from the measuring means when the substrate passes through the main heating unit. And a control means for heating the mounted component.

In this case, the measuring means measures the volume by also measuring the height of the mounting component as the size, and the control means adjusts the spot according to the heat capacity corresponding to the volume of the mounting component. The heating part can be heated.

[2] The reflow furnace according to the present invention (1) is an infrared spectrometer provided between a preheating section and a main heating section for measuring a temperature difference between mounted components passing through the preheating section; The spot heating unit provided in the main heating unit and capable of heating in the predetermined area unit, and the size information and position of the mounted component based on the temperature difference information obtained from the infrared spectrometer when the substrate passes through the main heating unit. Means for extracting information and correspondingly heating the mounted component by the spot heating unit.

[3] In the above-mentioned present invention, the position of the heater of the spot heating section can be adjusted according to the board form of the mounting component, and the feed mechanism connects the board to the preheating section. It is possible to feed only a fixed size when passing through the heating part.

[0018]

[Action]

[1] In the reflow furnace according to the present invention (No. 1),
Before heating in the preheating section, the size and position of the mounted components on the board are measured in units of a predetermined area (mesh) by the measuring means provided in the preceding stage of the preheating section.

After being heated in the preheating section in the same manner as in the conventional case, when it is sent to the main heating section, the main heating section is provided with the spot heating section capable of heating in the above predetermined area unit. When the substrate is sent to the main heating unit, the control unit controls the spot heating unit to heat the mounted component in component units in accordance with the size and position of the mounted component measured in advance.

In this case, the above-mentioned measuring means can measure the height of the mounted component as the size in consideration of the difference in the height of the mounted component, so that the volume of the mounted component can be known. .

Therefore, the control means can heat the spot heating portion in accordance with the heat capacity corresponding to the volume of the mounted component (this is obtained from the relationship between the volume and the heat capacity prepared in advance), and only the area is heated. More accurate component heating can be performed as compared to the case of considering.

[2] According to the reflow furnace according to the present invention (No. 2), the above-mentioned measuring means is not particularly provided, but instead, the preheating part is passed between the preheating part and the main heating part. An infrared spectrometer that measures the temperature of the components is installed, and the size information and position information of each mounted component are extracted from the temperature difference information obtained from this infrared spectrometer, and the board passes through the main heating unit correspondingly. Similarly, each mounting component is heated by the spot heating unit provided in the main heating unit.

It goes without saying that the size information of the mounted component obtained from the temperature difference information by the infrared spectrometer in this case includes the volume information of the entire mounted component.

[3] The position of the spot heater of the spot heating unit can be adjusted according to the board form of each mounted component.

Further, the feeding mechanism, when preheating the substrate, can feed the substrate by a fixed size when passing through the main heating section.

[0026]

【Example】

[1] FIG. 1 shows an embodiment of a reflow furnace according to the present invention (No. 1). Particularly, FIG. 1 (1) shows a schematic side view thereof, and FIG. This corresponds to the view seen from the arrow A in (1).

The difference between this embodiment and the conventional example shown in FIG. 11 is that the X-Y drive type CCD camera 14 as the measuring means and the X for measuring the height of the mounting component 21 are provided in front of the preheating section PH1. -Y drive type laser unit 15 is provided, the size and position of the mounted component 21 on the substrate 20 are measured, and the spot heater 12 as a spot heating unit is provided in the main heating unit MH.

FIG. 2 shows a plan view of the heating section shown in FIG. 1. Particularly, FIG. 1 shows the preheating sections PH1 and PH2.
Of the main heating unit MH is shown in FIG.
Is shown in plan view.

That is, in the preheating parts PH1 and PH2, the sheath heater 11 is attached to the frame body 16 of the preheating part at a right angle to the feeding direction of the substrate 20, and in the main heating part MH, the same as the preheating parts PH1 and PH2. Sheath heater 11
At the same time, spot heaters 12 are provided between the sheathed heaters 11 in a predetermined area unit (cell shape).

FIG. 3 is a perspective view of the main heating section shown in FIG. 2B. As shown in the figure, the sheath heater 11 has a part of a slide hole 17 formed on the side surface of the frame 16 and a part thereof is thin. Since it comes out as a bolt and is fixed by tightening it with a nut 18, it can be moved in the X direction as shown in the drawing, and the spot heater 12 is the same as the sheath heater 11 moves in the X direction. To X
It is possible to move in the Y direction as well as move in the direction.

FIG. 4 shows an embodiment of the spot heating section. First, a xenon lamp 31 as a heating source for the spot heating is provided, the emitted light of this xenon lamp is reflected by a reflector 32, and this spot is spotted. The heater 12 irradiates the mounting component 21 of the substrate 20.

A shutter 3 is attached to each spot heater 12.
3 is provided, and by opening and closing the shutter 33, the emitted light of the xenon lamp 31 reflected by the reflector is given to the mounting component 21 as a light flux 35 through the lens 34. The shutter 33 can be controlled not only to perform an ON / OFF operation but also to an intermediate opening for adjusting the amount of the light flux 35.

FIG. 5 shows a control system of the embodiment of the present invention shown in FIGS.
The output signal of No. 4 is supplied to the control unit 32 via the image processing unit 31, and the output signal of the laser unit 15 is also supplied to the control unit 32.

The control unit 32 is connected to a CPU 33 for carrying out arithmetic processing to be described later to constitute control means, and also performs conveyor control C1, heater control C2, spot heater control C3, etc. as shown in the figure, and an infrared spectrometer. An output signal from (which will be described later) is also received. In addition, these controls C1
Since C3 is a well-known control process, it is omitted here.

Incidentally, as will be described later, the CPU 33 stores beforehand mounting part information such as size and heat capacity, occupancy ratios of large, medium and small parts, and mounting patterns such as temperature conditions as a database.

FIG. 6 shows the CPU 3 according to the present invention (part 1).
3 is a flowchart of the control processing executed in No. 3, and the operation of the above embodiment will be described below with reference to this flowchart.

First, the CPU 33 carries the substrate 20 from the front conveyor 4 to the measuring means constituted by the CCD camera 14 and the laser unit 15 by the constant-size feeding mechanism 2 (step S1). This can be performed by the conveyor control C1 using the output signal of the substrate loading sensor 6.

As a result, the CCD camera 14 and the laser unit 15 scan the substrate 20 on the XY plane to control each output signal (the output signal image-processed by the image processing unit 31 of the CCD camera 14). Unit 32
Will be given to the CPU 33 via. Thereby, the CPU 33 measures the size and position of the mounted component (step S2).

FIG. 7 specifically shows a subroutine for measuring the mounted component 21 by the CCD camera 14 and the laser unit 15. First, the size of the mounted component 21 is measured (step S21), and the substrate is determined from this size and position. A planar mounting map M1 is created in the form as shown.

Further, since the laser unit 15 can generate the height information from the reflected light by emitting the laser light to irradiate the mounting component 21, the above-mentioned planar mounting map M1 is taken into consideration. Mounted component 21
I know the volume of.

Therefore, a component information file (heat capacity for each size) storing the heat capacity for each component volume is obtained in advance,
A matching process is performed between this file and the actually measured volume information, and the mounting map M is created based on the matching process result.
A temperature difference map M2 for the case of uniform reference heating (season heater heating) is created for 1 (step S23).

In this temperature difference map M2, the reference heating level (solder meltable level) which does not require spot heating by the spot heater 12 is shown.
Indicates that the spot heating is required by the difference from the reference heating level as the value becomes smaller.

That is, if the mounting components in the temperature difference map M2 have the same height, for example, one of the shutters 33 shown in FIG. It indicates that it is necessary to open the two shutters 33 for the mounted components having a difference.

On the other hand, in this temperature difference map M2,
The reason why there are different mounted components such as the temperature difference even though they have the same area is that the heights of the mounted components are different as described above. Uniform heating can be realized by increasing the opening of one shutter 33 as compared with the above.

For creating the temperature difference map M2, the CCD camera 14 is used without using the laser unit 15.
It is possible to use only the area of the mounted components (board mounting map M1) according to the above, and in that case, the matching process in step S23 determines which of the squares of the predetermined area each mounting component corresponds to as shown in the figure. Then turn on the shutter 33
/ OFF control is sufficient.

After executing the measurement subroutine S2 in this way, the CPU 33 executes the constant-size feed control for the substrate constant-size feed mechanism 2 (step S3).

Thereafter, the CPU 33 preheats the preheater PH1 under the constantly energized sheath heater 11 to heat the preheater PH1 via the control unit 32 (step S).
4).

After that, the substrate 20 is again fed at a constant size (step S5), and the second preheating is performed under the constantly energized sheath heater 11 in the next preheating portion PH2 (step S6).

Then, the substrate 20 is further fed at a constant size (step S7), and the sheath heater 11 and the spot heater 12 which are constantly energized in the next main heating section MH are operated (step S8).

In step S8, the sheath heater 11 is heated as usual, and the subroutine S
The spot heater 12 is heated based on the temperature difference map M2 measured by 2.

After that, the substrate 20 is again fed at a fixed size (step S9), the substrate 20 is cooled by the cooling fan 13 (step S10), and the substrate is further fed at a fixed size (step S11) to the next step. move on.

[2] FIG. 8 shows an embodiment of the reflow furnace according to the present invention (Part 2), and the difference between this embodiment and the embodiment of the present invention (Part 1) (see FIG. 1) is Preheating section PH
CCD camera 14 and laser unit 15 in front of 1.
Without a measuring means consisting of the preheating part PH2 and the main heating part M
The point is that an infrared spectrometer 7 is provided between H and H, and an output signal of this infrared spectrometer is given to the CPU 33 via the control unit 32. Therefore, the embodiment shown in FIGS. 2 to 4 can be similarly applied to the embodiment shown in FIG.

FIG. 9 shows the CPU 3 in the present invention (part 2).
6 shows the control flow chart of FIG. 3, and in this embodiment, the same reference numerals as those in the flow chart of FIG. 6 indicate the same steps, and in the steps of FIG. 9, the subroutine S2 of FIG. S7 and S8
And a mounting subroutine S12 for measuring a mounted component by an infrared spectrometer is provided between and.

A concrete example of the measurement subroutine S12 is shown in FIG. 10. First, the temperature distribution after passing through the preheating section PH2 is measured by the infrared spectrometer 7 (step S121), and the measurement result is obtained. Temperature difference map M3
To create.

In this case, in order to create the temperature difference map M3, the reference temperature may be stored in advance and the reference temperature may be compared with the measured temperature distribution.

That is, in the infrared spectrometer 7, the infrared light 71 from the substrate 20 is received by the light receiving portion 72, and the temperature distribution of the substrate 20 can be measured by scanning the light receiving portion 72 at this time.

Then, the position of the scan information and the distribution temperature can be known by image-processing this, so that it can be obtained as shown by comparing the temperature difference of each component on the substrate with the reference temperature.

Since the temperature difference map M3 shows the temperature state by the volume of each mounted component detected by the infrared spectrometer 7, the CCD camera 14 and the laser unit 15 as shown in FIG. 1 are not necessary.

[0059]

As described above, in the reflow furnace according to the present invention, the size and position of each mounted component on the board is measured by providing the measuring means in the preceding stage of the preheating section, and the board is heated by the main heating. The spot heating unit provided in the main heating unit corresponding to the size and position of each mounting unit heats each mounted component in component units, or instead of providing the above measuring means, the preheating unit and the main heating unit. Infrared spectrometer is installed between and, and the size information and the position information of the same mounted parts are taken out by the temperature difference information obtained from this infrared spectrometer, and the mounting parts are heated by spot heating in the same manner. Therefore, even if large and small components are mixed in the substrate, optimum heating can be performed for each component and a desired temperature profile can be obtained, so that the substrate quality is also improved.

Further, parts (large parts) which could not be conventionally reflow soldered can be collectively reflow soldered, and the number of steps can be reduced.

[Brief description of drawings]

FIG. 1 is a side view and a plan view of a reflow furnace according to the present invention (No. 1).

FIG. 2 is a plan view of a heating unit used in the reflow furnace according to the present invention.

FIG. 3 is a perspective view of a main heating unit used in the reflow furnace according to the present invention.

FIG. 4 is a diagram showing an example of a spot heating unit used in the reflow furnace according to the present invention.

FIG. 5 is a block diagram showing a control system of the reflow furnace according to the present invention.

FIG. 6 is a control flowchart of the present invention (No. 1).

FIG. 7 is a flowchart specifically showing a subroutine for measuring mounted components by the CCD camera and the laser unit in FIG.

FIG. 8 is a side view showing an embodiment of a reflow furnace according to the present invention (No. 2).

FIG. 9 is a control flowchart of the reflow furnace according to the present invention (No. 2).

10 is a diagram specifically showing a subroutine for measuring mounted components by the infrared spectrometer shown in FIG.

FIG. 11 is a side view showing a conventionally known reflow furnace.

FIG. 12 is a waveform diagram showing a general temperature profile obtained by a reflow furnace.

FIG. 13 is a diagram for explaining a defect of the conventional example.

[Explanation of symbols]

 1 Reflow oven 2 Substrate transport conveyor 6 Substrate loading sensor 7 Infrared spectrometer 14 Laser unit 15 CCD camera PH1, PH2 Preheating part MH Main heating part 11 Season heater 12 Spot heater 20 Board 21 Mounting component 22 Paste Solder printing part The reference numerals indicate the same or corresponding parts.

Claims (5)

[Claims] 1. A reflow furnace for soldering the mounting component to the substrate by passing a substrate on which the mounting component is mounted on the paste solder printing unit through a preheating unit and a main heating unit by a feeding mechanism. Means for measuring the size and position of the mounted component provided in the preceding stage in a predetermined area unit, a spot heating section provided in the main heating section capable of heating in the predetermined area unit, and the substrate passing through the main heating section And a control means for controlling the spot heating section to heat the mounted component in accordance with the size and position obtained from the measuring means. 2. The volume is measured by the measuring means also measuring the height of the mounted component as the size,
The reflow furnace according to claim 1, wherein the control unit heats the spot heating unit in accordance with a heat capacity corresponding to the volume of the mounted component. 3. A reflow furnace for soldering the mounting component to the substrate by passing a substrate on which the mounting component is mounted on the paste solder printing unit through a preheating unit and a main heating unit by a feeding mechanism. An infrared spectrometer provided between the main heating unit and the preheating unit for measuring a temperature difference of the mounted component, a spot heating unit provided in the main heating unit and capable of heating the predetermined area unit, Means for extracting size information and position information of the mounted component from the temperature difference information obtained from the infrared spectrometer when the substrate passes through the main heating unit, and correspondingly heating the mounted component by the spot heating unit And a reflow furnace. 4. The reflow furnace according to claim 1, wherein a position of the heater of the spot heating section can be adjusted according to a board form of the mounted component. 5. The reflow furnace according to claim 1, wherein the feeding mechanism feeds the substrate by a fixed size when passing the substrate through the preheating unit and the main heating unit.