JP2003133718A - Reflow apparatus and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflow apparatus and a reflow method that can carry out reliable solder junction. SOLUTION: In the reflow apparatus for conveying a substrate 4 in a heating chamber 3 that is divided into a plurality of heating zones including a reflow zone, and at the same time allowing an electrode 6a for connection of an electronic component 6 mounted onto a surface at one side of the substrate 4 to be subjected to solder junction to an electrode 4a of the substrate 4 by cream solder 7, heaters H5B, H6B, H5A and H6A are provided in reflow zones Z5 and Z6. The heaters H5B and H6B heat the substrate 4 by radiant heat from the opposite side of an electronic component-mounting surface for fusing solder. The heaters H5A and H6A are used as an overheating-preventing means for spraying gas at temperature that is lower than a solder melt point temperature to the side of the electronic component-mounting surface of the substrate 4, to set the temperature of an electronic component 6 to a heat-resistant temperature or less. As a result, the solder is fused completely, and at the same time overheating in the electronic component 6 can be prevented even in lead-free solder with a high melting point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow device and a reflow method for heating a solder joint object.

[0002]

2. Description of the Related Art A reflow device is known as a device used when soldering an electronic component to an object to be soldered such as a substrate. The reflow apparatus is one in which an object is passed through a heating chamber in the reflow apparatus to sequentially raise the temperature of a solder joint portion, and is heated to a temperature equal to or higher than the solder melting point temperature to melt the solder and perform solder joining. In the heating chamber, generally, a heating zone for rapidly heating the temperature of the target object to raise the temperature, a soaking zone for uniformizing the temperature of each part of the target object, and a solder joint by raising the temperature of the soldered portion to a temperature higher than the melting point. It has a reflow zone for melting.

[0003]

From the viewpoint of preventing environmental pollution by lead in recent years, a lead-free type solder containing no lead as a component is used in place of the conventionally used tin-lead eutectic solder. It has become. However, since the melting point of this lead-free solder is higher than that of the conventional solder, it is difficult to secure a temperature margin with the heat resistant temperature of the electronic component. Therefore, if the heating temperature is set to be high, the electronic components are likely to be damaged by overheating, and if the heating temperature is set to be low, there is a problem that solder melting is insufficient and a bonding failure is likely to occur.

Therefore, an object of the present invention is to provide a reflow apparatus and a reflow method capable of performing solder joining with excellent reliability.

[0005]

According to another aspect of the present invention, there is provided an electronic component mounted on one surface of a substrate while the substrate is transported in a heating chamber defined by a plurality of heating zones including a reflow zone. Is a reflow device for solder-bonding the connection electrode to the electrode of the board, wherein the solder is melted by heating the board with radiant heat from the opposite side of the electronic component mounting surface to the reflow zone for melting the solder for bonding. A heating means and an overheat preventing means for controlling the temperature of the electronic component to a heat resistant temperature or lower by blowing a gas having a temperature lower than the melting point of the solder to the electronic component mounting surface side of the substrate are provided.

The reflow apparatus according to claim 2 is the reflow apparatus according to claim 1.
In the reflow device described above, the solder is a lead-free type solder.

A reflow method according to a third aspect of the present invention is a reflow method of soldering a connecting electrode of an electronic component mounted on one surface of a substrate to an electrode of the substrate, wherein the substrate is mounted on the electronic component mounting surface. While melting the solder on the electronic component mounting surface side by heating with radiant heat from the opposite side, the temperature of the electronic component soldered by blowing a gas having a temperature lower than the melting point temperature of the solder onto the electronic component mounting surface side of the substrate. Is prevented from exceeding the heat resistant temperature.

The reflow method according to claim 4 is the reflow method according to claim 3.
The reflow method as described above, wherein the solder is lead-free solder.

According to the present invention, in the reflow zone for melting the solder for joining, the substrate is heated by radiant heat from the side opposite to the electronic component mounting surface to melt the solder on the electronic component mounting surface side, By blowing a gas at a temperature lower than the melting point of the solder onto the component mounting surface side to prevent the temperature of the electronic components to be soldered from exceeding the heat resistant temperature, the solder is completely melted and the electronic components are not overheated. Can be prevented.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. 1 is a side sectional view of a reflow apparatus according to an embodiment of the present invention, and FIG. 2A is a sectional view of a reflow zone of a reflow apparatus according to an embodiment of the present invention.
FIG. 3B is a cross-sectional view of a substrate solder-bonded by the reflow device according to the embodiment of the present invention, and FIG. 3 is an explanatory diagram of a heating temperature and a heating profile in the reflow method according to the embodiment of the present invention.

First, the structure of the reflow apparatus will be described with reference to FIG. In FIG. 1, the reflow apparatus 1 includes a heating chamber 3 horizontally arranged inside a furnace body 2, and the heating chamber 3 includes seven zones Z1, Z2, Z3, Z4, Z5.
It is divided into Z6 and Z7. Zones Z1 and Z2 are heating zones for rapidly heating the substrate 4 which is the object of solder joining to raise the temperature. The zones Z3 and Z4 are the substrate 4
Is a soaking zone in which the temperature of each part is made uniform to a predetermined preheating temperature. The zones Z5 and Z6 are the substrate 4
It is a reflow zone that heats the solder joint part of the above to a temperature exceeding the solder melting temperature to perform the solder joint.
A cooling zone 7 cools the substrate 4 after solder bonding.

An inlet 3a for loading the substrate 4 is provided on the upstream side wall (left side in FIG. 1) of the heating chamber 3, and an outlet 3b for loading the substrate 4 is provided on the downstream side wall. It is provided. A transport conveyor 5 is arranged between the carry-in port 3a and the carry-out port 3b so as to penetrate the zones Z1 to Z7. The substrate 4 carried into the heating chamber 3 from the carry-in port 3a by the carrying conveyor 5 sequentially passes through each zone and is carried out to the outside from the carry-out port 3b.

Here, the heating means provided in each zone in the heating chamber 3 will be described. The reflow device 1 shown in the present embodiment is provided with different types of heating means depending on the purpose of each zone. In the zone Z1, a hot-air type heating device H1A combining a heater and a blowing fan is arranged above the transport conveyor 5, and a far infrared heating device H1B is disposed below the transport conveyor 5. Heating device H
1A heats the board 4 and the electronic components mounted on the top surface of the board 4 by blowing hot air onto the top surface of the board 4. The heating device H1B irradiates the lower surface of the substrate 4 with far infrared rays and heats the substrate 4 by radiant heat.

In the zones Z1, Z2, Z3 and Z4, hot air type heating devices are provided on both upper and lower sides of the conveyor 5. That is, the heating devices H2A and H2B are provided in the zone Z2, and the heating device H3 is provided in the zone Z3.
A, H3B, in the zone Z4, heating devices H4A, H4
B are provided respectively. Zones Z1, Z2, Z
In Z3 and Z4, hot air is blown onto the upper and lower surfaces of the substrate 4 to heat the substrate 4 to a predetermined preheating temperature.

In the zones Z5 and Z6, hot air type heating devices H5A and H6A are provided above the transfer conveyor 5, and far infrared type heating devices H5B and H6B are provided below the transfer conveyor 5, respectively. There is. Zone Z5 (Z
In 6), as shown in FIG. 2A, the lower surface side of the substrate 4 placed on the conveyor 5 is heated by the heating device H5B (H6).
While being heated by radiant heat of far infrared rays emitted from B) (see broken line arrow a), hot air of a predetermined temperature blown from the heating device H5A (H6A) is blown onto the upper surface of the substrate 4 (see solid line arrow b). ). Then, in the zone Z7, both upper and lower blowers F7A and F7 for cooling are provided.
7B is provided.

Here, the substrate 4 to be soldered by the reflow device 1 is a single-sided mounting substrate, and the electronic component 6 is mounted only on one surface (upper surface). As shown in FIG. 2B, an electrode 4 on which an electronic component is mounted is mounted on the upper surface of the substrate 4.
a is formed, and the cream solder 7 is printed on the electrode 4a in the solder printing step of the previous step. Further, in the component mounting step, the electronic component 6 is mounted on the upper surface side of the substrate 4, and the connection electrode 6a of the electronic component 6 lands on the electrode 4a after solder printing.

Here, the solder particles in the cream solder 7 used for solder joining contain lead-free solder (eg, Sn-A) containing no or almost no lead component.
g-Cu system etc.) is used. The melting temperature of such a lead-free solder is significantly higher than the melting temperature of the tin-lead eutectic solder that has been conventionally used, 210 to 220 ° C.
Since it is only about 6 degrees, electronic parts 6
There is a constraint that a small temperature difference (temperature margin) from the heat resistant temperature (about 240 ° C.) can be secured.

Under such restrictions, in order to perform good solder joining without causing thermal damage to the electronic component 6, in the present embodiment, the heating temperature and heating profile for each zone as shown in FIG. I am trying to reflow. FIG. 3A shows an example of the heating temperature of each zone (set temperature of the heating device), and FIG. 3B is a heating profile showing the temperature in each zone of the solder joint on the upper surface side of the substrate 4. is there.

First, the temperature setting in the heat raising zone (Z1, Z2) and the soaking zone (Z3, Z4) will be described.
Among the heating devices arranged in these zones, the heating devices H1A, H2A, H3A, H4A, H2B by hot air,
H3B and H4B are all 180 according to the preheating temperature T1.
Set to ° C. The heating device H1B arranged in the zone Z1 is set to 300 ° C. for the purpose of rapidly raising the temperature of the substrate 4 from the lower surface side. With such a temperature setting, as shown in FIG. 2B, the substrate 4 carried into the heating chamber 3 rapidly rises in temperature in the heat-up zone, and each part of the substrate 4 is separated by passing through the temperature-equalizing zone. Preheat temperature T
Heated uniformly to 1.

Next, the temperature setting in the reflow zones (Z5, Z6) for melting the bonding cream solder 7 will be described. Here, far infrared rays are emitted to the lower surface side of the substrate 4 by the heating devices H5B and H6B, and at this time, the set temperature of the heating devices H5B and H6B is set to 400 ° C. The radiant heat of the far infrared rays raises the temperature of the lower surface of the substrate 4, and this heat causes the heat of the inside of the substrate 4 to increase the temperature of the upper surface of the substrate 4. As shown in FIG.
In, the temperature on the upper surface side of the substrate 4 rises to a temperature exceeding the melting point temperature T3.

As a result, the solder component in the cream solder 7 interposed between the electrode 4a of the substrate 4 and the joining electrode 6a of the electronic component 6 is melted, and the connecting electrode 6a is soldered and joined to the electrode 4a. Therefore, the heating devices H5B and H6B are heating means for melting the solder by heating the substrate 4 from the side opposite to the electronic component mounting surface (upper surface) with radiant heat generated by irradiation of far infrared rays. The heating devices H5B, H6
As B, a heating method other than the radiant heat (for example, a hot air blowing method) may be used in combination, and any material capable of melting the cream solder on the upper surface of the substrate 4 may be used.

In the reflow zone, the heating devices H5B and H6B perform heating, and the upper heating devices H5A and H6A adjust the temperature of the upper surface of the substrate 4. That is, in the heating devices H5A and H6A, the heating temperature is set to 210 ° C. and 200 ° C., which are lower than the heat resistant temperature T3 (about 240 ° C.) of the electronic component 6, respectively.
Hot air of these set temperatures is blown onto the upper surface of the.

As a result, the temperature of the electronic component 6 does not greatly exceed these set temperatures, and the heat resistant temperature T3 is always maintained.
Maintained at a lower temperature. Therefore, the heating device H5
A and H6A are overheat preventing means for keeping the temperature of the electronic component 6 below the heat resistant temperature by blowing a gas having a temperature lower than the melting point temperature of the solder onto the electronic component mounting surface side of the substrate 4.

After that, the substrate 4 is moved to the cooling zone, where cool air at about room temperature is blown from both upper and lower surfaces of the substrate 4 by the blowers F7A and F7B to cool the substrate 4. As a result, the solder melted in the reflow zone is cooled and solidified, and the solder joining is completed.

As described above, in the reflow apparatus according to the present embodiment, in the reflow zone, the board 4 is heated by radiant heat from the side opposite to the electronic component mounting surface to melt the solder on the electronic component mounting surface side. A gas having a temperature lower than the melting point temperature of the solder is blown to the electronic component mounting surface side to prevent the temperature of the electronic component 6 from exceeding the heat resistant temperature. As a result, it is possible to efficiently raise the temperature of the substrate 4 and prevent overheating of the electronic component 6 itself having a low heat resistant temperature. Therefore, even when using a high melting point lead-free solder, Solder bonding with excellent reliability can be performed without causing damage due to overheating of electronic components.

[0026]

According to the present invention, in the reflow zone for melting the solder for joining, the substrate is heated by radiant heat from the side opposite to the electronic component mounting surface to melt the solder on the electronic component mounting surface side and When a lead-free solder is used, the temperature of the electronic component to be soldered is prevented from exceeding the heat resistant temperature by blowing a gas at a temperature lower than the melting point of the solder onto the electronic component mounting surface of Even in this case, it is possible to completely melt the solder, prevent overheating of the electronic component, and realize highly reliable solder joining.

[Brief description of drawings]

FIG. 1 is a side sectional view of a reflow device according to an embodiment of the present invention.

FIG. 2A is a cross-sectional view of a reflow zone of a reflow device according to an embodiment of the present invention. FIG. 2B is a cross-sectional view of a substrate solder-bonded by the reflow device according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a heating temperature and a heating profile in the reflow method according to the embodiment of the present invention.

[Explanation of symbols]

1 reflow equipment 3 heating chambers 4 substrates 4a electrode 6 electronic components 6a Connection electrode 7 cream solder H5A, H6A heating device (hot air type) H5B, H6B heating device (far infrared type)

Claims (4)

[Claims] 1. A reflow process in which a connection electrode of an electronic component mounted on one surface of a substrate is soldered to an electrode of the substrate while the substrate is conveyed in a heating chamber defined by a plurality of heating zones including a reflow zone. A device, in a reflow zone for melting solder for joining, heating means for melting the solder by heating the substrate with radiant heat from the side opposite to the electronic component mounting surface, and the electronic component mounting surface side of the substrate A reflow apparatus comprising: an overheat prevention unit for reducing a temperature of an electronic component to a heat resistant temperature or lower by blowing a gas having a temperature lower than a solder melting point temperature. 2. The reflow apparatus according to claim 1, wherein the solder is a lead-free type solder. 3. A reflow method for soldering a connecting electrode of an electronic component mounted on one surface of a substrate to an electrode of the substrate, wherein the substrate is heated from the side opposite to the electronic component mounting surface by radiant heat. As a result, the solder on the electronic component mounting surface side is melted, and the temperature of the electronic component to be soldered by blowing a gas having a temperature lower than the melting point temperature of the solder onto the electronic component mounting surface side of the substrate becomes equal to or higher than the heat resistant temperature. A reflow method characterized by preventing 4. The reflow method according to claim 3, wherein the solder is a lead-free type solder.