JPS6229196A - Reflow soldering method and apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and apparatus for reflow soldering electronic components onto a printed circuit board.

[Background of the invention]

Conventionally, electronic components have been soldered to printed circuit boards using a flow soldering method. However, with the miniaturization of products, higher density printed circuit boards are required, and surface mount components such as flat back ICs and chip components are increasingly used. A reflow soldering method is used in which solder is melted using a suitable heat source such as Joule heat, infrared rays, laser, gas, or the latent heat of vaporization of a special liquid.

This is a reflow soldering method that uses high-temperature gas.

For example, as shown in Japanese Patent Application Laid-Open No. 56-66374, there is a method in which an inert gas such as Alzan is heated and sprayed onto the soldering part for soldering, and Japanese Patent Application Laid-Open No. 59-113689
As shown in Japanese Patent Application Publication No. 2003-120012, there are known methods in which air is heated to a high temperature and then blown onto the soldered parts.

In this soldering method, as shown in FIG. 1, a solder layer 3 is formed on a land 2 of a printed circuit board 1, and an electronic component 4 is
After positioning the lead terminals 5 and mounting all of the electronic components 4, hot air 7 generated by a hot air generator 6 is blown to melt the solder layer 3 and connect. Here, as a method for forming the solder layer 3, a method of screen printing cream solder is generally used. In order to obtain a good connection, the amount of solder layer 3 is important; if it is too large, it will result in a solder bridge between the lead terminals, and if it is too small, it will result in a solder open connection failure.

In recent years, the lead terminal pitch of flat nose ICs has become rapidly narrower, and at the same time, the lead terminals have also become thinner, making it difficult to maintain the shape accuracy of the lead terminals. If each lead terminal has a different shape, the amount of gap between the lead terminal and the land changes, resulting in a different optimum amount of solder for each lead terminal, making it impossible to avoid defects such as solder bridges and solder opens.

This will be explained with reference to FIGS. 2 and 3. Second
As shown in Figure (a), when the pitch of the lead terminals 5 is narrowed to, for example, 0.65 mm, the incidence of solder bridges increases. Furthermore, as shown in FIG. 2(b), if the shape of the lead terminal 5 is distorted, the amount of gap between the lead terminal 5 and the land changes, so the optimum amount of solder will differ for each lead terminal 5. become. When such a flat nose IC (electronic component) 4 is connected using the conventional reflow soldering method shown in FIG. 1, solder bridges 8 occur in areas where there is excess solder, as shown in FIG. Solder open 9 occurs in the insufficient portion.

By the way, with conventional equipment, it is difficult to supply the appropriate amount of solder to each lead terminal,
Since the occurrence of defects such as solder opens cannot be avoided, conventional repairs have been done manually.

[Purpose of the invention]

An object of the present invention is to provide a reflow soldering method and apparatus that can automatically make high-quality solder connections.

[Summary of the invention]

According to one embodiment of the present invention, an excessive solder layer is formed at the joint portion on the printed circuit board, and after positioning and mounting the electronic component,
The solder layer is melted with hot air, and then the solder bridges are removed by suction with a suction nozzle. 3) [Embodiments of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to FIG. 4. 7
In the 0-head, a nozzle body 11 is fixed to the lower end of a hot air generator 10. The nozzle body 11 includes a hot air tank 13 formed at an outlet for hot air 12 of a hot air generator 10, and hot air nozzles 14 formed on four sides of the lower end of this hot air tank 13.
and a suction nozzle 15 formed outward from the lower end of the hot air nozzle 14, and the suction nozzle 15 is connected to a negative pressure tank and a cooling tank (not shown).

Next, the effect will be explained. First, the solder layer 3 is formed on the printed circuit board l by, for example, screen printing. In this case, the solder layer 3 is formed in excess so that the portion where the lead terminal 5 and the land 20 are wide apart does not become exposed to open solder. Next, the lead terminal 5 of the electronic component 4 is accurately mounted at a predetermined position by an automatic mounting machine or an operator using a microscope or the like. Thereafter, the printed circuit board 1 and the reflow head are moved relative to each other, and the head 70 is positioned as shown. Next, the hot air 12 generated by the hot air generator]0 is sent. As a result, the hot air 12 flows evenly from the hot air nozzles 14 on the four sides via the hot air tank 13, melting the solder R43.

In this case, excessive molten solder causes solder bridges. However, solder opens do not occur due to excessive solder.

Next, to remove the solder bridge, use suction nozzle 1
5, the area near the lead terminal 5 suddenly becomes negative and positive. As a result, the center portion of the solder bridge is separated by the pressure of the air inflow 16 from the back surface of the electronic component 4, and the solder bridge is removed. On this occasion.

Since cold air flows in from the outside, the solder is temporarily cooled, and if icicles or the like occur, the solder may be heated again with hot air 12 to adjust the shape 2. A convenient way to rapidly create a negative pressure is to prepare a negative pressure tank and instantly open it with a valve.

Further, since there is a risk that the electronic component 4 may be displaced due to the pressure difference when removing the bridge, a pressure bottle 17 for pressurizing the electronic component 4 is provided at the center of the lower surface of the nozzle body 11 as a function of fixing the electronic component 4. A suction pad may be provided in place of this pressure pin 17.

After that, the hot air 12 is stopped and the cold air is sucked into the nozzle 15.
The molten solder is blown out and the molten solder is cooled to complete the soldering.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the solder layer is made excessive, the occurrence of solder open is prevented, and the solder bridges that occur as damage are removed by suction with a suction nozzle, so that high quality solder can be obtained. Connection can be made automatically.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional reflow soldering method, and FIGS. 2(a) and (b) are perspective views showing an example of an electronic component, respectively.
FIG. 3 is a perspective view showing some examples of soldering by the method shown in FIG.
FIG. 4 is a cross-sectional view showing the reflow soldering method and apparatus according to the present invention. 1... Printed circuit board, 2... Land,
3...Solder layer, 4...Electronic component, 5
...Lead terminal, 10...Hot air generator, 11
... Nozzle body, 12 ... Hot air, 14 ... Hot air nozzle, 15 ... Suction nozzle. 0″iA”! −1= , J゛ J“
1 ''' Figure 1 Figure 2 (0) (b) @ Figure 3 Figure 4

Claims (1)

[Claims] 1. Forming an excessive solder layer on the joint portion on a printed circuit board, then positioning and mounting an electronic component on the solder layer, and then melting the solder layer with hot air from a hot air nozzle; A reflow soldering method characterized in that solder bridges generated due to melting of the solder layer are then removed by suction with a suction nozzle. 2. In a reflow soldering device that forms a solder layer on a joint on a printed circuit board, positions and mounts an electronic component on this solder layer, and melts the solder layer by blowing hot air with a hot air generator, the hot air generation is performed. A reflow soldering device characterized in that a nozzle body is provided at the lower end of the device, and the nozzle body is formed with a hot air nozzle that blows out hot air and a suction nozzle that sucks in solder bridges generated by melting a solder layer.