JPH057077A - Soldering method - Google Patents

Abstract

PURPOSE:To provide the title soldering method of a discrete part capable of eliminating the soldering step by a robot or manual operations while cutting down the cost by the enhancement of the reliability upon the soldering step, the curtailment of the manhours for and the increase in the efficiency of the soldering step. CONSTITUTION:During the title soldering method wherein a discrete part 2 is packaged on a printed-substrate 1 with the surface lands 5 and the rear surface lands 6 formed thereon, before or after the discrete part 2 is inserted into the printed-substrate 1, the surface lands 5 are coated with a creamy solder and then the printed-substrate 1 is passed over a solder immersion vessel 9 so that the rear surface lands 6 and the discrete part 2 may be soldered with one another. Through these procedures, the heat of molten solder in the solder immersion vessel 9 can be conducted from the discrete part 2 to the creamy solder on the surface lands 5 so as to set the creamy solder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for soldering a discrete component to front and back lands when mounting an electronic component on a printed circuit board.

[0002]

2. Description of the Related Art Conventionally, electronic parts, in particular insertion type so-called discrete parts, are inserted into a printed circuit board,
When soldering to the back side land, first, pass the printed circuit board with discrete components inserted through the solder dipping bath to solder to the back side land, then use the automatic soldering robot or manual work to make the front side land. And soldering discrete parts.

Further, through-hole processing is employed in which front and back lands of a printed circuit board are artificially soldered before inserting discrete components.

[0004]

By the way, in both of the above-mentioned conventional methods, oxidation due to the flux of the soldering iron tip is unavoidable, the reliability of soldering is lacking, and the connecting portion of the discrete component is For soldering individually,
There is a problem that the soldering work requires a considerable amount of time, the work efficiency is low, and it is one of the factors of cost increase.

The present invention has been made in view of the above problems, and an object thereof is to eliminate soldering by a robot or manual work, improve reliability of soldering, and soldering work time. It is an object of the present invention to provide a soldering method for discrete components, which can reduce the cost and cost by improving the efficiency.

[0006]

In order to achieve the above object, the present invention takes the following technical means. That is, the method of the present invention is a method for mounting and soldering discrete components on a printed circuit board on which front lands and back lands are formed, and applying cream solder to the front lands before or after the discrete components are inserted. Then, by passing the printed circuit board over the solder immersion tank and soldering the back surface land and the discrete component, the heat of the molten solder in the solder immersion tank is transferred from the discrete component to the cream solder on the front surface land, and the cream solder Is characterized by solidifying and soldering the discrete component to the surface land.

According to the present invention, the front surface land and the back surface land made of copper foil are provided at predetermined positions on the front and back surfaces of the printed circuit board, the discrete component insertion holes are provided, and the cream solder is applied on the front surface land (screen. After printing or coating with a dispenser), the lead wire of the discrete component is inserted into the insertion hole of the printed circuit board. Next, the printed circuit board is passed through a solder dipping tank, the back surface land and the lead wire are dipped in the molten solder to be soldered, and the heat of the molten solder is transmitted through the lead wire to the cream solder on the front surface land. Then, the cream solder is solidified and the surface land and the lead wire of the discrete component are soldered. In this way, by passing the back surface land and the front surface land over the solder dipping tank, they are automatically soldered to the lead wires of the discrete component at the same time.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. The drawing shows a discrete component 1 on a printed circuit board 1.
A mounting step (for example, a capacitor, a resistor, a coil, etc.) is shown. As shown in FIG. 1, first, a lead wire insertion hole 4 for inserting the lead wire 3 of the discrete component 2 is formed at a predetermined position of the printed board 1. ..

Then, as shown in FIG. 2, front surface lands 5 and back surface lands 6 made of copper foil around the lead wire insertion holes 4 are fixed at predetermined positions on the front and back of the printed circuit board 1, and then, as shown in FIG. As shown in FIG. 3, cream solder 7 is applied to the upper surface of the front surface land 5. The cream solder 7 is applied by screen printing or application with a dispenser.

Therefore, as shown in FIG. 4, when the back surface land 3 of the discrete component 2 is inserted from the front side, the lower end 3a of the lead wire 3 is bent to prevent it from collapsing. In this way, as shown in FIG. 5, the printed circuit board 1 on which the discrete component 2 is mounted is placed on a conveyor (not shown), and the molten solder 8 is placed on the front side with the front side facing upward. It is made to pass over the solder dipping bath, that is, the solder dipping bath 9 being blown up, and while passing over the bath 9, the molten solder 8 adheres to the back surface land 6 of the printed circuit board 1, especially around the lower end 3a of the lead wire. At this time, the heat of the molten solder 8 is transferred to the cream solder 7 on the front surface land 5 through the lead wire 3, and the cream solder 7 is hardened. Then, when the printed circuit board 1 passes through the solder dipping bath 9, the solders 7a and 8a are cooled and solidified, and the front surface land 5 and the back surface land 6 and the lead wire 3 are simultaneously and efficiently soldered and connected. The state shown in FIG.

The lead wire 3 can be made of a material that can obtain sufficient strength and heat conduction, for example, a steel wire, a copper wire, a solder-plated iron wire or the like, and a wire diameter of about 0.6 mm is preferable.

Further, it goes without saying that the cream solder 7 may be applied after the discrete component 2 is inserted into the printed board 1.

[0013]

As described above, the soldering method for discrete components according to the present invention is a molten solder for soldering the rear surface land, which is transmitted through the lead wire with the cream solder applied on the front surface land. Since it is characterized by being cured by the heat of, the front and back surface lands and discrete parts can be soldered simultaneously and automatically, and there is no need for conventional through hole processing or robot or manual soldering. Therefore, it is possible to shorten the soldering work time, improve the reliability, and significantly reduce the cost and improve the quality by completely automating the soldering work time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a printed circuit board.

FIG. 2 is a cross-sectional view of a printed circuit board including a front surface land and a back surface land.

FIG. 3 is a cross-sectional view of a printed circuit board including cream solder.

FIG. 4 is a sectional view of a printed circuit board on which discrete components are mounted.

FIG. 5 is a sectional view showing a state of immersion in a solder immersion tank.

FIG. 6 is a sectional view of the finished product.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed circuit board 2 Discrete parts 3 Lead wire 5 Front surface land 6 Back surface land 7 Cream solder 8 Molten solder 9 Solder dipping bath

Claims (1)

Claim: What is claimed is: 1. A method for mounting discrete components on a printed circuit board having front and back lands formed thereon and soldering the printed components, wherein the cream is before or after the discrete components are inserted into the front lands. Transfers the heat of the molten solder in the solder immersion tank from the discrete parts to the cream solder on the front side land by applying solder and passing the printed circuit board over the solder immersion tank to solder the back side land and discrete parts. Then, the discrete solder is soldered to the surface land by solidifying the cream solder.