JP2022187673A - Manufacturing method of print circuit board - Google Patents

Abstract

To provide a manufacturing method of a print circuit board which can adjust the amount of flux depending on a joint.SOLUTION: A manufacturing method of a print circuit board to which an electrical component is bonded according to the present invention includes a component insertion step of inserting a terminal of an electrical component into a through-hole of the printed wiring board, and a soldering step of joining the through-hole and the electrical component. At least one of the through-holes has melted and solidified solder on its land, and the soldering step melts the solder on the land and supplies thread solder to join the through-hole and the electrical component to adjust the amount of flux according to the wettability of a joint.SELECTED DRAWING: Figure 2

Description

The present invention relates to a method of manufacturing a printed circuit board, and more particularly to a method of manufacturing a printed circuit board capable of joining electrical components that cannot be reflow soldered.

Soldering to mount electrical components on a printed circuit board with no components on it is generally performed by reflow soldering (hereinafter sometimes referred to as "reflow"), followed by flow soldering (hereinafter referred to as "reflow"). It is sometimes called "flow soldering".) and electrical parts that cannot be reflow soldered by hand are often mounted.

The above reflow is a soldering method in which cream solder is applied to the terminal part of the board surface, electrical components are placed on it, and the cream solder is melted in a high-temperature furnace to join multiple electrical components to the printed circuit board at once. is.

In addition, the above flow is a process of mounting electrical components that are not compatible with reflow, which cannot be put into a high-temperature furnace due to their low heat resistance. (hereinafter sometimes referred to as "through-holes"), and the individual terminals of the electrical components are soldered using thread solder.

In Patent Document 1, a terminal of an electric component is inserted into a through-hole of a printed circuit board, the through-hole is plugged with cream solder, and a laser beam is applied to the through-hole, and soldering is performed by supplying thread solder. disclosed.

JP 2010-10589 A

The amount of oxide film formed on the surface of the junction where the through-hole of the printed circuit board and the terminal of the electrical component are joined, that is, the wettability to solder, differs depending on the material and shape of the junction.

If more flux than is required to reduce the oxide film formed on the joint is applied, the surplus flux that is not consumed in the reduction of the oxide film will scatter and the quality of the printed circuit board will be degraded. do.

Therefore, it is desirable to adjust the amount of flux for each joint according to the wettability of the joint with solder.

However, in order to adjust the amount of flux for each joint, it is necessary to use thread solder with a different flux content for each joint, which complicates the soldering process.

Patent Document 1 discloses changing the flux content of cream solder and thread solder, but in order to prevent the laser beam from irradiating the electrical parts, it is necessary to block the through holes with cream solder. For this reason, cream solder must be applied even to joints with good wettability, and it is difficult to prevent flux from scattering.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a method of manufacturing a printed circuit board that can adjust the amount of flux depending on the joint.

As a result of intensive studies in order to achieve the above object, the present inventors used a printed circuit board having flux-removed solder attached to the joints, and supplied wire solder to this printed circuit board to join electrical components. By doing so, it is possible to reduce the amount of thread solder to be used while ensuring the amount of solder required for joining, and to prevent the scattering of flux, which led to the completion of the present invention.

That is, the method of manufacturing a printed circuit board to which electrical components are joined according to the present invention comprises a component insertion step of inserting terminals of electrical components into through holes of a printed wiring board, and a soldering step of joining the through holes and electrical components. And prepare.
At least one of the through holes has melted and solidified solder on its land, and the soldering step melts the solder on the land and supplies thread solder to form the through hole. It is characterized by including a process of joining electrical components.

According to the present invention, the solder from which the flux has been removed from the printed circuit board is melted, and the thread solder is supplied to join the through-hole and the electric component. Therefore, it is possible to provide a method of manufacturing a printed circuit board in which the amount of flux can be adjusted.

It is a figure explaining a component insertion process. It is a figure explaining a soldering process process. It is a figure which shows the completion state of joining by solder. It is a figure explaining the state which applied cream solder.

A method for manufacturing a printed circuit board to which electrical components are joined according to the present invention will be described in detail.
The printed circuit board manufacturing method includes a component insertion step and a soldering step.

The component insertion step is, as shown in FIG. 1, a step of inserting terminals of electrical components into through-holes of a printed circuit board. (sometimes referred to as "land") is pre-applied with solder.
This solder is once melted and solidified to adhere to the land, and the flux is vaporized and removed by the melting.

The soldering step is, as shown in FIG. 2, a step of joining the terminals of the electrical component in the through-hole and the through-hole.

In the present invention, as described above, since the solder from which the flux has been removed adheres to the land, the solder on the land is melted and the wire solder is supplied to solder the electric parts.

Therefore, the amount of thread solder used is reduced compared to the case of joining only with thread solder, so flux is not left over for reduction of joints such as through holes and terminals, so flux scattering is prevented. prevented.

In addition, unlike cream solder, the solder adhered to the joint is not wrapped in flux, so the heat of the soldering iron is directly transferred to the solder and melts quickly, so the cycle time is not extended.

The printed board to which the solder is applied may be a printed board on which no components are mounted, that is, a so-called raw board, or a printed board on which electrical components are surface-mounted by reflow.

If the electrical component is a surface-mounted printed circuit board, when soldering this electrical component, cream solder is applied not only to the lands that join the electrical component, but also to the lands that solder the non-reflow-compatible electrical component. can be given.

Therefore, within a series of manufacturing processes in which cream solder is melted in a high-temperature furnace and solidified to join electrical components, solder can also be applied to lands that join electrical components that are not compatible with reflow, without adding a new process. can be applied, the cycle time is not extended.

In addition, since it is not necessary to newly provide a coating device for applying solder to the through-holes for joining the electrical parts that are not compatible with reflow, the manufacturing cost does not increase.

The method for producing a printed circuit board according to the present invention can optionally have a step of producing a printed circuit board to which the solder is applied.

As shown in FIG. 3, when the through-hole and the electrical component are joined by solder, the solder must pass through the through-hole and be continuous on the front side and the back side of the printed circuit board.

Therefore, in reflow, a heaping amount of cream solder is applied not only on the land but also on the through hole so that the solder is sufficiently supplied into the through hole.

However, if the through-holes are covered with cream solder, when the cream solder melts, it enters the through-holes and solidifies to block the through-holes, making it impossible to insert the terminals of electrical components. As shown in 4, cream solder is applied only on the land without blocking the through hole.

The amount of cream solder to be applied to the land is preferably changed according to the wettability of the through-holes of the joints and the terminals of the electrical parts to the solder wire.

Specifically, by applying more cream solder to joints with good wettability with thread solder and reducing the amount of cream solder applied to joints with poor wettability, the amount of thread solder used for joining is changed, the amount of flux delivered to the joint can be adjusted.

It is not necessary to apply the cream solder to all the through holes, and it is not necessary to apply the cream solder to the through holes with the poorest wettability.

By using a thread solder with a large amount of flux that matches the joint with the worst wettability, it is possible to supply an appropriate flux to each joint with different wettability to the thread solder. , good solder joints and flux splatter can be prevented.

The wettability of the joint to solder can be known from the material and shape of the terminal, but it can also be known by fabricating a printed circuit board and inspecting for defective joints.

The cream solder can be applied using a conventionally known coating device or printing device, and the amount of cream solder to be applied can be adjusted by the mask area or the like.

REFERENCE SIGNS LIST 1 printed circuit board 11 through hole 12 land 2 electrical component 21 terminal 3 solder solidified after melting 4 thread solder 41 thread solder feeder 5 cream solder 6 soldering iron

Claims (3)

A method for manufacturing a printed circuit board to which electrical components are bonded,
a component insertion step of inserting terminals of electrical components into through-holes of a printed wiring board;
a soldering step of joining the through-hole and the electrical component,
at least one of the through holes having molten and solidified solder on its land;
The method of manufacturing a printed circuit board, wherein the soldering step includes a process of melting the solder on the land and supplying thread solder to join the through hole and the electrical component. Before the component insertion process,
A soldering step of applying cream solder to the land of the through hole;
and a reflow step of melting the cream solder in a furnace,
2. The method of manufacturing a printed circuit board according to claim 1, wherein said solder application step includes a process of applying cream solder onto lands without blocking said through holes. The amount of cream solder applied to the land of the through hole is
3. The method of manufacturing a printed circuit board according to claim 2, wherein the wettability of the through-hole and/or the wettability of the terminal of the electrical component joined to the through-hole with respect to the solder wire is different.

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