JPH0123959B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention performs simple and reliable soldering on the surface of a circuit wiring pattern conductor of a flexible circuit board while maintaining a fluid state with a heating heater and adjusting the amount of solder attached to the surface. The present invention relates to a method and an apparatus thereof.

Known methods for soldering the circuit wiring pattern conductor surface of a flexible circuit board include a plating method and a method using a solder coater or solder printer used for existing rigid printed circuit boards.

When soldering the conductor surface with plating, as shown in Figure 1, the processing process is long, the processing time is long, and equipment such as water supply and drainage treatment equipment is required. It is inappropriate as a method. In particular, with regard to the electrolytic plating method, the circuit wiring pattern conductor to be soldered must be electrically conductive during plating. For this reason, electrolytic plating cannot be used as a soldering method for circuit wiring patterns in which conductivity cannot be established.

Next, a well-known method using a solder coater used on rigid printed circuit boards is shown in FIG. For hard printed circuit boards, in the case of a solder coater, after applying flux, a hard printed circuit board 1 of standard size is immersed vertically into a molten solder bath 2, and when the hard printed circuit board 1 is vertically pulled up from the molten solder bath 2. By blowing air heated above the melting point of the solder at high speed from the nozzle 3, excess solder adhering to the circuit wiring pattern is blown away and the thickness of the solder layer is adjusted. However, when using a solder coater to solder the surface of the circuit wiring pattern conductor of a flexible circuit board, the flexible circuit board is
A protective jig is required to prevent the flexible circuit board from being deformed or damaged due to the vertical immersion in the flexible circuit board and the influence of the heated air blown out from the nozzle at high speed. Therefore, when using an existing solder coater device for a flexible circuit board, it is necessary to attach and detach the device to a jig. Furthermore, since this is basically a soldering device for fixed-sized rigid printed circuit boards, it has the disadvantage that it cannot solder long cable-shaped flexible circuit boards.

Here, FIG. 3 shows a method of using a solder printer used for rigid printed circuit boards for flexible circuit boards. In a solder printer,
By horizontally inserting the flexible circuit board 4 with the circuit wiring pattern facing down between the rotating rolls 5 and 6 arranged vertically facing each other, the flexible circuit board 4 after applying flux is removed from the molten solder tank 7 by the metal lower roll 5. In this method, the molten solder that has adhered and lifted is transferred or printed onto the circuit wiring pattern conductor portion on the lower surface of the flexible circuit board 4. According to this method, the drawback of using a solder coater for soldering flexible circuit boards, which is that long cable-shaped flexible circuit boards cannot be soldered, can be solved, but the circuit wiring of flexible circuit boards can be solved. In addition to the fact that it is very difficult to apply an appropriate amount of solder to the surface of the lower metal roll from the molten solder tank and lift it up in order to transfer it to the pattern conductor, the flexible circuit board 4 and the lower metal roll 5 are in line contact. Therefore, the reliability of transcription is lacking.

The reason why it is difficult for the metal lower roll 5 to lift an appropriate amount of molten solder to the upper part is that the specific gravity of the molten solder is large, and since the metal lower roll 5 directly contacts the flexible circuit board 4, the surface needs to be smooth. It's for a reason. Moreover, even if the rotational speed of the metal lower roll 5 is increased, the moving speed of the flexible circuit board 4 sandwiched between the rolls also increases in proportion to the rotational speed of the rolls, and Another factor is that it is not possible to increase the amount of molten solder lifted. Since the lifting amount of molten solder cannot be adjusted, if the surface of the circuit wiring pattern of the flexible circuit board 4 shown in FIG. 3 is insulated with solder resist or the like,
If the surface position of the insulating material is more protruding from the metal lower roll 5 than the conductor surface position to be soldered, and the thickness of the molten solder layer on the metal lower roll 5 is relatively thin, the molten solder will become the conductor. Since it does not touch the surface, it is impossible for a solder printer to solder the surface of the conductor. Even if it is possible to solder the conductor surface, the thickness of the insulating material must be reduced in order to ensure soldering, which is unreasonable in terms of the insulation effect. Therefore, if the flexible circuit board 4 has a structure in which an insulating material is provided on a part of the surface of the conductor to be soldered, the reliability of the soldering process will be lacking.

The present invention specifically and suitably solves the problems of the conventional methods of soldering the conductor surface of the circuit wiring pattern of the well-known flexible circuit board.

According to the present invention, after applying flux to the soldering surface of the flexible circuit board with the circuit wiring pattern that requires soldering of the flexible circuit board facing downward, the flux is applied to the solder processing surface of the flexible circuit board, and then a cylindrical shape is formed by utilizing the flexibility of the flexible circuit board. , move the flexible circuit board to the bottom of the heater while directly contacting it with a U-shaped or V-shaped heater, and immerse it in a molten solder bath under the heater, or touch the jet of molten solder to remove the solder from the circuit wiring pattern. Make sure that it sticks sufficiently. After attaching the solder to the circuit wiring pattern, move the flexible circuit board upward along the heating heater, and before the flexible circuit board leaves the heating heater,
By adjusting the amount of solder on the circuit wiring pattern, the optimum soldering process is performed for the circuit wiring pattern of the flexible circuit board.

Hereinafter, the present invention will be further explained with reference to the illustrated embodiment. In FIG. 4, a flexible circuit board 8 is subjected to flexible coating with a flux coating device 12 with the circuit wiring pattern requiring soldering facing downward. A molten solder bath 10 is placed along a cylindrical heater 9 heated to a temperature above the melting point of the solder.
Soak in. The cylindrical heater 9 is illustrated as rotating as a roller for moving the flexible circuit board 8, but if a separate drive device is provided before and after the soldering process, the flexible circuit board 8 can be moved along the heater 9. As a means for moving the heater 9, it is also possible to fix the heater 9 without rotating it.

By immersing the flexible circuit board 8 in the molten solder tank 10, it becomes possible to apply enough solder to the circuit wiring pattern, which was a problem with the method using a solder printer, and the reliability of the soldering process is improved. problem will be resolved. However, the appropriate amount of solder depends on the width of the circuit wiring pattern, the surface tension of the solder, and
The solder layer thickness varies depending on the type of flux, the moving speed of the flexible circuit board 8, etc., and the thickness of the solder layer cannot be sufficiently controlled, and the amount of solder usually ends up being more than necessary.

Therefore, in order to adjust the thickness of the solder layer,
The flexible circuit board 8 is moved upward along the cylindrical heater 9, and before the flexible circuit board 8 is separated from the cylindrical heater 9, air heated to a temperature higher than the melting point of the solder is blown from the nozzle 11 at high speed. The thickness of the solder layer can be adjusted by blowing off excess molten solder onto the circuit wiring pattern of the circuit board 8. According to this method, the jig for preventing deformation or damage of the flexible circuit board, which is a problem with the method using a solder coater, is installed on the back side of the flexible circuit board 8 when heated air is blown from the nozzle 11. Since the cylindrical heater 9 is provided, the flexible circuit board 8 is not deformed by the heated air blowing, and a jig to prevent deformation or damage is not required. In addition, since conventional solder coaters are designed to solder rigid printed circuit boards of standard size, they cannot solder long lengths such as flexible circuit boards, but the method of the present invention can handle soldering of long lengths such as flexible circuit boards. Since the soldering process can be performed continuously, it becomes easier to process long items, and the problems of known methods can be effectively solved.

As described above, according to the molten solder processing method and apparatus for flexible circuit boards of the present invention, high performance and high performance can be achieved while optimally adjusting the amount of solder attached to the solder processing surface of this type of long flexible circuit board. It is possible to perform stable and reliable soldering. Furthermore, equipment costs and workability can be significantly improved, and the method is extremely useful as a means of contributing to cost reduction of this type of product.

[Brief explanation of drawings]

Figure 1 is a conventional process diagram for applying solder to the conductor surface of a circuit board by plating means, Figure 2 is a conceptual diagram of a conventional solder coater applied to hard printed circuit boards, and Figure 3 is also a hard solder coater. FIG. 4 is a conceptual block diagram of a conventional solder printer used for printed circuit boards, and FIG. 4 is a conceptual block diagram showing an apparatus for carrying out a soldering method for flexible circuit boards according to an embodiment of the present invention. . 8: Flexible circuit board, 9: Cylindrical heater, 10: Molten solder tank, 11: Heated air blowing nozzle, 12: Flux coating device.

Claims (1)

[Claims] 1. Move the flexible circuit board along the heating heater to a path where it comes into contact with the molten solder, and remove excess molten solder that has adhered to the wiring pattern surface of the flexible circuit board while being heated by the heating heater. A method for soldering a flexible circuit board, comprising performing solder processing on the wiring pattern surface of the flexible circuit board while adjusting the amount of solder adhering to the wiring pattern surface by blowing away with heated air. 2 comprising a molten solder tank and a heating heater arranged to move the wiring pattern surface of the flexible circuit board into contact with the molten solder in the tank, and a driving means for moving the flexible circuit board;
A soldering device for a flexible circuit board, comprising a heated air blowing device that works in conjunction with the heating heater to adjust the amount of solder attached to the wiring pattern surface. 3. The flexible circuit board solder processing apparatus according to claim 2, further comprising a device for applying flux to the solder processing surface on the feeding side of the flexible circuit board relative to the molten solder tank and the heating heater.