JPH10109160A - Soldering method and wave soldering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an insulation resistance from reducing by completely not leaving flux residual dross in the soldered part after soldering. SOLUTION: In the wave soldering device of a double wave system, the storage vessel 6 for the liquid 10 having reducing action is provided between a pre-heater 12 and a solder vessel 3, a first nozzle 7 of long sideways, wherein the liquid 10 is continuously fed at a given flow rate form the lower side with a pressure device circulating the liquid 10, and a second nozzle 8 of long sideways having an opening in adjacent to the first nozzle 7, wherein an about horizontal liquid receiving part is provided in the edge far from the first nozzle 7 and the liquid 10 is continuously fed at a given flow rate from the lower side with the pressure device, are provided in the carrying directional order of a printed wiring board, and the liquid 10 is jetted from the first nozzle 7 and the second nozzle 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the soldering of a printed wiring board (hereinafter referred to as a printed wiring board assembly) on which electric and electronic components such as surface-mounted components and components with leads are assembled, and in particular, cleaning after soldering. The present invention relates to a soldering method and an apparatus for eliminating the need for soldering.

[0002]

2. Description of the Related Art In a multilayer printed wiring board used for an electronic product, a conductor portion such as a pad or a through hole of a printed wiring board (also referred to as a card assembly) is connected to a component electrode or lead by soldering. And
2. Description of the Related Art Conventionally, a high-density mounting board in which surface-mounted components and insertion components are mixed is generally soldered by using both flow soldering and reflow soldering.

[0003] Among them, flow soldering is a method in which molten solder is jetted, a printed wiring board assembly is conveyed by a conveyer, and electrodes and leads of electric / electronic parts mounted by bringing the soldering surface into contact with the jetted solder. Is soldered to the pads and through-holes of the printed wiring board. As a general process, a flux is applied, then preheated (preheated), poured into a molten solder bath, soldered, and finally cooled. This flux application is an indispensable process to remove the oxide film of the soldering part and obtain good solderability, but the residue of this flux remaining after soldering corrodes the mounted electronic components, The insulation property may be degraded or a contact failure may occur. For this reason, cleaning is performed to remove the flux residue.However, with the progress of high-density mounting as in recent years, flux residue that has not been a problem in the past has led to a decrease in reliability and life of products. Tied. Therefore, it is important to consider how to completely remove the flux residue.

In addition, in order to reduce ozone layer depleting substances for the purpose of environmental protection, Freon used as a cleaning agent for removing flux after soldering of a printed wiring board assembly has recently been developed.
Ethane is a controlled substance and its use is banned.
For this reason, halogenated hydrocarbon solvents, hydrocarbon-based (petroleum-based) and alkaline saponifiers have been developed and commonly used as substitutes for these materials, but these substitutes are more efficient than chlorofluorocarbons and ethane. The capacity and workability are equal to or less than the above.Flux residues such as washing, rinsing with detergent, rinsing with city water, pure water, or alcohol, and then drying A more complicated cleaning process is required for removal than for CFCs and ethane. in this way,
There is a defect that it is difficult to completely remove the flux residue even if cleaning is performed through many of the steps described above using a material as a CFC substitute agent.

As a means for solving this defect, there has been proposed a soldering method in which the following flux is not applied so that no flux residue is left and the cleaning step itself becomes unnecessary. That is, it has a function of reducing oxides even when vaporized, and a liquid having a boiling point lower than the melting temperature of the solder, for example, a liquid such as formic acid or acetic acid is dropped on the molten solder liquid surface of the solder bath, and the rising vapor Apply the soldering part of the printed wiring board assembly to the surface to reduce and remove the oxide film adhering to the soldering part, and reduce the oxide floating on the surface of the molten solder by applying it to the jet of molten solder. This is a method of obtaining a good soldering portion (Japanese Patent Laid-Open No. 8-52564).

[0006]

However, this method has the following problems. In recent printed wiring board assemblies, various components having different shapes and sizes are mounted on a printed wiring board at a high density, so that the components are mounted very closely. In the case of a component arrangement in which small components are shadowed by large components because small components near the large components are conveyed on the conveyor, it is difficult for steam to enter the space between the lead and pad of the desired soldering portion properly. In this case, since the above-mentioned vapor does not properly enter, the oxides are not completely removed and remain in the soldered portions, causing a problem that the soldered portions are not soldered or have insufficient solder wetting (flow). Since the reducing liquid is heated and vaporized by heating at high temperature, it is necessary to surround the entire soldering device with a hood and remove the liquid odor, and forcibly exhaust the liquid. A large amount evaporates and the liquid is wasted. Liquid vapor having a reducing action flows forcibly into the exhaust port due to forced exhaust, and this vapor does not properly contact the soldering part of the printed wiring board assembly, so that oxides are formed as in the case of There is a problem that the solder is not completely removed and remains in the soldered portion, and the solder is not soldered or the solder is insufficiently wet. The present invention has been made to solve the above-mentioned problem, and good soldering can be performed without applying a flux by directly contacting a liquid for reducing an oxide with a soldering portion of a printed wiring board assembly. It is an object of the present invention to provide a soldering method and apparatus which will be described below.

[0007]

The present invention provides the following means for solving the above-mentioned problems. That is, in the soldering method, a liquid (acetic acid, oxalic acid) having a reducing action on a metal oxide is brought into direct contact with the soldering portion, and immediately thereafter, the soldering portion is brought into contact with the molten solder to perform soldering. It can be realized by doing.

In addition, this soldering method comprises a primary nozzle for forming a primary wave for ejecting molten solder in a substantially vertical direction, and a secondary nozzle for ejecting molten solder in a relatively quiet horizontal plane shape.
And a secondary nozzle for forming a next wave is sequentially provided in a conveying direction of the printed wiring board, and a lower surface of the printed wiring board is brought into contact with the primary wave and the secondary wave in order to perform a flow soldering. A storage tank for storing the liquid having a reducing action is provided between the preheater and the solder tank, a pressurizing device for circulating the liquid in the storage tank, a lower part is inserted into the liquid, and an upper part is formed of the liquid. A first horizontally elongated nozzle that projects upward from the liquid surface and opens substantially vertically upward, and the liquid is continuously supplied at a constant flow rate from below by the pressurizing device; Adjacent and likewise, the lower part enters the liquid, the upper part projects upwardly from the liquid level of the liquid and opens almost vertically upward, and the upper opening has a first opening.
A substantially horizontal liquid receiving portion is provided at an edge far from the nozzle, and a horizontally long second nozzle to which the liquid is continuously supplied at a constant flow rate from below by the pressurizing device is provided in the order of conveyance direction of the printed wiring board. And a jet-type soldering apparatus characterized in that the liquid is jetted from the first nozzle and the second nozzle.

[0009]

According to the present invention, since a liquid having a reducing action such as acetic acid or oxalic acid is brought into direct contact with the soldering surface, not only the surface of the component lead or the surface of the electrode on the printed wiring board assembly, but also the component lead. The liquid sufficiently penetrates and adheres to the pad gap between the pad portion and the component electrode portion, so that the oxide at the soldered portion can be completely removed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing one embodiment of the present invention,
FIG. 2 is a view taken in the direction of arrows AA in FIG. In FIG. 1, reference numeral 3 denotes a primary nozzle 4 which is filled with a molten solder 9 and has a jet port 15 for generating a primary molten solder wave therein, and a secondary nozzle 5 which has a jet port 16 for generating a secondary molten solder wave. , A preheater 12 for preheating the printed wiring board assembly 2, and a conveyor 11 for transporting the printed wiring board assembly. These components are the same as those of the conventional double wave type jet soldering apparatus. Things.

Reference numeral 6 denotes a storage tank provided between the preheater 12 and the solder tank 3 and filled with a liquid (acetic acid) 10 having a reducing action. A horizontally elongated (long in the direction perpendicular to the paper surface of FIG. 1) first nozzle 13 protruding upward and opening substantially vertically upward is a liquid 10 which is an upper opening of the first nozzle 7.
A jet port 8 for adjoining the first nozzle 7 has a lower portion similarly entering the liquid 10 and an upper portion projecting upward from the liquid surface of the liquid 10 and opening upward substantially vertically. The upper opening has a second nozzle provided with a substantially horizontal liquid receiving portion at an edge far from the first nozzle, and 14 is a jet port for jetting the liquid 10 which is the upper opening of the second nozzle. .

A pressurizing device (not shown) for circulating the liquid 10 is built in the storage tank 6, and the liquid 10 is continuously supplied at a constant flow rate from below the first nozzle 7 by the pressurizing device. . For this reason, the liquid 10 is ejected from the jet port 13 almost vertically, and a primary wave of the single mountain-shaped liquid 10 which is divided and flows down on both sides is formed. Liquid 10 in the same way
The liquid 10 is continuously supplied from below the second nozzle 8 at a constant flow rate. Therefore, the liquid 10 is ejected almost vertically from the jet port 14, but temporarily stays in the liquid receiving portion to form an almost horizontal, relatively quiet secondary wave of the liquid 10. As described above, the formation of the two types of waves is based on the same idea as the soldering of the double-wave type jet-type soldering apparatus, and the liquid 10 is applied only to the surface of the component lead or the surface of the electrode on the printed wiring board assembly. This is because the liquid sufficiently penetrates and adheres to the gap between the component lead and the pad portion and the component electrode portion and the pad.

Next, the operation of the jet type soldering apparatus according to the present invention will be described. The transport of the printed wiring board assembly 2 by the conveyer 11 and the soldering in the solder tank 3 are the same as those of the conventional jet-type soldering apparatus, and therefore description thereof is omitted. The printed wiring board assembly 2 is preheated by the preheater 12 without applying the flux, and is immediately brought into direct contact with the surface of the liquid 10 jetted from the first nozzle 7 and the second nozzle 8 of the storage tank 6. First nozzle 7
The liquid 10 is spouted vertically from the spout 13 and the liquid 10 is spouted almost horizontally and relatively quietly from the spout 14 of the second nozzle 8. Liquid 1 on the component lead and pad, and the component electrode and pad gap
Printed wiring board 2
The oxide of the soldered portion is reduced and completely removed.

Thereafter, the printed wiring board assembly 2 is immediately sent to the solder tank 3 and soldered. In this soldering step, the liquid 10 is evaporated and vaporized by the heat of the molten solder.

[0015]

According to the present invention, as described above,
Instead of applying the flux, a liquid having a reducing action is jetted to make direct contact with the soldering part of the printed wiring board assembly, so that this liquid is the gap between the component lead and the pad or the electrode and the pad. This liquid will contact and adhere uniformly to all parts of the printed wiring board assembly where high-density mounting requires soldering, and the oxide in the soldered parts will be reduced completely. Since it is removed, good soldering is obtained. Therefore, cleaning for removing the flux residue is not required, and the printed wiring board assembly can be soldered at low cost.

Further, since the liquid having a reducing action is not evaporated and vaporized at a high temperature, it is not necessary to surround the entire soldering apparatus with a hood to remove the odor of the liquid and forcibly exhaust the liquid. No longer
Soldering becomes possible at low cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a view as viewed in the direction of arrows AA in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Jet type soldering apparatus, 2 ... Printed wiring board assembly, 3 ... Solder tank, 4 ... Primary nozzle, 5 ... Secondary nozzle, 6 ... Storage tank, 7 1st nozzle 8 2nd nozzle 9 ... molten solder 10 ... liquid with reducing action 11 ... conveyor 12 ... preheater 13, 14, 15, 16 ... spout.

Claims (3)

[Claims] 1. A soldering method comprising: immediately bringing a liquid having an action of reducing a metal oxide into contact with a soldering portion, and immediately bringing the soldering portion into contact with molten solder to perform soldering. Method. 2. The soldering method according to claim 1, wherein the liquid having a reducing action is acetic acid or oxalic acid. 3. A printed wiring comprising: a primary nozzle for forming a primary wave for ejecting molten solder in a substantially vertical direction; and a secondary nozzle for forming a secondary wave for ejecting molten solder in a relatively quiet horizontal plane shape. In a jet type soldering apparatus which is provided sequentially in the board conveying direction, and in which the lower surface of the printed wiring board is brought into contact with the primary wave and the secondary wave in sequence and flow soldering is performed, the reducing action is provided between the preheater and the solder bath. A storage tank for storing the liquid; a pressurizing device for circulating the liquid in the storage tank; a lower part entering the liquid; an upper part projecting upward from the liquid surface of the liquid and substantially vertically upward. A first horizontally elongated nozzle which is continuously opened at a constant flow rate from below by the pressurizing device, and the lower portion of which is adjacent to the first nozzle and has the same The upper portion projects upward from the liquid surface of the liquid and opens upward substantially vertically, and the upper opening is provided with a substantially horizontal liquid receiving portion along an edge far from the first nozzle. And a horizontally long second nozzle to which the liquid is continuously supplied at a constant flow rate from below by the pressurizing device, is provided in the order of conveyance of the printed wiring board, and upper openings of the first nozzle and the second nozzle are provided. A jet-type soldering device, wherein the liquid is jetted from a part.