Metal fusion bonding – Including means to apply flux or filler to work or applicator – By partial or total immersion of work or applicator into liquid
Patent
1993-08-26
1995-01-10
Ramsey, Kenneth J.
Metal fusion bonding
Including means to apply flux or filler to work or applicator
By partial or total immersion of work or applicator into liquid
B23K 306
Patent
active
053799313
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a soldering machine comprising: a vessel opened at the top for filling with solder; at least two solder towers placed in the vessel, each adapted for delivering a flow of solder; from an upper portion of the tower and a transporting member for carrying along the objects for soldering above the solder towers.
Such soldering devices are generally known.
The problem often arises with such soldering devices that the solder flows falling back into the vessel cause splashes of solder which can spatter so high that they make contact with the underside of the objects for soldering such as the printed circuit boards for soldering.
This problem occurs particularly, although not exclusively, in soldering machines, wherein the soldering-process takes place inside an atmosphere of inert gas. These splashed solder droplets will make contact with the underside of the circuit board where they form solder globules. These globules adhere weakly to the other solder which is already on the circuit board so that there is a danger of them coming loose at a later time and short-circuiting another circuit portion. Although this problem occurs in the case of normal soldering machines placed in a normal atmosphere, the problem arises to a greater extent in soldering machines operating in an atmosphere substantially excluding oxygen. The low-oxygen atmosphere probably results in an increase of the surface tension, whereby the formation of droplets and globules of solder is stimulated.
The object of the present invention is to avoid the above stated problems.
This object is achieved in that the solder towers are adapted for generating solder jets directed toward each other, wherein the solder jets intersect before they make contact with the solder level prevailing in the vessel. As a result of these steps the, splashes caused by the fall of the combined solder jet on the solder level are shielded from the circuit board transported thereabove so that it is no longer possible for the solder splashes to contact the surface of the objects for soldering.
Similar problems occur when the object for soldering leaves the final solder jet. In this situation, certainly when the soldering process takes place in a nitrogen atmosphere, the solder also has the tendency to form globules on the object for soldering at the position where the solder wave leaves the object for soldering.
According to a preferred embodiment of the present invention the rear tower in the direction of movement is adapted for generating a jet of solder comprising a movement component counter to the movement of the objects for soldering.
As a result of this step any globules that may have formed are washed away by the solder jet so that the problems of such solder globules are prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will subsequently be elucidated with reference to the annexed figures, in which:
FIG. 1 shows a sectional view of a soldering device according to a first embodiment of the invention; and
FIG. 2 is a sectional view of an alternative embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
In the device shown in FIG. 1 the soldering device comprises a solder vessel 1 suitable for filling with solder 2. Understood by solder is any form of metal solder suitable for mutually connecting two other metals. Such a metal does not necessarily have to contain tin.
Arranged above vessel 1 is a conveyor belt 3 for transporting the objects for soldering, in the present case printed circuit boards 4. Such a conveyor belt forms the subject of the Netherlands patent application 8901014.
Two solder towers 5, 6 are further arranged in the solder vessel 1. The first solder tower is provided with a nozzle 7 which is adapted for generating a solder jet 8 which contacts the printed circuit board for soldering on the underside. Arranged in the solder tower 5 for this purpose is a pump 9 which is connected to the nozzle 7 by means of a channel 10.
The second solder tower 6 is likewise provided
REFERENCES:
patent: 3797724 (1974-03-01), Flury et al.
patent: 4802617 (1989-02-01), Deambrosio
patent: 4824010 (1989-04-01), Inoue et al.
patent: 4848642 (1989-07-01), Kondo
patent: 5156324 (1992-10-01), Hueste et al.
Ramsey Kenneth J.
Soltec B.V.
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