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
Reexamination Certificate
2000-05-01
2002-04-02
Dunn, Tom (Department: 1725)
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
Reexamination Certificate
active
06364195
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a brazing apparatus using an electromagnetic induction pump. More specifically, the present invention relates to a brazing apparatus having a pluralty of reservoirs for brazing filler metal, wherein the height of the reservoirs may be adjusted independently. The present invention also relates to a brazing apparatus having an intermediate processing space capable of accommodating an intermediate processing device such as a warp correcting device or a flux applying device. The present invention also relates to a brazing apparatus having a pluralty of reservoirs fitted with local nozzles capable of soldering a local area of a workpiece. In this latter arrangement, there is no restriction as to the orientation of the reservoirs with respect to each other and multiple workpieces may be processed simultaneously.
FIG. 15
shows the general structure of a conventional wave soldering device, wherein a work conveyor
14
adapted to convey workpieces to be soldered, such as component-mounted substrates or the like, extends from a workpiece inlet
12
to a workpiece outlet
13
of a device cover
11
.
A fluxer
15
for applying foamed flux to workpieces, a preheater
16
for preheating the workpieces, a solder bath
17
for soldering the workpieces by using molten solder ejected from wave nozzles, and a fan
18
for cooling the workpieces after soldering are arranged in this order along the conveyor
14
.
A primary wave nozzle
21
a and a secondary wave nozzle
21
b
are disposed in the solder bath
17
. A wave-forming plate
22
has numerous ejection holes is disposed at the open top of the primary wave nozzle
21
a
. The primary wave nozzle
21
a
is adapted to feed molten solder over the entire workpiece, covering every corner of the electrode portions and other parts of chip components by means of numerous small primary waves W
1
which are ejected as irregular spouts from the ejection holes of the wave-forming plate
22
. The secondary wave nozzle
21
b
is adapted to adjust the shapes of soldered parts by means of gentle secondary waves W
2
.
As shown in
FIG. 16
, the solder bath
17
is provided with a pressure duct
23
fitted in an opening at the bottom of the nozzle body
21
of the wave nozzles
21
a
,
21
b
, and a pump impeller
24
disposed at the end of the pressure duct
23
. The solder bath
17
also includes a suction opening
25
and a motor drive mechanism
26
associated with the pump impeller
24
.
Molten solder introduced from the suction opening
25
as a result of rotation of the pump impeller
24
is fed under pressure through the pressure duct
23
into the nozzle body
21
and emitted from the nozzle body
21
in waves so that the undersides of workpieces P, which may be component-mounted substrates, are soldered while they are conveyed, being held between conveyor claws
27
of the conveyor
14
. The major part of the solder waves directly returns onto the molten solder surface
28
in the solder bath
17
and is circulated into the suction opening
25
of the pump impeller
24
.
Various brazing apparatuses using an electromagnetic pump are disclosed in, for example, Japanese Patent Publication Nos. 42590-1976, 31628-1990 and 60581-1991, and Japanese Utility Model Publication No. 17572-1988. Electromagnetic pumps used in those brazing apparatuses are either a direct current type or an alternating current type.
A direct-current type electromagnetic pump is adapted to generate a thrusting force to a conductive brazing filler metal, such as tin, over its path of motion by applying a magnetic field perpendicularly to the path of the conductive brazing filler metal and feeding direct electric current perpendicularly to both the path of motion and the magnetic field.
An alternating-current type electromagnetic pump is an electromagnetic induction pump which includes induction coils arranged on a plane along a path traveled by a conductive brazing filler metal and is adapted to generate a thrusting force to the brazing filler metal by feeding AC current having lagged phases to the induction coils, thereby generating a shifting magnetic field in the path traveled by the conductive brazing filler metal to permit the electromagnetic induction to generate electromotive force on the conductive brazing filler metal in its path of motion so that electric current generated by the electromotive force of the brazing filler metal flows in the magnetic flux in the magnetic field.
With a wave soldering device of a type which calls for force-feeding molten solder by means of a pump impeller rotated by a conventional motor drive mechanism, it is difficult to reduce the amount of solder, because of structural limitations in how small the solder bath can be.
To be more precise, as the solder bath has
17
to be sufficiently deep in order to prevent oxidized solder from being entangled in the portion where the impeller is turning, the volume of the entire solder bath
17
becomes large.
On the other hand, although a conventional brazing apparatus which calls for force-feeding brazing filler metal by using an electromagnetic pump and ejecting it in the form of waves requires less brazing filler metal compared with the wave soldering device described above, it occupies a considerable space along the conveyance path of workpieces.
For this reason, unlike a motor-driven wave soldering device, no conventional electromagnetic pump type brazing apparatus has ever employed the art that calls for serially arranging two brazing apparatus and performing two kinds of brazing by means of primary waves and secondary waves.
Simply arranging two conventional electromagnetic pump type brazing apparatuses to be used respectively for primary brazing and secondary brazing would not only double the surface area of the device, which would tale up too much space, but also require twice as much brazing filler metal.
Due to environmental protection regulations, the demands for brazing filler metal which does not contain lead (what is generally called lead-free solder) are recently on the increase. As lead-free solders are made of materials such as indium or the like, which are 3 to 10 times as expensive as ordinary solder made of tin and lead, it is necessary to reduce the quantity of the brazing filler metal to be used as much as possible.
OBJECTS AND SUMMARY OF THE INVENTION
In order to solve the above problems, an object of the present invention is to provide an electromagnetic pump type brazing apparatus which is capable of forming waves at a plurality of locations without taldng up much space. Another object of the present invention is to provide an electromagnetic pump type brazing apparatus which is capable of reducing the quantity of brazing filler metal.
Briefly stated, the present invention is a brazing apparatus having at least a first and second reservoir for holding a brazing filler metal. The first and second reservoirs are disposed along a predetermined conveyance path of a workpiece. A first nozzle is disposed on and in communication with the first reservoir and ejects a first wave of brazing filler metal from the first reservoir. A second nozzle is disposed on and in communication with the second reservoir and ejects a second wave of brazing filler metal from the second reservoir. A means for adjusting the height of the first and second reservoirs allows for the height of the reservoirs to be adjusted independently from one another.
In an embodiment of the present invention, a brazing apparatus is provided including a plurality of reservoirs adapted to contain brazing filler metal, and a plurality of electromagnetic induction pumps adapted to braze workpieces by ejecting upward the brazing filler metal contained in the reservoirs, said reservoirs arranged along the predetermined conveyance path of workpiece and having vertically extending vertical plate portions in the shape of a plate, and the electromagnetic induction pumps disposed respectively along specified vertical plate portions of the reservoirs.
With the configuration as
Masuda Tsugunori
Onozaki Junichi
Saito Hiroshi
Dunn Tom
Kabushiki Kaisha Tamura Seisakusho
Morrison Law Firm
Stoner Kiley
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