Soldering apparatus

An apparatus for soldering printed circuit boards moving along a predetermined path of travel, comprises an upwardly extending nozzle member having an opening at its top end from which molten solder is caused to overflow to form an overflowing molten solder with which the underside surface of the printed circuit board is contacted, and an adjustable outlet member rotatably disposed in the opening to define an outlet extending in the direction transverse to the path of travel, so that by adjusting the angular position of the outlet member the orientation of the outlet may be varied for adjustment of the direction and height of the overflowing solder.

This invention relates to an apparatus for soldering printed circuit 
boards. 
There have thus far been proposed various soldering apparatuses for printed 
circuit boards. When applied to printed circuit boards bearing chip type 
electric parts such as resisters and condensers, however, the known 
apparatuses invariably give rise to problems of soldering failures due to 
the recesses defined between adjacent chip type parts or behind the chip 
type parts as seen in the direction of travel of the boards. Such recesses 
or space can block the molten solder from flowing thereinto and can trap 
gases therein, causing incomplete deposition of the solder. The air 
bubbles, once trapped in the recesses, are difficult to remove even if the 
molten solder is poured over the printed circuit board over a long period 
of time. 
To cope with this problem, there is proposed in U.S. Pat. No. 4,465,219 a 
wave soldering apparatus capable of adjusting the direction and height of 
the solder wave so as to provide optimum contact between the molten solder 
and the printed circuit boards. An embodiment of this prior art apparatus 
is shown in FIG. 19 of the accompanying drawings, in which the reference 
numeral 3 denotes an upwardly converged nozzle member having an overflow 
outlet 4 extending in the direction perpendicular to the direction shown 
by the arrow A along which a printed circuit board 1 bearing temporarily 
mounted chip parts 2 travels. A molten solder 5 is caused to overflow from 
the outlet 4 to form thereover a solder wave 5a. The front plate of the 
nozzle member 3 has an L-shaped plate 6 mounted on a V-shaped plate 7 
which in turn is mounted on a stationary plate 9. The position of the 
L-shaped plate 6 is adjustable horizontally in the direction parallel to 
the direction A of the travel of the printed circuit board 1 while the 
position of the V-shaped plate 7 is adjusted vertically, so that the 
orientation and size of the area of the overflow outlet 4 may be varied 
for the adjustment of the direction and height of the overflowing solder 
wave 5a. 
One problem associated with the above described appratus is that it is 
troublesome and time consuming to vary the position of the plates 6 and 7. 
Especially, it is very difficult to control the orientation of the 
overflow outlet 4. 
With the foregoing situations in view, the present invention is aimed at 
the provision of an apparatus for soldering printed circuit boards 
travelling along a predetermined path of travel, which permits easy 
adjustment of the direction of solder wave. 
Another object of the present invention is to provide a soldering apparatus 
which can provide various shapes of soldering wave such as thin solder 
waves having a high flowing speed suitable for soldering printed circuit 
boards bearing small outline integrated circuits. 
In accordance with the present invention there is provided an apparatus for 
soldering printed circuit boards moving along a predetermined path of 
travel, said apparatus comprising: 
an open-topped tank located for containing a molten solder; 
an upwardly extending nozzle member having the lower end thereof in flow 
communication with said tank and the upper end thereof defining an opening 
extending laterally in the direction transverse to said path of travel; 
solder feed means operable for supplying said molten solder in said tank to 
said nozzle member to cause said molten solder to overflow from said 
opening, with the underside surface of the printed circuit board being 
contacted with the overflowing molten solder; and 
outlet means disposed in said opening to reduce the area of said opening 
and to define a laterally extending outlet, said outlet means being 
rotatable about an axis oriented transversely to said path of travel so 
that by adjusting the angular position of said outlet means the 
orientation of said outlet may be varied for adjustment of the direction 
of said overflowing solder.

Referring to FIGS. 1-3, the reference numeral 12 denotes a tank which is 
generally rectangular in shape and which is open on the top side thereof. 
The tank 12 contains a molten solder or melt 13 which is maintained at a 
suitable temperature by a heating element (not shown). The melt 13 is 
applied to printed circuit boards by solder applicator means generally 
indicated by a reference numeral 11. 
Disposed within the tank 12 is an upwardly extending nozzle member 14, the 
lower end of which is connected to one end of a conduit 17. At the other 
end, the conduit 17 is provided with a molten solder supply hole 18 which 
is opened toward the bottom of the tank 12. Consequently, the lower 
portion of the nozzle member 14 is in flow communication with the tank 12. 
The nozzle member 14 is formed in a substantially rectangular shape in 
section and has a sectional area gradually reduced from its middle portion 
toward its upper tip end. More specifically, of the two pairs of opposing 
walls which define the configuration of the nozzle member 14, the side 
plates are disposed substantially parallel with each other but the front 
and rear plates converge toward the upper end of the nozzle member 14. 
A feed means is provided in the tank 12 for continuously supplying the 
molten solder 13 in the tank 12 to the nozzle member 14. The feed means 
preferably includes a propeller assembly 15 which is disposed in the 
conduit 17 adjacent to the opening 18. The propeller 15 is provided with a 
shaft which is connected to drive means including a motor 16, so that it 
is rotated about the shaft upon actuation of the motor 16 to supply the 
molten solder 13 in the tank 12 continuously to the nozzle 14. The 
supplied molten solder flows upward through the nozzle 14, overflows from 
its upper end 19 to form an overflowing wave or layer 13a and, then, 
return to the tank 12. 
The opening 19 which is defined at the upper end of the nozzle 14 extends 
laterally in the direction transverse to a direction A along which a 
printed circuit board 1 bearing chip type electric parts 2 temporarily 
attached to its underside by means of an adhesive or solder paste is fed 
by operation of ordinary transfer means. In this instance, it is preferred 
that the printed circuit board 1 travel in a rearwardly inclined posture 
and along a similarly inclined path of travel at an angle of .theta..sub.1 
with respect to a horizontal plane so that the molten solder excessively 
applied to the board 1 can drop in a facilitated manner. As the printed 
circuit board 1 passes over the nozzle 14, its lower side is brought into 
contact with the overflowing molten solder 13a for soldering the electric 
parts 2 on the underside of the printed circuit board 1. 
Provided within the opening 19 at the upper end of the nozzle 14 is an 
outlet means 20 to reduce the area of the size of the opening 19 and to 
define a laterally extending outlet 22 (FIG. 2). The outlet means 20 in 
this embodiment includes a pair of longitudinally curved or arcked plates 
20a and 20b rotatably disposed about an axis C. As shown in FIG. 4, the 
plates 20a and 20b are disposed to define between them two laterally 
extending apertures one of which serves as the overflow outlet 22 with the 
other aperture serving as an inlet port 21 for permitting the molten 
solder 13 introduced into the nozzle 14 to be passed therethrough to the 
outlet 22. 
The width and orientation of the outlet 22 may be varied by adjusting the 
positions of the plates 20a and 20b. As shown in FIGS. 2 and 3, the curved 
plate 20b has connecting plates 25b and 26b at opposing ends thereof. The 
connecting plate 25b is fixedly secured to an outer shaft 23b which is 
rotatably received in a bore of one of the opposing side plates of the 
nozzle 14. The connecting plate 26b, on the other hand, is rotatably 
supported about a shaft 24 secured to the other, opposite side plate of 
the nozzle 14. Similarly, connecting plates 25a and 26a are provided at 
opposite ends of the curved plate 20a. The connecting plate 25a is fixed 
to an inner shaft 23a which is rotatably received by a bore formed in the 
outer shaft 23b, while the connecting plate 26a is rotatably supported on 
the shaft 24. The inner and outer shafts 23a and 23b are concentric with 
the axis C about which there are rotatable. 
Consequently, by rotating the inner and outer shafts 23a and 23b, the 
curved plates 20a and 20b are rotated about the axis C so that the width 
and orientation of the outlet 22 defined therebetween may be varied. By 
adjusting the orientation and width of the outlet 22, soldering operation 
may be effected in various manner with the single apparatus as shown in 
FIGS. 4 through 6. 
FIG. 4 illustrates a state of the apparatus in which the curved plates 20a 
and 20b are positioned to form a solder wave suitable for performing flow 
dip soldering of printed circuit boards which bear electric components 
having lead wires depending from the underside of the boards. The 
reference numeral 27 designates a guide plate on which a moving layer 13a 
of the overflowing molten solder is supported. To the rear end of the 
plate 27 is fixed a dam plate 28 by means of screws 29. The position of 
the plate 28 is vertically adjustable for controlling the height of the 
solder layer 13a. The molten solder in the tank 12 (FIG. 1) is fed to the 
nozzle 14 and is passed through the aperture 21 to the overflow outlet 22. 
The overflowing solder forms the layer or wave flowing on the plate 27 in 
the directions parallel with and opposite to the direction A along which 
printed circuit boards 1 carrying electric parts 2a travel. The printed 
circuit boards 1 are brought into contact with the solder wave 13a to 
effect dip soldering. 
When soldering printed circuit boards bearing chip parts by dip soldering, 
the overflow outlet 22 is narrowed and is oriented upward as shown in FIG. 
5 to form a protruded wave 13b. The printed circuit boards are contacted 
with the apex portion of the protruded wave 13b. 
As shown in FIG. 6, by further narrowing the width of the outlet 22 and by 
orienting the outlet toward the direction opposite to the direction A of 
the travel of the printed circuit boards, there is formed an overflowing 
wave 13c extending in the direction opposite to the direction A. Such an 
overflowing solder wave 13c is effective in preventing the formation of 
"bridges" and "icicles" of the solder. 
In the above embodiment, the connecting plates 25a and 26a, and 25b and 26b 
have fan-like forms whose peripheral, arcked edges have lengths equal to 
the peripheral widths of the arcked plates 20a and 20b respectively. 
However, the connecting plates 25a and 26a, and 25b and 26b may have any 
desired structure (shape, size and position), although it is preferred 
that they are positioned at both ends of the arcked plates 20a and 20b and 
have sizes effective for reducing the amount of the molten solder escaping 
laterally from the outlet 22. 
Another embodiment of the outlet means 20 is shown in FIGS. 7 through 9, in 
which the same reference numerals designate similar component parts. The 
outlet means 20 in this embodiment includes only one curved plate 30 
having a structure similar to the plate 20a or 20b. Thus, the curved plate 
30 has a connecting plate 36 at its one end. The connecting plate 36 is 
rotatably supported by a shaft 34 fixed to a side plate of the nozzle 
member 14. The other end of the curved plate 30 is connected to a 
connecting plate (not shown) to which a shaft (not shown) is secured. The 
shaft is rotatably received by a bore in the side wall of the nozzle 14. 
Of the two pairs of the side walls constituting the nozzle 14, the front 
side wall has an elongated upper portion 33 curved in the direction of the 
arrow A. Between the upper portion 33 and the curved plate 30 is defined 
an overflow outlet 32. The orientation and the width of the outlet 32 may 
be varied by adjusting the angular position of the curved plate 30. 
When the curved plate 30 is positioned to provide a wide width for the 
outlet 32, as shown in FIG. 7, there is formed a layer 13a of molten 
solder similar to that of FIG. 4. As shown in FIG. 8, by narrowing the 
width, a protruded wave 13b is formed in the same manner as in FIG. 5. In 
FIG. 9, the width is further narrowed to form an overflowing wave 13c 
similar to that of FIG. 6. 
A further embodiment is shown in FIGS. 10 and 11, in which the same 
reference numerals designate similar component parts. Outlet means 20 in 
this embodiment includes a curved plate 40 having a structure similar to 
that of the embodiment shown in FIGS. 7 through 9. The inwardly curved 
portion 33 of FIG. 7 is removed and replaced by an outwardly extending 
guide plate 43. When the curved plate 40 is positioned to provide a wide 
width for the outlet 42, as shown in FIG. 10, there is formed a layer 13a 
of molten solder similar to that of FIG. 4. As shown in FIG. 11, by 
narrowing the width, a thin wave 13c is formed in the same manner as in 
FIG. 6. 
FIGS. 12 and 13 illustrates a further embodiment of the outlet means 20. 
The outlet means 20 includes a cylindrical member 50 mounted in the top of 
the nozzle 14 for closing the opening 19. The cylindrical member 50 is 
disposed so that its axis C is oriented in the direction transverse to the 
direction A along which the printed circuit boards 1 travel. The 
cylindrical member 50 is provided with an aperture or slit 52 extending 
axially in parallel with the axis C. Also provided in the cylindrical 
member 50 is an aperture or hole 51 at a location opposite to the slit 52. 
Thus, the molten solder supplied in the nozzle 14 is passed through the 
aperture 51 serving as an inlet and is discharged or ejected from the slit 
52 serving as the overflow outlet. The overflowing or ejected molten 
solder forms a solder wave 13c with which the printed circuit boards 1 are 
contacted. 
In the specific embodiment shown, there is disposed an inner cylinder 57 
concentrically within the cylindrical member 50 to define an annular 
passage through which the molten solder is passed from the inlet 51 to the 
outlet 52. The overflowing molten slder 13c is collected in a chamber 59 
defined by side and bottom plates 59a and is returned to the tank 12 
through exits 60 provided in the opposite end of the chamber 59. 
The direction of the overflowing or ejected molten solder wave 13c may be 
varied by adjusting the angular position of the cylindrical member 50. 
Thus, the opposite ends of the cylindrical member 50 are closed by 
connecting plates 55 and 56. The plate 56 is rotatably supported by a 
shaft 54 which is secured to a side wall of the nozzle member 14. The 
other plate 55 is fixed to a shaft 53 which is rotatably received in a 
bore of a side wall of the nozzle member 14. As a result of this 
construction, by turning the shaft 53, the cylindrical member 50 may be 
rotated about the axis C so that the direction in which the molten solder 
is ejected (angle .theta..sub.2) from the outlet 52 may be adjusted at 
will. After the adjustment of the direction of the solder wave 13c, the 
cylindrical member 50 is fixed at that position by turning a screw 58. 
The solder wave applicator means 11 described in the foregoing are suitably 
used as one of the two solder applicators of a dual-stage soldering 
apparatus in combination with another solder applicator capable of forming 
a laterally moving progressive wave. One such application is shown in FIG. 
14 in which the solder applicator 11 shown in FIG. 12 is used for a 
secondary soldering step. 
Referring to FIGS. 14 and 15, the reference numeral 63 denotes a pot which 
is generally rectangular in shape and which is open on the top side 
thereof. The pot 63 is divided by a partition wall 63a into separate first 
and second tanks 64 and 65 in a tandem fashion, i.e. in a direction 
parallel with the direction indicated by the arrow A along which printed 
circuit boards to be soldered are successively moved. The first and second 
tanks 64 and 65 contain molten solders or melts 66 and 67, respectively. 
The melts 66 and 67 are maintained at suitable temperatures by heating 
elements (not shown) such as electric coils. The melts 66 and 67 are 
repsectively applied to printed circuit boards by first and second solder 
applicatior means which are generally indicated by reference numerals 68 
and 11. 
Disposed within the first tank 64 is an upwardly extending riser 69 having 
at its top end a laterally extending opening on which is slidably mounted 
a cylindrical nozzle member 72 having a plurality of substantially equally 
spaced apart overflow throughholes or ports, generally designated 73a and 
73b, which are arranged in a direction parallel with the axis of the 
nozzle member 72 and which are in fluid communication with the riser 69. 
Means (not shown) are provided so that the molten solder 66 in the tank 64 
is continuously introduced into the riser 69 and is forced to overflow 
from respective ports 73a and 73b to form over the nozzle member 72 
standing waves 66a and 66b having a plurality of raised or protruded 
portions at positions corresponding to the overflowing ports 73a and 73b. 
As shown in FIGS. 16 through 18, the through holes 73a and 73b are 
alternately arranged in a row and each spaced apart at an equal distance 
P. The through holes 73a are tilted at an angle alpha toward the direction 
A, whereas the through holes 73b are tilted at an angle beta in the 
direction opposite to the direction A. As a consequence of this 
arrangement, the wave 66a of molten solder overflowing from the through 
holes 73a is deflected in the same direction A of the travel of the 
printed circuit boards, while the wave 66b is deflected in the direction 
opposite to that along which the printed circuit boards travel. The wave 
66a is effective in preventing the occurrence of soldering failure at rear 
ends of chip parts while the wave 66b is effective in preventing the 
occurrence of soldering failure at front ends of the chip parts. 
The orientation angles alpha and beta of the through holes 73a and 73b are 
selected to provide suitable height of the apices of the waves 66a and 
66b. The open ends of the through holes 73a and 73b need not be arranged 
in one row. They may be arrayed in different rows, i.e. in a zig-zag 
fashion. 
Referring again to FIG. 14, drive means 74 are provided to reciprocally and 
slidably move the nozzle member 72 in the axial direction, i.e. in a 
direction transverse to the path of travel A of the printed circuit board 
1, as shown by the arrow B, so that the standing waves 66a and 66b of 
molten solder overflowing from the reciprocally moving ports 73a and 73b 
form progressive waves progressing in the same direction as the movement 
of the nozzle member 72. The drive means 74 of this embodiment includes a 
motor 77 whose drive axis is fixedly secured to a balance wheel 76. A 
crank shaft 75 is slidably received by a guide 75a provided on the pot 63 
and has its one end connected to the nozzle member 72 and its other end 
pivotally connected to a drive shaft 76a rotatably connected to the 
balance wheel 76. Upon rotation of the motor 77, the nozzle member 72 is 
reciprocally displaced. It is preferred that the nozzle member 72 displace 
in its every half cycle of the reciprocation through a distance 
substantially equal to an integer multiple of the distance P between the 
adjacent two overflowing ports 73a (or 73b). 
Referring to FIG. 15, the printed circuit boards 1 each having chip-type 
electric parts 2 temporarily attached to its lower side by means of an 
adhesive or the like are fed from left to right, as viewed in FIG. 15, or 
in the direction of the arrow A, along the predetermined path of travel by 
operation of conventional trnasfer means. As the printed circuit board 1 
passes over the first solder applicator 68, its lower side is brought into 
counter-current and cocurrent contact with the progressive waves 66b and 
66a of molten solder for soldering the parts on the underside of the board 
1. Since the upper surface of each of the solder waves 66a and 66b is 
continuously moved in a direction transverse to the direction of the 
travel of the printed circuit board 1, the molten solder can arrive at the 
recessed portions of the chip parts-bearing printed circuit board 1 in an 
accelerated manner without permitting gases to be trapped in those 
portions. 
The printed circuit board 1 which has undergone the soldering treatment 
with the molten solder 66 in the first solder tank 64 is then passed to 
the adjacently located second applicator 11 for contact with the second 
molten solder 67 in the second tank 65 in a manner such as shown in any of 
FIGS. 4 through 12. 
The invention may be embodied in other specific forms without departing 
from the spirit or essential charcteristics thereof. The present 
embodiments are therefore to be considered in all respects as illustrative 
and not restrictive, the scope of the invention being indicated by the 
appended claims rather than by the foregoing description, and all the 
changes which come within the meaning and range of equivalency of the 
claims are therefore intended to be embraced therein.