Abstract:
A solder dross recovery module has gears and a waste collection chamber positioned within a solder pot. The gears are configured to draw in solder dross from a surface of molten solder stored in the solder pot. The gears apply pressure to the solder dross so as to separate solder from the solder dross. The recovered solder is returned to the molten solder in the solder pot. A resulting waste material is collected in the waste collection chamber.

Description:
FIELD OF THE INVENTION 
     The present invention is generally directed to recovering solder from solder dross. More specifically, the present invention is directed to a solder dross recovery module that can be attached to a solder pot. 
     BACKGROUND OF THE INVENTION 
     Wave soldering is a bulk soldering process used to solder components to a printed circuit board. Solder is held in a wave soldering pot where the solder is heated and maintained in a molten state. The molten solder is pumped through a wave nozzle to form an up-welling of solder that appears as a standing wave. The printed circuit board is passed over the molten solder wave such that the component leads contact the molten solder. 
     An issue with the wave soldering device is that maintaining the solder in a molted state results in the formation of solder dross. Solder dross is a mass of impurities floating on the molten solder. The surface of the molten solder is exposed to air, and the solder dross is formed by oxidation of the molten solder. 
     Solder is an expensive material, but the solder dross is not useable due to the impurities. It is common practice to recycle the solder dross back to solder, which can then be reused. Different recycling techniques have been developed. One recycling technique is the periodic application of chemicals to the solder dross formed on the surface of the molten solder. The chemicals dissolve the oxides within the solder dross, however a resulting slag remains as waste. This slag must be periodically removed, typically by skimming. The slag is a messy material that may dirty other components of the wave soldering apparatus. Removing the slag is done manually, which is time consuming and costly, as well as dangerous since the molten solder is heated to at least 500 degrees Fahrenheit. The chemicals themselves are also costly and need to be periodically applied. Examples of such chemicals include a sodium hydroxide additive or a surfactant. A wave oil can also be used to reduce the formation of solder dross. The wave oil is applied to the surface of the molten solder and acts as a barrier between the molten solder and the atmosphere, thereby reducing oxidation and the formation of solder dross. However, wave oil does not completely eliminate the formation of solder dross, so the solder dross that does form still needs to be dealt with. The wave oil is also costly and needs to be periodically applied. 
     Another recycling technique is to physically separate the solder from the solder dross. In some cases, the solder dross is processed while still on the surface of the molten solder. This separation process can be as simple as using two stainless steel spatulas to squeeze the solder out from the solder dross. However, the safety and health of the operators is a concern considering the high temperature of the molten solder and the generation of harmful airborne particles during the separation process. In other cases, offline solder dross recovery machines are used. An operator needs to remove the solder dross from the wave soldering pot and place the recovered solder dross into a recovery pot in the offline solder dross recovery machine. However, during this transfer process the solder dross cools and hardens. For the machine to separate the solder from the solder dross, the solder dross must be heated to a molten temperature. This requires the machine to have a heater. Time is also required to melt the cooled solder dross. Also, not all solder is made of the same material, and therefore different offline solder dross recover machines are needed for different types of solder so as to avoid contamination. Good ventilation is also required during the operation. 
     SUMMARY OF THE INVENTION 
     Embodiments are directed to a solder dross recovery module having gears and a waste collection chamber positioned within a solder pot. The gears are configured to draw in solder dross from a surface of molten solder stored in the solder pot. The gears apply pressure to the solder dross so as to separate solder from the solder dross. The recovered solder is returned to the molten solder in the solder pot. A resulting waste material is collected in the waste collection chamber. 
     In an aspect, a solder dross recovery module is disclosed. The solder dross recovery module includes a plurality of interconnected gears, a motor and a waste material collector. At least one of the gears is at least partially submerged in molten solder and solder dross floating on a surface of the molten solder contained within a solder pot. The motor is coupled to the plurality of interconnected gears. The motor is configured to rotate the plurality of interconnected gears and the plurality of interconnected gears are configured to apply pressure to the solder dross floating on the surface of the molten solder thereby separating solder from the solder dross and dispensing a waste material. The waste material collector is positioned adjacent to the plurality of interconnected gears and configured to collect the dispensed waste material. In some embodiments, the solder dross recovery module further comprises support walls configured to support the plurality of interconnected gears and to enable the separated solder to be fed back to the molten solder in the solder pot. In some embodiments, the motor and the plurality of interconnected gears are configured to drive the plurality of interconnected gears in a forward direction thereby drawing molten solder in the solder pot and solder dross floating on the surface of the molten solder toward the solder dross recovery module. In some embodiments, the motor and the plurality of interconnected gears are further configured to drive the plurality of interconnected gears in a backward direction opposite the forward direction. In some embodiments, the plurality of interconnected gears comprise a first subset of gears including the at least one gear at least partially submerged in molten solder and a second gear, wherein the solder dross is drawn between the at least one gear at least partially submerged in molten solder and the second gear, and pressure is applied to the solder dross by the at least one gear at least partially submerged in molten solder and the second gear. In some embodiments, the first subset of gears of the plurality of interconnected gears comprise spur gears. In some embodiments, the plurality of interconnected gears further comprise a second subset of gears, wherein the second subset of gears are coupled to the motor. In some embodiments, the solder dross recovery module further comprises a camshaft, wherein a first end of the camshaft is coupled to the first subset of gears and a second end of the camshaft is coupled to the second subset of gears. In some embodiments, the first subset of gears and the waste material collector are positioned within an interior of the solder pot and the second subset of gears and the motor are positioned external to the solder pot. In some embodiments, the second subset of gears of the plurality of interconnected gears comprise miter gears. In some embodiments, the solder dross recovery module further comprises a mounting structure configured to mount the solder dross recovery module to the solder pot. In some embodiments, the mounting structure comprises a U-clamp configured to fit over a side wall edge of the solder pot. 
     In another aspect, the solder dross recovery module is included as part of a solder dross recovery system. The solder dross recovery system includes a solder pot and the solder dross recovery module. The solder pot is configured to maintain and contain molten solder, wherein solder dross is formed on at least a portion of a surface of the molten solder. In some embodiments, the solder dross recovery system further comprises a control module coupled to control the motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Several example embodiments are described with reference to the drawings, wherein like components are provided with like reference numerals. The example embodiments are intended to illustrate, but not to limit, the invention. The drawings include the following figures: 
         FIG. 1  illustrates a solder dross recovery system according to some embodiments. 
         FIG. 2  illustrates a top-down front right perspective view of the solder dross recovery module according to some embodiments. 
         FIG. 3  illustrates a top-down front left perspective view of the solder dross recovery module according to some embodiments. 
         FIG. 4  illustrates the same view of the solder dross recovery module of  FIG. 2  with the cover removed. 
         FIG. 5  illustrates a top-down back right perspective view of the solder dross recovery module according to some embodiments. 
         FIG. 6  illustrates the same view of the solder dross recovery module of  FIG. 5  with a side wall removed. 
         FIG. 7  illustrates a back left side view of the solder dross recovery module with two side walls removed. 
         FIG. 8  illustrates a left side view of the solder dross recovery module with a side wall removed. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present application are directed to a solder dross recovery module. Those of ordinary skill in the art will realize that the following detailed description of the solder dross recovery module is illustrative only and is not intended to be in any way limiting. Other embodiments of the solder dross recovery module will readily suggest themselves to such skilled persons having the benefit of this disclosure. 
     Reference will now be made in detail to implementations of the solder dross recovery module as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts. In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer&#39;s specific goals, such as compliance with application and business related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure. 
       FIG. 1  illustrates a solder dross recovery system according to some embodiments. The solder dross recovery system includes a solder pot for maintaining and containing molten solder and a solder dross recovery module. In some embodiments, the solder pot is included as part of a wave soldering apparatus. In general, the solder pot can be part of any apparatus that requires maintaining and containing molten solder. In the exemplary configuration shown in  FIG. 1 , the solder dross recovery system includes a wave soldering apparatus  2  and a solder dross recovery module  10 . The wave soldering apparatus  2  includes a solder pump  4 , a wave nozzle  6  and a solder pot  8 . The solder pot  8  includes a heater (not shown) for maintaining solder in a molten state. The solder pump  4  pumps molten solder up through the wave nozzle  6  forming a wave of molten solder. The solder pot  8  includes a bottom wall and side walls for containing the molten solder. The molten solder is exposed to the environment at the top surface. 
     The solder dross recovery module  10  includes a mounting structure and is mounted to a side wall edge  16  of one of the side walls  14 . In some embodiments, the mounting structure includes a U-clamp  26  configured to fit over and rest on the side wall edge  16 . The U-clamp  26  is secured to the side wall  14  by locking knobs  28  ( FIG. 2 ). A portion of the solder dross recovery module  10  is suspended within the solder pot  8  and submerged in the molten solder. The solder dross recovery module  10  also includes a motor  18  which is suspended outside the solder pot  8 . The motor  18  is controlled by a coupled controller and motor driver unit  12 . In some embodiments, the motor  18  is covered or partially covered by a thermal insulating material so as to thermally insulate the motor  18  from the high temperature of the molten solder. 
       FIG. 2  illustrates a top-down front right perspective view of the solder dross recovery module  10  according to some embodiments.  FIG. 3  illustrates a top-down front left perspective view of the solder dross recovery module  10  according to some embodiments. The solder dross recovery module  10  includes a waste collector  32  and a cover  34  movably coupled to a top wall  36  via a hinge  56 .  FIG. 4  illustrates the same view of the solder dross recovery module  10  of  FIG. 2  with the cover  34  removed. The solder dross recovery module  10  includes gears  46 ,  48  and  50 . In some embodiments, the gears  46 ,  48 ,  50  are each spur gears interconnected such that rotating the gear  50  translates to rotating the gears  46  and  48 , as shown in  FIG. 8 . The gears  46 ,  48  are coupled at either end to side walls  38  and  40 . A wall  42  extends between the side walls  38 ,  40 . The gear  50  is connected to a first end of a cam shaft  24 . A gear  22  is connected to a second end of the cam shaft  24 . A gear  20  is coupled to the motor  18 . In some embodiments, the gears  20  and  22  are each miter gears interconnected such that rotating the gear  20  translates to rotating the gear  22 , which in turn rotates the cam shaft  24  which rotates the gear  50 . The gear  20  is driven by the motor  18 . The gear  20  can be rotated in either the clockwise or counter-clockwise direction depending on control signaling supplied by the controller and motor drive unit  12 . 
       FIG. 5  illustrates a top-down back right perspective view of the solder dross recovery module  10  according to some embodiments. A side wall  44  covers the gear  50  and partially covers the gear  48 , but leaves exposed the gear  46 .  FIG. 6  illustrates the same view of the solder dross recovery module  10  of  FIG. 5  with the side wall  44  removed. As shown in  FIGS. 5 and 6 , there is no bottom wall connecting the bottoms of side walls  38  and  40 , and as such the underside of gear  46  is left exposed. 
       FIG. 7  illustrates a back left side view of the solder dross recovery module  10  with the side wall  40  and the side wall  44  removed. The wall  42  does not extend to contact the cover  34 . A waste entrance  52  is an opening formed between the top edge of the wall  42  and the cover  34 . 
       FIG. 8  illustrates a left side view of the solder dross recovery module  10  with the side wall  40  removed. The solder dross recovery module  10  is mounted to the side wall  14  ( FIG. 1 ) of the solder pot  8  such that the waste collector  32 , side walls  38 ,  40 , the wall  42  and the gears  46 ,  48  are partially submerged in the molten solder. In the exemplary configuration shown in  FIG. 8 , the solder dross recovery module  10  is positioned with a solder level  54 . Solder level  54  is substantially aligned with the mesh point of the gears  46 ,  48  and at a level lower than the waste entrance  52  such that molten solder does not pass over the top edge of the wall  42  and enter the waste collector  32 . The position of the solder dross recovery module  10  relative to the molten solder lever can be adjusted up or down by adjusting the height adjustment mechanism  30  ( FIG. 2 ), thereby adjusting the solder level  54 . In some embodiments, the solder dross recovery module  10  is configured such that the side wall  38  rests against the inner surface of the side wall  14  ( FIG. 1 ) when the solder dross recovery module  10  is mounted to the side wall  14 . 
     In operation, the motor  18  drives the gear  20  which rotates the gear  22 , the cam shaft  24  and the gear  50 . Rotating the gear  20  clockwise results in clockwise rotation of the gear  50 . Clockwise rotation of the gear  50  translates to counter-clockwise rotation of the gear  48  and clockwise rotation of the gear  46 . Counter-clockwise-rotation of the gear  48  and clockwise rotation of the gear  46  draws molten solder from outside the solder dross recovery module  10  toward the gears  46 ,  48 . As applied to  FIG. 8  molten solder is drawn from left of the gears  46 ,  48  toward the gears, in other words from left to right. This is referred to as forward rotation of the gears. Rotating the gears in the opposite directions, such that the gear  48  rotates clockwise and the gear  46  rotates counter-clockwise, is referred to as backward rotation of the gears. Solder dross forms on the surface of the molten solder, for example solder dross is present starting from the solder level  54  ( FIG. 8 ) upward. As molten solder is drawn to the gears  46 ,  48  rotating in the forward direction, so too is the solder dross floating on the surface of the molten solder. The gears  46 ,  48  apply pressure to the solder dross, such as by squeezing, thereby separating solder from the solder dross, leaving behind a waste material. The separated solder falls into the molten solder within the space enclosed by the side walls  38 ,  40  and wall  42 . As the gears  46 ,  48  continue to rotate, the waste material collects behind the gears  46 ,  48  in the space enclosed by the side walls  38 ,  40 , the wall  42 , and the cover  34  and floats above the solder level  54 . The waste material is eventually pushed through the waste entrance  52  into the waste collector  32 . 
     In some embodiments, a sensor (not shown) is positioned in the waste collector  32  to indicate when the waste collector  32  is full of waste material and needs to be emptied. In some embodiments, the waste collector  32  includes a removable container that can be removed from the remainder of the solder dross recovery module  10 . This enables emptying of the waste collector  32  without having to dismount the entire solder dross recovery module  10  from the solder pot  8 . The waste collector  32  and the removable container are accessible by raising the cover  34 . 
     The motor  18  can be controlled by the controller and motor drive unit  12  to turn the gears according to various patterns and/or speeds. For example, the motor  18  can turn the gears at a constant rate of speed and in a continuous forward direction. In another example, the gears can be rotated forward for a set period, such as 5 steps of the motor, and then rotated backwards for another set period, such as 4 steps of the motor, and then repeat. Changing the rotation forward and backward cycles portions of the solder dross back and forth through the gears  46 ,  48 , thereby increasing a duration during which pressure is applied to the solder dross by the gears  46 ,  48 . 
     The solder dross recovery module and its implementation with a solder pot provides numerous advantages. There is no need for centralized off-line equipment required for different alloys, which reduces handling and equipment cost. The solder dross recovery module is smaller and much less expensive than a separate off-line device. There is no need to re-heat collected solder dross as in a separate off-line device since the solder dross is processed within the solder pot. This process removes the need to track the type of solder recovered and avoids possible solder type mix up. There is no need for additional chemicals, which reduces indirect material consumption. There is no need for operators to remove solder dross from the solder pot to different area for solder dross recovery. Performing the solder dross recovery in the solder pot reduces maintenance to the solder pot. The solder dross recovery module requires less maintenance than a separate off-line device, simply replace low cost spur gears when worn out. 
     The present application has been described in terms of specific embodiments incorporating details to facilitate the understanding of the principles of construction and operation of the solder dross recovery module. Many of the components shown and described in the various figures can be interchanged to achieve the results necessary, and this description should be read to encompass such interchange as well. As such, references herein to specific embodiments and details thereof are not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modifications can be made to the embodiments chosen for illustration without departing from the spirit and scope of the application.