Abstract:
A system for solder processing includes a heating zone at a first pressure; a cooling zone at a second pressure higher than the first pressure, the heating and cooling zones in communication with each other and adapted for receiving a component to be soldered; and an outlet in communication with the heating zone for exhausting atmosphere from the heating zone and enabling a flow of gas from the cooling zone to the heating zone.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to methods and apparatus for treating objects and other work pieces with solder.  
         [0002]     It is known in the industry to use separate and discrete processing chambers with variable atmospheres for heating and/or cooling of the components or parts that are to be soldered treated. The application of a vacuum during the processing in known systems can be useful during the heating or melting stage since such a vacuum substantially reduces, if not eliminates, voids which may form during the soldering process. It is known that drawing a vacuum during the cooling stage of the solder processing does not impact as much the actual processing of the solder.  
         [0003]     Known systems rely upon the processing environment or chambers to be “sealed from the environment”, that is, sealed off from an environment external to the processing chambers where the effect of heating and cooling is undertaken on the component to be processed with solder.  
         [0004]     Hydrogen (H 2 ) vacuum soldering is known and known systems employ separate, discrete chambers (with independent atmospheres) for heating and cooling of the parts to be soldered; in effect using separate atmospheres for heating and cooling. While providing a vacuum is generally useful during the heating or melting stage of the process, as such heating/melting reduces the number of voids formed during soldering, a vacuum is not as necessary during cooling and in fact provides little benefit.  
         [0005]     Accordingly, the known systems require an extensive infrastructure in order to affect solder processing; in that the known systems rely upon separate and discrete processing chambers restricted from communication with each other for affecting the solder environment in which solder processing of a component may be undertaken.  
     
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0006]     For a more complete understanding of the present invention, reference may be had to the following drawings taken in conjunction with the detailed description, of which:  
         [0007]      FIG. 1  shows an embodiment of the solder process system of the invention; and  
         [0008]      FIG. 2  shows another embodiment of the solder process system of the invention. 
     
    
     DESCRIPTION OF THE INVENTION  
       [0009]     As shown in  FIG. 1 , the solder process system of the present invention is generally indicated at  10  and includes housing  12  having a heating/melting zone  14  and a cooling zone  16 . A system  11  at  FIG. 2  shows the heating zone  14  divided into a preheat zone  14   a  and a melting zone  14   b . The heating/melting zone  14  may be referred to herein as the heating zone  14 .  
         [0010]     Each of the heating/melting zone  14  and the cooling zone  16  may be provided in a corresponding one of the heating chamber  18  ( 18   a ,  18   b ), and cooling chamber  20 , respectively, for the atmosphere employed in that particular chamber.  
         [0011]     As shown in  FIG. 1 , a conduit  22  with a passage is in communication with the heating chamber  18  and hence the heating zone  14 . A conduit  24  with a passage is in communication with the cooling chamber  20  and hence the cooling zone  16  for providing hydrogen, nitrogen (N 2 ) or combinations thereof, thereto. The chambers  18 ,  20  are segregated from the external environment by the housing  12  and movable doors  26 ,  28 .  
         [0012]     The conduit  22  may include a pump  23  or pump and valve assembly to be actuated in order to promote heating in said zone for processing of the component with solder. The conduits  22 ,  24  regulate the gas flow to and from the chambers  18 ,  20 , and the gas flow can be controlled by butterfly or other valving means.  
         [0013]     There is also provided a wall  32  or baffle disposed in the housing  12  to separate the heating and cooling chambers  18 ,  20 , respectively. The wall  32  is constructed with a valve  30  or other flow or pressure regulator means in the wall. Door  27  is formed at the wall  32  to enable the component to be moved between the chambers  14 ,  16 . The valve  30  enables communication between the chambers  18 ,  20 . The doors  26 ,  27 ,  28  permit movement of the solder component through the apparatus  10 .  
         [0014]     A pressure “P 2 ” of the cooling zone  16  is preferably greater then a pressure “P 1 ” of the heating zone. By way of example and not by way of limitation, P 1  may be less than or equal to 760 Torr.  
         [0015]     Operation of the system includes opening the conduit  22  a sufficient amount during processing to facilitate drawing down of the atmosphere to a vacuum in the heating zone  14  to facilitate environmental conditions for heat processing of the solder to the component. Similarly, ingress of the gas at the conduit  24  into the cooling zone  16  is permitted to subsequently flow, as indicated by the arrow  34 , through the regulator valve  30  or valve means into the heating zone  14  where it may subsequently be withdrawn through the conduit  22 . Such a construction and arrangement of the components of the system  10  of the present invention provides for a uniform controlled flow of gas from one zone to another zone, i.e. from the cooling zone  16  as indicated by the arrow  34  through to the heating zone  14 , whereupon it can flow or be exhausted to the external atmosphere. In effect, the heating and cooling chambers  18 ,  20  are permitted to be in controlled communication with each other and the atmosphere external to the housing  12 .  
         [0016]     The construction of this embodiment of the present invention is cost effective, in that there is only one exhaust pump which may be required for one of the chambers, as opposed to a plurality of pumps being in communication with each of the chambers. In addition, cooling is more cost effective by providing the cooling gas (hydrogen, nitrogen or combinations thereof) at a higher pressure in the cooling zone  16  to provide a more thorough and quick cooling process for control thereof. In addition, the higher pressure P 2  causes the cooling gas to move though the valve  30  with no complicated mechanical activity.  
         [0017]     Operation of the system can be strictly controlled regarding the amount of exhaust at the conduit  22  and the flow setting or restriction of the valve  30  between the two chambers  18 ,  20 , in order to selectively manipulate both the pressures P 1 , P 2  and the temperature at the heating chamber  18 .  
         [0018]     Another reason for the higher pressure P 2  in the cooling zone  16  is to substantially reduce if not eliminate any introduction of evaporated flux from the melt zone  14  into the cooling zone  16  where detrimental effects, such as flux condensation on the component, could occur with respect to the soldered component and thereby reduce the effectiveness of cooling in the cooling chamber  20 . To further this, the valve  30  is preferably a one-way valve. The valve  30  may also be two-way, but controllable with respect to the direction of flow required between the chambers  18 ,  20 .  
         [0019]     Another embodiment of the present invention is shown generally at  11  in  FIG. 2 , and includes at least three (3) chambers, wherein the heating zone  14  would be segregated into a preheat zone  14   a  (preheat chamber  18   a ) and a melt zone  14   b  (melt chamber  18   b ). In such construction, where the system  11  has both the preheat zone  14   a  and the melt zone  14   b , it is preferred to have a respective pump in communication with a respective one of the preheat and melt chambers as shown in  FIG. 2 .  
         [0020]     Referring to  FIG. 2 , a pipe  36  is in communication with the preheat zone  14   a . The pipe  36  includes a valve  38  and pump  40  in communication to coact with the pipe  36 . The pipe  36  provides for communication between and among the chamber  14   a  and an external atmosphere.  
         [0021]     A pipe  42  is in communication with the melt chamber  14   b  to provide for communication between the chamber  14   b  and the external atmosphere. A valve  44  and pump  46  are in communication with the pipe  42  for coaction therewith.  
         [0022]     There is also provided a wall  48  or baffle disposed in the housing  12  to separate the pre-heat chamber  14   a  from the melt chamber  14   b . A valve  50  or flow regulator means is disposed in the wall  48  to control the flow of the atmosphere between and among the chambers  18   a ,  18   b . Door  29  is provided at the wall  48  to enable the component to move between the chambers  14   a ,  14   b.    
         [0023]     A wall  52  is disposed in the housing  12  to separate the melt chamber  14   b  from the cooling zone  16  of the cooling chamber  20 . A valve  54  or flow regulating means is disposed in the wall  52  to control communication between and among the chambers  18   b ,  20 , to thereby control the flow of the atmosphere between and among said zones  14   b ,  16 . Door  31  is provided at the wall  52  to enable the component to move between the chambers  18   b ,  20 .  
         [0024]     The doors  26 ,  28  control ingress and egress of the components into and out of the apparatus  11  and seal the apparatus  11  from the external environment.  
         [0025]     A source  56  of hydrogen, nitrogen or combination thereof, is provided to the cooling chamber  20  via pipe  58  to the cooling zone  16 . Pump  60  is provided at the pipe  58  or conduit to transfer the gas from the source  56  to the chamber  20 .  
         [0026]     The embodiment of  FIG. 2  prevents flux that has melted or evaporated in the melt zone  14   b  from ingress into the preheat zone  14   a , and similarly prevents vapors from the flux melt into the preheat zone  14   a . The wall or baffle  48  separating the preheat zone  14   a  from the zone  14   b  is not necessarily as critical as the wall  52  that is provided separating the heating zone  14   b  from the cooling zone  16 . The wall  52  and valve  54 , in combination with the higher pressure P 2  at the cooling chamber  20 , prevents unwanted vapors and flux particulate from escaping from the heat zone  14  ( 14   a ,  14   b ) to the cooling zone  16 .  
         [0027]     Pressure P 2  is greater that pressure P 1 . Pressure P 1  is greater that pressure P 1 ′. Other cooling gases from the sources  24 ,  56  may be used as necessary. Arrow  62  in  FIG. 2  shows gas flow at the cooling zone  16 . Arrow  64  in  FIG. 2  shows a flow of the cooling gas originating from the source  56  transiting through the zone  14   b . Arrow  66  shows gas flow at the chamber  14   a  to the conduit  36 . Filters (not shown) may also be disposed in the valves  30 ,  50 ,  54 , to remove unwanted matter from the air flow through said valves.  
         [0028]     In summary, with a dual chamber system such as in  FIG. 1 , only one exhaust pump is necessary in communication with the melt zone; while in the system of  FIG. 2  employing a melt chamber with a preheat chamber it is preferred to have an exhaust pump in communication with each of the respective preheat and melt chambers.  
         [0029]     It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as defined in the appended claims. The embodiments described above are not only in the alternative, but can be combined.