Patent Publication Number: US-2010128445-A1

Title: Clamp for mounting semiconductor laser bar chips and method of mounting chips

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims priority of Chinese Patent Application No. 200810217706.8, filed on Nov. 26, 2008, the disclosure of which is incorporated herein in its entirety by reference. 
     FIELD OF THE INVENTION 
     The present disclosure generally relatives to clamps and methods of mounting chips using the clamps and, particulary, to a clamp for mounting semiconductor laser bar chips and a method of mounting the chips. 
     BACKGROUND OF THE INVENTION 
     In the semiconductor photoelectricity field, manufacturing technology of semiconductor laser bar products is a basis of applying semiconductor larer bar products. Particularly, mounting technology of mounting a semiconductor laser bar chip and a heat sink together is one of the critical technologies. Generally, high power semiconductor laser bar chips are mounted by P-side mounting method. The reason is that the P-side of the chip should be mounted to a heat sink capable of dispersing heat quickly, because the high power semiconductor laser bar chip produces a mount of heat during working and the heat source is closed to the P-side of the chip. As such, the heat sink not only disperses heat, but also acts as a P-electrode. The semiconductor laser bar chip and the heat sink are generally soldered together using a medium of metallic solder metarial, so that heat and electricity can be conducted efficiently therebetween and the semiconductor laser bar chip and the heat sink are firmly connected. A surface, to be contacted with a P-side of the chip, of the heat sink is plated with metallic solder material with the in advance, and then the semiconductor laser bar chip and the heat sink are mounted together by solder. Methods for mounting a N-side of the chips includes various of manners, for example, adopting gold wires as electrodes or a manner similar to the P-side mounting method described above. Using the latter method, i.e., the manner similar to the P-side mounting method, to mounting the N-side can disperse heat efficiently. It can be understood that, to mount the heat sink (also used as P-electrode), the chip, and a N-electrode simultaneity is most difficult. 
     There are two methods to position and mount the semiconductor laser arry chip and the heat sink together. Referring to  FIG. 6 , one is adopting a mounting system including a chip position controller  111  configured to adjust a position of a chip  11 , a heat sink position controller  121  configured to adjust a position of a heat sink  12 , and a high magnification video system  131  having a microscope unit  13 . The chip  11  and the heat sink  12  are arranged below the microscope unit  13 . The microscope unit  13  scans edges of the chip  11  and the heat sink  12 , and the high magnification video system  131  calculates the chip  11  and the heat sink  12  being in desired positions or not. However, precise chip position controller  111  and precise heat sink position controller  121  are needed, thus resulting in a high cost. In addition, a precision of positioning the chip  11  relative to the heat sink  12  is determined by the high magnification video system  131  that has a precision of several microns. Furthermore, a mounting efficiency is low. Referring to  FIG. 7 , the other one is adopting a mounting system including a chip position controller  211  configured to adjust a position of a chip  21 , a heat sink position controller  221  configured to adjust a position of a heat sink  22 , and an optical scanning system  231  having a scanning unit  23 . The chip  21  and the heat sink  22  are arranged at a side of the scanning unit  23 . However, precise chip position controller  211 , precise heat sink position controller  221 , and expensive optical scanning system  231  are needed, thus resulting in a high cost. In addition, a mounting efficiency is low. To mount the heat sink (also used as P-electrode), the chip, and the N-electrode together simultaneily with the above-described two methods is difficult. 
     Therefore, a new clamp for mounting semiconductor laser bar chips and a new method of mounting chips are desired to overcome the above-described shortcomings. 
     SUMMARY OF THE INVENTION 
     A clamp for mounting chips comprises a base, a limiting member, a positioning assembly, and a pressing assembly. The base defines a gap. The limiting member is fixed on the base, and defines a limiting slot corresponding to the gap. The limiting member has a first side and a second side opposite to the first side. The positioning assembly is positioned at the first side of the limiting member. The positioning assembly comprises a positioning handle and a pushing member. The pushing member extends in the limiting slot, and the positioning handle runs through the limiting member and is connected to the pushing member. The pressing assembly is positioned at the second side of the limiting member. The pressing assembly runs through the limiting member and extends in the limiting slot. A chip is capable of being pushed to the position of the gap by the pushing member with operating the positioning handle and resists against the pressing assembly, thus being clamped. 
     A method of mounting chips is provide. A heat sink and a N-electrode are to be mounted on opposite sides of a chip. The chip has a P-side, a N-side, and a light-outgoing surface, the heat sink, the chip. The N-electrode are mounted together by a clamp comprising a base defining a gap, a limiting member defining a limiting slot corresponding to the gap, a pressing assembly, and a positioning assembly. The positioning assembly and the pressing assembly are positioned at opposited sides of the limiting member. The method comprising: (1) the heat sink plated with solder material is put in a limiting slot of the limiting member mounted on the base, and put on a surface of the base, the positioning handle of the positioning assembly is pushed to slide the pushing member, thus pushing the heat sink to a position in range of ¼˜¾ portion of a gap of the base and positioning the heat sink; (2) a clamp is slanted through an angle, so that the pressing assembly is on the top side and a plated surface of the heat sink faces the upside, the chip is put in the limiting slot with the P-side of the chip acing a plated film of the heat sink, the chip slides towards the base due to the gravity of the chip, a light-outgoing portion of the light-outgoing surface of the chip is positioned above the gap, and a portion of the light-outgoing surface of the chip which is adjacent to the N-side of the chip is attached at an edge of the gap, the slanted angle of the clamp is in a range of 30˜60 degrees; (3) with a plated surface facing the N-side of the chip, the N-electrode is put on the base; and (4) the N-electrode is pushed towards the N-side of the chip by pushing the pressing assembly, thus clamping the N-electrode, the chip, and the heat sink resisting the positioning assembly together. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The componets in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout several views, and all the views are schematic. 
         FIG. 1  is an assembled, isometric view of an embodiment of a clamp for mounting semiconductor laser bar chips of of the present disclosure. 
         FIG. 2  is an assembled, isometric view showing the clamp of  FIG. 1 , showing a heat sink, a chip, and a N-electrode put on the clamp. 
         FIG. 3  is an assembled, isometric view showing the clamp of  FIG. 2 , showing the heat sink, the chip, and the N-electrode clamped by the clamp. 
         FIG. 4  is a cross-sectional view of  FIG. 3  taken along line IV-IV. 
         FIG. 5  is a flow chart showing an embodiment of a method for mounting semiconductor laser bar chips of the present disclosure. 
         FIG. 6  is a first typical mounting system. 
         FIG. 7  is a second typical mounting system. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , an embodiment of a clamp for mounting semiconductor laser bar chips of of the present disclosure is shown. The clamp (not labeled) includes a positioning assembly  4 , a limiting member  5 , a pressing assembly  6 , and a base  7 . The clamp is used to mount a heat sink  1 , a chip  2 , and a N-electrode  3  together. The chip  2  may be a semicondutor laser bar chip. The positioning assembly  4  and the pressing assembly  6  are positioned at opposite ends of the base  7 , and the limiting member  5  is located on the base  7 . 
     The base  7  is substantially a sheet including a smooth top surface (not labeled). The base  7  defines a gap  71  with a width corresponding to a thickness of the chip  2  to be mounted. The gap  71  is defined in the top surface. The heat sink  1 , the chip  2 , and the N-electrode  3  may be precisely aligned to each other when positioned on the base  7 , because the top surface of the base  7  is smooth. 
     The limiting member  5  is positioned on the top surface of the base  7 . The limiting member  5  and the base  7  may be fixed by screws or by pasting. The limiting member  5  is substantially a sheet defining a limiting slot  51 . The gap  71  of the base  7  corresponds to the limiting slot  51  so that the gap  71  is exposed via the limiting slot  51 . 
     The positioning assembly  4  includes a positioning handle  41  and a pushing member  42  connected to the positioning handle  41 . The pushing member  42  extends in the limiting slot  51 . Part of the positioning handle  41  runs through the limiting member  5  and connected to the positioning handle  41 . The limiting member  5  defines a threaded hole. The positioning handle  41  is a helical screw. The positioning handle  41  runs through and engage with the threaded hole of the limiting member  5 , and then being connected to the pushing member  42 . The engagement of the positioning handle  41  and the threaded hole of the limiting member  5  makes the positioning assembly  4  can move when the positioning handle  41  is rotated. The pushing member  42  is a pushing block for facilitating to be pushed and has a large contacting area for contacting with the heat sink  1 . Part of the positioning handle  41  is outside the limiting member  5  and at least part of the pushing member  42  capable of extending in the limiting slot  51  of the limiting member  5 . 
     The pressing assembly  6  runs through the limiting member  5  and extends in the limiting slot  51 . The chip  2  can be pushed to the position of the gap  71  by the pushing member  42  with operating the positioning handle  41  and resists against the pressing assembly  6 , thus being clamped. 
     Referring to  FIGS. 2 through 4 , the pressing assembly  6  forms a bulgy protrusion  61  at an end of the pressing assembly  6  that protrudes into the limiting slot  51 . In use, the protrusion  61  may be configured to resist and press the N electrode  3 . The pressing assembly  6  may further include an elastic member  62 . In the illustrated embodiment, the elastic member  62  is a compression spring sleeved on the pressing assembly  6 . Alternatively, the elastic member  62  may be other components that is changeable in length. The elastic member  62  provides a push force among the heat sink  1 , the chip  2 , and the N-electrode  3  during a process of eutectics soldering, so that the heat sink  1 , the chip  2  and the N-electrode  3  can be mounted together better. The pressing assembly  6  may further include a handspike  64  extending outside the limiting member  5 . A limiting pin  63  is mounted on the handspike  64 . The limiting member  5  further defines a guiding slot  53 . When the handspike  64  is pushed towards the limiting slot  51  of the limiting member  5 , the limiting pin  63  is engaged in the guiding slot  53 , such that the pressing assembly  6  can not deflect during pressing. Alternatively, the pressing assembly  6  may be connected to the limiting member  5  via a crossbeam  9 . That is, the elastic member  62  and the handspike  64  run through the crossbeam  9  before connected to the limiting member  5 . The crossbeam  9  may be connected to the limiting member  5  via bolts or screws. 
     The limiting member  5  defines a pair of engaging slots  52  (see  FIG. 3 ) that are opposite to each other. Opposite ends of a block  8  is positioned in the engaging slots  52 , such that the block  8  traverses the limiting slot  51 . The protrusion  61  of the pressing assembly  6  is to resist the block  8 . Before mounting the heat sink  1 , the chip  2  and the N-electrode  3  together, the block  8  resists the pressing assembly  6 . After the the heat sink  1 , the chip  2  and the N-electrode  3  are put in place, the block  8  is taken away to allow the pressing assembly  6  pressing the heat sink  1 , the chip  2 , and the N-electrode  3 . 
     In alternative embodiments, the base  7 , the limiting member  5 , and the crossbeam  9  may be integrally formed to form an integral member. In this case, a bottom portion of the integral member defines the gap  71 , and a top portion of the integral member defines the limiting slot  51 . 
     The present disclosure also provides a method of mounting chips. The heat sink  1  and the N-electrode  3  need to be mounted on opposite sides of the chip  2 . The chip  2  includes a P-side, a N-side, and a light-outgoing surface. The method includes the following steps.
     (1) The heat sink  1  plated with solder material is put in the limiting slot  51  of the limiting member  5  and on the top surface of the base  7 . The positioning handle  41  of the positioning assembly  4  is pushed to slide the pushing member  42 , thus pushing the heat sink  1  to the one second portion (½) of the gap  71  of the base  7  and positioning the heat sink  1 . Alternatively, the heat sink  1  may be pushed to the one fourth to three fourth (¼˜¾) portion of the gap  71 ;   (2) The clamp is slanted through 45 degrees, so that the pressing assembly  6  is on the top side and a plated surface of the heat sink  1  faces the upside. The chip  2  is put in the limiting slot  51  with the P-side of the chip  2  facing a plated film of the heat sink  1 . The chip  2  slides towards the base  7  due to the gravity of the chip  2 . A light-outgoing portion of the light-outgoing surface of the chip  2  is positioned above the gap  71 , and a portion of the light-outgoing surface of the chip  2  which is adjacent to the N-side of the chip  2  is positioned on the base  7  and at an edge of the gap  71 . In alternative embodiment, the clamp may be slanted through 30˜60 degrees;   (3) With a plated surface facing the N-side of the chip  2 , the N-electrode  3  is put on the base  7 ;   (4) The N-electrode  3  is pushed towards the N-side of the chip  2  by pushing the pressing assembly  6 , thus clamping the N-electrode  3 , the chip  2 , and the heat sink  1  resisting the positioning assembly  4  together.   

     A flow chart of the mounting method is shown in  FIG. 5 . The flow of the mounting method includes the steps of cleaning the clamp, plating a plated film on the heat sink  1 , plating a plated film on the N-electrode  3 , positioning the heat sink  1 , positioning the chip  2 , positioning the N-electrode  3  or a bumper, clamping the heat sink  1 , the chip  2 , and the N-electrode  3 , eutectics soldering, unloading, and testing. 
     The mounting method and a process of using the clamp are detailed below. 
     In the step of cleaning the clamp, the clamp is put in an organic solvent such as acetone, isopropylcarbinol, or alcohol, and then cleaned by ultrasonic. After cleaned clean, the clamp is blowed to dry by a nitrogen gun. 
     In the step of plating a plated film on the heat sink  1 , solder material is plated on a surface to be mounted and soldered by sputtering method or evaporating method. In a prefered embodiment, the solder material may be high purity indium. A thickness of the plated film is in a range of 5˜10 microns. 
     In the step of plating a plated film on the N-electrode  3 , solder material is plated on a surface to be mounted and soldered, by sputtering method or evaporating method. If the N-side of the chip  2  not need to be mounted, this step may be omitted. The solder material may be high purity indium, and a thickness of the plated film is in range of 5˜10 microns. 
     In the step of positioning the heat sink  1 , as shown in  FIG. 2  and  FIG. 3 , the heat sink I with the plated film is put on the top surface of the base  7  and stands against a front wall of the pushing member  42 . The positioning handle  41  is rotated to push the heat sink  1 , thus making a bottom edge of the plated film of the heat sink I to be positioned on the ½ portion (or any portion in a range of ¼˜¾) of the gap  71  of the base  7 . 
     In the step of positioning the chip  2 , as shown in  FIG. 2  through  FIG. 4 , the clamp is slanted through 45 degrees (or any angle in a range of 30˜60 degrees) so that the pressing assembly  6  is at the top side and the plated film of the heat sink  1  faces the upside. The chip  2  is lightly put on the plated film of the heat sink  1  by a vacuum absorbing device with the P-side of the chip  2  facing the plated film of the heat sink  1  and the light-outgoing surface facing the underside, i.e., facing the gap  71 . The chip  2  slides towards the base  7  for the gravity of the chip  2 . The light-outgoing portion of the light-outgoing surface of the chip  2  is positioned above the gap  71 , and no gap is between the chip  2  and the top surface of the base  7 . Referring to  FIG. 4 , the light-outgoing portion of the light-outgoing surface of the chip  2  corresponds to the gap  71  without contacting anything, and a part of the light-outgoing surface of the chip  2 , which is adjacent to the N-side of the chip  2  is attached at an edge of the gap  71  of the base  7 . General chips  2  in the market usually have a thickness in a range of 0.12˜0.15 millimeters, and a distance between a light-outgoing opening and the P-side of the general chips  2  is usually equal to or less than 0.05 millimeters. Therefore, the structure of the clamp and the mounting method can ensure that the light-outgoing portion exactly corresponds to the gap  71  and contacts nothing. 
     In the step of positioning the N-electrode or the bumper, referring to  FIG. 2  through  FIG. 4 , the N-electrode  3  with plated film is put on the base  7 , with the plated surface facing the chip  2 . The plated surface of the N-electrode  3  stands against the N-side of the chip  2 . The the chip  2  and the N-electrode  3  are perpendicular to the base  7 , such that the sidewalls of chip  2  and the N-electrode  3  fully contact with the top surface of the base  7 . 
     In the step of clamping the heat sink  1 , the chip  2 , and the N-electrode  3 , referring to  FIG. 3  and  FIG. 4 , the block  8  is removed to make the protrusion  61  of the pressing assembly  6  resisting the N-electrode  3 . In some cases, if the N-electrode  3  not need to be mounted, the N-electrode  3  may be instead by a N-electrode not plated with solder material called as a bumper. A force applied to the heat sink  1 , the chip  2 , and the N-electrode  3  (or the bumper), which is from the pressing assembly  6 , is in a range of 100˜300 grams. 
     In the step of eutectics soldering, the clamp clamping the heat sink  1 , the chip  2 , and the N-electrode  3  (or the bumper) is put in a vacuum eutectics soldering oven to be soldered with high temperature. The plated films, i.e., the solder material, of the heat sink  1 , and the N-electrode  3  are melted under the high temperature. Then, the plated films consolidate when the temperature is lowered, thus firmly mounting the heat sink  1 , the chip  2 , and the N-electrode  3 . In the process of eutectics soldering, the temperature is preferred to 160˜210 degrees centigrade, and the preferred temperature is kept for more than three minutes. A plurality of clamps may be put in the vacuum eutectics soldering oven and soldered simultaneity, to improve the manufacturing efficiency. 
     In the step of unloading, the clamp is taken out of the vacuum eutectics soldering oven. The handspike  64  of the pressing assembly  6  is pulled out of the limiting slot  51  and the block  8  is inserted into the engaging slots  52 . The front end of the protrusion  61  of the pressing assembly  6  resists the block  8 . Thus, the heat sink  1 , the chip  2 , and the N-electrode  3  may be taken out from the clamp. 
     In the step of testing, an aspect of the heat sink  1 , the chip  2 , and the N-electrode  3  mounted together is all-around tested by optical testing, and photoelectric performances of the heat sink  1 , the chip  2 , and the N-electrode  3  mounted together are tested by compositive testing. As such, the flow for mounting the heat sink  1 , the chip  2  and the N-electrode  3  is completed. 
     Using the clamp and the method of mounting chips of the present disclosure, the heat sink  1 , the chip  2  and the N-electrode  3  can be easily mounted together simultaneity, just by rotating the positioning handle  41  to push the pushing member  42 . The process is quite simple and has low cost. Mounting the heat sink  1 , the chip  2  and the N-electrode  3  together can be performed in mass manufacturing, and a manufacturing efficiency is improved. 
     Finally, while various embodiments have been described and illustrated, the disclosure is not to be construed as being limited thereto. Various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the disclosure as defined by the appended claims.