Patent Publication Number: US-2010124023-A1

Title: Method for plating film on a heat dissipation module

Description:
This application claims the benefit of the Taiwan Patent Application Serial NO. 097144838, filed on Nov. 20, 2008, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fabrication technology for a heat dissipation module, more particularly to a method for plating films on an external surface of the heat dissipation module and a film-plated heat dissipation module. 
     2. Description of the Prior Art 
     In our daily life, several of the electronic devices include a plurality of electronic elements, such as LED (light emitting diode) or a CPU (central processing unit). Operation of these electronic elements generally results in heat. Under certain condition, the heat generated thereby may affect the proper function of the electronic device, like reduction in the carrying load, shortening the service life, lowering the operation speed and effect thereof. 
     In order to dissipate the heat, a heat dissipation module is mounted intentionally adjacent to the heat-generating source in the electronic device. Two facts, namely the structure and the material, are taken for consideration in the presently available heat dissipation module. As far as the material is concern, conductive material is preferred for enhancing the heat dissipating effect. For the structure, the external surface area of the heat dissipation is increased as much as possible for heat exchanging operation. A conventional heat dissipation module generally includes a dissipating base and a plurality of fins extending from the dissipating base, thereby increasing the total surface area for enhancing the heat exchanging operation. 
     In addition, in order to enhance the heat dissipating effect, the external surfaces of the base or the fins are generally heat-treated so that the external surfaces are formed with recesses, protrusions, wrinkled portions or densely located grain-like projections. Regarding the aforesaid comments, a known structure and method is given in the following paragraphs for fabricating a heat dissipation module. 
       FIG. 1  shows a conventional heat dissipation module  1  to include a dissipating base  11  and a plurality of dissipating fins  12 . The base  11  has a main layer  111  and an external layer  112 , wherein the main layer  111  has a mounting surface  111   a  for disposing on a support ground and a dissipating surface  111   b  for dissipating the heat therefrom. The external layer  112  is disposed on and thus encloses the dissipating surface  111   b  of the main layer  111  from above. Each fin  12  has a base layer  121  integrally formed with the main layer  111  of the base  11 , and an external layer  122  enclosing the base layer  121  from above. A function element  2  is disposed below the mounting surface  111   a  of the main layer  111  and generates heat upon operation. A portion of the generated heat is transferred from the main layer  111 ,  121  to the external layer  112 ,  122  and finally into the ambient air via the natural convection. 
     In real practice, the aforesaid external layers  112 ,  122  are respectively plated on the main layers  111 ,  112  by means of sand blasting process, extrusion machine, cutting device and impact force such that the external layers  112 ,  122  are formed with recesses, protrusions, wrinkled portions or densely located grain-like projections, thereby increasing a total surface area for dissipating heat effectively. 
     For those persons skilled in the art, it is obvious that once the external surface of the dissipation module is heat-treated, the heat dissipating effect is indeed increased but the heat treatment simultaneously ruptures the planar surface of the dissipating base  11  and the dissipating fins  12 . From a microcosmic view, rupture in the external surface of the dissipating base  11  and the dissipating fins  12  causes irregular dislocation of the ions, narrowing the location space among the ions and difficulties in the machining of the external surface, which, in turn, causes reduction in the heat dissipating ability of the aforesaid external layers  112 ,  122 . 
     Due to aforesaid facts, it is urgently needed to invent a new method for plating film on the external surface of a heat dissipation module in order to overcome the problems encountered during use of the prior art plating method for heat dissipation module. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a plating method for a heat dissipation module, in which, the exterior of the heat dissipation module is plated successively by an adherent film, a mixed film and a noncrystalline DLC film. The noncrystalline DLC film thus formed has regular ions location and provides enhanced heat dissipating ability. 
     A method for plating film on the external surface of a heat dissipation module is provided according to the present invention. The method accordingly includes the steps of: (a) preparing the heat dissipation module; (b) cleaning the external surface of the heat dissipation module; (c) disposing the heat dissipation module into a working chamber, injecting hydrogen and tetra-methylsilane [TMS; Si(CH 3 ) 4 ] gases therein and applying an electric current to generate a bias electric field within the working chamber, thereby plating an adherent film on the external surface of the heat dissipation module; (d) plating a mixed film on an external surface of the adherent film; and (e) plating a noncrystalline DLC film on the mixed film. The mixed film has a distal portion that is spaced farthermost from the heat dissipation module and that consists of larger noncrystalline DLC (diamond-like carbon) material when compared to the remaining portion of the mixed film. 
     When compare to the prior art method, according to the method of the present invention, the adherent film, the mixed film and the noncrystalline DLC film are successively plated on the heat dissipation module so that the noncrystalline DLC film is tightly adhered on the dissipating base and the dissipating fins. Since the noncrystalline DLC film has a balanced ions bonding and enhanced heat dissipating ability, the heat dissipating effect of the heat dissipation module is increased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of this invention will become more apparent in the following detailed description of the preferred embodiment of this invention, with reference to the accompanying drawings, in which: 
         FIG. 1  shows a conventional heat dissipation module dissipating heat generated by a function element; 
         FIG. 2  illustrates a plasma enhanced chemical vapor deposition apparatus for plating films onto a heat dissipation module according to the method of the present invention; 
         FIG. 3  illustrates how the heat dissipation module is mounted in a working chamber for conducting the method of the present invention; 
         FIG. 4  illustrates gas being injected into an electric field within the working chamber during carrying out the method of the present invention; 
         FIG. 5  shows an adherent film being plated on a dissipating base and fins of the heat dissipation module according to the method of the present invention; 
         FIG. 6  is a cross sectional view of the heat dissipating module taken along an encircle portion X in  FIG. 5 ; 
         FIG. 7  illustrates a mixed film being plated on the adherent film of the heat dissipation module according to the method of the present invention; 
         FIG. 8  is a cross sectional view of the heat dissipating module taken along an encircle portion Y in  FIG. 8 ; 
         FIG. 9  illustrates a mixed film being plated on the adherent film of the heat dissipation module according to the method of the present invention; 
         FIG. 10  is a cross sectional view of the heat dissipating module taken along an encircle portion Z in  FIG. 9 ; and 
         FIG. 11  shows a plated heat dissipation module formed according to the present method dissipating heat generated by a function element. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The method of the present invention is used for plating film on the external surface of a heat dissipation module, thereby forming a plated heat dissipation module with effective heat dissipating properties. An example is given in the following paragraphs, but the restriction should not be limited thereto. 
       FIG. 2  illustrates a plasma enhanced chemical vapor deposition apparatus  100  for plating films on the heat dissipation module  3  according to the method of the present invention. As illustrated, the heat dissipation module  3  accordingly includes a dissipating base  311  and a plurality of fins  321  extending from or integrally formed with the dissipating base  311 , which are intended for undergoing the film-plating method of the present invention, thereby forming the plated heat dissipation module. The apparatus  100  includes a working chamber  4 , a vacuum pump  5  for pumping out air from the chamber  4 , a power control device  6 . The chamber  4  is formed with four vents  41 , 42 , 43 , 44 . The power control device  6  includes an adjustable power supply  61  disposed exterior of the chamber  4 , a conductive carrier frame  62  extending into the chamber  4  from the power supply  61 . 
       FIGS. 3 to 10  illustrates one embodiment of the film-plating method of the present invention. Firstly, the heat dissipation module  3  is erected securely on the carrier frame  62  as shown in  FIG. 3  and is connected electrically to the power supply  61 . An electric current is applied so as to generate a bias electric field within the chamber  4 . 
     The pump  5  is activated to pump out the air from the working chamber  4 , thereby converting into a vacuum chamber. The power supply  61  supplies an external electric current to the carrier frame  62  so that a high current level is existed in the frame  62  while a lower current level is existed in the chamber, thereby forming the bias electric field E. 
     Referring to  FIG. 4 , gases are injected into the bias electric field in the vacuum chamber, where the gases become plasma-like ions after ionization process. In this embodiment, when plating a film on the heat dissipation module  3 , H (hydrogen) and A (argon) gases are injected into the chamber  4  via the vents  41 ,  42  after shutting the vents  43 ,  44 , wherein the gases convert into hydrogen ions H′ and argon ions A′ due to the bias electric field E. The hydrogen and argon ions thus formed will collide against the heat dissipation module  3 , thereby cleaning the external surface thereof. 
     The cleaning operation of the heat dissipation module  3  includes a first cleaning section of 10-35 minutes and a second cleaning section of 10-45 minutes. During the first cleaning section, the pressure in the vacuum chamber is maintained under 2-4 μbar, the bias electric field E at 300-700V (Voltage) and the power of the applied electric current at 600-1400 W (watt), respectively. At the same, the flow rate of argon and hydrogen is maintained at 50-200 sccm (standard cc/min) respectively. 
     During the second cleaning time, the pressure in the working chamber is maintained under of 2-15 μbar, the bias electric field E at 300-700V and the power of the applied electric current at 600-1400 W. During this time, the flow rate of H is at 50-200 sccm while the flow rate of A is at 200-400 sccm (standard cc/min). 
       FIG. 5  shows an adherent film  322  being plated on the dissipating base  311  and the dissipating fins  321  of the heat dissipation module  3  according to the method of the present invention.  FIG. 6  is an enlarged view of the encircled portion (X) shown in  FIG. 5 . For plating the adherent film  322 , the vents  41  and  44  are closed firstly and hydrogen and tetra-methylsilane [TMS; Si(CH 3 ) 4 ] gases are injected into the working chamber  4  via the vents  42  and  43 , wherein the adherent film  322  is deposited tightly on the dissipating base  311  and the dissipating fins  321  due to the bias electric field E and after the ionization process. 
     For plating the adherent film  312 ,  322 , the flow rate of the hydrogen is maintained at 50-200 sccm while the TMS gas at 50-250 sccm for 1-15 min respectively. The adherent film  312 ,  322  thus formed consists of Silicon, carborundum (SiC) and a minor portion of hydrocarbon compound. The adherent film  312 ,  322  has a silicon ratio greater than the noncrystalline DLC material, and therefore adheres securely on the dissipating base  311  and the dissipating fins  321 . At this time, the power of the applied electric current supplied by the power supply  61  is maintained at 800-1500 W while the bias electric field E at 400-700V and the working chamber is maintained under between 2-4 μbar. 
       FIG. 7  illustrates how a mixed film being plated on the adherent film according to the method of the present invention.  FIG. 8  is an enlarged view of the encircled portion (Y) shown in  FIG. 7 . In order to form a mixed film  313 ,  323  over the adherent film  312 ,  322 , the vent  41  is closed firstly, and afterwards, hydrocarbon gas together with the hydrogen and tetra-methylsilane gases are injected into the working chamber via the vents  42 ,  43  and  44 , thereby depositing the mixed film  313 ,  323  over the adherent film  312 ,  322  due to the ionization process caused by the bias electric field E. The hydrocarbon gas in this embodiment is Acetylene gas C. 
     It takes 1-35 min for depositing the mixed film  313 ,  323  over the adherent film  312 ,  322 . During this period, the flow rate of Acetylene gas C is maintained at 50-800 sccm, the flow rate of drogen is maintained at 50-800 sccm while the flow rate of the TMS gas S is maintained at 50-250 sccm. The applied electric current supplied by the power supply  61  is maintained at 800-1500 W so as to generate the bias electric field with 400-700V. The working chamber is maintained between 4-15 μbar. The mixed film  313 ,  323  thus formed consists of carborundum (SiC), noncrystalline DLC (diamond-like carbon) material and a minor portion of silicon. Since the mixed film  313 ,  323  has composition (such as Si and SiC) of the adherent film  312 ,  322 , the material of the mixed film  313 ,  323  at the initial plating stage is similar to that of the adherent film  312 ,  322  so that the mixed film  313 ,  323  can be securely adhered on the adherent film  312 ,  322 . 
     During deposition of the mixed film  313 ,  323 , by slightly increasing the flow rate of Acetylene gas C, hydrogen and tetra-methylsilane gases, the mixed film  313 ,  323  thus formed accordingly has the following features. The mixed film  313 ,  323  has a distal portion that is spaced farthermost from the dissipating base  311  and the dissipating fins  321  and that contains larger noncrystalline DLC (diamond-like carbon) material when compared to the remaining portion of the mixed film  323  and a proximate portion that contains composition similar to the adherent film  322 . 
       FIG. 9  illustrates how a noncrystalline DLC film  314 ,  324  being plated over the mixed film  313 ,  323  according to the method of the present invention.  FIG. 10  is a cross sectional view of the heat dissipating module taken along an encircle portion Z in  FIG. 9 . For plating the noncrystalline DLC film  314 ,  324 , the vent  41  in shut up immediately, the vent  42  is gradually shut up while the vents  42 ,  44  are open to inject the H and Acetylene gases into the working chamber  4 . By ionization process due to the bias electric field E, the noncrystalline DLC film  314 ,  324  is deposited over the mixed film  313 ,  323 . At this time, the plated dissipating base  31  includes the dissipating base  311  plated with the adherent film  312 , the mixed film  313  and the noncrystalline DLC film  314 . The plated dissipating fin  32  includes the dissipating fin  321  the adherent film  322 , the mixed film  323  and the noncrystalline DLC film  324 . In other words, the plated heat dissipation module  3   a  consists of the plated dissipating base  31  and the plated dissipating fin  32 . 
     It takes 1-200 min for depositing the noncrystalline DLC film  314 ,  324  over the mixed film  313 ,  323 . During this period, the flow rate of hydrogen and Acetylene is maintained at 50-800 sccm while the flow rate of the TMS gas S is reduced gradually to 0 sccm. The applied electric current supplied by the power supply  61  is maintained at 800-1500 W so as to generate the bias electric field E with 400-700V. The working chamber is maintained between 2-20 μbar. 
     The outermost part of the mixed film  323  has the composition very similar to the noncrystalline DLC film  324 . Thus, the noncrystalline DLC film  324  can tightly adhered on the mixed film  323 . At the same time, since the mixed film  323  is tightly adhered on the adherent film  322 , which, in turn, is tightly adhered on the main axle  321 , the plated driven shaft  32  has the noncrystalline DLC film  324  tightly attached thereon. 
     From the above mentioned explanation, it is apparent for those skilled in the art and when compare to the prior art plating method, in the film-plating method of the present invention, the adherent film  312 ,  322 , the mixed film  313 , 323 , and the noncrystalline DLC film  314 ,  324  are deposited successively on the dissipating base  311  and the dissipating fins  321 . Thus, the noncrystalline DLC film  314 ,  324  adheres tightly on the dissipating base  311  and the dissipating fins  321  to form the plated heat dissipation module  3   a.  Since the noncrystalline DLC film has a balanced ions bonding and enhanced heat dissipating ability, the heat dissipating effect of the plated heat dissipation module is increased. 
       FIG. 11  shows a plated heat dissipation module formed according to the present method dissipating heat generated by a function element. As illustrated, the plated heat dissipation module  3   a  formed accordingly is used to dissipate the heat generated by the function element  2 . An experiment is conducted under the conditions that the present plated heat dissipation module  3   a  the prior art heat dissipation module  1  having the similar geometric dimension and the same function elements. The experiment testifies for the enhanced heat dissipating ability of the present plated heat dissipation module  3   a.    
     An LED (light emitting diode) serves as the function element  2  in the aforesaid experiment and has a power of 5 W. When the prior and present heat dissipation modules  1 ,  3   a  are used respectively to dissipate the heat generated due to operation of the LED for 15 mins, the external surface of function element  2  has 70° C. and 63° C. respectively, thereby testifying for the enhanced heat dissipating ability of the present plated heat dissipation module  3   a.    
     While the invention has been described in connection with what is considered the most practical and preferred embodiments, it is understood that this invention is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.