Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a 35 U.S.C. §371 national stage application of PCT/CN2010/076325 filed Aug. 25, 2010, which claims the benefit of Chinese Patent Application No. 201010191873.7 filed Jun. 4, 2010 and Chinese Patent Application No. 201020215719.4 filed Jun. 4, 2010, each of which is hereby incorporated herein by reference in its entirety for all purposes. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     TECHNICAL FIELD OF THE INVENTION 
     The present application relates to a method for manufacturing an LED bracket applicable to an LED device and the LED bracket, in particular, to a method for manufacturing a surface mounted power LED bracket and the surface mounted power LED bracket. 
     BACKGROUND OF THE INVENTION 
     The semiconductor illumination is known as the fourth generation of illuminating source, and is gradually applied to the general illumination field. The power light emitting diode (power LED) is popular in the market because of its high brightness and high power. There are two types of conventional power LED brackets: a PLCC-type (plastic leaded chip carrier) bracket and a ceramic substrate bracket. 
       FIG. 1  shows a structural schematic view of a prior PLCC-type bracket. In the PLCC-type bracket, a plastic casing  01  having a reflection cavity covers a metal lead frame  02 . The metal lead frame  02  includes a chip mounting portion  03  for carrying an LED chip  04 , and an electrode pin  05 . The chip mounting portion  03  forms an integral structure together with a positive electrode or a negative electrode. The PLCC-type bracket is particularly applicable to fields requiring a high light distribution and a high mounting density because of the reflection cavity and compact structure of the PLCC-type bracket. A high power LED may generate high heat energy in operation, thus it needs to take some technical means to help to dissipate the generated heat energy. Otherwise, the lifetime and light emitting effect of the high power LED will be affected. In a typical packaging structure of the PLCC-type bracket for the high power LED, the plastic casing having the reflection cavity not only covers the metal lead frame, but also covers a heat sink provided at the bottom of an LED chip and exposed outside the bracket. The heat sink generally employs a metal material having a good heat dissipation effect, such as copper, to facilitate the dissipation of the high heat energy generated in the operation of the LED. The PLCC-type high power LED is one of the most commonly used high power LED packaging structures because of the good heat dissipation effect thereof. 
     Another conventional power LED bracket is the ceramic substrate. A typical packaging structure of the ceramic substrate is shown in  FIG. 2 . A substrate  06  for carrying an LED chip, and a reflection cavity  07  arranged on the substrate  06  employ a ceramic material. As to a power LED device, at least one through hole  08  is provided in a chip mounting portion of the substrate  06 , with a heat conductive material being filled in the through hole  08  for increasing the heat dissipation effect, to meet heat dissipation requirement of the high power LED device. Since the ceramic substrate has good insulating property and heat dissipating property, the ceramic substrate is widely applied to the high power LED field, and occupies the whole high power LED market together with the PLCC-type bracket. 
     However, the PLCC-type bracket and the ceramic substrate have some disadvantages. As for the PLCC-type bracket, manufacture processes thereof are complicated and require a high precision. Many relevant patent applications have been developed, however, key technologies of these patent applications are still grasped by foreign enterprises, and these technologies are relatively mature and have limited rooms for improvement. Especially for the PLCC-type bracket for a power LED, a heat sink is further needed to improve heat dissipation of the bracket. Thus, it needs to further provide a counter bore and mount the heat sink in the counter bore, which causes the structure of the PLCC-type bracket for a power LED more complicated, and thus the bracket packaging process is more complicated. At the same time, the PLCC-type high power LED has a large volume, the packaging structure thereof cannot be applied to a reflow soldering process, is not applicable to a full-automatic and batch testing and taping process and is inconvenient for a batch soldering and mounting of the down-stream products, and is particularly inconvenient for the subsequent surface mounted processes of the manufacture of the LED product. Therefore, the prior PLCC-type bracket has a complicated structure, a relatively complicated manufacture process and a relatively high production cost, which limits the subsequent manufacture processes of the product, increases the production cost of the subsequent LED products, reduces the production efficiency, and accordingly limit the application range of the PLCC-type bracket power LED. 
     The ceramic substrate may overcome the main disadvantages of the PLCC-type bracket, however, the ceramic substrate has some common problems, for example, manufacture processes of the ceramic substrate are difficult, cost of the ceramic substrate is high, and material of the ceramic substrate is fragile, which are key factors that restrain the ceramic substrate from fully substituting the PLCC-type bracket. 
     Based on the above description, there is a need to provide an LED bracket structure and a manufacture process thereof, the LED bracket structure has a simple manufacture process, a good light emitting effect, a good heat dissipation effect and a low production cost, and compared with the above PLCC-type bracket and ceramic substrate, the LED bracket structure can overcome the above technical drawbacks of the prior PLCC-type bracket and ceramic substrate. In the prior technical improvements, the person skilled in the art has already made attempts to improve the manufacture material and the manufacture process. However, these attempts can not properly solve or overcome the above technical drawbacks. 
     Before making the present application, applicants of the present application filed a patent application (China Patent Application No. 201010165442.3) titled “METHOD FOR MANUFACTURING A SURFACE MOUNTED POWER LED BRACKET AND THE SURFACE MOUNTED POWER LED BRACKET”, which provides a method for manufacturing a surface mounted power LED bracket by employing a single-sided copper coated circuit board and a metal sheet, and the bracket product. This technical solution has such advantages as having a simple manufacture method, a low cost and a good heat dissipation effect. This technical solution can overcome drawbacks of the commonly used PLCC-type bracket and ceramic substrate for the power LED, and has a potential of occupying the power LED bracket market. However, it is discovered in the further research that, since the metal sheet is connected to the single-sided copper coated circuit board only via an adhesive film, there may be a gap between the metal sheet and the edge of the bottom of a through hole in the single-sided copper coated circuit board, which may cause the LED bracket hard to pass reliability tests such as the “red ink test”, and thus affect the reliability of the power LED bracket. Further, since the bottom of the through hole and the metal sheet are not closely connected, the bottom surface of the chip mounting portion may not be continuously smooth, which may reduce the light reflection efficiency of the LED chip. 
     In light of the above technical drawbacks, the present application provides a new technical solution to solve the above technical drawbacks. The present application can overcome the technical prejudice, as is commonly accepted by the person skilled in the art, that an ordinary insulating board, such as a PCB board, is not applicable to be employed as a packaging material for the power LED. Meanwhile, the present application can solve the problem that there may be a gap between the metal sheet and the edge of the bottom of the through hole when using a single-sided copper coated circuit substrate as a substrate, and provides a method for manufacturing a power LED bracket and the power LED bracket with a simple process, a low cost, a high reliability, a wide application range, a high heat dissipation property and a high light reflection efficiency. 
     SUMMARY OF THE INVENTION 
     Compared with the prior ceramic substrate and PLCC-type bracket, an ordinary insulating board, such as a PCB board, has advantages such as a low cost, a relatively mature board manufacturing process, namely, the ordinary insulating board has such advantages as a low cost and easy to be manufactured. However, since the ordinary insulating board has disadvantages of poor heat dissipation effect and poor heat resisting property, on one hand, it is generally accepted, by the person skilled in the art, that the ordinary insulating board cannot meet the high heat dissipation property requirement of the power LED device, and thus can only be used for a small power LED device, thereby the ordinary insulating board has a poor universal applicability. On the other hand, problems, such as delamination and deformation of the board may occur in the packaging and die bonding process of the LED due to the poor heat resisting property of the ordinary insulating board, thus the yield rate is low, thereby it is generally accepted by the person skilled in the art that the ordinary insulating board is not applicable to be employed as a packaging material for the power LED. 
     The present application overcomes the above technical prejudice by employing an ordinary insulating board coated with metal layers on two sides thereof as a substrate for manufacturing a power LED bracket, and makes further technical innovations and improvements on the basis of the technical solution in which the single-sided copper coated circuit board is employed as the bracket substrate and is bonded with a the metal sheet, to overcome the existed technical drawbacks. According to the present application, an ordinary insulating board is employed as a substrate, with two sides of the insulating board being coated with metal layers to form a double-sided metal layer coated circuit board, and is used as the substrate for manufacturing the surface mounted power LED bracket. Then, by a regular manufacture process of the ordinary insulating board and an innovative and special design for the bracket structure, the present application can realize an object of providing a method for manufacturing a surface mounted power LED bracket and the surface mounted power LED bracket. 
     Based on the method technical solution of the present application, a method for manufacturing a surface mounted power LED bracket is provided. The method includes steps of: 1) preparing a double-sided metal layer coated circuit substrate, including; providing an ordinary insulating board as a substrate for the circuit substrate, coating an upper surface of the substrate with a first metal layer and a lower surface of the substrate with a second metal layer, thereby forming the double-sided metal layer coated circuit substrate; 2) forming a hole, including forming at least one hole in the circuit substrate by a mechanical process, a laser process or an etching process; 3) providing a hole-wall metal layer, including providing a metal layer on an inner wall of the hole by a plating process, a deposition process or a screen printing process; 4) increasing a thickness of a metal layer, including increasing a thickness of the metal layer on the lower surface of the circuit substrate by a fusion process, a deposition process or a plating process. A third metal layer is integrally formed on the second metal layer to form a thick metal layer, such that a metal layer at a bottom of the hole has a thickness that can carry an LED chip; 5) etching the metal layers, including processing the metal layers on the circuit substrate by an etching process to form a first circuit layer on the upper surface of the circuit substrate and a second circuit layer on the lower surface of the circuit substrate, wherein the first circuit layer, the second circuit layer and the hole form a power LED bracket structure; and 6) separating a power LED bracket unit from the power LED bracket structure, including separating a power LED bracket unit from the power LED bracket structure formed by the above steps by a cutting process. 
     It is further provided according to the present application a technical solution of a product manufactured by the above method for manufacturing the surface mounted power LED bracket. According to the technical solution of the surface mounted power LED bracket of the present application, the structure of the surface mounted power LED bracket includes a double-sided metal layer coated circuit substrate provided as a bracket substrate. The bracket substrate is provided with a hole and bracket circuit layers, thereby forming the power LED bracket. The bracket substrate comprises a first metal layer, a second metal layer and an insulating substrate provided between the first metal layer and the second metal layer. The circuit layers comprise a first circuit layer on an upper surface of the substrate and a second circuit layer on a lower surface of the substrate. The first circuit layer comprises a lead connecting portion, surrounding the hole and being used for welding a metal lead, and a first positive and negative electrode layer at two sides of the hole. The lead connecting portion is electrically connected to the first positive and negative electrode layer. The bracket substrate has a thick metal layer at a bottom thereof. The second circuit layer comprises a chip mounting portion, which is formed by the thick metal layer corresponding to a bottom of the hole, and a second positive and negative electrode layer corresponding to and electrically insulated from the chip mounting portion. The first positive and negative electrode layer and the second positive and negative electrode layer are electrically connected to form electrode of the bracket. And a metal layer is provided on an inner wall of the hole. 
     The present application provides a bracket structure and a method for manufacturing the bracket structure which are different from those of the prior art. The technical solutions of the present application make innovations on the manufacture process and the product structure. The present application overcomes the prior technical prejudice by employing an ordinary insulating board, with metal layers coated on both sides thereof, as a double-sided metal layer coated circuit substrate to manufacture the bracket. With the innovative design of the structure and the process of the technical solutions of the present application, and with a machining process of the ordinary insulating board and other conventional processes for manufacturing the LED bracket, the double-sided metal layer coated circuit substrate can be processed into a surface mounted power LED bracket. On one hand, the present application has simple processes, high production efficiency, good product reliability, and greatly reduces the production cost. On the other hand, with the innovative design of the bracket structure of the present application, the LED bracket made of the ordinary insulating board can meet the high heat-resistant requirement of the power LED. In the bracket structure of the present application, an LED chip directly contacts a thick metal layer which is of an integral structure, has a good heat conductivity and forms a chip mounting portion, such that heat generated by the LED chip in operation can be released to the outside directly through the thick metal layer, and thus the LED bracket has a good heat dissipation effect, a high reliability, and a good light emitting effect. It is proved through tests that, the LED bracket, made of an ordinary insulating board and with metal layers coated on both sides, has a good heat resisting property, and problems such as delamination and cracking would not occur in the die bonding process using a silver paste of the LED packaging. 
     Based on the above description, the method of the present application overcomes the technical prejudice generally accepted by the person skilled in the art that the ordinary insulating board cannot be employed to manufacture the power LED bracket. The ordinary insulating board is skillfully applied in the manufacture of the LED bracket, which greatly simplifies the prior manufacture process of the power LED bracket, improves the production efficiency, and reduces the production cost. The product manufactured by the method of the present application has a low cost, a high reliability, a good heat dissipation and light emitting effect, can be applied to a reflow soldering process, and is applicable to a full-automatic and batch testing and taping process, is convenient for a batch soldering and mounting of the downstream products, and is particularly convenient for the subsequent surface mounted processes of the manufacture of the LED product, and thus has a wider application range. Therefore, the present application is an invention overcoming a technical prejudice. Compared with the prior art, the method and the product of the present application achieve a notable progress and have prominent and positive advantageous technical effects. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a structural schematic view of a PLCC-type bracket for a power LED in the prior art; 
         FIG. 2  is a structural schematic view of a ceramic substrate bracket for a power LED in the prior art; 
         FIG. 3  is a process flow chart of a method according to a first embodiment of the present application; 
         FIG. 4  is a schematic view of process steps of the method according to the first embodiment of the present application; 
         FIG. 5  is a process flow chart of a method according to a second embodiment of the present application; 
         FIG. 6  is a schematic view of process steps of the method according to the second embodiment of the present application; 
         FIG. 7  is a structural schematic view of a power LED bracket according to a first embodiment of the present application; 
         FIG. 8  is a structural schematic view of a power LED bracket according to a second embodiment of the present application; 
         FIG. 9  is a structural schematic view of a power LED bracket according to a third embodiment of the present application; and 
         FIG. 10  is a structural schematic view of a power LED bracket according to a fourth embodiment of the present application. 
       
         
           
                 
               
                 
                 
                 
               
                 
                 
                 
                 
               
                 
               
                 
                 
               
                 
                 
                 
               
                 
                 
                 
               
                 
                 
                 
               
                 
                 
               
                 
                 
               
                 
                 
               
                 
                 
               
                 
               
                 
                 
                 
                 
               
                 
                 
               
                 
                 
               
                 
                 
               
                 
                 
                 
               
                 
                 
               
                 
                 
                 
               
                 
               
                 
                 
               
                 
                 
               
                 
                 
                 
               
                 
                 
                 
               
                 
                 
               
                 
                 
               
                 
                 
               
                 
                 
               
                 
                 
               
             
                 
                     
                 
                 
                   Reference Numbers Utilized in the drawings: 
                 
                 
                     
                 
               
               
                 
                     
                 
               
            
             
                 
                   01. plastic casing 
                   02. metal lead frame 
                   03. chip mounting portion 
                 
               
            
             
                 
                   04. LED chip 
                   05. electrode pin 
                   06. substrate 
                   07. reflection cavity 
                 
               
            
             
                 
                   1. double-sided metal layer coated circuit substrate 
                 
               
            
             
                 
                   10. ordinary insulating substrate (for short, substrate) 
                   11. first metal layer 
                 
               
            
             
                 
                   12. second metal layer 
                   13. blind hole 
                   131. metal reflection layer 
                 
               
            
             
                 
                   141. small electrode blind hole 
                   142. electrode conductive layer 
                   14. metal foil 
                 
               
            
             
                 
                   15. thick metal layer 
                   16. first circuit layer 
                   161. lead connecting portion 
                 
               
            
             
                 
                   162. first positive and negative electrode layer 
                   17. second circuit layer 
                 
               
            
             
                 
                   171. chip mounting portion 
                   172. second positive and negative electrode layer 
                 
               
            
             
                 
                   2. double-sided metal layer coated circuit substrate  
                   20. ordinary insulating substrate 
                 
               
            
             
                 
                   21. first metal layer 
                   22. second metal layer 
                 
               
            
             
                 
                   221. metal layer at an edge of a bottom of a through hole 
                 
                 
                   222. metal layer at an edge of a bottom of a small electrode through hole 
                 
               
            
             
                 
                   23. through hole 
                   231. metal reflection layer 
                   24. metal foil 
                   25. adhesive film 
                 
               
            
             
                 
                   26. first circuit layer 
                   261. lead connecting portion 
                 
               
            
             
                 
                   262. first positive and negative electrode layer 
                   27. second circuit layer 
                 
               
            
             
                 
                   271. chip mounting portion 
                   272. second positive and negative electrode layer 
                 
                 
                   281. small electrode through hole 
                   282. electrode conductive layer 
                 
               
            
             
                 
                   3. bracket substrate 
                   31. through hole 
                   311. hole-wall metal layer 
                 
               
            
             
                 
                   32. positive and negative electrode 
                   321. small electrode through hole 
                 
               
            
             
                 
                   322. electrode conductive layer 
                   33. first metal layer 
                   34. second metal layer 
                 
               
            
             
                 
                   341. metal layer at a bottom of the through hole 
                 
               
            
             
                 
                   342. metal layer at a bottom of a small electrode through hole 
                   35. metal foil 
                 
               
            
             
                 
                   351. chip mounting portion 
                   352. second positive and negative electrode layer 
                 
               
            
             
                 
                   36. adhesive film 
                   37. cup-shaped covering board 
                   371. cup hole 
                 
               
            
             
                 
                   4. bracket substrate 
                   41. blind hole 
                   411. hole-wall metal layer 
                 
               
            
             
                 
                   42. positive and negative electrode  
                   421. small electrode blind hole 
                 
                 
                   43. first metal layer 
                   431. lead connecting portion 
                 
               
            
             
                 
                   432. first positive and negative electrode layer 
                   44. second metal layer 
                 
               
            
             
                 
                   441. chip mounting portion 
                   442. second positive and negative electrode layer 
                 
               
            
             
                 
                   422. electrode conductive layer  
                   45. cup-shaped covering board 
                 
               
            
             
                 
                   451. cup hole 
                   46. adhesive film 
                 
                 
                     
                 
               
            
           
         
       
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A PLCC-type bracket in the prior art is shown in  FIG. 1 . A plastic casing  01  having a reflection cavity covers a metal lead frame  02 , and a chip mounting portion  03  for carrying an LED chip  04  and an electrode pin  05  are provided on the metal lead frame  02 . A ceramic substrate in the prior art is shown in  FIG. 2 . A substrate  06  for carrying an LED chip and a reflection cavity  07  provided on the substrate  06  employ a ceramic material. 
     A method for manufacturing a power LED bracket according to a first embodiment of the present application is shown in  FIGS. 3 and 4 . Manufacture steps of the embodiment are described in detail in conjunction with the process flow chart of the embodiment shown in  FIG. 3  and the schematic view of the process steps shown in  FIG. 4 . 
     Step S 11 ), preparing a double-sided metal layer coated circuit substrate: A double-sided metal layer coated circuit substrate  1  is prepared in advance. As shown in  FIG. 4A , the circuit substrate  1  includes an ordinary insulating substrate  10 , a first metal layer  11  coated on the upper surface of the substrate and a second metal layer  12  coated on the lower surface of the substrate  10 . There is no special requirement on the material of the substrate  10 . The substrate may be an ordinary insulating board such as a PCB board. Preferably, the substrate may be cheap materials, such as a fiber-glass cloth substrate, a CEM-3 (Composite Epoxy Material Grade-3) substrate, or a CEM-1 (Composite Epoxy Material Grade-1) substrate. It is also preferable to employ a bismaleimide-triazine resin (BT) substrate and similar base materials. Preferably, the metal layers employ copper layers. 
     Step S 12 ), forming a blind hole: At least one blind hole  13  is formed on the double-sided metal layer coated circuit substrate by a mechanical process, a laser process or an etching process, with the bottom of the blind hole  13  being formed by the second metal layer. In other words, the second metal layer is remained (as shown in  FIG. 4B ). Preferably, the blind hole may be formed as a blind hole array of M rows×N columns to form a bracket substrate structure having the blind hole  13  array of M rows×N columns (not shown in  FIG. 2 ). In another preferable solution, at least one small electrode blind hole  141  may be formed at each side of two sides of the blind hole in the step, to form a part of an electrode (as shown in  FIG. 4 ). 
     Step S 13 ), providing a hole-wall metal layer: A metal reflection layer  131  is provided on an inner wall of the blind hole  13  by a plating process, a deposition process or a screen printing process. Preferably, the metal reflection layer may be a copper layer or a silver layer to increase light emitting effect of an LED device. In the preferable solution with the small electrode blind holes  141 , an electrode conductive layer  142  is provided on the inner wall of each small electrode blind hole  141  (as shown in  FIG. 4C ) in the step S 13 ), to form a part of a positive electrode or a part of a negative electrode. Preferably, the electrode conductive layer may be a cooper layer or a silver layer so as to improve conductive property of the electrode. 
     Step S 14 ), forming a thick metal layer: A third metal layer is integrally formed on the second metal layer  12  of the double-sided metal layer coated circuit substrate  1  by a hot melt process, a plating process or a deposition process, to further increase a thickness of the metal layer, thereby forming a thick metal layer  15  (as shown in  FIG. 4D ). Preferably, the third metal layer may be a copper layer. In one preferable solution, a third metal layer is formed on the second metal layer  12  by a plating process or a deposition process, such that the third metal layer and the second metal layer  12  form the thick metal layer  15  having a thickness that can carry an LED chip. In another preferable solution, firstly, a metal foil  14  is laminated and bonded, at the lower surface of the double-sided metal layer coated circuit substrate  1  to the double-sided metal layer coated circuit substrate  1 , such that the metal foil  14  is physically connected to the second metal layer  12  at the bottom of the circuit substrate (not shown in  FIG. 4 ); then, the metal foil  14  and the metal layer  12  at the bottom of the circuit substrate are closely connected into an integral structure by a hot melt process, a plating process or a deposition process, to form the thick metal layer  15 . In this solution, it is preferable to provide an adhesive film between the metal foil  14  and the bottom of the circuit substrate; then the adhesive film is melted, when being heated at a high temperature, into a state having a bonding property; and then the metal foil  14  is laminated such that the metal foil  14  is physically bonded to the bottom of the circuit substrate, to form a fake connection as shown in  FIGS. 4E and 4F ; lastly, the metal foil  14  and the metal layer  12  at the bottom of the circuit substrate are closely connected into an integral structure by the hot melt process, the plating process or the deposition process, thereby forming the thick metal layer  15 . 
     Step S 15 ), Performing etching: A first circuit layer  16  is formed by the first metal layer and a second circuit layer  17  is formed by the thick metal layer  15 , by an etching process. The first circuit layer  16  includes a lead connecting portion  161  and a first positive and negative electrode layer  162  electrically connected to the lead connecting portion  161 . The second circuit layer  17  includes a chip mounting portion  171  and a second positive and negative electrode layer  172  electrically insulated from the chip mounting portion  171 . The bottom of the blind hole  13  acts as the chip mounting portion  171  for carrying the LED chip. In the preferable solution with the small electrode blind holes  141 , a conductive metal layer  142  is provided on the inner wall of each small electrode blind hole  141 , and the conductive metal layer  142  is electrically connected to the first positive and negative electrode layer  162  and the second positive and negative electrode layer  172 , to form a positive electrode and a negative electrode (as shown in  FIG. 4E ). The first circuit layer, the second circuit layer and the blind hole form a power LED bracket structure. 
     Step S 16 ), separating a power LED bracket unit from the power LED bracket structure: The power LED bracket structure formed by the above steps is processed by a cutting process to obtain a separate power LED bracket unit. 
     Some non-essential and optional steps may be further included in the above steps, for example: An etching step S 13   b ) may be performed before the step S 14 ). Most of the second metal layer on the lower surface of the circuit substrate is removed by an etching process, to remain at least the metal layer surrounding the bottom of the blind hole as a basis of the second circuit layer in the subsequent processes. Step S 13   b ) is non-essential and may be omitted. 
     A step of plating the circuit layers S 15   a ) may be performed after the step 15). A metal layer is further provided on the first circuit layer  16 , the second circuit layer  17 , the upper surface of the metal foil at the bottom of the blind hole  13  and the metal layer on the inner wall of the blind hole by a plating process, so as to increase luminance brightness and solderability of the bracket. The metal layer further provided may be a silver layer, a gold layer, a tin layer or other similar metal layers. Step Si  5   a ) is non-essential and may be omitted. 
     A step of installing a cup-shaped covering board S 15   a ′) may be performed after the step S 15 ). Step S 15   a ′) is a non-essential and optional step, and comprises the following sub-steps: sub-step 1), preparing a substrate. There is no special requirement on the material of the substrate. The substrate may be an ordinary insulating board such as a PCB board. Preferably, the substrate may be cheap materials such as a fiber-glass cloth substrate, a CEM-3 (Composite Epoxy Material Grade-3) substrate, a CEM-1. (Composite Epoxy Material Grade-1) substrate, a FR-1 (Flame Resistant Laminates Grade-1) and a FR-2 (Flame Resistant Laminates Grade-2). It is also preferable to employ a bismaleimide-triazine resin substrate and similar base materials. Sub-step 2), forming a cup hole, the position and the number of which is corresponding to the position and the number of the blind hole formed in the step S 12 ), on the substrate by a mechanical process, a laser process or an etching process, to form a cup-shaped covering board. Preferably, the cup hole is of a reflection cup shape or a cylindrical shape. Sub-step 3), coating a black material on the upper surface of the cup-shaped covering board to increase contrast ratio of a device. Sub-step 4), bonding the cup-shaped covering board to the upper surface of the circuit substrate formed by the step S 15 ) or the step S 15   a ). The cup hole has a diameter larger than a diameter of the blind hole, such that the cup-shaped covering board covers the other portions of the first circuit layer except for the lead connecting portion. Among the above sub-steps, sub-step 3) is optional, and thus may be omitted. A preferable embodiment of sub-step 4) is as follows: A) providing an adhesive film between the cup-shaped covering board and the upper surface of the circuit substrate; B) heating the adhesive film at a high temperature till the adhesive film is melted into a state having an adhesive property, thereby bonding the cup-shaped covering board to the upper surface of the circuit substrate. 
     Steps S 15   a ) and S 15   a ′) are non-essential, thus one of the two steps or both of them may be omitted in other embodiments. 
     An ordinary insulating board is processed in the above processes which are easy to perform and can achieve a high yield rate. Compared with the prior art, the above processes can greatly improve the production efficiency and reduce the production cost. 
     The power LED bracket unit formed by the above steps is of a surface mounted bracket, and can substitute the prior PLCC-type bracket and ceramic substrate bracket for a high power LED. The power LED bracket unit formed by steps including step S 15   a ′) can substitute the prior conventional top light-illuminating LED bracket, and is particularly applicable to a top light-illuminating LED device for a display screen. 
     The present embodiment employs some simple processes, in which a metal conductive layer  131  of the blind hole is formed on the double-sided metal layer coated circuit substrate  1 , and an integral thick metal layer is formed by directly forming a third metal layer on the second metal layer of the circuit substrate or bonding a metal foil on the second metal layer to form a close connection. The processes can solve problems, for example, there may be a gap between an edge of the bottom of the hole and the metal sheet, and it is difficult to pass reliability tests such as the “red ink test” due to the gap, which improves the reliability of the power LED bracket. At the same time, in the processes of the embodiment, an integral thick metal layer is formed at the bottom of the blind hole such that a smooth connection is formed at the bottom of the blind hole, thereby the light emitting rate of the LED product can be increased. 
     A method for manufacturing a power LED bracket according to a second embodiment of the present application is shown in  FIGS. 5 and 6 . Manufacture steps of the embodiment are described in detail in conjunction with the process flow chart of the embodiment shown in  FIG. 5  and the schematic view of process steps shown in  FIG. 6 . 
     Step S 21 ), preparing a double-sided metal layer coated circuit substrate: A double-sided metal layer coated circuit substrate  2  is prepared in advance. The circuit substrate  2  includes an ordinary insulating substrate  20 , a first metal layer  21  coated on the upper surface of the substrate and a second metal layer  22  coated on the lower surface of the substrate. There is no special requirement on the material of the substrate  20 . The substrate may be an ordinary insulating board such as a PCB board. Preferably, the substrate may be cheap materials such as a fiber-glass cloth substrate (FR-4), a CEM-3 (Composite Epoxy Material Grade-3) substrate, or a CEM-1 (Composite Epoxy Material Grade-1) substrate. It is also preferable to employ a bismaleimide-triazine resin (BT) substrate and similar base materials. Preferably, the metal layers are copper layers. 
     Step S 22 ), forming a through hole: At least one through hole  23  is formed on the double-sided metal layer coated circuit substrate  2  by a mechanical process, a laser process or an etching process (as shown in  FIG. 6B ). In one preferable solution, the through hole may be formed as a through hole array of M rows×N columns to form a bracket substrate having the through hole  23  array of M rows×N columns (not shown in  FIG. 6 ). In another preferable solution, at least one small electrode through hole  281  is formed at each side of two sides of the through hole in the step, to form a part of an electrode. 
     Step S 23 ), providing a hole-wall metal layer: A metal layer  231  having a reflective property is provided on the inner wall of the through hole  23  by a plating process, a deposition process or a screen printing process. In the preferable solution with the small electrode through holes  281 , a metal layer is provided on the inner wall of each small electrode through hole to form an electrode conductive layer  282  (as shown in  FIG. 6C ), so as to form a part of a positive electrode or a part of a negative electrode. 
     Step S 24 ), Performing a first etching: The first metal layer  21  on the upper surface of the metal layer coated circuit substrate is remained. Most of the second metal layer  22  on the lower surface of the metal layer coated circuit substrate is removed by an etching process to remain a metal layer  221  surrounding the edge of the bottom of the through hole  23  as a basis of a chip mounting portion to be formed in the subsequent processes. In the preferable solution with the small electrode through holes, a metal layer  222 , in the second metal layer  22 , surrounding the edge of the bottom of each small electrode through hole  281  is remained as a basis of a second positive and negative electrode layer to be formed in the subsequent processes, so as to form a part of the positive and negative electrode layers of the bracket (as shown in  FIG. 6D ). 
     Step S 25 ), increasing a thickness of a metal layer: A thickness of the metal layer on the lower surface of the circuit substrate is increased by a hot melt process, a deposition process or a plating process. A third metal layer is integrally formed on the second metal layer to form a thick metal layer, such that the metal layer at the bottom of the hole has a thickness that can carry an LED chip. 
     One preferable solution for realizing the step is to provide a metal foil to increase the thickness of the metal layer. That is, a metal foil  24  is laminated, at a lower surface of the double-sided metal layer coated circuit substrate  2 , on the double-sided metal layer coated circuit substrate  2  to form a thick metal layer. Two sub-steps are included: 1) laminating the metal foil, comprising laminating and bonding the metal foil  24  to the bottom of the circuit substrate by a bonding process, to form a fake connection as Shown in  FIG. 6F ; 2) integrally connecting the metal foil with the metal layer at the bottom of the circuit substrate, comprising closely connecting the metal foil and the metal layer at the bottom of the circuit substrate into an integral structure by a hot melt process, a plating process or a deposition process, to form the thick metal layer. 
     In the above preferable solution, the sub step of laminating the metal foil may be realized by bonding the metal foil  24  to the bottom of the double-sided metal layer coated circuit substrate  2  via an adhesive film  25 . The following sub-steps are included: A) providing the adhesive film  25  between the metal foil  24  and the bottom of the double-sided metal layer coated circuit substrate  2 ; B) heating the adhesive film  25  at a high temperature till the adhesive film  25  is melted into a state having an adhesive property, then laminating and bonding the metal foil  24  to the bottom of the double-sided metal layer coated circuit substrate  2 , such that the metal foil  24  and the double-sided metal layer coated circuit substrate  2  are physically connected together to form the fake connection shown in  FIG. 6F . In the preferable solution with the small electrode through holes, a fake connection as shown in  FIG. 6F  is further formed between the metal foil  24  and the metal layer  222  at the bottom of each small electrode through hole  281  of the circuit substrate. The step of integrally connecting the metal foil with the double-sided metal layer coated circuit substrate may be realized by a hot melt process, a plating process or a deposition process, such that the metal foil  24  and the metal layer  221  around the through hole of the double-sided metal layer coated circuit substrate  2  are closely connected into an integral structure, so as to realize the integration of the metal foil and the double-sided metal layer coated circuit substrate. Preferably, in the solution with the small electrode through holes, it further includes a sub-step of closely connecting the metal foil  24  and the metal layer  222  at the bottom of each small electrode through hole  281  of the circuit substrate to form an integral thick metal layer (as shown in  FIGS. 6E ,  6 F, and  6 G). 
     In the present step, though the metal foil  24  is physically connected to the double-sided metal layer coated circuit substrate  2  after the sub step of laminating the metal foil, the metal foil  24  and the metal layer  221  at the bottom of the through hole  23  do not form an integral structure, which may cause the LED bracket fail to pass the reliability tests such as the “red ink test” and may affect the reliability and stability of the LED bracket. The metal foil  24  is closely connected with the bottom of the double-sided metal layer coated circuit substrate  2  by the step of integrally connecting the metal foil with the double-sided metal layer coated circuit substrate, which can achieve the integration of the metal foil and the double-sided metal layer coated circuit substrate, overcome the problem of failing to pass the reliability tests, and increase the reliability of the power LED bracket. Further, the bottom of the through hole can be smoothened by the step, which increases light reflection rate of the through hole. 
     Step S 26 ), Performing a second etching: A first circuit layer  26  is formed by the first metal layer  21  and a second circuit layer  27  is formed by the thick metal layer, by an etching process. The first circuit layer  26  includes a lead connecting portion  261  and a first positive and negative electrode layer  262  electrically connected to the lead connecting portion  261 . The second circuit layer  27  includes a chip mounting portion  271  and a second positive and negative electrode layer  272  electrically insulated from the chip mounting portion  271 . A portion of the metal foil  24  locating at the bottom of the through hole  23  and sealing the bottom of the through hole  23  acts as the chip mounting portion  271  for carrying the LED chip. In the preferable solution with a positive small electrode through hole and a negative small electrode through hole (as shown in  FIG. 6H ), the second positive and negative electrode layer  272  formed in the etching process is a metal layer locating at the bottom of the small electrode through hole  281  and sealing the bottom of the small electrode through hole  281 . The metal layer  282  on the inner wall of each small electrode through hole  281  is electrically connected to the first positive and negative electrode layer  262 , and the second positive and negative electrode layer  272 , respectively, to form a positive electrode or a negative electrode  28  of the power LED bracket (as shown in  FIG. 6H ). 
     Similar to the first embodiment, an optional step of plating the circuit layer S 26   a ) may be performed after the step of etching the metal layer, comprising: forming a metal plating layer on the first circuit layer  26 , the second circuit layer  27 , the upper surface of the metal foil  24  at the bottom of the through hole  23  and the metal layer  231  on the inner wall of the through hole  23  by a plating process, to increase luminance brightness and solderability of the bracket. The metal plating layer may be a silver layer, a gold layer, a tin layer or other similar metal layers. Similar to the first embodiment, an optional step of installing a cup-shaped covering board S 26   a ′) may be performed after the step of etching the metal layer. Detailed sub-steps of step S 26   a ″) are similar to relevant contents described in the first embodiment, and will not be described herein. The above two optional steps are non-essential, thus one of the two steps or both of them may be omitted in other embodiments. 
     Step S 27 ), separating a power LED bracket unit from the power LED bracket structure, comprising processing the power LED bracket structure formed by the above steps by a cutting process to obtain a separate power LED bracket unit. An ordinary insulating board is processed in the above processes which are easy to perform and can achieve a high yield rate. Compared with the prior art, the above processes can greatly improve the production efficiency and reduce the production cost. 
     The present embodiment employs some simple processes, in which a metal conductive layer  231  of the through hole is formed on the double-sided metal layer coated circuit substrate  2 , and an integral thick metal layer is formed after bonding the metal foil to the second metal layer and forming a close connection. These processes can solve problems, for example, there may be a gap between the edge of the bottom of the hole and the metal layer, and it is difficult to pass reliability tests such as the “red ink test” due to the gap, which improves the reliability of the power LED bracket. At the same time, in the processes of the embodiment, the metal layer provided on the inner wall of the through hole form an integral structure with the thick metal layer at the bottom of the through hole such that a smooth connection is formed at the bottom of the hole, thereby the light emitting rate of the LED product can be increased. 
     A power LED bracket according to the present application is shown in  FIG. 7 . The power LED bracket includes: a bracket substrate  3  employing a double-sided metal layer coated circuit substrate; at least one through hole  31  provided in the bracket substrate  3 ; positive and negative electrode  32  at two sides of the through hole  31 ; and a chip mounting portion  351  at the bottom of the through hole  31 . The bracket substrate  3  includes a first metal layer  33 , a second metal layer  34  and an insulating substrate provided between the first metal layer and the second metal layer. Preferably, each of the positive and negative electrode  32  includes at least one small electrode through hole  321  penetrating the bracket substrate  3 . An inner wall of each small electrode through hole  321  is provided with a conductive layer  322  or is filled with a conductive material (not shown). The first metal layer  33  is formed as a first circuit layer, and the first circuit layer includes: a lead connecting portion  331  around the through hole  31 , for soldering a metal lead; and a first positive and negative electrode layer  332  located at two sides of the through hole and electrically connected to the lead connecting portion  331 . The second metal layer  34  is formed as a second circuit layer, and the second circuit layer includes a metal layer  341  surrounding the bottom of the through hole  31  and a metal layer  342  surrounding the bottom of each small electrode through hole  321 . A metal layer  311  having a reflective property is provided on the inner wall of the through hole  31 . A metal foil  35  is further provided at the bottom of the bracket substrate  3 , with a portion of the metal foil  35  sealing the bottom of the through hole  31  acting as a chip mounting portion  351 . The metal foil  35  is bonded to the bottom of the bracket substrate  3  via an adhesive film  36  and forms an integral structure with the metal layer  341  at the bottom of the through hole  31 . The metal foil  35  further includes a second positive and negative electrode layer  352  electrically insulated from the chip mounting portion  351 . The electrode conductive layers  322  or the conductive materials (not shown) are electrically connected to the first positive and negative electrode layer  332  and the second positive and negative electrode layer  352 . 
     A power LED bracket according to another embodiment of the present application is shown in  FIG. 8 . The power LED bracket of the present embodiment differs from the power LED bracket according to the first embodiment by further including a cup-shaped covering board  37  provided on the upper surface of the bracket substrate  3 . The cup-shaped covering board  37  is connected to the upper surface of the bracket substrate  3  via an adhesive film  36 , and further includes a cup hole  371  corresponding to the position of the through hole  31 . A diameter of the cup hole  371  is larger than a diameter of the through hole  31 , with the lead connecting portion  331  being exposed in the cup hole  371  and the positive and negative electrode  32  being covered by the cup-shaped covering board  37 . Preferably, the cup hole  371  of the cup-shaped covering board  37  may be of a reflection cup shape or a cylindrical shape, and is not limited to the present embodiment. Preferably, the upper surface of the cup-shaped covering board  37  may be coated with a black material to increase the contrast ratio. Thus this kind of power LED bracket is particularly applicable to an indoor or outdoor LED display screen. 
     A power LED bracket according to another embodiment of the present application is shown in  FIG. 9 . The power LED bracket includes: a bracket substrate  4  employing a double-sided metal layer coated circuit substrate; at least one blind hole  41  provided in the bracket substrate  4 ; and positive and negative electrode  42  located at two sides of the blind hole  41 . The bracket substrate  4  includes a first metal layer  43 , a second metal layer  44  and an insulating substrate provided between the first metal layer and the second metal layer. The first metal layer  43  is formed as a first circuit layer, and the first circuit layer includes: a lead connecting portion  431  around the blind hole  41 , for soldering a metal lead; and a first positive and negative electrode layer  432  located at two sides of the blind hole and electrically connected to the lead connecting portion  431 . The second metal layer  44  is formed as a second circuit layer, and the second circuit layer includes a metal layer (referred to as a chip mounting portion  441 ) acting as the bottom of the blind, hole  41  and a second positive and negative electrode layer  442 . A metal layer  411  having a reflective property is provided on the inner wall of the blind hole  41 . The chip mounting portion  441  is electrically insulated from the second positive and negative electrode layer  442 . Preferably, each of the positive and negative electrode  42  includes at least one small electrode blind hole  421  penetrating the first metal layer  43  and the substrate  4  of the bracket. An inner wall of each small electrode blind hole  421  is provided with an electrode conductive layer  422  or is filled with a conductive material (not shown), and the electrode conductive layer  422  or the conductive material is electrically connected to the first positive and negative electrode layer  432  and the second positive and negative electrode layer  442 . 
     A power LED bracket according to another of the present application is shown in  FIG. 10 . The power LED bracket of the present embodiment differs from the power LED bracket according to the third embodiment by further including a cup-shaped covering board  45  provided on the upper surface of the bracket substrate  4 . The cup-shaped covering board  45  is connected to the upper surface of the bracket substrate  4  via an adhesive film  46 , and further includes a cup hole  451  corresponding to the position of the blind hole  41 . A diameter of the cup hole  451  is larger than a diameter of the blind hole  41 , with the lead connecting portion  431  being exposed in the cup hole  451  and the positive and negative electrode  42  being covered by the cup-shaped covering board  45 . The cup-shaped covering board  45  may be of a reflection cup shape or a cylindrical shape, and is not limited to the present embodiment. In other embodiments, the upper surface of the cup-shaped covering board  45  may be coated with a black material to increase the contrast ratio. Thus this kind of power LED bracket is particularly applicable to an indoor or outdoor LED display screen. 
     To sum up, the present application overcomes the technical prejudice in the prior art by employing an ordinary insulating board as a substrate for manufacturing a power LED bracket. The present application employs a simple processing method and can achieve a high yield rate. The product manufactured according to the present application has a unique structural design, a low production cost, a high universal applicability, a good heat dissipation effect, can be widely applied, and is applicable to an industrial batch production. In a word, the present application achieves prominent advantageous effects.

Technology Category: 5