Patent Publication Number: US-2019198204-A1

Title: Method for making resistors

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Invention Patent Application No. 106145678, filed on Dec. 26, 2017. 
     FIELD 
     The disclosure relates to a method for making resistors, more particularly to a method for making resistors involving the use of laser. 
     BACKGROUND 
     Referring to  FIG. 1 , a resistor  1  includes a resistor wire  11 , an upper part  12  connected to an upper surface of the resistor wire  11 , an identification code  13  formed on the upper part  12 , a bottom part  14  connected to a bottom surface of the resistor wire  11 , and two terminal electrodes  15  formed on two opposite sides of the resistor wire  11 . The resistor wire  11  is formed by cutting a metal plate, and provides a predetermined resistance value. The upper and bottom parts  12 ,  14  are made of electrically insulating materials and protectively cover the resistor wire  11 , such that the resistor wire  11  is electrically insulated from its surroundings. The identification code  13  is formed by printing, and provides information about the resistor such as resistance value thereof, model number thereof, etc. After the resistor  1  is soldered to a circuit board (not shown in figures) via the terminal electrodes  15  and forms a part of an electrical circuit of the circuit board, the resistor wire  11  provides the predetermined resistance value to the electrical circuit. The resistance value may depend on the shape of the resistance wire  11  and the resistance coefficient of the material of the resistance wire  11 . Because the resistor  1  has a simple structure and is easy to produce, and has characteristics such as small size, high precision and reliability, and being non-inductive in practical circuitry applications, it has been widely used as a passive component in electrical machines and devices. 
     Referring to  FIG. 2 , a conventional method of making resistors includes steps  21  to  26 . 
     In step  21 , a protective layer is formed on a front surface of the metal plate. In step  22 , a rear surface of the metal plate opposite to the front surface is cut to form a plurality of the resistor wires  11  spaced apart from each other. In step  23 , an electrical insulating material is printed on the rear surface of the metal plate to form a plurality of spaced-apart bottom row parts. Each of the bottom row parts covers a portion of a respective row of the resistor wires  11 , such that each of the resistor wires  11  defines two opposite electrode forming regions exposed from the bottom row part. In step  24 , identification code  13  is printed onto each of the resistor wires  11  by screen-printing. In step  25 , the protective layer, the bottom row parts, and the metal plate are punched with respect to each of the resistor wires  11  to obtain a plurality of pre-formed resistors, the protective layer and the bottom row parts respectively forming a plurality of the upper parts  12  and a plurality of the bottom parts  14 . In step  26 , each of the pre-formed resistors is electroplated to form the two terminal electrodes  15  on the electrode forming regions to complete the making of the resistor  1 . 
     The conventional method of making the resistor  1  may be applied for mass production of the resistor  1 . However, with increasing demands in miniaturization of passive components with a high dimensional precision, the conventional method for making the resistor  1  needs to be improved for the following reasons: screen-printing the identification code  13  on the upper part  12  of the small-sized resistor  1  using oil-based ink is difficult to perform, and punching the protective layer and the bottom row parts does not achieve a sufficient level of precision. 
     SUMMARY 
     Therefore, the object of the disclosure is to provide a method for making resistors that can alleviate at least one of the drawbacks of the prior art. 
     According to the disclosure, the method for making resistors includes:
         forming a protective layer on a front surface of a metal plate, the protective layer being made of a first electrically insulating material;   patterning a rear surface of the metal plate to form a plurality of spaced-apart resistor wires;   forming a plurality of bottom parts on the rear surface of the metal plate, each of the bottom parts covering a portion of a respective one of the resistor wires such that the respective resistor wire defines two opposite electrode forming regions that are exposed from the bottom part, the bottom parts being made of a second electrically insulating material;   laser-marking the protective layer to form a plurality of identification codes, each of which corresponds in position to a respective one of the resistor wires;   laser-cutting the protective layer and the metal plate to form a plurality of spaced-apart pre-formed resistors, each of which includes an upper part defined by the protective layer, a respective one of the identification codes marked on the protective layer, a respective one of the resistor wires, and the respective bottom part covering the resistor wire; and   forming two terminal electrodes respectively on the two opposite electrode forming regions of each of the resistor wires.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic view of a conventional resistor; 
         FIG. 2  is a flow chart showing a conventional method of making the conventional resistors; 
         FIG. 3  is a flow chart showing an embodiment of a method of making resistors according to this disclosure; 
         FIG. 4  is a schematic view of the resistor made by the embodiment; 
         FIG. 5  is a fragmentary schematic view illustrating formation of a protective layer on a metal plate; 
         FIG. 6  is a fragmentary schematic view illustrating patterning of a rear surface of the metal plate; 
         FIG. 7  is a fragmentary schematic view illustrating formation of a plurality of bottom parts on the rear surface of the metal plate; 
         FIG. 8  is a fragmentary schematic view illustrating laser-marking of the protective layer to form a plurality of identification codes; and 
         FIG. 9  is a close-up view of  FIG. 8 , illustrating removal of a portion of the protective layer. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 4 , a resistor  4  made by a method according to this disclosure is shown to be structurally similar to a resistor produced by a conventional method, and includes a resistor wire  41 , an upper part  42  connected to an upper surface of the resistor wire  41 , an identification code  43  formed on the upper part  42 , a lower part  44  connected to a lower surface of the resistor wire  41 , and two terminal electrodes  45  formed on two opposite sides of the resistor wire  41 . The difference between the resistor produced by the conventional method and the resistor  4  of the present disclosure is that, the identification code  43 , and the upper and bottom parts  42 ,  44  are formed using lasers, allowing the resistor  4  to have smaller size and higher precision. 
     Referring to  FIG. 3 , an embodiment of the method for making a plurality of the resistors  4  according to this disclosure includes steps  31  to  36 . 
     Referring to  FIGS. 3 and 5 , in step  31 , a protective layer  52  is formed on a front surface  511  of a metal plate  51 . The protective layer  52  is made of a first electrically insulating material. In this embodiment, the first electrically insulating material is selected from polyimide and photosensitive insulating ink, and is formed on the front surface  511  by hot-pressing (in the case of polyimide) or printing (in the case of photosensitive insulating ink). The metal plate  51  may be made of a manganese copper nickel alloy, a manganese copper tin alloy, an iron chromium aluminum alloy, a nickel chromium copper aluminum alloy, or combinations thereof. 
     Referring to  FIGS. 3 and 6 , in step  32 , a rear surface  512  of the metal plate  51  is patterned to form a plurality of the resistor wires  41 , which are spaced apart from each other. In this embodiment, photolithography and etching techniques are used for patterning the rear surface  512  of the metal plate  51 . 
     Referring to  FIGS. 3 and 7 , in step  33 , a plurality of the bottom parts  44  are formed on the rear surface  512  of the metal plate  51 . Each of the bottom parts  44  covers a portion of a respective one of the resistor wires  41  such that the respective resistor wire  41  defines two opposite electrode forming regions  53  that are exposed from the bottom part  44 . The bottom parts are made of a second electrically insulating material. In this embodiment, the second electrically insulating material is selected from photosensitive insulating ink and printing insulating ink, and the bottom parts  44  are formed by printing on the rear surface  512 . Further processing may be conducted on the resistor wires  41  based on practical requirements. For example, a test (e.g., resistance value test) may be conducted on the resistor wires  41 . For the resistor wire  41  that fails the test, the respective one of the bottom parts  44  is removed to expose the resistor wire  41 , and then the respective resistor wire  41  is reformed, followed by reconstructing the respective one of the bottom parts  44 . Such a test may improve a yield of the resistor  4 . 
     Referring to  FIGS. 3, 4, and 8 , in step  34 , the protective layer  52  is laser-marked to forma plurality of the identification codes  43 . Each of the identification codes  43  corresponds in position to a respective one of the resistor wires  41 . 
     In step  35 , the protective layer  52  and the metal plate  51  are laser cut to form a plurality of spaced-apart pre-formed resistors  6  (see  FIG. 8 ). Each of the pre-formed resistors  6  includes the upper part  42  defined by the protective layer  52 , a respective one of the identification codes  43  marked on the protective layer  52 , a respective one of the resistor wires  41 , and the respective bottom part  44  covering the resistor wire  41 . In certain embodiments, as further shown in  FIG. 9 , a portion of the upper part  42  of one of the pre-formed resistors  6  is removed such that the resistor wire  41  of the one of the pre-formed resistor  6  defines an electrode forming upper region  54  that is exposed from the upper part  42 . In certain embodiments, after formation of the identification codes  43 , removal of the portion of the upper part  42  of the pre-formed resistor  6  is performed, followed by laser-cutting of the protective layer  52  and the metal plate  51 . 
     In this embodiment, laser with 3%-10% of maximum power and a speed of 300-500 mm/second is used to form the identification codes  43 , laser with 60%-90% of maximum power and a speed of 50 to 100 mm/second is used to remove the portion of the upper part  42 , and laser with 40%-60% of maximum power and a speed of 40 to 60 mm/second is used to cut the protective layer  52  and the metal plate  51 . It should be noted that the laser power may be adjusted based on practical requirements. In certain embodiments, the bottom parts  44  may be laser cut to change the dimensions of the electrode forming regions  53  of each of the resistor wires  41 . 
     In step  36 , the terminal electrodes  45  are respectively formed on the two opposite electrode forming regions  53  of each of the resistor wires  41 . In certain embodiments, one of the terminal electrodes  45  is then connected to the electrode forming upper region  54 . 
     In sum, by virtue of the method for making resistors of this disclosure, the laser is used not only to form the identification codes  43 , but also to remove a portion of the upper part  42  and to cut the metal plate  51  and the protective layer  52  so as to obtain the plurality of the pre-formed resistors  6 . Therefore, in view of miniaturization trends of electrical passive components with high dimensional precision, mass production of the resistors  4  having miniaturized size with the identification codes  43  precisely marked can be accomplished. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. 
     While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment 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.