Abstract:
An apparatus for heating and pressing a printed circuit board includes a first pressing member, a second pressing member, a driving member, a heater and an electromagnetic assembly. The driving member is configured for driving the first pressing member and the second pressing member to move toward or away from each other. The heater is configured for heating one of the first and second walls, and the electromagnetic assembly is capable of generating a magnetic field to attract the second wall to create additional pressure.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to apparatuses and methods for manufacturing a printed circuit board (PCB), and more particularly relates to an apparatus for activating a layer of glue on a PCB and a method using the same. 
         [0003]    2. Description of Related Art 
         [0004]    Many circuit boards comprise a substrate having a pattern of copper conductive tracks formed onto it. The substrate can either be rigid, or flexible. Active and passive electronic components are soldered onto the board via a set of pads arranged around the periphery of a component site. 
         [0005]    In a manufacturing process for a PCB, the copper conductive tracks may be protected from oxidation by coating the circuit board with a film of material. The film includes an insulation layer such as polyimide, and an adhesive layer. The adhesive layer is arranged between the circuit board and the insulation layer. A pressing apparatus comprising an upper hot press plate, and a lower hot press plate is provided. The film is positioned between the upper and lower hot press plates, and then the adhesive layer is melted by the upper and lower hot press plates. Then the lower hot press plate is pushed by a cylinder rod to move close to the upper hot press plate, so as to press the film and the circuit board firmly together. Finally, the adhesive is cured, thereby forming a PCB protected from oxidation. The end of the cylinder rod just contacts the center portion of the lower hot press plate, thus the pressure applied to the center portion of the film is greater than that applied to the surrounding region. Thus some melted material of the adhesive layer will stream from the center region to the surrounding portion, which causes a non-uniform thickness of the adhesive layer. In addition, the surrounding region with dense conductive tracks may not be totally covered or filled with the adhesive material of the adhesive layer because of differences in pressure, thereby forming bubbles on the PCB. Too many bubbles may cause bad adhesion between the circuit board and the protective film. 
         [0006]    What is needed, therefore, is an apparatus for more reliably pressing a PCB and a method using the same. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is a schematic view of an apparatus for pressing a PCB according to an exemplary embodiment, comprising a first pressing member and a second pressing member. 
           [0009]      FIG. 2  is a schematic view of the first pressing member of the apparatus in  FIG. 1 , showing an electromagnetic assembly in the first pressing member. 
           [0010]      FIG. 3  is a flow chart of a method for pressing a PCB using the apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Embodiments will now be described in detail below and with reference to the drawings. 
         [0012]    Referring to  FIGS. 1 and 2 , an apparatus  10  for pressing and heating a PCB according to a first exemplary embodiment includes a supporting member  11 , a first pressing member  12 , a second pressing member  13 , two driving members  14 , a first heater  151 , a second heater  152 , an electromagnetic assembly  16  and a controller  17 . The apparatus  10  presses a PCB  20  and an anti-oxidation protective film (protective film  30 ) together to bond the protective film  30  firmly onto a surface of the PCB  20 . The protective film  30  includes an insulation layer  301  such as polyimide film, and a heat-activated adhesive layer  302  between the PCB  20  and the insulation layer  301 . 
         [0013]    The first pressing member  12  and the driving members  14  are arranged on the support member  11 . The second pressing member  13  is connected to the driving members  14 . The electromagnetic assembly  16  is arranged in the first pressing member  12 . The second pressing member  13  is arranged over the first pressing member  12 . The driving members  14  move the second pressing member  13  up and down, and thereby the first pressing member  12  and the second pressing member  13  may cooperatively render the protective film  30  and the PCB  20  into one unit. The first heater  151  is arranged in the first pressing member  12  and heats the first pressing member  12 , and the second heater  152  is arranged in the second pressing member  13  and heats the second pressing member  13 . The first and second pressing members  12 ,  13  then compress and heat the protective film  30  and the PCB  20  together. The second pressing member  13  includes magnetic material. Thus, the electromagnetic assembly  16  in the first pressing member  12  attracts the second pressing member  13 , so as to compress the PCB  20  and the protective film  30  more firmly. The controller  17  controls the operations of first pressing member  12 , the second pressing member  13 , the driving members  14 , the first heater  151 , the second heater  152  and the electromagnetic member  16 . 
         [0014]    The support member  11  includes a base plate  111  and a support main body  112  arranged on the base plate  111 . The base plate  111  bears the support main body  112 . The support main body  112  has a support surface  1122  facing away from the base plate  111 . 
         [0015]    The first pressing member  12  is rectangular and hollow, and is mounted on the support surface  1122 . The first pressing member  12  includes a first lower wall  1201  contacting the support surface  1122 , and a first upper wall  1202 . The first pressing member  12  includes an effective pressing region  125 , where the PCB  20  and the protective film  30  can be positioned and processed. In this exemplary embodiment, the effective pressing region  125  has an area less than that of the first upper wall  1202 , and is at the center of the first upper wall  1202 . The first pressing member  12  further includes a first sidewall  1203  interconnecting the first lower wall  1201  and the first upper wall  1202 , and a second sidewall  1204  opposite to the first sidewall  1203 . 
         [0016]    The first pressing member  12  defines a receiving cavity  120  therein. The receiving cavity  120  includes a first cavity portion  121  adjacent to the first lower wall  1201 , and a second cavity portion  122  adjacent to the first upper wall  1202 . The first cavity portion  121  and the second cavity portion  122  are partitioned by a thermally insulating board  123 . The first heater  151  is received in the second cavity portion  122 , and heats up the first upper wall  1202  of the first pressing member  12 . The thermally insulating board  123  protects the second cavity portion  122  from the passage of heat generated by the first heater  151 . 
         [0017]    The electromagnetic assembly  16  is received in the first cavity portion  121 . The electromagnetic assembly  16  includes a plurality of electromagnetic units  160  arranged in an array. Each of the electromagnetic units  160  includes an I-shaped magnetic core  161  and an electromagnetic coil  162 . The I-shaped magnetic core  161  includes a first rectangular core plate  1611 , a second rectangular core plate  1612 , and a cylindrical core  1613 . The two ends of the cylindrical core  1613  are connected to the first and second rectangular core plates  1611 ,  1612 . The cylindrical core  1613  is perpendicular to the first and second rectangular core plates  1611 ,  1612 . Each of the first and second rectangular core plates  1611 ,  1612  has a larger area than that of the ends of the cylindrical core  1613 , thereby the first rectangular core plate  1611 , the second rectangular core plate  1612 , and the cylindrical core  1613  cooperatively forming an “I” shape. The electromagnetic coil  162  is wound around the cylindrical core  1613 . In this embodiment, the electromagnetic coils  162  of the plurality of electromagnetic units  160  have a same number of windings. The first core plates  1611  of the plurality of the electromagnetic units  160  are parallel with each other and are arranged side by side, thereby forming a first electromagnetic panel  1601 . The second core plates  1612  of the plurality of the electromagnetic units  160  are parallel with each other and are arranged side by side, thereby forming a second electromagnetic panel  1602 . The first electromagnetic panel  1601  is adjacent to the first upper wall  1202 , and the second electromagnetic panel  1602  is adjacent to the first lower wall  1201 . In this embodiment, the first electromagnetic panel  1601  has an upper surface  165  facing toward the thermally insulating board  123 , and is parallel with the first upper wall  1202 . The surface area of the upper surface  165  is equal to that of the effective pressing region  125 . 
         [0018]    The second pressing member  13  includes a second lower wall  1301 , a second upper wall  1302  opposite to the second lower wall  1301 , a third sidewall  1303  interconnecting the second lower wall  1301  and the second upper wall  1302 , and a fourth sidewall  1304  opposite to the third sidewall  1303 . The second lower wall  1301  is arranged adjacent to the first upper wall  1202 . The surface area of the second lower wall  1301  is equal to that of the first upper wall  1202 , and is aligned with the first upper wall  1202 . The third sidewall  1303  and the first sidewall  1203  are at the same side, and the fourth sidewall  1304  and the second sidewall  1204  are at the same side. The second lower wall  1301 , the second upper wall  1302 , the third sidewall  1303  and the fourth sidewall  1304  cooperatively define a receiving cavity  131 . The second heater  152  is received in the receiving cavity  131 , and heats the second lower wall  1301 . The second lower wall  1301  is comprised of a magnetic material. 
         [0019]    Each of the driving members  14  includes a sliding sleeve  141  and a cylinder rod  142 . The cylinder rod  142  extends out of the sliding sleeve  141  and is slidable in the sliding sleeve  14 . The driving member  14  further includes an air or oil pump (not shown) for pushing and pulling the cylinder rod  142 . The sliding sleeve  141  and the cylinder rod  142  of one driving member  14  are respectively fixed to the first sidewall  1203  and to the third sidewall  1303 , and the sliding sleeve  141  and the cylinder rod  142  of the other driving member  14  are respectively fixed to the second sidewall  1204  and to the fourth sidewall  1304 . When the cylinder rods  142  slide in the sliding sleeves  141 , the second pressing member  13  moves toward or away from the first pressing member  12 . 
         [0020]    The controller  17  is installed on the support main body  112 . The controller  17  includes an interface incorporating buttons, knobs and one or more displays. The controller  17  is operated to control the flow of power in the electromagnetic coils  162 , to control the driving members  14  to move the second pressing member  13 , and to control the first and second heaters  151 ,  152  to heat the first and second pressing members  12 ,  13 . 
         [0021]    The apparatus  10  further includes an outer shield or casing (cover  18 ) enclosing the first pressing member  12 , the second pressing member  13  and the driving member  14 . 
         [0022]    Referring also to  FIG. 3 , a pressing method for pressing the PCB  20  and the protective film  30  firmly together according to a second exemplary embodiment includes the steps below. 
         [0023]    Step  101 , to provide clearance, the second pressing member  13  is driven to move away from the first pressing member  12  by the driving member  14 . 
         [0024]    In step  101 , the driving member  14  can be started by operating the controller  17 . The cylinder rods  142  slides upward to move the second pressing member  13  away from the first pressing member  12  until there is a predetermined distance between the first upper wall  1202  of the first pressing member  12  and the second lower wall  1301  of the second pressing member  13 . 
         [0025]    Step  102 , the PCB  20 , the protective film  30  and a cushion sheet  40  are positioned on the first upper wall  1202 . The adhesive layer  302  of the protective film  30  is in contact with the PCB  20 . 
         [0026]    In step  102 , the PCB  20  and the protective film  30  are positioned in the effective pressing region  125 . The cushion sheet  40  is arranged on the protective film  30 . The cushion sheet  40  can be a polypropylene film or a silica gel sheet. The cushion sheet  40  prevents the PCB  20  from deforming in the following pressing step, and enhances heat dissipation. 
         [0027]    Step  103 , the second pressing member  13  is driven close to the first pressing member  12  until the second lower wall  1301  of the second pressing member  13  contacts the cushion sheet  40 . 
         [0028]    In step  103 , the driving member  14  is started, and the cylinder rod  142  slides downward. The second pressing member  13  moves close to the first pressing member  12  as the cylinder rod  142  slides until the second lower wall  1301  of the second pressing member  13  contacts the cushion sheet  40 . Then, the pressure on the cylinder rod  142  to the second pressing member  13  is removed by turning off the air or oil pump of the driving member  14  and releasing the pressure medium in the driving member  14 . In this situation, the second pressing member  13  rests on the cushion sheet  40  by its own gravity. 
         [0029]    Step  104 , the first heater  151  and the second heater  152  are started to heat the PCB  20  and the protective film  30 . The adhesive layer  302  of the protective film  30  becomes molten and adheres to the PCB  20  by the pressing of the second lower wall  1301  of the second pressing member  13 . 
         [0030]    In step  104 , the first and second heater  151 ,  152  are started by operating the controller  17 . The adhesive layer  301  is heated to softness, and even be molten. 
         [0031]    Step  105 , electric currents are passed through the electromagnetic coils  162  to magnetize the I-shaped magnetic cores  161  for a predetermined duration. A magnetic force is generated between the electromagnetic assembly  16  and the second pressing member  13 , thereby compressing the PCB  20  and the protective film  30  more firmly together. 
         [0032]    In step  105 , the electric power supplied to all the electromagnetic coils  162  is equal, thus resulting in an overall uniformity of pressure between all the surface areas of the first and second pressing members  12 ,  13 . Therefore, a uniform thickness of adhesive can be obtained. The magnetic force between the first pressing member  12  and the second pressing member  13  can be made large enough to ensure the total filling of the adhesive into the surrounding region with the dense conductive tracks of the PCB  20 , thereby preventing the formation of any bubbles in the protective film. The magnetic force can be adjusted by changing the electric current through the electromagnetic coils  162 , and can be also be adjusted to operate in a wave-like manner, by energizing the coils  162  in the center to start and then energizing the next coil(s) towards the outside, so as to provide a wiping or sweeping action to further discourage or remove any bubbles in the adhesive. 
         [0033]    Step  106 , the electric currents through electromagnetic coils  162  are gradually decreased to zero. 
         [0034]    Step  107 , the driving member  14  moves the second pressing member  13  upward, thereby away from the first pressing member  12 , and the PCB assembly is removed. The insulation layer  301  of the protective film  30  acts as a protective film for protecting the copper conductive tracks of the PCB  20  from oxidation. 
         [0035]    In the case of an adhesive which is not activated by heat the first heater  151  or the second heater  152  or both can be omitted. The electromagnetic assembly  16  can be received in the second pressing member  13 . The driving member  14  can also be arranged above the pressing member  13 . Also, the driving member  14  can be any other type of drive which is effective, such as hydraulic drive cylinder. 
         [0036]    While certain embodiments have been described and exemplified above, various other embodiments will be apparent to those skilled in the art from the foregoing disclosure. The present disclosure is not limited to the particular embodiments described and exemplified but is capable of considerable variation and modification without departure from the scope of the appended claims.