Patent Publication Number: US-2023164919-A1

Title: Circuit board assemly and method for manufacturing the same

Description:
FIELD 
     The subject matter herein generally relates to circuit boards, in particular, to a circuit board assembly formed by connecting a plurality of circuit boards and a method for manufacturing the circuit board assembly. 
     BACKGROUND 
     Functions of electronic products are always increasing, which leads to the number of circuit boards in the electronic products being increased. These circuit boards need to be electrically connected. The circuit boards are generally connected through a hot bar process. However, the hot bar process includes a reflow soldering process which process is complicated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of embodiment, with reference to the attached figures. 
         FIG.  1    is a cross-sectional view of a double-sided copper clad laminate according to an embodiment of the present disclosure. 
         FIG.  2    is a cross-sectional view showing a through hole formed on the double-sided copper clad laminate of  FIG.  1   . 
         FIG.  3    is a cross-sectional view showing a conductive structure formed in the through hole of  FIG.  2   . 
         FIG.  4    is a cross-sectional view showing conductive wiring layers formed on the double-sided copper clad laminate of  FIG.  3    as a first circuit board. 
         FIG.  5    is a bottom view of the first circuit board of  FIG.  4   . 
         FIG.  6    is a cross-sectional view showing protective layers formed on the conductive wiring layers of  FIG.  4   . 
         FIG.  7    is a bottom view of the first circuit board in  FIG.  6   . 
         FIG.  8    is a bottom view showing the first circuit board of  FIG.  7    having a preset shape. 
         FIG.  9    is a bottom view showing slits formed between first contact pads of the first circuit board of  FIG.  8   . 
         FIG.  10    is a cross-sectional view showing stamped protrusions formed on the first circuit board of  FIG.  9   . 
         FIG.  11    is a cross-sectional view showing a supporting block arranged on the first circuit board of  FIG.  10   . 
         FIG.  12    is a bottom view of the first circuit board in  FIG.  11   . 
         FIG.  13    is a cross-sectional view of a second circuit board according to an embodiment of the present disclosure. 
         FIG.  14    is a bottom view of the second circuit board of  FIG.  13   . 
         FIG.  15    is a cross-sectional view showing two first circuit boards attached to opposite surfaces of the second circuit board. 
         FIG.  16    is a cross-sectional view showing an encapsulation layer formed on the first circuit boards of  FIG.  15    and the second circuit board of  FIG.  15   . 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “substantially” is defined to be essentially conforming to the particular dimension, shape, or other feature that the term modifies, such that the component need not be exact. For example, “substantially cylindrical” means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like. 
     A method for manufacturing a circuit board assembly according to an embodiment includes steps as follows. 
     Step S 1 , referring to  FIG.  1   , a copper clad laminate  10  is provided. The copper clad laminate  10  includes a first insulating layer  11  and a copper layer  12  arranged on the first insulating layer  11 . In this embodiment, the copper clad laminate  10  includes two copper layers  12  which are arranged on opposite surfaces of the first insulating layer  11 . In other embodiments, the copper clad laminate  10  includes only one copper layer  12 . 
     The first insulating layer  11  is made of a flexible insulating material, which is selected from a group consisting of liquid crystal polymer (LCP), poly tetra fluoro ethylene (PTFE), poly ether ether ketone (PEEK), polyphenylene oxide (PPO), polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethylene (PE), and any combination thereof. 
     Step S 2 , referring to  FIG.  2   , a through hole  101  is formed on the copper clad laminate  10 . The through hole  101  penetrates the first insulating layer  11  and the copper layers  12 . In some embodiments, the through hole  101  is formed by mechanical drilling or laser drilling. 
     Step S 3 , referring to  FIG.  3   , a first conductive structure  21  is formed in the through hole  101 . The first conductive structure  21  is coupled to the two copper layers  12 . 
     In this embodiment, a coating is formed on a wall of the through hole  101 , through an electroplating process, to obtain the first conductive structure  21 . It can be understood that when the first conductive structure  21  is formed by electroplating, the coating is also formed on surfaces of the copper layers  12  facing away from the first insulating layer  11 . In other embodiments, the first conductive structure  21  is formed by filling the through hole  101  with conductive materials. 
     Step S 3 , referring to  FIG.  4    and  FIG.  5   , the two copper layers  12  are processed to form two first conductive wiring layers  13 . In some embodiments, the copper layers  12  are processed using a lithography process. The two first conductive wiring layers  13  are coupled through the first conductive structure  21 . 
     One of the first conductive wiring layers  13  includes a plurality of lines  131  and a plurality of first contact pads  132 . The first contact pads  132  are coupled to the lines  131 , respectively. The first contact pads  132  are adjacent to an end of the first insulating layer  11  and are parallel with each other. 
     Step S 4 , referring to  FIG.  6    and  FIG.  7   , two first protective layers  31  are formed on surfaces of the first conductive wiring layers  13  facing away from the first insulating layer  11 , obtaining a first circuit board  40 . The first contact pads  132  are exposed from a first protective layer  31 . 
     The first protective layers  31  are configured to protect the first conductive wiring layers  13 . The first protective layers  31  are cover films which are bonded to the first conductive wiring layers  13  or printed ink layers formed on the first conductive wiring layers  13 . 
     The first circuit board  40  includes a first surface  401  with the first contact pads  132  and a second surface  402  opposite to the first surface  401 . The two first protective layers  31  are respectively located on the first surface  401  and the second surface  402 . 
     Step S 5 , referring to  FIG.  8   , an outline of the first circuit board  40  is cut to remove extra and excess materials, obtaining the circuit board  40  having a preset shape. 
     Step S 6 , referring to  FIG.  9   , a portion of the first circuit board  40  between any two adjacent first contact pads  132  is cut to form a slit  41  which penetrates an end of the first circuit board  40 , to separate the first circuit board  40  into a plurality of portions. Each of the plurality of portions has one first contact pad  132 . The separated portions of the first circuit board  40  having the first contact pads  132  are independent of each other and can be processed separately without interference. 
     Step S 7 , referring to  FIG.  10   , the portions of the first circuit board  40  with the first contact pads  132  are stamped along a direction from the second surface  402  to the first surface  401 , to form a plurality of stamped protrusions  51  being correspondingly positioned relative to positions of the first contact pads  132 . Each first contact pad  132  is outside a stamped protrusion  51 . 
     The stamped protrusions  51  protrude out of the first surface  401 . A plurality of stamped grooves  52  are formed on the second surface  402 , the stamped groove  52  corresponding in position to the stamped protrusions  51 . Each stamped groove  52  has a shape matching that of a corresponding stamped protrusion  51 . In this embodiment, a cross section of each stamped protrusion  51  is arc-shaped. In other embodiments, the cross section of each stamped protrusion  51  can be triangular, rectangular, trapezoidal, etc. It can be understood, each stamped protrusion  51  and the corresponding stamped groove  52  are formed simultaneously during a stamping process. 
     Step S 8 , referring to  FIG.  11    and  FIG.  12   , a supporting block  60  is fixed on the first surface of the first circuit board  40 . Specifically, the supporting block  60  is arranged on one first protective layer  13 . The supporting block  60  is adjacent to the stamped protrusions  51 . A height H 1  of each stamped protrusion  51  is greater than a height H 2  of the supporting block  60 . 
     In some embodiments, an adhesive layer  70  is sandwiched between the supporting block  60  and the first circuit board  40 , the supporting block  60  is bonded to the first circuit board  40  through the adhesive layer  70 . 
     The adhesive layer  70  may include a viscous resin. The viscous resin may be at least one of polypropylene, epoxy, polyurethane, phenolic, urea-formaldehyde, melamine-formaldehyde and polyimide. 
     Step S 9 , referring to  FIGS.  13  and  14   , a second circuit board  80  is provided. The second circuit board  80  includes a second insulating layer  81  and a second conductive wiring layer  83  arranged on the second insulating layer  81 . The second conductive wiring layer  83  includes a plurality of second contact pads  832 . The second contact pads  832  are parallel to each other. 
     In this embodiment, the second circuit board  80  includes two second conductive wiring layers  83  which are arranged on opposite surfaces of the second insulating layers  81 . The two second conductive wiring layers  83  are electrically connected with each other through a second conductive structure  42  which penetrates the second insulating layer  81 . The second conductive structure  42  is a hole which is metallized or a conductive column. In other embodiment, the second circuit board  80  can include only one second conductive wiring layer  83 . 
     The second circuit board  80  further includes two second protective layers  32 . The second protective layers  32  cover surfaces of the second conductive wiring layers  83  facing away from the second insulating layer  81 . The second contact pads  832  of one second conductive wiring layer  83  are exposed from a corresponding second protective layer  32 . The second protective layers  32  are cover films or can be layers of ink. 
     The second insulating layer  81  is rigid. The second insulating layer  81  can be made of a resin material containing glass fibers. 
     In some embodiment, another supporting block  60  is arranged on the second protective layer  32  of the second circuit board  80 . The supporting block  60  on the second circuit board  80  is configured to connect to the supporting block  60  on the first circuit board  40 . In other embodiments, there is only one supporting block  60  arranged between the first circuit board  40  and the second circuit board  80 . 
     Step S 10 , referring to  FIG.  15   , the first circuit board  10  is pressed onto the second circuit board  80 , each first contact pad  132  of one stamped protrusion  51  coming into contact with a corresponding second contact pad  832 . 
     The supporting block  60  is sandwiched between the first circuit board  40  and the second circuit board  80 . Since the height of the stamped protrusion  51  is greater than the height of the supporting block  60 , the stamped protrusion  51  will deform under pressure and its height will be reduced when the first circuit board  40  is pressed onto the second circuit board  80 , thereby the supporting block  60  can make contact with the second circuit board  80 , and an area of contact between the first contact pad  132  and the corresponding second contact pad  832  is thus increased The first contact pad  132  is thus in close contact with the corresponding second contact pad  832  to maintain good conductivity. 
     In some embodiments, another adhesive layer  70  is sandwiched between the supporting block  60  and the second circuit board  80 . The supporting block  60  is bonded to the second circuit board  80  through the adhesive layer  70 . 
     In this embodiment, two first circuit boards  40  are pressed on opposite surfaces of the second circuit board  80 , the stamped protrusions  51  of one first circuit board  40  are in contact with the second contact pads  832  of a corresponding second conductive wiring layer  83 . 
     Step S 11 , referring to  FIG.  16   , an encapsulation layer  90  encapsulating the first contact pads  132  and the second contact pads  832  is formed, obtaining the circuit board assembly. The encapsulation layer  90  further infills gaps between first circuit boards  40  and the second circuit board  80 . The encapsulation layer  90  also acts as a hermetic seal against the air, improving the reliability. 
     The encapsulation layer  90  further covers a portion of a surface of the first circuit board  40  facing away from the second circuit board  80 , a portion of a side face of the first circuit board  40 , a portion of a surface of the second circuit board  80  facing away from the first circuit board  40 , and a portion of a side face of the second circuit board  80 . The encapsulation layer  90  covers corresponding regions of the first circuit board  40  and the second circuit board  80 . 
     The encapsulation layer  90  is made of a non-conductive material. The non-conductive material includes one or more of epoxy molding compound (EMC), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyethylene terephthalate (PET), and other injection molding materials. 
     Referring to  FIG.  16   , a circuit board assembly according to one embodiment is provided. The circuit board assembly includes two first circuit boards  40  and the second circuit board  80 . The first circuit boards  40  are disposed on opposite surfaces of the second circuit board  80 . 
     Each first circuit board  40  includes the first insulating layer  11 , two first conductive wiring layers  13  on opposite surface of the first insulating layer  11 , and two first protective layers  31  on surfaces of the two first conductive wiring layers  13  facing away from the first insulating layer  11 . One first conductive wiring layer  13  of each first circuit board  40  includes the first contact pads  132  which are exposed from the corresponding first protective layer  31 . 
     Each first circuit board  40  defines one slit  41  (shown in  FIG.  9   ) between any two adjacent first contact pads  132 . The slit  41  penetrates an end of the first circuit board  40 . A portion of the first circuit board  40  having the first contact pads  132  is separated into a plurality of portions through a plurality of slits  41 , each of the plurality of portions having one first contact pad  132 . 
     Each first circuit board  40  further includes the first surface  401  and the second surface  402  opposite to the first surface  401 . The first surface  401  defines the stamped protrusions  51  corresponding to the first contact pads  132 , and each first contact pad  132  is outside a stamped protrusion  51 . The second surface  402  defines the stamped grooves  52  having shapes matching the shapes of the stamped protrusions  51 . 
     In other embodiments, the first conductive wiring layer  13  includes only one first contact pad  132 , and the second conductive wiring layer  83  includes only one second contact pad  832 , and there are only one stamped protrusion  51  being correspondingly positioned relative to a position of the first contact pad  132 . 
     The second circuit board  80  includes the second insulating layer  81 , two second conductive wiring layers  83  on opposite surfaces of the second insulating layer  81 , and two second protective layers  32  on surfaces of the two second conductive wiring layers  83  facing away from the second insulating layer  81 . Each second conductive wiring layer  83  includes the second contact pads  832  which are exposed from the corresponding second protective layer  32 . 
     Each first contact pad  132  of the stamped protrusion  51  of one first circuit board  40  is in contact with a second contact pad  832  of one second conductive wiring layer  83 , so that the two first circuit boards  40  are electrically coupled to the second circuit board  80 . 
     In some embodiments, the circuit assembly further includes two supporting blocks  60 , one supporting block  60  is sandwiched between one first circuit board  40  and the second circuit board  80 , and the other supporting block  60  is sandwiched between the other first circuit board  40  and the second circuit board  80 . Each supporting block  60  is adjacent to the stamped protrusions  51  of one first circuit board  40 . 
     In some embodiments, each supporting block  60  is bonded to one first circuit board  40  and the second circuit board  80  by two respective adhesive layers  70 . 
     In some embodiments, the circuit board assembly further includes the encapsulation layer  90 . The encapsulation layer  90  infills gaps between the first circuit boards  40  and the second circuit board  80  and encapsulates and seals the first contact pads  132  and the second contact pads  832 . 
     In the circuit board assembly and the manufacturing method, the first contact pads  132  of the first circuit board  40  are in contact with the second contact pads  832  of the second circuit board  80 , so that electronic connections between the first circuit board  40  and the second circuit board  80  are achieved. Compared with a hot bar process, neither a solder paste nor a reflow soldering process is required, the process is simplified. Moreover, the encapsulation layer  90  encapsulates the first contact pad  132  and the connected second contact pads  832  to seal against the air, improving the reliability. 
     While the present disclosure has been described with reference to particular embodiments, the description is illustrative of the disclosure and is not to be construed as limiting the disclosure. Therefore, those of ordinary skill in the art can make various modifications to the embodiments without departing from the scope of the disclosure as defined by the appended claims.