Abstract:
A circuit pattern is formed on a printed circuit board, and a plating surface of a projecting stripe on a substrate is connected to the circuit pattern by soldering. Further, adhesive agent is filled in a gap between a coarsened surface of a non-circuit unit and the printed circuit board. When the adhesive agent is filled in the gap, the adhesive agent comes in an uneven portion of the coarsened non-circuit unit and is hardened in the recessed portion, so that a chemical bonding force of the adhesive agent itself and an anchoring effect act. For this reason, a fixing force and the bonding force increase.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a connecting member for surface mounting circuit for mobile phone and the like. 
         [0003]    2. Description of the Related Art 
         [0004]    Previously, for connecting a metal connecting member for surface mounting circuit with a circuit pattern of a main circuit board, soldering of a metal terminal of the connecting member and the circuit pattern provides a sufficient connecting strength. However, recent electronic devices are equipped with multiple functions; mobile phone has such functions as digital camera, Internet tool, GPS apparatus, and television. Electronic devices&#39; multi-functionization and miniaturization causes a need to make both the width of a circuit pattern on a printed circuit board and the pitch between those circuit patterns much narrower into a micron order. In such a situation, the conventional mechanical connection by soldering no longer provides a sufficient connecting strength. Therefore, in recent years, insulating adhesive agent is used for reinforcing the connecting strength. 
         [0005]    The above-mentioned functions such as digital camera, television, GPS, inter-net, and the like are mounted on a small board of the sub-board and made into a module. A connecting member for mounting those functional members on a printed circuit board is connected to the printed circuit board by mechanical bonding with soldering and by chemical bonding with adhesive agent. 
         [0006]    The substrate of the connecting member is made of electrically insulating thermoplastic resin such as liquid crystal polymer, heat-resistant polyamide, or polyphenylene sulfide, and is formed by injection-molding of those resins. However, a property of good adhesion does not belong to any of the liquid crystal polymer, heat-resistant polyamide, and polyphenylene sulfide. 
         [0007]    Further, it is inevitable that portable mobile electronic devices such as mobile phone, portable computer, or digital camera, drop by accident while handled. If a mobile phone drops, weight of its own multiple function module mounted on the sub-board directly hits its own printed circuit board, to break the electric connection between the printed board and the module. 
         [0008]    Facing such a new problem of accidental dropping of the electronic devices, increase of adhesive strength between their connecting member and electronic circuit board is desired to improve their shock resistance level against dropping. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    Therefore, it is an object of the present invention to provide a connecting member for surface mounting circuit board, which improves its shock resistance level against dropping even though the substrate of the connecting member is injection-molded of electrically insulating thermoplastic resin such as liquid crystal polymer, heat-resistant polyamide, or polyphenylene sulfide. 
         [0010]    The first feature of the present invention is to provide a connecting member for surface mounting circuit to be connected with an electronic circuit board by soldering or bonding. The substrate of the connecting member is molded of electrically insulating resin. A circuit portion and a non-circuit portion are formed on the surface of the substrate. The non-circuit portion has a coarsened surface. Adhesive agent is applicable to the coarsened surface. 
         [0011]    The second feature of the present invention is to provide the connecting member for surface mounting circuit according to the first feature thereof, wherein the entire surface of the substrate is coarsened, and the surface of the circuit portion thereof is plated. 
         [0012]    The third feature of the present invention is to provide a connecting member for surface mounting circuit to be connected with an electronic circuit board. The substrate of the connecting member is molded of electrically insulating resin. A circuit portion and a non-circuit portion are formed on the surface of the substrate. The non-circuit portion has a coarsened surface. The electronic circuit board is connected with the non-circuit portion of the substrate, whose surface is coarsened, by using non-conductive adhesive agent that contains electrically conductive particles. Also, the circuit pattern of the electronic circuit board is connected with the circuit portion of the substrate by using the same non-conductive adhesive that contains electrically conductive particles. 
         [0013]    The fourth feature of the present invention is to provide the connecting member for surface mounting circuit according to the third feature thereof, wherein the non-conductive adhesive agent containing electrically conductive particles is an anisotropic conductive adhesive film. 
         [0014]    The fifth feature of the present invention is to provide a connecting member for surface mounting circuit to be connected with an electronic circuit board. The substrate of the connecting member is molded of electrically insulating resin. A circuit portion and a non-circuit portion are formed on the surface of said substrate. The non-circuit portion has a coarsened surface. The electronic circuit board is connected with the non-circuit portion of the substrate, whose surface is coarsened, by using cream soldering agent that also serves as adhesive agent. Also, the circuit pattern of the electronic circuit board is connected with the circuit portion of the substrate by using the same cream soldering agent that also serves as adhesive agent. 
         [0015]    Effect of the present invention is such that only one application of chemical etching to the substrate of the connecting member provides a rigid and tight connection between the connecting member and the electronic circuit board by both plating and adhesive agent, to efficiently prevent peeling by an external impact. Thereby, high productivity and quality improvement is realized. Even if portable mobile devices such as mobile phone drop, the tight and rigid connection between the connecting member and the electronic circuit board prevents or considerably reduces their disconnection. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view of a connecting member; 
           [0017]      FIG. 2  is an enlarged sectional view taken along the line a-a in  FIG. 1 ; 
           [0018]      FIG. 3  is an enlarged sectional view showing a state in which the connecting member is connected to an electronic circuit board; 
           [0019]      FIG. 4  is a perspective view showing an experiment of the present invention; 
           [0020]      FIG. 5  is an enlarged sectional view showing a state in which a connecting member according to another embodiment is connected to an electronic circuit board; and 
           [0021]      FIGS. 6A and 6B  are developments of still another embodiment, in which  FIG. 6A  is a sectional view showing a pre-stage of steps, and  FIG. 6B  is a sectional view showing a post-stage of the steps. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    An embodiment of the connecting member for surface mounting circuit according to the present invention is described below with reference to the accompanying drawings. As shown in  FIGS. 1 and 2 , a connecting member  1  is to be connected with an electronic circuit board  3  by soldering or gluing. A substrate  10  of the connecting member  1  is molded of electrically insulating thermoplastic resin such as liquid crystal polymer, heat-resistant polyamide, or polyphenylene sulfide as the raw material. A projection  10   a  for connection is formed integrally with the substrate  10 . On the surface of the substrate  10 , the projection  10   a  and a plating  2  applied to the surface of the projection  10   a  compose a circuit portion  10   c . The rest of the surface of the substrate  10  is a non-circuit portion  10   b , which is kept coarsened. 
         [0023]    Next, process for manufacturing the substrate  10  of the connecting member  1  is described below. The substrate  10  is molded into a contour corresponding to its finish by injecting a plating-grade liquid crystal polymer into mold cavity. As the liquid crystal polymer, aromatic polyester (“VECTRA” (trade name of Polyplastics Co., Ltd.)) is used. 
         [0024]    Then, the entire surface of the substrate  10  is subjected to coarsening (etching) process. The etching process is conducted by dipping the substrate  10  in an alkaline aqueous solution for a predetermined period of time, e.g. 30 minutes. The alkaline aqueous solution is obtained by solving sodium hydroxide or potassium hydroxide in water at a predetermined concentration, e.g. 45 wt %, and is subsequently heated to a predetermined temperature, e.g. 50 to 90° C. Thereby, the entire surface of the substrate  10  is coarsened. 
         [0025]    Next, the substrate  10  is again inserted into the mold cavity. “ECOMATY AX” (trade name of Nippon Synthetic Chemical Industry Co., Ltd.), an oxyalkylene-group-containing polyvinyl alcohol resin, is injected into the cavity to coat only a portion of the surface of substrate  10  corresponding to the non-circuit portion  10   b  thereof. Namely, the rest of the surface of the substrate  10  corresponding to the projection  10   a  thereof is not coated with the resin, by which the projection  10   a  is left exposed. 
         [0026]    Then, the surface of the projection  10   a  is provided with catalyst such as palladium, gold, or the like. For applying catalyst, any of the well-known methods is available. In one method, the substrate  10  is dipped in mixed catalyst solution of tin- and palladium-base before the substrate  10  is activated by acid such as hydrochloric acid or sulfuric acid. Thereby, palladium is deposited on the surface of the substrate  10 . In another method, relatively strong reducer such as stannous chloride is adsorbed on the surface of the substrate  10 . Then, the substrate  10  is dipped in a catalyst solution that contains noble metal ions such as gold ions at a temperature ranging from 15° C. to 23° C. for 5 minutes. Thereby, gold is deposited on the surface of the substrate  10 . 
         [0027]    Next, the substrate  10  is put in hot water at 60° C. for 10 minutes to heat the substrate  10 , before ECOMATY AX, the coating agent, solves into the hot water. 
         [0028]    Then, the surface of the projection  10   a , which is coarsened in the previous step, is applied with plating  2 . For conducting plating process, either chemical copper plating or chemical nickel plating is available. The plating  2  strongly adheres to the surface of the projection  10   a  by anchor effect. Other methods are substituted for this plating process. Conductive thin film may be applied to the surface of the projection  10   a , or a metal terminal may be fitted on the surface thereof. 
         [0029]    Finally, the substrate  10  is heated to remove moisture in its structure, completing the plating. Thereby, on the surface of the substrate  10 , the circuit portion  10   c  consisting of the projection  10   a  and the plating  2  applied to the surface of the projection  10   a  is formed, and the connecting member  1  having the substrate  10  shown in  FIGS. 1 and 2  is completed. 
         [0030]    Next, process for connecting the substrate  10  of the connecting member  1  to a printed circuit board  3  that serves as electronic circuit board is described. As shown in  FIG. 3 , a circuit pattern  31  is formed on the printed circuit board  3 . The circuit portion  10   c  of the substrate  10  is connected to the circuit pattern  31  by solder  4 . Further, adhesive agent  5  can be applied to the surface of the non-circuit portion  10   b , which is coarsened. More specifically, the adhesive agent  5  is injected into a gap between the non-circuit portion  10   b  and the electronic circuit board  3 . Epoxy adhesive is used for the adhesive agent  5 . When the adhesive agent  5  is injected into the gap, as the non-circuit portion  10   b  is coarsened, the adhesive agent  5  permeates into the uneven portion of the non-circuit portion  10   b , especially the recessed portion thereof, before it stiffens there. Consequently, in addition to the chemical bonding force of the adhesive agent, anchoring effect, i.e. a mechanical and physical anchoring effect, is provided. Thereby, the fixing and bonding force considerably increases to secure sufficient impact-resistant and peel-resistant forces against the external force caused by the electronic devices&#39; dropping or the like. 
         [0031]    An experiment on the peel-resistant force of the adhesive surface according to the present invention is described with reference to  FIG. 4 . A test-piece  6  is adhered to the other test-piece  61  by the adhesive agent  5 . Each test-piece  6 ,  61  is made of previously mentioned “VECTRA” (trade name of Polyplastics Co., Ltd.), and has a width of 10 mm and a thickness of 3 mm. Length of the test-piece  6  is 30 mm while the test-piece  61  is 40 mm. Epoxy adhesive (product number AW106 available from Vantico AG) is used as adhesive agent. Adhering is conducted by heating them at 125° C. for one hour for stiffening. Etching process is conducting by dipping the test pieces in an aqueous solution containing 40 wt % of potassium hydroxide (KOH) for 25 minutes, and heating them at 70° C. for 20 minutes. 
         [0032]    The test pieces on which etching process is conducted and those not subjected to the etching process respectively tensed outward at a tensile speed of 1.7×10 −4  m/s in horizontal directions to compare peel-resistant forces of the adhesive surfaces of the adhesive agents  5  between them. 
         [0033]    The experiment shows that the processed test piece has a peel-resistant force of 15 megapascals (MPs) and that the unprocessed test piece has a peel-resistant force of 5 MPs. It means that the peel-resistant strength of the processed test piece is three times stronger than that of the unprocessed test piece. 
         [0034]    In the above-described embodiment, the circuit portion  10   c  of the substrate  10  is connected to the circuit pattern  31  of the printed circuit board  3  by the solder  4  before the adhesive agent  5  is injected into the gap between the non-circuit portion  10   b  and the electronic circuit board  3  to connect the electronic circuit board  3  and the substrate  10 . Namely, the two steps, i.e., the soldering step and the adhesive-agent-injecting step, are required. 
         [0035]    In the following description, another embodiment is explained with reference to  FIG. 5 . In this embodiment, only one step is required for connecting a circuit pattern  31  of an electronic circuit board  3  to a circuit portion  10   c  of a substrate  10  as well as for connecting a coarsened non-circuit portion  10   b  to the electronic circuit board  3 . 
         [0036]    This embodiment is also to connect a connecting member  1  with a printed circuit board  3  serving as an electronic circuit board as the previous embodiment. A substrate  10  of the connecting member  1  is molded of electrically insulating resin such as electrically insulating thermoplastic resin, and the same raw material is applied as those in the previous embodiment. A projection  10   a  for connection is integrally formed on the substrate  10 . On the surface of the substrate  10 , a circuit portion  10   c  is formed with the projection  10   a  and a plating  2  applied to the surface of the projection  10   a . The rest of the surface of the substrate  10  is a non-circuit portion  10   b.    
         [0037]    Next, process for manufacturing the substrate  10  of the connecting member  1  is described below. The contour of the substrate  10  corresponds to that of its finish. 
         [0038]    The substrate  10  is molded by injecting a plating-grade liquid crystal polymer into mold cavity. Liquid crystal polymer is the same as previously described. 
         [0039]    Then, the entire surface of the substrate  10  is subjected to coarsening (etching) process. The etching process is the same as previously described. 
         [0040]    Next, the substrate  10  is inserted into the mold cavity again. “ECOMATY AX” (the trade name previously described), an oxyalkylene-group-containing polyvinyl alcohol resin, is injected into the cavity to coat only a portion of the surface of the substrate  10  corresponding to the non-circuit portion  10   b  thereof. Namely, the rest of the surface of the substrate  10  corresponding to the projection  10   a  thereof is not coated with the resin, by which the projection  10   a  is left exposed. 
         [0041]    Then, the surface of the projection  10   a  is provided with catalyst such as palladium, gold, or the like. For applying catalyst, well-known method is available. 
         [0042]    Next, the substrate  10  is put in hot water and is heated under the same condition as previously described, before ECOMATY AX, the coating agent, solves into the hot water. 
         [0043]    Then, the surface of the projection  10   a , which is coarsened previously, is applied with plating  2 . For conducting plating process, either chemical copper plating or chemical nickel plating is available. The plating  2  strongly adheres to the surface of the projection  10   a  by anchor effect. Other methods are substitute for this plating process. Conductive thin film may be applied to the surface of the projection  10   a , or a metal terminal may be fitted on the surface thereof. 
         [0044]    Finally, the substrate  10  is heated to remove moisture in the structure thereof. Thereby, on the surface of the substrate  10 , a circuit portion  10   c  is formed with the projection  10   a  and the plating  2  applied to the surface of the projection  10   a  is formed, and the connecting member  1  having the substrate  10  shown in  FIG. 5  is completed. 
         [0045]    Next, process for mounting the substrate  10  of the connecting member  1  onto a printed circuit board  3  that serves as electronic circuit board is described. A circuit pattern  31  is formed on the printed circuit board  3 . One non-conductive adhesive agent containing electrically conductive particles is used for connecting the circuit pattern  31  with the circuit portion  10   c  as well as for connecting the non-circuit portion  10   b  and the non-circuit surface of the printed circuit board  3 . An example of the non-conductive adhesive agents, which contains silver fine particle as the electrically conductive particle, is anisotropic conductive adhesive film  51  (ThreeBond 3370C (trade name) or ThreeBond 3370D (trade name) available from Three Bond Co., Ltd.). 
         [0046]    For adhering, the anisotropic conductive adhesive films  51  is applied both into a gap between the circuit pattern  31  and the circuit portion  10   c  and into a gap between the non-circuit portion  10   b  and the printed circuit board  3 , and is heated under pressure. 
         [0047]    As the anisotropic conductive adhesive film  51  that is used here has the property of going solid at a cure temperature of about 60° C. to 120° C., adhering by use of the anisotropic conductive adhesive film is suitably applied to a portion such as liquid crystal display. Namely, as the electrode of such portion is made of a thin film of ITO (Indium Tin Oxide) having a thickness of several hundred angstroms and is so poor in heat resistance as not to withstand soldering heat, its adhering is conducted by heating and press-bonding under pressure to a temperature not so high as the soldering heat. Heating and press-bonding device is obtained by applying aluminum and silicon rubber to the lower surface of a heated plate. The device pressures the connecting member  1  placed on an operating stand. 
         [0048]    The connection by the anisotropic conductive adhesive film  51  is performed by only one step for heating under pressure. The circuit pattern  31  and the circuit portion  10   c  are connected to each other in an electrically conductive state by electrically conductive particles. On the other hand, the non-circuit portion  10   b  and the non-circuit surface of the electronic circuit board  3  are connected in a non-electrically-conductive state because the electrically conductive particle is suspended in the adhesive agent. As the adhesive agent, an epoxy adhesive is used. When the adhesive agent permeates into the uneven portion of the non-circuit portion  10   b  with the coarsened surface, especially into the recessed portion thereof, and stiffens there, an anchoring effect, i.e. a mechanical and physical anchor effect, is provided in addition to the chemical bonding force of the adhesive agent. Thereby, the fixing force and the bonding force considerably increase to secure a sufficient impact-resistant and peel-resistant forces against the external force caused by fall or the like. 
         [0049]    Still another embodiment is explained below with reference to  FIG. 6 . 
         [0050]    This embodiment also to connect a substrate  10  of a connecting member  1  with a circuit pattern  31  of a printed circuit board  3  serving as an electronic circuit board. The substrate  10  is molded of electrically insulating resin. Of the surface of the substrate  10 , a projection  10   a , i.e. circuit portion of the substrate  10 , is applied with plating  2 . The rest of the surface of the substrate  10  is a non-circuit portion, which is coarsened previously. Those structures and manufacturing processes are the same as the previous embodiments 
         [0051]    The characteristic feature of this embodiment is the use of cream solder  52 , which also serves as adhesive agent, both for connecting the non-circuit surface of the printed circuit board  3  with the non-circuit portion  10   b  of the substrate  10  and for connecting the circuit pattern  31  of the printed circuit board  3  with the circuit portion  10   c . The embodiment is especially applicable to the adhesion of soldering-heat-resistant items such as mounting a connector on a printed circuit board. 
         [0052]    Next, a process is explained, by which the substrate  10  of the connecting member  1  completed in the same way as the previous embodiment is connected with the printed circuit board  3  serving as the electronic circuit board. Cream solder  52 , which also serves as an adhesive agent, is used for connecting the circuit pattern  31  with the circuit portion  10   c  and for connecting the non-circuit portion  10   b  with the non-circuit surface of the printed circuit board  3 . The cream solder  52  is a mixture of solder metal powder and adhesive flux, and its representative product is co-developed by Senju Metal Industry Co., Ltd. and TDK Corporation, sold under the trade name “Under Fill Paste #2000”. 
         [0053]    As shown in  FIG. 6(A) , adhering step is conducted in such a way that the cream solder  52  also serving as an adhesive agent is applied into a gap between the circuit pattern  31  and the circuit portion  10   c  and is heated. However, the adhering step requires no pressurization. Namely, it is conducted without under pressure. 
         [0054]    In the process of coating and heating of the cream solder  52  also serving as an adhesive agent, the viscosity of the adhesive flux contained therein decreases. 
         [0055]    Then, solder particles agglutinate by Van-der-Waals Bonding and the influence of gravity, and inter-metallic bonding occurs between the circuit pattern  31  and the circuit portion  10   c  of the substrate  10  so that the adhesive flux component is removed to the outside. 
         [0056]    Thereafter, a flux resin component is solidified by a cross-linking reaction to complete the bonding. 
         [0057]    Consequently, as shown in  FIG. 6B , the circuit pattern  31  is connected with the circuit portion  10   c  in the state of intermetallic bonding by soldering, by which they are electrically connected with each other on one hand. On the other hand, the non-circuit portion  10   b  having the coarsened surface is connected with the non-circuit surface of the printed circuit board  3  by the adhesive flux resin component as an adhesive agent. By the synergistic effect of those soldering and adhesion, the substrate  10  of the connecting member  1  is mechanically connected to the circuit pattern  31  of the printed circuit board  3  tightly. Particularly, as the adhesive flux resin component permeates into the uneven portion of the non-circuit portion  10   b  with coarsened surface, especially the recessed portion thereof and stiffens there, an anchoring effect, i.e. mechanical and physical anchor effect, is provided in addition to the chemical bonding force of the flux resin. Thereby, the fixing force and the bonding force considerably increase to secure sufficient impact-resistant and peel-resistant forces against the external force caused by fall or the like. 
         [0058]    According to the embodiment, the adhesion by use of the cream solder  52  also serving as an adhesive agent requires only one step, i.e. heating. 
         [0059]    The present invention is applied to connecting members such as a connector mounted on a circuit board for mobile phone, digital camera, notebook personal computer, or the like by soldering and adhesive agent, as the circuit board requires high impact resistance against falling.