Patent Application
20070298630
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
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.
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.
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 10b thereof. Namely, the rest of the surface of the substrate 10 corresponding to the projection 10a thereof is not coated with the resin, by which the projection 10a is left exposed.
Then, the surface of the projection 10a 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.
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.
Then, the surface of the projection 10a, 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 10a by anchor effect. Other methods are substituted for this plating process. Conductive thin film may be applied to the surface of the projection 10a, or a metal terminal may be fitted on the surface thereof.
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 10c consisting of the projection 10a and the plating 2 applied to the surface of the projection 10a is formed, and the connecting member 1 having the substrate 10 shown in
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
An experiment on the peel-resistant force of the adhesive surface according to the present invention is described with reference to
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.
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.
In the above-described embodiment, the circuit portion 10c 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 10b 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.
In the following description, another embodiment is explained with reference to
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 10a for connection is integrally formed on the substrate 10. On the surface of the substrate 10, a circuit portion 10c is formed with the projection 10a and a plating 2 applied to the surface of the projection 10a. The rest of the surface of the substrate 10 is a non-circuit portion 10b.
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.
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.
Then, the entire surface of the substrate 10 is subjected to coarsening (etching) process. The etching process is the same as previously described.
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 10b thereof. Namely, the rest of the surface of the substrate 10 corresponding to the projection 10a thereof is not coated with the resin, by which the projection 10a is left exposed.
Then, the surface of the projection 10a is provided with catalyst such as palladium, gold, or the like. For applying catalyst, well-known method is available.
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.
Then, the surface of the projection 10a, 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 10a by anchor effect. Other methods are substitute for this plating process. Conductive thin film may be applied to the surface of the projection 10a, or a metal terminal may be fitted on the surface thereof.
Finally, the substrate 10 is heated to remove moisture in the structure thereof. Thereby, on the surface of the substrate 10, a circuit portion 10c is formed with the projection 10a and the plating 2 applied to the surface of the projection 10a is formed, and the connecting member 1 having the substrate 10 shown in
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 10c as well as for connecting the non-circuit portion 10b 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.).
For adhering, the anisotropic conductive adhesive films 51 is applied both into a gap between the circuit pattern 31 and the circuit portion 10c and into a gap between the non-circuit portion 10b and the printed circuit board 3, and is heated under pressure.
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.
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 10c are connected to each other in an electrically conductive state by electrically conductive particles. On the other hand, the non-circuit portion 10b 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 10b 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.
Still another embodiment is explained below with reference to
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 10a, 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
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 10b of the substrate 10 and for connecting the circuit pattern 31 of the printed circuit board 3 with the circuit portion 10c. The embodiment is especially applicable to the adhesion of soldering-heat-resistant items such as mounting a connector on a printed circuit board.
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 10c and for connecting the non-circuit portion 10b 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”.
As shown in
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.
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 10c of the substrate 10 so that the adhesive flux component is removed to the outside.
Thereafter, a flux resin component is solidified by a cross-linking reaction to complete the bonding.
Consequently, as shown in
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.
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.
