Source: http://www.google.com/patents/US20020053468?dq=5,241,671
Timestamp: 2016-02-09 23:34:23
Document Index: 380119054

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Patent US20020053468 - Grounding terminal and mounting structure of the same on a printed circuit board - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsThe present invention realizes proper grounding of a printed circuit board to a grounding conductor by solving the problems in soldering a grounding terminal to a printed circuit board by reflow soldering, relating to a mounting structure of a grounding terminal on a printed circuit board formed by soldering...http://www.google.com/patents/US20020053468?utm_source=gb-gplus-sharePatent US20020053468 - Grounding terminal and mounting structure of the same on a printed circuit boardAdvanced Patent SearchPublication numberUS20020053468 A1Publication typeApplicationApplication numberUS 09/951,672Publication dateMay 9, 2002Filing dateSep 13, 2001Priority dateApr 30, 1998Also published asDE69918489D1, DE69918489T2, EP0954067A2, EP0954067A3, EP0954067B1, US6300579, US6465738, US6674018, US20020062989Publication number09951672, 951672, US 2002/0053468 A1, US 2002/053468 A1, US 20020053468 A1, US 20020053468A1, US 2002053468 A1, US 2002053468A1, US-A1-20020053468, US-A1-2002053468, US2002/0053468A1, US2002/053468A1, US20020053468 A1, US20020053468A1, US2002053468 A1, US2002053468A1InventorsHideo YumiOriginal AssigneeHideo YumiExport CitationBiBTeX, EndNote, RefManReferenced by (5), Classifications (25), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetGrounding terminal and mounting structure of the same on a printed circuit board
US 20020053468 A1Abstract
The present invention realizes proper grounding of a printed circuit board to a grounding conductor by solving the problems in soldering a grounding terminal to a printed circuit board by reflow soldering, relating to a mounting structure of a grounding terminal on a printed circuit board formed by soldering a grounding terminal to the printed circuit board. Two joint surfaces having different surface areas are formed within the joint part of the grounding terminal, and the grounding terminal is soldered to the conductive pattern on the printed circuit board corresponding to the joint surfaces by using the solder having an amount corresponding to the surface area of each joint surface. Also, the bending area as the center of elastic deformation of the contact part of the grounding terminal is formed at a predetermined distance away from the relatively small joint surface of the joint part. Images(7) Claims(11)
BRIEF DESCRIPTION OF THE DRAWINGS [0012] The invention will now be described, by way of example, with reference to the accompanying drawings, in which [0013] [0013]FIG. 1 is a plan view showing the mounting structure of a grounding terminal according to the embodiment of the invention; [0014] [0014]FIG. 2 is a longitudinal sectional view along line II-II of FIG. 1; [0015] [0015]FIGS. 3 and 4 show modifications of the restriction part, respectively, in the invention; [0016] [0016]FIG. 5 is a plan view showing a conventional mounting structure of a grounding terminal on a printed circuit board; and [0017] [0017]FIG. 6 is a longitudinal sectional view along line VI-VI of FIG. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT [0018] As shown in FIG. 2, the grounding structure in the embodiment is formed by soldering a grounding terminal 10 to a printed circuit board 20. The grounding terminal 10 soldered to the printed circuit board 20 is pressed against a grounding conductor 30, thereby ground the printed circuit board 20 to the grounding conductor 30. To illustrate the structure simply, the grounding conductor 30 is not shown in FIG. 1. The grounding conductor 30 may be a chassis or a metal shielding case which covers the printed circuit board 20. [0019] The grounding terminal 10 in the embodiment is formed by bending a strip-like thin sheet metal member. The longitudinal center part of the metal member is a joint part 11, within which the metal member is bent such that the longitudinal section of the metal member forms a trapezoid, in other words, a groove lid is formed on one side of the joint part 11. Two surfaces oppositely positioned across the groove 11 d are joint surfaces 11 a and 11 b. In this case, the groove 11 d is formed at a predetermined distance away from the longitudinal center of the joint part 11, and thus one joint surface 11 a is smaller than the other joint surface 11 b. [0020] The metal member is bent in the upper direction at both ends of the Joint part 11. At one end, the metal member is bent approximately perpendicularly to the joint part 11, and the bent part is further bent approximately perpendicularly so as to form a U-shaped longitudinal section with the joint part 11. Rectangular plate-like parts 14, which arc bent perpendicularly in the direction of the joint part 11, are formed on both sides of the edge of the metal member. Also, projection parts 15 projecting from both sides of the metal member are formed at a predetermined distance away from the edge. The projection parts 15 arc made by being separated from the neighboring member of the same shape when the strip-like thin sheet metal member is stamped out from a sheet metal. [0021] The other end of the metal member is bent at the end of the joint part 11 so as to form a V-shaped longitudinal section. The peak of the V-shaped part has a gently curved longitudinal section instead of an acute one. A part which also has a gently curved longitudinal section from the peak of the V-shape part toward the edge of the metal member forms, together with the V-shaped part, a contact part 12. The part from the end of the contact part 12 to the edge having a straight longitudinal section is bent in the direction of the joint part 11, and forms a restriction part 13. [0022] Once the grounding terminal 10 is soldered and fixed on the printed circuit board, which is then placed in a metal shielding case and the like, the contact part 12 contacts with and is pressed against the grounding conductor 30, thus being elastically deformed around the peak of the above mentioned V-shaped part. [0023] [0023]FIG. 2 shows the state that the contact part 12 is elastically deformed by being pressed against the grounding conductor 30. Two-dot chain line of FIG. 2 shows the state that the contact part 12 is not pressed against the grounding conductor 30. The main function of the plate-like parts 14 is to restrict the movement of the contact part 12 such that the elastic deformation of the contact part 12 is performed without fluctuation. The restoring force caused by the elastic deformation makes the contact part 12 securely pressed against the grounding conductor 30, thereby properly grounding the printed circuit board 20 to the grounding conductor 30. [0024] The mounting structure of the invention is formed by soldering, specifically by reflow soldering, the grounding terminal 10 having the joint part 11, the contact part 12, and the restriction part 13 as above mentioned to the printed circuit board 20. [0025] Specific steps of soldering are explained hereafter. [0026] On the printed circuit board 20 is formed a conductive pattern 21, which corresponds to the joint surfaces 11 a and 11 b configured within the joint part 11 of the grounding terminal 10. Before soldering, creamed solder 22 a and 22 b are applied on the conductive pattern 21 using a known metal mask. The grounding terminal 10 is temporarily fixed to a prescribed position on the printed circuit board 20 by taking advantage of adhesion of the creamed solder applied on the conductive pattern 21 of the printed circuit board 20. Then the printed circuit board 20, on which the grounding terminal 10 is temporarily fixed, is heated in a reflow furnace to allow the aforementioned creamed solder 22 to be melted, and the soldering steps end. The above reflow soldering is automatically performed, by means of total heating such as infrared heating, latent heating of vaporization, hot air circulation heating, and hot plate heating, and local heating using a heating tool, a light beam, a laser beam, and an air heater. Since reflow soldering is known, a detailed explanation of it is omitted. [0027] The aforementioned grounding structure according to the embodiment of the invention has particular advantages in the process of reflow soldering as explained below. To make the explanation easy to understand, problems in a conventional grounding structure are firstly clarified. [0028] In a conventional grounding structure shown in FIG. 6, there are the following problems in soldering the grounding terminal 10 to the printed circuit board 200 by reflow soldering. [0029] (A) The grounding terminal 100 is moved to the right position by self-alignment effect caused by the melted solder, and then is fixed at the position by hardening of the melted solder In this case the grounding terminal 100 may deviate, during the hardening process, from the right position on the printed circuit board 200 because of vibration and the like. In the case where the grounding terminal deviates from the right position, the contact part 102 cannot be appropriately pressed against the grounding conductor 300, and also the requirements of highly precise mounting performance to allow high density mounting cannot be satisfied. [0030] (B) When the temperature of the grounding terminal 100 reaches the melting point of the solder earlier than the conductive pattern 201 of the printed circuit board 200, what is called wicking phenomenon occurs. Wicking phenomenon, here, means a phenomenon that the solder 202 is sucked up along the bending area γ forming the center of elastic deformation of the contact part 102 shown in FIG. 6. In this case, since the solder 202 adheres and hardens around the bending area the elastic deformation performance of the contact part 102 is lowered, and thus it is sometimes impossible to attain elastic deformation enough for the contact part 102 to be pressed against the grounding conductor 300 and conduct electricity to the grounding conductor 300. [0031] In contrast, in the grounding structure according to the embodiment of the invention, two joint surfaces 11 a and 11 b having different surface areas are formed within the joint part 11 of the grounding terminal 10. As a result, the creamed solder 22 a applied on the relatively small joint surface 11 a hardens earlier than the creamed solder 22 b applied on the relatively large joint surface 11 b, when the printed circuit board 20 is cooled after the grounding terminal 10 is moved to the right position on the printed circuit board 20 by self-alignment effect caused by the surface tension of the melted creamed solder 22 a and 22 b. Accordingly, once the creamed solder 22 a applied on the smaller joint surface 11 a hardens, the grounding terminal 10 does not deviate from the right position on the printed circuit board 20 because of vibration and the like. This reduces the possibility of the grounding terminal 10 deviating from the right position on the printed circuit board 20 while cooling the printed circuit board 20, and thus has solved the problems mentioned in (A). Namely, the possibility of the contact part 12 not being appropriately pressed against the grounding conductor 30 is reduced, and also the requirements of highly precise mounting performance to allow high density mounting are satisfied. [0032] Another advantage is as follows: in the case where two joint surfaces 11 a and 11 b having different surface areas are formed within the joint part 11 of the grounding terminal 10, when the printed circuit board 20 with the grounding terminal 10 at the prescribed position thereon is heated in a reflow furnace, the solder 22 a applied on the relatively small joint surface 11 a is melted earlier than the solder 22 b applied on the relatively large joint surface 11 b. This may result in what is called tombstone phenomenon (Manhattan phenomenon), which means, in this case, the grounding terminal 10 is made to erect because of the surface tension of the melted solder. However, in the embodiment of the invention, the creamed solder 22 a and 22 b, which is a paste mixture of powdered solder and a vehicle, is employed. As a result, there is a strong possibility that the adhesion of the creamed solder offsets the force to detach the joint surface 11 b from the conductive pattern 21 on the printed circuit board 20 caused by the surface tension of the previously melted solder. Moreover, in the embodiment of the invention, since the size of the joint surfaces of 11 a and 11 b is different, the adhesion of the creamed solder 22 b on the larger joint surface 11 b is probably stronger than the force to detach the joint surface 11 b caused by the surface tension of the melted creamed solder 22 a on the smaller joint surface 11 a. Thus tombstone phenomenon is prevented effectively. [0033] A further advantage is as follows: in the mounting structure of the embodiment, the bending area γ is formed at a predetermined distance away from the relatively small joint surface 11 a of the joint part 11. As a result, since the creamed solder 22 a applied on the smaller joint surface 11 a is not sucked up, by wicking phenomenon, to the bending area γ of the contact part 12, the solder 22 a does not adhere around the bending area γ. This prevents the elastic deformation performance of the contact part 12 from declining because of the solder adhering around the bending area γ. Thus, the aforementioned problem (B) is solved and the contact part 12 is appropriately pressed against the grounding conductor 30. [0034] The mounting structure of the embodiment provides another advantage as follows: a restriction part 13 adjacent to the contact part 12 of the grounding terminal 10 is formed so that the stress caused to the contact part 12 by the elastic deformation thereof will not exceed the elastic limit. When the contact part 12 is elastically deformed to a predetermined extent, the restriction part 13 restricts the elastic deformation by contacting and pressing its edge to a surface 11 c on the reverse side of the joint surface 11 b of the joint part 11. The predetermined extent means the extent of elastic deformation which does not allow the stress caused to the contact part 12 to exceed the elastic limit. This prevents a permanent deformation of the contact part 12 even though a heavy load is applied thereto. Although the restriction part 13 is formed adjacent to the contact part 12 of the grounding terminal 10 in FIG. 2, it may be possible to form a restriction part on the reverse side of the joint surfaces 11 a and 11 b of the joint part 11 as shown in FIG. 3 and 4 such that the restriction part is pressed against the contact part 12 In a modification shown in FIG. 3, a member 16 is formed as part of the metal member such that the member 16 extends from a side end of the top surface of the above mentioned trapezoid part and bent in the upper direction, allowing the top edge of the member 16 to function as a restriction part. In a modification shown in FIG. 4, the trapezoid part of FIG. 2 is redesigned to have a significant elevation, and the trapezoid part 17 functions as a restriction part. [0035] As described above, the mounting structure of the embodiment have solved the problems in soldering the grounding terminal 10 to the printed circuit board 20 by reflow soldering, ensuring that the printed circuit board 20 is properly grounded to the grounding conductor 30. [0036] The invention is not restricted to the embodiment and may be embodied in various forms without departing from the spirit and the scope of the invention. [0037] For example, in the mounting structure of the embodiment, two joint surfaces 11 a and 11 b having different surface areas, respectively, are formed within the joint part 11 of the grounding terminal 10. However, when a grounding terminal having a joint part, within which three or more joint surfaces are formed, is soldered to a printed circuit board, only one of the joint surfaces needs to be smaller than the others. [0038] Also, in the mounting structure of the embodiment, the creamed solder 22 a and 22 b is applied to both of the two joint surfaces 11 a and 11 b formed within the joint part 11 of the grounding terminal 10. However, in order to prevent tombstone phenomenon, only the solder applied on the larger joint surface 11 b needs to be creamed solder 22 b. In other words, to prevent tombstone phenomenon, the adhesion on the larger joint surface 11 b is necessary to resist against the surface tension of the solder which is melted first on the smaller joint surface 11 a. Referenced byCiting PatentFiling datePublication dateApplicantTitleUS6986669Mar 5, 2004Jan 17, 2006Kitagawa Industries Co., Ltd.Electrically conductive contact member for a printed circuit boardUS9179530Jul 1, 2011Nov 3, 2015Thomson LicensingSystem for grounding in an electronic deviceCN103081577A *Jul 1, 2011May 1, 2013汤姆森特许公司A system for grounding in an electronic deviceEP1455416A1 *Mar 5, 2004Sep 8, 2004Kitagawa Industries Co., Ltd.Contact memberWO2012001161A1 *Jul 1, 2011Jan 5, 2012Thomson LicensingA system for grounding in an electronic device* Cited by examinerClassifications U.S. Classification174/261International ClassificationH01R4/64, H01R4/48, H05K7/14, H01R4/02, H05K1/18, H01R12/36, H05K7/02, H01R43/02, H05K3/34, H01R13/24Cooperative ClassificationY02P70/611, Y02P70/613, H05K2201/09663, H05K3/341, H05K2201/1031, H05K1/0215, H01R13/24, H01R9/091, H01R4/64, Y10T29/49149, H01R43/0256European ClassificationH05K1/02C1, H05K3/34C, H01R9/09BLegal EventsDateCodeEventDescriptionJul 6, 2007FPAYFee paymentYear of fee payment: 4Jul 6, 2011FPAYFee paymentYear of fee payment: 8Apr 17, 2014ASAssignmentOwner name: KITAGAWA INDUSTRIES CO., LTD., JAPANFree format text: ADDRESS CHANGE;ASSIGNOR:KITAGAWA INDUSTRIES CO., LTD.;REEL/FRAME:032707/0316Effective date: 20140411Aug 14, 2015REMIMaintenance fee reminder mailedRotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services