Surface-mounted type connector and method for producing circuit device including the same

[0002] This application is based upon and claims the benefit of Japanese Patent Applications No. 11-70108 filed on Mar. 16, 1999, and No. 11-298736 filed on Oct. 20, 1999, the contents of which are incorporated herein by reference.

[0003] 1. Field of the Invention

[0004] This invention relates to a surface-mounted type connector and to a method for producing a circuit device including the surface-mounted type connector, which is generally used for an automotive electronic control unit.

[0005] 2. Description of the Related Art

[0006] There are various kinds of structures for surface-mounting connectors used for electronic control units. For example, JP-A-9-326269 discloses a structure (a) in which a connector terminal is soldered to a printed circuit board by solder paste disposed between the printed circuit board and the connector terminal. JP-A-10-172620 discloses a structure (b) in which a connector terminal holding solder balls thereon undergoes a reflow treatment and is soldered to a printed circuit board by the solder balls. JP 2792958 discloses a structure (c) in which a connector terminal is connected to a printed circuit board by soldering through a flexible member.

[0007] In the structures (a) and (b), however, the connector terminal is mounted on the printed circuit board directly by soldering. Therefore, the soldered portions directly receive stresses generated such as when an opposite connector is attached or detached and when vibrations occur. As a result, the soldered portions may be separated from each other. In the structure (c), it is difficult to accurately position the flexible member with respect to the printed circuit board, and to keep the state of the positioned flexible member for soldering due to its flexibility.

[0008] The present invention has been made in view of the above problems. An object of the present invention is to provide a surface-mounted type connector capable of being mounted on a printed circuit board with high mounting workability and high reliability of soldered portions. Another object of the present invention is to provide a method for producing a circuit device including the surface-mounted type connector with high mounting workability and high reliability of soldered portions.

[0009] According to a first aspect of the present invention, a lead terminal protruding from a connector body is fixed to a flexible member and is electrically connected to a conductive path on the flexible member. The flexible member has a specific portion for being soldered to a member such as a printed circuit board. The specific portion has a through hole, and an extending portion protruding from the connector body is inserted into the through hole.

[0010] According to a second aspect of the present invention, a circuit device is produced as follows. Specifically, a lead terminal of a connector body is fixed to a first portion of a flexible member so that the lead terminal is electrically connected to a conductive path on the first portion. The flexible member has a second portion extending from the first portion and having a through hole, and an extending portion extending from the connector body is inserted into the through hole. Then, the connector body is fixed to a printed circuit board, and the conductive path on the flexible member is electrically connected to a wiring pattern on the printed circuit board.

[0011] Accordingly to the present invention described above, the flexible member can be positioned readily and accurately by inserting the extending portion of the connector body into the through hole of the flexible member. The mounting workability for mounting the connector body to the printed circuit board can be improved. Further, the wiring pattern on the printed circuit board and the lead terminal of the connector body is electrically connected to each other through the conductive path on the flexible member. Therefore, the soldered portions of the flexible member and the printed circuit board are not easily separated from each other by externally applied stresses, resulting in high reliability of the soldered portions. Even when the number of the lead terminal of the connector body is increased, a pitch of the conductive path on the flexible member can be increased, resulting in improved yield of soldering.

[0012] Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings, in which;

[0013] FIG. 1 is a cross-sectional view showing a circuit device including a surface-mounted type connector in a first preferred embodiment of the present invention;

[0014] FIG. 2 is a cross-sectional view taken along a line II—II line in FIG. 1;

[0015] FIG. 3 is a cross-sectional view showing a circuit device including a surface-mounted type connector in a second preferred embodiment of the present invention; and

[0016] FIG. 4 is a plan view showing the circuit device in a direction indicated by an arrow IV in FIG. 3.

[0017] (First Embodiment)

[0018] A first preferred embodiment of the present invention is explained with reference to appended drawings below. A surface-mounted type connector in the present embodiment is used for a circuit device of an automotive electronic control unit. The connector is a multi-way type and complies with improved functionality of the electronic control unit.

[0019] Referring to FIG. 1, the connector has a connector body 1 made of resin and shaped into a rectangular box. The connector body 1 is open at a right side in FIG. 1 to detachably receive an opposite connector G in a direction indicated by an arrow in FIG. 1. Plural connection terminals 2 for external connection are disposed within the connector body 1, and plural lead terminals 3 extend from the respective connection terminals 2. The lead terminals 3 are taken out from the connector body 1.

[0020] The connector body 1 integrally has several leg portions 4 as extending portions at a bottom wall thereof, and is fixed to a printed circuit board 5 by the leg portions 4. Specifically, two or three leg portions 4 are disposed in a longitudinal direction of the connector body 1 (in a direction perpendicular to the paper space of FIG. 1). Each of the leg portions 4 has a screw hold 4a.The printed circuit board 5 has holes 5aat portions corresponding to the leg portions 4. The connector body 1 is fixed to the printed circuit board 5 by inserting screws 6 into the screw holes 4aof the leg portions 4 through the holes 5aof the printed circuit board 5.

[0021] A flexible member 7 is a film plate made of, for example, polyimide resin. A copper foil is adhered to the film plate, and is etched into a specific shape. Accordingly, conductive paths having the specific shape are formed on the flexible member 7. Plural through holes 8 are formed in the flexible member 7, and the lead terminals 3 are inserted into the through holes 8, respectively. The lead terminals 3 are fixed to the flexible member 7 by soldering.

[0022] The flexible member 7 is further fixed to the printed circuit board 5 with a ball grid array (BGA) form. Specifically, the flexible member 7 has a free end portion extending downwardly from the portion where the lead terminals 3 are soldered, and the free end portion is bent to be disposed between the bottom wall of the connector body 1 and the printed circuit board 5. The flexible member 7 is soldered to the printed circuit board 5 by solder balls 9, which are arranged into a latticed shape between the flexible member 7 and the printed circuit board 5. Accordingly, the conductive paths of the flexible member 7 are electrically connected to a wiring pattern on the printed circuit board 5. The solder balls 9 are disposed on the copper pattern forming the conductive paths of the flexible member 7, and are welded onto the printed circuit board 5 by a reflow treatment.

[0023] The flexible member 7 has through holes 10, and the leg portions 4 of the connector body 1 are inserted into the through holes 10. Referring to FIG. 2 showing a cross-section taken along a line II—II in FIG. 1, the leg portions 4 are provided at two portions close to both ends of the connector body 1 in the longitudinal direction. The through holes 10 are formed to correspond to the positions and dimensions of the leg portions 4. Each of the through holes 10 has a diameter slightly larger than an outer diameter of each of the leg portions 4 to define a clearance of, for example, approximately 0.1 mm.

[0024] A method for producing the circuit device described above is explained below. First, the connector body 1 assembled with the lead terminals 3, the flexible member 7 holding the solder balls 9 with a specific pattern, and the printed circuit board 5 are prepared, respectively. The lead terminals 3 protruding from the connector body 1 are inserted into the through holes 8 of the flexible member 7, and the lead terminals 3 are fixed to the flexible member 7 by soldering. Next, the free end portion of the flexible member 7 is bent toward the bottom wall of the connector body 1, and the leg portions 4 are inserted into the through holes 10 provided in the free end portion.

[0025] In this state, the leg portions 4bare disposed on the printed circuit board 5. The screws 6 are screwed into the screw holes 4athrough the holes 5a,so that the connector body 1 are screwed to the printed circuit board 5. The free end portion of the flexible member 7 is positioned by the screw fixation step described above, and accordingly, the solder balls 9 are positioned with respect to the wiring pattern on the printed circuit board 5 at high accuracy. After that, the flexible member 7 is soldered to the printed circuit board 5 by performing a soldering reflow treatment, thereby completing the circuit device shown in FIG. 1.

[0026] According to the present embodiment described above, the following effects can be provided.

[0027] (1) The through holes 10 are formed in the flexible member 7 at portions close to the soldered portions (BGA portions) of the flexible member 7, and the leg portions 4 of the connector body 1 is inserted into the through holes 10 of the flexible member 7. Accordingly, the positioning of the soldered portions (BGA portions) of the flexible member 7 can be performed readily and accurately, and the mounting workability for mounting the connector body 1 to the printed circuit board 5.

[0028] (2) The connector body 1 is electrically connected to the printed circuit board 5 through the flexible member 7. The soldered portions (BGA portions) do not receive directly a stress generated when the opposite connector G is attached to or detached from the connector body 1, and a stress generated by vibrations and the like. As a result, the reliability of the soldered portions is improved. In practice, the soldered portions are hardly separated from each other even in cases where the connector is automatically detached when the electronic control device is checked, vibrations occur when the circuit device is mounted on a vehicle, and the like.

[0029] (3) Because the flexible member 7 is positioned utilizing the leg portions 4 of the connector body 1, it is not necessary to use additional members for the positioning, resulting in the simplified structure of the circuit device.

[0030] (4) The BGA form is adopted to solder the flexible member 7 and the printed circuit board 5 together. Therefore, even when the conductive paths are formed on the flexible member 7 with a decreased pitch to be used for a multi way connector, the yield of soldering is elevated. Further, the BGA form improves a self-alignment performance when mounting, and can absorb a positional deviation to some extent occurring when the connector body 1 is screwed to the printed circuit board 5. Furthermore, the mounting workability of the connector body is easy even when the number of the lead terminal is increased, because the pitch of the solder balls 9 arranged into a latticed shape needs not be increased.

[0031] (5) The leg portions 4 provided at the portions close to both ends in the longitudinal direction of the connector body 1 can prevent distortion of the connector body 1 and the printed circuit board 5 when there is a difference in thermal expansion coefficient between the connector body 1 and the printed circuit board 5. Therefore, the soldered portions are not easily separated from each other by the thermal distortions even when the automotive electronic control unit including the circuit device in the present embodiment is operated under harsh environment accompanied by a large change in temperature.

[0032] (Second Embodiment)

[0033] A second preferred embodiment of the present invention is explained focusing on differences from the first embodiment. In the second embodiment, the same parts and components as those in the first embodiment are assigned to the same reference numerals.

[0034] Referring to FIGS. 3 and 4, the free end portion of the flexible member 7 extending downward from the joining portion with the lead terminals 3 is bent along the printed circuit board 5, and is fixed to the printed circuit board 5 at an opposite side of the connector body 1 with the BGA form. The conductive paths of the flexible member 7 and the wiring pattern of the printed circuit board 5 are electrically connected to each other through the solder balls 9 arranged into a latticed shape between the flexible member 7 and the printed circuit board 5 as in the first embodiment.

[0035] Two stays 11 attached to the connector body 1 and extending therefrom position the free end portion of the flexible member 7. Specifically, as shown in FIG. 4, the connector body 1 has two recesses 12, and base end portions of the stays 11 are fitted in the recesses 12, respectively. Front end portions of the stays 11 extend to face both sides of the flexible member 7. The front end portions of the stays 11 have positioning pins 13, respectively, and the positioning pins 13 are inserted into through holes 14 provided in the flexible member 7. Each of the through holes 14 has a diameter slightly larger than the outer diameter of the pins 13 so that a specific clearance (for example, 0.1 mm) is defined between each through hole 14 and each pin 13. Accordingly, the free end portion of the flexible member 7 can be positioned readily and accurately, so that the solder balls 9 on the flexible member 7 are positioned on the wiring pattern of the printed circuit board 5 accurately.

[0036] Next, a procedure for producing the circuit device shown in FIGS. 3 and 4 is explained below. First, as explained in the first embodiment referring to FIGS. 1 and 2, the connector body 1 assembled with the lead terminals 3, the flexible member 7 holding the solder balls 9 arranged into a specific pattern thereon, and the printed circuit board 5 are prepared, respectively. The stays 11 are attached to the connector body 1 at this stage.

[0037] The lead terminals 3 extending from the connector body 1 are inserted into the respective through holes 8 of the flexible member 7, and are fixed to the flexible member 7 by soldering. Next, the free end portion of the flexible member 7 is bent toward the side opposite to the connector body 1, and then, the positioning pins 13 of the stays 11 are inserted into the through holes 14 provided in the free end portion. In this state, the screws 6 are screwed into the screw holes 4aof the leg portions 4 through the holes 5aof the printed circuit board 5 so that the connector body 1 is screwed to the printed circuit board 5. The plural solder balls 9 are positioned on the wiring pattern on the printed circuit board 5 at high accuracy by the screw fixation step. After that, the flexible member 7 and the printed circuit board 5 are soldered together by a soldering reflow treatment, thereby completing the circuit device shown in FIG. 3.

[0038] According to the second embodiment described above, the same effects as those in the first embodiment are realized. For example, the mounting workability is easy, the reliability of soldered portions (BGA portions) is improved, and the number of the lead terminals of the connector can be increased. In addition, according to the second embodiment, the flexible member 7 bent in an arbitrary direction can be positioned on the printed circuit board 5 readily and accurately by changing the direction in which the stays 11 extend. For example, the stays 11 may extend toward the connector body 1 (under the connector body 1) at a side opposite to that in FIGS. 3 and 4.

[0039] While the present invention has been shown and described with reference to the foregoing preferred embodiments, it will be apparent to those skilled in the art that changes in form and detail may be made therein without departing from the scope of the invention as defined in the appended claims.

[0040] For example, in the embodiments described above, two or three leg portions 4 are provided at the bottom wall of the connector body 1. However, the number of the leg portions 4 is not limited to that, but may be one or more than three. The positions where the leg portions 4 are provided are also arbitrary changeable, and can be determined in consideration of the assembling strength of the connector and the like.

[0041] The circuit device shown in FIGS. 3 and 4 can dispense with the leg portions 4 of the connector body 1 when the thickness of the bottom wall of the connector body 1 is increased so that screw holes are formed in the bottom wall directly. In this case, the connector body 1 is screwed to the printed circuit board 5 by inserting the screws into the screw holes. The flexible member 7 is positioned by the stays 11 as well. As a result, the same effects described above can be provided.

[0042] In the embodiments described above, the solder balls 9 are arranged on the flexible member 7 with the latticed shape to adopt the BGA form. However, the solder balls 9 may be arranged with another shape such as a staggered shape, a line, or the like. The solder balls 9 may be disposed on the printed circuit board 5 instead of on the flexible member 7 to undergo the reflow treatment.

[0043] The present invention is especially effective to multi way connectors, but is not limited to those. The present invention is also applicable to circuit devices not adopting the BGA form.