Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-03-18
2001-02-27
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S801000, C439S062000, C439S949000, C029S856000
Reexamination Certificate
active
06195263
ABSTRACT:
The entire disclosure of Japanese Patent Application No. Hei 10-92336 filed on Mar. 20, 1998 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an electronic control unit and more particularly, to the structure of a pad portion for connecting a connector and a circuit substrate of the electronic control unit by wire bonding.
2. Description of the Related Art
Hitherto, a circuit substrate constituting an electronic control unit is generally contained in a resin case (b) which is formed integrally with a connector (a) as shown in
FIG. 8
, and the circuit substrate (c) is electrically coupled to the connector (a) through a number of strip-like terminal plates (e) which have been molded integrally with the resin case (b) by die molding. Each of the terminal plates (e) has one end formed as a pin projecting into the connector (a) and the other end formed as a lead portion (f) having a face exposed at the pad portion (d) which is formed in the case (b). The lead portions (f) which are arrayed close together on a common plane in the pad portion (d) are designed to terminate at the front face of the pad portion (d).
The terminals at the side of the circuit substrate (c) are respectively connected to the lead portions (f) at the side of the terminal plate (e) by wire bonding which has been increasingly employed because of easy processing. Wire bonding is a method for bonding metals by compressing and vibrating an end of the bonding wire (g) formed of aluminum or the like to the lead portion (f) of the terminal plate e), with a bonding tool and using high frequency vibration, so as to remove soil or oxide film from the press fit portion.
Referring to
FIG. 9
, the lead portion (f) of the terminal plate (e) is fixed within the resin molding (case b) with its upper surface exposed to allow bonding to the wire (g) and has a thin embedded thickness. Therefore it is difficult to provide sufficient strength in the bond between the case (b) and the pad portion (d). More importantly, because the tip of the lead portion (f) terminates at the front face of the pad portion (d), in a so-called open state, sufficient force to arrest the movement of the terminal plate (e) cannot be obtained.
As described above, in the related art, the terminal plate (e) is held in place merely at a short portion of its length where it passes through the wall of the case (b). Accordingly, if the wire (g) is pressed against the lead portion (f) in the pad portion (d), using the bonding tool to apply vibration for effecting the wire bonding, the lead portion (f) which is insufficiently fixed is also vibrated together with the wire g), thus inhibiting formation of a good bond between the wire (g) and the lead portion (f).
SUMMARY OF THE INVENTION
Accordingly, it is a first object of the invention to provide a bond between a circuit substrate and a connector in an electronic control unit which is sufficiently strong to withstand the supersonic vibration applied in wire bonding.
Further, even if sufficient bonding strength is provided to satisfy the foregoing objective, because the wire (g) is pulled upward by the bonding tool upon completion of the bonding, the lead portion (f) of the terminal plate (e) is likely to separate from the pad portion (d), resulting in displacement. Therefore, it is a second object of the present invention to prevent the lead portion (f) from separating from the pad portion (d).
Further, in manufacture of such a connector having a large number of closely arrayed terminal plates (e) arrayed directly on the case (b), it is necessary to spread the resin completely to reach even fine gaps. For this purpose, the resin is required to be compressed at a high pressure, and it becomes difficult to prevent the displacement of the terminal plates (e) when molding under high pressure. Therefore, a two-stage manufacture must be used to avoid the problem. The two-stage manufacture includes a first stage wherein only the portion in the area of the terminal plate (e) is molded (primary molded part) to a degree allowing relative positioning, and a second stage wherein the primary molded part is further molded to the case for completing the whole case. However, in practice of the two-stage molding process, a fine gap between the primary molded part and the secondary molded part is formed owing to thermal shrinkage after completion. Especially, slip may occur at the boundary between the secondary molded part and back surface of the pad portion with a gap forming between one end side of the pad portion and the secondary molded part, resulting in the possibility of buffering the supersonic vibration used in wire bonding. Such buffering of the vibration may cause deterioration of the bonding strength between the lead in the pad portion and the wire.
Accordingly, it is a third object of the present invention to prevent buffering of the supersonic vibration used in wire bonding.
In order to attain the first object, the present invention provides an electronic control unit including a circuit substrate, a case accommodating the circuit substrate, a connector provided on the case, and a number of terminal plates extending into the case from the pins of the connector to be connected to the circuit substrate. The case is provided with a pad portion for securing therein lead portions of the terminal plates. A surface of each of the lead portions is exposed in the pad portion and is connected at this exposed surface to a terminal on the circuit substrate through a bonding wire.
To better attain the aforementioned second object, each lead portion is bent at the opposing ends of the exposed surface portion for embedding in the case.
In order to attain the aforementioned third object, the case is formed of a primary molded part formed by integrally molding the connector and the pad portion and a secondary molded part. More specifically, a resistance or “anchor” portion in mesh with the secondary molded part is formed on the back surface of a pad portion of the primary molded part.
According to one preferred embodiment of the invention, each lead portion has first bent portions extending in opposite directions from its surface section which is exposed in the pad portion, which bent portions are embedded in the case whereby the lead portion of the terminal plate is completely fixed to the case at the pad portion. Moreover, as the bent portions serve to prevent the wire and lead portion from vibrating together during wire bonding, strong bonding therebetween can be attained.
Furthermore, the lead portion may be more firmly fixed to the pad portion through second bent portions formed by further bending the aforementioned first bent portions. In this manner the lead portion can be more firmly fixed to the pad portion of the case, not only in the axially extending direction thereof but also in a direction perpendicular thereto. As a result, the lead portion cannot separate from the pad portion when lifting away the bonding tool.
Furthermore, because an anchor portion is meshed with the secondary molded part and is provided on the back surface of the pad portion of the primary molded part, it prevents release of the vibration at the open end side of the pad portion, thus ensuring good strength in the bond between the leads embedded in the pad portion and the wires during wire bonding.
REFERENCES:
patent: 5185550 (1993-02-01), Morita et al.
patent: 5646445 (1997-07-01), Masumoto et al.
patent: 2-146839 (1990-12-01), None
patent: 5-053149 (1993-07-01), None
patent: 6-104362 (1994-04-01), None
patent: 7-010947 (1995-02-01), None
patent: 10-270134 (1998-10-01), None
Aoike Koji
Murakami Naotaka
Takata Hiroki
Yamato Osamu
Aisin Aw Co. Ltd.
Gandhi Jayprakash N.
Lorusso & Loud
LandOfFree
Electronic control unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electronic control unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electronic control unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2599967