Chip Carrier for Fastening a Chip to a Printed Circuit Board

The present invention relates to chip carriers, and more particularly the present invention relates to a chip carrier which has terminal calibrating ribs to keep the terminals at the same elevation for accurate and positive fastening to a printed circuit board.

An electronic chip is a precision integrated circuit comprised of resistors, diodes, etc., which may be damaged easily when directly welded to a printed circuit board. Therefore a chip carrier is commonly used to fasten a chip to a printed circuit board. There are two different types of chip carriers which are classified according to their mounting methods, namely, the welding process and the surface mounting technology. The present invention pertains to the surface mounting technology type of chip carriers.

A chip carrier according to the prior art, as shown in FIG. 1, is generally comprised of a base, and terminals. The base is made of plastic by an injection molding process, in the shape of a flat square block, having a series of terminal slots along the four sides thereof, which receive the terminals, and a recessed portion in the middle, which receives the chip. A number of terminals are connected by a connecting strip for quick insertion into the terminal slots on the base at the same side. Each terminal is comprised of a mounting contact and a connecting leg. The mounting contact is inserted in either terminal slot while the respective connecting leg projects out of the respective terminal slot for connecting to the printed circuit board. When inserted, the connecting strip is cut off. After the chip has been mounted on the base, the contacts of the chip are respectively disposed in contact with the mounting contacts of the terminals, and the connecting legs of the terminals are respectively connected to the circuit of the printed circuit board by employing a surface mounting technology. Because the connecting legs of the terminals are suspended out of the terminal slots respectively, they are not in perfect alignment (see FIG. 2) and should be corrected to be maintained at the same elevation so that the tin solder can be evenly distributed over the connecting legs while fastening the terminals to the printed circuit board. However, calibrating the horizontal alignment of the connecting legs is not easy, and requires special techniques and tools. While using a tool to correct the connecting legs of the terminals, the connecting legs may be easily damaged or broken.

The present invention eliminates the aforesaid problems. It is therefore the main object of the present invention to provide a chip carrier which automatically keeps the connecting legs of the terminals in perfect horizontal alignment without damaging the terminals. This object is achieved by forming horizontal straight ribs on the base of the chip carrier along the terminal slots thereof at an inner side. When the terminals are respectively inserted in the terminal slots, the connecting legs of the terminals become respectively supported on the horizontal straight ribs at the same elevation.

FIG. 1 is a perspective exploded view of a chip carrier constructed according to the prior art;

FIG. 2 is a front view of the chip carrier of FIG. 1 showing the connecting legs of the terminals not in alignment;

FIG. 3 is a perspective exploded view of a chip carrier constructed according to the present invention;

FIG. 4 is a top view of the chip carrier of FIG. 3 when the terminals are removed; and

FIG. 5 is a cross section taken along line 5--5 of FIG. 4, showing the connecting legs of the terminals in perfect alignment.

Referring to FIGS. 3 and 4, a chip carrier 20 constructed in accordance with the preferred embodiment of the present invention is generally comprised of a base 1, and terminals 2. The base 1 is made of plastic by an injection molding process, in the shape of a flat square block, having series of terminal slots 11 along the four sides thereof, into which a mounting contact 21 oil either terminal 2 is inserted, and a recessed portion 12 in the middle, which receives the chip. A number of terminals 2 are connected by a connecting strip 22 for quick insertion into the terminal slots 11 on the base 1 at the same side. Each terminal 2 consists of the mounting contact 21 and a connecting leg 23. The mounting contact 21 is inserted in either terminal slot 11 while the respective connecting leg 23 projects out of the respective terminal slot 11 for connecting to the printed circuit board. After the chip has been mounted on the base 1, the contacts of the chip are respectively disposed in contact with the mounting contacts 21 of the terminals 2, and the connecting leg 23 of the terminals 2 are respectively connected to the circuit of the printed circuit board by employing a surface mounting technology.

Referring to FIG. 5 and FIGS. 3 and 4 again, the main feature of the present invention is outlined hereinafter with reference to FIGS. 3 and 4 again. There are four straight ribs 13 integrally formed on the base 1 and horizontally disposed along the terminal slots 11 at an inner side adjacent to a recessed portion, which serve as automatic calibration lines to keep respective connecting legs 23 at the same elevation (see FIG. 5). Therefore, the chip carrier 20 is maintained perfectly horizontal when mounted on the printed circuit board, permitting the tin solder to be evenly distributed over every connecting leg 23 without causing any error. Each straight rib 13 comprises a series of grooves 14 spaced corresponding to the terminal slots 11 on either side. The depth of the grooves 14 is relatively shorter than the diameter of the connecting legs 23, for example: the depth of the grooves 14 is about 0.15 m/m, and the connecting legs 23 have a 0.2 m/m diameter. When a connecting leg 23 is inserted into the respective groove 14 on the respective straight rib 13, its outer wall will project out of the respective groove 14 for fastening to the printed circuit board by employing a surface mounting technology. The width of the grooves 14 is slightly greater than the diameter of the connecting legs 23 so that the connecting legs 23 can be conveniently inserted into the respective grooves 14. The arrangement of the grooves 14 on the straight ribs 13 are intended to receive the connecting legs 23, and to keep them straight.

As indicated, tile present invention provides a chip carrier having terminal calibrating ribs to keep terminals in perfect alignment automatically for easy and accurate application of the tin solder without damaging the terminals.

While only an embodiment of the present invention has been shown and described, it will be understood that various modifications and changes could be made without departing from the spirit and scope of the invention.