Leadless Chip Carrier Adapter

It is often desirable to monitor signals being transmitted between a LCC (Leadless Chip Carrier) and the circuit of a printed circuit board to which the LCC is connected. The LCC is typically held in a LCC socket which plugs into the circuit board. A simple low-cost LCC socket does not have any exterior terminals for connection to test equipment. It is possible to use a special LCC socket with such externally-accessible terminals, but if it is desired to make a test on an ordinary circuit then it would be necessary to remove the socket already in place and replace it with a special purpose socket. An adapter which permitted the testing of signals passing between an LCC and an ordinary low-cost socket which normally holds the LCC, would aid in the testing of circuits. Such an adapter would be even more useful if it permitted separate testing of the circuit connected to the socket in the absence of the LCC, and separately permitted testing of the LCC when it was not connected to the circuit to which the socket is connected.

In accordance with one embodiment of the present invention, an adapter is provided for making connections between a LCC (Leadless Chip Carrier) and an ordinary low-cost socket designed to hold the LCC, while also providing for connections to outside test equipment to monitor the interface between the LCC and the socket. The adapter can include a base element which is shaped so that it fits into the socket, and which has conductive pads forming the same contact footprint as a LCC. The adapter also includes a test interfacer which includes a frame with a receiver for receiving a LCC, and a multiplicity of leads. Each lead extends between the receiver and the pads of the base element to connect them so that the pads of the LCC are connected to terminals of the socket as though the LCC were directly held by the socket. The leads include externally-accessible test terminal portions to which test equipment can be connected to monitor signals passing between the LCC in the receiver of the interfacer and the terminals of the socket.

The novel features of the invention are set forth with particularly in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.

FIG. 1 is an exploded view of an adapter of the present invention, and also showing a LCC (Leadless Chip Carrier) and a LCC socket with which the adapter is used.

FIG. 2 is a partial sectional view of the adapter of FIG. 1.

FIG. 1 illustrates an adapter 10 which can be used to make connections between a LCC (Leadless Chip Carrier) 12 and a LCC socket 14. The LCC 12 has contact pads 16 at its periphery, that are connected to an integrated circuit chip 18. The LCC is designed for installation directly in the socket 14 by laying the LCC into a recess 20 in a frame 22 of the socket, so that the pads 16 of the LCC engage socket terminals 24. The terminals 24 are connected to a circuit 26 on a printed circuit board 28. The adapter 10 is designed to connect the pads 16 of the LCC to the terminals 24 of the socket so the integrated circuit of the LCC 12 can interact with the circuit 28 on the printed circuit board, and to also provide outward external terminals 30 that are accessible for connection to external test equipment that can monitor the signals passing between the LCC 12 and the socket 14.

The adapter 10 includes a base element 32 that is shaped to fit into the LCC socket 14 in the same manner as the LCC 12. The base element 32 has multiple contact pads 34 mounted on the base element frame 36. The pads 34 have peripheral portions 38 that extend to the periphery of the frame 36, so that when the base element 32 is installed in the socket 14, the peripheral pad portion 38 will make contact with the socket terminals 24. The contact pads 34 of the base element also have inner portions 40 spaced from the periphery of the base element frame, and which are designed to make contact with leads 42 on a test interfacer 44.

The interfacer includes a frame 46 which forms a receiver 48 at its upper end which receives the LCC 12. The leads 42 extend from the lower end 46b of the frame to the upper end 46u, where the upper ends of the leads have inner portions 50 that can engage the contact pads 16 of the LCC when the LCC is in the receiver 48. The upper ends of the leads have outer portions formed by the terminals 30 in the form of upstanding pins, that enable connection to external test equipment. When the system is assembled, with the base element 32 installed in the socket 14, the interfacer 44 installed on the base element 32, and the LCC 12 installed in the interfacer, power and signals can pass between the circuit 26 on the circuit board and the LCC 12, so that the entire circuit can operate in a normal fashion. However, test equipment connected to the terminals 30 will be connected to the interface between the LCC and the socket 14, and can monitor the signals transmitted between them.

FIG. 2 illustrates some of the details of the adapter 10. Each lead 42 includes an insulated contact lead or conductor 54 which extends along most of the height of the interfacer and is surrounded by an insulator 55. A contact element 56 connects to the top of the conductor. The contact element forms the inner portion 50 of the top of the lead and the outer portion or terminal 30 of the top of the lead. The bottom of the conductor forms a bottom contact 57 that can contact the conductive layer 63 of a base element pad 65. The interfacer frame 46 can be formed as a shell with four flat sides that have multiple holes 60. The conductor can have an extreme end inserted in one of the holes 60 that form lead retainers and can be wrapped around a resilient pad 71 of elastomeric material at the bottom of a frame side 62. The elastomeric material absorbs any dimensional differences to assure contact of all bottom contacts. The contact pads 34 on the base element can be formed by upper and lower conductive layers at 63 and 38, that are joined by a plated through hole 64. The bottom contact 57 of a lead can press on at least the conductive layer 63 to contact the plated through holes 64. Such contact can be maintained by a screw 66 on the interfacer that threads into a nut 68 on the base element, and that extends along the axis 69 of each part of the system. The insulated conductors 54 can be formed as portions of a flexible printed circuit, with the spacings of the conductive wires therein selected for use on the interfacer.

The equipment of FIG. 1 can be assembled for use by first inserting the base element 32 into the LCC socket 14 so that the contact pads 34 of the base element contact the terminals 24 of the socket. A lid 70 of the socket assembly can be installed over the base element to hold it in place. The lid 70 lies over only the periphery of the base element, to leave a wide central region of the base element that is uncovered. The test interfacer 44 is installed on the base element 32 by screwing the screw 66 into the nut 68 on the base element to hold them together and with the leads 42 engaged with the contact pads 34. The LCC 12 can then be installed in the interfacer 44. Monitoring or test instrument 72 (FIG. 2) can then be connected to the upstanding pins or terminals 30 to monitor signals transmitted between the LCC 12 and the terminals of the socket 14.

The adapter 10 also permits monitoring of signals passing through the socket terminals 24 in the absence of their connection to the LCC 12. This is accomplished merely by not installing the LCC 12 in the interfacer. Additionally, the interfacer permits testing of the LCC by equipment connected to the pins 30 when the LCC is not connected to the circuit on the printed circuit board. This is accomplished simply by not connecting the interfacer 44 to the base element or not installing the base element in the LCC socket.

Thus, the invention provides an adapter that enables the making of a connection between a LCC (Leadless Chip Carrier) and the terminals of a socket which connects to the circuit on a printed circuit board or the like, while permitting the monitoring of signals passing through the interface between the LCC and the circuit, by external test instruments. This can be accomplished using a relatively low cost LCC socket that is installed on a printed circuit board, rather than requiring a specialized socket. This is accomplished by the use of an adapter which has a base element that can fit into the receiver area of a LCC socket, of a type which has a hold-down lid that leaves a large central uncovered area.

The base element has contact pads forming the same contact footprints as the LCC which it temporarily replaces. An interfacer whose upper end can receive a LCC, has a lower end which can attach to the base element and has leads which extend between the contact pads of the base element and the contact pads of the LCC. The leads also include outer portions that are accessible from outside the interfacer for convenient connection of external test equipment to the LCC and the contacts of the LCC socket.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.