Semiconductor components, such as bare dice and chip scale packages, must be tested prior to shipment by semiconductor manufacturers. Since these components are relatively small and fragile, carriers have been developed for temporarily packaging the components for testing. The carriers permit electrical connections to be made between external contacts on the components, and testing equipment such as burn-in boards. On bare dice, the external contacts typically comprise planar or bumped bond pads. On chip scale packages, the external contacts typically comprise solder balls in a dense array, such as a ball grid array, or a fine ball grid array.
An interconnect component of the carrier includes contacts that make the temporary electrical connections with the external contacts on the components. The interconnect provides power, ground and signal paths to the component. A force applying mechanism of the carrier applies a biasing force for biasing the component against the interconnect. Typically, the force applying mechanism includes a biasing member such as a metal, or elastomeric spring for applying the biasing force. In addition, the force applying mechanism can include a clamp, or a latch plate, for securing the biasing member to a base of the carrier.
One aspect of this type of carrier is that the biasing force is determined by the geometry and construction of the force applying mechanism. This biasing force is fixed when the carrier is assembled, and the biasing member presses the component against the interconnect. However, it would be advantageous to be able to adjust this biasing force during and subsequent to assembly of the carrier.
For example, a relatively large biasing force is required during initial contact of the component with the interconnect. The large biasing force is required for making reliable temporary electrical connections with the contacts on the component. Solder balls, for example, can be retained in a conductive pocket, or penetrated with conductive projections. The large biasing force is necessary for penetrating native oxide layers present to make low resistance electrical connections. However, once the electrical connections are made with the component contacts, the biasing force does not need to be as large. Also, if the carrier and component are heated during testing, such as in a burn-in oven, the contacts expand, and lower biasing forces are sufficient to maintain the electrical connections.
The present invention is directed to a carrier that includes a biasing member constructed to provide a variable biasing force. In particular, the biasing force can be large during initial assembly of the carrier, and smaller following assembly and during operation of the carrier.