1. Technical Field
This invention relates in general to multi-chip modules and, more specifically, to methods for repairing such modules by bonding out a module repair site using a repair solution generated during module testing.
2. State of the Art
As shown in FIG. 1, multi-chip modules (MCMs), comprising multiple dice carried on a printed circuit board (PCB) or other carrier substrate bearing circuit traces, are generally tested after being assembled, and those MCMs that pass testing are then shipped to customers. Those MCMs that fail testing are marked as such, typically by printing an xe2x80x9cXxe2x80x9d on the top of the xe2x80x9cbadxe2x80x9d (i.e., at least partially defective) dice that caused each MCM to fail testing. After being marked, any bad dice on a given MCM are disabled through various means including, for example, cutting conductive traces on the MCM to isolate the bad dice, or shorting conductive traces together to force a high-impedance condition on all inputs and outputs of the bad dice (e.g., by pulling the RAS* input of a Dynamic Random Access Memory (DRAM) permanently high).
Once the bad dice are disabled, known-good die (KGD) repair dice are attached to each failing MCM at an empty repair site. The failing MCMs with attached repair dice then proceed to a wire-bonding station, where an operator manually selects the wire-bonding pattern (also referred to as a wire-bonding xe2x80x9csolutionxe2x80x9d herein) necessary to connect the repair dice to traces on the carrier substrate to replace the disabled bad dice. The repair dice are wire-bonded using the manually selected wire-bonding solution, and the repaired MCMs are then retested, with those repaired MCMs that pass the retesting proceeding on to shipping, and those repaired MCMs that fail retesting proceeding once again to repair or, alternatively, to scrap.
Because a wire-bonding machine operator manually selects a particular wire-bonding pattern for each MCM to be repaired, the process of repairing MCMs is subject to human error. Specifically, the operator generally selects the particular wire-bonding pattern to be used based on which dice are marked as bad (e.g., with the xe2x80x9cXxe2x80x9d described above), so the operator may make a mistake in observing which dice are marked as bad, or in selecting the appropriate wire-bonding pattern, or both.
Therefore, there is a need in the art for a method of selecting a wire-bonding solution for an MCM to be repaired that avoids the chance for human error associated with the conventional method described above.
In one embodiment of this invention, a multi-chip module (MCM) proceeds to testing after it is assembled. During testing, an ID code (e.g., a bar code) of the MCM is read. Then, if the MCM fails testing, a wire-bonding repair solution is generated and stored in a computer system in association with the ID code. The wire-bonding repair solution may identify, for example, which of several sets of bonding pads on the surface of a substrate of the MCM a repair integrated circuit (IC) die or dice should be wire-bonded to. A bad IC die or dice of the MCM that caused the MCM to fail testing may then be disabled by, for example, disconnecting the bad IC die or dice from the rest of the MCM, or by permanently connecting the bad IC die or dice so all of its inputs and outputs are in a high-impedance state. The repair IC die or dice is then attached to the substrate of the MCM, the stored repair solution is accessed, and the repair IC die or dice is wire-bonded to the substrate in accordance with the accessed repair solution. As a result, the opportunity for human error is avoided, and the length of time it takes to repair the MCM is shortened.