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OEM-friendly thermal test chip design for flip-chip application

IP.com Disclosure Number: IPCOM000004730D
Publication Date: 2001-Apr-23
Document File: 5 page(s) / 237K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a design for an OEM-friendly thermal test chip for flip-chip application. Benefits include improved uniformity of die heating and similarity of electrical current as the final product without requiring a special test board, external power supply or a test-vehicle-specific package substrate.

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OEM-friendly thermal test chip design for flip-chip application

Disclosed is a design for an OEM-friendly thermal test chip for flip-chip application. Benefits include improved uniformity of die heating and similarity of electrical current as the final product without requiring a special test board, external power supply or a test-vehicle-specific package substrate.

The thermal test vehicle of the test chip is pin compatible with the production motherboard through the Vcc and Vss pins. The electrical current level through the package substrate, socket, and pins for the actual product can also be simulated by this test chip design.

The key element of the design is a thermal test chip with small cells of Vcc-Vss die bump pattern. A specific heater design is duplicated in each Vcc-Vss cell and populated for almost the entire flip-chip die area. These small heater bands in each cell can then be powered up through the Vcc/Vss die bumps and package pins.

Thermal testing has conventionally posed several problems. Heat generation on the thermal test die is not uniform due to the serpentine-type of heater design. The electrical current level through the package substrate, pins, and sockets does not simulate the actual product current level during the thermal test. The conventional thermal test vehicle is not pin-compatible to the production motherboard and socket. To power up the thermal test vehicle, OEMs must design a special test board.

Conventional solutions have addressed these problems in two ways. One solution is to reduce the spacing between heater traces to improve the uniformity of die heating. However, non-uniform heating has persisted, as shown as Figure 1.

Another conventional solution is to connect the heater on the test die to the package substrate by including Vcc and Vss die bumps on each end of the heater replacing the I/O bumps as shown in Figure 2. This solution enables the heater to be easily powered up by the Vcc and Vss pins from the production motherboard and socket. This solution results in several problems. To accommodate the limitation of 5-10 Vcc and Vss die bumps, the heater resistance of the conventional thermal test vehicle must be about 30 ohms so that the test die can be powered to 30 watts without damaging the die bumps. As a result, the total current level during thermal test is only about 1 amp where as the actual product level is up to 20 amps. The electrical-current level through the package substrate, pins, and socket in the actual product is not simulated by the conventional thermal test vehicle.

Another problem with the conventional solution involves the power supply. The chassis power supply for the production motherboard produces -1.5 volts and 20+ amps. This voltage and current is different from the 30 volts and 1 amp required for the thermal test vehicle. Furthermore, connecting an external DC power supply to the motherboard presents a very high risk to the other components mounted on the same motherboard.

The disclose...