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Design for a self-contained, encapsulated, field-replaceable, spring loaded resistive thermal device for temperature sensing in a thermal control unit for central processor unit test systems

IP.com Disclosure Number: IPCOM000006568D
Publication Date: 2002-Jan-15
Document File: 9 page(s) / 272K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a design for a self-contained, encapsulated, field-replaceable, spring loaded resistive thermal device (RTD) for temperature sensing in a thermal control unit (TCU) for central processor unit (CPU) test systems. Benefits include improved durability, improved performance, and ease of replacement/installation.

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Design for a self-contained, encapsulated, field-replaceable, spring loaded resistive thermal device for temperature sensing in a thermal control unit for central processor unit test systems

Disclosed is a design for a self-contained, encapsulated, field-replaceable, spring loaded resistive thermal device (RTD) for temperature sensing in a thermal control unit (TCU) for central processor unit (CPU) test systems. Benefits include improved durability, improved performance, and ease of replacement/installation.

Components

                    The disclosed design is comprised of the following components:

·        Spring-loaded RTD – provides temperature feedback from the CPU

·        RTD element – a resistive temperature-sensing device consisting of a platinum resistor housed in a ceramic package.

·        RTD cup – a machined copper cup houses and protects the RTD and directly interfaces with the object of which the surface temperature is monitored (for example, the CPU package)

·        Spring – enables compliance in the design and provides a force that presses the RTD cup contact surface against the CPU package to aid in thermal conduction between the two surfaces.

·        Cover – a press-fit top piece secures the spring and holds the components in place.

·        Wiring – braided strand wires are secured to the RTD element and extend out of the housing to a connector to allow the resistance of the RTD to be monitored with a data acquisition system.

·        Housing – all components are held together within the cylindrical outer housing. The wiring harness extends out of the housing on one side, and the contact surface of the RTD cup extends out of the other.

Theory of Operation

                    During CPU production testing, the TCU controls the CPU temperature because power to the CPU varies due to operating conditions. The assembled TCU is mounted to an air actuator and pressed against the CPU during the test operation. The RTD touches the surface of the CPU and feeds back the CPU temperature to an external temperature controller that is designed to enable the TCU to maintain a prespecified temperature setpoint on the surface of the CPU. If the actual CPU temperature and the setpoint are not in agreement, the temperature controller generates a control signal that causes the TCU to either heat or cool the CPU via thermoelectric coolers.

 


Description

                    The RTD provides feedback for the CPU temperature to an external controller so that CPU temperature can be accurately maintained. To ensure good contact with the CPU, a spring is mounted behind the RTD to press it tightly against the CPU surface. This force helps to improve the thermal conductivity between the RTD and the CPU. The spring also enables the RTD element to conform to the CPU package, which may be a curved surface. Mounting the RTD in an enclosure with a spring behind also helps to isolate the RTD thermally from the control plate so that the RTD is measuring the temperature of the CPU and not the control plate.

                    Conventionally, the RTD is mounted so that it protrudes be...