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Method for a load-controlled RTD probe design for high heat flux surface temperature measurements

IP.com Disclosure Number: IPCOM000011736D
Publication Date: 2003-Mar-12
Document File: 4 page(s) / 70K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a load-controlled resistive temperature device (RTD) probe design for high heat flux surface temperature measurements. Benefits include improved performance.

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Method for a load-controlled RTD probe design for high heat flux surface temperature measurements

Disclosed is a method for a load-controlled resistive temperature device (RTD) probe design for high heat flux surface temperature measurements. Benefits include improved performance.

Background

� � � � � Processor package thermal performance is conventionally assessed using the metric Rjc, which is the thermal resistance between the die and the integrated heat spreader (IHS). This metric is expressed in equation 1 (see Figure 1). The equation contains the following values:

•        � � � � Tj is the maximum temperature of the die.

•        � � � � Tc is the temperature of the integrated heat spreader.

•        � � � � P is the power input to the die.

•        � � � � Adie is the cross-sectional area of the die through which the heat is transferred.

� � � � � A metrology is deemed capable of measuring a parameter if the precision to tolerance (P/T) ratio is less than 30%. The P/T ratio is defined in equation 2 (see Figure 2). The equation contains the following values:

•        � � � � sms is the measurement system variation in measuring Rjc.

•        � � � � USL is upper spec limit

•        � � � � xbar is the process mean

� � � � � Rjc is a function of Tj, Tc, and power as shown in equation 1. Therefore, reducing the variation in any of the three input parameters Tj, Tc, or power reduces the variation in Rjc. The disclosed method reduces the variation of the parameter Tc.

� � � � � Conventionally, a K-type thermocouple measures the IHS temperature (Tc). The thermocouple is epoxied in a groove that is machined in the base of the heatsink and is oriented parallel to the IHS. The thermocouple bead is bent 90 degrees and protrudes 0.005 inch to 0.010 inch from the surface of the heatsink. The bead contacts the IHS when the heatsink is attached to the package. An accurate heat spreader temperature is attained if the thermocouple bead contacts the heat spreader. The thermocouple bead wears from repeated use. As the contact with the IHS becomes worse, the accuracy and precision of the measurement is affected. As the input power and the heat flux increases, the thermocouple contact with the IHS becomes more critical because larger temperature gradients exist through the die, heat spreader, and thermocouple bead.

General description

� � � � � The disclosed method is a load-controlled RTD probe design for high heat flux surface temperature measurements. A thin-film RTD is deposited on the tip of a copper cylinder to measure the surface temperature (Tcase) of an IHS. Four RTD connections occur along the length of the copper cylinder and protrude out the top of the heatsink or cold plate. The connections are subsequently connected to the digital multi-meter (DMM) for a four-wire resistance measurement. The copper cylinder is pressed against the IHS using a load fixture that enables the pressure to be applied consistently to minimize and control contact resistance between the surface and tem...